JP5472369B2 - Conductive particles, insulating coated conductive particles and manufacturing method thereof, anisotropic conductive adhesive - Google Patents

Description

  The present invention relates to conductive particles, insulating coated conductive particles, a method for producing the same, and an anisotropic conductive adhesive.

  The method of mounting a liquid crystal driving IC on a liquid crystal display glass panel can be broadly classified into two types, COG (Chip-on-Glass) mounting and COF (Chip-on-Flex). In COG mounting, an IC for liquid crystal is directly bonded onto a glass panel using an anisotropic conductive adhesive containing conductive particles. On the other hand, in COF mounting, a liquid crystal driving IC is bonded to a flexible tape having metal wiring, and these are bonded to a glass panel using an anisotropic conductive adhesive containing conductive particles. The anisotropy referred to here means conduction in the pressing direction and insulation in the non-pressing direction.

  However, along with the recent high definition of liquid crystal display, gold bumps, which are circuit electrodes of liquid crystal driving ICs, have narrowed pitch and narrowed area. Therefore, a circuit in which conductive particles of anisotropic conductive adhesive are adjacent to each other. There is a problem that a short circuit occurs between the electrodes. When conductive particles flow out between adjacent circuit electrodes, the number of conductive particles in the anisotropic conductive adhesive captured between the gold bump and the glass panel decreases, and the connection resistance between the opposing circuit electrodes increases. There was a problem of poor connection.

  Therefore, as a method for solving these problems, a method for preventing deterioration in bonding quality in COF mounting or COF mounting by forming an insulating adhesive on at least one side of the anisotropic conductive adhesive (Patent Document 1). A method of covering the entire surface of the conductive particles with an insulating film (Patent Document 2) has been proposed.

  In addition, methods for coating the surface of gold particles with insulating child particles have been proposed (Patent Documents 3 and 4). In the method described in Patent Document 4, a process of forming a functional group on a metal surface by treating with a compound having either a mercapto group, a sulfide group, or a disulfide group on the gold surface of the particle is provided. The formation of the group is aimed at.

  Further, as an attempt to improve the conductivity of conductive particles, there is a method of performing copper / gold plating on resin fine particles (Patent Document 5). In addition, conductive particles coated with nickel and gold on a metal layer containing 50% by weight or more of copper (Patent Document 6), metal coated particles having a gold content in the metal-coated phase of 90% by weight or more (Patent Document) 7) is known.

JP-A-8-279371 JP-A-8-335407 JP-A-4-259766 International Publication WO2003 / 02955 JP 2006-28438 A JP 2001-155539 A JP 2005-36265 A

However, in the method of forming an insulating adhesive on one side of the circuit connection member, when the bump area is less than 3000 μm ² and the conductive particles are increased in order to obtain a stable connection resistance, the insulation between adjacent electrodes There is still room for improvement in sex. Furthermore, the method of covering the entire surface of the conductive particles with an insulating coating has a problem that the conductivity tends to be low although the insulating property is high.

  Metal-coated particles having a gold content of 90% by weight or more in the metal-coated phase are good in terms of reliability, but cost is high, and in recent years, the gold content tends to be lowered and is hardly practical. Although the copper plating particles are excellent in terms of conductivity and cost, there is a problem from the viewpoint of moisture absorption resistance because they easily migrate. Attempts have been made to compensate for the shortcomings of both (gold and copper), but none of them are perfect.

  As pointed out in Patent Document 7, there is a problem that copper migrates into gold. In particular, when blended with an acidic resin, migration easily occurs when moisture is absorbed, and gold is insufficient as a copper stopper.

  Cu / Ni / Au particles and Cu / Ni particles are superior to Cu / Au particles in terms of migration resistance. However, it has been found that the use of nickel for the copper stopper layer causes problems when subsequently forming an insulating layer on the metal.

  In the method of coating the surface of the Cu / Ni / Au particles with the insulating child particles, it is desirable that the nickel surface is completely covered with gold. However, when the average film thickness of gold is thin (for example, 300 mm or less), it is difficult for gold to completely cover the metal inside the gold (usually nickel). In recent years, from the viewpoint of cost reduction, the gold film thickness tends to be reduced. Since nickel which is not a noble metal forms an oxide film, it is difficult to form an insulating film if nickel is exposed. In order to perform the insulating coating process firmly, the stopper layer is preferably a noble metal.

  Further, when nickel is used for the stopper layer, it is likely to be oxidized in the plating process, which often causes defects in the plating appearance, and it is also desirable that the stopper layer is a noble metal.

  Further, in the method of covering the surface of the conductive particles with the insulating child particles, it is necessary to use the child particles made of resin such as acrylic because of the problem of adhesion between the child particles and the conductive particles. In that case, the resin-made child particles become conductive by melting at the time of thermocompression bonding. Therefore, it has been found that there is a problem that the conductivity tends to be low as in the method of covering the entire surface of the conductive particles with an insulating coating.

  For the above reason, the insulating child particles are suitable, for example, inorganic oxides having relatively high hardness and high melting temperature. For example, in the method described in Patent Document 4, the silica surface is treated with 3-isocyanatopropyltriethoxysilane, and the silica having an isocyanate group on the surface is reacted with the conductive particles having an amino group on the surface. However, it is generally considered difficult to modify the surface of particles having a particle diameter of 500 nm or less with a functional group, and inorganic oxides such as silica are used during centrifugation or filtration after modification with a functional group. The problem of agglomeration tends to occur. Furthermore, in the method described in Patent Document 4, it is difficult to control the coverage of the insulating child particles.

  The present invention has been made in view of such circumstances, and an object of the present invention is to use conductive particles capable of realizing a highly reliable anisotropic conductive film excellent in conductivity and insulation, and use of the conductive particles. An object of the present invention is to provide an insulating coated conductive particle, a method for producing the same, and an anisotropic conductive adhesive using the insulating coated conductive particle.

  In order to solve the above-mentioned problem, the present invention comprises resin particles and a metal layer provided on the surface of the resin particles, and the metal layer contains copper or a copper alloy in the order closer to the resin particles. Provided is a conductive particle having a structure in which one layer and a second layer containing palladium are laminated.

  The present invention also includes resin particles and a metal layer provided on the surface of the resin particles, wherein the metal layer is in the order closer to the resin particles, the first layer containing copper or a copper alloy, and palladium. Provided is a conductive particle characterized in that it has a structure in which a second layer containing bismuth and a third layer containing gold are laminated.

