JP2005285536A - Anisotropic conductive film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an anisotropic conductive film that easily responds to further pitch reduction while securing the conductivity in the thickness direction and the insulation property in the film surface direction. <P>SOLUTION: The anisotropic conductive film comprises a porous film that has many holes penetrating in the thickness direction and is composed of polymer, and a conductive layer covered by the hole inner wall surface of this porous film. The holes are arranged in a honeycomb shape, and the inner wall surfaces of the holes are bent in the outside direction. The conductive layer is preferably a metal layer formed by metal plating. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an anisotropic conductive film, and more particularly to an anisotropic conductive film suitably used for functional inspection of electronic parts such as semiconductor elements and pressure sensitive sensors.

  Conventionally, anisotropic conductive films (ACF) that are conductive in the film thickness direction and insulative in the film surface direction are known, and function inspection and sensitivity of electronic components such as semiconductor elements are known. Used for pressure sensors.

  For example, Non-Patent Document 1 describes an ACF 104 in which a copper pillar 102 is arranged in the thickness direction of an insulating resin sheet 100 as shown in FIG. The ACF 104 is sandwiched between the electronic component 106 and the test substrate 108 and then pressed in the thickness direction, thereby being subjected to various inspections such as a continuity test.

 For example, Non-Patent Document 2 describes an ACF 114 in which metal particles 112 are arranged in the thickness direction of the rubber sheet 110 as shown in FIG. As shown in FIG. 6 (b), the ACF 114 is anisotropically conductive by being pressed in the thickness direction and brought into contact with the metal particles 112, and is used in a pressure-sensitive sensor.

  By the way, Non-Patent Document 3 and Non-Patent Document 4 describe a porous film made of a polymer having a honeycomb structure in which pores are regularly arranged in the film thickness direction, although it is not ACF.

Miho Yamaguchi, Fumiaki Asai, “Anisotropic Conductive Film for Inspection Cupil-T”, Nitto Giho, May 2002, Vol. 40, No. 1, p. 17-p. 20 “Code Switch (Pressure Conductive Rubber Pressure Sensitive Sensor)”, [online], Bridgestone Corporation, [Search January 8, 2004], Internet <http://www.bridgestone-dp.jp/dp/ ip / switch / code_sw / code_sw02.html> Masahiro Shimomura, “Formation and functionalization of nano-mesohol structures by self-organization of polymer materials”, Functional Materials, CMC Publishing Co., Ltd., October 2003, vol. 23, no. 10, p. 18-p. 26 Masahiro Shimomura, “Pattern formation by self-organization and development to microfabrication technology”, Materia, The Japan Institute of Metals, 2003, Vol. 42, No. 6, p. 457-p. 460

  However, the inspection ACF has the following problems.

  That is, in general, all electronic components such as semiconductor chips are subjected to a continuity test before mounting in order to prevent defective products from being mounted on the substrate.

  Previously, an inspection method called a contact pin method, in which one pin is brought into contact with each terminal, was used. However, in this method, an individual jig with a pin is required for each component, and an electronic component is used. It was not possible to cope with the narrow pitch accompanying the downsizing.

  Therefore, the inspection ACF has been developed and used as an inspection method that can cope with a narrow pitch and does not require an individual jig for each part.

  However, in recent years, there has been a remarkable trend toward miniaturization of cellular phones and the like, and along with the further miniaturization of electronic components, an ACF for inspection that can handle a narrow pitch of 100 μm pitch or less is currently being demanded. .

  However, if the ACF for inspection of Non-Patent Document 1 is used to reduce the diameter of the copper pillar to cope with further narrow pitch, resistance in the thickness direction becomes large or it becomes difficult to align the copper pillar. At the current level, a pitch of about 100 μm was the limit. For this reason, there is a problem that it is difficult to cope with a narrower pitch than this.

On the other hand, the pressure-sensitive sensor ACF also had the same problem as the inspection ACF.
That is, in order to detect a change in pressure applied to a minute region as a change in electrical resistance using the pressure-sensitive sensor ACF, the particle diameter of the metal particles is reduced and the pitch of the metal particles is further reduced. It is necessary to make it.

