JP2012142247A - Anisotropic conductive material and connection structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anisotropic conductive material which, when used for connection between electrodes in a connection structure, facilitates the connection between the electrodes, can enhance conduction reliability and furthermore can enhance heat impact resistant characteristics of the connection structure against thermal shock such as cooling-heating cycle.SOLUTION: The anisotropic conductive material relating to the present invention includes conductive particles 1 and a binder resin. The conductive particle 1 includes a resin particle 2 and a conductive layer 3 covering a surface 2a of the resin particle 2. At least an outside surface layer of the conductive layer 3 is a solder layer 5. The absolute value of the difference between a linear expansion coefficient at 30 to 60°C of the resin particle 2 in the conductive particle 1 and a linear expansion coefficient at 30 to 60°C of a material including all components except the conductive particles 1 in the anisotropic conductive material is 15 ppm/°C or less.

Description

  The present invention relates to an anisotropic conductive material including conductive particles having a solder layer, and more specifically, for example, an anisotropic conductive material that can be used for electrical connection between electrodes, and the anisotropic The present invention relates to a connection structure using a conductive material.

  Conductive particles are used for connection between an IC chip and a flexible printed circuit board, connection between liquid crystal driving IC chips, connection between an IC chip and a circuit board having an ITO electrode, and the like. For example, after the conductive particles are arranged between the electrode of the IC chip and the electrode of the circuit board, the electrodes can be electrically connected by bringing the conductive particles into contact with the electrodes by heating and pressurization.

  The conductive particles are dispersed in a binder resin and are also used as an anisotropic conductive material.

  As an example of the conductive particles, Patent Document 1 listed below discloses conductive particles having base particles formed of nickel or glass and a solder layer covering the surface of the base particles. ing. The conductive particles are mixed with a polymer matrix and used as an anisotropic conductive material.

  Patent Document 2 below discloses conductive particles having resin particles, a nickel plating layer covering the surface of the resin particles, and a solder layer covering the surface of the nickel plating layer. Yes.

Japanese Patent No. 2769491 JP-A-9-306231

  In the conductive particles described in Patent Document 1, since the material of the base particles in the conductive particles is glass or nickel, the conductive particles may settle in the anisotropic conductive material. For this reason, the anisotropic conductive material cannot be applied uniformly during the conductive connection, and the conductive particles may not be disposed between the upper and lower electrodes. Further, the agglomerated conductive particles may cause a short circuit between electrodes adjacent in the lateral direction.

  Note that Patent Document 1 merely describes a configuration in which the material of the base material particles in the conductive particles is glass or nickel. Specifically, the base material particles are formed of a ferromagnetic metal such as nickel. It is only described to do.

  The conductive particles described in Patent Document 2 are not used by being dispersed in a binder resin. This is because the conductive particles are not preferable for use as an anisotropic conductive material dispersed in a binder resin because the conductive particles have a large particle size. In the example of Patent Document 2, the surface of resin particles having a particle size of 650 μm is coated with a conductive layer, and conductive particles having a particle size of several hundreds of μm are obtained. It is not used as a mixed anisotropic conductive material.

  In Patent Document 2, when connecting the electrodes of the connection target member using conductive particles, one conductive particle is placed on one electrode, and then the electrode is placed on the conductive particle. Heating. By heating, the solder layer is melted and joined to the electrode. However, the operation of placing conductive particles on the electrode is complicated. Further, since there is no resin layer between the connection target members, the connection reliability is low.

  Further, in a conventional anisotropic conductive material containing conductive particles, when a thermal shock such as a thermal cycle is applied to a connection structure using the anisotropic conductive material for connection between electrodes, conduction between the electrodes is achieved. Reliability may be reduced. That is, a connection structure using a conventional anisotropic conductive material may have low thermal shock characteristics.

  An object of the present invention is that when used for connection between electrodes in a connection structure, the connection between the electrodes is easy, the conduction reliability can be improved, and further, the connection structure against a thermal shock such as a thermal cycle is provided. An object is to provide an anisotropic conductive material capable of enhancing the thermal shock resistance and a connection structure using the anisotropic conductive material.

  According to a wide aspect of the present invention, the conductive particle includes a conductive particle and a binder resin, and the conductive particle has a resin particle and a conductive layer covering a surface of the resin particle. At least the outer surface layer is a solder layer, and the material contains all components except the linear expansion coefficient of the resin particles in the conductive particles at 30 to 60 ° C. and the conductive particles in the anisotropic conductive material. An anisotropic conductive material in which the absolute value of the difference from the linear expansion coefficient at 30 to 60 ° C. is 15 ppm / ° C. or less is provided.

  In a specific aspect of the anisotropic conductive material according to the present invention, the binder resin is a curable compound, and the linear expansion coefficient of the material including all components except the conductive particles in the anisotropic conductive material is: It is a linear expansion coefficient of the hardened | cured material of the material containing all the components except the said electroconductive particle in an anisotropic conductive material.

  In another specific aspect of the anisotropic conductive material according to the present invention, the binder resin is an epoxy compound.

  In another specific aspect of the anisotropic conductive material according to the present invention, the conductive particles have an average particle size of 0.1 μm or more and 50 μm or less.