  The second layer is preferably a reduction plating type palladium layer, and the third layer is preferably a reduction plating type gold layer.

  The thickness of the first layer is preferably 300 mm or more, and the thickness of the second layer is preferably 100 mm or more.

  The copper / (gold + palladium) ratio in the metal layer is preferably 0.4 or less.

  Moreover, it is preferable that the average particle diameter of the electroconductive particle of this invention is 2-4 micrometers.

  The present invention also provides insulating coated conductive particles, wherein at least a part of the surface of the metal layer of the conductive particles of the present invention is coated with insulating particles.

  Further, in the present invention, at least a part of the metal layer surface of the conductive particle of the present invention is coated with a polymer electrolyte, and the surface of the metal layer coated with the polymer electrolyte is further coated with insulator particles. Insulating coated conductive particles are provided.

  The polymer electrolyte is preferably a polyamine, and more preferably polyethyleneimine.

  The metal surface of the conductive particles is preferably treated with a compound having a functional group of mercapto group, sulfide group, or disulfide group before coating with the polymer electrolyte or insulator particles.

In the present invention, the surface of the metal layer of the conductive particle of the present invention is treated with a compound having at least one functional group selected from a mercapto group, a sulfide group and a disulfide group, thereby forming the functional group on the surface of the metal layer. A first step of:
A second step of treating the metal layer surface of the conductive particles treated in the first step with the insulator particles and coating at least a part of the metal layer surface with the insulator particles;
A method for producing insulation-coated conductive particles is provided.

  Insulating coated conductive particles of the present invention are obtained by treating the surface of the conductive particles treated in the first step with a polymer electrolyte between the first step and the second step. It is preferable to further include a third step of covering at least a part with the polymer electrolyte.

  The polymer electrolyte used in the above production method is preferably polyamines, and more preferably polyethyleneimine.

  The conductive particles used in the first step preferably have at least one functional group selected from a hydroxyl group, a carboxyl group, an alkoxyl group, and an alkoxycarbonyl group on the surface of the metal layer.

  Insulator particles used in the above production method are preferably inorganic oxides, and more preferably silica particles.

  The present invention also provides an anisotropic conductive adhesive obtained by dispersing the insulating coated conductive particles of the present invention in an adhesive.

  According to the present invention, conductive particles capable of realizing a highly reliable anisotropic conductive film excellent in conductivity and insulation, insulating coated conductive particles using the conductive particles, a method for producing the same, and the insulating coated conductive An anisotropic conductive adhesive using particles can be provided.

It is sectional drawing which shows the manufacturing method of the connection structure using an anisotropic conductive adhesive.

  Hereinafter, preferred embodiments of the present invention will be described in detail.

  The conductive particles of the present invention include resin particles and a metal layer provided on the surface of the resin particles, and the metal layer contains copper or a copper alloy in the order closer to the resin particles. It has a structure in which a layer and a second layer containing palladium are laminated. The average particle size of the conductive particles needs to be smaller than the minimum interval between the electrodes of the substrate, and when there is a variation in the height of the electrodes, it is preferable that the average particle size is larger than the variation in height. The range of 1-10 micrometers is preferable by the said concept, and the range of 2-4 micrometers is more preferable.

  Resin particles constituting the core of the conductive particles (also referred to as “organic core particles”) are not particularly limited, but acrylic resins such as polymethyl methacrylate and polymethyl acrylate, polyolefin resins such as polyethylene, polypropylene, polyisobutylene and polybutadiene, etc. Is mentioned.

  Moreover, the 1st layer provided in the side close | similar to a resin particle among the metal layers provided in the surface of a resin particle is comprised including copper or a copper alloy. Copper has flexibility and ductility, and does not easily cause metal cracking or the like even after compression. In addition, when the inorganic fine particles or the like are coated with insulation, the inorganic fine particles are likely to be embedded in the copper, thereby easily exhibiting conductivity. Furthermore, copper is excellent in terms of cost, ease of handling of the plating solution, and the like. As the copper alloy, an alloy of copper and nickel can be used. Copper alloys are superior in terms of adhesive strength to resin particles compared to copper. When using a copper alloy, from the viewpoint of conductivity, the copper content is preferably 70% by weight or more, and more preferably in the range of 90 to 100% by weight.

  The thickness of the first layer is preferably in the range of 300 to 2000 mm, and more preferably in the range of 300 to 1000 mm. If the thickness of the first layer is less than 300 mm, the conductivity tends to decrease. On the other hand, if the thickness exceeds 1000 mm, it tends to aggregate during plating.

  The first layer can be formed through a copper plating process, for example. As a copper plating process, it is preferable to first apply a palladium catalyst before performing copper plating, and then perform electroless copper plating.

  The composition of the electroless copper plating includes (i) a water-soluble copper salt such as copper sulfate, (ii) a reducing agent such as formalin, (iii) a complexing agent such as Rochelle salt, EDTA, (iv) an alkali hydroxide, etc. What added the pH adjuster of is preferable.

  Further, a copper reducing agent such as sodium hypophosphite, sodium borohydride, dimethylamine borane, hydrazine may be used.

  Also, amino acids such as citric acid, tartaric acid, hydroxyacetic acid, malic acid, lactic acid, gluconic acid and glycine, amines such as ethylenediamine and alkylamine, and other copper complexing agents such as ammonium, EDTA and pyrophosphoric acid may be used. Good.

  Alloy plating can also be performed by using another metal ion source such as nickel sulfate in the plating solution. In particular, if a very small amount of nickel is added, the bond strength between the resin and the metal increases, so it is preferable to add nickel depending on the situation.

  It is desirable that the washing with water after the electroless copper plating is completed efficiently in a short time. The shorter the washing time, the more difficult it is to form an oxide film on the copper surface.

  A second layer containing palladium is formed on the first layer. The second layer functions as a copper migration stop layer. The thickness of the second layer is preferably from 100 to 1000 mm, and more preferably from 100 to 300 mm. If the thickness of the second layer is less than 100 mm, the second layer becomes sparse when the second layer is formed by plating or the like, and the effect as a copper migration stop layer tends to be reduced. On the other hand, when the thickness of the second layer exceeds 1000 mm, the manufacturing cost tends to increase.

