JPH03107888A - Connecting structure for circuit board - Google Patents

Abstract

PURPOSE:To eliminate the need for application of a silicone resin for reinforcement by interposing a resin layer which does not contain conductive particles or contains the conductive particles at the mixing ratio smaller than the mixing ratio of a conductive resin layer between the conductive resin layer and a 1st electrode or 2nd electrode. CONSTITUTION:The 1st resin layer 6 is interposed between the flexible substrate electrode 2 formed on a flexible substrate 1 and a glass substrate electrode 4 formed on the glass substrate 3 and this 1st resin layer 6 is constituted by mixing and dispersing the conductive particles 8 with and in the thermosetting resin 9. Further, the 2nd resin layer 7 is interposed between the 1st resin layer 6 and the flexible substrate electrode 2 and between the 1st resin layer 6 and the glass substrate electrode 4. This 2nd resin layer 7 is the resin layer which consists of nearly the same material as the material of the 1st resin layer 9 and is not incorporated with the conductive particles 8 or is smaller in the mixing ratio thereof than in the 1st resin layer 6. The resin layer 7 is low in melt viscosity by heating and pressurizing and is extruded into the gap part between the 1st member and the 2nd member. The resin layer further flows out to the end of the circuit board to fix both substrates. The need for reinforcing the 1st member 1 and the 2nd member 3 is eliminated in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a circuit board connection structure suitably implemented in connection with a display device such as a liquid crystal display device typified by, for example, a liquid crystal television receiver.

More specifically, for example, a tape automated bond is attached to a glass substrate such as a display panel.
ng) It relates to a circuit board connection structure suitably implemented when connecting a flexible board mounted with a driving integrated circuit known as a tape.

Prior Art A typical prior art using an anisotropic conductive film, which is a conductive resin layer, will be explained first with reference to FIGS. 4 and 5. Next, with reference to FIGS. 6 and 7. will be explained in more detail.

FIG. 4 is a perspective view showing the appearance of a liquid crystal television receiver 15 in which a glass substrate 3 and a flexible substrate 1 constituting a liquid crystal panel are connected using an anisotropic conductive film. Fifth
[! 1 is a sectional view of a connecting portion between the glass substrate 3 and the flexible substrate 1. FIG.

In recent years, the degree of integration of pixels in liquid crystal display devices such as liquid crystal television receivers has increased, and the pitch of electrodes from the glass substrate 3 has also increased to 100 μm.
The extent of this is becoming extremely small. For this reason, connections using the anisotropic conductive film 5 have become mainstream instead of the conventionally used conductive rubber connector system.

Referring to FIGS. 4 and 5, in the liquid crystal television receiver 15, the glass substrate 3 and the color filter substrate 10 attached with the deflection plate 12, which is indicated by hatching in FIG. 4, partially overlap. Has area A.

and are superimposed. In this region A, a liquid crystal material or the like is sealed between the glass substrate 3 and the color filter substrate 10, and a liquid crystal display is performed. In the non-overlapping area B, the flexible substrate 1 carrying the driving integrated circuit 11 known as tab tape and the glass substrate 3 are electrically and mechanically connected via the anisotropic conductive film 5. Furthermore, a silicone resin 13 is applied to the end of the connection between the glass substrate 3 and the flexible substrate 1 to reinforce the mechanical connection.

The connection using the anisotropic conductive film 5 will be described in more detail with reference to FIGS. 60 and 7.

FIG. 6 is an enlarged cross-sectional view of the connecting portion between the flexible substrate 1 and the glass substrate 3 before heating and pressing by the hot press mold 14, and FIG. 7 (2I is an enlarged cross-sectional view after heating and pressing. .

As shown in FIG. 6, a plurality of flexible substrate electrodes 2 are formed on the surface of the flexible substrate 1 facing the glass substrate 3. As shown in FIG. Further, a plurality of glass substrate electrodes 4 are also formed on the surface of the glass substrate 3 facing the flexible substrate 1. The flexible substrate 1 and the glass substrate 3 are arranged so that the flexible substrate electrode 2 and the glass substrate electrode 4 face each other. An anisotropic conductive film 5, which is a conductive resin layer made of a mixture of conductive particles 8 and resin 9, is interposed between the flexible substrate electrode 2 and the glass substrate electrode 4. When this is heated and pressurized using the hot press mold 14, as shown in FIG. There is a short circuit between the two and conduction occurs. When metal particles are used as the conductive particles, the metal particles are aggregated and crushed to about three times the initial diameter. In other areas, the conductive particles remain dispersed and non-conductive. As a result, flexible substrate electrode 2 and glass substrate electrode 4 are selectively electrically connected, and no short circuit occurs between adjacent electrodes.

