JPH03250570A - Conductive connection method - Google Patents

Abstract

PURPOSE:To connect each pair of mating connection terminals by electroconductive particulate by mixing particulate for electric continuity with an insulative adhesive to constitute a bond agent for continuity, interposing it between No.1 and No.2 connection terminals oppositely situated, and performing joining by hot press. CONSTITUTION:An Au plating film 2 is applied to the surface of resin particulate 1, and insulative particulate 4 is attached and melted to cause covering with an insulative film 5, and thus particles 6 for electric continuity are prepared. These particles 6 are put in mutual contact, arranged into a plane, and embedded in a thermo- plastic resin 7 having a low melting point. Connection terminals 11 are provided on a glass plate 9 at a certain pitch while other connection terminals 12 are formed on the undersurface of a film form base board 10 at the same pitch, and a bond agent 8 for continuity is interposed between the upper and lower base boards 9, 10, which are joined together by hot press. The insulative film 5 of particles for continuity 6 melts to cause exposure of the electroconductive particulate 3, and now the terminals 11, 12 continued provided in the direction of orientation. This constitution ensures connections are made with high reliance even though the pitch of connection terminals is small.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a conductive connection method for electrically connecting connection terminals that are spaced apart from each other and that face each other.

[Prior Art] Various methods are known as methods for electrically connecting connection terminals that are spaced apart from each other.

The most common method is soldering.

In response to the recent demand for finer pitches of connection terminals, soldering techniques have advanced considerably. With modern equipment and extreme care, soldering can be applied to connect connection terminals of about 200 μm.

However, the disadvantages of this method are that the connecting terminals must have solder wettability and therefore must be made of at least a conductive metal foil, and because of the high temperature bonding, a heat-resistant insulating substrate is required. need to be used. These conditions increase the price of materials.

As a method for connecting connection terminals formed on inexpensive resin substrates to electronic components, a method using a conductive adhesive is known. However, this method requires accurately positioning and applying the conductive adhesive onto the connection terminal, which is extremely inefficient. Further, since the portions to which the conductive adhesive is not applied, that is, the connecting terminals are not bonded at all, the bonding force is extremely insufficient, and means for reinforcing the bonding strength is required.

Therefore, the joint portion occupies a large volume. Moreover, in addition to these drawbacks, due to poor alignment accuracy during connection work, the pitch of the connection terminals is 200~200mm.
When the thickness is less than 300 μm, short circuits and conduction failures are extremely likely to occur.

Another prior art technique is the use of a one-sided electrically conductive adhesive, which is relatively close to the concept of the present invention when compared to the techniques described above. Anisotropically conductive adhesive is a mixture of conductive particles dispersed in an insulating adhesive. When using this anisotropic conductive adhesive to connect the connection terminals of a board to the connection terminals of electronic components, the anisotropic conductive adhesive is applied not only on the connection terminals provided on the board, but also on the board between the connection terminals. is also covered. When the connection terminal of the board and the connection terminal of the electronic component are bonded by thermocompression with an anisotropic conductive adhesive interposed, the insulating adhesive interposed between each conductive fine particle and the connection terminal of the board or electronic component is bonded between the connection terminals. The conductive particles come into direct contact with the conductive particles. At this time, if the conductive particles are dispersed at sufficient distances so that they do not conduct with each other, the connection terminals provided on the board or electronic component will not be short-circuited. In the bonded state, it has conductivity in the thickness direction but exhibits insulation in the surface direction, and is an adhesive that has directionality in conductivity.

This anisotropic conductive adhesive is used as an insulating adhesive with a
Since it uses a material that melts at a relatively low temperature of 300°C, it can also be applied to resin substrates. Furthermore, it is efficient because alignment is not required when it is applied onto the connection terminals of the board. Furthermore, since the adhesive is also interposed between the connecting terminals, the bonding strength can be increased.