  The second layer can be formed, for example, through a palladium plating step, and the second layer is preferably an electroless plating type palladium layer. For electroless palladium plating, either a substitution type (a type that does not contain a reducing agent) or a reduction type (a type that contains a reducing agent) may be used. Examples of such electroless palladium plating include APP (Ishihara Pharmaceutical Co., Ltd., trade name) for the reduction type, and MCA (trade name, manufactured by World Metal Co., Ltd.) for the replacement type.

  When the substitution type and the reduction type are compared, the reduction type is particularly preferable because voids tend to decrease. Since displacement plating precipitates while dissolving the inner metal, the coating area is less likely to increase compared to the reduced type.

  A third layer containing gold is provided on the second layer. By providing such a third layer, the surface resistance of the conductive particles can be lowered and the characteristics can be improved. The thickness of the third layer is preferably 0 mm or more and 300 mm or less from the viewpoint of the balance between the effect of reducing the surface resistance of the conductive particles and the manufacturing cost, but even if it is 300 mm or more, there is no problem in characteristics.

  The third layer can be formed through a gold plating process, for example. As the gold plating, substitutional gold plating such as HGS-100 (Hitachi Chemical Industry, trade name) or reduction-type electroless copper plating such as HGS-2000 (Hitachi Chemical Industry, trade name) can be used.

  When the substitution type and the reduction type are compared, the reduction type is particularly preferable because voids tend to decrease. Since displacement plating precipitates while dissolving the inner metal, the coating area is less likely to increase compared to the reduced type.

  As described above, the conductive particles of the present invention may have a structure in which the outer side of the resin particles is covered with copper plating having a thickness of 300 mm or more, and the outer side thereof is covered with palladium plating having a thickness of 100 mm or more, and appropriately covered with gold plating. The thickness referred to here is an average value of thicknesses obtained by dissolving the sample in hydrofluoric acid or the like and then converting the value measured by atomic absorption, ICP or the like into thickness. When electroless copper plating with a uniform thickness is performed at a thickness of about 300 mm, it is specified by XPS (X-ray Photoelectron Spectroscopy, also referred to as ESCA) as an index that changes to direct thickness measurement. The element ratio of was measured. When the copper / (palladium + gold) ratio (copper ratio when the ratio of palladium + gold is 1) of the palladium-coated copper-plated particles of 100% or less was measured by XPS, all showed values exceeding 0.4. I understood that. Therefore, in the present invention, the copper / (palladium + gold) ratio is preferably 0.4 or less. Here, the reason for measuring the ratio is that XPS in air is easily affected by foreign matters on the metal. Copper / (palladium + gold) here is a measurement result by XPS to the last. Since the measurement result by XPS is also strictly different depending on the measurement device or the like, in this application, the measurement method according to the method of Table 1 is used.

  As a method for decreasing the copper / (palladium + gold) ratio, the following methods can be considered in addition to increasing the film thickness of palladium or gold.

  The copper / (palladium + gold) ratio can be lowered by shortening the washing time after plating (specifically, within 120 seconds at room temperature) or shortening the filtration time. Moreover, it can also wash | clean with the washing | cleaning liquid containing EDTA and cyan after palladium or gold plating.

  A step of removing copper by plasma or other physical methods is also possible.

  By passing through the above processes, copper / (palladium + gold) can be made 0.4 or less.

  The copper / palladium particles and copper / palladium / gold particles produced as described above can be used as a constituent material of the anisotropic conductive adhesive as they are. Also in this case, the migration property is improved as compared with the conventional copper-containing particles. Further, the conductivity is improved as compared with the conventional Ni / Au particles.

  Next, the insulating coated conductive particles of the present invention will be described. The coated particles of the present invention are those in which at least a part of the metal layer surface of the conductive particles of the present invention is coated with insulator particles. In recent years, anisotropic conductive adhesives for COG have been required to have insulation reliability at a narrow pitch of 10 μm, so in order to further improve insulation reliability, copper / palladium particles and copper / palladium / gold particles are used. It is necessary to apply insulation coating. According to the insulating coated conductive particles of the present invention, such required characteristics can be effectively realized.

  As the insulator particles coated on the conductive particles, inorganic oxide fine particles are preferable. Note that when organic fine particles are used, the insulator particles are deformed in the manufacturing process of the anisotropic conductive adhesive, and the characteristics are easily changed.

As the inorganic oxide fine particles, oxides containing each element of silicon, aluminum, zirconium, titanium, niobium, zinc, tin, cerium, and magnesium are preferable, and these may be used alone or in combination of two or more. it can. Among inorganic oxides, water-dispersed colloidal silica (SiO ₂ ) is particularly suitable because it has a hydroxyl group on the surface, and thus has excellent properties such as excellent bonding with conductive particles, easy alignment of particle diameters, and low cost. Examples of such commercially available inorganic oxide fine particles include Snowtex, Snowtex UP (manufactured by Nissan Chemical Industries), Quatron PL series (manufactured by Fuso Chemical Industries), and the like. In terms of insulation reliability, the concentration of alkali metal ions and alkaline earth metal ions in the dispersion solution is desirably 100 ppm or less, preferably an inorganic oxidation produced by a hydrolysis reaction of metal alkoxide, a so-called sol-gel method. Fine particles are suitable.

  As for the size of the inorganic oxide fine particles, the particle diameter measured by the specific surface area conversion method by the BET method or the X-ray small angle scattering method is preferably 20 to 500 nm. If the particle diameter is less than 20 nm, the inorganic fine particles adsorbed on the conductive particles do not act as an insulating film, and a short circuit tends to occur in part. On the other hand, when it exceeds 500 nm, the conductivity in the pressurizing direction of the connection tends to be lowered.

  The hydroxyl group on the surface of the inorganic oxide can be modified to an amino group, a carboxyl group or an epoxy group with a silane coupling agent or the like, but it is difficult when the particle size of the inorganic oxide is 500 nm or less. Therefore, it is desirable to coat the conductive particles without modifying the functional group.

  In general, a hydroxyl group can form a strong bond with a hydroxyl group, a carboxyl group, an alkoxyl group, or an alkoxycarbonyl group. Examples of the mode of bonding between the hydroxyl group and these functional groups include covalent bonding by dehydration condensation and hydrogen bonding. Therefore, these functional groups are preferably formed on the surface of the conductive particles.

