JPH0661642A - Jointing method for flexible resin board - Google Patents

Abstract

PURPOSE:To joint the terminal of a thin wiring pattern of a planar display module with a terminal of a thick wiring pattern of a circuit board, on which a driving circuit and the like are formed, through a flexible resin board formed with a wiring pattern such that both terminals are jointed through an adhesive film having uniform thickness while ensuring conductivity at the joint. CONSTITUTION:Dielectric resin 6 is filled in a recess 3 made in one board at a joint of a circuit board 4 and a flexible resin board 1 for connecting thick wiring patterns with each other thus reducing the volume of the recess and then both terminals are connected through a thin anisotropic conductive adhesive film 7.

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 a flexible resin substrate on which a wiring pattern is formed. More specifically, the present invention relates to a flexible resin substrate connection method for electrically connecting a wiring pattern of a substrate of a flat-panel display device such as a liquid crystal display device (LCD), electroluminescence (EL), or plasma display to a wiring pattern of a circuit board. .

[0002]

2. Description of the Related Art In order to electrically connect each terminal of a wiring pattern formed on a flat display module such as an LCD to each terminal of a wiring pattern of a circuit board on which a driving circuit is formed, the terminals may be bent in the middle of the wiring. TA to be able to
B (Tape Automated Bonding) and FPC (Flexible printe)
A wiring pattern such as a d circuit) is mediated by a flexible resin substrate formed by a printing method or an evaporation method, and one end side of the flexible resin substrate is a flat display module and the other end side is a drive circuit. It is configured to be adhered to a circuit board on which elements and the like are formed and to connect each wiring.

A conventional bonding method for this flexible resin substrate will be described with reference to FIG. In FIG. 2, a thickness of 35 μm is formed on a flexible resin substrate 11 such as a polyimide resin having a thickness of 25 μm.
A substrate on which a wiring pattern 12 made of a Cu film is formed,
Again, the circuit board 13 on which the wiring pattern 14 is formed is aligned and the anisotropic conductive adhesive film (ACF) 15 is interposed (see FIG. 2A). Here, the anisotropic conductive adhesive film is an adhesive film in which conductive particles, which are gold-plated resin balls having a particle size of about 5 μm, are mixed in an epoxy adhesive, and the adhesive and the conductive particles are void when pressed. Extruded to the part, even with the uneven portion is evenly bonded, in the convex portion has conductive by pressure-contacting the conductive particles, the concave portion has an adhesive effect but the conductive particles do not contact, It does not have lateral conductivity.

Next, two substrates with an anisotropic conductive adhesive film interposed are pressure-welded to each other at a temperature of 150 ° C. and a pressure of 15 to 20 kgf.
Heat and pressurize at 30 cm / cm ² for 30 to 40 seconds to bond (see FIG. 2 (b)). At this time, since the anisotropic conductive adhesive film on the convex portion of the Cu film is pushed to the concave portion between the adjacent convex portions, the concave portion is almost filled with the anisotropic conductive adhesive film, and the dimension C between both substrates is It is approximately equal to the sum of the thicknesses of the wiring patterns formed on both substrates.

[0005]

In order to connect the flexible resin substrate to the flat display type module and the circuit board by the above-mentioned method, an anisotropic conductive adhesive film having a different thickness is prepared. There must be. That is, the wiring pattern of the flat-panel display type module is usually formed as thin as 1 μm or less with an ITO film or the like because of its light transmittance, but the wiring pattern of the circuit board or the flexible resin substrate is a Cu film or the like.
It is formed with a thickness of about 35 μm. Therefore, the dimensions between both substrates after bonding on the flat display module side (Fig. 2 (b))
C) is 35 to 40 μm, and the thickness of the anisotropic conductive adhesive film is about 20 μm, while on the circuit board side, the wiring patterns of both boards have a thickness of about 35 μm.
This is because the anisotropic conductive adhesive film needs to have a thickness of 35 to 40 μm.

Further, when the two substrates are pressure-bonded to each other, the conductive particles and the adhesive present in the convex portions are almost pushed to the concave portions, but the convex portions on both sides are highly convex like the flexible resin substrate and the circuit board are adhered. When the substrate on which the striped portion is formed is pressed, a large pressure is temporarily applied to the convex portion. Especially, if the wiring patterns of the upper and lower substrates are misaligned, the contact area becomes smaller, and the larger pressure is applied to the resin in that portion. As a result, the conductive particles are crushed. As described above, the conductive particles are resin balls plated with gold, etc., and when pressed in a ball shape, they have elasticity to ensure contact with both substrates, but when the balls are crushed they are elastic. There is a problem that the electrical contact between the wiring patterns of both substrates becomes insufficient.

The present invention solves the above problem and enables the flexible resin substrate to be bonded on either side of the flat panel display module and the circuit substrate with an anisotropic conductive adhesive film having the same thickness. At the same time, it is an object of the present invention to provide a method for connecting a flexible resin substrate so that the wiring patterns of both substrates can be surely connected even if a slight displacement occurs.

[0008]

A method of connecting a flexible resin substrate according to the present invention comprises a wiring pattern provided on a flat display module and a wiring pattern provided on a circuit board on which a driving circuit and the like are formed. Is a method for connecting a flexible resin substrate through a wiring pattern provided on the flexible resin substrate, wherein insulation is provided in a concave portion between the wiring patterns provided on the flexible resin substrate or the circuit board. It is characterized in that it is filled with a conductive resin and then thermocompression bonded with an anisotropic conductive adhesive film interposed between both substrates.