  However, when trying to cope with narrow pitch by reducing the diameter of metal particles, there is a limit to further narrow pitch, such as increasing resistance in the thickness direction and making it difficult to align metal particles.

  The present invention has been made in view of the above problems, and the problem to be solved by the present invention is to cope with further narrow pitch while ensuring the conductivity in the film thickness direction and the insulation in the film surface direction. An object is to provide an easy anisotropic conductive film.

  In order to solve the above-described problem, the anisotropic conductive film according to claim 1 has a large number of holes penetrating in the film thickness direction, and the holes are arranged in a honeycomb shape, and the inside of the holes is The gist is that the wall surface is provided with a porous film made of a polymer, which is curved outward, and a conductive layer coated on the inner wall surface of the hole of the porous film.

  The anisotropic conductive film according to claim 2 casts a polymer solution containing a hydrophobic and volatile organic solvent, a polymer soluble in the organic solvent, and an amphiphilic substance. A porous membrane having a large number of pores arranged in a honeycomb shape, which can be obtained by allowing the support substrate to exist in an atmosphere having a relative humidity of 50% or more, and a conductive film coated on the inner wall surface of the pores of the porous membrane. The gist is that it comprises a layer.

  The anisotropic conductive film according to claim 3 is the one according to claim 1 or 2, wherein the conductive layer is a metal layer formed by metal plating.

  An anisotropic conductive film according to a fourth aspect is the one according to the first to third aspects, wherein the polymer is a thermoplastic elastomer and / or rubber.

  The anisotropic conductive film according to claim 5 is the anisotropic conductive film according to claim 4, wherein the thermoplastic elastomer is one or more selected from silicone elastomers and fluorine elastomers. It is a summary.

  In the anisotropic conductive film according to the first aspect, a large number of minute holes arranged in a honeycomb shape are separated from each other, and the inner wall surface of these holes is covered with a conductive layer. Therefore, for example, even when the conductor pitch of the electronic component to be subjected to the function inspection is further narrowed compared to the conventional case, it can be easily handled. For example, even when a pressure is applied to a minute region, the pressure change can be detected as a change in electrical resistance. In addition, the conduction in the film thickness direction and the insulation in the surface direction are sufficiently secured. Further, since the inner wall surface of the hole is curved outward and the inner wall surface is covered with the conductive layer, the resilience (cushioning property) in the film thickness direction is also excellent.

  Further, the porous film having a large number of minute pores arranged in a honeycomb shape includes an organic solvent having hydrophobicity and volatility, a polymer soluble in the organic solvent, and an amphiphilic substance. It can be easily formed by using a method in which a support substrate cast with a polymer solution is present in an atmosphere with a relative humidity of 50% or more. Therefore, the anisotropic conductive film can be manufactured easily and inexpensively.

  The anisotropic conductive film according to claim 2 casts a polymer solution containing a hydrophobic and volatile organic solvent, a polymer soluble in the organic solvent, and an amphiphilic substance. A porous film having a large number of pores arranged in a honeycomb shape, which can be obtained by allowing the support substrate to exist in an atmosphere having a relative humidity of 50% or more, is used. Therefore, the anisotropic conductive film can be manufactured easily and inexpensively.

  In the anisotropic conductive film according to claim 3, since the conductive layer is a metal layer formed by metal plating, it is easy to ensure conduction in the film thickness direction.

  In the anisotropic conductive film according to claim 4, since the polymer is made of a thermoplastic elastomer and / or rubber, the inner wall surface of the hole is curved in the outer direction, and the film thickness direction Excellent rebound resilience (cushioning property).

  Moreover, since the anisotropic conductive film of Claim 5 consists of 1 type (s) or 2 or more types as which a thermoplastic elastomer is selected from a silicone type elastomer and a fluorine-type elastomer, not only rebound resilience (cushion property), Excellent heat resistance.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a cross-sectional view schematically showing the structure of an anisotropic conductive film according to the present invention. FIG. 2 is a diagram schematically showing the configuration of the porous film in the anisotropic conductive film according to the present invention.