  In another specific aspect of the anisotropic conductive material according to the present invention, a flux is further included.

  The connection structure according to the present invention includes a first connection target member, a second connection target member, and a connection portion connecting the first and second connection target members, and the connection The portion is formed of an anisotropic conductive material configured according to the present invention.

  Since the anisotropic conductive material according to the present invention includes the specific conductive particles and the binder resin, when the anisotropic conductive material is used for connection between the electrodes in the connection structure, it is easy to connect the electrodes. Can be connected. Further, since the conductive particles have resin particles and a conductive layer covering the surface of the resin particles, and at least the outer surface layer of the conductive layer is a solder layer, the conduction reliability of the connection structure is obtained. Sexuality can be increased.

  Furthermore, in the anisotropic conductive material according to the present invention, the specific conductive particles are used, and the linear expansion coefficient of the resin particles in the conductive particles at 30 to 60 ° C. and the anisotropic conductive material Since the absolute value of the difference from the coefficient of linear expansion at 30 to 60 ° C. of the material including all components excluding the conductive particles is 15 ppm / ° C. or less, the thermal shock resistance characteristics of the connection structure against the thermal shock such as the thermal cycle Can be increased.

FIG. 1 is a cross-sectional view showing conductive particles contained in an anisotropic conductive material according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing a modification of the conductive particles. FIG. 3 is a front sectional view schematically showing a connection structure using an anisotropic conductive material according to an embodiment of the present invention. FIG. 4 is an enlarged front sectional view showing a connection portion between the conductive particles and the electrodes of the connection structure shown in FIG.

  Details of the present invention will be described below.

  The anisotropic conductive material according to the present invention includes conductive particles and a binder resin. The conductive particles include resin particles and a conductive layer covering the surface of the resin particles. At least the outer surface layer of the conductive layer in the conductive particles is a solder layer. The linear expansion coefficient at 30 to 60 ° C. of the resin particles in the conductive particles and the linear expansion coefficient at 30 to 60 ° C. of the material including all components except the conductive particles in the anisotropic conductive material. The absolute value of the difference is 15 ppm / ° C. or less.

  Since the anisotropic conductive material which concerns on this invention is equipped with the said structure, when this anisotropic conductive material is used for the connection between the electrodes in a connection structure, the connection between electrodes is easy. For example, without disposing conductive particles one by one on the electrode provided on the connection target member, the conductive particles can be formed on the electrode by simply coating or laminating an anisotropic conductive material on the connection target member. Can be placed. Furthermore, after an anisotropic conductive material layer is formed on the connection target member, the other electrodes are stacked on the anisotropic conductive material layer so that the electrodes face each other, and the electrodes are electrically connected. it can. Therefore, the manufacturing efficiency of the connection structure in which the electrodes of the connection target members are connected can be increased. Furthermore, since not only the conductive particles but also the binder resin exists between the connection target members, the connection target members can be firmly adhered, and the connection reliability can be improved.

  Furthermore, when the anisotropic conductive material according to the present invention is used for connection between electrodes, the conduction reliability of the obtained connection structure can be increased. Since the outer surface layer of the conductive layer in the conductive particles is a solder layer, for example, the contact area between the solder layer and the electrode can be increased by melting the solder layer by heating. Therefore, in the anisotropic conductive material according to the present invention, as compared with the anisotropic conductive material in which the outer surface layer of the conductive layer includes conductive particles that are metals other than a solder layer such as a gold layer or a nickel layer, The conduction reliability can be increased.

  In addition, since the base particles of the conductive particles are not particles formed of metal such as nickel or glass but resin particles formed of resin, the flexibility of the conductive particles can be increased. For this reason, the damage of the electrode which contacted the electroconductive particle can be suppressed. Furthermore, by using conductive particles having resin particles, a connection connected through the conductive particles as compared to the case of using conductive particles having particles formed of a metal such as nickel or glass. It is possible to enhance the thermal shock resistance against thermal shock such as a cold cycle of the structure.

  Further, all the components except for the linear expansion coefficient at 30 to 60 ° C. of the resin particles in the specific conductive particles and the conductive particles in the anisotropic conductive material using the specific conductive particles. When the absolute value of the difference from the linear expansion coefficient at 30 to 60 ° C. of the material containing 15 is 15 ppm / ° C. or less, the thermal shock resistance characteristics of the connection structure against a thermal shock such as a thermal cycle can be considerably improved.

  From the viewpoint of further improving the thermal shock resistance of the connection structure, all components except the linear expansion coefficient of the resin particles in the conductive particles at 30 to 60 ° C. and the conductive particles in the anisotropic conductive material The absolute value of the difference from the coefficient of linear expansion at 30 to 60 ° C. of the material containing is 0 ppm / ° C. or more, preferably 10 ppm / ° C. or less, more preferably 5 ppm / ° C. or less. What is the linear expansion coefficient at 30 to 60 ° C. of the resin particles in the conductive particles and the linear expansion coefficient at 30 to 60 ° C. of the material including all components except the conductive particles in the anisotropic conductive material? It may be the same.

  The linear expansion coefficient of the material containing all components except the conductive particles in the resin particles and the anisotropic conductive material can be measured as follows.

