JP2003297516A - Connection method of flexible board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent an overflow of excess resin in connecting a flexible board with a counterpart board through a thermosetting anisotropic conductive resin and to obtain a stronger mechanical connection. <P>SOLUTION: In crimping with heat a flexible board 10 made by coating an electrode-lead forming face of a base film 11 with an insulating resist film 13 with a counterpart board by removing the insulating resist film 13 by a given width from a board end part 10a to have a part of an electrode lead of the electrode-forming face exposed and coating a thermosetting anisotropic conductive resin A on the exposed face of the electrode lead, a range of coating of the thermosetting anisotropic conductive resin A on the exposed face of the electrode lead is to be away from both sides of the board end part 10a and film end part 13a of the insulating resist film 13 within the range of 0.1 to 0.5 mm, and at the same time, a thermosetting insulating resin B is to be coated thicker than the coating thickness of the thermosetting anisotropic conductive resin A by 0.01 to 0.05 mm between the thermosetting anisotropic conductive resin A and the film end part 13a. <P>COPYRIGHT: (C)2004,JPO

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 flexible substrate, and more particularly, to a method of connecting a flexible substrate to another circuit board or liquid crystal panel by using a thermosetting anisotropic conductive resin. It is about.

[0002]

2. Description of the Related Art In many cases, a flexible substrate is used as a relay substrate for connecting electric parts to each other. Figure 4
As shown in the plan view of FIG. 4A and the sectional view of FIG. 4B, the flexible substrate 10 has an electrode lead 12 formed on a flexible base film 11 made of, for example, a polyimide resin. Are covered with an insulating resist film 13.

The connecting means may be a conductive rubber connector, soldering, thermosetting anisotropic conductive resin, or the like. To collectively connect a large number of electrodes arranged at a relatively narrow pitch, thermosetting is used. Anisotropic conductive resins are often used.

The thermosetting anisotropic conductive resin is, for example, an epoxy or acrylic thermosetting resin in which fine conductive particles obtained by plating a conductive sphere such as gold on a plastic sphere are mixed. It has adhesiveness and conductivity.

When the thermosetting anisotropic conductive resin is used to connect to the other substrate, the insulating resist film 13 is removed from the substrate end of the flexible substrate 10 by a predetermined width to expose a part of the electrode lead 12. The thermosetting anisotropic conductive resin A is uniformly applied to the exposed surface of the electrode lead. The coating thickness varies depending on whether the other party is a circuit board or a liquid crystal panel, but is usually about 0.015 to 0.03 mm.

Then, as shown in FIG. 5, the flexible substrate 10 is superposed on the terminal portion 21 of the liquid crystal panel, for example, through the thermosetting anisotropic conductive resin A, and the thermocompression bonding head is overlaid thereon with the cushion material 31 interposed therebetween. 30 is pressed with a predetermined pressure.

As a result, the resin flows and the layer thickness of the thermosetting anisotropic conductive resin becomes thin, and the electrode lead 12 on the flexible substrate 10 side and the electrode lead (not shown) of the terminal portion 21 are electrically connected via the conductive particles. And the flexible substrate 10 and the terminal portion 21 are mechanically connected by the hardening of the resin.

[0008]

FIG. 6 shows a state after connection by thermocompression bonding. When the thermocompression bonding is performed, excess anisotropic conductive resin causes excess anisotropic conductive resin on the substrate end side and / or the end surface of the terminal portion 21. It may protrude from the side.

If the resin protruding from the substrate end of the flexible substrate 10 adheres to the cushion material 31, the resin must be removed or the cushion material 31 must be replaced each time, which impedes productivity. Further, if foreign matter such as dust adheres to the cushion material 31, the foreign matter may come into contact with the conductive particles in the protruding resin and conduct electricity between the adjacent electrode leads, resulting in a defective product.

Further, when the resin protrudes from the end face side of the terminal portion 21, the conductive particles in the protruded resin may aggregate between the electrode leads 12 of the flexible substrate 10 and cause a short circuit between the leads.

The flexible substrate 10 has a terminal portion 21.
Although it is bent in a predetermined direction after being connected to, the adhesive force of only the anisotropic conductive resin A may lose the stress at that time and peel off the adhesive portion.

The present invention has been made to solve the above-mentioned problems, and an object thereof is to prevent excess resin from squeezing out when connecting a flexible substrate to a counter substrate through a thermosetting anisotropic conductive resin. In addition, it is to provide a method of connecting a flexible substrate that enables stronger mechanical connection.

