JP2017120879A - Protection element, manufacturing method of protection element, mounting substrate, and electronic device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a protection element which is small in space occupation ratio and high in degree of layout freedom; a protection element manufacturing method which enables the efficient manufacturing of such a protection element; a mounting substrate including the protection element, and arranged so as to be able to protect an electronic component mounted thereon against an overvoltage; and a compact and reliable electronic device.SOLUTION: A mounting substrate 1 comprises: a pair of wiring lines 31 and 32 (conductive parts) spaced apart from each other on the surface of an insulative substrate 2 (base); a protected circuit (electronic component) electrically connected with the pair of wiring lines 31 and 32; and a protection element 5 provided athwart the pair of wiring lines 31 and 32. Of these constituents, the protection element 5 has: semiconductor ceramics particles 51 including grain boundary portions and a plurality of crystalline portions separated from each other by the grain boundary portions; and a cured product 52 of a resin of which the relative dielectric constant is 4 or less. The semiconductor ceramics particles 51 are unevenly distributed and concentrated on the side of the insulative substrate 2.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a protective element, a method for manufacturing the protective element, a mounting substrate, and an electronic device.

  In recent years, electronic devices have been rapidly reduced in size and thickness, and accordingly, the density of electronic components mounted on the wiring board and the density of wiring laid on the wiring board have also increased.

  When such high density progresses, when an overvoltage caused by static electricity is superimposed on the circuit, the electronic components are easily broken or malfunctioned. This is especially true when there is an increased opportunity for electronic devices to be exposed to static electricity when they are used in contact with a human body, such as mobile devices, or when electronic devices are connected with cables. The probability of occurrence is high.

  Therefore, varistors using semiconductor ceramics have been proposed to protect the circuit from overvoltage. For example, Patent Document 1 discloses that a semiconductor integrated circuit chip built in an IC card is prevented from electrostatic breakdown by incorporating a multilayer chip varistor.

JP 2001-160125 A

  However, further demands for downsizing and thinning of electronic devices are taking away even room for arranging small multilayer chip varistors. For this reason, there is an urgent need to develop a protective element with a very small space occupancy while protecting a circuit from an overvoltage caused by electrostatic discharge. In addition, a high degree of freedom that can be arranged in a small excess space is one of the requirements for the protection element.

  An object of the present invention is to provide a protective element having a small space occupancy ratio and a high degree of freedom in arrangement, a method for manufacturing a protective element capable of efficiently manufacturing such a protective element, and protecting an electronic component equipped with the protective element from overvoltage. An object of the present invention is to provide a mounting board and a small and highly reliable electronic device.

Such an object is achieved by the present inventions (1) to (11) below.
(1) A protective element that is provided across the conductive parts that are spaced apart from each other on the surface of the base, and that exhibits non-linearity in which the voltage-current characteristics do not follow Ohm's law,
A semiconductor ceramic particle including a grain boundary part and a plurality of crystal parts separated by the grain boundary part, and a cured product of a resin having a relative dielectric constant of 4 or less,
A protective element, wherein the semiconductor ceramic particles are unevenly distributed on the base side.

(2) A protective element that is provided across the conductive parts that are spaced apart from each other on the surface of the base, and exhibits non-linearity in which the voltage-current characteristics do not follow Ohm's law,
Semiconductor ceramic particles including a grain boundary part and a plurality of crystal parts separated by the grain boundary part, and a cured product of a curable resin,
A protective element, wherein the semiconductor ceramic particles are unevenly distributed on the base side.

  (3) Among the protective elements, when the volume fraction of the semiconductor ceramic particles on the base side is 1, the volume fraction of the semiconductor ceramic particles on the side opposite to the base is 0 or more and 0.90 or less. The protective element according to (1) or (2) above.

  (4) The protective element according to any one of (1) to (3), wherein the resin includes an epoxy resin, a silicone resin, an olefin resin, or a benzocyclobutene resin.

  (5) The protective element according to any one of (1) to (4), wherein the surface of the protective element includes a curved convex surface at least partially.

(6) applying a composition comprising semiconductor ceramic particles including a grain boundary part and a plurality of crystal parts separated by the grain boundary part, and an uncured curable resin;
Curing the curable resin in the composition to form a protective element exhibiting non-linearity in which voltage-current characteristics do not follow Ohm's law;
The manufacturing method of the protection element characterized by having.

(7) provided before the step of applying the composition, a base, a plurality of conductive parts provided on the surface of the base and spaced apart from each other, and an electronic component electrically connected to the conductive part The method further comprises the step of preparing an insulating member in which is disposed,
The method for manufacturing a protective element according to (6), wherein in the step of applying the composition, the composition is applied to a region straddling the conductive portions.

  (8) The method for manufacturing a protective element according to (7), wherein the composition is applied by discharging the composition toward the region.

(9) the base,
A plurality of conductive portions provided on the surface of the base and spaced apart from each other;
An electronic component electrically connected to the conductive portion;
The semiconductor ceramic particles, which are provided across the conductive parts and include a grain boundary part and a plurality of crystal parts separated by the grain boundary part, and a cured product of a curable resin, have a voltage-current characteristic. A protective element exhibiting non-linearity that does not follow Ohm's law;
Have
In the protective element, the semiconductor ceramic particles are unevenly distributed on the base side.

(10) Further, a solder resist film is provided so as to cover a part on the surface of the conductive portion, and has an opening corresponding to a region including a gap between the conductive portions,
The mounting substrate according to (9), wherein the protection element is provided so as to protrude from the opening onto the surface of the solder resist film.

  (11) An electronic device comprising the protective element according to any one of (1) to (5) above.

According to the present invention, a protection element having a small space occupancy and a high degree of freedom in arrangement can be obtained.
Moreover, according to this invention, the said protection element can be manufactured efficiently.

In addition, according to the present invention, it is possible to obtain a mounting substrate that can protect an electronic component equipped with the protection element from overvoltage.
In addition, according to the present invention, a small and highly reliable electronic device can be obtained.

It is a circuit diagram which shows an example of the electric circuit with which 1st Embodiment of the mounting board | substrate of this invention is provided. It is a perspective view which expands and shows the electric wiring vicinity which comprises the electric circuit shown in FIG. It is a top view which shows the other structural example of the electrical wiring which comprises the electrical circuit shown in FIG. It is the sectional view on the AA line of FIG. It is the elements on larger scale of the semiconductor ceramic particle shown in FIG. It is a figure for demonstrating the method to measure the dielectric constant of resin. It is a fragmentary sectional view of 2nd Embodiment of the mounting board | substrate of this invention. It is sectional drawing for demonstrating embodiment of the manufacturing method of the protection element of this invention. It is sectional drawing for demonstrating embodiment of the manufacturing method of the protection element of this invention. It is a figure for demonstrating the method of calculating a non-linear coefficient and a varistor voltage from the measurement result of an electric current value.

  Hereinafter, a protection element, a manufacturing method of a protection element, a mounting substrate, and an electronic device according to the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

<Mounting board>
<< First Embodiment >>
First, a first embodiment of a mounting board of the present invention and a first embodiment of a protection element of the present invention included therein will be described.

  FIG. 1 is a circuit diagram showing an example of an electric circuit provided in the first embodiment of the mounting board of the present invention. FIG. 2 is an enlarged perspective view showing the vicinity of the electric wiring constituting the electric circuit shown in FIG.

The mounting substrate 1 shown in FIG. 1 includes an insulating substrate 2 (base portion), two wirings 31 and 32 (conductive portions) that are provided on the surface of the insulating substrate 2 and are spaced apart from each other, and the wirings 31 and 32 are electrically connected. The protected circuit 4 (electronic component) connected to each other and the protection element 5 provided across the wiring 31 and the wiring 32 are provided. The wirings 31 and 32, the protected circuit 4 and the protection element 5 constitute an electric circuit. Further, the power supply 6 is electrically connected to the wiring 31 and the wiring 32 on the mounting substrate 1 so that a voltage can be applied between them.
Hereinafter, the configuration of each unit will be described in detail.

The insulating substrate 2 is a substrate that supports the wirings 31 and 32, the protected circuit 4, the protective element 5, and the like.
The constituent material of the insulating substrate 2 is not particularly limited as long as it is an insulating material. For example, polyimide resin, polyamide resin, epoxy resin, various vinyl resins, polyethersulfone resin, cycloolefin resin Various resin materials (resin material for flexible printed wiring boards) such as resin, polycarbonate resin, polyester resin such as polyethylene terephthalate resin and polyethylene naphthalate are listed.

  In addition, as a constituent material of the insulating substrate 2, for example, paper, glass cloth, resin film or the like is used as a base material, and this base material includes a phenol resin, a polyester resin, an epoxy resin, a cyanate resin, and a polyimide resin. Insulating substrates used for composite copper-clad laminates such as glass cloth / epoxy copper-clad laminates, glass nonwoven fabrics / epoxy copper-clad laminates, etc. In addition, heat-resistant and thermoplastic organic rigid substrates such as polyetherimide resin substrates, polyetherketone resin substrates, polysulfone resin substrates, and ceramic rigid substrates such as alumina substrates, aluminum nitride substrates, silicon carbide substrates, etc. Can be mentioned.

The wirings 31 and 32 are composed of a conductive layer provided on the surface of the insulating substrate 2.
Examples of the constituent material of the wirings 31 and 32 include metal materials such as copper, aluminum, nickel, chromium, zinc, tin, gold, silver, and the like, or alloys containing these metal elements.

  The wirings 31 and 32 may be formed by, for example, a method of attaching a metal foil, a method of baking a metal paste, a method of forming a film by a vapor deposition method, a method of forming a film by an electrolytic or electroless plating method, or the like. Is mentioned. Moreover, it can form also by the method of patterning the metal layer formed by such a method.

  Note that the form of the wirings 31 and 32 shown in FIG. 1 is an example, and another wiring may be provided or may be branched in the middle.

Further, the line impedance Z ₀ shown in FIG. 1 is a resistance element corresponding to the internal resistance of the power source 6 and the line impedance of the mounting substrate 1, which is similar to a resistance element.

  The protected circuit 4 is a circuit to be protected from damage due to overvoltage by the protective element 5. The protected circuit 4 may be a discrete circuit including elements such as transistors and light emitting diodes, and is an integrated circuit including elements such as IC (Integrated Circuit), LSI (Large-Scale Integration), and semiconductor memory. Alternatively, a circuit combining these may be used.