[Problems to be Solved by the Invention] As described above, it is an absolute condition for the anisotropically conductive adhesive to exhibit conductivity in the thickness direction and insulation in the surface direction. In order to exhibit conductivity in the thickness direction, at least (in theory) - conductive fine particles must be interposed between the connection terminal of the board and the connection terminal of the electronic component. In order to exhibit insulating properties in the direction, it is ideal that each conductive fine particle is separated from adjacent conductive fine particles by an insulating adhesive at a distance that provides electrical non-conductivity. Assuming that adjacent conductive particles happen to be insulated from adjacent connection terminals, conduction between the conductive particles is allowed only under such conditions. However, there is no guarantee that such conductive fine particles are insulated from adjacent connection terminals, and therefore it is necessary to create a structure in which no conductive fine particles are electrically connected to adjacent conductive fine particles. be.

However, in an anisotropic conductive adhesive, the arrangement of conductive fine particles dispersed in the insulating adhesive is determined only by stirring. Therefore, the distribution of conductive fine particles is
Naturally, it is not negative-like, but has dense parts and sparse parts. Therefore, the conditions arise that conductive fine particles do not conduct with each other even in dense areas, and that one or more conductive fine particles must be positioned for one connection terminal even in sparse areas.

As the pitch of the connection terminals becomes smaller and therefore the width of the connection terminals becomes narrower, it becomes more difficult to satisfy the above conditions. The number of conductive fine particles located on one connection terminal decreases as the connection terminal becomes more intermediate. However, if you increase the number of conductive particles located on the connection terminal and increase the proportion of conductive particles mixed in the insulating adhesive, the density of the conductive particles in the dense areas will further increase. . Needless to say, the dense part of the conductive fine particles fills the space between the connecting terminals in the middle and short-circuits the circuit.

Because of this structure and action, connections using anisotropic conductive adhesives are considered to be applicable even when the pitch of the connection terminals is several times the diameter of the conductive particles, but it is not practical. was far from this. −
For example, when conductive fine particles having a diameter of about 10 to 20 ILm are used, the pitch of the connecting terminals is limited to 200 to 300 Bm. Theoretically, this method cannot be applied when the pitch of the connecting terminals is smaller than the diameter of the conductive fine particles.

This invention was made in view of the above-mentioned circumstances, and its purpose is to enable low-temperature bonding to be applied to any wiring material and board material, and to reduce the pitch of connection terminals from conventional ones. The object of the present invention is to provide a conductive connection method using a conductive binder with a completely new structure, which can be applied even to cases of much smaller dimensions.

[Means for Solving the Problems J] In order to achieve the above-mentioned object, the present invention comprises conductive fine particles and an insulating film that electrically isolates the outer peripheral surface of the conductive fine particles from the outside, and the insulating film A large number of insulating particles that are finer than the conductive particles and have a lower melting point are bonded together to form conductive fine particles, and these conductive fine particles are mixed into an insulating adhesive to form a conductive particle. By forming a general-purpose binder and interposing this conductive binder between the first and second connecting terminals facing each other and thermocompression bonding, the portion of the conductive fine particles in the thickness direction of the insulating film is destroyed. , and the portion in the plane direction remains, so that the first
．． The second connection terminal is connected using the conductive fine particles.

[Function] The problem with anisotropic conductive adhesives is that in order to electrically insulate the conductive fine particles from each other, the proportion of conductive fine particles that can be mixed into the insulating adhesive cannot exceed a predetermined value. It was on point. Therefore.

If it is guaranteed that the conductive fine particles are not electrically conductive with each other, the above problem will be solved. In other words, if the proportion of conductive fine particles is sufficiently dense, a sufficient number of conductive fine particles necessary for continuity can be positioned on each connecting terminal, no matter how small the width of the connecting terminal becomes. . Furthermore, in this case, no matter how densely the conductive particles are distributed between the connection terminals, the connection terminals will not be short-circuited unless the conductive particles are electrically connected to each other.

The conductive binder of the present invention is composed of conductive fine particles that are mixed into an insulating adhesive and are formed by mutually bonding insulating fine particles that are finer than the conductive fine particles and have a lower melting point on the outer peripheral surface of the conductive fine particles. A material with an insulating film formed thereon is used.

This insulating film prevents electrical conduction between the conductive fine particles. Therefore, the conductive fine particles of the present invention exhibit the above-mentioned effect.

