JP2002057189A - Anisotropic conductive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anisotropic conductive sheet, which shows conductivity in the state of no pressure or in the state of pressing in the direction of the thickness with a small power and shows conductivity higher than that in the state of no pressure or in the state of pressing in the direction of the thickness with the small power in the state of pressing in the direction of the thickness with a great power. SOLUTION: In this anisotropic conductive sheet, a large number of conductive path forming parts, which are extended in the direction of the thickness, containing conductive particles showing magnetism in an elastomer in the state of orienting these particles in the direction of the thickness are located while being mutually separated in the direction of plane through a stationary conductive part and at least one surface of the stationary conductive part is formed while being protruded from the surface of the conductive path forming part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anisotropic conductive sheet having conductivity in a thickness direction.

[0002]

2. Description of the Related Art An anisotropic conductive elastomer sheet has conductivity only in the thickness direction, or has a pressurized conductive portion which has conductivity only in the thickness direction when pressed in the thickness direction. And it is possible to achieve a compact electrical connection without using means such as soldering or mechanical fitting, and it is possible to absorb mechanical shocks and strains and make a soft connection Because of these features, using such features, for example, computers,
In the fields of electronic digital watches, electronic cameras, computer keyboards, etc., it is widely used as a connector for achieving an electrical connection between circuit devices, for example, a printed circuit board and a leadless chip carrier, a liquid crystal panel, etc. ing.

In electrical inspection of a circuit device such as a printed circuit board or a semiconductor integrated circuit, an electrode to be inspected formed on one surface of a circuit device to be inspected and an electrode formed on the surface of the inspection circuit substrate. In order to achieve electrical connection with the test electrode, an anisotropic conductive elastomer sheet is interposed between the test electrode region of the circuit device and the test electrode region of the test circuit board. I have.

Heretofore, as such anisotropic conductive elastomer sheets, those having various structures are known. For example, as an anisotropic conductive elastomer sheet showing conductivity in the absence of pressure, a sheet base made of insulating rubber, conductive fibers arranged in a state of being oriented to extend in the thickness direction, carbon Conductive rubber containing black or metal powder and insulating rubber alternately laminated along the surface direction (Japanese Patent Laid-Open No. 50-94495)
For example, are known. On the other hand, as an anisotropic conductive elastomer sheet which exhibits conductivity when pressed in the thickness direction, a sheet obtained by uniformly dispersing metal particles in an elastomer (see JP-A-51-93393), A plurality of conductive path forming portions extending in the thickness direction and an insulating portion for insulating these from each other are formed by distributing the non-uniform magnetic material particles in the elastomer (JP-A-53-147772). Japanese Patent Application Laid-Open No. 61-250906 discloses a structure in which a step is formed between the surface of a conductive path forming portion and an insulating portion.

[0005]

However, in the field of electronic parts or electronic parts applied equipment, in the field of no pressure or in the state of being pressed in the thickness direction with a small force,
A certain degree of conductivity in the thickness direction (for example, a volume resistivity of 1
× 10 ⁷ to 1 × 10 ¹² Ω · m), and in a state of being pressed in the thickness direction with a large force, a higher conductivity (for example, volume resistivity) than a state of no pressure or a state of being pressed with a small force Is 1 × 10 ⁻² to 1 × 10 ⁷ Ω · m), but such an anisotropic conductive elastomer sheet is not known until now.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to show conductivity in a state where no pressure is applied or in a state where a small force is applied in the thickness direction and to provide a large force. An object of the present invention is to provide an anisotropic conductive sheet that exhibits higher conductivity when pressed in the thickness direction with no pressure or when pressed in the thickness direction with a small force.

[0007]

The anisotropic conductive sheet of the present invention comprises a large number of conductive particles extending in the thickness direction, wherein the conductive particles exhibiting magnetism are contained in the elastomer in a state of being aligned in the thickness direction. The path forming portion is disposed apart from each other in the surface direction via a stationary conductive portion made of a conductive elastomer, and the stationary conductive portion is in a state where at least one surface thereof protrudes from the surface of the conductive path forming portion. It is characterized by being formed.

In the anisotropic conductive sheet according to the present invention, the conductive elastomer constituting the stationary conductive portion is preferably a nonmagnetic conductive material dispersed in an insulating elastomer. The conductivity-imparting substance is preferably at least one substance selected from a substance exhibiting conductivity by itself and a substance exhibiting conductivity by absorbing moisture. Further, the volume resistivity of the conductive elastomer constituting the stationary conductive portion is 1 × 10 ⁷
It is preferably about 1 × 10 ¹² Ω · m. It is preferable that both surfaces of the stationary conductive portion are formed so as to protrude from the surface of the conductive path forming portion. In addition, it is preferable that the protruding height of the stationary conductive portion from the surface of the conductive forming portion or the total height thereof is 5 to 50% of the thickness of the stationary conductive portion.

[0009]

According to the anisotropic conductive sheet of the present invention, the surface of the stationary conductive portion is formed so as to protrude from the surface of the conductive path forming portion. In the non-pressurized state) or in a state where the stationary conductive part is pressed in the thickness direction by a small force by the connected body, the connected body does not contact the conductive path forming part, and as a result, the stationary conductive part It shows conductivity according to the electrical characteristics of the conductive elastomer constituting the stationary conductive portion. Moreover, in a state where the stationary conductive portion is pressed in the thickness direction by a large force by the connected body, the stationary conductive portion is greatly compressed, and the connected body comes into contact with the conductive path forming portion. The path forming part is pressurized, and as a result, the conductive path forming part includes:
Since a conductive path extending in the thickness direction is formed by the chain of the conductive particles, the conductivity is higher than in a non-pressurized state or a state in which the conductive particles are pressed in the thickness direction with a small force.