  The protected circuit 4 is electrically connected to the wiring 31 and the wiring 32 that are separated from each other. Via these wirings 31 and 32, it is possible to apply a driving voltage to the protected circuit 4 and to transmit and receive electrical signals.

  The power source 6 is electrically connected to the wiring 31 and the wiring 32, and a voltage is applied between them. Thereby, the protected circuit 4 can be operated.

  The protection element 5 is provided so as to straddle the wiring 31 and the wiring 32 that are separated from each other. As shown in FIG. 2, the protective element 5 has a shape along the surface of the insulating substrate 2 and the surfaces of the wirings 31 and 32 and is in close contact with these surfaces. Thus, the protection element 5 is electrically connected to the wiring 31 and the wiring 32 and is mechanically fixed to the insulating substrate 2.

  The protection element 5 exhibits non-linearity in which the voltage-current characteristic does not follow Ohm's law. In the present specification, “nonlinearity in which the voltage-current characteristic does not follow Ohm's law” is also referred to as “varistor characteristic”.

  Such a varistor characteristic exhibits insulation while a voltage equal to or lower than a predetermined voltage (varistor voltage of the protective element 5) is applied to a circuit including the protective element 5, and is electrically conductive when a voltage exceeding the predetermined voltage is applied. It is the characteristic which shows sex. When a high voltage exceeding the above-described predetermined voltage is induced between the wiring 31 and the wiring 32, a surge current flows through the protective element 5 exhibiting conductivity due to such varistor characteristics. Thereby, it is possible to suppress application of a voltage exceeding a predetermined voltage to the protected circuit 4.

  Further, by preventing application of a high voltage to the protected circuit 4, damage and deterioration of the protected circuit 4 are suppressed. As a result, the reliability of the mounting substrate 1 can be further increased.

  In addition, as described above, the shape of the protective element 5 is not particularly limited as long as it is a shape that straddles the wiring 31 and the wiring 32, but preferably has a curved convex surface in at least a part of the surface. With such a shape, for example, even when a load is applied to the protective element 5, it is difficult to concentrate stress locally. For this reason, the protection element 5 has crack resistance. In addition, since the peeling due to the concentration of stress is difficult to occur, the protection element 5 has excellent adhesion to the insulating substrate 2 and the wirings 31 and 32.

  Further, the thickness of the protective element 5 is not particularly limited, but is preferably larger than the particle diameter of the semiconductor ceramic particles 51. Thereby, the semiconductor ceramic particles 51 are less likely to drop off in the protection element 5, and the reliability of the protection element 5 can be further increased.

  Specifically, the maximum thickness of the protective element 5 is preferably about 1.1 to 1000 times the average particle diameter D50 of the semiconductor ceramic particles 51, and more preferably about 3.0 to 500 times. . Thereby, the above effect becomes more remarkable.

  Further, the thickness of the protective element 5 is preferably larger than the thickness of the wirings 31 and 32. Thereby, since the protection element 5 wraps around the wirings 31 and 32, the adhesion between the protection element 5 and the wirings 31 and 32 becomes higher. As a result, the reliability of the mounting substrate 1 can be further increased.

Here, another configuration example of the wirings 31 and 32 will be described.
FIG. 3 is a top view illustrating another configuration example of the electrical wiring configuring the electrical circuit illustrated in FIG. 1. In FIG. 3, for convenience of explanation, the outline of the protection element 5 is indicated by a broken line, and the shapes of the wirings 31 and 32 hidden behind the protection element 5 are indicated by a solid line.

  The wiring 31 shown in FIG. 3 has a plurality of branch points 315 that branch into two on the way. At each branch point 315, the wiring 31 branches into a main line 311 and a branch line 312.

  The wiring 32 shown in FIG. 3 also has a plurality of branch points 325 that branch into two in the middle. At each branch point 325, the wiring 32 branches into a main line 321 and a branch line 322.

  The trunk line 311 and the trunk line 321 are parallel to each other as in the relationship between the wiring 31 and the wiring 32 in FIG.

  On the other hand, the extending direction of the branch line 312 is orthogonal to the trunk line 311. The branch line 312 extends toward the wiring 32 side and extends to a position before reaching the wiring 32.

  Further, the extending direction of the branch line 322 is orthogonal to the main line 321. The branch line 322 also extends toward the wiring 31 side and extends to a position before reaching the wiring 31.

  Further, the branch lines 312 and the branch lines 322 are alternately arranged in the extending direction of the wirings 31 and 32. Thereby, each of the wiring 31 and the wiring 32 has a comb-tooth shape in plan view.

  3 is provided at a position including a plurality of branch lines 312 and branch lines 322. As a result, in the mounting substrate 1 shown in FIG. 3, it is possible to secure a larger area where the wiring 31 and the wiring 32 face each other while being separated from each other. For this reason, the protection element 5 can be interposed between the wiring 31 and the wiring 32 in a larger area, and the area where the varistor characteristics can be exhibited can be increased. As a result, it is possible to further improve the varistor characteristics such as an increase in energy resistance. In addition, since the area occupied by the protective element 5 can be reduced without deteriorating the varistor characteristics, compatibility with high-density wiring can be improved.

  The number of branch points 315 provided in the wiring 31 is not particularly limited, and may be one, but is preferably a plurality (for example, about 2 to 100).

  Similarly, the number of branch points 325 provided in the wiring 32 is not particularly limited, and may be one, but is preferably plural (for example, about 2 to 100).

  Moreover, the protection element 5 straddling the wiring 31 and the wiring 32 may be one or plural.

  By the way, such a protection element 5 includes semiconductor ceramic particles 51 and a cured product 52 of resin.

(Semiconductor ceramic particles)
4 is a cross-sectional view taken along the line AA in FIG. 2, and FIG. 5 is a partially enlarged view of the semiconductor ceramic particles shown in FIG.

  The semiconductor ceramic particle 51 shown in FIG. 5 is a particle having a grain boundary part 511 and a plurality of crystal parts 512 separated by the grain boundary part 511. In other words, the semiconductor ceramic particles 51 are secondary particles in which the crystal parts 512 are aggregated via the grain boundary parts 511. The semiconductor ceramic particles 51 do not pass current when a voltage lower than the varistor voltage is applied, because the grain boundary portion 511 acts as a resistance, but when a voltage higher than the varistor voltage is applied. , The tunnel effect is generated, and a current is passed as shown by an arrow in FIG.

  The average particle diameter D50 of the semiconductor ceramic particles 51 is preferably 0.01 μm or more and 1500 μm or less, more preferably 0.1 μm or more and 1000 μm or less, further preferably 1 μm or more and 500 μm or less, and more preferably 5 μm or more. A thickness of 150 μm or less is particularly preferable. Thereby, it is possible to develop the varistor characteristics without depending on the shape of the protection element 5.

  The semiconductor ceramic particles 51 are preferably spherical particles. Thereby, it is possible to easily control the varistor characteristics.

  In the semiconductor ceramic particle 51, the crystal part 512 is preferably formed of a material including one or more selected from the group consisting of zinc oxide, silicon carbide, strontium titanate, and barium titanate. In particular, a material containing zinc oxide as a main component is preferable from the viewpoint of improving the nonlinear coefficient and energy resistance of the semiconductor ceramic particle 51 itself. Since a material containing silicon carbide as a main component has a high dielectric breakdown voltage, it is suitable when the varistor voltage is set to a high voltage. A material containing strontium titanate as a main component is preferable in terms of absorption and suppression of high voltage / high frequency noise.

  In the semiconductor ceramic particle 51, the grain boundary part 511 is preferably formed of a material containing at least one selected from the group consisting of bismuth, praseodymium, antimony, manganese, cobalt and nickel, or a compound thereof. Especially, it is preferable that the grain boundary part 511 is formed from the material containing 1 or more types selected from the group which consists of bismuth, praseodymium, or these compounds from a viewpoint that a nonlinear resistance characteristic is favorable. . Examples of these compounds include oxides, nitrides, organic compounds, other inorganic compounds, and the like, and oxides are preferable from the viewpoint of achieving good varistor characteristics.

  The content of the semiconductor ceramic particles 51 is preferably 20% by mass or more and 90% by mass or less, more preferably 25% by mass with respect to the total amount of the protective element 5 from the viewpoint of more surely expressing the varistor characteristics of the protective element 5. % To 80% by mass, more preferably 30% to 70% by mass. By controlling the content of the semiconductor ceramic particles 51 to be within the above range, the gap between the adjacent wirings 31 and 32 can be easily filled with the semiconductor ceramic particles 51 as shown in the schematic diagram of FIG. Become. Thereby, the energy tolerance of the protection element 5 can be raised more.

  At this time, the semiconductor ceramic particles 51 are preferably in contact with each other. In addition, by controlling the content of the semiconductor ceramic particles 51 to be within the above range, the semiconductor ceramic particles 51 can be easily brought into contact with each other, and the varistor characteristics of the protective element 5 can be expressed more reliably.

  Furthermore, such a protective element 5 can be easily manufactured by applying a composition containing the semiconductor ceramic particles 51 and an uncured resin to an arbitrary place and then curing the resin. It is. For this reason, like the wirings 31 and 32 shown in FIG. 2, when two electrically independent conductive parts are adjacent to each other, the composition is applied so as to straddle them, and then the curing process is only performed. The protection element 5 can be easily formed. Therefore, the protection element 5 has a small space occupancy and a high degree of freedom in arrangement. As a result, the mounting substrate 1 can reduce the material procurement cost and reduce the manufacturing cost as compared with the case where discrete components (varistor elements) are employed, for example.

  When a discrete component such as a chip varistor element is mounted, since soldering is required, it is necessary to perform a solder reflow process on the chip varistor element. For this reason, the insulating substrate 2 is required to have a heat-resistant temperature (for example, around 260 ° C.) exceeding the melting point of the solder.

  On the other hand, in this invention, after apply | coating a composition to arbitrary places as mentioned above, it is possible to manufacture the protection element 5 by hardening resin. For this reason, the temperature required for manufacture is about 50 to 200 ° C., and the heat-resistant temperature required for the insulating substrate 2 can be lowered.

  Note that “so as to straddle the wiring 31 and the wiring 32” means that one protective element 5 is in contact with both the wiring 31 and the wiring 32 and is electrically connected to both. Point to. Therefore, the planar view shape, thickness, and the like of the protection element 5 are not particularly limited.