  A sheet-like sample prepared under the same formulation and polymerization conditions as the resin particles is prepared. Then, the linear expansion coefficient of the resin particles at 30 ° C. to 60 ° C. is measured using a heat / stress / strain measuring device (“EXSTAR TMA / SS120” manufactured by Seiko Instruments Inc.).

  Moreover, the material containing all the components except the said electroconductive particle in an anisotropic conductive material is prepared. When the binder resin is a curable compound, a cured product of a material including all components except for the conductive particles in the anisotropic conductive material is prepared. Then, using a heat / stress / strain measuring apparatus (“EXSTAR TMA / SS120” manufactured by Seiko Instruments Inc.), the linear expansion coefficient at 30 ° C. to 60 ° C. of the material or a cured product of the material is measured.

  When the binder resin is a curable compound, the linear expansion coefficient of the material including all components except the conductive particles in the anisotropic conductive material excludes the conductive particles in the anisotropic conductive material. It is preferably measured using a cured product obtained by curing the components at 200 ° C. for 10 minutes.

(Conductive particles)
In FIG. 1, the electroconductive particle contained in the anisotropic conductive material which concerns on one Embodiment of this invention is shown with sectional drawing.

  As shown in FIG. 1, the conductive particles 1 include resin particles 2 and a conductive layer 3 that covers the surface 2 a of the resin particles 2. The conductive particle 1 is a coated particle in which the surface 2 a of the resin particle 2 is coated with the conductive layer 3. Accordingly, the conductive particles 1 have the conductive layer 3 on the surface 1a.

  The conductive layer 3 includes a first conductive layer 4 covering the surface 2a of the resin particle 2, and a solder layer 5 (second conductive layer) covering the surface 4a of the first conductive layer 4. Have The outer surface layer of the conductive layer 3 is a solder layer 5. Thus, the conductive layer 3 may have a multilayer structure, or may have a multilayer structure of two layers or three or more layers.

  As described above, the conductive layer 3 has a two-layer structure. As in the modification shown in FIG. 2, the conductive particles 11 may have a solder layer 12 as a single conductive layer. The surface layer on the outer side of the conductive layer in the conductive particles may be a solder layer. However, the conductive particles 1 are preferable among the conductive particles 1 and the conductive particles 11 because the conductive particles can be easily produced.

  The method for forming the conductive layer 3 on the surface 2a of the resin particle 2 and the method for forming the solder layer on the surface 2a of the resin particle 2 or the surface of the conductive layer are not particularly limited. Examples of the method for forming the conductive layer 3 and the solder layers 5 and 12 include a method by electroless plating, a method by electroplating, a method by physical collision, a method by physical vapor deposition, and metal powder or metal powder and binder. And the like, and a method of coating the surface of the resin particles. Of these, electroless plating or electroplating is preferable. Examples of the method by physical vapor deposition include methods such as vacuum vapor deposition, ion plating, and ion sputtering. Further, in the method based on the physical collision, for example, a theta composer or the like is used.

  The method of forming the solder layers 5 and 12 is preferably a method by physical collision. The solder layers 5 and 12 are preferably formed by physical impact.

  Conventionally, the particle diameter of conductive particles having a solder layer on the outer surface layer of the conductive layer has been about several hundred μm. This is because the solder layer could not be formed uniformly even if conductive particles having a particle size of several tens of μm and the surface layer being a solder layer were obtained. On the other hand, by using a theta composer, even when conductive particles having a particle size of several tens of μm, particularly a particle size of 0.1 μm or more and a particle size of 50 μm or less are obtained, A solder layer can be uniformly formed on the surface of the conductive layer.

  The conductive layer 3 other than the solder layer is preferably formed of a metal. The metal constituting the conductive layer 3 other than the solder layer is not particularly limited. Examples of the metal include gold, silver, copper, platinum, palladium, zinc, lead, aluminum, cobalt, indium, nickel, chromium, titanium, antimony, bismuth, germanium and cadmium, and alloys thereof. In addition, tin-doped indium oxide (ITO) can also be used as the metal. As for the said metal, only 1 type may be used and 2 or more types may be used together.

  The first conductive layer 4 is preferably a nickel layer, a palladium layer, a copper layer, or a gold layer, more preferably a nickel layer, a copper layer, or a gold layer, and even more preferably a copper layer. The conductive particles preferably have a nickel layer, a palladium layer, a copper layer, or a gold layer, more preferably have a nickel layer, a copper layer, or a gold layer, and still more preferably have a copper layer. By using the conductive particles having these preferable conductive layers for the connection between the electrodes, the connection resistance between the electrodes can be further reduced. In addition, a solder layer can be more easily formed on the surface of these preferable conductive layers. Note that the first conductive layer 4 may be a solder layer. The conductive particles may have a plurality of solder layers.

  The thickness of the solder layers 5 and 12 is preferably 5 nm or more, more preferably 10 nm or more, further preferably 20 nm or more, preferably 70 μm or less, more preferably 40 μm or less, still more preferably 10 μm or less, and particularly preferably 5 μm or less. . When the thickness of the solder layers 5 and 12 is equal to or greater than the above lower limit, the conductivity is sufficiently high. When the thickness of the solder layers 5 and 12 is not more than the above upper limit, the difference in linear expansion coefficient between the resin particles 2 and the solder layers 5 and 12 becomes small, and the solder layers 5 and 12 are hardly peeled off.