[0010]

Embodiments of the present invention will be described below in detail. FIG. 1 is an explanatory cross-sectional view showing a configuration of an example of the anisotropic conductive sheet of the present invention.
FIG. 2 is an explanatory sectional view showing a part of the anisotropic conductive sheet shown in FIG. 1 in an enlarged manner. The anisotropic conductive sheet 10 includes a plurality of conductive path forming portions 11 each extending in the thickness direction, in which conductive particles P exhibiting magnetism are densely contained in a conductive elastomer. Each of the portions 11 is arranged in a plane direction at a regular interval, for example, at regular intervals via a stationary conductive portion 12 made of a conductive elastomer. Each of the conductive path forming portions 11 contains the conductive particles P in a state of being oriented so as to be arranged in the thickness direction. The stationary conductive portion 12 is formed such that its upper surface and lower surface protrude from each of the upper surface and lower surface of the conductive path forming portion 11.

As the conductive elastomer constituting the conductive path forming portion 11 and the stationary conductive portion 12, a material obtained by dispersing a nonmagnetic conductivity-imparting substance in an insulating elastomer can be suitably used. As the insulating elastomer for constituting the conductive elastomer, a polymer substance having a crosslinked structure is preferable. Various materials can be used as the curable polymer substance forming material that can be used to obtain the crosslinked polymer substance, and specific examples thereof include polybutadiene rubber, natural rubber, polyisoprene rubber, and styrene- Conjugated diene rubbers such as butadiene copolymer rubber and acrylonitrile-butadiene copolymer rubber and hydrogenated products thereof, and block copolymers such as styrene-butadiene-diene block copolymer rubber and styrene-isoprene block copolymer Rubber and their hydrogenated products, chloroprene, urethane rubber,
Examples include polyester rubber, epichlorohydrin rubber, silicone rubber, ethylene-propylene copolymer rubber, ethylene-propylene-diene copolymer rubber, and the like. In the above, when the obtained anisotropic conductive sheet 10 is required to have weather resistance, it is preferable to use a material other than the conjugated diene rubber. In particular, from the viewpoint of moldability and electrical characteristics, silicone rubber is used. Preferably, it is used.

[0012] The silicone rubber is preferably one obtained by crosslinking or condensing a liquid silicone rubber. The liquid silicone rubber preferably has a viscosity of 10 ⁵ poise or less at a strain rate of 10 ⁻¹ sec, and may be any of condensation type, addition type, and those containing a vinyl group or a hydroxyl group. Good. Specifically, dimethylsilicone raw rubber, methylvinylsilicone raw rubber, methylphenylvinylsilicone raw rubber and the like can be mentioned.

Among these, liquid group-containing silicone rubber (vinyl group-containing polydimethylsiloxane)
Is usually obtained by subjecting dimethyldichlorosilane or dimethyldialkoxysilane to hydrolysis and condensation reaction in the presence of dimethylvinylchlorosilane or dimethylvinylalkoxysilane, for example, followed by fractionation by repeated dissolution-precipitation. Also,
The liquid silicone rubber containing vinyl groups at both ends is anionically polymerized with a cyclic siloxane such as octamethylcyclotetrasiloxane in the presence of a catalyst, and uses, for example, dimethyldivinylsiloxane as a polymerization terminator and other reaction conditions (for example, , The amount of the cyclic siloxane and the amount of the polymerization terminator). Here, as a catalyst for anionic polymerization, alkali such as tetramethylammonium hydroxide and n-butylphosphonium hydroxide or a silanolate solution thereof can be used. The reaction temperature is, for example, 80 to 130 ° C. Such a vinyl group-containing polydimethylsiloxane preferably has a molecular weight Mw (weight average molecular weight in terms of standard polystyrene; the same applies hereinafter) of 10,000 to 40,000. In addition, from the viewpoint of heat resistance of the obtained conductive path element, the molecular weight distribution index (the value of the ratio Mw / Mn between the standard polystyrene-equivalent weight average molecular weight Mw and the standard polystyrene-equivalent number average molecular weight Mn; the same applies hereinafter) is 2. The following are preferred.

On the other hand, liquid silicone rubber containing hydroxyl groups (hydroxyl group-containing polydimethylsiloxane) is usually prepared by hydrolyzing dimethyldichlorosilane or dimethyldialkoxysilane in the presence of dimethylhydrochlorosilane or dimethylhydroalkoxysilane. And condensation reaction, for example,
It is obtained by performing fractionation by repeating precipitation.
Further, cyclic siloxane is anionically polymerized in the presence of a catalyst, and dimethylhydrochlorosilane, methyldihydrochlorosilane or dimethylhydroalkoxysilane is used as a polymerization terminator, and other reaction conditions (for example, the amount of the cyclic siloxane and the polymerization termination) are used. Amount of agent)
Can also be obtained by appropriately selecting Here, as a catalyst for anionic polymerization, alkali such as tetramethylammonium hydroxide and n-butylphosphonium hydroxide or a silanolate solution thereof can be used. The reaction temperature is, for example, 80 to 130 ° C. Such hydroxyl group-containing polydimethylsiloxane is,
It is preferable that the molecular weight Mw is 10,000 to 40,000. Further, from the viewpoint of heat resistance of the obtained conductive path element, those having a molecular weight distribution index of 2 or less are preferable.
In the present invention, either one of the above-mentioned vinyl group-containing polydimethylsiloxane and hydroxyl group-containing polydimethylsiloxane can be used, or both can be used in combination.