  Here, the semiconductor ceramic particles 51 are unevenly distributed on the insulating substrate 2 (base) side. That is, in this embodiment, as shown in FIG. 4, the occupation ratio of the semiconductor ceramic particles 51 is high below the cross section of the protective element 5 (on the insulating substrate 2 side), whereas the upper portion (what is the insulating substrate 2)? On the opposite side), the occupation ratio of the cured resin 52 is high.

  In such a protection element 5, the semiconductor ceramic particles 51 are accumulated on the insulating substrate 2 side, that is, on the wirings 31 and 32 side. For this reason, the semiconductor ceramic particles 51 are arranged at a high density between the wiring 31 and the wiring 32, and the protective element 5 having particularly good varistor characteristics can be obtained. Therefore, the mounting substrate 1 including the protection element 5 can satisfactorily relax the overvoltage applied to the protected circuit 4.

  In addition, since the semiconductor ceramic particles 51 are unevenly distributed on the insulating substrate 2 side, the ratio of the semiconductor ceramic particles 51 in the entire protection element 5 is reduced without significantly impairing the varistor characteristics of the protection element 5, and on the contrary, a cured resin. The ratio of 52 can be increased. That is, among the semiconductor ceramic particles 51, the particles that are located between the wiring 31 and the wiring 32 contribute to the expression of the varistor characteristics. Therefore, the particles existing in the other parts have the varistor characteristics. Difficult to contribute directly to expression. Therefore, by making the semiconductor ceramic particles 51 unevenly distributed, the ratio of the cured resin 52 can be increased without impairing the varistor characteristics.

  Thus, the reliability of the protection element 5 can be improved by increasing the ratio of the cured resin 52. That is, the protective element 5 has a higher ratio of the cured resin 52 so that the semiconductor ceramic particles 51 are bonded to each other, or the protective element 5 is more closely attached to the insulating substrate 2 and the wirings 31 and 32. Can be increased. As a result, for example, the protective element 5 showing sufficient reliability can be obtained even when subjected to a temperature cycle test.

  Furthermore, by making the semiconductor ceramic particles 51 unevenly distributed on the insulating substrate 2 side, the ratio of the semiconductor ceramic particles 51 in the entire protection element 5 can be reduced. Thereby, the usage-amount of the expensive semiconductor ceramic particle 51 can be reduced, and cost reduction of the protection element 5 can be achieved. In addition, the protective element 5 can be reduced in weight by reducing the amount of semiconductor ceramic particles 51 having a relatively large specific gravity. For this reason, weight reduction of the mounting substrate 1 can be achieved, and weight reduction of the electronic device etc. in which the mounting substrate 1 is mounted can also be achieved. In particular, in the case of an electronic device having a large number of protective elements 5 mounted, such as a mobile phone, the weight can be further reduced accordingly.

  In the protection element 5, when the semiconductor ceramic particles 51 are unevenly distributed downward (insulating substrate 2 side) in FIG. 4, the cured resin 52 is unevenly distributed upward (opposite side of the insulating substrate 2). It becomes. Since the cured product 52 has a low content of the semiconductor ceramic particles 51, it is difficult to exhibit varistor characteristics. For this reason, the upper part (part in which the hardened | cured material 52 is unevenly distributed) may be removed as needed. For this removal, for example, a polishing method or the like is used.

  On the other hand, by making the semiconductor ceramic particles 51 unevenly distributed on the insulating substrate 2 side, the linear expansion coefficient on the insulating substrate 2 side of the protective element 5 can be lowered from the average of the protective element 5 as a whole. Thereby, since the thermal expansion coefficient in the insulating substrate 2 side among the protection elements 5 can be brought close to the thermal expansion coefficient of the insulating substrate 2, the difference in thermal expansion coefficient between them can be reduced. As a result, it is possible to prevent the protective element 5 from being peeled off from the insulating substrate 2 and the wirings 31 and 32 as the temperature changes, so that the temperature cycle reliability of the protective element 5 can be further improved. In addition, the electrical connection between the wirings 31 and 32 and the protection element 5 is facilitated, and the varistor characteristics can be expressed more reliably.

  Note that “the semiconductor ceramic particles 51 are unevenly distributed on the insulating substrate 2 side” means that, for example, in the gap between the wiring 31 and the wiring 32 in FIG. 4 is a state in which the volume fraction of the semiconductor ceramic particles 51 in the lower part (4) is larger than the volume fraction of the semiconductor ceramic particles 51 on the opposite side of the insulating substrate 2 from the intermediate line (upper part in FIG. 4). Note that the intermediate line of the thickness of the protective element 5 is a line segment corresponding to the maximum thickness of the protective element 5 in a cross-sectional view as shown in FIG. A straight line that passes through the middle point of the line segment having the maximum length and is orthogonal to the line segment.

  Preferably, when the volume fraction of the semiconductor ceramic particles 51 on the insulating substrate 2 side is 1, the volume fraction of the semiconductor ceramic particles 51 on the side opposite to the insulating substrate 2 is 0 or more and 0.90 or less. More preferably, they are 0.001 or more and 0.80 or less, More preferably, they are 0.01 or more and 0.70 or less. When the uneven distribution state of the semiconductor ceramic particles 51 is within the above range, the varistor characteristics and the temperature cycle reliability of the protection element 5 can be made more highly compatible.

  If the volume fraction on the side opposite to the insulating substrate 2 exceeds the upper limit value, it is almost unevenly distributed, so that, for example, when the ratio of the cured resin 52 is increased, the semiconductor ceramic particles 51 There is a possibility that the filling rate of the varistor will be reduced and the varistor characteristics may be lowered.

  In addition, calculation of the said volume fraction can be substituted by calculating | requiring the area ratio of the semiconductor ceramic particle 51 in sectional drawing as shown in FIG.

(resin)
The cured product 52 of the resin may be a cured product of a thermosetting resin, a cured product of a photocurable resin, or a solidified product of a thermoplastic resin. In the present invention, the cured resin 52 includes a solidified product. Similarly, “curing” in the present invention includes solidification.

  Among these, as curable resins, for example, phenol novolak resins, cresol novolak resins, bisphenol A type novolak resins, triazine skeleton-containing phenol novolak resins and the like novolak type phenol resins; unmodified resole phenol resins, tung oil, linseed oil, Phenolic resin such as oil-modified resol phenolic resin modified with walnut oil etc .; bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, bisphenol E type epoxy resin, bisphenol M type epoxy Resin, bisphenol P type epoxy resin, bisphenol type epoxy resin such as bisphenol Z type epoxy resin; phenol novolac type epoxy resin, cresol novolac type epoxy resin Novolac type epoxy resins such as biphenyl type epoxy resins, biphenyl aralkyl type epoxy resins, aryl alkylene type epoxy resins, naphthalene type epoxy resins, anthracene type epoxy resins, phenoxy type epoxy resins, dicyclopentadiene type epoxy resins, norbornene type epoxy resins Epoxy resins such as adamantane type epoxy resins and fluorene type epoxy resins; resins having a triazine ring such as urea (urea) resins and melamine resins; unsaturated polyester resins; maleimide resins such as bismaleimide compounds; polyurethane resins; diallyl phthalates Resin; Silicone resin; Benzoxazine resin; Polyimide resin; Polyamideimide resin; Benzocyclobutene resin, Novolak type cyanate resin, Bisphenol A type cyanene DOO resin, bisphenol E type cyanate resin, cyanate ester resins such as bisphenol type cyanate resins such as tetramethyl bisphenol F type cyanate resins. One of these may be used alone, two or more having different weight average molecular weights may be used in combination, or one or two or more thereof and a prepolymer thereof may be used in combination. .

  On the other hand, as the thermoplastic resin, for example, olefin resin such as polyethylene, polypropylene, polynorbornene, benzocyclobutene resin, polyamide resin, thermoplastic urethane resin, polycarbonate resin, polyethylene terephthalate, polybutylene terephthalate, Polyester resin such as polyethylene naphthalate, polyacetal, polyphenylene sulfide, polyether ether ketone, liquid crystal polymer, fluororesin such as polytetrafluoroethylene and polyvinylidene fluoride, modified polyphenylene ether, polysulfone, polyethersulfone, polyarylate , Polyamideimide, polyetherimide, thermoplastic polyimide, etc., and those containing one or more of these are used. It is.

  The content of the resin is preferably 10% by mass or more and 80% by mass or less, more preferably 20% by mass or more and 75% by mass or less, based on the total amount of the composition including the resin before curing and the semiconductor ceramic particles 51. More preferably, it is 30 mass% or more and 70 mass% or less, Most preferably, it is 40 mass% or more and 60 mass% or less. By setting the content of the resin within the above range, the fluidity when the composition is heated can be improved. In addition, the heat dissipating property of the protective element 5 can be improved, and the varistor characteristics of the protective element 5 can be improved.

  As the resin, those containing a silicone resin, epoxy resin, olefin resin or benzocyclobutene resin are preferably used, and those containing an epoxy resin or silicone resin are more preferably used. By using these, when a voltage lower than the varistor voltage is applied to the protective element 5, it shows good insulation, while when the voltage higher than the varistor voltage is applied to the protective element 5, the withstand voltage is excellent. The protective element 5 is obtained. In addition, the protective element 5 including the cured product 52 of the curable resin has both good heat resistance and moisture resistance and good adhesion to the insulating substrate 2.

  Hereinafter, the silicone resin, epoxy resin, olefin resin, and benzocyclobutene resin will be described in detail.

・ Epoxy-based resin By using epoxy-based resin, high-voltage protection member is formed that is superior in terms of productivity, moldability, shape follow-up to the object to be sealed, heat resistance, moisture resistance, adhesion, electrical characteristics, etc. The resin composition can be used.

  As said epoxy resin, it is possible to use the monomer, oligomer, and polymer in general which have 2 or more of epoxy groups in 1 molecule irrespective of the molecular weight and molecular structure. Specific examples of such epoxy resins include biphenyl type epoxy resins, bisphenol A type epoxy resins, bisphenol F type epoxy resins, stilbene type epoxy resins, hydroquinone type epoxy resins and the like; cresol novolac type epoxy resins, Novolak type epoxy resins such as phenol novolac type epoxy resin and naphthol novolak type epoxy resin; Phenol aralkyl type epoxy such as phenylene skeleton-containing phenol aralkyl type epoxy resin, biphenylene skeleton containing phenol aralkyl type epoxy resin, phenylene skeleton containing naphthol aralkyl type epoxy resin Resin: Triphenolmethane type epoxy resin, alkyl-modified triphenolmethane type epoxy resin, glycidylamine, tetrafunctional naphthalene type Polyfunctional epoxy resins such as Poxy resin; Modified phenol type epoxy resins such as dicyclopentadiene modified phenol type epoxy resin, terpene modified phenol type epoxy resin and silicone modified epoxy resin; Heterocycle containing epoxy resins such as triazine nucleus-containing epoxy resin Naphthylene ether type epoxy resins and the like, and these may be used alone or in combination of two or more.