  First, the structure of the anisotropic conductive film (hereinafter referred to as “the present ACF”) according to the present invention will be described with reference to FIGS.

  The ACF 10 includes a porous film 12 and a conductive layer 14 as a basic configuration.

  In the present ACF 10, the porous film 12 is formed of a polymer and has a large number of holes 16 penetrating in the film thickness direction. That is, as shown in FIG. 2B, the hole portions 16 are arranged in a honeycomb shape, and the adjacent hole portions 16 are separated from each other by the partition walls 18. Further, as shown in FIG. 2A, the inner wall surfaces 20 of these holes 18 are curved in a substantially spherical shape toward the outer side.

  Here, the diameter and interval of the holes in the porous film are in contact with the width / interval of a plurality of conductors (for example, protruding electrodes of an IC chip) included in an inspection object such as an electronic component, and the surface of the ACF 10. It may be determined in consideration of the outer dimensions of the pressed portion.

  When used as an ACF for inspection, the diameter of the hole is smaller than the narrowest of the intervals between the plurality of conductors of the inspection object from the viewpoint of ensuring insulation in the surface direction. It is desirable that the distance between the holes is small and smaller than the narrowest width among the plurality of conductors included in the inspection object.

  Preferably, the diameter of the hole is ½ or less of the narrowest spacing among the plurality of conductors included in the inspection object, and the interval between the holes is the width of the plurality of conductors included in the inspection object. Of these, it is preferable to make it 1/2 or less of the narrowest.

  In addition, in the above, the diameter of a hole means the value which measured and averaged the diameter R of the opening part of the hole which appears on the film | membrane surface or back surface, as shown in FIG.2 (b), and is the space | interval of a hole. The term “means” refers to a value obtained by measuring and averaging the distance L between the opening portion of the hole portion appearing on the film surface or the back surface and the opening portion of the adjacent hole portion. The diameter R and the distance L are measured from an SEM photograph of the porous membrane surface.

  Further, the thickness of the porous film may be determined in consideration of the mechanical strength, voltage resistance, etc. of the present ACF. Preferably, it is in the range of 1 to 100 μm, more preferably 5 to 50 μm.

  Specific examples of the polymer forming the porous film include polystyrene-polybutadiene elastomer, polystyrene-polyisoprene elastomer, polystyrene-poly (ethylene / butylene) elastomer, polystyrene-poly (ethylene / propylene) elastomer, and the like. Polystyrene thermoplastic elastomer, Polybutadiene, polybutylene terephthalate, etc. as hard segment, polyester, polyether thermoplastic elastomer, silicone elastomer, fluorine elastomer, polyamide elastomer, crystal using polyester, polyether, etc. as soft segment Polyolefin elastomer with hard polyolefin as the hard segment and olefin elastomer as the soft segment, etc. Examples of thermoplastic elastomers include polyurethane, acrylic rubber, silicone rubber, chlorosulfonated polyethylene, epichlorohydrin rubber, hydrogenated nitrile rubber, fluororubber, ethylene / propylene / diene terpolymers, etc. May be used alone or in combination.

  Of these, silicone elastomers and fluorine elastomers are preferred from the standpoint of excellent heat resistance and impact resilience (cushioning properties). An example in which heat resistance is required is when the present ACF is used for a burn-in test or the like for inspecting chip conduction in a heated state.

  In the present ACF, the conductive layer 14 is basically covered with the inner wall surface 20 of the hole 16 of the porous membrane 12 as shown in FIG. At this time, it is preferable that the conductive layer 14 has a protruding portion 22 that slightly protrudes from the opening periphery of the hole portion 16 on the surface of the porous film from the viewpoint of improving the reliability of the electrical connection in the film thickness direction. .

  In this case, the height of the protruding portion may be determined in consideration of variations in the height of the conductor of the inspection object, warpage of the inspection object, and the like. Preferably, it is in the range of 1 to 100 μm, more preferably 1 to 10 μm.

