JPH0766563A - Multilayer circuit board with built-in capacitor - Google Patents

Abstract

(57) [Summary] [Object] To provide a multilayer circuit board with a built-in capacitor, which has a small absolute value of the dielectric constant temperature characteristics of the board body and is excellent in board strength. According to the present invention, a plurality of dielectric layers 1a, 1b, ... Made of a glass component and an inorganic filler are laminated, and a predetermined wiring pattern 2 and a capacitor made of a gold-based, silver-based or copper-based conductive material are provided inside thereof. In the multilayer capacitor built-in circuit board 10 on which the generation pattern 3 is formed and the thick film resistor film 6 is formed on the surface thereof, the inorganic filler is alumina, a perovskite crystal structure having a particle size of 2 to 10 μm, and a negative It includes a dielectric material having temperature characteristics.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a layered circuit board with a built-in capacitor, which is capable of correcting the capacity-temperature characteristic of a capacitor formed inside thereof, to obtain a capacitor having little temperature dependence, and having a strong capacity.

[0002]

2. Description of the Related Art Conventionally, an insulating layer composed of an inorganic filler such as alumina and a glass component has been used to obtain a low temperature (about 90%).
A multilayer circuit board capable of firing (around 0 ° C.) has already been used. This low-temperature sinterable multilayer circuit board can use a low resistance material such as gold, silver or copper for the internal wiring pattern, and can realize an electronic circuit or a high frequency circuit with a high signal propagation speed.

Further, a capacitance generating pattern (insulation (dielectric)) is formed on such a multilayer circuit board together with an internal wiring pattern.
There is proposed a multilayer circuit board with a built-in capacitor in which a pair of wiring patterns, which face each other with a layer sandwiched therebetween, is formed and a capacitor is built therein.

In this case, it cannot be used, for example, in an oscillator or the like having a resonant circuit in a multilayer circuit board with a built-in capacitor unless the temperature characteristics of the dielectric constant of the substrate composition material are sufficiently taken into consideration. This is because the glass component, which is the material constituting the dielectric layer, is, for example, borosilicate glass or alumino acid glass, and the inorganic filler is alumina, but these materials have positive dielectric constant temperature characteristics, This is because the substrate body has a positive dielectric constant temperature characteristic, and the capacitance value greatly changes due to temperature changes.

In order to correct the absolute value of the dielectric constant temperature characteristic of such a substrate material to a small value, it has been conventionally proposed in JP-A-4-82297 to use titania together with alumina as an inorganic filler. However, titania has a temperature coefficient of permittivity of −910 ppm / ° C., which is insufficient to correct the temperature coefficient of permittivity of the entire substrate material. This is because titania easily reacts with the substrate material and wiring pattern of alumina or glass components, especially on the surface of the thick film resistor film, which lowers the strength of the substrate or changes the characteristics of the thick film resistor film. This is because there is a possibility that it will be caused, and the addition amount thereof is limited.

As an inorganic filler added together with alumina for correcting the dielectric constant temperature characteristics of substrate materials other than titania, a substance having a perovskite crystal structure and a high Curie point at room temperature, such as strontium stannate (dielectric Rate-3720 ppm / ° C.), strontium titanate (-3360 ppm / ° C.), calcium titanate (-1620 ppm / ° C.), and the like.

[0007]

However, when the above-mentioned substance having a perovskite crystal structure is used as an inorganic filler to be added together with alumina, it will form a solid solution with the glass component during firing and the crystal structure will collapse. However, there is a problem that the effect of correcting the temperature characteristic of the dielectric constant is reduced.

As a result of various experiments, the inventors of the present invention have controlled the particle size of the inorganic filler of the substance having a perovskite crystal structure, for example, by increasing the particle size to reduce the contact area with the glass component, It was found that the area in which a solid solution reaction occurs can be reduced. That is, it is possible to reduce the solid solution reaction and maintain a sufficient correction action of the dielectric constant temperature characteristic. On the other hand, if the particle size is too large, the denseness of the substrate after firing will be poor and the strength and moisture resistance will be reduced.

The present invention is based on the above findings, and an object thereof is to optimize the particle size of the inorganic filler of a substance having a perovskite crystal structure to sufficiently correct the temperature coefficient of dielectric constant of the substrate. An object of the present invention is to provide a multi-layer circuit board with a built-in capacitor that can be manufactured and has high board strength.

