JPH08273441A - Anisotropic electric conduction film and its preparation - Google Patents

Abstract

PURPOSE: To provide an anisotropic conductive film that has sufficient anisotropy and higher conductivity for its reliable contact, and its manufacturing method. CONSTITUTION: An anisotropic conductive film is manufactured by coating a thermoplastic film 1 with separable protective films 2 and 3 on both sides, forming holes 4 through the coated film 1, and filling the holes 4 with a conductive substance 5. Upon its usage, after the separation of the protective films 2 and 3, the conductive film is fixed by thermo-compression bonding to objects to be connected together, which are then interconnected in the film thickness direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for connecting a precision electronic component having a narrow space between conductors and a substrate, such as connecting an FPC to a substrate or connecting an LCD substrate to a driver.
The present invention relates to an anisotropic conductive film having conductivity only in the film thickness direction and a manufacturing method thereof.

[0002]

2. Description of the Related Art The anisotropic conductive film currently used is one in which conductive particles or fibers are dispersed in an adhesive binder resin. Such an anisotropic conductive film can be manufactured at low cost and can easily connect conductors such as opposed electrodes arranged at fine intervals, but on the other hand, it can be contained in order to exhibit anisotropy. It was necessary to limit the amount of conductive particles, and it was essentially impossible to obtain high conductivity. In addition, a high pressure must be applied during the pressure bonding in order to remove the binder existing around the conductive particles. Therefore, the adherend is required to have strong mechanical properties, which narrows the range of application.

On the other hand, a conductive film of a type in which a large amount of conductive particles are dispersed in an elastic body can be connected at a relatively low pressure, but its own conductivity is isotropic, or At present, the anisotropy is not so large that it is considered that the adjacent terminals are insulated from each other. In addition, since this type of conductive film has the characteristic that the connection changes greatly depending on the compression pressure, the conductive elastic body is inserted in the vertical direction of the housing to connect between the opposing conductors. There is known a method of filling the core with anisotropy (US Patent No.
No. 4,770,641), the disclosed method not only requires a means for fixing to the upper and lower objects to be connected, but also has a larger connectable pitch as compared with the anisotropic conductive film. Therefore, an object of the present invention is to provide an anisotropic conductive film having high conductivity while having sufficient anisotropy, capable of obtaining a highly reliable connection by easy connection, and an anisotropic conductive film corresponding to a narrow pitch. It is to provide a manufacturing method.

[0004]

According to the present invention, a thermoplastic film, a protective film releasably arranged on both sides of the thermoplastic film, and the thermoplastic film and the protective film are penetrated in the thickness direction. Provided is an anisotropic conductive film having a conductive substance filled in a hole portion, which is peeled off a protective film at the time of use and thermocompression-bonded to an object to be connected to electrically connect in a film thickness direction. To do.

Furthermore, the present invention further comprises a step of arranging a protective film on both surfaces of the thermoplastic film so that the protective film can be peeled off, a step of forming a hole portion penetrating the thermoplastic film and the protective portion, and an elastic member in the hole portion. A method of manufacturing an anisotropic conductive film, which comprises the step of filling a conductive material having

As a result of repeated studies on the structure for solving these problems, the inventors sandwiched a film 1 made of a thermoplastic material with peelable protective films 2 and 3 (Step 1, drawing 1 (a)), multiple holes 4 through the membrane
Is formed (step 2, drawing 1 (b)), and the hole 4 is filled with a conductive material 5 having elasticity (step 3, drawing 1 (c)) to obtain excellent anisotropy and high conductivity. It has been found that an anisotropic conductive film having good properties and easy to attach and connect is manufactured. The anisotropic conductive film is peeled off the protective films 2 and 3 prior to use (step 4, FIG. 2 (a)), and thermocompression bonded to the object to be connected (step 5,
It is actually used by referring to FIGS. 2 (a) to 2 (c).

Here, as the thermoplastic substance 1, ethylene vinyl acetate copolymer (EVA) and styrene-butadiene rubber (S) which are generally used as hot melt adhesives are used.
In addition to BR), polyamide (PA), and the like, any thermoplastic resin such as thermoplastic polyimide (TPI), thermoplastic urethane (TPU), and polyetherimide (PEI) can be used.

As the peelable protective films 2 and 3, any one can be used, but it goes without saying that an appropriate one should be selected depending on the adhesiveness with the thermoplastic resin.

