JPS61259406A - Anisotropic conductive sheet and manufacture thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (a) Industrial Application Field The present invention relates to an anisotropically conductive sheet used as an electrical bonding material for flexible circuits, etc., and particularly to an anisotropic conductive sheet using an organic conductive material as the conductive material. The present invention relates to a conductive sheet and a method for manufacturing the same.

(b) Conventional technology Anisotropically conductive sheets that have conductivity only in the thickness direction of the sheet can be used for high-density connectors, such as connections between printed wiring boards and 7-rat cables, and connections between printed wiring boards and LSI packages. It is used for connections etc.

Such an anisotropically conductive sheet may be one in which a plurality of conductive metal fine powders are dispersed in an insulating sheet made of rubber or synthetic resin in a plurality of rows in the thickness direction of the sheet, or conductive fibers. It is known that the material is embedded in the thickness direction of the sheet.

(e) Problem to be solved by the invention In the former anisotropically conductive sheet, when the sheet is brought into contact with a printed circuit board, etc., the pressure causes contact between the fine metal powders arranged in the thickness direction of the sheet. different degrees,
Since the electric resistance fluctuates greatly in the sheet thickness direction, and metal is used as the conductive material, it is unavoidable that the weight of the anisotropically conductive sheet increases.

Furthermore, the latter anisotropically conductive sheet also has a problem of large fluctuations in electrical resistance. This problem with this sheet is thought to be due to its manufacturing method. This sheet is produced by dispersing conductive fibers in an insulating material before curing, orienting the conductive fibers, then curing the insulating material, and slicing the cured product across the orientation direction of the conductive fibers. It is obtained by It is preferable to perform the slicing operation perpendicular to the orientation direction of the conductive fibers in order to make each fiber in the slicing plane upright with respect to several planes, but some inclination is unavoidable in actual operations. be. Therefore, in the anisotropically conductive sheet obtained by this method, the degree of exposure of the conductive fibers on the slice plane is uneven, or the fibers are inclined, resulting in large fluctuations in electrical resistance. Furthermore, in the above manufacturing method, it is not only difficult to arrange and orient the conductive fibers and to slice the cured product, but also requires complicated equipment, and there are some HIMs in which productivity is poor.

Furthermore, in this type of anisotropic conductive sheet, the conductive am is easily broken during handling or processing, so metal conductive fibers with high mechanical strength are generally used. , it is impossible to avoid increasing the weight of this sheet.

In addition, both of the anisotropically conductive sheets mentioned above have parts that are partially covered by the base material forming the sheet, and as a result, conductivity in the thickness direction is completely lost in those parts. There was a problem.

(d) Means for Solving the Problem The present inventors have discovered that the sheet can be manufactured easily without requiring any special equipment or technology, has good productivity, and that the resistance in the thickness direction of the sheet is the same as that of the printed wiring. We have worked hard to develop an anisotropically conductive sheet that remains almost constant even when the contact pressure with a substrate changes.

As a result, an anisotropically conductive sheet formed by holding an electrochemically or chemically generated organic conductive material in the through holes of a porous sheet having a large number of through holes in the thickness direction is lightweight; Moreover, they discovered that the electrical resistance was stable.
This has led to the completion of the present invention.

That is, the first gist of the present invention is that a porous sheet having a large number of through holes in the thickness direction has an organic conductive material held in the through holes in the thickness direction of the sheet. It is.

The porous sheet used in the present invention is electrically insulating,
It is a sheet with many through holes in the thickness direction,
The material is not particularly limited as long as it can be formed into a sheet, and organic materials such as synthetic resins and rubber, and inorganic materials such as glass and ceramics can be used.

The above rubber includes natural rubber or various synthetic rubbers, such as
Examples include polybutanoene rubber, nitrile butadiene rubber, styrene butadiene rubber, silicone resin, polyurethane resin, and the like.

The synthetic resins include both thermoplastic resins and thermosetting resins, such as polyolefin, polyethylene terephthalate, polyacrylonitrile, polyacrylonitrile, polyvinyl chloride, polyester resin, acrylic resin, polyamide, polycarbonate resin, and polyester resin. 7-cetal resin, polystyrene resin, ABS resin, 7-fluorinated olefin represented by polytetrafluoroethylene (hereinafter referred to as PTFE), polyvinylidene heptadide, unsaturated polyester resin, 7-ether resin, urea resin , melamine resin, guanamine resin, etc.

The method for manufacturing the above porous sheet includes elution method, solvent-
Among known porous sheet manufacturing methods such as a non-solvent method, an emulsion method, a radiation irradiation method, a sintering method, and a stretching method, the most suitable method may be employed depending on the material used.

The pore diameter of the porous sheet is 0.01 to 1000 μm,
The thickness is preferably 1 to 100 μm.