In the present invention, an appropriate curing catalyst can be used to cure the polymer substance-forming material. As such a curing catalyst, an organic peroxide, a fatty acid azo compound, a hydrosilylation catalyst, or the like can be used. Specific examples of the organic peroxide used as the curing catalyst include benzoyl peroxide, bisdicyclobenzoyl peroxide, dicumyl peroxide, and ditertiary butyl peroxide. Specific examples of the fatty acid azo compound used as a curing catalyst include azobisisobutyronitrile. Specific examples of the catalyst which can be used as a catalyst for the hydrosilylation reaction include chloroplatinic acid and salts thereof, a siloxane complex containing a platinum-unsaturated group, a complex of vinylsiloxane and platinum, and platinum and 1,3-divinyltetramethyldisiloxane. And a complex of triorganophosphine or phosphite with platinum, acetylacetate platinum chelate, and a complex of cyclic diene and platinum. The amount of the curing catalyst used is appropriately selected in consideration of the type of the polymer substance-forming material, the type of the curing catalyst, and other curing treatment conditions. 15 parts by weight.

As the nonmagnetic conductivity-imparting substance powder for constituting the conductive elastomer, a substance exhibiting conductivity by itself (hereinafter, also referred to as a "self-conductive substance"), or a substance which becomes conductive by absorbing moisture. A substance that is expressed (hereinafter, also referred to as a “hygroscopic conductive substance”) or the like can be used,
Either one of these self-conductive substance and hygroscopic conductive substance can be used, or both can be used in combination.

As the self-conductive substance, generally, a substance exhibiting conductivity by free electrons in a metal bond, a substance in which charge transfer occurs due to movement of surplus electrons, and a substance in which charge transfer occurs due to movement of vacancies And an organic polymer substance having a π bond along the main chain and exhibiting conductivity by the interaction thereof, and a substance which causes charge transfer by the interaction of a group in a side chain. Specifically, non-magnetic metals such as platinum, gold, silver, copper, aluminum, manganese, zinc, tin, lead, indium, molybdenum, niobium, tantalum, chromium; copper dioxide, zinc oxide, tin oxide, titanium oxide, etc. Non-magnetic conductive metal oxides; conductive fiber materials such as whisker, potassium titanate, and carbon; semiconductive materials such as germanium, silicon, indium phosphorus, and zinc sulfide; carbon-based materials such as carbon black and graphite; polyacetylene Polymer, a conductive polymer material such as a heterocyclic polymer such as a polyphenylene-based polymer and a thiophenylene-based polymer, and these can be used alone or in combination of two or more as a conductivity-imparting substance. it can.

As the moisture-absorbing conductive substance, a substance that generates ions and carries charges by the ions, a substance having a group having a large polarity such as a hydroxyl group or an ester group, or the like can be used. Specifically, cation-forming substances such as quaternary ammonium salts and amine compounds; aliphatic sulfonates, higher alcohol sulfates, higher alcohol ethylene oxide addition sulfates, higher alcohol phosphates, Substances which generate both anions such as higher alcohol ethylene oxide addition phosphoric acid ester salts; Substances which generate both cations and anions such as bedyne compounds; Silicon compounds such as chloropolysiloxane, alkoxysilane, alkoxypolysilane and alkoxypolysiloxane , Conductive urethane,
High molecular substances such as polyvinyl alcohol or a copolymer thereof, higher alcohols such as ethylene oxide, polyethylene glycol fatty acid esters and polyhydric alcohol fatty acid esters, and substances having large polar groups such as polysaccharides are used. These can be used alone or in combination of two or more as a conductivity-imparting substance.

Further, among the above-mentioned moisture-absorbing conductive substances, they have high heat resistance and good compatibility with elastic polymer substances.
Aliphatic sulfonates are preferred in that they do not cause polymerization inhibition in the formation of the elastic polymeric material. Such aliphatic sulfonates include 1-decane sulfonate and 1-decane sulfonate.
Undecane sulfonate, 1-dodecane sulfonate,
1-tridecane sulfonate, 1-tetradecane sulfonate, 1-pentadecane sulfonate, 1-hexadecane sulfonate, 1-heptadecane sulfonate, 1
Those having an alkyl group having 10 to 20 carbon atoms, such as -octadecanesulfonic acid salt, 1-nonadecanesulfonic acid salt, 1-eicosandecasulfonic acid salt, and isomers thereof are preferable. As the salt, an alkali metal salt such as lithium, sodium, and potassium is preferable, and a sodium salt is particularly preferable because it has higher heat resistance.

The proportion of the conductivity-imparting substance in the conductive elastomer is appropriately set according to the type of the conductivity-imparting substance and the intended degree of conductivity. When used alone, 1 to 10% by weight, preferably 2 to 8% by weight,
When a substance made of a nonmagnetic conductive metal oxide is used alone as the conductivity-imparting substance, 10 to 40% by weight, preferably 20 to 30% by weight, and a substance made of a conductive fiber substance as the conductivity-imparting substance is used. When used alone, 5-3
0% by weight, preferably 8 to 15% by weight. When carbon black is used alone as the conductivity-imparting substance, it is 10 to 40% by weight, preferably 20 to 30% by weight. 10 to 30% by weight, preferably 15 to 25% by weight when the substance made of a conductive polymer substance is used alone, and 2 to 40% by weight when the hygroscopic conductive substance is used alone as the conductivity-imparting substance. %, Preferably in the range of 3 to 30% by weight. In the case where the above-mentioned various conductivity-imparting substances are used in combination, the ratio is set in consideration of the above range.

The conductive elastomer may contain an inorganic filler such as ordinary silica powder, colloidal silica, airgel silica, and alumina, if necessary. By including such an inorganic filler, the thixotropy of the material for forming the anisotropic conductive sheet 10 is ensured, the viscosity thereof is increased, and the dispersion stability of the conductive particles is improved. Thus, the anisotropic conductive sheet 10 having high strength is obtained. The use amount of such an inorganic filler is not particularly limited, but using a large amount is not preferable because the orientation of the conductive particles cannot be sufficiently achieved by the magnetic field.