  In addition, the thickness of the conductive layer may be determined in consideration of the diameter of the pores of the porous membrane. Preferably, it is in the range of 0.1 to 50 μm, more preferably 0.1 to 10 μm.

  Specifically, the conductive layer is preferably a metal layer formed by plating a metal such as Ag, Au, Pt, Ni, Cu, or Pd. Preferably, it is made of an Ag plating layer.

  Next, a method for manufacturing the present ACF having the above configuration will be described. The manufacturing method of the present ACF basically includes a step of forming a porous film and a step of covering the inner wall surface of the hole of the porous film with a conductive layer.

(Formation of porous film)
In the method for producing the ACF, it is preferable to use the following method for the porous film forming step. First, the outline and principle of the method will be described with reference to FIG. In brief, the technique is a technique in which a polymer is dissolved in a volatile organic solvent that is not mixed with water, and a support substrate cast with this polymer solution is present under high humidity conditions.

  According to this technique, a porous film having a large number of pores arranged in a honeycomb shape is spontaneously formed according to the following principle. As shown in FIG. 3, 1) water molecules in the air are condensed by the latent heat generated when the organic solvent evaporates to form minute water droplets 24, which are packed finely on the surface of the solution 26. 2) Further, the water droplet 24 is transported to the interface between the solution 26 and the support substrate 28 by convection or capillary force generated in the solution 26 by latent heat. 3) The water droplet 24 is fixed on the support substrate 28 by the receding solvent. 4) Further, when the water droplets 24 evaporate, the porous film 12 having a large number of pores 16 arranged in a honeycomb shape using the regularly arranged water droplets 24 as a template is formed. In addition, since the water droplet 24 becomes a casting_mold | template, the inner wall surface 20 of the hole 16 will be in the state curved outward.

  This will be described in more detail below. That is, as the polymer solution, a solution containing a hydrophobic and volatile organic solvent, a polymer soluble in the organic solvent, and an amphiphilic substance is preferably used.

  Examples of the hydrophobic and volatile organic solvent include halides such as chloroform and methylene chloride, aromatic hydrocarbons such as benzene, toluene and xylene, esters such as ethyl oxide and butyl acetate, and the like. You may use a seed | species or 2 or more types in mixture.

  Specific examples of the polymer soluble in the organic solvent include polystyrene-polybutadiene elastomers, polystyrene-polyisoprene elastomers, polystyrene-poly (ethylene / butylene) elastomers, polystyrene-poly (ethylene / propylene) elastomers, and the like. Thermoplastic elastomer, Polybutadiene, polybutylene terephthalate, etc. as hard segment, polyester, polyether thermoplastic elastomer, silicone elastomer, fluorine elastomer, polyamide elastomer, crystalline polyolefin using polyester, polyether, etc. as soft segment Thermoplastics such as polyolefin elastomers with hard segments and olefin elastomers as soft segments Examples of elastomers include polyurethane, acrylic rubber, silicone rubber, chlorosulfonated polyethylene, epichlorohydrin rubber, hydrogenated nitrile rubber, fluorine rubber, ethylene / propylene / diene terpolymer, and the like. You may use a seed or 2 or more types mixed.

  Here, the amphiphilic substance is a so-called surfactant, which is a compound having both a hydrophobic part and a hydrophilic part. This amphiphilic substance is added mainly for the purpose of stabilizing the water droplet group generated on the surface of the polymer solution. The reason why the water droplet group is stabilized is presumed that the hydrophobic portion of the amphiphilic substance is compatible with the hydrophobic organic solvent, and water is easily retained in the space portion of the reverse micelle generated thereby.

  As such an amphiphilic substance, specifically, a polymer having a hydrophilic acrylamide polymer as a main chain skeleton, a dodecyl group as a hydrophobic side chain, and a lactose group or a carboxyl group as a hydrophilic side chain, or And polyionic complexes of anionic polysaccharides such as heparin and dextran sulfate with quaternary long-chain alkylammonium salts. These may be used alone or in combination of two or more.