The formation of the hole 4 in the step 2 can be performed by using a usual processing means. That is, a method using punching, a method using a drill, a method using a laser, a method using chemical and physical etching, and the like,
The method using laser or etching is advantageous for forming holes at short intervals, and punching or drilling is advantageous in terms of cost. Therefore, the most suitable method according to the required diameter and interval of holes. Should be selected. The diameter and spacing of the holes are determined by the width and spacing of the conductor of the object to be connected (hereinafter referred to as the deposited conductor), but the diameter of the holes must be smaller than the narrowest spacing between the deposited conductors. And it is desirable that it is half or less. Also,
It is necessary that the distance between the holes is smaller than the narrowest distance between the adhered conductors, and it is also preferable that the distance is 1/2 or less.

As for the filling of the substance 5 in the step 3, all the commonly known methods can be applied, but the optimum method should be selected depending on the kind of the filler. When the substance consists of a mixture of thermosetting resin such as silicone rubber and conductive particles or fibers, fill the hole by a method such as squeeze method of filling the uncured mixture into the hole with squeeze, and then heat. The method of curing is effective. In this case, examples of the conductive particles include metal particles and non-conductive particles substantially covered with a metal film.

When the substance is a conductive polymer having a conjugated double bond, it can be polymerized electrically or chemically in the pores. Examples of polymers that can be used at this time include polyacetylene, polypyrrole, polythienylene, polyphenylene, and poly (phenylene vinylene).
Etc. and derivatives thereof. Further, these polymers may be doped with an electron accepting substance (acceptor) or an electron donating substance (donor). Examples of the electron-accepting substance that can be used in this case include halogen, phosphorus pentafluoride, arsenic pentafluoride, boron trifluoride, boron trichloride, boron tribromide, sulfuric acid, hydrogen halide and the like. . Further, examples of the electron donating substance that can be used in this case include alkali metals and quaternary amines.

When the substance is a mixture of a polymer having a conjugated double bond and a thermosetting resin, the thermosetting resin is filled in the pores by the method described above, and then the conductive material described above is used. A method of obtaining a mixture by polymerizing a monomer having penetrated into a resin by polymerizing a polymer having a, or a conductive polymer powder obtained by a known method in advance is mixed with an uncured thermosetting resin raw material. However, it can be obtained by, for example, a method of heating and curing after filling the holes.

When the substance is a metal, a method of precipitating and filling the metal in the pores by a chemical or electrical reaction can be used. For example, it is possible to fill the inside of the hole with metal by sticking a copper film on one surface of the film, performing electrolytic plating using this as an electrode, and then removing the copper film by etching.

It should be noted that the holes need not be completely filled with the conductive material. By making the intervals of the holes formed in step 2 narrower than the lengths and intervals of the adhered conductors, a plurality of conductive substances contribute to electrical connection between the adhered conductors. Therefore, the object of step 3 can be achieved if one or more holes are filled with the conductive material per the deposited conductor.

[0015]

EXAMPLES The preferred examples of the anisotropic conductive film and the method for producing the same according to the present invention will be shown below, but the present invention is not limited to the following description and can be variously modified and modified by those skilled in the art.

[0016]

Example 1 Polyamide film 3 (thickness 50 μm) coated with a release agent in advance was coated with polyamide hot melt adhesive 1 by heating, and then polyester film 2 (thickness 50 μm) was laminated by hot pressing. A three-layer film composed of polyester (protective film) -polyamide (thermoplastic film) -polyester (protective film) was prepared.

A large number of holes (holes) 4 having a diameter of 0.6 mm were formed in this three-layer film at a pitch of 1.2 mm in length and width by a punching method, and then silver powder (average particle size 10 μm) was used as the conductive material 5.
Of 80% by weight) was added by a squeeze method to an addition-curable silicone rubber (SE-1740 manufactured by Dow Corning Toray Co., Ltd.). The obtained film is heated at 85 ° C for 30 minutes,
The resin was cured. When the obtained film was observed by an electron microscope, it was found that a film having a structure in which the silver powder-containing silicone rubber 5 was filled in the holes 4 of the film was obtained.

After cutting the three-layer film into 5 mm × 30 mm, the polyester films 2 and 3 on both sides of the three-layer film were peeled off to form comb-shaped electrodes (adhered conductors) 22 at a pitch of 1.2 mm. It was sandwiched between a substrate 21 and an FPC 23 having electrodes (deposited conductors) 24 of the same pitch, pressurized at 200 ° C. for 10 seconds, then unloading and cooling to perform thermocompression bonding.

When the connection resistance between the opposing electrodes was measured, it was 10 mΩ. Moreover, the adjacent electrodes were substantially insulated from each other.