Such a conductive elastomer has a body
Product specific resistance is 1 × 10⁷~ 1 × 10 ¹²Ω ・ m
And more preferably 1 × 10⁸~ 1 × 10¹¹Ω
M, particularly preferably 1 × 10⁹~ 1 × 10^TenΩ ・ m
is there.

The conductive particles P contained in the conductive path forming portion 11 exhibit magnetism from the viewpoint that they can be easily aligned in the thickness direction of the anisotropic conductive sheet 10 by applying a magnetic field. Conductive particles are used. Specific examples of such conductive particles P include particles made of a metal exhibiting magnetism such as nickel, iron, and cobalt, particles made of an alloy thereof, particles containing these metals, or core particles containing these metals. ZrFe in which the surface of the core particles is plated with a conductive metal such as gold, silver, palladium, and rhodium which is difficult to oxidize;
₂ , FeBe ₂ , FeRh, MnZn, Ni ₃ Mn, F
eCo, FeNi, Ni ₂ Fe, MnPt ₃ , FeP
d, FePd ₃ , Fe ₃ Pt, FePt, CoPt, C
Particles made of a ferromagnetic intermetallic compound such as oPt ₃ or Ni ₃ Pt, or these particles are used as core particles, and the surfaces of the core particles are plated with a conductive metal such as gold, silver, palladium, or rhodium which is difficult to oxidize. Chemical formula: M ¹ OF
e ₂ O ₃ (where M ¹ is Mn, Fe, Ni, Cu, Z
Metals such as n, Mg, Co, and Li are shown. ) Or a mixture thereof (for example, Mn-Z
n ferrite, Ni-Zn ferrite, etc.), FeMn
Manganites such as ₂ O ₄ , chemical formula: M ² O · Co ₂ O
₃ (where M ² represents a metal such as Fe or Ni), cobaltite, Ni _0.5 Zn _0.5 Fe ₂ O ₄ ,
Ni _0.35 Zn _0.65 Fe ₂ O ₄ , Ni _0.7 Zn _0.2 Fe
_0.1 Fe ₂ O ₄ , Ni _0.5 Zn _0.4 Fe _0.1 Fe ₂ O ₄
Particles made of a ferromagnetic metal oxide such as, or particles obtained by using the particles as core particles and plating the surfaces of the core particles with a conductive metal such as gold, silver, palladium, or rhodium that is difficult to oxidize; Particles made of inorganic materials such as particles, glass beads, carbon, or particles made of polymers such as polystyrene cross-linked with polystyrene and divinylbenzene are used as core particles, and a conductive magnetic material such as nickel or cobalt is formed on the surface of the core particles. Examples include a body-plated body, and a core particle coated with both a conductive magnetic substance and a conductive metal that is hardly oxidized. Further, these conductive particles may have an insulating film formed on the surface for the purpose of adjusting the conductivity. Here, as the insulating film, an inorganic material such as a metal oxide or a silicon oxide compound, or an organic material such as a resin or a coupling agent can be used. In the above, the means for coating the surface of the core particles with the conductive metal is not particularly limited, but may be, for example, chemical plating or electrolytic plating.

In the case where the conductive particles P are formed by coating the surface of a core particle with a conductive metal, from the viewpoint of obtaining stable conductivity over a long period of time, the surface of the particle is coated with the conductive metal. The ratio (the ratio of the conductive metal covering area to the surface area of the core particles) is preferably 40% or more, more preferably 45% or more, and particularly preferably 47 to 95%. Further, the amount of the conductive metal to be coated is appropriately set according to the intended conductivity of the anisotropic conductive sheet 10, but is preferably 0.5 to 50% by weight of the core particles, more preferably. 1 to 30% by weight, more preferably 3 to 25% by weight, particularly preferably 4 to 20% by weight
% By weight. When the conductive metal to be coated is gold, the coating amount is preferably 2.5 to 30% by weight of the core particles, more preferably 3 to 20% by weight, and further preferably 3.5. ~ 15% by weight, particularly preferably 4 ~
10% by weight. When the conductive metal to be coated is silver, the coating amount is 3 to 50% by weight of the core particles.
It is preferably 4 to 40% by weight, more preferably 5 to 30% by weight, particularly preferably 6 to 20% by weight.

The number average particle diameter of the conductive particles P is 1
The thickness is preferably from 1000 to 1000 m, more preferably from 2 to 500 m, still more preferably from 5 to 300 m, and particularly preferably from 10 to 200 m. Further, in the obtained anisotropic conductive sheet 10, when the distance between the conductive paths formed in the thickness direction by the conductive particles P is small, that is, when high resolution anisotropic conductive characteristics are required. As the conductive particles P, those having a small number average particle diameter are preferably used, and specifically, those having a number average particle diameter of 1 to 20 μm, particularly preferably 1 to 10 μm are preferably used. In addition, the particle size distribution (D
w / Dn) is preferably 1 to 10, more preferably 1.01 to 7, and further preferably 1.05 to
5, particularly preferably 1.1 to 4. By using the conductive particles satisfying such conditions, the obtained anisotropic conductive sheet 10 can be easily deformed under pressure,
Further, sufficient electrical contact between the conductive particles can be obtained. The shape of the conductive particles P is not particularly limited. However, since the conductive particles P can be easily dispersed in the polymer substance-forming material, they have a spherical shape, a star shape, or a shape in which these are aggregated. It is preferably a lump formed by the secondary particles.

The water content of the conductive particles P is preferably at most 5%, more preferably at most 3%, further preferably at most 2%, particularly preferably at most 1%. By using the conductive particles satisfying such conditions, it is possible to prevent or suppress the generation of bubbles during the curing treatment of the polymer substance forming material.

The ratio of the conductive particles P in the conductive path forming portion 11 is appropriately selected according to the purpose of use of the anisotropic conductive sheet 10 and the type of the conductive particles used.
15 to 50%, preferably 20 to 40 in volume fraction
%. If this ratio is less than 15%, it may be difficult to form a conductive path having sufficiently small electric resistance. on the other hand,
If this ratio exceeds 50%, the resulting conductive path forming portion 11 may be fragile.