[0010]

According to the present invention, a plurality of dielectric layers composed of a glass component and an inorganic filler are laminated, and an internal wiring pattern made of a gold-based, silver-based or copper-based conductive material and a capacitance generation are formed inside. In the multilayered circuit board with a built-in capacitor having a pattern, the inorganic filler has a perovskite crystal structure and has a negative temperature characteristic of dielectric constant.
A multilayer circuit board with a built-in capacitor including a dielectric material of 10 μm.

Preferably, the dielectric material is a strontium titanate-embedded multilayer circuit board.

[0012]

As described above, according to the present invention, since the material of the insulating (dielectric) layer is composed of the glass component and the inorganic filler, it can be sintered at a relatively low temperature (up to 1000 ° C). A metal material such as gold, silver, or copper having a low specific resistance can be used for the internal wiring pattern and the capacitance generation pattern.

A dielectric material having a perovskite crystal structure and a negative dielectric constant temperature characteristic (hereinafter, simply referred to as a negative temperature characteristic material) is used as an inorganic filler for correcting the dielectric constant temperature characteristic used with an alumina filler, for example. Therefore, the absolute value of the temperature characteristic of the permittivity of the entire dielectric layer can be corrected to be extremely small, for example ± 60 ppm / ° C, and a stable capacitance characteristic can be obtained even if the capacitance generation pattern is built in. Type multi-layer circuit board.

In the present invention, the particle diameter of the inorganic filler, which is a negative temperature characteristic material, is 2 to 10 μm. That is, by setting the particle size to 2 μm or more, even if sintering is performed at a low temperature (for example, 900 ° C.) with alumina or a glass component, the solid solution reaction with the glass component can be suppressed during the sintering reaction, and the perovskite structure can be obtained. Since it can be sufficiently maintained, the above-mentioned correction action can be sufficiently maintained, and the dielectric constant temperature characteristic can be kept within ± 60 ppm as described above.

Further, since the grain size is 10 μm or less, the whole substrate after firing can be densified and the strength of the substrate can be maintained at a predetermined value or more. Here, the particle size is 10μ
If it exceeds m, the strength of the substrate is significantly deteriorated, and in the manufacturing process, when it is slurried with a solvent such as a glass frit and an alumina filler, a sedimentation phenomenon occurs or homogeneous dispersion cannot occur.

In particular, if strontium titanate is used as the negative temperature characteristic material, high substrate strength can be achieved.

Further, as compared with a substrate using titania, the titania component is not deposited on the substrate surface, and even if a thick film resistor film is formed on the surface, the resistance characteristic is not significantly changed. .

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A capacitor built-in multilayer circuit board of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows a cross-sectional structure of a capacitor-embedded multilayer circuit board of the present invention. In the figure, 10 is a multilayer circuit board with a built-in capacitor, 1 is a plurality of dielectric layers 1a,
1b is a laminated substrate body, and 2 is a dielectric layer 1
a is a predetermined internal wiring pattern formed between a, 1b ..., 3 is a capacitance generating pattern formed between dielectric layers 1a, 1b ..., 4 is a via-hole conductor, 5
Is a surface wiring pattern, and 6 is a thick film resistor film.

The substrate body 1 comprises a plurality of glass-ceramic dielectric layers 1a, 1b.
A predetermined internal wiring pattern 2 made of a gold-based, silver-based, or copper-based conductor, a capacitance generation pattern 3, and a via-hole conductor penetrating the dielectric layers 1a, 1b. 4 and.

As a result, a part of a circuit having a predetermined capacitance is formed in the substrate body 1 by the capacitance generating patterns 3 which face each other with the dielectric layers, for example, 1c and 1d interposed therebetween.

A predetermined surface wiring pattern 5 made of a gold-based, silver-based, or copper-based conductor and a thick film resistor film 6 are formed on the main surface of the substrate body 1, and these are connected via a via-hole conductor 4. , Is electrically connected to the internal wiring pattern 2 and the capacitance generation pattern 3, and a predetermined circuit is achieved as a whole. Although not shown in the drawing, a protective film is formed on the surface, and an IC chip, a chip electronic component, etc. are mounted as needed.

Here, the capacitance formed inside the substrate body 1 is generated, for example, between the capacitance generating patterns 3 having a predetermined facing area and arranged so as to sandwich the dielectric layer 1c in the figure. Further, a predetermined capacitance is generated between the capacitance generation patterns 3 arranged so as to sandwich the dielectric layer 1d.

The dielectric layers 1a, 1b ... Are formed by sintering a glass component and an inorganic filler. The glass component is crystallized glass, amorphous glass, or the like, and the inorganic filler includes at least powder of a negative temperature characteristic material,
Other examples include alumina powder. In addition, as the inorganic filler negative temperature characteristic material, strontium titanate (-3360 ppm / ° C), strontium stannate (-3720 ppm / ° C), calcium titanate (-1
620 ppm / ° C.). Further, examples of the glass component include low melting glass such as borosilicate glass and aluminosilicate glass.