Moreover, when using an epoxy resin, a hardening | curing agent may be added with it.
Any curing agent may be used as long as it can be cured by reacting with a curable resin. Specific examples of curing agents that can be used when an epoxy resin is used include ethylenediamine, trimethylenediamine, tetramethylenediamine, and hexamethylene. C2-C20 linear aliphatic diamine such as diamine, metaphenylenediamine, paraphenylenediamine, paraxylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diamino Diphenyl ether, 4,4′-diaminodiphenylsulfone, 4,4′-diaminodicyclohexane, bis (4-aminophenyl) phenylmethane, 1,5-diaminonaphthalene, metaxylenediamine, paraxylenediamine, 1,1-bis (4-Aminophenyl) cyclohexane, DISHI Aminos such as nodiamide; resol-type phenol resins such as aniline-modified resole resin and dimethyl ether resole resin; novolac-type phenol resins such as phenol novolac resin, cresol novolac resin, tert-butylphenol novolac resin, nonylphenol novolac resin; Resin, phenol aralkyl resin such as biphenylene skeleton-containing phenol aralkyl resin; phenol resin having condensed polycyclic structure such as naphthalene skeleton and anthracene skeleton; polyoxystyrene such as polyparaoxystyrene; hexahydrophthalic anhydride (HHPA), methyltetrahydro Aliphatic acid anhydrides such as phthalic anhydride (MTHPA), trimellitic anhydride (TMA), pyromellitic anhydride (PMDA) Acid anhydrides including aromatic acid anhydrides such as benzophenone tetracarboxylic acid (BTDA); polymercaptan compounds such as polysulfides, thioesters, thioethers; isocyanate compounds such as isocyanate prepolymers, blocked isocyanates; carboxylic acid-containing polyesters Examples thereof include organic acids such as resins. These may be used alone or in combination of two or more. In particular, from the viewpoint of improving the moisture resistance and reliability of the protective element 5, a compound having at least two phenolic hydroxyl groups in one molecule is preferable. Specific examples thereof include phenol novolac resin, cresol novolac resin, tert-butylphenol. Novolak type resins such as novolak resins and nonylphenol novolak resins; resol type phenol resins; polyoxystyrenes such as polyparaoxystyrene; phenylene skeleton-containing phenol aralkyl resins, biphenylene skeleton-containing phenol aralkyl resins, phenylene skeleton-containing naphthol aralkyl type phenol resins Is mentioned.

Silicone resin In addition to the effects described above, the silicone resin has properties unique to the silicone resin, that is, a resin material, but due to the inorganic properties derived from Si, Excellent affinity can be imparted to the protective element 5. For this reason, the protection element 5 can be more firmly attached to the insulating substrate 2 and the wirings 31 and 32.

  The composition of the silicone resin is not particularly limited as long as it is a curable silicone resin. The curing type includes a condensation reaction type and an addition reaction type, and examples of the condensation reaction type include a deacetic acid type, a dealcohol type, a deacetone type, and a deoxime type. In addition, the addition reaction type is generally cured by a hydrosilylation reaction between a silicone resin having a vinyl group and a silicone resin having a hydrogen atom. Addition-reactive silicone resins are particularly preferred because they do not produce by-products associated with the curing reaction, have small curing shrinkage, and can be cured in a short time by heat.

  The main component and curing agent of the curable silicone resin are at least one of a unit derived from a monofunctional silane, a unit derived from a bifunctional silane, a unit derived from a trifunctional silane, and a unit derived from a tetrafunctional silane. May be included as a repeating unit.

  Here, the unit derived from monofunctional silane refers to a repeating unit (M unit) represented by the following general formula (1).

R ₃ SiO _1/2 (1)
[However, R represents a non-reactive functional group such as a methyl group, an ethyl group, a propyl group, a cyclohexyl group, or a phenyl group, or a reactive functional group such as a vinyl group, a hydrogen atom, a hydroxy group, an alkoxy group, or an epoxy group. Show. ]

  Moreover, the unit derived from bifunctional silane means the repeating unit (D unit) represented by following General formula (2).

R ₂ SiO _2/2 (2)
[However, R represents a non-reactive functional group such as a methyl group, an ethyl group, a propyl group, a cyclohexyl group, or a phenyl group, or a reactive functional group such as a vinyl group, a hydrogen atom, a hydroxy group, an alkoxy group, or an epoxy group. Show. ]

  Moreover, the unit derived from a trifunctional silane means a repeating unit (T unit) represented by the following general formula (3).

RSiO _3/2 (3)
[However, R represents a non-reactive functional group such as a methyl group, an ethyl group, a propyl group, a cyclohexyl group, or a phenyl group, or a reactive functional group such as a vinyl group, a hydrogen atom, a hydroxy group, an alkoxy group, or an epoxy group. Show. ]

Moreover, the unit derived from tetrafunctional silane means a repeating unit (Q unit) represented by the following general formula (4).
SiO _4/2 (4)

-Olefin resin The olefin resin may be a chain olefin resin, but a cyclic olefin resin is preferably used, and a norbornene resin is more preferably used.

  Examples of the norbornene-based resin include (co) polymers of norbornene monomers, copolymers of norbornene monomers and other monomers that can be copolymerized such as α-olefins, and hydrogenation of these copolymers. Thing etc. are mentioned. These norbornene-based resins can be produced by a known polymerization method, and there are an addition polymerization method and a ring-opening polymerization method. Of these, polymers obtained by addition (co) polymerization of norbornene monomers are preferably used. As the polymerization method, a known method such as random polymerization or block polymerization is used.

  Here, as norbornene-type resin used by this embodiment, what contains the repeating structure represented by the following general formula is mentioned.

［上記式中のＸは、−ＣＨ_２−、−ＣＨ_２ＣＨ_２−、または−Ｏ−を示し、Ｒ１、Ｒ２、Ｒ３、Ｒ４はそれぞれ独立して水素原子、炭化水素基、または炭素数１〜１２の極性基を示し、該極性基は直鎖もしくは分岐したアルキル基、アルケニル基、アルキニル基、ビニル基、アリル基、アラルキル基、環状脂肪族基、アリール基、またはエーテル基により結合されていてもよい。また、ｎは、０から２の整数を示し、ｎが１以上の場合、複数の繰り返し単位は互いに異なっていてもよい。］

[X in the above _{formulas, -CH 2 -, - CH 2} CH 2 -, or -O- are shown, R1, R2, R3, R4 each independently represent a hydrogen atom, a hydrocarbon group or a carbon atoms, To 12 polar groups, which are linked by linear or branched alkyl groups, alkenyl groups, alkynyl groups, vinyl groups, allyl groups, aralkyl groups, cycloaliphatic groups, aryl groups, or ether groups. May be. N represents an integer of 0 to 2, and when n is 1 or more, the plurality of repeating units may be different from each other. ]

-Benzocyclobutene-type resin As a benzocyclobutene-type resin, what contains the structure represented by the following general formula or the structure by which these structures are prepolymerized is mentioned, for example.

［Ｒ^１は脂肪族、芳香族、ヘテロ原子、またはこれらの組み合わせを示し、Ｒ^２、Ｒ^３はそれぞれ独立して水素原子、脂肪族、芳香族、ヘテロ原子、またはこれらの組み合わせを示す。］

[R ¹ represents an aliphatic, aromatic, heteroatom, or a combination thereof, and R ² and R ³ each independently represent a hydrogen atom, an aliphatic, an aromatic, a heteroatom, or a combination thereof. ]

Note that these resins preferably have a relative dielectric constant ε _r of 4 or less, more preferably 3.5 or less, and even more preferably 3.2 or less. By using such a resin, resistance to overvoltage such as surge (abnormal voltage) or ESD (electrostatic discharge) (hereinafter, also referred to as “ESD resistance”) can be enhanced. Thereby, even if an overvoltage is applied to the circuit including the cured product 52, the cured product 52 itself can be prevented from being deteriorated by the overvoltage. As a result, even if an overvoltage is applied a plurality of times, it is possible to maintain sufficient varistor characteristics and suppress, for example, the application of a high voltage to the semiconductor element (protected circuit 4). Thereby, it is possible to realize the protective element 5 exhibiting sufficient varistor characteristics even when the volume is small. As a result, it is possible to obtain the protection element 5 that has a low space occupancy and a high degree of freedom in arrangement that can be arranged in a narrow space.

  The clear reason why such an effect occurs is not clear, but when the relative dielectric constant exceeds the above range, the charge accumulated in the resin is relatively increased. It is inferred that the ease will increase.

On the other hand, the lower limit value of the relative dielectric constant ε _r of the resin may not be particularly limited, but the relative dielectric constant ε _r is preferably 1.5 or more, more preferably 2 or more. As a result, for example, in a normal circuit where the overvoltage is not applied to the circuit including the cured product 52, the fluctuation of the power supply voltage applied to the circuit is absorbed to suppress the generation of noise and the diffusion of noise. can do.

The relative dielectric constant ε _r of the resin is obtained as follows.
FIG. 6 is a diagram for explaining a method of measuring the relative dielectric constant of a resin. FIG. 6A is a plan view showing a state in which the relative dielectric constant is measured for a test piece 13F (cured product) formed by molding a resin into a film and cured, and FIG. 6B is a plan view of FIG. It is the side view which looked at a) from the side.

  First, as shown in FIG. 6B, the test piece 13F is placed on the upper surface of the counter electrode 41 made of, for example, aluminum. And the main electrode 42 and the guard electrode 43 which were formed with the electrically conductive paste are mounted in the upper surface of the test piece 13F. Each of the counter electrode 41 and the test piece 13F has a square shape of 50 mm long × 50 mm wide in plan view. The main electrode 42 has a circular shape with a diameter of 18 mm in plan view, and is placed so that the center of the test piece 13F and the center of the main electrode 42 coincide. Furthermore, the guard electrode 43 has an annular shape with an inner diameter of 20 mm and an outer diameter of 26 mm in plan view, and is placed so that the main electrode 42 is positioned on the inner diameter side. As a result, the main electrode 42 and the guard electrode 43 are placed concentrically with each other.