  At this time, the concentration of the polymer contained in the polymer solution is 0.1 to 20% by weight, preferably 0.5 to 5% by weight.

  This is because if the polymer concentration is within this range, a porous membrane having sufficient mechanical strength can be obtained, and a sufficient honeycomb structure can be obtained.

  The concentration of the amphiphilic substance contained in the polymer solution is preferably 0.01 to 20% by weight, and preferably 0.05 to 5% by weight.

  This is because if the concentration of the amphiphile is within this range, the honeycomb structure can be obtained stably.

  In the step of forming the porous film in the method for producing the ACF, a polymer solution containing a hydrophobic and volatile organic solvent and an amphiphilic polymer is used instead of the polymer solution described above. May be.

  Here, the amphiphilic polymer refers to a polymer in which a hydrophobic site and a hydrophilic site are introduced. A specific case where the polymer is used as amphiphilic is a case where the polymer forming the porous film is hardly soluble or insoluble in an organic solvent.

Specifically, as the amphiphilic polymer, a polyionic complex of a polyamic acid and a cationic lipid, or a hydrophilic group such as —SO ₃ H group or —COOH group is introduced into the main chain or side chain. Examples include polyetheretherketone, polyimide, polyamideimide, polyetherimide, and the like, and these may be used alone or in combination.

  In the above, polyamic acid means 3,3 ′, 4,4′-biphenyltetracarboxylic acid, 3,3 ′, 4,4′-biphenyl ether tetracarboxylic acid, 3,3 ′, 4,4 ′. -Biphenylsulfone tetracarboxylic acid, 3,3 ', 4,4'-benzophenone tetracarboxylic acid, pyromesato acid, trimellitic acid and other tetracarboxylic dianhydrides, p-phenylenediamine, m-phenylenediamine, 2,5 -A resin composition obtained by polymerizing a diamine compound such as diaminotoluene, 2,6-diaminotoluene, 4,4'-diaminobiphenyl, diaminodiphenylmethane in a polar solvent.

  Examples of cationic lipids include aliphatic ammonium salt compounds having 4 or more carbon atoms such as octylamine, decylamine, tetradecylamine, hexadecylamine, stearylamine, cyclohexylamine, N-methyl-n-cyclohexylamine, N, And alicyclic ammonium salt compounds such as N′-dimethyl-n-cyclohexylamine.

  The polyionic complex of polyamic acid and cationic lipid is a lipid dissolved in the above lipid or an organic solvent that can be used for polymerization of the above amic acid in a solution containing a polyamic acid neutralized with a base. It can be obtained by blending a solution of

  When a polyionic complex of polyamic acid and cationic lipid is used, it is preferable to imidize the formed film by a known method. This is because the polyamic acid is closed to form a porous film made of polyimide.

  At this time, the concentration of the amphiphilic polymer contained in the polymer solution is 0.01 to 20% by weight, preferably 0.05 to 5% by weight.

  This is because if the concentration of the amphiphilic polymer is within this range, a porous film having sufficient mechanical strength can be obtained, and a sufficient honeycomb structure can be obtained.

  In addition, since the organic solvent which has hydrophobicity and volatility is the same as that of what was mentioned above, description is abbreviate | omitted.

  Examples of the material of the support substrate for casting the polymer solution described above include inorganic materials such as glass, metal, and silicon wafer, polymer materials such as polypropylene, polyethylene, and polyetherketone, water, and liquid paraffin.

  The cast amount of the polymer solution is, for example, the pore diameter of the porous membrane is smaller than the narrowest among the intervals between the plurality of conductors of the test object, and the interval between the pores is The width can be appropriately adjusted such that it is smaller than the narrowest width among the plurality of conductors of the connected object.

  Specifically, the cast amount of the polymer solution has a coating thickness of 50 to 3500 μm, preferably 150 to 1500 μm.

