JP3027841B2 - Wiring board connection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for connecting wiring boards.

[0002]

2. Description of the Related Art In electronic equipment, wiring boards are often electrically connected. For example, in a liquid crystal display device, a connection terminal of a glass substrate (wiring substrate) of a liquid crystal display panel and a connection terminal of a carrier tape (wiring substrate) on which a semiconductor chip for driving the liquid crystal display panel is mounted are electrically conductive. In some cases, conductive connection is made via an anisotropic conductive adhesive obtained by mixing particles in an insulating adhesive. In this case, for example, FIG.
As shown in FIG. 1, one strip-shaped anisotropic conductive adhesive 3 is disposed on the connection portion including the connection terminal 2 provided on the upper surface of the carrier tape 1, and on the disposed anisotropic conductive adhesive 3 The connection portion including the connection terminal 5 of the glass substrate 4 is placed, and the connection portion including the connection terminal 2 of the carrier tape 1 and the connection portion including the connection terminal 5 of the glass substrate 4 are heated using a heater chip or laser light. When thermocompression bonding is performed, a part of the insulating adhesive 6 in the anisotropic conductive adhesive 3 flows and escapes, so that a part of the conductive fine particles 7 in the anisotropic conductive adhesive 3 The connection terminal 2 and the connection terminal 5 of the glass substrate 4 facing the connection terminal 2 are both in contact with each other, thereby electrically connecting the connection terminal 2 of the carrier tape 1 to the connection terminal 5 of the glass substrate 4. The insulating adhesive 6 in the conductive adhesive 3 is By reduction, and bonding the connecting portion including the connection terminal 5 of the connecting portion and the glass substrate 4 including the connection terminal 2 of the carrier tape 1.

[0003]

However, in such a conventional method of connecting a wiring board, since the anisotropic conductive adhesive 3 having a substantially uniform distribution density of the conductive particles 7 is used, the heat is hardly applied. There is no problem if the crimping conditions are as expected. For example, if the temperature distribution is not uniform between the center and the end of the heater chip or the laser beam, the inside of the insulating adhesive 6 may be reduced. Since the viscosity varies, the fluidity of the insulating adhesive 6 at a relatively high temperature and low viscosity is large, so that the conductive particles 7 are easily crushed by thermocompression bonding, and the conductive particles 7 are easily moved. Since the fluidity of the high viscosity portion is small, the portion is not easily crushed by thermocompression and the conductive particles 7 are not easily moved. Therefore, the conductive particles 7 existing in the relatively high-temperature portion move to the relatively low-temperature portion. For example, as shown in FIG. It may be concentrated on one side, or may be dispersed on both sides in the width direction of the insulating adhesive 6, as shown in FIG. 9, and as a result, the distribution density of the conductive particles 7 may be considerably high in some parts, and as a result, There is a problem that a short circuit may occur between adjacent connection terminals 2 and 5. In particular, pitch 10
In the case of a fine pattern of 0 μm or less, the length L (see FIG. 7) of the opposing portions of the connection terminals 2 and 5 is increased in order to increase the conductive connection area, and the anisotropic conductive adhesive 3 is used. It is desirable to increase the length in the width direction, but on the other hand, the number of conductive particles 7 in the anisotropic conductive adhesive 3 increases, and a short circuit occurs between adjacent connection terminals 2 and 5. The risk rate increases. An object of the present invention is to provide a method of connecting a wiring board that can prevent a short circuit from occurring between adjacent connection terminals.

[0004]

SUMMARY OF THE INVENTION The present invention provides an anisotropic conductive bonding method in which a connecting terminal of one wiring board and a connecting terminal of another wiring board are mixed with conductive particles in an insulating adhesive. In the connection method of a wiring board, which is conductively connected by thermocompression bonding via an agent, the distribution density of conductive particles between the connection terminals of one wiring board and the connection terminals of another wiring board during thermocompression bonding is reduced. The distribution density of the conductive particles is increased in the parts where there is a tendency, and the distribution density of the conductive particles is increased in the parts where the distribution density of the conductive particles tends to increase. After the pressure bonding, the distribution density of the conductive particles in the anisotropic conductive adhesive is made substantially uniform.

[0005]

According to the present invention, the conductive particles are less likely to be distributed between the connection terminals of one wiring board and the connection terminals of the other wiring board in a portion where the distribution density of the conductive particles tends to decrease during thermocompression bonding. The distribution density of the conductive particles is increased and the distribution density of the conductive particles tends to increase. Anisotropic conductive adhesive with reduced distribution density of the conductive particles is interposed in Since the distribution density of the conductive particles in the agent is made substantially uniform, it is possible to prevent a short circuit from occurring between adjacent connection terminals.