  When the conductive particle surface has a gold or palladium surface, it is a compound having any of a mercapto group, sulfide group, or disulfide group that forms a coordinate bond with gold, and has a hydroxyl group, carboxyl group, alkoxyl group, alkoxycarbonyl on the gold surface. It is good to form a group. Specific examples include mercaptoacetic acid, 2-mercaptoethanol, methyl mercaptoacetate, mercaptosuccinic acid, thioglycerin, and cysteine. When the copper / (palladium + gold) ratio on the gold surface is 0.4 or less, the functional group can be firmly formed on the surface of the conductive particles.

  Precious metals such as gold, palladium, and copper easily react with thiols, and base metals such as nickel hardly react with thiols. Therefore, the copper / palladium particles and copper / palladium / gold particles of the present invention are more likely to react with thiols than conventional nickel / gold particles. In particular, nickel / gold particles tend to have a high nickel ratio on the particle surface when the gold thickness is 300 mm or less.

  The method for treating the above compound on the gold surface is not particularly limited, but a compound such as mercaptoacetic acid is dispersed in an amount of about 10 to 100 mmol / l in an organic solvent such as methanol or ethanol, and the copper / palladium particles of the present invention are dispersed therein. Disperse copper / palladium / gold particles.

  Next, the surface of the conductive particles having a functional group is coated with an inorganic oxide. The surface potential (zeta potential) of the conductive particles having a hydroxyl group, a carboxyl group, an alkoxyl group, or an alkoxycarbonyl group is usually (pH is in a neutral region). If so) negative. On the other hand, the surface potential of an inorganic oxide having a hydroxyl group is usually negative. It is difficult to coat particles having a negative surface potential around particles having a negative surface potential.

  Therefore, a method of alternately laminating a polymer electrolyte and an inorganic oxide is preferable. As a more specific production method, conductive particles having a functional group are (1) dispersed in a polymer electrolyte solution, the polymer electrolyte is adsorbed on the surface of the conductive particles, and then rinsed; (2) conductive particles Is dispersed in a dispersion solution of inorganic oxide fine particles, and after the inorganic fine particles are adsorbed on the surface of the conductive particles, a rinsing process is performed, so that the surface is insulated with a polymer electrolyte and inorganic oxide fine particles laminated. Fine particles coated with a coating can be produced. Such a method is called an alternating lamination method (Layer-by-Layer assembly). The alternate lamination method is described in G.H. This is a method of forming an organic thin film published in 1992 by Decher et al. (Thin Solid Films, 210/211, p831 (1992)). In this method, a polycation adsorbed on a substrate by electrostatic attraction by alternately immersing the base material in an aqueous solution of a polymer electrolyte having a positive charge (polycation) and a polymer electrolyte having a negative charge (polyanion). A combination of polyanions is laminated to obtain a composite film (alternate laminated film).

  In the alternating layering method, the film is grown by attracting the charge of the material formed on the substrate and the material having the opposite charge in the solution by electrostatic attraction, so that the adsorption proceeds and the charge is neutralized. When this occurs, no further adsorption occurs. Therefore, when reaching a certain saturation point, the film thickness does not increase any more. Lvov et al. Applied the alternate lamination method to fine particles and reported a method of laminating a polymer electrolyte having a charge opposite to the surface charge of the fine particles by using the fine particle dispersions of silica, titania and ceria. (Langmuir, Vol. 13, (1997) p6195-6203). By using this method, silica fine particles having a negative surface charge and polydiallyldimethylammonium chloride (PDDA) or polyethyleneimine (PEI), which are polycations having the opposite charge, are alternately laminated to form silica. It is possible to form a fine particle laminated thin film in which fine particles and a polymer electrolyte are alternately laminated.

  After immersing in the dispersion of the polymer electrolyte solution or inorganic oxide fine particles, before immersing in the fine particle dispersion or polymer electrolyte solution having the opposite charge, the excess polymer electrolyte solution or inorganic oxide fine particles are rinsed only with a solvent. It is preferred to wash away the dispersion. Examples of such rinsing include water, alcohol, and acetone. Usually, the specific resistance value is 18 MΩ · cm or more from the viewpoint of removing an excessive polymer electrolyte solution or a dispersion of inorganic oxide fine particles. Ion exchange water (so-called ultrapure water) is used. Since the polymer electrolyte and inorganic oxide fine particles adsorbed on the conductive particles are electrostatically adsorbed on the surface of the conductive particles, they are not peeled off in this rinsing step. In addition, it is preferable to perform rinsing in order to prevent the polymer electrolyte or inorganic oxide fine particles not adsorbed from being brought into the solution having the opposite charge. If this is not done, cations and anions may be mixed in the solution by bringing them in, which may cause aggregation and precipitation of the polymer electrolyte and the inorganic oxide fine particles.

  The polymer electrolyte solution used in the present invention is dissolved in water or a mixed solvent of water and a water-soluble organic solvent. Examples of water-soluble organic solvents that can be used include methanol, ethanol, propanol, acetone, dimethylformamide, acetonitrile, and the like.

  As the polymer electrolyte, a polymer that is ionized in an aqueous solution and has a charged functional group in the main chain or side chain can be used. In this case, a polycation is preferably used. The polycation generally has a positively charged functional group such as polyamines, such as polyethyleneimine (PEI), polyallylamine hydrochloride (PAH), polydiallyldimethylammonium chloride ( PDDA), polyvinyl pyridine (PVP), polylysine, polyacrylamide, and a copolymer containing at least one of them can be used.

  Among polyelectrolytes, polyethyleneimine has a high charge density and a strong binding force. Among these polymer electrolytes, alkali metal (Li, Na, K, Rb, Cs) ions, alkaline earth metal (Ca, Sr, Ba, Ra) ions, halides are used to avoid electromigration and corrosion. Those not containing ions (fluorine ions, chloride ions, bromine ions, iodine ions) are preferred. These polymer electrolytes are all water-soluble or soluble in a mixture of water and an organic solvent, and the molecular weight of the polymer electrolyte cannot be generally determined depending on the type of polymer electrolyte used. However, generally about 500-200,000 is preferable. In general, the concentration of the polymer electrolyte in the solution is preferably about 0.01 to 10% (weight). Further, the pH of the polymer electrolyte solution is not particularly limited.