Further, the above-mentioned organic conductive material refers to an organic conductive substance produced electrochemically or chemically.

Methods for forming organic conductive materials include substances produced electrochemically or chemically by oxidation/condensation, radical polycondensation, cationic polycondensation, anionic polycondensation, etc., but in particular, conjugated Polymeric materials are preferred because they have excellent electrical properties.

Examples of the above-mentioned conjugated polymer substances include polyacetylene, poly(1,6-heptadiyne), polypyrrole, folychenylene, polyphenylene, poly(para-phenylenevinylene), poly(para-7-22lene sulfite), poly(
(meta-phenylene sulfide), poly(para-phenylene oxide), polyfuran and derivatives thereof.

The organic conductive material used in the present invention is particularly preferably one in which an electron-accepting or electron-donating reagent is added (doped) to the above-mentioned organic conductive material.

Examples of electron-accepting reagents include halogen (C12°Br2
．． I 2. I CZ, I C1-1I Br), P F
s, A sF sr S bF sr A gC(1
Perchlorate such as 04, AgBF=, B F-9B C
13-B r-sulfuric acid, hydrogen halide, and the like.

For doping, the reagent may be directly reacted with the organic conductive material (the conductive material in the sheet) (so-called chemical doping), but in particular, the sheet holding the conductive material may be reacted with 1 to 50% by weight, preferably Preferably, it is doped electrochemically in a solution of 5 to 20% by weight of sulfuric acid, hydrogen halide, potassium halide, or organic/inorganic perchlorate.

Further, examples of the electron-donating reagent include alkali metals, quaternary amines, and the like.

Doping involves first reacting an alkali metal with another organic compound (eg naphthalene) in tetrahydrofuran. Preferably, a method is employed in which a complex (naphthalene complex) is synthesized and a sheet holding the organic conductive material is immersed in the complex.

The second gist of the present invention relates to a method of electrochemically manufacturing an anisotropically conductive sheet. This will be explained in detail below.

That is, the second gist of the present invention is to dissolve an electrochemically active monomer in a solvent, and in this solution, a porous sheet having a large number of through holes in the thickness direction is formed on the working electrode plate. A counter electrode is provided with the reference electrode as a reference, and electrolysis is carried out, whereby the organic conductive material electrochemically generated within the through hole is held within the through hole.

The solvent used in the present invention is used as an electrolyte and is not particularly limited, and examples include water, alcohols, ketones, nitriles, esters, alkali metal salts thereof, or mixtures thereof. Can be mentioned.

In the present invention, it is preferable that an electrolyte be present in the reaction system in order to improve conductivity during electrolytic polycondensation.

Examples of the electrolyte include halogen compounds, perchlorates, carbonates, and bicarbonates of lithium, sodium, and potassium, as well as methylates, ethylates, and amine salts.

Among these, halogen compounds and perchlorates are particularly preferred since they also act as doping agents.

Also, electrochemically active monomers are electrochemically active monomers.
Monomers that cause condensation reactions include acetylene, pyrrole, aniline, thiophene, furan, indole, azulene, and derivatives thereof.

Next, the electrode material used in the present invention will be explained.

First, working electrode materials include, for example, nickel, nickel alloys, stainless steel, carbon, lead dioxide, RuOx type oxide anodes, platinum, platinum alloys, and if desired, lead, lead alloys, and even iron/iron alloys. Among these, platinum and platinum alloys are most preferred from the viewpoint of electrochemical stability.

In addition, various metal materials such as nickel, nickel alloy, stainless steel, iron, iron alloy, titanium, platinum, and platinum alloy can be used as the counter electrode, but platinum and platinum alloy are particularly preferred from the viewpoint of electrochemical stability. Most preferred.

As the power source for electrolytic heavy condensation, either a constant voltage power source or a constant current power source can be used, and if desired, a potential scanning type power source can also be used.

As for the electrolytic conditions, the current density is usually 0.01 to 101
00O/co+2, preferably 1-50LllA/C
The temperature of the electrolyte is usually O~50℃.
, preferably at a temperature of 0 to 25°C.

As the electrolytic cell used for the electrolytic polycondensation of the present invention, a wide variety of those used for ordinary organic electrode reactions can be used.For example, beaker-shaped or box-shaped electrolytic cells can also If the electrostatic sheet does not have sufficient electrical properties, or if desired, the sheet may be doped with the above-mentioned electron-accepting substance or electron-donating substance by the above-mentioned method to improve the electrical properties (lower electrical resistance). It is preferable to improve

The third aspect of the present invention relates to a method of chemically manufacturing an anisotropically conductive sheet instead of the electrochemical method in the second invention.