Next, each electrode is connected to an LCR meter (for example, HP-4284A manufactured by Agilent Technologies), and a parallel capacitance C _p [F] and conductance G [S] at a measurement frequency of 1 MHz are measured.

Then, the measured values are substituted into the following formulas (8) and (9) to calculate the relative dielectric constant ε _r and the dielectric loss tangent tan δ. In the equation, f is the measurement frequency, t is the thickness [m] of the test piece 13F, d is the diameter [m] of the main electrode 42, and ε ₀ is the dielectric constant of vacuum (= 8.854 × 10 ⁻¹² [ F / m]).

The measurement environment is an air temperature of 22 ° C. and a relative humidity of 56%.
The thickness t of the test piece 13F is measured by, for example, a micrometer manufactured by Mitutoyo Corporation. The measuring method is as follows.

  First, the thickness of five places is measured about the laminated body of the counter electrode 41 and the test piece 13F, and the arithmetic mean value is calculated | required.

Next, the thickness of 10 locations of the counter electrode 41 alone is measured, and the arithmetic average value is obtained.
And the arithmetic mean value of the thickness about the counter electrode 41 is subtracted from the arithmetic mean value of the thickness about the laminated body, and this is made into the thickness t of the test piece 13F.

The relative dielectric constant ε _r and the dielectric loss tangent tan δ are obtained as an average value of three values measured by preparing three test pieces 13F.
The relative dielectric constant ε _r and the dielectric loss tangent tan δ are obtained as described above.

Additives Other additives may be added to the composition for forming the protective element 5.

  Examples of other additives include inorganic fillers, adhesion assistants, reaction inhibitors, and curing catalysts.

  Among these, although it does not specifically limit as a constituent material of an inorganic filler, For example, a silica, titanium dioxide, an alumina, a calcium carbonate, a calcium silicate, iron oxide, a zinc oxide etc. are mentioned. By adding such an inorganic filler, the thermal expansion coefficient of the cured product 52 can be reduced and the difference in thermal expansion from the adherend can be reduced, but the varistor characteristics may be reduced. . Therefore, it is preferable that the addition amount of the inorganic filler is a ratio of 100 parts by mass or less with respect to 100 parts by mass of the total amount of the silicone resin.

  In addition, it is preferable that the average particle diameter of an inorganic filler is 0.001-150 micrometers, and it is more preferable that it is 0.01-100 micrometers. Thereby, a thermal expansion coefficient can be adjusted efficiently and it can suppress that the mechanical characteristic of the protection element 5 falls.

  Further, the adhesion assistant is not particularly limited. For example, when a silicone resin is used as the resin, a hydrogen atom bonded to a silicon atom, an alkenyl group bonded to a silicon atom, an alkoxysilyl group, an epoxy group, etc. A siloxane monomer or siloxane oligomer containing a functional group is preferably used. When an epoxy resin is used as the resin, a functional silane cup having a reactive substituent such as a carboxyl group, a methacryloyl group, an isocyanate group, or an epoxy group. A ring agent or the like is preferably used. The adhesion assistant is preferably added at a ratio of 10 parts by mass or less, more preferably from 0.1 to 8 parts by mass with respect to 100 parts by mass of the total amount of the resin. By adding such an adhesion assistant, the adhesion of the cured product 52 to the adherend can be further increased.

  The reaction inhibitor is not particularly limited. For example, when a silicone resin is used as the resin, triallyl isocyanurate, alkyl maleate, acetylene alcohols, silane-modified products of acetylene alcohols, and acetylene alcohols. Siloxane modified product, hydroperoxide, tetramethylethylenediamine, benzotriazole, etc. are preferably used, and when an epoxy resin is used as the resin, boron compounds such as trimethyl borate and triethyl borate, sulfuric acid, acetic acid, adipic acid, Preference is given to acidic compounds such as tartaric acid, fumaric acid, barbitic acid, boric acid, pyrogallol, phenolic resins, carboxylic acid anhydrides, and the like. The reaction inhibitor is preferably added at a rate of 0.001 to 1.0 part by mass with respect to 100 parts by mass of the total amount of the resin, and is added at a rate of 0.005 to 0.5 part by mass. Is more preferable. By adding such a reaction inhibitor, the curing reaction of the composition for forming the protective element 5 can be suppressed, and the storage stability can be improved.

The curing catalyst is not particularly limited. For example, when a silicone resin is used as the resin, H ₂ PtCl ₆ · mH ₂ O, K ₂ PtCl ₆ , KHPtCl ₆ · mH ₂ O, K ₂ PtCl ₄ , K ₂ PtCl ₄ · mH ₂ O, PtO ₂ · mH ₂ O (m is a positive integer for each), complexes of these compounds with hydrocarbons such as olefins, alcohols or vinyl group-containing organopolysiloxanes, etc. When an epoxy resin is used as the resin, a diazabicycloalkene such as 1,8-diazabicyclo (5,4,0) undecene-7 and its derivatives, tributylamine, benzyldimethylamine and the like are used. Amine compounds, imidazole compounds such as 2-methylimidazole, triphenylphosphine , Organic phosphines such as methyldiphenylphosphine, tetraphenylphosphonium / tetraphenylborate, tetraphenylphosphonium / tetrabenzoic acid borate, tetraphenylphosphonium / tetranaphthoic acid borate, tetraphenylphosphonium / tetranaphthoyloxyborate, Tetra-substituted phosphonium / tetra-substituted borate such as tetraphenylphosphonium / tetranaphthyloxyborate, triphenylphosphine adducted with benzoquinone, and the like are preferably used. For example, when a silicone resin is used as the resin, the addition amount of the curing catalyst is preferably 0.1 to 500 ppm, more preferably 0.5 to 100 ppm by mass ratio with respect to the total amount of the resin. . In addition, for example, when an epoxy resin is used as the resin, the addition amount of the curing catalyst is preferably 0.05 to 10% by mass, more preferably 0.1 to 5% by mass of the total amount of the resin. preferable.

  Furthermore, conductive particles are also mentioned as an additive. By adding conductive particles, when a voltage exceeding the varistor voltage is applied to the protective element 5, the electrical conductivity of the protective element 5 can be further increased. That is, when conductive particles enter between the wiring 31 and the wiring 32, an electron conduction path when the varistor voltage is exceeded can be formed. Thereby, the varistor characteristic of the protection element 5 can be made more favorable.

  The content of the conductive particles is preferably 1% by mass or more and 20% by mass or less, more preferably, in the total amount of the composition for forming the protection element 5, from the viewpoint of sufficiently expressing the varistor characteristics of the protection element 5. It is 2 mass% or more and 15 mass% or less, More preferably, it is 2 mass% or more and 10 mass% or less. By controlling the content of the conductive particles to be within the above range, the conductive particles can be more surely entered into the gaps between the plurality of semiconductor ceramic particles 51 that have entered between the wiring 31 and the wiring 32. It becomes possible.

  The average particle diameter D50 of the conductive particles is preferably 0.01 μm or more and 500 μm or less, and more preferably 0.02 μm or more and 300 μm or less, from the viewpoint of sufficiently expressing the varistor characteristics of the protective element 5. The thickness is more preferably 0.05 μm or more and 200 μm or less, and particularly preferably 0.1 μm or more and 100 μm or less.

  The average particle diameter D50 of the conductive particles refers to, for example, a 50% cumulative particle diameter in a mass-based particle size distribution obtained using a laser diffraction particle size distribution measuring apparatus.

  Specific examples of the material forming the conductive particles include a conductive material selected from the group consisting of nickel, carbon black, aluminum, silver, gold, copper, graphite, zinc, iron, stainless steel, tin, brass, and alloys thereof. Examples thereof include a material and a semiconductive material selected from the group consisting of zinc oxide, silicon carbide, strontium titanate, and barium titanate.

  Moreover, it is preferable that the size of the semiconductor ceramic particles 51 and the conductive particles included in the protective element 5 satisfy the following conditions. Specifically, when the average particle diameter D50 of the semiconductor ceramic particles 51 is x and the average particle diameter D50 of the conductive particles is y, the value of y / x is preferably 0.05 or more and less than 1. More preferably, it is 0.1 or more and 0.8 or less. As a result, the conductive particles can more surely enter the gaps between the plurality of semiconductor ceramic particles 51 that have entered between the wiring 31 and the wiring 32.

  Although the protective element 5 has been described above, the composition for forming the protective element 5 may exhibit thixotropic properties. As a result, when the forming composition is supplied using an arbitrary supply device, it softens in accordance with the shearing force and exhibits excellent fluidity, while being applied to the gap between the wiring 31 and the wiring 32. After that, a decrease in fluidity (increase in viscosity) occurs. As a result, the forming composition can achieve both high efficient application workability and high application accuracy by utilizing this thixotropic property.

<< Second Embodiment >>
Next, a second embodiment of the mounting board of the present invention and a second embodiment of the protection element of the present invention included therein will be described.

FIG. 7 is a partial cross-sectional view of the second embodiment of the mounting board of the present invention.
Hereinafter, although 2nd Embodiment is described, in the following description, it demonstrates centering around difference with 1st Embodiment, The description is abbreviate | omitted about the same matter.

  The mounting substrate 1 according to the present embodiment is further provided on the surface of the insulating substrate 2, and has the solder resist film 7 that covers a part of the wirings 31 and 32. The mounting substrate according to the first embodiment Same as 1.

  The mounting substrate 1 shown in FIG. 7 includes an insulating substrate 2 (base portion), two wirings 31 and 32 (conductive portions) that are provided on the surface of the insulating substrate 2 and are spaced apart from each other, and the wirings 31 and 32 are electrically connected. Connected protected circuit (electronic component, not shown), the protection element 5 provided across the wiring 31 and the wiring 32, and the solder resist film 7 described above. .

  The solder resist film 7 is provided so as to cover a part of the wirings 31 and 32, thereby protecting the wirings 31 and 32 from oxidation and corrosion.

  Such a solder resist film 7 is comprised with various resin materials, and an inorganic filler is added as needed.

  The average thickness of the solder resist film 7 is not particularly limited, but is preferably about 5 to 100 μm, and more preferably about 15 to 50 μm.