  By using this polymer electrolyte thin film, the surface of the conductive particles can be uniformly coated without defects, insulation is ensured even when the circuit electrode interval is narrow, and the connection resistance is low and good between the electrically connected electrodes. It becomes. In addition, the coverage of the inorganic oxide can be controlled by adjusting the type, molecular weight, and concentration of the polymer electrolyte thin film.

  When a polyelectrolyte thin film with a high charge density such as polyethyleneimine is used, the coverage of the inorganic oxide tends to be high, and when a polyelectrolyte thin film with a low charge density such as polydiallyldimethylammonium chloride is used, There exists a tendency for the coverage of an inorganic oxide to become low. Further, when the molecular weight of the polymer electrolyte is large, the coverage of the inorganic oxide tends to be high, and when the molecular weight of the polymer electrolyte is small, the coverage of the inorganic oxide tends to be low. When the molecular weight of the polymer electrolyte is large, the inorganic oxide can be strongly adsorbed. From the viewpoint of bonding strength, the molecular weight of the polymer electrolyte is preferably 10,000 or more.

  Further, when the polymer electrolyte is used at a high concentration, the coverage of the inorganic oxide tends to be high, and when the polymer electrolyte is used at a low concentration, the coverage of the inorganic oxide tends to be low.

  When the coverage of the inorganic oxide is high, the insulation tends to be high and the conductivity tends to be poor, and when the coverage of the inorganic oxide is low, the conductivity tends to be high and the insulation is poor.

  In addition, it is good that the inorganic oxide is covered only by one layer. Multi-layer stacking makes it difficult to control the stacking amount.

  The coverage of the inorganic oxide is preferably in the range of 20 to 100%, and more preferably in the range of 30 to 60%.

  After the conductive particles are treated with the insulator particles, the bonding between the insulator particles and the conductor particles can be strengthened by heating and drying. In addition, it is preferable to perform heating in vacuum from the viewpoint of preventing rust of the metal. Reasons for increasing the binding force include, for example, a chemical bond between a functional group such as a carboxyl group on the gold surface and a hydroxyl group on the surface of the insulator particles, and dehydration condensation between a carboxyl group and an amino group on the gold surface. The temperature for heating and drying is preferably 60 ° C to 200 ° C, and the heating time is preferably in the range of 10 to 180 minutes. When the temperature is lower than 60 ° C. or when the heating time is shorter than 10 minutes, the insulator particles are easy to peel off, and when the temperature is higher than 200 ° C. or when the heating time is longer than 180 minutes, the conductive particles are easily deformed, which is preferable. Absent.

  The insulating coated conductive particles produced as described above are dispersed in an adhesive to obtain an anisotropic conductive adhesive.

  For the adhesive used in the anisotropic conductive adhesive of the present invention, a mixture of a heat-reactive resin and a curing agent is used. The adhesive preferably used is a mixture of an epoxy resin and a latent curing agent. Examples of the latent curing agent include imidazole series, hydrazide series, boron trifluoride-amine complex, sulfonium salt, amine imide, polyamine salt, dicyandiamide, and the like. In addition, an energy ray curable resin such as a mixture of a radical reactive resin and an organic peroxide or ultraviolet rays is used for the adhesive.

  The epoxy resin used in the present invention includes a bisphenol type epoxy resin derived from epichlorohydrin and bisphenol A, F, AD, etc., an epoxy novolac resin derived from epichlorohydrin and phenol novolac or cresol novolac, and a skeleton containing a naphthalene ring. It is possible to use various epoxy compounds having two or more glycidyl groups in one molecule such as naphthalene type epoxy resin, glycidylamine, glycidyl ether, biphenyl, alicyclic, etc. Is possible.

For these epoxy resins, it is preferable to use a high-purity product in which impurity ions (Na ⁺ , Cl ^−, etc.), hydrolyzable chlorine and the like are reduced to 300 ppm or less, in order to prevent electromigration.

  In order to reduce the stress after bonding or to improve the adhesiveness, butadiene rubber, acrylic rubber, styrene-butadiene rubber, silicone rubber, or the like can be mixed in the adhesive.

  Further, as the adhesive, a paste or film is used. In order to form a film, it is effective to blend a thermoplastic resin such as a phenoxy resin, a polyester resin, or a polyamide resin. These film-forming polymers are also effective in stress relaxation when the reactive resin is cured. In particular, when the film-forming polymer has a functional group such as a hydroxyl group, the adhesiveness is improved, which is more preferable. For film formation, an adhesive composition comprising at least an epoxy resin, acrylic rubber, and a latent curing agent is liquefied by dissolving or dispersing in an organic solvent, applied onto a peelable substrate, and below the activation temperature of the curing agent. This is done by removing the solvent. The solvent used at this time is preferably an aromatic hydrocarbon-based and oxygen-containing mixed solvent because the solubility of the material is improved.

  The thickness of the anisotropic conductive adhesive is relatively determined in consideration of the particle diameter of the conductive particles and the characteristics of the anisotropic conductive adhesive, but a thickness of 1 to 100 μm is preferable. If it is less than 1 μm, sufficient adhesion cannot be obtained, and if it exceeds 100 μm, a large amount of conductive particles are required to obtain conductivity, which is not realistic. For the same reason, a more preferable thickness is 3 to 50 μm.

  A method for producing a connection structure using the anisotropic conductive adhesive thus produced will be described with reference to FIG.

  FIG. 1A shows an anisotropic conductive adhesive in which insulating coated conductive particles are dispersed in an adhesive 3. The insulating coated conductive particles are composed of conductive particles 2 and insulator particles 1. Next, as shown in FIG.1 (b), the 1st board | substrate 4 and the 2nd board | substrate 6 are prepared, and an anisotropic conductive adhesive is arrange | positioned among them. At this time, the first electrode 5 and the second electrode 7 are opposed to each other. Next, as shown in FIG. 3C, the first substrate 4 and the second substrate 6 are stacked while being heated under pressure. Examples of the substrate include a glass substrate, a tape substrate such as polyimide, a bare chip such as a driver IC, and a rigid package substrate.

  When the connection structure is produced in this way, the insulator particles are peeled off in the vertical direction, the first electrode 5 and the second electrode 7 are conducted, and the insulator particles 1 are interposed between the conductive particles in the horizontal direction. Insulating properties are maintained.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example at all.