  When the conductive layer has a multilayer structure, the total thickness of the conductive layer is preferably 10 nm or more, more preferably 20 nm or more, still more preferably 30 nm or more, preferably 70 μm or less, more preferably 40 μm or less, and even more preferably 10 μm. Hereinafter, it is particularly preferably 5 μm or less.

  Examples of the resin for forming the resin particles 2 include polyolefin resin, acrylic resin, phenol resin, melamine resin, benzoguanamine resin, urea resin, epoxy resin, unsaturated polyester resin, saturated polyester resin, polyethylene terephthalate, polysulfone, and polyphenylene. Examples thereof include oxides, polyacetals, polyimides, polyamideimides, polyetheretherketones, and polyethersulfones. Since the hardness of the resin particles 2 can be easily controlled within a suitable range, the resin for forming the resin particles 2 is a polymer obtained by polymerizing one or more polymerizable monomers having an ethylenically unsaturated group. It is preferably a coalescence.

  The average particle diameter of the conductive particles 1 and 11 is preferably 0.1 μm or more, more preferably 1 μm or more, preferably 100 μm or less, more preferably 80 μm or less, still more preferably 50 μm or less, and particularly preferably 40 μm or less. When the average particle diameter of the conductive particles 1 and 11 is not less than the above lower limit and not more than the above upper limit, the contact area between the conductive particles 1 and 11 and the electrode can be sufficiently increased, and a conductive layer is formed. It becomes difficult to form the conductive particles 1 and 11 aggregated together. Further, the distance between the electrodes connected via the conductive particles 1 and 11 does not become too large, and the conductive layer is difficult to peel off from the surface 2 a of the resin particle 2.

  Since the size is suitable for the conductive particles in the anisotropic conductive material and the distance between the electrodes can be further reduced, the average particle diameter of the conductive particles 1 and 11 is 0.1 μm or more and 50 μm. It is particularly preferred that

  The “average particle diameter” of the conductive particles 1 and 11 indicates the number average particle diameter. The average particle diameter of the conductive particles 1 and 11 is obtained by observing 50 arbitrary conductive particles with an electron microscope or an optical microscope and calculating an average value.

  The CV value (coefficient of variation of particle size distribution) of the conductive particles is preferably 10% or less, and more preferably 3% or less. When the CV value exceeds 10%, it is difficult to cause variations in the distance between the electrodes connected by the conductive particles.

  The CV value is represented by the following formula.

CV value (%) = (ρ / Dn) × 100
ρ: standard deviation of diameter of conductive particles Dn: average particle diameter

(Anisotropic conductive material)
The anisotropic conductive material according to the present invention includes the above-described conductive particles and a binder resin. That is, the conductive particles contained in the anisotropic conductive material according to the present invention have resin particles and a conductive layer covering the surface of the resin particles, and at least outside the conductive layer. The surface layer is a solder layer. The anisotropic conductive material according to the present invention is preferably in a liquid state and is preferably an anisotropic conductive paste.

  The binder resin is not particularly limited. As the binder resin, for example, an insulating resin is used. Examples of the binder resin include vinyl resins, thermoplastic resins, curable resins, thermoplastic block copolymers, and elastomers. As for the said binder resin, only 1 type may be used and 2 or more types may be used together.

  Specific examples of the vinyl resin include vinyl acetate resin, acrylic resin, and styrene resin. Specific examples of the thermoplastic resin include polyolefin resin, ethylene-vinyl acetate copolymer and polyamide resin. Specific examples of the curable resin include epoxy resins, urethane resins, polyimide resins and unsaturated polyester resins. The curable resin may be a room temperature curable resin, a thermosetting resin, a photocurable resin, or a moisture curable resin. Specific examples of the thermoplastic block copolymer include styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, hydrogenated product of styrene-butadiene-styrene block copolymer, and styrene- Examples include hydrogenated products of isoprene-styrene block copolymers. Specific examples of the elastomer include styrene-butadiene copolymer rubber and acrylonitrile-styrene block copolymer rubber.

  The binder resin is preferably a thermosetting compound. In this case, by heating at the time of electrically connecting the electrodes, the solder layer of conductive particles can be melted and the binder resin can be cured. For this reason, the connection between electrodes by a solder layer and the connection of the connection object member by binder resin can be performed simultaneously.

  From the viewpoint of further improving the thermal shock resistance of the connection structure, the thermosetting compound is preferably an epoxy compound.

  The anisotropic conductive material according to the present invention preferably contains a curing agent in order to cure the binder resin.

  The said hardening | curing agent is not specifically limited. Examples of the curing agent include imidazole curing agents, amine curing agents, phenol curing agents, polythiol curing agents, and acid anhydride curing agents. As for a hardening | curing agent, only 1 type may be used and 2 or more types may be used together.