That is, the third gist of the present invention is that a porous sheet having a large number of through holes in the thickness direction is impregnated with a chemically polycondensable monomer into each of the through holes, and then the monomer is The present invention is characterized in that an organic conductive material chemically produced within the through-hole by adding a reaction aid is retained within the through-hole.

This will be explained in detail below.

Examples of chemically polycondensable monomers used in this invention include aniline hydrochloride, pyrrole, acetylene, benzene biphenyl, and para-terphenyl.

Further, the reaction aid is a substance having a function of causing the monomer to undergo a polycondensation reaction, and includes, for example, a catalyst, a reaction initiator, and a reaction promoter.

Specific examples of this auxiliary agent include sulfuric acid aqueous solutions of dichromates such as potassium dichromate and sodium dichromate, ferric chloride, chromium dioxide, cerium sulfate, potassium hepterythyanide, ferric sulfate, Potassium sulfate, benzoquinone, H2P tC1,.

Ti(OClHs)-A1(CzHs)i-AICb
Examples include CuCl2, AsF7, etc., and two or more of these may be used if desired.

Then, the porous sheet is prepared such that the concentration of the monomer is 1 to 1.
The porous sheet is immersed in a 50% by weight solution or a solution of the above monomer is dropped onto the porous sheet to impregnate and retain the monomer in each through hole of the porous sheet. Next, this sheet is put into the reaction accelerator, or the reaction accelerator is dropped onto the sheet, and the sheet is reacted at a reaction temperature of 0 to 50°C for 10 seconds to 5 hours, and then washed and dried. Obtain an anisotropic conductive sheet.

Furthermore, the anisotropically conductive sheet thus obtained may be doped with an electron-accepting substance or an electron-donating substance in the same manner as described above, if desired, to improve its electrical properties.

(e) Function The anisotropic conductive sheet of the present invention is extremely lightweight because it uses an organic conductive material, and since the organic conductive material is held in each through-hole of the porous sheet, There is no risk that the conductive material will be covered with the base material, and the conductive material in the form of fine particles is not connected in the thickness direction of the sheet.
Since a single organic conductive material is held in each through hole of the sheet, the resistance in the thickness direction is approximately constant even if the contact pressure between the anisotropic conductive sheet and the electrode group of the printed wiring board etc. changes. That's why.

(f) Examples Examples of the present invention will be shown below, but the present invention is not limited thereto.

Example 1 Aniline hydrochloride aqueous solution (concentration of aniline in the solution was 10% by weight) was placed in a box-shaped non-diaphragm electrolytic cell with a volume of 500 m1.
Pour 400ml of

A polycarbonate membrane with a pore diameter of 0.2 μm and a thickness of 10 μm as a porous sheet (manufactured by GE, trade name: Nuclebore)
The sheet was cut into 5c+n squares, and this sheet was brought into contact with a platinum plate (5, Ocm x 5, Ocm) with a thickness of 0.5 mm, and the sheet was inserted into the electrolytic cell.

This was used as the working electrode, and the unidirectional metal plate was used as the counter electrode, at a temperature of 25°C.
Electrolysis was carried out for 30 minutes under constant current conditions (current density 5 mA/am2) while stirring with a magnetic cooler to retain the organic conductive material in the through holes, and then washed with water.
Dry.

The current-carrying area of the working electrode was 25 cm+''.

The electrical properties of the anisotropically conductive sheet thus obtained are shown in Table 1.

Example 2 Aniline hydrochloride-methanol solution instead of the aniline hydrochloride aqueous solution in Example 1? An anisotropically conductive sheet was obtained in the same manner as in Example 1 except that [l (the concentration of aniline in the solution was 10% by weight) was used.

The electrical properties of this anisotropic conductive sheet are shown in Table fJIJ1.

Example 3 In place of the aniline hydrochloride aqueous solution in Example 1, a pyrrole-acetonitrile solution (the concentration of pyrrole in the solution was 5% by weight) was used, and tetrabutylammonium verchloride was added to this to increase the concentration of pyrrole in the entire electrolyte solution. An anisotropic conductive sheet was obtained in the same manner as in Example 1, except that the concentration of tetrabutylammonium verchloride was adjusted to 0.1% by weight.

The electrical properties of this anisotropically conductive sheet are shown in Table 1.

Example 4 An anisotropic conductive sheet was obtained in the same manner as in Example 2, except that a polytetrafluoroethylene sheet (hereinafter referred to as PTFE sheet) with a pore diameter of 50 μm and a thickness of 25 μm was used as the porous sheet.

The electrochemical properties of this anisotropically conductive sheet are shown in Table 1.

Example 5 Aniline hydrochloride in a box-shaped container with a capacity of 500+nff1
Nitethanol solution (the concentration of aniline in the solution is 10%)
).