(Conductive particles 1)
10 g of crosslinked polystyrene particles having an average particle size of 3.8 μm were added to 100 mL of a palladium-catalyzed solution containing 8% by weight of Atotech Neneogant 834 (manufactured by Atotech Japan Co., Ltd., a trade name), which is a palladium catalyst. After stirring for a minute, it was filtered through a membrane filter of φ3 μm (manufactured by Millipore) and washed with water. Thereafter, the resin fine particles were added to a 0.5 wt% dimethylamine borane solution adjusted to pH 6.0 to obtain resin fine particles whose surface was activated.
Thereafter, resin fine particles whose surface was activated were immersed in distilled water and ultrasonically dispersed. Then, while stirring the suspension at 50 ° C., CUST1610 (manufactured by Hitachi Chemical Co., Ltd.) containing, as main components, formalin as a reducing agent, copper sulfate pentahydrate, sodium hydroxide, and a complexing agent for copper ions. Using a product name), conductive particles having a copper plating thickness of about 500 mm were obtained by a plating solution addition method at 40 ° C.
After washing with water and filtration, the conductive particles were immersed in MCA (made by World Metal Co., Ltd .: trade name) 25 ° C., which is a substituted palladium plating solution, to form a palladium layer of about 200 mm.
Thereafter, conductive particles were immersed in HGS-100 (made by Hitachi Chemical Co., Ltd .: trade name) 85 ° C., which is a displacement gold plating, to form a gold layer of about 200 mm, and conductive particles 1 were produced.

(Conductive particles 2)
Conductive particles 2 were prepared in the same manner as the conductive particles 1 except that the amount of copper plating solution dropped was adjusted and the copper plating thickness was 300 mm.

(Conductive particles 3)
The conductive particles 3 were produced in the same manner as the conductive particles 1 except that the immersion time in the displacement palladium plating was changed and a palladium layer of about 100 mm was formed.

(Conductive particles 4)
Conductive particles 4 were produced in the same manner as the conductive particles 1 except that the outermost layer was not plated with gold.

(Conductive particles 5)
Conductive particles 5 were produced in the same manner as the conductive particles 3 except that the outermost layer was not plated with gold.

(Conductive particles 6)
Apart from forming a palladium layer of about 200 mm by plating addition method at 50 ° C. using APP (Ishihara Pharmaceutical Co., Ltd. product name) which is a reduced electroless palladium plating solution instead of substitutional palladium plating. Produced conductive particles 6 in the same manner as conductive particles 1.

(Conductive particles 7)
Using HSG-2000 (trade name, manufactured by Hitachi Chemical Co., Ltd.), which is a reduction type electroless gold plating, instead of displacement gold plating, a gold layer of about 200 mm was formed by a plating solution addition method at 65 ° C. Except for the above, conductive particles 7 were produced in the same manner as conductive particles 1.

(Conductive particles 8)
Conductive particles 8 were prepared in the same manner as the conductive particles 1 except that crosslinked polystyrene particles having an average particle size of 3.0 μm were used instead of using crosslinked polystyrene particles having an average particle size of 3.8 μm.

(Conductive particles 9)
Conductive particles 9 were produced in the same manner as the conductive particles 1 except that crosslinked polystyrene particles having an average particle diameter of 5.0 μm were used instead of using crosslinked polystyrene particles having an average particle diameter of 3.8 μm.

(Conductive particles 10)
Conductive particles 10 were produced in the same manner as the conductive particles 1 except that palladium plating was not performed.

(Conductive particles 11)
Conductive particles 11 were produced in the same manner as the conductive particles 1 except that the palladium plating thickness was 70 mm.

(Conductive particles 12)
Instead of performing palladium plating, a nickel layer of about 200 mm was formed by plating addition method at 25 ° C. using NIPS-100 (trade name, manufactured by Hitachi Chemical Co., Ltd.) which is electroless nickel plating. Produced conductive particles 12 in the same manner as conductive particles 1.

(Conductive particles 13)
Instead of performing palladium plating, a nickel layer of about 200 mm was formed by plating addition method at 25 ° C. using NIPS-100 (trade name, manufactured by Hitachi Chemical Co., Ltd.) which is electroless nickel plating. Produced conductive particles 13 in the same manner as conductive particles 4.

(Conductive particles 14)
The conductive particles 14 were produced in the same manner as the conductive particles 1 except that the dropping amount of the copper plating solution was adjusted and the copper plating thickness was 200 mm.

(Conductive particles 15)
Bright 22GNR3.8HT (manufactured by Nippon Chemical Industry Co., Ltd .: trade name) in which nickel / gold plating was applied around the resin core particles was used.

  Next, insulating coating particles were produced using the conductive particles 1-14.

(Insulation coated conductive particles 1)
A reaction liquid was prepared by dissolving 8 mmol of mercaptoacetic acid in 200 ml of methanol. Next, 10 g of the conductive particles 1 was added to the reaction solution, and the mixture was stirred at room temperature for 2 hours with a three-one motor and a stirring blade having a diameter of 45 mm. After washing with methanol, the conductive particles were filtered through a membrane filter (manufactured by Millipore) having a diameter of 3 μm to obtain 10 g of conductive particles having a carboxyl group on the surface.
Next, a 30% polyethyleneimine aqueous solution (manufactured by Wako Pure Chemical Industries, Ltd.) having a molecular weight of 70,000 was diluted with ultrapure water to obtain a 0.3 wt% polyethyleneimine aqueous solution. 10 g of the conductive particles having a carboxyl group were added to a 0.3% by weight polyethyleneimine aqueous solution and stirred at room temperature for 15 minutes. Next, the conductive particles were filtered through a membrane filter (manufactured by Millipore) with a diameter of 3 μm, put in 200 g of ultrapure water, and stirred at room temperature for 5 minutes. Further, the conductive particles were filtered with a membrane filter (manufactured by Millipore) having a diameter of 3 μm, and washed with 200 g of ultrapure water on the membrane filter to remove unimsorbed polyethyleneimine.
Next, a colloidal silica dispersion (mass concentration 20%, manufactured by Fuso Chemical Industries, product name Quatron PL-7, average particle size 70 nm) was diluted with ultrapure water to obtain a 0.1 wt% silica solution. The polyethyleneimine-treated conductive particles were placed in a 0.1 wt% silica solution and stirred at room temperature for 15 minutes. Next, the conductive particles were filtered through a membrane filter (manufactured by Millipore) with a diameter of 3 μm, put in 200 g of ultrapure water, and stirred at room temperature for 5 minutes. Furthermore, the conductive particles were filtered with a membrane filter (manufactured by Millipore) having a diameter of 3 μm, and the adsorbed silica was removed by washing twice with 200 g of ultrapure water on the membrane filter. Thereafter, drying was performed under the conditions of 80 ° C. for 30 minutes, and the insulating coated conductive particles 1 were produced by heating and drying at 120 ° C. for 1 hour.