  The anisotropic conductive material according to the present invention preferably further contains a flux. By using the flux, it becomes difficult to form an oxide film on the surface of the solder layer, and the oxide film formed on the surface of the solder layer or the electrode can be effectively removed.

  The flux is not particularly limited. As the flux, a flux generally used for soldering or the like can be used. Examples of the flux include zinc chloride, a mixture of zinc chloride and an inorganic halide, a mixture of zinc chloride and an inorganic acid, a molten salt, phosphoric acid, a derivative of phosphoric acid, an organic halide, hydrazine, an organic acid, and pine resin. Is mentioned. Only 1 type of flux may be used and 2 or more types may be used together.

  Examples of the molten salt include ammonium chloride. Examples of the organic acid include lactic acid, citric acid, stearic acid, glutamic acid, and hydrazine. Examples of the pine resin include activated pine resin and non-activated pine resin. The flux is preferably rosin. By using pine resin, the connection resistance between the electrodes can be lowered.

  The rosin is a rosin composed mainly of abietic acid. The flux is preferably rosins, and more preferably abietic acid. By using this preferable flux, the connection resistance between the electrodes can be further reduced.

  The said flux may be disperse | distributed in binder resin and may adhere on the surface of electroconductive particle.

  The anisotropic conductive material according to the present invention may contain a basic organic compound in order to adjust the activity of the flux. Examples of the basic organic compound include aniline hydrochloride and hydrazine hydrochloride.

  From the viewpoint of achieving both conductivity and insulation by the anisotropic conductive material, the content of the binder resin is preferably 30% by weight or more, more preferably 50% by weight or more in 100% by weight of the anisotropic conductive material. More preferably, it is 80% by weight or more, preferably 99.99% by weight or less, more preferably 99.9% by weight or less. When the content of the binder resin is not less than the above lower limit and not more than the above upper limit, a short circuit between adjacent electrodes can be further prevented, and the connection reliability of a connection target member connected by an anisotropic conductive material can be improved. It can be further increased.

  When a curing agent is used, the content of the curing agent is preferably 0.01 parts by weight or more, more preferably 0.1 parts by weight or more, preferably 100 parts by weight or less with respect to 100 parts by weight of the binder resin. More preferably, it is 50 parts by weight or less. When the content of the curing agent is not less than the above lower limit and not more than the above upper limit, the binder resin can be sufficiently cured, and a residue derived from the curing agent is less likely to occur after curing.

  In 100% by weight of the anisotropic conductive material, the content of the conductive particles is preferably 0.01% by weight or more, more preferably 0.1% by weight or more, preferably 20% by weight or less, more preferably 10% by weight. It is as follows. When the content of the conductive particles is not less than the above lower limit and not more than the above upper limit, short-circuiting between adjacent electrodes can be further prevented, and conduction reliability between the electrodes can be further enhanced.

  In 100% by weight of the anisotropic conductive material, the content of the flux is 0% by weight or more, preferably 0.5% by weight or more, preferably 30% by weight or less, more preferably 25% by weight or less. The anisotropic conductive material may not contain a flux. When the flux content is not less than the above lower limit and not more than the above upper limit, an oxide film is more difficult to be formed on the surface of the solder layer, and the oxide film formed on the solder layer or the electrode surface is more effective. Can be removed.

  The anisotropic conductive material according to the present invention includes, for example, a filler, an extender, a softener, a plasticizer, a polymerization catalyst, a curing catalyst, a colorant, an antioxidant, a heat stabilizer, a light stabilizer, an ultraviolet absorber, Various additives such as a lubricant, an antistatic agent or a flame retardant may be further contained.

  The method for dispersing the conductive particles in the binder resin is not particularly limited, and a conventionally known dispersion method can be used. Examples of the method for dispersing the conductive particles in the binder resin include, for example, a method in which the conductive particles are added to the binder resin and then kneaded and dispersed with a planetary mixer or the like. The conductive particles are dispersed in water or an organic solvent. After uniformly dispersing using a homogenizer, etc., adding into a binder resin, kneading and dispersing with a planetary mixer, etc., and after diluting the binder resin with water or an organic solvent, the conductive particles are The method of adding, kneading | mixing with a planetary mixer etc., and dispersing is mentioned.

  The anisotropic conductive material according to the present invention can be used as an anisotropic conductive paste, anisotropic conductive ink, anisotropic conductive adhesive, anisotropic conductive film, or anisotropic conductive sheet. When the anisotropic conductive material containing the conductive particles of the present invention is used as a film-like adhesive such as an anisotropic conductive film or an anisotropic conductive sheet, the film-like shape containing the conductive particles is used. A film-like adhesive that does not contain conductive particles may be laminated on the adhesive. However, as described above, the anisotropic conductive material according to the present invention is preferably in a liquid state, and is preferably an anisotropic conductive paste.

(Connection structure)
A connection structure can be obtained by connecting the connection target members using the anisotropic conductive material according to the present invention.

  The connection structure includes a first connection target member, a second connection target member, and a connection portion connecting the first and second connection target members, the connection portion according to the present invention. It is preferable that it is formed of an anisotropic conductive material. The first and second connection target members are preferably electrically connected.

  FIG. 3 is a front sectional view schematically showing a connection structure using an anisotropic conductive material according to an embodiment of the present invention.