If electrical continuity can be achieved in the thickness direction of such a conductive binder, this binder can be applied to connection terminals arranged at a pitch no matter how small. It is clear that For this purpose, 1 ml of conductive fine particles of the present invention are made of a material with a low melting point, and the thickness direction part is destroyed by the thermocompression bonding force applied to the binder, while the planar direction part remains. .

Therefore, in the conductive connection method using this conductive binder, the conductive binder is interposed between the first and second connecting terminals facing each other and the conductive binder is bonded using a thermocompression jig or the like. Due to the conductive particles contained in the binder, the binder exhibits conductivity in the thickness direction, but exhibits insulation in the direction in which the conductive particles are arranged, that is, in the plane direction, so that the adjacent first and second Only the opposing first and second connection terminals can be reliably connected using the conductive fine particles without short-circuiting the connection terminals.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

3(A) to 3(C) show the manufacturing process of the conductive binder. First, as shown in FIG. 3(A), a conductive film 2 is formed on the surface of the resin fine particles 1 to make the resin conductive. Fine particles 3 are formed, and insulating fine particles 4 are attached to the outer peripheral surface of the conductive fine particles 3. The resin fine particles 1 are made of acrylic or the like. The conductive film 2 is coated with metal such as gold, silver, copper, nickel, aluminum, etc. by electroless plating, vapor deposition, or the like. The insulating fine particles 4 are for electrically isolating the outer circumferential surface of the conductive fine particles 3 from the outside, and are made of a low melting point (100 to 3
The conductive film 2 is made of fine powder resin at a temperature of about 100° C.) and is attracted to the outer circumferential surface of the conductive film 2 by static electricity. Note that the insulating fine particles 4 are much smaller than the conductive fine particles 3. - For example, the conductive fine particles 3 have a diameter of about 10 pm, and the insulating fine particles 4 have a diameter of about 1 m.

Next, the conductive fine particles 3 to which the insulating fine particles 4 are attached are stirred at about 50° C. using a ball mill or the like, and the 311th! J(
As shown in B), the insulating fine particles 4 are bonded to each other until they form a film or a continuous state close to a film. At this time, the insulating fine particles 4 are bonded to each other or chemically bonded,
Alternatively, they may be joined by physical bonding or the like. As a result,
An insulating film 5 in which insulating fine particles 4 are bonded to each other is formed on the outer peripheral surface of the conductive fine particles 3, thereby forming conductive fine particles 6.

Then, as shown in FIG. 3(C), the conductive particles 6 are mixed into the insulating adhesive 7 in a state in which they are arranged in a planar manner in contact with each other. As a result, the conductive binder 8 is formed. In this case, the temperature of the insulating adhesive 7 is 100 to 300°C.
For example, a hot-melt type material belonging to the heat-melting type made of thermoplastic resin is preferable, but it is not limited to this, and materials made of thermosetting resin may also be used.
Note that the thickness of the insulating adhesive 7 is formed to be slightly thicker than the size of the conductive fine particles 6.

In such a conductive binder 8, the conductive fine particles 3
are electrically isolated by the insulating film 5, the conductive fine particles 6 can be arranged in a plane in contact with each other in the insulating adhesive 7, and the conductive fine particles 3.・・・
The density of can be increased without limit as long as the adhesive strength is assumed to be sufficient.

In addition, since the insulation of the conductive particles 6 [15] is made by bonding the insulating particles 4 with a low melting point in a continuous manner into a film-like or similar state, 1 when heated and pressurized by thermocompression bonding, for example, Since the insulating film 5 at that location is melted and the conductive fine particles 3 are exposed, conduction is possible in the pressurizing direction (thickness direction) via the conductive fine particles 3. but,
Since the insulating film 5 at other locations, that is, locations in the planar direction perpendicular to the pressing direction, remains as it is, the conductive particles 6 do not conduct in the planar direction.