  The solder resist film 7 includes an opening 71 corresponding to a region including the gap 33 between the wiring 31 and the wiring 32. Accordingly, the wirings 31 and 32 and the gap 33 between them are exposed from the opening 71.

  In addition, in this embodiment, the protection element 5 is provided so as to straddle the wiring 31 and the wiring 32. That is, the protective element 5 is provided so as to fill the gap 33. Thereby, similarly to the first embodiment, the protection element 5 causes a surge current to flow through the protection element 5 when a high voltage exceeding the varistor voltage is induced between the wiring 31 and the wiring 32, thereby Application of a high voltage to the protected circuit 4 can be suppressed.

  In addition, in the present embodiment, the protective element 5 is provided so as to protrude from the surface of the solder resist film 7. That is, the protection element 5 shown in FIG. 7 fills the gap 33 between the wiring 31 and the wiring 32 and the opening 71 of the solder resist film 7 and protrudes from the opening 71 onto the surface of the solder resist film 7. As a result, the protective element 5 partially overlaps the solder resist film 7.

  As in the first embodiment, such a mounting substrate 1 suppresses application of a high voltage to the protected circuit 4 by an electrical action provided by the protection element 5, while the protection element 5 is made of a solder resist film. By protruding over the surface of the protective layer 5, the protective element 5 can also have the function of the solder resist film 7. That is, by providing the opening 71, the function of the solder resist film 7 that protects the wirings 31 and 32 is lost in that portion, but by providing the protective element 5 in the opening 71, Reduced function can be compensated.

  At this time, even if a gap is generated between the protective element 5 and the solder resist film 7 because the protective element 5 protrudes from the surface of the solder resist film 7, the protective element 5 is covered with the gap. Can be covered. As a result, the gap is closed and the wirings 31 and 32 can be more reliably protected.

  In addition, when the length of the portion where the protective element 5 and the solder resist film 7 overlap is L1, and the thickness of the solder resist film 7 is t, the length L1 is not particularly limited, but 0.5 t to It is preferably about 500 t, more preferably about 1 t to 100 t, and even more preferably about 2 t to 50 t. Thereby, both the function of protecting the wirings 31 and 32 and the space saving property of the protective element 5 can be achieved. That is, when L1 is less than the lower limit, the contact area between the solder resist film 7 and the protective element 5 is shortened, so that there is a high probability that a gap is formed between the two, and moisture, oxygen, etc. easily enter the gap. There is a risk. On the other hand, when L1 exceeds the upper limit, the function of protecting the wirings 31 and 32 is enhanced, but the area of the protective element 5 becomes too large, so that the wirings 31 and 32 are laid at a high density in a narrow range. There is a risk that adjacent protective elements 5 may interfere with each other.

<Method for manufacturing protective element>
Next, an embodiment of a method for manufacturing a protection element of the present invention will be described.

  8 and 9 are cross-sectional views for describing an embodiment of a method for manufacturing a protection element of the present invention.

  The manufacturing method of the protection element 5 according to the present embodiment includes: [1] preparing the insulating substrate 2 on which the wirings 31 and 32 are formed and the protected circuit 4 (electronic component) is placed; [2] A step of applying a composition 50 containing semiconductor ceramic particles 51 and an uncured resin, and [3] a step of obtaining the protective element 5 by curing the resin in the composition 50. Hereinafter, each process will be described sequentially.

[1] First, as shown in FIG. 8A, wirings 31 and 32 are formed on the insulating substrate 2, and the protected circuit 4 (not shown in FIGS. 8 and 9) is placed.

  The method for forming the wirings 31 and 32 is not particularly limited. For example, a method of forming and patterning a conductive layer in advance, a method of applying a conductive material along a wiring pattern, a method of forming a film by electrolysis or electroless plating, and the like can be mentioned.

  The protected circuit 4 is electrically connected to the wirings 31 and 32 through, for example, reflow processing.

  Note that this step may be performed as necessary, and the wirings 31 and 32 and the protected circuit 4 may be arranged on the insulating substrate 2 in advance.

  Further, the protected circuit 4 may be placed after the protective element 5 described later is formed.

  Further, the surface of the insulating substrate 2 may be subjected to a lyophilic treatment or a liquid repellent treatment as necessary. Among these, by performing the lyophilic treatment, the affinity between the surface of the insulating substrate 2 and the composition 50 described later is improved, so that the composition 50 can be more reliably applied to the target region. In other words, in the region subjected to the lyophilic treatment, the adhesion of the composition 50 is improved, so that the adhesion between the protective element 5 obtained from the composition 50 and the insulating substrate 2 can be further increased. As a result, a more reliable mounting substrate 1 can be obtained.

  On the other hand, when the liquid-repellent treatment is performed, the affinity between the surface of the insulating substrate 2 and the composition 50 is lowered in that region, and it is easily repelled. By utilizing this, the region to which the composition 50 is applied can be controlled more reliably. In other words, the composition 50 can be more easily and accurately applied to the target region by performing the liquid repellent treatment on the region surrounding the region where the composition 50 is to be applied.

  In addition, the lyophilic treatment and the liquid repellent treatment are appropriately selected according to the composition of the composition 50, for example, plasma treatment, corona treatment, electron beam irradiation treatment, coupling agent treatment, roughening treatment, etc. Can be mentioned. Two or more types of processing may be performed.

[2]
[2-1] Next, a composition 50 containing the semiconductor ceramic particles 51 and an uncured resin is prepared.

  The composition 50 is prepared in a liquid form (paste form) by mixing the semiconductor ceramic particles 51 and an uncured resin and diluting with a solvent or the like as necessary.

  The mixing method is not particularly limited as long as each component is uniformly dispersed and mixed. Specifically, it is mixed by ultrasonic dispersion, a disper, a three roll mill, a ball mill, a bead mill, a twin screw kneader, a self-revolving stirrer or the like.

  The solvent is not particularly limited as long as it is compatible with the resin. For example, water, diols, alcohol, polyol, glycol ether, 1-methylpyrrolidinone, pyridine, terpineol, butyl carbitol, butyl carbitol. Acetate, texanol, phenoxypropanol, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, ethylene glycol monobutyl ether acetate, diethylene glycol monobutyl ether acetate, γ-butyrolactone, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, methoxybutyl acetate, methoxypropyl Acetate, diethylene glycol monoethyl ether acetate, Examples include ethyl, 1-octanol, acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone (MIBK), toluene, xylene, mesitylene, ethyl acetate, cyclohexane, cyclohexanone, etc., including one or more of these A mixed solvent may be used.

  The amount of the solvent used is appropriately set in consideration of the applicability of the composition 50. As an example, it is preferably about 0.3 to 50% by mass with respect to the total amount of the semiconductor ceramic particles 51 and the resin, It is more preferably about 0.5 to 30% by mass, and further preferably about 1 to 25% by mass. Thereby, when apply | coating the composition 50, the application | coating precision can be improved and the dimensional accuracy of the protection element 5 finally obtained can be improved. As a result, for example, even when the wirings 31 and 32 are laid at a high density in a narrow area, the composition 50 can be accurately applied to the target range, and protection suitable for the high-density wiring is achieved. Element 5 is obtained.

  The composition 50 may contain, for example, a dispersant, a leveling agent, a viscosity modifier, a defoaming agent, a colorant such as a pigment, a dye, or the like as an additive other than those described above.

  Examples of the colorant include one or more selected from the group consisting of a dye exhibiting a color such as green, red, blue, yellow, and black, a pigment exhibiting a color such as black, and a pigment. .

  Among these, examples of the green colorant include those containing one or more known colorants such as anthraquinone, phthalocyanine, and perylene.

  Examples of the black dye include azo-based metal complex black dyes and organic black dyes such as anthraquinone compounds. Although it does not specifically limit as the said black dye, For example, Kayase Black AN (made by Nippon Kayaku Co., Ltd.), Kayase Black G (made by Nippon Kayaku Co., Ltd.), etc. are mentioned. You may use 1 type, or 2 or more types of black pigments.

[2-2] Next, the composition 50 is applied to the gap 33 between the wiring 31 and the wiring 32 as shown in FIG.

  The application method is not particularly limited, and examples thereof include a method using a dispenser such as a dispenser or an inkjet, a method using a spatula such as a squeegee, a method using a printing machine such as a screen printing machine, and the like. . Among these, as shown in FIG. 8B, a method using a discharger is preferably used. According to this method, a necessary amount of the composition 50 can be efficiently applied with high accuracy at a target position. For this reason, the application operation can be performed in a short time while minimizing the amount of the composition 50 used. As a result, the cost and speed of the application work can be reduced.

Thereafter, the applied composition 50 is dried as necessary. Thereby, fixation of the applied composition 50 can be achieved.
Drying may be natural drying or forced drying.

  Although the applied composition 50 depends on its viscosity, as shown in FIG. 9A, the semiconductor ceramic particles 51 are dispersed almost uniformly in the composition 50. In other words, the viscosity of the composition 50 is preferably set as appropriate so that the semiconductor ceramic particles 51 are uniformly dispersed in the composition 50 before coating. Thereby, the applied composition 50 contains the semiconductor ceramic particles 51 at a constant concentration, regardless of the timing of application. As a result, variation in the concentration of the semiconductor ceramic particles 51 can be suppressed.

  Such a viscosity is appropriately set according to the specific gravity difference between the semiconductor ceramic particles 51 and the uncured resin, the viscosity difference, the compatibility, the particle diameter of the semiconductor ceramic particles 51, the temperature, and the like. As an example, the pressure is preferably about 0.1 to 1000 Pa · s, more preferably about 0.5 to 500 Pa · s, still more preferably about 1 to 300 Pa · s, and 2 to 150 Pa · s. Particularly preferred is about s. Thereby, while the storage stability of the composition 50 becomes favorable, the application | coating precision of the apply | coated composition 50 can be improved more.

  If the viscosity is lower than the lower limit, depending on the environment such as the temperature, the shape of the applied composition 50 is likely to be lost, the application accuracy is reduced, or the semiconductor ceramic particles 51 of the applied composition 50 are reduced. There is a risk of variations in concentration. On the other hand, if the viscosity exceeds the upper limit, depending on the environment such as the temperature, the workability of the application work may be reduced, or the application accuracy may be reduced.

  The viscosity is a value measured at 25 ° C. (room temperature) using Toki Sangyo TVE-33H.