  The connection structure 21 shown in FIG. 3 includes a first connection target member 22, a second connection target member 23, and a connection portion 24 connecting the first and second connection target members 22 and 23. Prepare. The connecting portion 24 is formed by curing an anisotropic conductive material including the conductive particles 1. In FIG. 3, the conductive particles 1 are schematically shown for convenience of illustration.

  A plurality of electrodes 22 b are provided on the upper surface 22 a of the first connection target member 22. A plurality of electrodes 23 b are provided on the lower surface 23 a of the second connection target member 23. The electrode 22b and the electrode 23b are electrically connected by one or a plurality of conductive particles 1. Accordingly, the first and second connection target members 22 and 23 are electrically connected by the conductive particles 1.

  The manufacturing method of the connection structure is not particularly limited. As an example of the manufacturing method of the connection structure, the anisotropic conductive material is disposed between the first connection target member and the second connection target member to obtain a laminate, and then the laminate is heated. And a method of applying pressure. The solder layer 5 of the conductive particles 1 is melted by heating and pressurization, and the electrodes are electrically connected by the conductive particles 1. Further, when the binder resin is a thermosetting compound, the binder resin is cured, and the first and second connection target members 22 and 23 are connected by the cured binder resin.

The pressure of the said pressurization is about 9.8-10 < ⁴ > -4.9 * 10 < ⁶ > Pa. The temperature of the said heating is about 120-220 degreeC.

  FIG. 4 is an enlarged front sectional view of a connection portion between the conductive particles 1 and the electrodes 22b and 23b in the connection structure 21 shown in FIG. As shown in FIG. 4, in the connection structure 21, by heating and pressurizing the laminated body, after the solder layer 5 of the conductive particles 1 is melted, the melted solder layer portion 5 a is sufficient with the electrodes 22 b and 23 b. To touch. That is, by using the conductive particles 1 whose surface layer is the solder layer 5, the conductive particles are compared with the case where the surface layer of the conductive layer is a metal such as nickel, gold or copper. 1 and the contact area between the electrodes 22b and 23b can be increased. For this reason, the conduction | electrical_connection reliability of the connection structure 21 can be improved. In general, the flux is gradually deactivated by heating.

  Specific examples of the connection target member include electronic components such as semiconductor chips, capacitors, and diodes, and circuit boards such as printed boards, flexible printed boards, and glass boards.

  Examples of the electrode provided on the connection target member include metal electrodes such as a gold electrode, a nickel electrode, a tin electrode, an aluminum electrode, a copper electrode, a molybdenum electrode, and a tungsten electrode. When the connection object member is a flexible printed board, the electrode is preferably a gold electrode, a nickel electrode, a tin electrode, or a copper electrode. When the connection target member is a glass substrate, the electrode is preferably an aluminum electrode, a copper electrode, a molybdenum electrode, or a tungsten electrode. In addition, when the said electrode is an aluminum electrode, the electrode formed only with aluminum may be sufficient and the electrode by which the aluminum layer was laminated | stacked on the surface of the metal oxide layer may be sufficient. Examples of the metal oxide include indium oxide doped with a trivalent metal element and zinc oxide doped with a trivalent metal element. Examples of the trivalent metal element include Sn, Al, and Ga.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. The present invention is not limited only to the following examples.

(Preparation Example 1 of Conductive Particles)
Resin particles having an average particle size of 20 μm (“Micropearl SP” manufactured by Sekisui Chemical Co., Ltd., linear expansion coefficient of 30 to 60 ° C .: 68 ppm / ° C.) are electroless nickel plated, and the surface of the resin particles has a thickness of 0.3 μm. A base nickel plating layer was formed. Next, the resin particles on which the base nickel plating layer was formed were subjected to electrolytic copper plating to form a 1 μm thick copper layer. Thereafter, using a theta composer (manufactured by Tokuju Kogakusha Co., Ltd.), on the surface of the copper layer of the obtained particles, solder fine powder (average particle diameter of 3 μm including 42 wt% tin and 58 wt% bismuth) is applied. By melting, a 1 μm thick solder layer was formed on the surface of the copper layer. Thus, a 1 μm thick copper layer is formed on the surface of the resin particles, and a 1 μm thick solder layer (tin: bismuth = 42 wt%: 58 wt%) is formed on the surface of the copper layer. Conductive particles A were produced.

  In addition, the linear expansion coefficient at 30 to 60 ° C. of the resin particles used in Preparation Example 1 of the conductive particles is prepared by separately preparing a sheet-like sample having the same composition and the same polymerization conditions as the above resin particles. It measured using the distortion measuring apparatus ("EXSTAR TMA / SS120" by Seiko Instruments Inc.). The linear expansion coefficient at 30 to 60 ° C. of the resin particles used in Production Example 2 of conductive particles described later was also measured in the same manner.