[0006]

1 and 2 are views for explaining one embodiment of the present invention, in which a connection terminal of a glass substrate of a liquid crystal display panel and an I / O for driving the liquid crystal display panel are shown.
The connection terminal of the carrier tape on which the C chip is mounted
It shows a state in which conductive connection is made via an anisotropic conductive adhesive.

In the liquid crystal display panel 11, transparent electrodes 14 and 15 are provided on opposing surfaces of a pair of upper and lower glass substrates 12 and 13, a sealing material 16 is provided therebetween, and a liquid crystal 17 is provided therein. It has a sealed structure. In this case, one end of the upper glass substrate 12 protrudes from one end of the lower glass substrate 13, and a connection terminal 18 is provided on the lower surface of one end of the protruded upper glass substrate 12 to form the transparent electrode 1.
4 and is provided.

As shown in FIG. 3, the carrier tape 21 has a tape body 22 made of a resin film such as polyethylene terephthalate, polyethersulfone, or polyimide. A lead pattern made of a metal foil is formed on the upper surface of the tape main body 22, so that a finger lead 24 protrudes from an opening 23 formed in the center of the tape main body 22. The unit is provided with an output-side connection terminal 25, and the other end of the tape body 22 is provided with an input-side connection terminal 26. The bump electrodes 28 of the IC chip 27 disposed in the openings 23 are joined to the finger leads 24 by thermocompression. This joint is sealed with a sealing material 29 made of resin. Output connection terminal 25
Are arranged at the same pitch as the connection terminals 18 of the glass substrate 12 on the upper side of the liquid crystal display panel 11.

The anisotropic conductive adhesive 31 comprises conductive particles 32
Is mixed in the insulating adhesive 33. Among them, the conductive particles 32 are obtained by coating a conductive film made of a metal such as gold, silver, copper, nickel, or aluminum on the surface of resin particles made of an acrylic resin or the like by plating or vapor deposition, or gold, silver, copper, or the like. , Nickel, aluminum and the like. The insulating adhesive 33 is made of a thermosetting or thermoplastic resin.

Next, a description will be given of a case where the connection terminals 18 of the glass substrate 12 on the upper side of the liquid crystal display panel 11 and the connection terminals 25 on the output side of the carrier tape 21 are conductively connected. The distribution state of the conductive particles 32 initially becomes, for example, a thermocompression bonding condition (a condition in which the conductive particles 7 move and concentrate on one side in the width direction of the insulating adhesive 6) as shown in FIG. Suppose In this case, for example, as shown in FIG.
3a, a strip-shaped anisotropic conductive adhesive 3 in which the distribution density of the conductive particles 32a is relatively large but substantially uniform.
1a and the conductive particles 32 in the insulating adhesive 33b
A band-like anisotropic conductive adhesive 31b having a relatively small but substantially uniform distribution density of b is prepared. Then, as shown in FIG. 4, a portion of the upper surface of the carrier tape 21 indicated by a dashed line in FIG. An anisotropic conductive adhesive 31a having a relatively large distribution density of conductive particles is disposed, and in the case shown in FIG. 8, the distribution density of the conductive particles tends to increase after thermocompression bonding. Conductive adhesive 31 having a relatively small size
b is arranged. Next, a connection portion including the connection terminal 18 of the glass substrate 12 is placed on the upper surfaces of the anisotropic conductive adhesives 31a and 31b thus arranged. When the connection portion including the connection terminal 25 on the output side of the carrier tape 21 and the connection portion including the connection terminal 18 on the glass substrate 12 are thermocompression-bonded using a heater chip or laser light, the distribution densities of the conductive particles are compared. Of the conductive particles 32a in the anisotropically conductive adhesive 31a having a relatively large size move into the anisotropically conductive adhesive 31b in which the distribution density of the conductive particles is relatively small,
As a result, for example, as shown in FIG. 6, the distribution density of the conductive particles 32 in the anisotropic conductive adhesive 31 as a whole becomes substantially uniform.