[0013]

In order to achieve the above object, the present invention provides the insulating resist film from the substrate end portion of a flexible substrate in which the electrode lead forming surface of the base film is covered with the insulating resist film. A part of the electrode lead on the surface where the electrode lead is formed is exposed by removing a predetermined width in parallel with the end portion, and a thermosetting anisotropic conductive resin is applied to the exposed surface of the electrode lead and thermocompression bonding is performed on the mating substrate. In the substrate connecting method, the application range of the thermosetting anisotropic conductive resin on the exposed surface of the electrode lead is separated by 0.1 to 0.5 mm from both sides of the substrate end and the film end of the insulating resist film. While applying the thermosetting anisotropic conductive resin within the range, at least between the thermosetting anisotropic conductive resin and the film end portion a thermosetting insulating resin is applied to the thermosetting anisotropic resin. 0.01 than the coating thickness of the conductive resin
It is characterized in that it is heated and pressure-bonded in a state of being applied in a thickness of 0.05 mm.

As described above, the thermosetting anisotropic conductive resin is not applied to the entire surface of the exposed surface of the electrode lead but from 0.1 to 0.5 mm from both sides of the substrate end of the flexible substrate and the film end of the insulating resist film. Since the coating is performed within the range that enters the inside, there is no risk of the resin squeezing out during thermocompression bonding. Moreover, since the adhesive strength of the thermosetting anisotropic conductive resin is reinforced by the thermosetting insulating resin, peeling of the flexible substrate can be prevented.

In order to obtain higher adhesive strength, a thermosetting insulating resin is further added between the thermosetting anisotropic conductive resin and the film end of the insulating resist film by 0.1 to 0.5 mm. It is preferable that the coating is applied on the film.
Moreover, by using the same resin as the resin component of the thermosetting anisotropic conductive resin as the thermosetting insulating resin, the thermosetting insulating resin and the thermosetting anisotropic conductive resin can be integrated during thermocompression bonding. You can

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described with reference to FIGS. Figure 1 (A),
4B is a plan view and a sectional view of a flexible substrate 10 similar to FIGS. 4A and 4B, FIG. 2 is an explanatory view at the time of thermocompression bonding corresponding to FIG. 5, and FIG. It is explanatory drawing after thermocompression-bonding corresponding to the above-mentioned FIG. It should be noted that the same reference numerals are used for the portions that do not need to be changed from the conventional example described above.

When the flexible substrate 10 is connected to the counter substrate using the thermosetting anisotropic conductive resin, the insulating resist film 1 is applied from the substrate end 10a of the flexible substrate 10.
3 is removed in parallel with the substrate end portion 10a by a predetermined width to expose a part of the electrode lead 12 on the end portion side.

Then, the thermosetting anisotropic conductive resin A is uniformly applied to the exposed surface of the electrode lead, but in the present invention, the thermosetting anisotropic conductive resin A is not applied to the entire exposed surface of the electrode lead. The specific area of the exposed surface of the electrode lead.

The specific range means the flexible substrate 10.
Substrate end 10a and insulating resist film 13 film end 1
It is within a range of 0.1 to 0.5 mm apart from both sides of 3a. The coating thickness of the thermosetting anisotropic conductive resin A varies depending on whether the other party is a circuit board or a liquid crystal panel, as in the above-mentioned conventional example, but may be about 0.015 to 0.03 mm.

After applying the thermosetting anisotropic conductive resin A, in the present invention, the thermosetting insulating resin B is provided between the thermosetting anisotropic conductive resin A and the film end portion 13a of the insulating resist film 13. Than the coating thickness of the thermosetting anisotropic conductive resin A is 0.01 to 0.
Apply 05mm thick.

Since the thermosetting insulating resin B enhances the connection strength of the flexible substrate 10, the thermosetting insulating resin B is further applied on the insulating resist film 13 by 0.1 to 0.1%.
It is preferable to apply it so that it takes 0.5 mm.

Further, during thermocompression bonding, thermosetting insulating resin B
In order to make the mechanical strength more effective by integrating the thermosetting anisotropic conductive resin A and the thermosetting anisotropic conductive resin A, the same resin as the thermosetting anisotropic conductive resin A is used for the thermosetting insulating resin B. Is preferred.

That is, when the resin component of the thermosetting anisotropic conductive resin A is an epoxy resin, the thermosetting insulating resin B is used.
The resin component of is also the same epoxy resin. Further, in order to make the thickness of the connecting portion uniform after pressure bonding, the thermosetting insulating resin B
Insulating particles such as plastic spheres having the same particle size as the conductive particles contained in the thermosetting anisotropic conductive resin A may be mixed therein.

Thereafter, as shown in FIG. 2, the flexible substrate 10 is overlaid on the terminal portion 21 of the liquid crystal panel, for example, with the thermosetting anisotropic conductive resin A interposed therebetween, and the cushion material 31 is used for thermocompression bonding thereon. The head 30 is pressed with a predetermined pressure.