[3] Next, the applied composition 50 is heated to cure the resin. Thereby, the protection element 5 including the semiconductor ceramic particles 51 and the cured resin 52 is obtained.

  Although the heating conditions of the composition 50 are suitably set according to the composition etc. of the composition 50, it is preferable that it is 50-200 degreeC, for example, and it is more preferable that it is 70-180 degreeC. The heating time is preferably, for example, 1 to 300 minutes, and more preferably 2 to 120 minutes. Thereby, the resin can be sufficiently cured while suppressing thermal deterioration of the wirings 31 and 32 and the protected circuit 4.

  Note that this step may be performed in multiple steps. That is, after heating under the heating conditions as described above, preferably at a heating temperature of 50 to 200 ° C., more preferably 70 to 180 ° C., preferably 0.1 to 10 hours, more preferably 1 to 4 hours later. You may make it perform a process.

  Here, as the resin in the composition 50, a resin that is once softened in the initial stage when heated in this step and then rises in viscosity again to be cured is preferably used. At the timing of softening, the composition 50 is filled without a gap by the gap 33 between the wiring 31 and the wiring 32, so that the adhesion between the wiring 31, 32 and the protection element 5 is enhanced. As a result, the expression of the varistor characteristics by the semiconductor ceramic particles 51 becomes more prominent, and the varistor characteristics such as the energy resistance of the protective element 5 can be further improved.

  On the other hand, at the timing of softening, the semiconductor ceramic particles 51 easily move in the composition 50. For this reason, the semiconductor ceramic particles 51 are likely to settle based on the specific gravity difference between the semiconductor ceramic particles 51 and the resin. At this time, as shown in FIG. 9A, when the insulating substrate 2 is disposed vertically below the composition 50, the semiconductor ceramic particles 51 settle to the insulating substrate 2 side. As a result, as shown in FIG. 9B, the semiconductor ceramic particles 51 are unevenly distributed in the gap 33 between the wiring 31 and the wiring 32. As a result, as described above, the semiconductor ceramic particles 51 are arranged at a high density in the gap 33, and the varistor characteristics of the protection element 5 can be further improved. Thereby, the overvoltage applied to the protected circuit 4 can be moderated satisfactorily.

  Therefore, in this step, the semiconductor ceramic particles 51 need to settle while the resin is softened. For this purpose, for example, by knowing the thickness of the composition 50, that is, the settling distance and the settling speed of the semiconductor ceramic particles 51, it is possible to know whether or not the settling is completed within the softening time. it can. Moreover, what is necessary is just to prepare the composition 50 so that sedimentation may be in time based on the result.

From the above viewpoint, the density of the constituent material of the semiconductor ceramic particles 51 is preferably 2 g / cm ³ or more and 8 g / cm ³ or less, more preferably 3 g / cm ³ or more and 7 g / cm ³ or less, and 4 g / cm ³ or more 6 g / cm ³ at even more preferably less. By setting the density of the constituent material of the semiconductor ceramic particles 51 within the above range, the semiconductor ceramic particles 51 can be settled at a sufficient sedimentation speed, so that the protective element 5 in which the semiconductor ceramic particles 51 are unevenly distributed can be more reliably obtained. Can be manufactured.

  The density of the constituent material of the semiconductor ceramic particles 51 is not the bulk density of the semiconductor ceramic particles 51 but the density of the constituent material itself.

  The minimum melt (softening) viscosity of the resin is not particularly limited, but is preferably 0.001 to 100 Pa · s, more preferably 0.01 to 50 Pa · s, and more preferably 0.1 to 30 Pa · s. More preferably, it is s. Thereby, when the semiconductor ceramic particle 51 of the particle diameter as mentioned above is used, the sedimentation rate of the semiconductor ceramic particle 51 is not too fast and is not too slow. As a result, the semiconductor ceramic particles 51 can be more unevenly distributed while increasing the manufacturing efficiency of the protection element 5.

  The viscosity can be measured with a viscoelasticity measuring device (Rheo stress RS-10 HAAKE, manufactured by Thermo Fisher Scientific Co., Ltd.) at a heating rate of 10 ° C./min, a frequency of 0.1 Hz, and constant strain-stress detection. it can.

<Electronic equipment>
The protection element of the present invention as described above is mounted on various electronic devices. As described above, the protection element of the present invention has a small space occupancy and a high degree of freedom in arrangement. For this reason, a protective element can be arrange | positioned in a very small space, and it has high affinity also for the densification of the wiring of a mounting substrate. Therefore, the electronic device of the present invention is small and highly reliable.

  As an electronic device of the present invention, for example, a mobile phone, a smartphone, a tablet terminal, a game machine, a personal computer, a consumer device such as a TV, a server, a router device, an industrial device such as a robot, an automobile, an aircraft, a train, Examples include equipment mounted on a moving body such as a ship.

  As mentioned above, although this invention was demonstrated based on suitable embodiment, this invention is not limited to these.

  For example, the manufacturing method of the protection element of the present invention may be one in which an arbitrary step is added to the above-described embodiment, or the order of the steps in the above-described embodiment may be changed. .

  Moreover, the protection element and the mounting substrate of the present invention may be those obtained by adding arbitrary elements to the above-described embodiment.

Hereinafter, specific examples of the present invention will be described.
1. Fabrication of mounting substrate (Sample No. 1)
First, a mixture of bisphenol F type epoxy resin and bisphenol A type epoxy resin (liquid, manufactured by DIC Corporation, EPICLON EXA-830LVP) was prepared.

  Moreover, phenol novolak resin (liquid, Meiwa Kasei Co., Ltd. make, MEH-8000H) was prepared as a hardening | curing agent.

  Further, 3-glycidyloxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., KBM-403) was prepared as a silane coupling agent.

  Moreover, the compound represented by following formula (a) was prepared as a hardening accelerator. In the following formula (a), Ph represents a phenyl group.

Further, semiconductor ceramic particles (manufactured by Ceraon Co., Ltd., micro varistor, average particle size 48 μm) were prepared.
The mixing ratio of these raw materials is as shown in Table 1.

Next, these raw materials were kneaded with a planetary mixer to prepare a resin composition.
Subsequently, as a substrate including the electric circuit shown in FIG. 4, an FR-4 substrate having copper wiring on the surface was prepared. In addition, a light emitting diode element was placed as a protected circuit. The wiring thickness was 35 μm.

  Next, the prepared resin composition for forming a protective element was applied so as to fill the gap between the wirings, and leveled using a squeegee. A dispenser was used for this application.

  Next, the applied composition was dried at 100 ° C. for 2 minutes in a state where the FR-4 substrate was positioned vertically below when the resin composition was used as a reference, and then further at 150 ° C. for 60 minutes. The curable resin was cured by heating. As a result, a protective element having a maximum thickness of 0.1 mm was obtained and a mounting substrate was obtained.

(Sample No. 2-9)
Except for changing the raw materials and the blending ratio thereof as shown in Table 1, sample No. A protective element was obtained in the same manner as in Example 1, and a mounting substrate was obtained. In some samples, semiconductor ceramic particles having different particle diameters were used.
The raw materials shown in Table 1 are as follows.

・ Vinyl group-containing silicone resin (liquid, Momentive Performance Materials Japan, IVSM-4500 (A))
・ Hydrogen atom-containing silicone resin (Liquid, Momentive Performance Materials Japan Ltd., IVSM-4500 (B))
・ Hydroxy group-containing silicone resin (solid, manufactured by Asahi Kasei Wacker Silicone Co., Ltd., SILRES MK)
・ Epoxy resin (DICIC, EPICLON EXA-830LVP)
・ Epoxy resin (Shikoku Kasei Kogyo, MA-DGIC)
・ Curing agent (Maywa Kasei, MEH-8000H)
・ Curing agent (manufactured by Shin Nippon Chemical Co., Ltd., MH-700)
・ Olefin resin (Sumitomo Bakelite, 5-decylnorbornene resin)

Here, the 5-decylnorbornene resin was synthesized by the method shown below.
First, 430 g of ethyl acetate, 890 g of cyclohexane and 223 g of 5-decylnorbornene (0.95 mol) were introduced into a sufficiently dried reaction vessel. Dry nitrogen was passed through the system at 40 ° C. for 30 minutes to remove dissolved oxygen.

Subsequently, 1.33 g (2.75 × 10 ⁻⁴ mol) of bis (toluene) bis (perfluorophenyl) nickel dissolved in 12 g of ethyl acetate was added to the reaction system. The system was heated from 40 ° C. to 55 ° C. over 15 minutes, and then the system was stirred for 3 hours while maintaining the temperature.

  Next, a solution was prepared by dissolving 26 g of glacial acetic acid in 1500 g of pure water to which 49 g of hydrogen peroxide having a concentration of 30% by mass was added. And the solution prepared to said system was added, and after stirring at 50 degreeC for 5 hours, stirring was stopped and the isolate | separated water layer was removed.

  Next, the organic layer remaining after the removal of the aqueous layer was washed with 220 g of methanol and 200 g of isopropyl alcohol.

  Next, 510 g of cyclohexane and 290 g of ethyl acetate were added to the washed organic layer to uniformly dissolve the system.

  Next, a solvent consisting of 156 g of methanol and 167 g of isopropyl alcohol was added to the obtained solution, followed by stirring, and a process for removing the added solvent. The organic layer was washed by repeating this treatment twice.

  Next, 180 ml of cyclohexane was added to the washed organic layer to uniformly dissolve the system, and 670 g of mesitylene was further added. Then, 543 g (35% mesitylene solution) of 5-decylnorbornene polymer was obtained by evaporating and removing cyclohexane with a rotary evaporator under reduced pressure.

  The synthesized 5-decylnorbornene polymer was measured to have a weight average molecular weight of 75,300 by gel permeation chromatography (GPC).

  In addition, about the raw material solid at normal temperature, it mixed with the liquid raw material at normal temperature, and it was made to use for an application | coating operation | work after heat-melting solid raw material after that.

(Sample No. 10)
First, as the resin composition, a raw material and a mixture ratio thereof changed as shown in Table 1 were prepared.

Next, sample no. The resin composition was applied in the same manner as in the method of manufacturing the mounting substrate 1 and leveled using a squeegee, and then the top and bottom were inverted. Then, the applied composition was dried and cured in a state where the FR-4 substrate was held vertically above when the resin composition was used as a reference. Thereby, a protective element was obtained and a mounting substrate was obtained.
The raw materials shown in Table 1 are as follows.

