JPH05224229A - Method for connecting liquid crystal display panel and circuit board - Google Patents

Abstract

PURPOSE:To surely interpose conductive particulates only between the connecting terminals facing each other. CONSTITUTION:Only the parts on the connecting terminals 13 among insulating adhesives 14 consisting of a photosetting type resin provided atop the connecting parts inclusive of the connecting terminals 13 of a circuit board 11 are formed as uncured parts 14b and the conductive particulates 17 are adhered and disposed only atop the uncured parts 14b by utilizing the tacky adhesiveness thereof. The rear surfaces of the connecting parts inclusive of the connecting terminals 20 of the transparent substrate 19 of a liquid crystal display panel 18 is aligned and imposed atop the conductive particulates 17 via insulating adhesives 21 provided on this rear surface. The conductive particulates are held nearly in their original positions even if the uncured parts 14b and the insulating adhesives 21 partly flow and escape when the panel is press welded and is exposed in this state. The conductive particulates 17 are, therefore, surely interposed only between the connecting terminals 13 and 20 facing each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of connecting a liquid crystal display panel and a circuit board.

[0002]

2. Description of the Related Art In a liquid crystal display device used in an electronic device such as a word processor, the connection terminals of a transparent substrate of a liquid crystal display panel and the connection terminals of a circuit board are heated with conductive fine particles made of a conductive metal or the like. In some cases, conductive connection is made via an anisotropic conductive adhesive dispersed in an insulating adhesive made of a curable or photocurable resin. In this case, an anisotropic conductive adhesive is interposed between the connection portion including the connection terminal of the transparent substrate of the liquid crystal display panel and the connection portion including the connection terminal of the circuit board, and thermocompression bonding or light irradiation is performed. When pressure bonding is applied, some of the insulating adhesive in the anisotropic conductive adhesive flows and escapes, causing some of the conductive fine particles in the anisotropic conductive adhesive to connect to the transparent substrate of the liquid crystal display panel. Both the terminals and the connection terminals of the circuit board facing the connection terminals are in contact with each other, so that the connection terminals of the transparent board of the liquid crystal display panel and the connection terminals of the circuit board facing each other are conductively connected,
Further, the insulating adhesive interposed between the adjacent conductive fine particles is cured, so that the connecting portion including the connecting terminal of the transparent substrate of the liquid crystal display panel and the connecting portion including the connecting terminal of the circuit substrate are bonded. That is, such an anisotropically conductive adhesive has conductivity in the thickness direction but has insulation in the surface direction in the connected state.

[0003]

However, in the anisotropic conductive adhesive used in such a conventional connecting method, when the conductive fine particles are dispersed in the insulating adhesive,
Generally, the conductive fine particles are mixed and kneaded in the insulating adhesive, but there is a property that the conductive fine particles are easily attached to each other and thus aggregate, and therefore the conductive fine particles are uniformly dispersed in the insulating adhesive. It is difficult to prevent the difference in the dispersion density of the conductive fine particles in the insulating adhesive, which may result in a connection failure between the opposing connection terminals or a short circuit between the adjacent connection terminals. There was a problem.
For example, as shown in FIG. 7, an anisotropic structure in which the conductive fine particles 6 are dispersed in the insulating adhesive 7 for the connection terminals 3 of the transparent substrate 2 and the connection terminals 5 of the circuit board 4 of the liquid crystal display panel 1. When conducting the conductive connection via the conductive adhesive 8, as shown on the left side of the figure, the dispersion density of the conductive fine particles 6 in the insulating adhesive 7 is too small and the connection terminals 3 and 5 face each other. When no conductive fine particles 6 are present, a connection failure occurs between the connecting terminals 3 and 5 facing each other, while the conductive fine particles 6 are dispersed in the insulating adhesive 7 as shown on the right side of FIG. When the density is too high and the conductive fine particles 6 are attached and aggregated in a daisy chain, a short circuit occurs between the adjacent connection terminals 3 and 5. An object of the present invention is to provide a method of connecting a liquid crystal display panel and a circuit board, in which conductive particles can be surely interposed only between the connection terminal of the transparent substrate and the connection terminal of the circuit board of the liquid crystal display panel facing each other. To provide.