FIG. 1 shows a conductive connection structure using the above-mentioned conductive binder 8. In this figure, 9. IO are substrates facing each other vertically. The lower substrate 9 is, for example, a glass substrate,
A plurality of (only two are shown in this embodiment) first connection terminals 1, 1, . . . are arranged at the same pitch on the upper surface thereof. The upper substrate 1O is, for example, a film substrate, and on its lower surface, second connection terminals 12 are formed opposite to the first connection terminals 11 at the same distance. Further, the above-mentioned conductive binder 8 is interposed between the upper and lower substrates 9 and 10. That is, the upper and lower substrates 9.10
Conductive fine particles 6 are arranged in between and in contact with each other, and the gaps are filled with an insulating adhesive 7. In this case, the width of each connection terminal 11, 12 is formed wider than the diameter of the conductive fine particles 6 of the conductive binder 8. Therefore, at least one
More than one conductive fine particle 6 is arranged.

In this state, when the upper and lower substrates 9.10 are bonded by thermocompression, the upper and lower substrates 9 and 10 are bonded to each other by the insulating adhesive 7, and at the same time, the connection between the first and second connection terminals 11.12 is bonded. The insulation I5!5 of the conductive particles 6 located at the connection terminal 11.
12 is pressurized vertically and heated, so the insulation M of the part where the connecting terminals 11 and 12 come into contact (the part in the thickness direction)
5 is melted and washed away, and the internal conductive fine particles 3 are exposed and come into contact with the connection terminals 11 and 12 to establish conduction. but,
Portion where connection terminals 11 and 12 do not contact (portion in the surface direction)
Since the pressing force on the insulating film 5 is smaller than that in the thickness direction, the insulating film 5 remains as it is. In addition, the opposing connection terminal 11.1
1 or 12.12 is not pressurized by the connecting terminal 11.12, so the insulating film 5
remains as is. Therefore, conductive fine particles 3...
* does not conduct in the arrangement direction of the connecting terminals 11 and 12, but contacts only the opposing connecting terminals 11 and 12 and conducts. As a result, the adjacent connection terminals 11 and 12 are not short-circuited to each other by the conduction particles 6, and only the opposing connection terminals 11 and 12 are reliably connected. in this case,
Even if the pitch of the connecting terminals 11.12 is smaller than the size of the conductive particles 6, the adjacent connecting terminals 11.12
are not electrically connected, and it is possible to connect only the opposing connection terminals 11 and 12. This will be explained below.

FIG. 2 shows the conduction relationship between the connection terminals 13 and the conductive particles 3 when the pitch of the connection terminals 13 is smaller than that of the conduction particles 6. The dotted circles 14a to 14d are portions of the insulating film 5 that are melted during thermocompression bonding, and therefore these regions come into contact with the connection terminals 13. Furthermore, the connection terminal 13 indicated by the two-dot chain line corresponds to the connection terminals 11 and 12 in FIG. Here, the width of the connection terminal 13 is set to about 1/2 the size of the conductive fine particles 3, and the pitch is set to about 1/2 of the width of the conductive fine particles 3.
, and the length of the connecting terminal 13 is approximately twice that of the conductive fine particles 6. In addition, conduction fine particles 6
... are arranged without any gaps so that they are in contact with the adjacent ones. This is true not only in the pitch direction of the connection terminals 13 but also in the length direction. Therefore, for example, when the conductive fine particles 3 on the lower left side and the connecting terminal 13 come into contact within the hatched portion shown in the contact area 14a,
The contact area 14b of the conductive fine particles 3 on the right side jumps over the connecting terminal 13 on the right side, so it does not come into contact with the connecting terminal 13 on the right side. However, the conductive fine particles 3 on the lower left side and the contact area 14b Contact areas 14c, 14d of conductive fine particles 3, 3 located before and after the conductive fine particle 3 on the right side
As shown by diagonal lines, a part of the connecting terminal 13 on the right comes into contact with the adjacent connecting terminal 13 in the front and rear groups. This is because the conductive fine particles 3... are arranged in contact with each other, so the conductive fine particles 3 before and after
．． 3 is located between the conductive fine particles 3 on the lower left side and the conductive fine particles 3 on the right side.