(Insulation coated conductive particles 2)
Insulating coated conductive particles 2 were produced using the conductive particles 2 instead of the conductive particles 1.

(Insulation coated conductive particles 3)
Insulating coated conductive particles 3 were produced using the conductive particles 3 instead of the conductive particles 1.

(Insulation coated conductive particles 4)
Insulating coated conductive particles 4 were produced using the conductive particles 4 instead of the conductive particles 1.

(Insulation coating conductive particles 5)
Insulating coated conductive particles 5 were produced using the conductive particles 5 instead of the conductive particles 1.

(Insulation coated conductive particles 6)
Insulating coated conductive particles 6 were produced using the conductive particles 6 instead of the conductive particles 1.

(Insulation coating conductive particles 7)
Insulating coated conductive particles 7 were produced using the conductive particles 7 instead of the conductive particles 1.

(Insulation coated conductive particles 8)
Insulating coated conductive particles 8 were produced using the conductive particles 8 instead of the conductive particles 1.

(Insulation coated conductive particles 9)
Insulating coated conductive particles 9 were produced using the conductive particles 9 instead of the conductive particles 1.

(Insulation coated conductive particles 10)
Insulating coated conductive particles 10 were produced using the conductive particles 10 instead of the conductive particles 1.

(Insulation coated conductive particles 11)
Insulating coated conductive particles 11 were produced using the conductive particles 11 instead of the conductive particles 1.

(Insulation coated conductive particles 12)
Insulating coated conductive particles 12 were produced using the conductive particles 12 instead of the conductive particles 1.

(Insulation coated conductive particles 13)
Insulating coated conductive particles 13 were produced using the conductive particles 13 instead of the conductive particles 1.

(Insulation coating conductive particles 14)
Insulating coated conductive particles 14 were produced using the conductive particles 14 instead of the conductive particles 1.

(Insulation coating conductive particles 15)
Insulating coated conductive particles 15 were produced using the conductive particles 15 instead of the conductive particles 1.

Example 1
Preparation of adhesive solution: copolymer of 100 g of phenoxy resin (trade name, PKHC, manufactured by Union Carbide) and acrylic rubber (40 parts of butyl acrylate, 30 parts of ethyl acrylate, 30 parts of acrylonitrile, 3 parts of glycidyl methacrylate, molecular weight: 85 10) was dissolved in 300 g of ethyl acetate to obtain a 30 wt% solution.
Next, 300 g of a liquid epoxy (Eboxy equivalent 185, manufactured by Asahi Kasei Epoxy Co., Ltd., NovaCure HX-3941) containing a microcapsule-type latent curing agent was added to this solution and stirred to prepare an adhesive solution.
Ultrasonic dispersion of insulating coating particles: 1, 4 g of insulating coating conductive particles prepared by the method described above were ultrasonically dispersed in 10 g of ethyl acetate. The condition for ultrasonic dispersion was a sample immersed in a beaker in 38 kHZ400W20L (test apparatus: US107 Fujimoto Kagaku brand name) and stirred for 1 minute.
The particle dispersion is dispersed in an adhesive solution (so that the conductive particles are 21% by volume with respect to the adhesive), and this solution is applied to a separator (silicone-treated polyethylene terephthalate film, thickness 40 μm) with a roll coater. The anisotropic conductive adhesive film having a thickness of 25 μm was dried at 90 ° C. for 10 minutes.
Next, using the produced anisotropic conductive adhesive film, a chip (1.7 × 1.7 mm, thickness: 0.7 mm) with gold bumps (area: 30 × 90 μm, space: 10 μm, height: 15 μm, bump number: 362). 5 μm) and a glass substrate with an Al circuit (thickness: 0.7 mm) were connected as shown below.
An anisotropic conductive adhesive film (2 × 19 mm) was attached to a glass substrate with an Al circuit at 80 ° C. and 0.98 MPa (10 kgf / cm 2), then the separator was peeled off, and the bumps of the chip and the position of the glass substrate with the Al circuit Combined.
Next, the main connection was performed by heating and pressing from above the chip under the conditions of 190 ° C., 40 g / bump, and 10 seconds.

(Example 2)
A sample was prepared in the same manner as in Example 1 except that the insulating coated conductive particles 2 were used instead of the insulating coated conductive particles 1.

(Example 3)
A sample was prepared in the same manner as in Example 1 except that the insulating coated conductive particles 3 were used instead of the insulating coated conductive particles 1.

Example 4
A sample was prepared in the same manner as in Example 1 except that the insulating coated conductive particles 4 were used instead of the insulating coated conductive particles 1.

(Example 5)
A sample was prepared in the same manner as in Example 1 except that the insulating coated conductive particles 5 were used instead of the insulating coated conductive particles 1.

(Example 6)
A sample was prepared in the same manner as in Example 1 except that the insulating coated conductive particles 6 were used instead of the insulating coated conductive particles 1.

(Example 7)
A sample was prepared in the same manner as in Example 1 except that the insulating coated conductive particles 7 were used instead of the insulating coated conductive particles 1.

(Example 8)
A sample was prepared in the same manner as in Example 1 except that the insulating coated conductive particles 8 were used instead of the insulating coated conductive particles 1.

Example 9
A sample was prepared in the same manner as in Example 1 except that the conductive particles 1 were used instead of the insulating coating conductive particles 1.

(Example 10)
A sample was prepared in the same manner as in Example 1 except that the insulating coated conductive particles 9 were used instead of the insulating coated conductive particles 1.

(Comparative Example 1)
A sample was prepared in the same manner as in Example 1 except that the insulating coated conductive particles 10 were used instead of the insulating coated conductive particles 1.

(Comparative Example 2)
A sample was prepared in the same manner as in Example 1 except that the insulating coated conductive particles 11 were used instead of the insulating coated conductive particles 1.