  Further, it is desirable that the support substrate on which the polymer solution is cast be present in an atmosphere with a relative humidity of 50% to 95%. This is because if the relative humidity is less than 50%, condensation tends to be insufficient, and if it exceeds 95%, it tends to be difficult to control the environment.

  In the porous film forming step, the polymer solution may be cast on a support substrate in an atmosphere with a relative humidity of 50% to 95%, or the support substrate on which the polymer solution is cast in advance is used as a relative humidity. It may be placed in an atmosphere of 50% to 95%. Further, the air having a relative humidity of 50% to 95% may be sprayed on the polymer solution.

  Further, in the porous film forming step, the organic solvent and the water droplet groups arranged on the surface of the polymer solution are accelerated, so that heating or the like may be performed without affecting the porous film. good.

(Coating of conductive layer)
Next, in the manufacturing method of the ACF, as a method of covering the inner wall surface of the porous film with the conductive layer, for example, when the conductive layer is a metal layer, the metal film is attached to one surface of the porous film. Examples of the method include a method of selectively plating a metal layer on the inner wall surface of the hole and the peripheral edge of the hole by removing the metal film by etching after performing electrolytic plating using this as an electrode.

  In addition, for example, by dispersing the above-described metal fine particles in a solvent in which the polymer is insoluble, and immersing the porous film in this dispersion solution, the metal fine particles are formed on the inner wall surface of the hole and the opening periphery of the hole. The method of making it precipitate is mentioned. At this time, the content of the metal fine particles in the polymer solution is preferably 1 to 50% by weight, and more preferably 1 to 10% by weight. The average diameter of the metal fine particles is preferably about 1 μm or less.

  Next, an inspection method using this ACF will be described with reference to FIG. As shown in FIG. 4, the ACF 10 is sandwiched between, for example, a test substrate 30 and a semiconductor chip 32 that is an inspection object, and pressed in the thickness direction of the ACF 10, whereby the wiring pattern 34 of the test substrate 30 Conductivity is ensured between the protruding electrodes 36 of the semiconductor chip 32, and a continuity test or the like can be performed.

  The present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, the inspection method using the present ACF has been described. However, the present invention can be used not only for inspection purposes but also for pressure-sensitive sensor applications.

It is sectional drawing which showed typically the structure of the anisotropic electrically conductive film which concerns on this invention. It is the figure which showed typically the structure of the porous film in the anisotropic electrically conductive film which concerns on this invention. It is the figure which showed typically the principle in which the porous membrane which has many hole parts arranged in the honeycomb form is formed. It is a figure for demonstrating typically the inspection method of a semiconductor chip etc. using the anisotropic conductive film concerning the present invention. It is a figure for demonstrating typically the inspection method of a semiconductor chip etc. using the conventional anisotropic conductive film. It is a figure for demonstrating the principle of operation of the conventional anisotropic conductive film used for a pressure-sensitive sensor use.

Explanation of symbols

10 ACF (anisotropic conductive film)
12 Porous membrane 14 Conductive layer 20 Inner wall surface 22 Projection

Claims (5)

A porous film made of a polymer having a large number of holes penetrating in the film thickness direction, the holes being arranged in a honeycomb shape, and an inner wall surface of the holes being curved outward;
An anisotropic conductive film comprising: a conductive layer coated on an inner wall surface of a hole of the porous film. A support substrate in which a polymer solution containing a hydrophobic and volatile organic solvent, a polymer soluble in the organic solvent, and an amphiphile is cast is present in an atmosphere with a relative humidity of 50% or more. A porous membrane having a large number of pores arranged in a honeycomb shape, which can be obtained by:
An anisotropic conductive film comprising: a conductive layer coated on an inner wall surface of a hole of the porous film.   The anisotropic conductive film according to claim 1, wherein the conductive layer is a metal layer formed by metal plating.   The anisotropic conductive film according to claim 1, wherein the polymer is a thermoplastic elastomer and / or rubber.   The anisotropic conductive film according to claim 4, wherein the thermoplastic elastomer is one or more selected from silicone elastomers and fluorine elastomers.

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