The composition ratio of the glass component is 40 to 90% by weight.
The composition ratio of the inorganic filler composed of the alumina powder and the powder of the negative temperature characteristic material is 10 to 60% by weight.
When the content of the inorganic filler is less than 10% by weight, the amount of the material such as alumina powder that is effective for the strength of the substrate decreases relatively, so that the strength of the sintered substrate body 1 decreases.
On the other hand, when it exceeds 60% by weight, the glass component is relatively insufficient in the substrate body 1 after sintering, so that a dense circuit substrate cannot be achieved. The composition ratio of the glass component is preferably 30.
Is about 50% by weight, and the balance is a glass component.

In this way, the particle size of the negative temperature characteristic material is set to 2-1.
It is important to set it to 0 μm. Particle size 2 to 10μ
By setting m, it is possible to obtain a homogeneously mixed slurry without causing a sedimentation phenomenon even when the substrate material is made into a slurry state. Further, even when sintered at a temperature up to about 1050 ° C., a very stable perovskite crystal structure can be maintained, the effect of correcting the dielectric constant temperature characteristic of the substrate 1 sufficiently appears, and the temperature characteristic is kept within ± 60 ppm. be able to.

As a result, even if the capacitance generating pattern 3 is formed, a stable capacitance component whose capacitance does not largely depend on temperature can be easily formed. Further, the relative permittivity can be set to 8.0 or more, and a capacitance having a sufficient capacitance value can be achieved even if the facing area of the capacitance generating pattern 3 is reduced.

In particular, when strontium titanate is used as the above-mentioned dielectric material, the flexural strength of the substrate is superior to other dielectric materials.

Further, the characteristics of the conductor material forming the internal wiring pattern 2 and the capacitance generating pattern 3 formed between the dielectric layers 1a, 1b ... Are not affected.

Further, the strength of the substrate body 1 becomes a practical value by using it together with the alumina powder of the inorganic filler.

Note that ruthenium oxide on the surface of the substrate body 1
Even if the thick film resistor film 6 made of lanthanum hexaboride, tin oxide or the like is formed, the thick film resistor film 6 is never given semiconductor conductivity and the temperature characteristic is not shifted to the negative side at all.

Among the above-mentioned negative temperature characteristic materials, the reason why strontium titanate is preferable is that the strength of the substrate body 1 is sufficiently obtained as described above, the compensating action of the temperature characteristic is remarkably exhibited, and the firing condition is This is because it is relatively eased.

For example, calcium titanate has a smaller ionic radius than strontium titanate,
The reaction with the glass component becomes remarkable, the crystal structure is easily broken, and the particle size is 10 μm in order to obtain a sufficient effect of correcting the dielectric constant.
It should be close to m.

Further, strontium stannate is difficult to maintain the perovskite structure after sintering, and it is necessary to pay sufficient attention to the firing conditions.

As the dielectric layers 1a, 1b ... In addition to the glass component, the alumina powder and the powder of the negative temperature characteristic material,
An oxidizing agent or the like may be added if necessary.

Next, a method of manufacturing the capacitor built-in type multilayer circuit board of the present invention will be described.

First, the substrate composition (dielectric layers 1a, 1b)
...) which is a crystallized or amorphous low-melting-point glass frit, alumina powder, a negative temperature characteristic material, for example, strontium titanate powder, an organic binder (for example, polymethacrylate resin), and a plasticizer (for example, dibutyl). Phthalate), a solvent (for example, methyl ethyl ketone), and another additive (for example, an antifoaming agent) are mixed at a predetermined ratio, and this is kneaded for about 24 to 72 hours using a ball mill to prepare a homogeneous slurry. After defoaming the slurry, the slurry is subjected to a known method such as doctor blade method at 50-30.
A green sheet having a thickness of about 0 μm is formed.

Next, a hole to be the via-hole conductor 4 is punched on the surface of the obtained green sheet to fill the via-hole conductor 4 and print the internal wiring pattern 2 and the capacitance generating pattern 3. The filling of the via-hole conductor 4 may be performed after printing the internal wiring pattern 2 and the capacitance generating pattern 3.