PTF as a porous sheet with a pore diameter of 50 μm and a thickness of 25 μm
Cut the E sheet into 5 ca + square pieces, put it into the above container and impregnate it with the above solution, then take out the sheet, drop the following sulfuric acid aqueous solution of potassium dichromate, and heat it to a temperature of 25 The organic conductive material was retained in the through-holes of the sheet by reacting at .degree. C. for 10 minutes.

Blend ratio (weight ratio) Potassium dichromate 5 Sulfuric acid 15 Water 75 The electrical properties of the anisotropically conductive sheet thus obtained are shown in Table 1.

Table 1 Note 1) The anisotropic conductive sheet of each example was placed on a flat brass plate as a resistance electrode in the sheet thickness direction, and a 4-point probe (needle electrode thickness 0.75 mm) was placed on the surface of the sheet. , distance between needle electrodes 3 I'll, in series), connect one needle electrode and a brass flat plate electrode to a digital multimeter (TR6855 manufactured by Takegu Riken Co., Ltd.), and read the resistance. Next, disconnect the needle electrode from the meter, connect the other needle electrode to the terminal, and read the resistance. In this way, four points are measured for one sample. The number of samples was five for each example product.

Note 2) Electrical resistance in the plane direction Width lll is etched on the copper foil epoxy printed circuit board.
An insulating gap of l11 is provided, the anisotropically conductive sheet of each example product is placed on top of this, a flat plastic plate is brought into contact with it under a load of 1 kg, and the resistance value is measured by connecting it to a digital multimeter. was measured.

(g) Effects of the Invention The anisotropically conductive sheet of the present invention uses an organic conductive material, and since the organic conductive material is lightweight and is easily compatible with the base material, it can be easily increased in density.

Further, since the anisotropically conductive sheet of the present invention has an organic conductive material held in the through holes of the insulating porous sheet,
The conductive material is not covered with an insulating base material at all, and as a result, problems such as poor conductivity do not occur, and the conductive material is composed of a single conductive polymer substance. Even if the contact pressure fluctuates, the resistance in the thickness direction of the anisotropic conductive sheet remains approximately constant, and ultimately the electrical characteristics are stabilized by the combination of the two.

In addition, the anisotropically conductive sheet of the present invention can be easily produced electrochemically or chemically without the need for conventional complicated equipment or techniques, and the electrical resistance of the sheet can be easily produced by electrochemical or chemical methods. It can be significantly reduced by doping with an electron-accepting substance or an electron-donating substance, either selectively or chemically.

In particular, the method of electrochemically manufacturing an anisotropically conductive sheet is extremely economical because the generation of an organic conductive material and the doping of the conductive material can be performed simultaneously.

Claims (10)

[Claims] (1) An anisotropic conductive sheet characterized in that a porous sheet having a large number of through holes in the thickness direction has an organic conductive material held in the through holes in the thickness direction of the sheet. (2) The anisotropically conductive sheet according to claim 1, wherein the porous sheet is made of an organic material such as synthetic resin or rubber, or an inorganic material such as ceramics or glass. . (3) The anisotropically conductive sheet according to claim 1, wherein the organic conductive material is made of a conjugated polymer substance. (4) The above conjugated polymer substance is polyacetylene, poly(
1,6-heptadiyne), polypyrrole, polythienylene, polyphenylene, poly(para-phenylene sulfide), poly(meta-phenylene sulfide), poly(para-phenylene oxide), and polyfuran. An anisotropically conductive sheet according to claim 3. (5) The anisotropically conductive sheet according to claim 4, wherein the conjugated polymer substance is doped with an electron-accepting substance or an electron-donating substance. (6) dissolving an electrochemically active monomer in a solvent;
In this solution, a porous sheet having many through holes in the thickness direction is brought into contact with the working electrode plate, a counter electrode is provided with the reference electrode as a reference, and electrolysis is carried out. 1. A method for manufacturing an anisotropically conductive sheet, characterized in that an organic conductive material produced by the method is held in the through-holes. (7) The method for producing an anisotropically conductive sheet according to claim 6, wherein the monomer is acetylene, pyrrole, aniline, thiophene, furan, indole, azulene, or a derivative thereof. (8) A porous sheet having a large number of through holes in the thickness direction is impregnated with a chemically polycondensable monomer into each of the through holes, and then a reaction aid for the above monomer is added. A method for manufacturing an anisotropically conductive sheet, characterized in that an organic conductive material chemically generated within the through-holes is retained within the through-holes. (9) The method for producing an anisotropically conductive sheet according to claim 8, wherein the monomer is aniline hydrochloride. (10) The method for producing an anisotropically conductive sheet according to claim 9, wherein the reaction accelerator is an aqueous sulfuric acid solution of dichromate.