[0020]

[Example 2] Holes (holes) 4 having a diameter of 0.06 mm were formed in the three-layer film used in Example 1 by a laser processing method in a vertical and horizontal pitch.
After forming a large number of 0.12 mm, an addition-curable silicone rubber (SE-1740 manufactured by Dow Corning Toray Co., Ltd.) containing 80% by weight of silver powder (average particle size: 2 μm) was filled as a conductive substance 5 by a squeeze method. The resulting film at 85 ° C
Heated for 30 minutes to cure the resin. When the obtained film was observed by an electron microscope, it was found that a film having a structure in which the silver powder-containing silicone rubber 5 was filled in the holes 4 of the film was obtained.

After cutting this three-layer film into 5 mm × 30 mm, the polyester film on the layers on both sides of the film was peeled off and the same as the substrate 21 on which comb-shaped electrodes (adhered conductors) 22 were formed at a pitch of 0.2 mm. F having pitch electrodes (deposited conductors) 24
It was sandwiched between PC22, pressurized at 200 ° C. for 10 seconds, and then unloaded and cooled to perform thermocompression bonding.

The connection resistance between the opposing electrodes was measured and found to be 60 mΩ. Moreover, the adjacent electrodes were substantially insulated from each other.

For comparison with Examples 1 and 2, a commercially available anisotropic conductive film (3370C manufactured by ThreeBond) was used.
Was sandwiched between two printed circuit boards that had been heated to 250 ° C. in advance, and pressure bonding was performed for 20 seconds under a pressure of 5 kg / cm ² . After cooling the substrate, the electrical resistance value between the upper and lower sides was measured and it was in a substantially insulated state.

[0024]

According to the present invention, in a thermoplastic film sandwiched between two peelable protective films, a hole penetrating the film is formed, and the hole is filled with a conductive substance. An anisotropic conductive film, which is a film formed by removing the protective film and thermocompression-bonding the film when used, provides the following effects because the anisotropic conductive film is provided.

(1) Since the protective film is peeled off at the time of use, the thermoplastic film is protected before peeling, and the adhered conductors are connected by thermocompression bonding, so that highly reliable connection can be easily achieved. .

(2) When the protective film is peeled off, the projection of the conductive material having elasticity projects from the surface of the thermoplastic film, and this projection contributes to the connection, so that a more reliable connection is realized. Furthermore, the force required for connection is the sum of the force required to compress the conductive material and the force required to bond the thermoplastic resin, and this value is the same as the conventional anisotropic method that requires large amounts of resin to be removed. Significantly smaller than the force required for a conductive film. Therefore, it is possible to electrically connect the adherend that has low mechanical strength and is easily deformed by compression.

(3) The connection is achieved under compressive stress, and this state is retained as it is by the adhesive, so that it is possible to continue to have stable and high conductivity.

(4) By forming the holes filled with the conductive material at an appropriate interval, it is possible to cope with the case where the interval between the adhered conductors varies.

(5) As the conductive material with which the hole is filled, a material in which elasticity and conductivity are freely adjusted can be used from a relatively wide selection range.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a process for producing an anisotropic conductive film of the present invention, in which (a) is a view showing a film in which a protective film is attached to a thermoplastic film. (B) is a diagram showing a state in which holes are formed in the film of (a), and (c) is a diagram showing a state in which the holes formed in (b) are filled with a conductive substance.

2A and 2B are cross-sectional views showing a method of connecting an anisotropic conductive film of the present invention to an object to be connected, wherein FIG. 2A is a view showing a state in which a protective film is peeled off, and FIG. The figure which shows the state which has arrange | positioned the electrically conductive film opposite to an to-be-connected object. (C) is a figure which shows the connection state of an anisotropic conductive film.

[Explanation of symbols]

 1 Thermoplastic film 2, 3 Protective film 4 Hole 5 Conductive substance 21, 23 Connected object (FPC, substrate, etc.)

Claims (2)

[Claims] 1. A thermoplastic film, a protective film releasably disposed on both sides of the thermoplastic film, and a conductive material filled in a hole penetrating the thermoplastic film and the protective film in a film thickness direction. An anisotropic conductive film comprising a substance, which is peeled off from the protective film at the time of use and thermocompression-bonded to an object to be connected to perform electrical connection in the film thickness direction. 2. A step of arranging a protective film on both sides of a thermoplastic film in a releasable manner, a step of forming a hole portion penetrating the thermoplastic film and the protective film, and an electrically conductive material having elasticity in the hole portion. Of an anisotropic conductive film, which comprises a step of filling a conductive material.