Internal wiring pattern 2, capacitance generation pattern 3
As the conductor paste for use, a conductor paste containing as a main component at least one metal selected from gold, silver, copper and alloys thereof is used. The green sheets on which the internal wiring pattern 2, the capacitance generating pattern 3 and the via-hole conductor 4 are formed are sequentially laminated in consideration of the layer structure of the dielectric layers 1a, 1b ... A laminated body to be the substrate body 1 is formed.

The laminated body thus obtained is fired. First, in the first step, the organic substances contained in the laminate are removed at a temperature equal to or lower than the softening point of the glass component, for example, around 500 ° C. In the next step, the dielectric layers 1a, 1b, ... Made of glass component, alumina powder, and strontium titanate.
And the internal wiring pattern 2, the capacitance generation pattern 3, and the via-hole conductor 4 are integrally sintered. The firing temperature is set to the glass components of the dielectric layers 1a, 1b ... Or the internal wiring pattern 2
Is determined by the melting point of the conductor material such as
It is carried out at a temperature of 1050 ° C. The firing atmosphere is determined by the conductor material of the internal wiring pattern 2. Thereby, the sintered substrate body 1 is achieved.

A surface wiring pattern 5 and a thick film resistor film 6 are formed on the obtained substrate body 1.

The thick-film resistor film 6 is determined by the baking atmosphere of the surface wiring pattern 5 and the like. However, when baking in a non-oxidizing atmosphere, the resistance mainly composed of lanthanum hexaboride, tin oxide, etc. It is formed using body paste.
When firing in an oxidizing atmosphere, a resistor paste containing ruthenium oxide as a main component is used.

The surface wiring pattern 5 may be made of silver-based conductor (silver or silver alloy) or copper-based (copper or copper alloy), but copper-based material is preferable in consideration of migration resistance. .

(Experimental Example) As a glass frit, 51 mol% of silicon oxide, 19 mol% of aluminum oxide, 19 mol% of magnesium oxide, 8 mol% of zinc oxide, and 3 mol% of boron oxide (boric acid corresponding thereto) were mixed, After melting at about 1600 ° C., it was poured into water and rapidly cooled to obtain glass. The obtained glass was put into an alumina pot together with alumina balls, wet-ground and dried. As a result, a crystallized glass frit having an average particle size of 2 to 3 μm was obtained.

Next, in the proportions shown in Table 1, crystallized glass frit, alumina powder having a particle size of 2 μm and / or particle size of 3.9.
μm or 1.6 μm particle size strontium titanate powder was mixed. The mixture was put together with alumina balls in an alumina pot, mixed by a ball mill and then dried to obtain a composition for a built-in capacity type multilayer circuit board.

To 1000 g of the obtained composition for substrates, 100 g of acrylic resin, 70 g of plasticizer and 400 g of toluene were added to prepare a slurry, and this slurry was subjected to vacuum defoaming treatment.

Next, using the slurry, a green sheet having a thickness of 200 μm was prepared by the doctor blade method. Then, 10 green sheets were laminated and hot pressed, and the obtained laminate was fired at 870 ° C. for 1 hour to prepare a multilayer substrate body.

Indium-gallium conductor films were formed on both surfaces of the obtained substrate body, and in accordance with JIS 2141,
The dielectric constant was measured at 1 MHz with a Q meter.

As the evaluation in Table 1, the dielectric constant temperature characteristics are within ± 60 ppm in the practical temperature range of −30 to 80 ° C., and the bending strength of the substrate is 15 kgf / cm ² which is the practical strength. The above is regarded as a good product.

[0049]

[Table 1]

In Experimental Examples 1 and 2 (adding strontium titanate having a particle size of 1.6 μm), the relative dielectric constant exceeds 8.0, and the dielectric constant temperature characteristics also contribute to the formation of capacitance inside the substrate body 1. ± 60ppm / which is a practical range
Since the temperature becomes less than or equal to ℃, the bending strength can be ensured to be more than the strength suitable for practical use.

In Comparative Example 1 (no addition of strontium titanate), the relative dielectric constant was as small as 6.5, and the temperature characteristic of the dielectric constant was 130 ppm / ° C., which was large on the plus side.

In Comparative Example 2 (addition of strontium titanate having a particle size of 1.6 μm), the relative dielectric constant was 7.0, which was slightly improved as compared with Comparative Example 1, but the dielectric constant-temperature characteristic. Is 78 to 90 ppm / ° C., which is still large on the plus side.

Here, the composition is the same as in Example 1, but since the particle size of strontium titanate is less than 2.0 μm, a part of the perovskite crystal structure collapses during sintering, and in particular, The effect of compensating for the temperature characteristics will not fully appear.