The degree of conductivity of the conductive path forming portion 11 is appropriately set according to the purpose of use of the anisotropic conductive sheet 10. Specifically, the conductive path forming portion 11 has a strain rate of 5%. In the state where pressure is applied in the thickness direction as described above, the volume resistivity of the conductive path forming portion 11 in the thickness direction is 1 × 10
⁻⁴ to 1 × 10 ⁸ Ω · m, more preferably 1 × 10 ⁻³ to 1 × 10 ⁷ Ω · m, and particularly preferably 1 × 10 ⁻² to 1 × 10 ⁶ Ω · m. m. In order to obtain such conductivity, the type of the conductive particles P to be used may be selected and the content ratio of the conductive particles may be adjusted.

The diameter and the arrangement pitch of the conductive path forming portions 11 are appropriately set according to the purpose of use of the anisotropic conductive sheet 10. For example, the diameter of the conductive path forming portion 11 is 0.05 to 1 m at a point where the portion 11 is securely contacted with the connected body.
m, preferably 0.08 to 0.5 mm, and the arrangement pitch of the conductive path forming portions 11 is 0.1 to 2.54 mm, preferably 0.15 to 1 mm. The ratio of the area of the surface of the conductive path forming portion 11 to the surface of the anisotropic conductive sheet 10 is appropriately set according to the purpose of use of the anisotropic conductive sheet 10. It is preferably 40 to 80%, particularly preferably 50 to 70%, from the viewpoint that the conductive path forming portion 11 is reliably brought into contact with the connected body when pressed.

The protruding heights h1 and h2 of the stationary conductive portion 12 from the upper and lower surfaces of the conductive path forming portion 11 are appropriately set according to the intended use of the anisotropic conductive sheet 10. Height h1 from the upper surface of the conductor and conductive path forming portion 1
1 + h2 (h1 + h2)
Is preferably 5 to 50% of the thickness d of the stationary conductive portion 12, more preferably 10 to 40%, and particularly preferably 20 to 30%. If the protruding height of the stationary conductive portion 12 is too small, the conductive path forming portion 11 comes into contact with the connected body even when the connecting body is pressurized with a small pressing force. May not be obtained. On the other hand, when the protruding height of the stationary conductive portion 12 is excessively large, the conductive path forming portion 11 does not come into contact with the connected body even if the connection body is pressurized with a considerably large pressing force,
Expected conductivity may not be obtained. The thickness of the stationary conductive portion 12 is, for example, 0.02 to 2 mm, and preferably 0.05 to 0.5 mm.

The anisotropic conductive sheet 10 as described above can be manufactured, for example, by the following method. FIG.
FIG. 2 is an explanatory cross-sectional view showing a configuration of an example of a mold for manufacturing the anisotropic conductive sheet of the present invention. The mold 20 is configured such that an upper mold 21 and a lower mold 26 that is a pair with the upper mold 21 are arranged to face each other via a frame-shaped spacer 25. In the upper die 21, a ferromagnetic layer 23 is formed on the lower surface of the ferromagnetic substrate 22 according to a pattern opposite to the arrangement pattern of the intended conductive path forming portions 11 of the anisotropic conductive sheet 10. A non-magnetic layer 24 having a thickness smaller than that of the ferromagnetic layer 23 is formed in a portion other than the magnetic layer 23. On the other hand, in the lower mold 26, a ferromagnetic layer 28 is formed on the upper surface of the ferromagnetic substrate 27 in accordance with the same pattern as the arrangement pattern of the intended conductive path forming portions 11 of the anisotropic conductive sheet 10. In places other than the ferromagnetic layer 28, the ferromagnetic layer 28
A non-magnetic layer 29 having a smaller thickness is formed. As a material forming the ferromagnetic substrates 22, 27 and the ferromagnetic layers 23, 28 in each of the upper mold 21 and the lower mold 26, iron, nickel, cobalt, or an alloy thereof can be used. In addition, as a material constituting the nonmagnetic portions 24 and 29 in each of the upper mold 21 and the lower mold 26, a nonmagnetic metal such as copper, a heat-resistant resin such as polyimide, a radiation-curable resin, or the like can be used. .

Then, the anisotropic conductive sheet 10 is manufactured using the above-described mold 20 as follows. First, in a liquid polymer material forming material which becomes an insulating elastomer by curing treatment, a fluid sheet forming material in which conductive particles exhibiting magnetism and a non-magnetic conductivity imparting substance are dispersed is prepared. As shown in FIG. 4, the sheet molding material is injected into a mold 20 to form a sheet molding material layer 10A. In the sheet forming material layer 10A, the conductive particles P and the conductivity-imparting substance are in a state of being dispersed in the sheet forming material layer 10A. Next, an electromagnet or a permanent magnet is arranged on the upper surface of the ferromagnetic substrate 22 in the upper die 21 and the lower surface of the ferromagnetic substrate 27 in the lower die 26, and a parallel magnetic field having an intensity distribution, that is, the ferromagnetic material of the upper die 21 A parallel magnetic field having a large strength acts between the layer 23 and the corresponding ferromagnetic layer 28 of the lower mold 26 in the thickness direction of the sheet forming material layer 10A. As a result, in the sheet forming material layer 10A, as shown in FIG. 5, the conductive particles P dispersed in the sheet forming material layer 10A correspond to the ferromagnetic layer 23 of the upper die 21. The lower mold 26 assembles in a portion located between the lower mold 26 and the ferromagnetic layer 28 and is oriented so as to be arranged in the thickness direction. On the other hand, the conductivity-imparting substance is non-magnetic, and thus remains dispersed in the sheet forming material layer 10A even when a parallel magnetic field acts. Then, in this state, the sheet forming material layer 10A is subjected to a curing treatment, whereby
A plurality of conductive path forming portions which are disposed between the first ferromagnetic layer 23 and the corresponding ferromagnetic layer 28 of the lower mold 26 and in which conductive particles P are densely contained in a conductive elastomer. 11
As a result, an anisotropic conductive sheet 10 composed of the stationary conductive portion 12 having no or almost no conductive particles P is obtained.