Next, due to the non-uniform temperature distribution at the time of the thermocompression bonding, the distribution state of the conductive particles 32 is initially set to the thermocompression bonding condition (for example, as shown in FIG. Condition that the light is distributed on both sides in the width direction). In this case, as shown in FIG. 5, for example, one strip-shaped anisotropic conductive adhesive 31a in which the distribution density of the conductive particles 32a in the insulating adhesive 33a is relatively large but substantially uniform, Two strip-shaped anisotropic conductive adhesives 31b in which the distribution density of the conductive particles 32b in the insulating adhesive 33b is relatively small but substantially uniform are prepared. Then, as shown in FIG. 5, an anisotropic conductive adhesive 3 having a relatively large distribution density of conductive particles is provided at a central portion in the width direction of a portion indicated by a chain line in FIG.
1a is disposed, and anisotropic conductive adhesives 31b having relatively small distribution density of conductive particles are disposed on both sides thereof.
Next, the anisotropic conductive adhesives 31a, 3
A connection portion including the connection terminal 18 of the glass substrate 12 is placed on the upper surface of 1b. When the connection portion including the connection terminal 25 on the output side of the carrier tape 21 and the connection portion including the connection terminal 18 on the glass substrate 12 are thermocompression-bonded using a heater chip or laser light, the distribution densities of the conductive particles are compared. Conductive particles 32a in anisotropically conductive adhesive 31a
Are moved into the anisotropic conductive adhesive 31b in which the distribution density of the conductive particles on both sides thereof is relatively small, and as a result, for example, as shown in FIG. The distribution density of the conductive particles 32 in the agent 31 becomes substantially uniform.

As described above, in this liquid crystal display device, the distribution density of the conductive particles between the connection terminal 25 on the output side of the carrier tape 21 and the connection terminal 18 on the glass substrate 12 is reduced by the thermocompression bonding condition. The anisotropic conductive adhesives 31a and 31b are used, in which the distribution density of the conductive particles in the portion where the tendency is increased is increased, and the distribution density of the conductive particles in the portion where the distribution density of the conductive particles is increased is reduced. And
After the thermocompression bonding, the distribution density of the conductive particles 33 in the anisotropic conductive adhesive 31 is made substantially uniform.
It is possible to prevent a short circuit from occurring between adjacent connection terminals 18 and 25.

In the above embodiment, a plurality of anisotropic conductive adhesives 31a and 31b, which have different distribution densities of conductive particles but are substantially uniform in a single unit, are used. Of course, one sheet of anisotropic conductive adhesive having a distribution density difference of conductive particles may be used.

[0014]

As described above, according to the present invention, the distribution density of conductive particles between the connection terminals of one wiring board and the connection terminals of another wiring board during thermocompression bonding is reduced. The distribution density of the conductive particles is increased in the parts where there is a tendency, and the distribution density of the conductive particles is increased in the parts where the distribution density of the conductive particles tends to increase. Since the distribution density of the conductive particles in the anisotropic conductive adhesive after the pressure bonding is made substantially uniform, it is possible to prevent a short circuit from occurring between adjacent connection terminals.

[Brief description of the drawings]

FIG. 1 is a view for explaining an embodiment of the present invention, in which a connection terminal of a carrier tape and a connection terminal of a glass substrate of a liquid crystal display panel are conductively connected via an anisotropic conductive adhesive. FIG.

FIG. 2 is a sectional view taken along the line AA in FIG. 1;

FIG. 3 is a plan view of a carrier tape.

FIG. 4 is a plan view showing a state in which two anisotropic conductive adhesives are arranged at connection terminal portions of a carrier tape under a certain thermocompression bonding condition.

FIG. 5 is a plan view showing a state in which three anisotropic conductive adhesives are arranged on connection terminal portions of a carrier tape under another thermocompression bonding condition.

FIG. 6 is a plan view for explaining a state after thermocompression bonding.

FIG. 7 is a plan view showing a state in which one anisotropic conductive adhesive is arranged at a connection terminal portion of a carrier tape in a conventional example.

FIG. 8 is a plan view for explaining a problem of the conventional example.

FIG. 9 is a plan view for explaining a problem of the conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Liquid crystal display panel 12 Glass substrate 18 Connection terminal 21 Carrier tape 25 Connection terminal 31, 31a, 31b Anisotropic conductive adhesive 32, 32a, 32b Conductive particles 33, 33a, 33b Insulating adhesive

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01R 43/00 H01L 21/603 H01L 23/50 H01R 11/01 H05K 3/36

Claims (1)

(57) [Claims] 1. A connection terminal of one wiring board and a connection terminal of another wiring board are conductively bonded by thermocompression through an anisotropic conductive adhesive obtained by mixing conductive particles in an insulating adhesive. In the method of connecting a wiring board to be connected, the conductive particles are distributed between the connection terminals of the one wiring board and the connection terminals of the other wiring board in a portion where the distribution density of the conductive particles tends to be reduced during thermocompression bonding. The distribution density of conductive particles is increased, and anisotropic conductive adhesive with reduced distribution density of conductive particles is interposed in the part where the distribution density of conductive particles tends to increase, and after the thermocompression bonding, the anisotropic conductive adhesive is used. A method for connecting a wiring board, wherein a distribution density of conductive particles in a conductive adhesive is made substantially uniform.