In Comparative Example 3 (without addition of alumina), the relative dielectric constant was 8.2, but the dielectric constant temperature characteristic was 25.
67 ppm / ° C. at -80 ° C., which is slightly large, and the bending strength is less than the practical strength of 15 kgf / cm ² . Also in this case, the particle size of strontium titanate is 2
Since it is less than μm, the perovskite crystal structure is partially collapsed, so that the temperature characteristic is ± 60 ppm / ° C. without adding alumina powder having a positive temperature characteristic.
Can't be within.

As can be seen from the above experimental results, as shown in Examples 1 and 2, a dielectric material having a perovskite crystal structure having a grain size of 2 μm or more and having a negative temperature characteristic was used.
By using it as an inorganic filler together with the alumina powder, the temperature characteristics of the dielectric constant of the dielectric layers 1a, 1b ...
Since it is 60 ppm / ° C., even if the capacitance generating pattern 3 is formed inside the substrate body to obtain a predetermined capacitance,
The capacity can maintain a stable capacity even when the ambient temperature changes.

Further, since the relative permittivity can be increased more than ever before, a sufficient value of capacitance can be obtained even if the area of the capacitance generating pattern 3 is reduced.
Furthermore, the microstrip line pattern 7 shown in FIG.
Even when the substrate is formed inside the substrate body 1, a miniaturized line pattern 7 is achieved, and by further controlling the compounding amount of the dielectric material according to the wavelength shortening rate, the microstrip line can be further minimized. Can be made.

Further, the negative temperature characteristic material has no adverse effect on the internal wiring pattern 2, the capacitance generating pattern 3, the via hole conductor 4 and the surface wiring pattern 5, the thick film resistance film 6, etc. of the substrate body 1 at all. For example, the resistance temperature characteristic of the thick film resistor film 6 on the surface of the substrate body 1 is never changed.

In the above experiment, strontium titanate was used as the dielectric material, but other similar dielectric materials such as strontium stannate, calcium titanate, etc. have been mentioned above. Since the perovskite crystal structure of these materials is more likely to be collapsed than that of strontium titanate, it is important to increase the particle size so as to approach 10 μm in the range of 2 to 10 μm.

In the above-mentioned embodiment, the substrate main body 1 having the capacitance generating pattern 3 and the microstrip line pattern 7 formed therein is exemplified, but other coil patterns may be provided inside the substrate main body 1 or on the surface of the substrate main body 1. It can be widely used in various circuit networks, such as forming an LC resonance circuit with a capacitance component formed inside.

[0060]

As described above, according to the present invention, it is fired at a low temperature and used as an internal wiring pattern and a capacitance generation pattern.
A multilayer circuit board with a built-in capacitor, which comprises a metal material such as gold, silver, or copper having a small specific resistance, wherein a dielectric layer constituting the board body has a glass component, an alumina component, and a particle size of 2 to 2
Since it is configured to include a negative temperature characteristic material of 10 μm and the temperature characteristic of the substrate body can be kept within ± 60 ppm, it is possible to form a capacitance generation pattern in the substrate body and form a stable capacitance. .

Furthermore, since the above-mentioned negative temperature characteristic material can maintain a stable crystal structure even after sintering, it is possible to satisfactorily correct the dielectric constant temperature characteristics of the substrate, and It does not affect the resistance temperature characteristics.

In particular, if strontium titanate is used as the dielectric material, it is effective for maintaining the perovskite crystal structure, and the grain size can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing a sectional structure of a multilayer circuit board with a built-in capacitor according to the present invention.

[Explanation of symbols]

 10- ・ Multilayer circuit board with built-in capacitor 1- ・ Board body 1a, 1b ・ ・ Dielectric layer 2 ・ ・ Internal wiring pattern 3 ・ ・ Capacity generation pattern 4 ・ ・ Via hole conductor 5 ・ ・ ・ ・ ・ ・ Surface wiring pattern 6 ・ ・ ・ ・ Thick film resistor film 7 ・ ・ ・ ・ Microstrip line pattern

Claims (2)

[Claims] 1. A capacitance built-in type in which a plurality of dielectric layers made of a glass component and an inorganic filler are laminated and an internal wiring pattern and a capacitance generation pattern made of a gold-based, silver-based or copper-based conductor material are arranged inside. A multilayer circuit board, wherein the inorganic filler contains a dielectric material having a perovskite crystal structure and a particle diameter of 2 to 10 μm having a negative temperature characteristic of dielectric constant. 2. The multi-layer circuit board with a built-in scale according to claim 1, wherein the dielectric material having the perovskite crystal structure and a negative dielectric constant temperature characteristic is strontium titanate.