[0004]

SUMMARY OF THE INVENTION According to the present invention, when conductively connecting a connection terminal of a transparent substrate of a liquid crystal display panel and a connection terminal of a circuit board in a state of facing each other, one of the two substrates is connected. An insulating adhesive made of a photo-curing resin is provided on the upper surface of the connection portion including the connection terminal, and the insulating adhesive located on the upper surface of the connection portion other than the connection terminals is cured by exposure, The insulating adhesive located on the upper surface of the connection terminal is uncured without being exposed, and conductive fine particles are arranged on the uncured insulating adhesive located on the upper surface of the connection terminal. The connection terminals of the other substrate of the both substrates are placed on the conductive fine particles, and the connection terminals of the one substrate and the connection terminals of the other substrate are electrically conductive by exposing the connection terminals of the other substrate by pressure bonding. Through the particles As well as electric connection is obtained by the cure the insulating adhesive of the uncured.

[0005]

According to the present invention, the insulating adhesive made of the photo-curing resin provided on the connection terminal of the one substrate is uncured, and the conductive fine particles are arranged on the uncured insulating adhesive. Then, the connection terminal of the other substrate is placed on the conductive fine particles, and when pressure bonding and exposure are performed, even if a part of the uncured insulating adhesive flows and escapes, the conductive fine particles are almost removed. Therefore, the conductive fine particles can be reliably interposed only between the connection terminal of the transparent substrate and the connection terminal of the circuit substrate of the liquid crystal display panel which are held in the same position and are opposed to each other.

[0006]

1 to 6 show respective steps of connecting a liquid crystal display panel and a circuit board in an embodiment of the present invention. Therefore, a method of connecting the liquid crystal display panel and the circuit board will be described with reference to these drawings in order.

First, a circuit board 11 as shown in FIG. 1 is prepared. The circuit board 11 has a structure in which a connection terminal 13 made of a metal such as copper or aluminum is patterned on the upper surface of a flexible board body 12 made of resin or the like with a film thickness of about 20 to 40 μm. An insulating adhesive 14 made of a photocurable resin such as ultraviolet rays is applied to the upper surface of the connection portion including the connection terminals 13 of the circuit board 11 by screen printing, letterpress printing or the like. The film thickness of the insulating adhesive 14 is about 5 μm thicker than the film thickness of the connection terminal 13 of the circuit board 11 and is about 25 to 45 μm.

Next, as shown in FIG. 2, the circuit board 11 is provided with a photomask 16 having a predetermined pattern, which has a light shielding portion 15 for shielding the portion of the circuit board 11 corresponding to the connection terminal 13.
The photomask 16 is positioned above the photomask 16 and is irradiated with light 16a such as ultraviolet light from above the photomask 16. Then, as shown in FIG. 3, a portion of the insulating adhesive 14 excluding the upper portions of the connection terminals 13 of the circuit board 11 is exposed and cured to form a cured portion 14a, and the other portion, that is, the cured portion 14a is formed. Of the insulating adhesive 14, the connection terminal 13 of the circuit board 11
The uncured portion 14b is formed while the upper part of the uncured portion remains uncured.

Next, as shown in FIG. 4, the insulating adhesive 1
The conductive fine particles 17 are arranged only on the upper surface of the uncured portion 14b of No. 4. The conductive fine particles 17 include fine particles made of conductive metal, or resin fine particles coated with a conductive thin metal film by plating, vapor deposition, or the like. As a method of disposing the conductive fine particles 17 only on the upper surface of the uncured portion 14b of the insulating adhesive 14,
A large number of conductive fine particles 17 are formed on the entire upper surface of the insulating adhesive 14.
There is a method in which the conductive fine particles 17 are adhered and arranged only on the upper surface of the uncured portion 14b having adhesiveness, and a large number of conductive fine particles 1 are formed on the entire upper surface of the insulating adhesive 14.
After spraying 7 using a spray or the like, the conductive fine particles 17 on the non-adhesive cured portion 14a are blown away by air or the like to remove the conductive fine particles 17 on the upper surface of the adhesive non-cured portion 14b. There is a method in which the fine particles 17 are attached and arranged.