FIG. 3 shows a state after connection by thermocompression bonding. According to the present invention, the thermosetting anisotropic conductive resin A is added to the substrate end 10a of the flexible substrate 10 and the film end 13a of the insulating resist film 13. From both sides of 0.1 to 0.
Since the coating is carried out within a range of 5 mm apart, there is almost no possibility that the surplus of the thermosetting anisotropic conductive resin A will squeeze out during thermocompression bonding.

Further, the thermosetting anisotropic conductive resin A and the thermosetting insulating resin B are simultaneously melted by heating by the thermocompression bonding head 30 and integrated with the resin component of the thermosetting anisotropic conductive resin A. Therefore, the mechanical connection strength between the flexible substrate 10 and the terminal portion 21 of the liquid crystal panel is increased.

When the thermosetting anisotropic conductive resin A and the thermosetting insulating resin B are applied by screen printing, the applied thickness can be easily controlled by the thickness of the screen printing plate and / or the printing speed.

[0028]

As described above, according to the present invention,
A part of the electrode lead on the electrode lead forming surface is exposed by removing the insulating resist film by a predetermined width from the substrate end of the flexible substrate formed by covering the electrode lead forming surface of the base film with the insulating lead film. When the thermosetting anisotropic conductive resin is applied to the exposed surface and thermocompression-bonded to the other substrate, the application range of the thermosetting anisotropic conductive resin to the exposed surface of the electrode lead is set to the substrate end and the film end of the insulating resist film. The thermosetting anisotropic conductive resin is applied within a range of 0.1 to 0.5 mm from each side, and at least a thermosetting insulating resin is applied between the thermosetting anisotropic conductive resin and the film end portion. 0.0 than the coating thickness of the thermosetting anisotropic conductive resin
By applying heat and pressure in the state of applying 1 to 0.05 mm thick, it is possible to prevent excess resin from squeezing out when connecting the flexible substrate to the counter substrate through the thermosetting anisotropic conductive resin, and to make it stronger. A good mechanical connection can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an application range of a thermosetting anisotropic conductive resin on an electrode lead forming surface of a flexible substrate in the present invention.

FIG. 2 is an explanatory view showing a state in which the flexible substrate according to the present invention is thermocompression bonded to a counter substrate.

FIG. 3 is an explanatory view showing a state after thermocompression bonding of the present invention.

FIG. 4 is an explanatory diagram showing a coating range of a thermosetting anisotropic conductive resin on an electrode lead forming surface of a flexible substrate in a conventional example.

FIG. 5 is an explanatory view showing a thermocompression bonding state of the flexible substrate to the counterpart substrate in the above conventional example.

FIG. 6 is an explanatory view showing a state after thermocompression bonding in the conventional example.

[Explanation of symbols]

10 Flexible substrate 10a substrate edge 11 Base film 12 electrode lead 13 Insulating resist film 13a membrane end 21 LCD panel 30 Thermocompression bonding head 31 cushion material A Thermosetting anisotropic conductive resin B thermosetting insulating resin

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 2H092 GA48 GA50 MA32 NA18                 5E085 BB09 BB19 CC01 DD06 EE12                       FF11 JJ36 JJ38                 5E344 AA02 AA22 BB02 BB04 CC13                       CD04 DD06 EE16 EE21 EE23

Claims (3)

[Claims] 1. An electrode lead is formed by removing a predetermined width of the insulating resist film from a substrate end of a flexible substrate formed by coating an electrode lead forming surface of a base film with an insulating resist film. In the method for connecting a flexible substrate, in which a part of the electrode lead on the surface is exposed, and a thermosetting anisotropic conductive resin is applied to the exposed surface of the electrode lead and thermocompression bonding is performed on the mating substrate, While applying the anisotropic conductive resin, the thermosetting anisotropic conductive resin is applied within a range of 0.1 to 0.5 mm apart from both sides of the substrate end and the film end of the insulating resist film. A thermosetting insulating resin between the thermosetting anisotropic conductive resin and the film end portion at least 0.01 to 0.05 mm thicker than the coating thickness of the thermosetting anisotropic conductive resin. Connection of the flexible substrate, characterized by heat pressing while cloth. 2. The thermosetting insulating resin is further added between the thermosetting anisotropic conductive resin and the film end portion in an amount of 0.1 to 0.1.
The flexible substrate connecting method according to claim 1, wherein the flexible substrate is applied so as to cover the insulating resist film by 0.5 mm. 3. The method for connecting a flexible substrate according to claim 1, wherein the same resin as the resin component of the thermosetting anisotropic conductive resin is used as the thermosetting insulating resin.