In the above description, the intensity of the parallel magnetic field applied to the sheet molding material 10 A depends on the ferromagnetic layer 23 of the upper mold 21.
It is preferable that the average size between the ferromagnetic layer 28 of the lower die 26 and the corresponding ferromagnetic layer 28 is 0.02 to 1.5 T on average. When a parallel magnetic field is applied in the thickness direction of the sheet forming material layer 10A by a permanent magnet, the permanent magnet can be provided with an alnico (Fe-Al-Ni-Co-based) in that a parallel magnetic field strength within the above range is obtained. Alloy), ferrite or the like. The curing treatment of the sheet forming material layer 10A can be performed in a state where the parallel magnetic field is applied, but can also be performed after the operation of the parallel magnetic field is stopped. Sheet molding material layer 1
The curing treatment of 0A is appropriately selected depending on the material used, but is usually performed by a heat treatment. The specific heating temperature and heating time are appropriately set in consideration of the type of the material for the polymer substance constituting the sheet molding material layer 10A, the time required for the movement of the conductive particles P, and the like.

According to the anisotropic conductive sheet 10 having the above structure, the upper and lower surfaces of the stationary conductive portion 12 are formed on the conductive path forming portion 1.
1 is formed so as to protrude from each of the upper surface and the lower surface, so that the connected body is simply in contact with the stationary conductive portion 12, that is, in a non-pressurized state or the connected body causes the stationary conductive portion 12 to have a small force. In a state where the conductive body is pressed in the thickness direction, the connected body does not contact the conductive path forming portion 11, and as a result, the electrical characteristics of the conductive elastomer constituting the stationary conductive portion 12 by the stationary conductive portion 12 and the non-conductive property of the conductive elastomer. The conductivity according to the contact area between the connection body and the stationary conductive portion 12 is shown. Moreover, in a state where the stationary conductive portion 12 is pressed in the thickness direction by a large force by the connected body, the stationary conductive portion 12 is greatly compressed, and the connected body comes into contact with the conductive path forming portion 11, and The conductive path forming portion 11 is pressurized. As a result, a conductive path extending in the thickness direction is formed in the conductive path forming portion 11 by a chain of the conductive particles P. Both of the conductive paths formed in the portion 11 exhibit higher conductivity than a state where no pressure is applied or a state where pressure is applied in the thickness direction with a small force.

Such an anisotropic conductive sheet of the present invention comprises:
By bringing the connected object into contact with one side or applying pressure with a small force, static electricity on the surface of the connected object,
Capacitance, the microscopic surface distribution state of the amount of electricity such as the amount of ions can be transferred and held on the surface of the anisotropic conductive sheet. By applying pressure with a large force, the microscopic surface distribution state of the transferred and held amount of electricity can be moved to the other surface of the anisotropic conductive sheet. Specifically, the anisotropic conductive sheet of the present invention is used, for example, for moving the capacitance distribution on the surface of an inspection object to a measurement unit in a capacitance type electrical inspection device such as a printed wiring board. It is useful as a sensor unit, and according to such an electrical inspection device, the capacitance distribution on the surface of the inspection object can be expressed as a two-dimensional image. Further, for example, converting an ion pattern image generated from a writing device such as a laser printer or an electrostatic pattern image of a roll portion of an electronic copying device into an electric pattern image via the anisotropic conductive sheet of the present invention. Can be. Further, according to the anisotropic conductive sheet of the present invention, the present invention is not limited to the above example, and may include static electricity, capacitance,
A microscopic surface distribution state of an electric quantity such as an ion quantity can be expressed as a two-dimensional electric pattern image.
In addition, the anisotropic conductive sheet of the present invention can be used in various applications in which the conventional anisotropic conductive sheet is used, for example, as a connector for achieving electrical connection between circuit devices, or as a circuit device. It can be used as a connector used for electrical inspection.

Further, in the anisotropic conductive sheet of the present invention, by using an appropriate conductive particle P, a chain of the conductive particles P functions as a heat conduction path.
It can be used as a heat conductive sheet such as a heat radiating sheet. For example, by bringing the anisotropic conductive sheet of the present invention into contact with a heating element such as a heating component of an electronic device, and pressing the anisotropic conductive sheet intermittently and repeatedly in the thickness direction, a certain amount of heat is generated from the heating element. Dissipates heat intermittently through the anisotropic conductive sheet, and as a result, the temperature of the heating element can be kept constant. In addition, the anisotropic conductive sheet of the present invention can be used as an electromagnetic radiation absorbing sheet, thereby reducing, for example, electromagnetic noise generated from electronic components and the like.

The anisotropic conductive sheet of the present invention is not limited to the above embodiment, and various changes can be made. For example, as shown in FIG. 6 and FIG.
2 may be formed so as to protrude from only one surface (the upper surface in the figure) of the conductive path forming portion 11. In the anisotropic conductive sheet 10 having such a configuration, the protruding height h of the stationary conductive portion 12 from one surface of the conductive path forming portion 11 is 5 to 50% of the thickness d of the stationary conductive portion 12. Is more preferable, more preferably 10 to 40%, particularly preferably 2 to 40%.
0 to 30%.

[0038]

EXAMPLES The present invention will now be described by way of specific examples, which should not be construed as limiting the invention thereto.