(Preparation Example 2 of Conductive Particles)
Resin particles having an average particle size of 20 μm (“Micropearl LP” manufactured by Sekisui Chemical Co., Ltd., linear expansion coefficient of 30 to 60 ° C .: 85 ppm / ° C.) are electroless nickel plated, and the surface of the resin particles has a thickness of 0.3 μm. A base nickel plating layer was formed. Next, the resin particles on which the base nickel plating layer was formed were subjected to electrolytic copper plating to form a 1 μm thick copper layer. Thereafter, using a theta composer (manufactured by Tokuju Kogakusha Co., Ltd.), on the surface of the copper layer of the obtained particles, solder fine powder (average particle diameter of 3 μm including 42 wt% tin and 58 wt% bismuth) is applied. By melting, a 1 μm thick solder layer was formed on the surface of the copper layer. Thus, a 1 μm thick copper layer is formed on the surface of the resin particles, and a 1 μm thick solder layer (tin: bismuth = 42 wt%: 58 wt%) is formed on the surface of the copper layer. Conductive particles B were produced.

Example 1
50 parts by weight of G-0250S (manufactured by NOF Corporation), 50 parts by weight of HP-7200HH (manufactured by DIC), 10 parts by weight of 2 MAOK (manufactured by Shikoku Kasei Kogyo Co., Ltd.), and 10 parts by weight of the conductive particles A obtained in Production Example 1 Parts were dispersed in methyl ethyl ketone, and a coating film was formed on the PET film to obtain an anisotropic conductive material. In addition, the linear expansion coefficient in 30-60 degreeC of the hardened | cured material of the material containing all the components except electroconductive particle was 66 ppm / degreeC. The linear expansion coefficient at 30 to 60 ° C. of the cured product of the material including all components except the conductive particles is separately from the cured product obtained by heating the sample obtained by removing the conductive particles from the anisotropic conductive material at 200 ° C. for 10 minutes. Prepared and measured using a heat / stress / strain measuring device (“EXSTAR TMA / SS120” manufactured by Seiko Instruments Inc.). The linear expansion coefficient at 30 to 60 ° C. of the cured product including all components excluding the conductive particles described later was also measured in the same manner.

(Example 2)
50 parts by weight of G-2050M (manufactured by NOF Corporation), 50 parts by weight of EOCN-1020-55 (manufactured by Nippon Kayaku Co., Ltd.), 40 parts by weight of YH-306 (manufactured by Mitsubishi Chemical Corporation), 2MAOK (manufactured by Shikoku Kasei Kogyo Co., Ltd.) 5 parts by weight and 15 parts by weight of the conductive particles A obtained in Preparation Example 1 were dispersed in methyl ethyl ketone and coated onto a PET film to obtain an anisotropic conductive material. In addition, the linear expansion coefficient in 30-60 degreeC of the hardened | cured material of the material containing all the components except electroconductive particle was 75 ppm / degreeC.

(Example 3)
50 parts by weight of G-2050M (manufactured by NOF Corporation), 50 parts by weight of HP-7200HH (manufactured by DIC), 50 parts by weight of HNA-100 (manufactured by Shin Nippon Chemical Co., Ltd.), 5 parts by weight of 2 MAOK (manufactured by Shikoku Kasei Kogyo Co., Ltd.) And 15 parts by weight of the conductive particles A obtained in Preparation Example 1 were dispersed in methyl ethyl ketone and coated onto a PET film to obtain an anisotropic conductive material. In addition, the linear expansion coefficient in 30-60 degreeC of the hardened | cured material of the material containing all the components except electroconductive particle was 82 ppm / degrees C.

Example 4
An anisotropic conductive material was obtained in the same manner as in Example 2 except that the conductive particles A obtained in Production Example 1 were changed to the conductive particles B obtained in Production Example 2.

(Example 5)
An anisotropic conductive material was obtained in the same manner as in Example 3 except that the conductive particles A obtained in Production Example 1 were changed to the conductive particles B obtained in Production Example 2.

(Comparative Example 1)
Solder particles (tin: bismuth = 43 wt%: 57 wt%, average particle diameter 20 μm) were prepared. An anisotropic conductive material was obtained in the same manner as in Example 1 except that the conductive particles A obtained in Preparation Example 1 were changed to the solder particles.

(Comparative Example 2)
Solder particles (tin: bismuth = 42 wt%: 58 wt%, average particle diameter 20 μm) were prepared. An anisotropic conductive material was obtained in the same manner as in Example 3 except that the conductive particles A obtained in Production Example 1 were changed to the solder particles.

(Comparative Example 3)
By stirring 100 parts by weight of Epicoat 828 (manufactured by Mitsubishi Chemical Corporation), 40 parts by weight of MH-700 (manufactured by Shin Nippon Chemical Co., Ltd.), and 15 parts by weight of the conductive particles A obtained in Preparation Example 1, Obtained material. In addition, the linear expansion coefficient in 30-60 degreeC of the hardened | cured material of the material containing all the components except electroconductive particle was 104 ppm / degrees C.

(Comparative Example 4)
An anisotropic conductive material was obtained in the same manner as in Example 1 except that the conductive particles A obtained in Production Example 1 were changed to the conductive particles B obtained in Production Example 2.

(Comparative Example 5)
An anisotropic conductive material was obtained in the same manner as in Comparative Example 3 except that the conductive particles A obtained in Production Example 1 were changed to the conductive particles B obtained in Production Example 2.