(Comparative Example 3)
A sample was prepared in the same manner as in Example 1 except that the insulating coated conductive particles 12 were used instead of the insulating coated conductive particles 1.

(Comparative Example 4)
A sample was prepared in the same manner as in Example 1 except that the insulating coated conductive particles 13 were used instead of the insulating coated conductive particles 1.

(Comparative Example 5)
A sample was prepared in the same manner as in Example 1 except that the conductive particles 10 were used instead of the insulating coating conductive particles 1.

(Comparative Example 6)
A sample was prepared in the same manner as in Example 1 except that the insulating coated conductive particles 14 were used instead of the insulating coated conductive particles 1.

(Comparative Example 7)
A sample was prepared in the same manner as in Example 1 except that the insulating coated conductive particles 15 were used instead of the insulating coated conductive particles 1.

(Measurement of film thickness of gold, copper and palladium)
The thickness of gold, copper, and palladium was measured by dissolving the sample in 50 vol% aqua regia, removing the resin by filtration with a φ3 μm membrane filter (manufactured by Millipore), and measuring the thickness by atomic absorption.

(Ratio of Cu / (Pd + Au) on the surface of conductive particles by XPS)
Conductive particles 1 to 15 were spread on a conductive tape, and the component ratio of the surface of the conductive particles in a circle of Φ1.1 mm was measured by XPS. The number of measured particles was 10,000 or more. The XPS measurement conditions were as shown in Table 1 above. When conducting particles were measured by XPS, components such as carbon and oxygen were detected in addition to copper, gold and palladium. C and O are organic contaminants in the air, so they were ignored and the Cu / (Pd + Au) ratio was determined.

(Confirmation of child particle peeling)
During sample preparation, the insulator particles may be peeled off from the conductive particles when the insulating coated conductive particles are ultrasonically dispersed in ethyl acetate. Then, the child particle coverage before and after ultrasonic dispersion was confirmed by image analysis of SEM. To calculate the coverage, a circle having a diameter half the diameter of the insulating coated conductive particles is drawn on the SEM image, and the coverage of the child particles in the circle (that is, the projected area of the insulating particles × the number of the insulating particles) / Surface area of the insulating coated conductive particles in the measurement range).

(Insulation resistance test and conduction resistance test)
The insulation resistance test and conduction resistance test of the samples produced in the examples and comparative examples were performed. It is important that the anisotropic conductive adhesive film has high insulation resistance between the chip electrodes and low conduction resistance between the chip electrode / glass electrode. The insulation resistance between the chip electrodes was measured for 20 samples, and the minimum value was measured. Further, the yield was calculated when the conduction resistance> 10 ⁹ (Ω) was a non-defective product. Further, the insulation resistance value was measured after being left for 72 hours at 60 ° C. and 90% humidity with a voltage of 20V applied.
Moreover, the average value of 14 samples was measured regarding the conduction | electrical_connection resistance between a chip electrode / glass electrode. The conduction resistance was measured as an initial value and a value after a hygroscopic heat resistance test (left for 1000 hours under conditions of an air temperature of 85 ° C. and a humidity of 85%).

  Details of the samples prepared in Examples and Comparative Examples are shown in Table 2, and the results of the above measurements and tests are shown in Table 3, respectively. As shown in Table 3, it was found that the samples produced according to Examples 1 to 10 were superior in conduction resistance as compared with the conventional nickel / gold plating (Comparative Example 7). This is because copper is more conductive than conventional nickel. It was found that when the copper thickness was less than 300 mm (Comparative Example 6), the average conduction resistance after the moisture absorption test was 5Ω or more. Therefore, it can be said that the copper plating thickness is preferably 300 mm or more. Moreover, when Pd which is a copper migration stop layer was not used, both the conductive particles (comparison of Example 9 and Comparative Example 5) and the insulating coated conductive particles (comparison of Example 1 and Comparative Example 1) were both insulated by moisture absorption. Decreases. Therefore, when copper is used, reliability is improved by having a palladium layer as a migration stop layer. In addition, when nickel is used as the migration stop layer as in the prior art, the small particle coverage is reduced depending on the presence or absence of gold, and the insulation is reduced (Comparative Example 3 and Comparative Example 4). Further, when the palladium layer is thick, the effect of preventing migration is large (comparison between Example 1, Example 3 and Comparative Example 2). From a practical aspect, a thickness of 100 mm or more is sufficient. When the diameters of the conductive particles are compared (comparison between Example 1, Example 8 and Example 10), the conductive particle diameter is preferably 4 μm or less. Further, compared to displacement plating, reduced electroless palladium plating (comparison between Example 1 and Example 6) and reduced electroless gold plating (comparison between Example 1 and Example 7) are Cu / (Pd + Au). The ratio is small, and the rate of decrease in insulation resistance is small, which is more preferable. It is more preferable that gold plating is present because the rate of decrease in insulation resistance is small (comparison between Example 1 and Example 4, comparison between Example 3 and Example 5).

1: Polymer electrolyte 2: Conductive particles 3: Adhesive 4: First substrate 5: First electrode 6: Second substrate 7: Second electrode

Claims (9)

Resin particles and a metal layer provided on the surface of the resin particles,
The metal layer has a structure in which a first layer containing copper or a copper alloy and a second layer containing palladium are stacked in the order closer to the resin particles,
Conductive particles, wherein the copper / (gold + palladium) ratio in the metal layer is 0.4 or less by weight . The conductive particles according to claim 1 , wherein the second layer is a reduction plating type palladium layer. The conductive particles according to claim 1 or 2 , wherein the thickness of the first layer is 300 mm or more. Conductive particles according to any one of claims 1 to 3, wherein the thickness of said second layer is 100Å or more. The conductive particles according to claim 1, wherein the conductive particles have an average particle size of 2 to 4 μm. Insulation-coated conductive particles, wherein at least a part of the surface of the metal layer of the conductive particles according to any one of claims 1 to 5 is coated with insulator particles. At least a portion is coated with a polymer electrolyte, the surface of the metal layer coated with the polymer electrolyte is insulative child of the metal layer surface of the conductive particles according to any one of claims 1 to 5 Insulated coated conductive particles, further coated with particles. An anisotropic conductive adhesive obtained by dispersing the conductive particles according to any one of claims 1 to 5 in an adhesive. Anisotropic conductive adhesive having dispersed in an adhesive insulating coating conductive particle according to claim 6 or 7.

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