<Example 1> Addition type liquid silicone rubber 1
A sheet molding material was prepared by adding and mixing 100 parts by weight of the conductive particles and 30 parts by weight of the nonmagnetic conductivity-imparting substance in 00 parts by weight. In the above, as the conductive particles, Mn _0.7 Zn _0.2 Fe _0.1 Fe ₂ O ₄
Particles (average particle diameter: 5 μm) were used, and zinc oxide powder was used as the nonmagnetic conductivity-imparting substance.

According to the structure shown in FIG. 3, a mold for forming an anisotropic conductive sheet was produced under the following conditions. [Ferromagnetic substrate] Material: iron, thickness: 5 mm [Ferromagnetic layer] Material: nickel, thickness: 0.08 mm, diameter: 0.08 m
m, pitch: 0.1 mm [Non-magnetic layer] Material: copper, thickness: 0.06 mm [spacer] Thickness: 0.2 mm

The prepared sheet molding material was injected into the mold cavity to form a sheet molding material layer. Next, electromagnets are arranged on the upper surface of the upper die and the lower surface of the lower die, and the thickness of the sheet forming material layer between the upper ferromagnetic material layer and the lower ferromagnetic material layer in the thickness direction is reduced. By applying a hardening treatment to the sheet molding material layer at 120 ° C. for 2 hours while applying a parallel magnetic field of 7T, FIG.
Was manufactured. In this anisotropic conductive sheet, the diameter of the conductive path forming portion is 0.08 mm, the pitch is 0.1 mm, the ratio of the surface area of the conductive path forming portion to the surface is 50%, and the thickness of the stationary conductive portion is 0.1 mm. 2mm, each projecting height is 0.02mm (total 0.04m
m), the volume resistivity of the stationary conductive part is 1 × 10 ¹¹ Ω · m,
The ratio of the conductive particles in the conductive path forming portion is 40% by volume fraction.
Met.

Example 2 Addition type liquid silicone rubber 1
A sheet molding material was prepared by adding and mixing 120 parts by weight of conductive particles and 5 parts by weight of a nonmagnetic conductivity-imparting substance in 00 parts by weight. In the above, nickel particles (number average particle diameter 10 μm) are used as the conductive particles.
The surface of which is partially covered with a silane coupling agent to reduce its conductivity, and used as a nonmagnetic conductivity-imparting substance is a sodium alkane sulfonate having an alkyl group having 5 to 15 carbon atoms (moisture absorbing conductive material). Substance). An anisotropic conductive sheet having the configuration shown in FIG. 1 was produced in the same manner as in Example 1 except that this sheet molding material was used. In this anisotropic conductive sheet, the diameter of the conductive path forming portion is 0.08 mm, the pitch is 0.1 mm, the ratio of the surface area of the conductive path forming portion to the surface is 50%, and the thickness of the stationary conductive portion is 0.1 mm. 2mm, each projecting height is 0.02mm
(Total 0.04 mm), the volume resistivity of the stationary conductive part is 1
× 10 ⁸ Ω · m, the ratio of the conductive particles in the conductive path forming portion is:
The volume fraction was 35%.

Example 3 Addition type liquid silicone rubber 1
In 100 parts by weight, 120 parts by weight of conductive particles, 10 parts by weight of carbon black (self-conductive substance) manufactured by Denki Kagaku as a nonmagnetic conductivity-imparting substance, and sodium having 5 to 15 carbon atoms in an alkyl group. A sheet forming material was prepared by adding and mixing 10 parts by weight of alkane sulfonate (a moisture-absorbing conductive substance). In the above, nickel particles (number average particle diameter 10 μm) are used as the conductive particles.
The surface of which was partially coated with a silane coupling agent to reduce its conductivity was used. 1 in the same manner as in Example 1 except that this sheet molding material was used.
Was manufactured. In this anisotropic conductive sheet, the diameter of the conductive path forming portion is 0.08 mm, the pitch is 0.1 mm, the ratio of the surface area of the conductive path forming portion to the surface is 50%, and the thickness of the stationary conductive portion is 0.1 mm. 2mm, each projecting height is 0.02mm (total 0.04m
m), the volume resistivity of the stationary conductive part is 1 × 10 ⁸ Ω · m,
The ratio of the conductive particles in the conductive path forming portion is 33% by volume.
Met.

Comparative Example 1 Example 1 was repeated except that a sheet-forming material was prepared without using a nonmagnetic conductivity-imparting substance.
An anisotropic conductive sheet for comparison was produced in the same manner as in.

<Evaluation of Electrical Properties of Anisotropic Conductive Sheet> The electrical properties of the anisotropic conductive sheets according to Examples 1 to 3 and Comparative Example 1 were evaluated as follows. [Volume resistivity in the thickness direction in the state of no pressurization] An ion sputtering device (E10
10, manufactured by Hitachi Science Co., Ltd.) to form a metal film having a thickness of 100 nm using Au-Pd as a target. A wiring connected to an insulation resistance meter (4339A high resistance meter, manufactured by HP) was bonded to the surface of the metal film with a conductive adhesive containing silver. And
By pressing the other surface of the anisotropic conductive sheet with the measuring electrode having an electrode diameter of 50 mm connected to the insulation resistance meter, the surface of the measuring electrode is sufficiently adhered to the other surface of the anisotropic conductive sheet. Then, the surface of the measurement electrode was brought into contact with the other surface of the anisotropic conductive sheet, that is, in a non-pressurized state. Then, in this state, a current having an appropriate voltage value or current value is supplied between the measurement electrode and the metal film, and 1
After a lapse of minutes, the volume resistivity in the thickness direction of the anisotropic conductive sheet (including the space formed on both end surfaces of the conductive path forming portion)
Was measured. [Volume resistivity in a state of being pressed in the thickness direction] An anisotropic conductive sheet was connected to an insulation resistance meter (4339A high resistance meter, manufactured by HP), and a measuring electrode having an electrode diameter of 50 mm and a pressing electrode were used. Placed between the electrodes,
30% distortion rate of anisotropic conductive sheet by pressing electrode
, And in this state, the volume resistivity in the thickness direction of the anisotropic conductive sheet was measured. The results are shown in Table 1.