・ Vinyl group-containing silicone resin (liquid, manufactured by Shin-Etsu Chemical Co., Ltd., KE-106)
・ Hydrogen atom-containing silicone resin (liquid, manufactured by Shin-Etsu Chemical Co., Ltd., CAT-RG)

(Sample No. 11)
Except for changing the raw materials and the blending ratio thereof as shown in Table 1, sample No. A protective element was obtained in the same manner as in No. 10, and a mounting substrate was obtained.

(Sample No. 12)
After applying the resin composition using the dispenser and then omitting the leveling operation using the squeegee, the sample No. A protective element was obtained in the same manner as in Example 1, and a mounting substrate was obtained.
In addition, Table 2 shows the raw materials used and their blending ratios.

  Moreover, when the upper surface of the protective element was observed with an optical microscope, it was recognized that it had a curved convex surface.

(Sample No. 13)
First, sample no. In the same manner as in the case of 1, a resin composition was prepared. The raw materials of the resin composition and the blending ratio are as shown in Table 2.

  Next, as a substrate including the electric circuit shown in FIG. 7, an FR-4 substrate having a copper wiring and a solder resist film provided on the surface was prepared. Note that an opening was provided in the solder resist film so that the adjacent copper wiring and the space between the wirings were exposed. In addition, a light emitting diode element was placed as a protected circuit. The wiring thickness was 35 μm.

  Next, the prepared resin composition was applied so as to fill the opening of the solder resist film. A dispenser was used for this application.

  Next, sample no. In the same manner as in case 1, the resin composition was cured to obtain a protective element having a maximum thickness of 0.1 mm and a mounting substrate.

  The thickness of the solder resist film was 30 μm, and the length L1 of the portion where the protective element and the solder resist film overlapped was 60 to 1500 μm.

(Sample No. 14)
Sample No. 1 except that the length L1 is 30 to 2000 μm. In the same manner as in Example 13, a protective element was obtained and a mounting substrate was obtained.

(Sample No. 15)
Sample No. 1 except that the length L1 is 15 to 3000 μm. In the same manner as in Example 13, a protective element was obtained and a mounting substrate was obtained.

(Sample No. 16)
Sample No. except that the length L1 is 0 to 3000 μm. In the same manner as in Example 13, a protective element was obtained and a mounting substrate was obtained.

2. Evaluation of Resin Composition Sample No. About the resin composition used in the case of manufacture of the mounting board | substrate in 1-11, the viscosity at room temperature and the minimum melt viscosity when heated to 150 degreeC and the viscosity in 150 degreeC were measured, respectively. The viscosity was measured using a viscoelasticity measuring apparatus (Rheo stress RS-10 HAAKE, manufactured by Thermo Fisher Scientific Co., Ltd.) under the conditions of a heating rate of 10 ° C./min and a frequency of 0.1 Hz. -It carried out by the measuring method by stress detection. The measurement results are shown in Table 1.

3. Evaluation of mounted substrate 3.1 Evaluation of sedimentation degree A plurality of mounting substrates were manufactured, and one of them was cut to observe the cross section of the protective element. When the cut surface was observed with a scanning electron microscope, it was found that the semiconductor ceramic particles were unevenly distributed on the FR-4 substrate side. Therefore, an intermediate line of the protective element is obtained from the observation image of the cut surface, and when the area ratio (volume ratio) of the semiconductor ceramic particles on the FR-4 substrate side from the intermediate line is 1, FR- The relative value of the area ratio (volume ratio) of the semiconductor ceramic particles on the side far from the four substrates (opposite side) was calculated. The calculation results are shown in Tables 1 and 2.

  In the calculation, binarized image processing was performed on the observed image so that the outline of the ceramic particles became clear.

3.2 Evaluation of electrical characteristics (initial varistor characteristics) Using a pA meter / DC VOLTAGSOURCE SOURCE 4140B (manufactured by Agilent Technologies), a boosting speed of 0.5 V / sec from 0 V to 100 V between adjacent wirings on the mounting board The value of the current that flowed when the voltage was applied was measured. Based on the results of the current / voltage characteristics thus obtained, a graph plotted with a logarithmic axis was created as shown in FIG. Next, a non-linear coefficient was calculated from the obtained graph. And each sample No. About the varistor characteristic which the hardened | cured material of this resin composition shows, it evaluated on the following references | standards from the value of the calculated nonlinear coefficient.

A: The nonlinear coefficient is 20 or more.
A: The nonlinear coefficient is 10 or more and less than 20.
Δ: The nonlinear coefficient is 2 or more and less than 10.
X: The non-linear coefficient was less than 2, and no varistor voltage was developed.
The evaluation results are shown in Tables 1 and 2.

3.3 Evaluation of weather resistance (salt water spray test) First, sample no. 13 to 16 mounting boards were put into a salt spray test apparatus. And the aqueous solution containing 0.5 mass% sodium chloride and 0.2% hydrogen peroxide was prepared as a salt solution, and this was sprayed with respect to the mounting substrate for 96 hours. The temperature in the spray chamber was 35 ° C.

  Next, 20 mounting substrates after 24 hours and 20 mounting substrates after 96 hours were cut, respectively, and the presence or absence of rusting in the copper wiring near the protective element was observed with an optical microscope. And the observation result was evaluated in light of the following evaluation criteria.

<Evaluation criteria for rusting>
A: The number of rusting is 0. B: The number of rusting is 1 or 2. B: The number of rusting is 3-5. X: The number of rusting is 6 or more. Shown in

3.4 Evaluation of ESD resistance First, five discharges were performed between adjacent circuits on the mounting substrate. The discharge conditions were a discharge capacity of 100 pF and a discharge resistance of 1500Ω. Moreover, the static electricity tester (Noise Research Institute make, ESS-6008) was used for the discharge test.

  Next, a voltage was applied from 0 V to 100 V at a boosting rate of 0.5 V / second between adjacent circuits using pA meter / DC VOLTAG SOURCE 4140B (manufactured by Agilent Technologies). Then, the current value flowing between the circuits when a voltage of 5 V was applied was measured, and the obtained measured value was evaluated in light of the following evaluation criteria.

<Evaluation criteria for ESD resistance>
○: Current value is less than 1.0 × 10 ⁻⁶ A Δ: Current value is 1.0 × 10 ⁻⁶ A or more and less than 1.0 × 10 ⁻³ A ×: Current value is 1.0 × 10 ⁻³ A or more The above evaluation results are shown in Tables 1 and 2.

  As is clear from Tables 1 and 2, the varistor characteristics of the protective element could be confirmed in any of the mounting substrates of the examples. Furthermore, the adhesion of the protective element was also good from the results of cross-sectional observation and the like. From these facts, it became clear that according to the present invention, the protective element can be easily manufactured at a target position with a high degree of freedom in arrangement.

  Furthermore, it was recognized that the weather resistance of the mounting substrate can be improved by arranging the protective element so as to overlap the solder resist film.

DESCRIPTION OF SYMBOLS 1 Mounting board 2 Insulating board 4 Protected circuit 5 Protection element 6 Power supply 7 Solder resist film 13F Test piece 31 Wiring 32 Wiring 33 Gap 41 Counter electrode 42 Main electrode 43 Guard electrode 50 Composition 51 Semiconductor ceramic particle 52 Hardened material 71 Opening 311 Trunk line 312 Branch line 315 Branch point 321 Trunk line 322 Branch line 325 Branch point 511 Grain boundary part 512 Crystal part Z ₀ Line impedance

Claims (11)

A protection element that is provided across the conductive parts that are spaced apart from each other on the surface of the base part, and exhibits non-linearity in which the voltage-current characteristic does not follow Ohm's law,
A semiconductor ceramic particle including a grain boundary part and a plurality of crystal parts separated by the grain boundary part, and a cured product of a resin having a relative dielectric constant of 4 or less,
A protective element, wherein the semiconductor ceramic particles are unevenly distributed on the base side. A protection element that is provided across the conductive parts that are spaced apart from each other on the surface of the base part, and exhibits non-linearity in which the voltage-current characteristic does not follow Ohm's law,
Semiconductor ceramic particles including a grain boundary part and a plurality of crystal parts separated by the grain boundary part, and a cured product of a curable resin,
A protective element, wherein the semiconductor ceramic particles are unevenly distributed on the base side.   The volume fraction of the semiconductor ceramic particles on the side opposite to the base is 0 or more and 0.90 or less, where the volume fraction of the semiconductor ceramic particles on the base side of the protective element is 1. Item 3. The protective element according to Item 1 or 2.   The protective element according to any one of claims 1 to 3, wherein the resin includes an epoxy resin, a silicone resin, an olefin resin, or a benzocyclobutene resin.   The protective element according to claim 1, wherein a surface of the protective element includes a curved convex surface at least partially. Applying a composition comprising semiconductor ceramic particles including a grain boundary part and a plurality of crystal parts separated by the grain boundary part, and an uncured curable resin;
Curing the curable resin in the composition to form a protective element exhibiting non-linearity in which voltage-current characteristics do not follow Ohm's law;
The manufacturing method of the protection element characterized by having. Provided before the step of applying the composition, a base, a plurality of conductive parts provided on the surface of the base and spaced apart from each other, and an electronic component electrically connected to the conductive part are arranged Further comprising the step of preparing an insulating member,
The method for manufacturing a protection element according to claim 6, wherein in the step of applying the composition, the composition is applied to a region straddling the conductive portions.   The method for manufacturing a protection element according to claim 7, wherein the composition is applied by discharging the composition toward the region. The base,
A plurality of conductive portions provided on the surface of the base and spaced apart from each other;
An electronic component electrically connected to the conductive portion;
The semiconductor ceramic particles, which are provided across the conductive parts and include a grain boundary part and a plurality of crystal parts separated by the grain boundary part, and a cured product of a curable resin, have a voltage-current characteristic. A protective element exhibiting non-linearity that does not follow Ohm's law;
Have
In the protective element, the semiconductor ceramic particles are unevenly distributed on the base side. Furthermore, a solder resist film is provided so as to cover a part on the surface of the conductive portion, and has an opening corresponding to a region including a gap between the conductive portions,
The mounting substrate according to claim 9, wherein the protective element is provided so as to protrude from the opening onto the surface of the solder resist film.   An electronic apparatus comprising the protective element according to claim 1.

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