(Evaluation)
(1) Production of Connection Structure An FR-4 substrate having a gold electrode pattern with L / S of 300 μm / 300 μm formed on the upper surface was prepared. In addition, a polyimide substrate (flexible substrate) having a gold electrode pattern with L / S of 300 μm / 300 μm formed on the lower surface was prepared.

  An anisotropic conductive material layer was formed on the upper surface of the FR-4 substrate so as to have a thickness of 40 μm by using the obtained anisotropic conductive material.

  Next, a polyimide substrate (flexible substrate) was laminated on the upper surface of the anisotropic conductive material layer so that the electrodes face each other. Then, while adjusting the head temperature so that the temperature of the anisotropic conductive material layer becomes 200 ° C., a pressure heating head is placed on the upper surface of the semiconductor chip, and the anisotropic conductive material layer is cured while melting the solder. To obtain a connection structure.

(2) Insulation test between electrodes adjacent in the lateral direction In the obtained connection structure, the presence or absence of leakage between adjacent electrodes was evaluated by measuring resistance with a tester. When the resistance exceeded 500 MΩ, it was determined that there was no leakage, and the result was “◯”. When the resistance was 500 MΩ or less, the result was determined as having leakage, and the result was determined as “X”.

(3) Conductivity test between upper and lower electrodes The connection resistance between the upper and lower electrodes of the obtained connection structure was measured by a four-terminal method, respectively. The average value of the two connection resistances was calculated. Note that the connection resistance can be obtained by measuring the voltage when a constant current is passed from the relationship of voltage = current × resistance. The case where the average value of the connection resistance was 2.0Ω or less was judged as “◯”, and the case where the average value of the connection resistance exceeded 2Ω was judged as “X”.

(4) Thermal shock characteristics Process of preparing 20 each of the obtained connection structures, holding at −30 ° C. for 30 minutes, then raising the temperature to 80 ° C., holding for 30 minutes, and then lowering the temperature to −30 ° C. A cold cycle test was carried out with 1 cycle. Ten connection structures were taken out after 500 cycles and 1000 cycles, respectively.

  It was evaluated whether 10 connection structures after 500 cycles of the thermal cycle test and 10 connection structures after 1000 cycles of the thermal cycle test had poor conduction between the upper and lower electrodes. Of the 10 connection structures, the case where the number of defective conductions was 1 or less was judged as “◯”, and the case where it was 2 or more was judged as “x”.

  Further, as a harsher condition, holding at −40 ° C. for 30 minutes, then raising the temperature to 125 ° C., holding for 30 minutes, and then lowering the temperature to −30 ° C. in one cycle is performed with 500 cycles and It implemented similarly to 1000 cycles.

  The results are shown in Table 1 below. In Table 1 below, “−” indicates that evaluation is not performed. Moreover, in the following Table 1, the thermal cycle test result of -30 degreeC-80 degreeC is shown as a thermal shock characteristic (1), and the thermal cycle test result of -40 degreeC-125 degreeC is shown as a thermal shock characteristic (2).

  As shown in Table 1, in the connection structure using the anisotropic conductive material in which the conductive particles of Examples 1 to 5 are dispersed, there is no leakage between the electrodes adjacent in the horizontal direction, and there is no gap between the upper and lower electrodes. It turns out that it is connected enough. Furthermore, it can be seen that the connection structures using the anisotropic conductive materials of Examples 1 to 5 are excellent in thermal shock resistance.

DESCRIPTION OF SYMBOLS 1 ... Conductive particle 1a ... Surface 2 ... Resin particle 2a ... Surface 3 ... Conductive layer 4 ... 1st conductive layer 4a ... Surface 5 ... Solder layer 5a ... Molten solder layer part 11 ... Conductive particle 12 ... Solder layer 21 ... Connection structure 22 ... First connection target member 22a ... Upper surface 22b ... Electrode 23 ... Second connection target member 23a ... Lower surface 23b ... Electrode 24 ... Connection portion

Claims (6)

Containing conductive particles and a binder resin,
The conductive particles have resin particles and a conductive layer covering the surface of the resin particles, and at least the outer surface layer of the conductive layer is a solder layer,
The linear expansion coefficient at 30 to 60 ° C. of the resin particles in the conductive particles and the linear expansion coefficient at 30 to 60 ° C. of the material including all components except the conductive particles in the anisotropic conductive material. An anisotropic conductive material having an absolute difference of 15 ppm / ° C. or less. The binder resin is a curable compound;
The linear expansion coefficient of the material including all components except the conductive particles in the anisotropic conductive material is the linear expansion coefficient of the cured product of the material including all components except the conductive particles in the anisotropic conductive material. The anisotropic conductive material according to claim 1, wherein   The anisotropic conductive material according to claim 1, wherein the binder resin is an epoxy compound.   The anisotropic conductive material of any one of Claims 1-3 whose average particle diameter of the said electroconductive particle is 0.1 micrometer or more and 50 micrometers or less.   The anisotropic conductive material of any one of Claims 1-4 which further contains a flux. A first connection target member;
A second connection target member;
A connecting portion connecting the first and second connection target members;
The connection structure in which the said connection part is formed with the anisotropic conductive material of any one of Claims 1-5.

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