[0046]

[Table 1]

[Charge Transfer and Mobility] As shown in FIG. 8, an anisotropic conductive sheet 1 is disposed on a ground plate 40, and a urethane resin roll is placed immediately above the anisotropic conductive sheet 1. 45 were arranged. The roll 45 is formed by accumulating electric charges on the surface thereof by a discharge treatment by a Tesla coil, and has a surface potential of 500 ± 50.
V (Trek Japan surface electrometer "Model 520-
1 "). Then, the roll 45 is gradually lowered to come into contact with the surface of the anisotropic conductive sheet 1 (in a non-pressurized state). The surface potential of the conductive sheet 1 was measured by a surface potentiometer “Model 520-1”. Then roll 4
5, the surface of the anisotropic conductive sheet 1 is pressurized so that its distortion rate becomes 30%, and is maintained for 1 minute in this state. The surface potential of the conductive sheet 1 was measured by a surface potentiometer “Model 520-1”. The above operation was performed ten times in total, and the average value of the surface potential and the variation in the value were obtained. The results are shown in Table 2 above.

[0048]

[Table 2]

As is clear from the results in Table 2, Examples 1 to
According to the anisotropically conductive sheet according to No. 3, by bringing the surface of the roll 45 into contact with the surface of the anisotropically conductive sheet, the charge on the surface of the roll 45 can be reproduced with high reproducibility on the surface of the anisotropically conductive sheet. Transfer was confirmed. Further, it was confirmed that when the surface of the anisotropic conductive sheet was pressed by the roll 45, the charge on the surface of the roll 45 moved to the ground plate via the anisotropic conductive sheet. On the other hand, in the anisotropic conductive sheet according to Comparative Example 1,
The charge on the surface of the roll 45 could not be stably transferred to the surface.

[0050]

As described above, according to the present invention,
In a state where no pressure is applied or a state where pressure is applied in the thickness direction with a small force, conductivity is exhibited, and in a state where pressure is applied in the thickness direction with a large force, a state where no pressure is applied or a state where pressure is applied in the thickness direction with a small force An anisotropic conductive sheet showing higher conductivity can be provided.

[Brief description of the drawings]

FIG. 1 is an explanatory sectional view showing a configuration of an example of an anisotropic conductive sheet of the present invention.

FIG. 2 is an explanatory sectional view showing a part of the anisotropic conductive sheet shown in FIG. 1 in an enlarged manner.

FIG. 3 is an explanatory cross-sectional view illustrating a configuration of an example of a mold for manufacturing the anisotropic conductive sheet of the present invention.

FIG. 4 is an explanatory sectional view showing a state in which a sheet molding material layer is formed in the mold shown in FIG. 3;

FIG. 5 is an explanatory sectional view showing a state in which a parallel magnetic field having an intensity distribution is applied to a sheet forming material layer in a thickness direction.

FIG. 6 is an explanatory cross-sectional view showing a configuration of another example of the anisotropic conductive sheet of the present invention.

FIG. 7 is an explanatory sectional view showing a part of the anisotropic conductive sheet shown in FIG. 6 in an enlarged manner.

FIG. 8 is an explanatory view showing an apparatus used for evaluating electric characteristics of an anisotropic conductive sheet in Examples.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 anisotropic conductive sheet 10 anisotropic conductive sheet 10A sheet forming material layer 11 conductive path forming portion 12 stationary conductive portion 20 mold 21 upper mold 22 ferromagnetic substrate 23 ferromagnetic layer 24 non-magnetic layer 25 spacer 26 Lower mold 27 Ferromagnetic substrate 28 Ferromagnetic layer 29 Nonmagnetic layer 40 Ground plate 45 Roll P Conductive particles

Continuation of the front page (72) Inventor Ryoji Setaka 2-11-24 Tsukiji, Chuo-ku, Tokyo FSR term in JSR Corporation (reference) 2G003 AA07 AG07 AG08 AG12 AH05 AH09 2G011 AA15 AA21 AB00 AB08 AC14 AC32 AC33 AF04 5F044 LL09

Claims (6)

[Claims] 1. An elastomer, wherein conductive particles exhibiting magnetism are contained in an elastomer so as to be aligned in a thickness direction.
A large number of conductive path forming portions extending in the thickness direction are arranged apart from each other in the surface direction via a stationary conductive portion made of a conductive elastomer, and the stationary conductive portion has at least one surface thereof as the conductive path forming portion. An anisotropic conductive sheet formed so as to protrude from the surface of the sheet. 2. The anisotropic material according to claim 1, wherein the conductive elastomer constituting the stationary conductive portion is formed by dispersing a non-magnetic conductivity-imparting substance in an insulating elastomer. Conductive sheet. 3. The substance according to claim 2, wherein the conductivity-imparting substance is at least one substance selected from a substance exhibiting conductivity by itself and a substance exhibiting conductivity by absorbing moisture. Anisotropic conductive sheet. 4. The conductive elastomer constituting the stationary conductive portion has a volume resistivity of 1 × 10 ⁷ to 1 × 10 ¹² Ω · m. The anisotropic conductive sheet according to the above. 5. The anisotropic conductive sheet according to claim 1, wherein both surfaces of the stationary conductive portion are formed so as to protrude from the surface of the conductive path forming portion. . 6. The stationary conductive part according to claim 1, wherein the protruding height of the conductive part from the surface of the conductive part or the total height thereof is 5 to 50% of the thickness of the stationary conductive part. The anisotropic conductive sheet according to any one of the above.