In this way, even if the width and pitch of the connection terminals 13 are formed to be smaller than the conduction fine particles 6, it is possible to connect only the opposing connection terminals 13 without making the adjacent connection terminals 13 conductive. In reality, since the length of the connecting terminal 13 is much longer than the conductive particles 6, a large number of conductive particles 6 are arranged in the length direction of the connecting terminal 13, making the connection described above even more effective. For example, if the length of the connecting terminal 13 is 1 inch, the diameter is 10 pm.
If the conduction fine particles 6 are of the same size, they will be arranged in about 100 rows in the length direction. Furthermore, the conductive fine particles 6 arranged in 100 rows are slightly shifted in position in the pitch direction of the connection terminals 13, as shown in FIG. Therefore, theoretically, the present invention can also be applied to connection terminals arranged at a pitch smaller than the diameter of the conductive particles 6.

FIGS. 4 and 5 show each modification of the above-mentioned conductive connection structure. In this case, the conductive connection structures shown in both figures differ only in the structure of the conductive fine particles 3 of the conduction binder 8 described above. The other parts are the same as the conductive connection structure described above.

Therefore, here, the same parts are given the same reference numerals and the explanation thereof will be omitted.

The conductive fine particles 15 of the conductive bonding agent 8 shown in FIG. 4 are obtained by forming a conductive film 2 on the surface of an insulating particle 16, and a film of insulating fine particles 4 is formed on the outer peripheral surface thereof as described above. An insulating film 5 is formed which is bonded in a shape or in a state close to it. In this case, the insulating particles 16 are silicon oxide (S
i0? ), titanium oxide (Ti02), or other inorganic material, and conductive M2 is formed on its surface by electroless plating, vapor deposition, etc., as described above. In the conductive bonding agent 8 using such conductive fine particles 15, when the connecting terminals 11 and 12 are interposed and thermocompression bonded, the insulating particles 16 are hard particles made of an inorganic material. It is difficult to deform even when pressed, and the portion of the insulating film 5 that comes into contact with the connecting terminals 11.12 can be reliably swept away to bring the conductive film 2 into contact with the connecting terminals 11.12.

Moreover, the conductive fine particles of the conductive bonding agent 8 shown in FIG. 5! Reference numeral 7 is a metal particle such as gold, silver, copper, nickel, tin, or aluminum, or carbon particle, which itself is made of a conductive material, and the outer peripheral surface thereof is coated with insulating fine particles 4 as described above. The insulation M5 is formed by combining the two in a film form or a state close to it. With such a conductive binder 8 as well, it is possible to reliably connect only the opposing connection terminals 11 and 12 with the conductive fine particles 17, as described above.

Next, with reference to FIGS. 6 and 7, a specific example in which the above-described conductive connection structure is applied to connection between a liquid crystal display panel and a film substrate, or a connection between a liquid crystal display panel and an IC chip will be described.

FIG. 6 shows a case where the above-described conductive connection structure is applied to the connection between a liquid crystal display panel and a film substrate.
Transparent electrodes 21 and 22 made of T O (Indium Tin 0w1de) or the like are formed, and a sealant 23 is provided around them.
9. The liquid crystal 24 is sealed between 20 and the lower glass substrate 2.
0 protrudes outward from the upper glass substrate 19, a large number of connection terminals 25 are arranged at equal intervals. On the other hand, the film substrate 26 is made of TAB (Tape Au
t.

Finger leads 28 are formed on the lower surface of the carrier tape 27 by a mated bonding method, and an IC chip 29 is bonded to the finger leads 28. That is, an opening 30 is formed in the center of the carrier tape 27, and inside this opening 30, the inner ends of the finger leads 28 are provided to protrude.

At the tip of this protruding finger lead 28... is an IC.
The bumps 31 of the chip 29 are bonded and sealed with a resin 32.

In this case, the finger leads 28 are formed by etching a metal foil such as copper laminated on the carrier tape 27, and the outer ends thereof are formed as connection terminals 33. Note that the same number of connection terminals 33 as the connection terminals 25 of the liquid crystal display panel 18 are arranged.