[0009]

According to the flexible resin substrate connecting method of the present invention,
When bonding to a substrate such as a circuit board on which a wiring pattern with high protrusions is formed, the recesses between the protrusions are pre-filled with resin, so a thin ITO film etc. was formed on the glass substrate. Similarly, there are almost no protrusions. Therefore, the convex portion of the wiring pattern can be uniformly pressed regardless of the presence or absence of misalignment, and the flexible resin substrate and the substrate or circuit of the flat panel display type module can be formed by the anisotropic conductive adhesive film having one thickness. It can be bonded to a substrate.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for connecting flexible resin substrates according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a sectional view showing each step of the method for connecting a flexible resin substrate of the present invention.

In FIG. 1, reference numeral 1 denotes a flexible resin substrate. For example, a wiring pattern 2 is formed by laminating a Cu foil on one surface with a polyimide resin having a thickness of about 25 μm and etching the Cu foil. Has been formed.

The wiring pattern 2 is formed to have a thickness of about 35 μm, and a recess 3 is formed between the wiring patterns 2. One end side of the wiring pattern 2 formed on the flexible resin substrate 1 is connected to a wiring pattern of a flat display module such as a liquid crystal display module, and the other end side is connected to a wiring pattern 5 of the circuit board 4. As described above, the thickness of the wiring pattern of the flat display module is about 1 μm, and the thickness of the wiring pattern 5 of the circuit board 4 is about 35 μm.
It is formed in the m position. FIG. 1 shows a process diagram of a method of connecting the thickly formed wiring patterns 2 and 5 to each other.

First, one of the two substrates 1 and 4 to be connected is
Insulating resin 6 is filled in the recesses 3 between the wiring patterns of the substrates 1 and solidified (see FIGS. 1A and 1B). Here, the insulating resin 6 may be fluid as long as it has fluidity and is cured by being left standing, heated, or irradiated with ultraviolet rays, and has insulating properties. For example, it is cured at room temperature by mixing a curing agent. Epoxy resin, thermosetting epoxy resin, ultraviolet curing resin, etc. are used. Further, the amount of the insulating resin 6 applied is such that the upper surface of the wiring pattern 2 is completely covered so that the recesses 3 between the wiring patterns can be completely filled, and excess resin is removed later (see FIG. 1B). Although it is preferable that the object of the present invention is achieved, even if the concave portion 3 cannot be completely filled. Then, the resin filled in the recess 3 is cured. For example, when the above-mentioned thermosetting epoxy resin is used, it is cured by heat treatment at about 150 ° C. for about 30 minutes, and the recess 3 between the wiring patterns 2 is filled with the insulating resin 6.

Next, an anisotropic conductive adhesive film 7 is interposed between both substrates and thermocompression bonding is performed (see FIGS. 1C and 1D). Specifically, the wiring patterns 2 and 5 of both substrates 1 and 4 are aligned, and they are stacked with an anisotropic conductive adhesive film having a thickness of about 20 μm interposed therebetween, and the temperature is raised to 150 to 170 ° C. At the same time, apply a pressure of 15 to 20 kgf / cm ² and maintain this state for 30 to 40 seconds, and then crimp. In this case, both boards 1, 4
The thickness of the wiring patterns 2 and 5 formed on the
The distance between the substrates 1 and 4 after bonding is about 70 μm. However, since the concave portions 3 between the wiring patterns of the one substrate 1 are filled with the insulating resin 6, the anisotropic conductive adhesive film 7 only flows into the concave portions of the other substrate 4, and therefore the anisotropic conductivity The thickness of the adhesive film 7 may be thin. As a result, when the flat display module having a thin wiring pattern and the flexible resin substrate are bonded (the distance between the substrates is 35 to 40 μm), the conditions are almost the same, and the anisotropic conductivity is the same. Adhesive films can be used.

In the above-mentioned embodiment, the resin is filled in the concave portion on the flexible resin substrate side, but the same procedure is performed by filling the concave portion on the opposite substrate (eg, circuit board) side with resin or the like. It is the same even if formed by the method of. Also, FPC
Flexible resin substrates such as TAB and TAB can be adhered to each other.

[0016]

As described above, according to the flexible resin substrate connecting method of the present invention, an excessive pressure is applied to a part of the wiring pattern even if the two substrates are misaligned. In addition, the conductive particles are not crushed to cause poor conductivity. Further, whether it is the connection between the flexible resin substrate and the circuit board or the connection between the flexible resin substrate and the glass panel,
Since the anisotropic conductive adhesive film having the same thickness can be used for connection, it is necessary to switch the anisotropic conductive adhesive film when the flat display panel and the circuit board are bonded on both sides of the flexible resin substrate. Absent.

As a result, it is possible to obtain a flat-panel display device which can be formed at low cost and has good conductivity and improved performance.

[Brief description of drawings]

FIG. 1 is a sectional view showing each step of a method for connecting a flexible resin substrate of the present invention.

FIG. 2 is a cross-sectional view showing each step of a conventional flexible resin substrate connection method.

[Explanation of symbols]

 1 Flexible Resin Substrate 2 Wiring Pattern 3 Recess 4 Circuit Board 5 Wiring Pattern 6 Insulating Resin 7 Anisotropic Conductive Adhesive Film

Claims (1)

[Claims] 1. A wiring pattern provided on a flat display module and a wiring pattern provided on a circuit board on which a driving circuit and the like are formed are connected via a wiring pattern provided on a flexible resin substrate. A method for connecting a flexible resin substrate, comprising filling an insulating resin in the recesses between the wiring patterns provided on the flexible resin substrate or the circuit board, and then forming an anisotropic conductive adhesive film between the two substrates. A method for connecting a flexible resin substrate, characterized in that thermocompression bonding is performed with intervening.