Next, a liquid crystal display panel 1 as shown in FIG.
Prepare 8. The liquid crystal display panel 18 has a structure in which a connection terminal 20 made of a translucent conductor such as ITO is patterned on a lower surface of a transparent substrate 19 made of glass or resin. An insulating adhesive 21 made of a photocurable resin such as ultraviolet rays is applied to the lower surface of the connection portion of the transparent substrate 19 of the liquid crystal display panel 18 including the connection terminals 20 by printing such as screen printing or letterpress printing. ing. Then, the lower surface of the connection portion including the connection terminal 20 of the transparent substrate 19 of the liquid crystal display panel 18 is placed on the upper surface of the uncured portion 14b of the insulating adhesive 14 via the insulating adhesive 21 provided on the lower surface. The conductive fine particles 17 attached and arranged on the upper surface of the conductive fine particles 17 are aligned and placed.

Next, as shown in FIG. 6, when the circuit board 11 and the liquid crystal display panel 18 are pressure-bonded to each other and exposed to light 16a such as ultraviolet rays from above the liquid crystal display panel 18, exposure is performed. The uncured portion 14b (see FIG. 5) of the conductive adhesive 14 and each part of the insulating adhesive 21 flow and escape, so that the conductive fine particles 17 are connected to the connection terminals 20 of the transparent substrate 19 of the liquid crystal display panel 18. The connection terminal 20 and the connection terminal 13 of the circuit board 11 facing each other are brought into contact with each other, so that the connection terminal 20 of the transparent substrate 19 of the liquid crystal display panel 18 and the connection terminal 13 of the circuit board 11 which are opposite to each other are conductively connected. , The transparent substrate 19 and the connection terminal 20 are light 16
Since a is transmitted, the uncured portion 14 of the insulating adhesive 14
b (see FIG. 5) and the insulative adhesive 21 are cured and both insulative adhesives 14 and 21 are integrated, so that the connection portion including the connection terminal 20 of the transparent substrate 19 of the liquid crystal display panel 18 and the circuit board. 11 and the connection portion including the connection terminal 13 are bonded.

By the way, the uncured portion 1 of the insulating adhesive 14
4b and each part of the insulating adhesive 21 flow and escape, the conductive fine particles 17 are held in almost the same positions, and therefore the connection terminals 20 and the circuit of the transparent substrate 19 of the liquid crystal display panel 18 facing each other. The conductive fine particles 17 can be reliably interposed only between the connection terminals 13 of the substrate 11. As a result, the conductive fine particles 17 can be surely interposed between the connection terminals 20 and 13 facing each other, and eventually the connection failure can be prevented between the connection terminals 20 and 13 facing each other. Connection terminals 2 adjacent to each other
It is possible to prevent the conductive fine particles 17 from existing between 0 and 13 and to prevent a short circuit between the adjacent connection terminals 20 and 13, thus improving the reliability of anisotropic conductive connection. To do.