When connecting the liquid crystal display panel 18 and the film substrate 26, the connection terminals 33 of the film substrate 26 are placed above the connection terminals 25 of the liquid crystal display panel 18, and the above-mentioned conductive binder 8 is applied between the connection terminals 33 of the film substrate 26. Deploy. In this state, a heater chip (not shown) is pressed onto the film substrate 23 to bond the conductive binder 8 by thermocompression. Then, the respective connection terminals 25.33 are bonded to each other by the insulating adhesive 7 of the conduction binder 8, and the opposing connection terminals 25.33 are electrically connected by the conductive fine particles 3 of the conduction fine particles 6. be done.

Therefore, in such a connection structure between the liquid crystal display panel 18 and the film substrate 26, the opposing connection terminals 25.3
The connection can be easily made by simply disposing the conductive bonding agent 8 between the parts 3 and bonding them by thermocompression. In this case, each connection terminal 25
．． Even if the number of terminals 33 is large and the pitch is fine, the adjacent connection terminals 25.33 will not be electrically connected, and only the opposing connection terminals 25.33 can be reliably connected.

FIG. 7 shows a case where an IC chip 29 is connected to a liquid crystal display panel 18, which is applied to the so-called chip-on-glass method. In this case, the lower glass substrate 20 of the liquid crystal display panel 18 is connected to the upper glass substrate. 19, and the connecting terminal 3 is placed on the protruding lower glass substrate 20.
4 are patterned in a predetermined arrangement. When connecting the IC chip 29 to the connecting terminal 34, a conductive binder 8 is placed on the connecting terminal 34, and the bump 31 of the IC chip 29 is connected to the connecting terminal 34 through the conductive binder 8. Place it opposite. In this condition.

If a heater chip (not shown) is pressed onto the IC chip 29 and the conductive bonding agent 8 is bonded by thermocompression, the IC chip 29
and the glass substrate 20 are bonded to each other by the insulating adhesive 7 of the conductive bonding agent 8, and the adjacent connection terminals 34
Also, adjacent bumps 31 are not short-circuited with each other, and only the opposing connection terminals 34 and bumps 31 can be reliably electrically connected by the conductive particles 3 of the conduction particles 6.

[Effects of the Invention] As explained in detail above, the present invention can be applied even when the pitch of the connecting terminals is much smaller than that of the conventional method, and the conductive particles are insulated by an insulating adhesive. However, since the conductive particles themselves have an insulating film, short circuits of the connecting terminals can be reliably prevented.
In addition, since low-temperature bonding is possible, it can be used as an inexpensive material for connecting terminals and insulating substrates, and it has excellent connection reliability despite the small pitch of the connecting terminals. .

[Brief explanation of drawings]

Fig. 1 is an enlarged sectional view of a main part showing an example of a connection structure to which the conductive connection method of the present invention is applied, and Fig. 2 shows connection terminals and conductive particles when the pitch of the connection terminals is smaller than that of the conductive particles. 3 (A) is a plan view for explaining the conduction of
) to (C) are cross-sectional views showing the manufacturing process of the conductive binder,
4 and 5 are cross-sectional views showing various modifications of the conductive connection structure, and FIG. 6 is a cross-sectional view when the conductive connection method of the present invention is applied to connection between a liquid crystal display panel and a film substrate.
FIG. 7 is a sectional view when applied to connection between a liquid crystal display panel and an IC chip. 3.15.17... Conductive fine particles, 4...
...Insulating fine particles, 5...Insulating film, 6...
... fine particles for conduction, 7... insulating adhesive, 8.
...Binding agent for conductivity. 11.12.13.25.33.34... Connection terminal, 29... Bump. 3- is the broken grain chart (Fig. 4) 5. Toughness chart

Claims (1)

[Claims] It consists of conductive fine particles and an insulating film that electrically isolates the outer peripheral surface of the conductive fine particles from the outside, and the insulating film interconnects a large number of insulating fine particles that are finer than the conductive fine particles and have a lower melting point. The conductive fine particles are formed by bonding, the conductive fine particles are mixed into an insulating adhesive to constitute a conductive binder, and the conductive binder is attached to first and second By thermocompression bonding between the connecting terminals, a portion of the conductive fine particles in the thickness direction of the insulating film is destroyed, and a portion in the planar direction remains, thereby forming the first and second connecting terminals. A conductive connection method characterized in that the conductive particles are connected by the conductive fine particles.