Problems to be Solved by the Invention However, in the connection using such a prior art anisotropic conductive film, the resin 9 does not wrap around easily in areas where the flexible substrate electrode 2 and the glass substrate electrode 4 do not face each other. Furthermore, the gap between the flexible substrate 1 and the glass substrate 3 may not be completely filled. As a result, sufficient adhesion strength between the flexible substrate 1 and the glass substrate 3 cannot be obtained, so that variations in conduction resistance or disconnection may occur in a temperature cycle test or the like. Additionally, in order to increase the adhesive strength, silicone resin 13 is applied for reinforcement, but this requires an extra process and not only that, but also requires a large amount of silicone resin to be applied. Depending on the temperature conditions, a force due to contraction or expansion of the silicone resin may be applied to the connection part, which may have an adverse effect.

The object of the present invention is to solve the above-mentioned problems, to have good adhesive strength, and to provide reinforcing silicone I! To provide a circuit board connection structure that does not require one-finger application.

Means for Solving the Problems The present invention provides a method in which conductive particles and resin are mixed between a first electrode formed on a first member and a second electrode formed on a second member. In a circuit board connection structure in which a first electrode and a second electrode are electrically connected to each other through a conductive resin layer and a first member and a second member are bonded to each other, the conductive resin layer A resin layer containing no conductive particles or a mixed gap of conductive particles is formed between the conductive resin layer and the first electrode or at least one of the interleaves between the conductive resin layer and the second electrode. This is a circuit board connection structure characterized by intervening a resin layer smaller than the size of the above.

Function: In the circuit board connection structure according to the present invention, the first electrode formed on the first member and the second electrode formed on the second member individually corresponding to the first electrode are made of conductive resin. Each layer is electrically connected by conductive particles contained in the layer. Further, the first member and the second member are mechanically connected by the resin layer.

Furthermore, the present invention does not contain conductive particles.

Alternatively, a resin layer with a small amount is interposed, and since this resin layer has a low melt viscosity when melted by heating and pressurizing, it is quickly extruded into the gap between the first member and the second member and fills the gap. . Furthermore, it flows out to the edge of the circuit board and fixes both boards, reinforcing the mechanical connection between the first member and the second member.

Embodiment An embodiment of the present invention will be described with reference to FIGS. FIG. 1 is an embodiment of the present invention, and is a cross section showing a connection structure using an anisotropic conductive film 5, which is a conductive resin layer, between a flexible substrate 1, which is a first member, and a glass substrate 3, which is a second member. It is a diagram. FIG. 2 is a characteristic diagram showing the viscosity change of the thermosetting resin of the anisotropic conductive film 5 used in the same example. FIG. 3 is a sectional view showing the state of the same plan jIi13i1 after the circuit board is connected.

As shown in FIG. 1, one or more flexible substrate electrodes 2, which are first electrodes, are formed on the surface of the flexible substrate 1 facing the glass substrate 3. Also, on the surface of the glass substrate 3 facing the flexible substrate 1, 1
Alternatively, two or more glass substrate electrodes 4 as second electrodes are formed.

The flexible substrate 1 and the glass substrate [3 are arranged so that the flexible substrate electrode 2 and the glass substrate electrode 4 face each other.

A 1V14th resin layer 6 is interposed between the flexible substrate electrode 2 formed on the flexible substrate 1 and the glass substrate electrode 4 formed on the glass substrate 3.

This 11th! The resin layer 6 is made by mixing and dispersing conductive particles 8 made of a conductive material such as metal particles such as nickel or solder or carbon fiber in a thermosetting resin 9, which is a binder such as epoxy resin. Ru. The thermosetting resin is used in a semi-cured state, so-called B stage state.

No. 11111! There is also a 21st layer between the resin layer 6 and the flexible substrate electrode 2 and between the first resin layer 6 and the glass substrate electrode 4. ! A fat layer 7 is interposed. This second resin layer 7
This is a resin layer in which the conductive particles 8 are not contained in substantially the same material as the resin layer of the first resin layer, or the warm ratio thereof is smaller than the mixing ratio of the first resin layer 6 even if the conductive particles 8 are contained.

Anisotropically conductive WA5 is made by heating and pressing with a hot press mold.
When the resin 9 constituting the resin 9 is melted, the melt viscosity of the resin 9 changes as shown in FIG. In Figure 2, curve 1
1 shows the viscosity change of the first resin layer 6 containing conductive particles 8, and curve 12 shows the change in the viscosity of the first resin layer 6 containing conductive particles 8, and the curve 12 shows whether the conductive particles are not contained or even if the conductive particles are contained, the mixing ratio is higher than the mixing ratio of the first resin layer 6. The first resin layer 6 exhibiting a small viscosity change in the second resin layer 7 has a large viscosity when melted because it contains the conductive particles 8, and also tends to increase its viscosity quickly when cured. On the other hand, the second resin layer 7 has a low viscosity when melted, and the increase in viscosity during curing is also slower than that of the first resin layer 6. Therefore, the second resin layer 7 quickly flows out and The amount of the outflow is also large, and the resin 9 of the second resin layer 7 seals the gap between the glass substrate 3 and the flexible substrate 1 without leaving any gap, and furthermore, it flows out of the connection part and reinforces the sealing.