In the above embodiment, as shown in FIG. 2, the photomask 16 is used. However, the substrate body 12 of the circuit board 11 is made of a translucent resin such as polyethylene terephthalate or polyether sulfone. In such a case, the photomask 16 is not used, and the opaque connection terminal 13 made of metal of the circuit board 11 is used as a photomask so that the light 16a such as ultraviolet rays is irradiated from below the circuit board 11. Good. Further, in the above embodiment, as shown in FIG. 4, the connection terminal 13 of the circuit board 11 is
The uncured portion 14b is provided on the upper surface of the conductive fine particles 1 and the conductive fine particles 17 are arranged on the upper surface of the uncured portion 14b.
Liquid crystal display panel 1 with insulating adhesive 21 on the upper surface of 7.
Although the connection portion including the connection terminal 20 of the transparent substrate 19 of No. 8 is placed, on the contrary, the uncured portion is provided on the upper surface of the connection terminal 20 of the transparent substrate 19 of the liquid crystal display panel 18, and The conductive fine particles may be arranged on the upper surface of the cured portion, and the connection portion including the connection terminals 13 of the circuit board 11 may be placed on the upper surface of the conductive fine particles via an insulating adhesive.
The circuit board 11 does not have to be a flexible board and may be a hard board.

[0014]

As described above, according to the present invention, the insulating adhesive made of the photo-curing resin provided on the connection terminal of the one substrate is uncured, and the uncured insulating adhesive is Since the conductive fine particles are arranged on the upper side, even if a part of the uncured insulating adhesive flows and escapes, the conductive fine particles can be held in almost the same position, and therefore the liquid crystal facing each other can be held. The conductive fine particles can be reliably interposed only between the connection terminals of the transparent substrate of the display panel and the connection terminals of the circuit board, and the reliability of anisotropic conductive connection can be improved.

[Brief description of drawings]

FIG. 1 is a cross section of a state in which an insulating adhesive made of a photocurable resin is provided on the upper surface of a connection portion including a connection terminal of a circuit board when connecting a liquid crystal display panel and a circuit board according to an embodiment of the present invention. Fig.

FIG. 2 is a cross-sectional view of a state in which light is irradiated on the insulating adhesive provided on the circuit board using a photomask during the connection.

FIG. 3 is a cross-sectional view showing a state in which a cured portion and an uncured portion are formed on an insulating adhesive provided on a circuit board by light irradiation during the same connection.

FIG. 4 is a cross-sectional view showing a state in which conductive fine particles are adhered and arranged only on an upper surface of an uncured portion of an insulating adhesive provided on a circuit board during the same connection.

FIG. 5 is a cross-sectional view showing a state in which a lower surface of a connecting portion including a connecting terminal of a transparent substrate of a liquid crystal display panel is placed on an upper surface of conductive fine particles through an insulating adhesive provided on the lower surface during the same connection. ..

FIG. 6 is a cross-sectional view showing a state in which the connection terminals of the transparent substrate of the liquid crystal display panel and the connection terminals of the circuit board are conductively connected during the same connection.

FIG. 7 is a cross-sectional view shown for explaining the problems of the conventional example.

[Explanation of symbols]

 11 Circuit Board 13 Connection Terminal 14 Insulating Adhesive 14b Uncured Part 17 Conductive Fine Particles 18 Liquid Crystal Display Panel 19 Transparent Substrate 20 Connection Terminal 21 Insulating Adhesive

Claims (1)

[Claims] 1. When conductively connecting a connection terminal of a transparent substrate of a liquid crystal display panel and a connection terminal of a circuit substrate in a state of being opposed to each other, a connection portion including a connection terminal of one of the two substrates is connected. An insulating adhesive made of a photo-curable resin is provided on the upper surface, and the insulating adhesive located on the upper surface of the connection portion other than the connection terminals is cured by exposure and located on the upper surface of the connection terminals. The insulating adhesive is uncured without being exposed to light, conductive fine particles are arranged on the uncured insulating adhesive located on the upper surface of the connection terminal, and the both substrates are provided on the conductive fine particles. The connection terminal of the other substrate is placed on the other substrate, and the connection terminal of the one substrate and the connection terminal of the other substrate are conductively connected through the conductive fine particles by exposing the connection terminals of the other substrate by pressure bonding and exposing. ,Previous Curing the uncured insulating adhesive, method of connecting the liquid crystal display panel and the circuit board, characterized in that.