The state of the circuit board connection portion of the liquid crystal display device using the present invention will be explained with reference to FIG. The glass substrate 3 and the color filter substrate 10 are overlapped with each other with a partially overlapping area A. In this region A, a liquid crystal material or the like is sealed between the glass substrate 3 and the color filter substrate 1°.
In 6 non-overlapping areas B where a liquid crystal display is performed, a flexible substrate 1 equipped with a driving integrated circuit known as tab tape and a glass substrate 3 are electrically and mechanically connected using the anisotropic conductive film 5 of the present invention. connected.

As mentioned above, the second t1[1 resin rM7 has a low viscosity when melted, so it seals the flexible substrate 1 and the glass substrate 3 without leaving any gaps, and furthermore, it flows out of the connection part,
Strengthen the seal. That is, the resin 9 mainly supplied from the second vA resin layer 7 can seal the gap between the flexible substrate 1 and the glass substrate 3, and also seal the end of the front substrate. In this way, the bonding area is increased and the edges of the substrate can also be sealed, resulting in high bonding strength and no need for conventional reinforcement using silicone resin.

In this embodiment, the anisotropic conductive film 5 is formed by laminating the second resin layer 7 on both sides of the first resin layer 6, but it may also be formed on only one side. The thickness of the flexible substrate electrode 2 of the flexible substrate 1 is
The thickness of the glass substrate electrode 4 of the glass substrate 3 is about 10 to 30 μm, whereas the thickness of the glass substrate electrode 4 of the glass substrate 3 is as thin as several 1000 μm. Therefore, the second vA fat layer 7 may be formed only on one side of the flexible substrate 1.

Further, the melt viscosity can be adjusted by dispersing non-conductive particles in the second resin layer 7 to an extent that does not adversely affect the electrical connection.

Furthermore, the resin components of the first vI4 resin layer 6 and the second resin layer 7 do not need to be the same, and as long as they have an affinity, different resins may be used to optimize the viscosity and flow rate.

Further, conventionally, both thermoplastic resin and thermosetting resin have been used for the anisotropic conductive film. However, since the thermoplastic resin needs to be rapidly cooled after heating and pressurizing, and the adhesive strength is low, there has recently been a tendency to use thermosetting resins such as epoxy resins. However, in the present invention, since the strength of the adhesion is aimed at as described above, it is also possible to use thermoplastic resin.

Furthermore, the present invention is not limited to the connection structure of a liquid crystal display device, but is a connection structure of a circuit board that can be applied to all devices using an anisotropic conductive film.

Effects of the Invention As described above, according to the present invention, it is possible to bond circuit boards with good adhesion using the conventional hot press or other thermocompression bonding method, and which does not require the application of silicone resin to reinforce the connection parts. A connection structure can be realized.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of an embodiment of the present invention, Fig. 2 is a characteristic diagram showing changes in viscosity of the resin used in an embodiment of the present invention, and Fig. 3 is a diagram after connecting a circuit board of an embodiment of the present invention. 4 is a perspective view showing the external appearance of a liquid crystal television receiver using an anisotropic conductive 1C film according to the prior art. FIG. cross section,
FIG. 6 is a cross-sectional view showing the state of the connection between the flexible substrate and the glass substrate before pressure and heating in the prior art, and FIG. It is a sectional view showing a state. DESCRIPTION OF SYMBOLS 1... Flexible substrate, 2... Flexible substrate electrode, 3... Glass substrate, 4... Glass substrate electrode,
5...Anisotropic conductive TFI, 6--first resin layer, 7...
Second resin layer, 8... Conductive particles, 9... Resin, 10
... Color filter substrate, 11 ... Driving@product circuit, 12 ... Deflection plate, 13 ... Silicone resin, 14.
...Hot press mold, 15...LCD television receiver, 16...LCD display device

Claims (1)

[Claims] A conductive resin layer formed by mixing conductive particles and resin between a first electrode formed on a first member and a second electrode formed on a second member. A connection structure for a circuit board in which a first electrode and a second electrode are electrically connected to each other and a first member and a second member are bonded together through the conductive resin layer and the first electrode. or between the conductive resin layer and the second electrode, a resin layer containing no conductive particles or a resin layer in which the mixing ratio of the conductive particles is smaller than the mixing ratio of the conductive tree layer. A circuit board connection structure characterized by intervening.