JP2006104273A - Electroconductive adhesive and electroconductive film, and printed wiring board obtained using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly reliable electroconductive adhesive as an adhesive material for replacing solder which is endowed with a low resistance property and a low migration property and yet can be microfabricated, and its joining method. <P>SOLUTION: The electroconductive adhesive comprises an anisotropic ferromagnetic metal plated with a noble metal and having a particle size of 0.5-5 μm, and the electroconductive particles are oriented by thermosetting the insulating adhesive resin in a magnetic field. The electroconductive adhesive has such a constitution and thus permits a highly reliable electroconductive connection having a large electric capacity and an excellent antioxidation property. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a conductive adhesive as a substitute for solder, and to a method for connecting an electronic component having a plurality of conductive terminals to a substrate surface having a plurality of conductive paths using the conductive adhesive.

Sn / Pb solder is generally used as a bonding technique on a printed circuit board. However, Pb-free is being promoted due to environmental problems. A bonding method that is attracting attention along with Pb-free solder is a conductive adhesive. For this conductive adhesive, development of a low-cost material that satisfies a decrease in connection resistance, a countermeasure against migration, and an improvement in adhesive strength is required, and several proposals have been made heretofore.

A conductive resin with low content and good electrical conductivity, which is reliably bonded with metal bundles by magnetic force, can be manufactured with a simple component structure with high reliability and high yield, and has excellent durability. It is for the purpose of provision. In order to achieve the object, an adhesive formed by pressure-pulverizing a magnetized magnet to form conductive particles of 100 μm to 0.1 μm and mixed with an ultraviolet curable adhesive is described in the patent literature. ing.

According to Patent Document 1, since the magnetized magnetic material is used as conductive particles, there is a problem in that the resistance value increases due to surface oxidation or the like.

In addition, Patent Document 2 describes an adhesive in which a ferromagnetic material having a highly conductive plating layer as a surface layer is dispersed and filled by using a magnetic field in an uncured adhesive.

According to Patent Document 2, since the particle diameter is as large as 20 to 30 μm, the conductive particles are likely to settle in the coating liquid, and there is a problem that handling may be difficult during screen printing.

Patent Document 3 provides a conductive powder and paste that are excellent in environmental resistance, conductive, easily deformable, and excellent in bondability when directly mounting an LSI chip on a substrate. And it is represented by the general formula Ag _x Cu _1-x (where 0.02 ≦ x ≦ 0.4, atomic ratio), and the silver concentration on the particle surface is 2.3 times or more of the average silver concentration, Conductive powder having an average particle diameter of 3 to 20 μm and an average particle diameter of ± 2 μm of 75% or more and containing oxygen concentration of 2000 ppm or less or paste using the conductive powder of the composition is applied to the substrate electrode of the LSI chip electrode. It is described that it is used for connection.

When mounting this LSI chip on a substrate, the present invention provides a conductive powder and a paste using the conductive powder that are easily deformed and excellent in migration resistance as well as conductivity and environmental resistance.

According to the above-mentioned Patent Document 3, the silver and copper gradient conductive powder is excellent in conductivity and migration resistance, but it causes a cost increase in the powder manufacturing method and has a spherical shape, and therefore has a connection resistance as a conductive adhesive. There is a problem that cannot be lowered.

Further, Patent Document 4 provides a conductive resistor using a metal that is easily available and does not cause pollution, does not cause migration, and has little resistance change even when left at high temperature, and a circuit using the same. Is to do. For this purpose, metal particles whose surface is nickel or a nickel-boron alloy, conductive particles surface-treated with a mixture of a polyoxyalkylene phosphate derivative and a polyoxyalkylene alkyl (or alkenyl) amine or a derivative thereof, and diglycidyl There is a description of an adhesive containing an epoxy resin containing a type reactive diluent and a phenol resin containing an alkylresole type or an alkyl novolak type.

According to Patent Document 4, since the surface uses nickel or nickel alloy metal particles, there is a problem that the resistance value increases due to surface oxidation or the like.

Patent document 5 is a conductive adhesive containing two or more types of metal powders having different shapes, and there is a description of a conductive adhesive in which the outermost surface plating of only one selected metal powder is performed. .

In Patent Document 5, as in Patent Document 2, since the maximum size of the metal powder is as large as 40 μm, sedimentation or the like is likely to occur in the coating liquid, which may be difficult to handle during screen printing. The problem is that irregularities may occur on the printed surface.

Patent Document 6 describes a conductive film containing acicular gamma-iron oxide as conductive particles, wherein each particle acts as a single conductive circuit by applying a magnetic field. Has been.

In Patent Document 6, since each conductive particle is single and secures conduction, it is necessary to make the particle diameter of the conductive particles uniform in order to stabilize electrical characteristics. For this reason, there is a problem that it is too costly to use as a solder substitute material.

Japanese Patent Laid-Open No. 5-114307 JP-A-6-122857 JP-A-6-260015 JP-A-9-157613 JP 2002-332464 A Japanese Patent Laid-Open No. 2003-187885

As described above, conventional conductive adhesives have problems of reliability in fine circuits, problems of increased connection resistance due to oxidation of the surface of the conductive particles, and conductive particles settled due to the large particle size and screen printability. There were problems such as a decrease in manufacturing cost and a problem of manufacturing costs.

The present invention provides a new solder replacement material that solves these problems. As a solder substitute material, a conductive adhesive having low resistance and high reliability in the connection of electronic components having fine circuits, and having excellent screen printability, and conductive using this conductive adhesive It aims at providing a property film and a printed wiring board.

The conductive adhesive of the present invention includes a matrix resin and conductive particles, the conductive particles have an average particle size of 0.5 to 5 μm, and the conductive particles have a noble metal plated surface. When the electronic components are bonded, a magnetic field can be applied in the vertical direction to ensure efficient conduction.

In the conductive adhesive comprising a matrix resin and conductive particles, the conductive particles are plated with a noble metal on the surface, and have an anisotropic shape with an average particle diameter of 0.5 to 5 μm. The conductive adhesive comprises 10 to 50 wt% of the conductive particles with respect to the total weight part of the conductive adhesive.

The invention according to claim 2 is the conductive adhesive according to claim 1, wherein the conductive particles having anisotropy have an aspect ratio of 2 or more.

Invention of Claim 3 is the microcapsule structure in which the conductive adhesive in the conductive adhesive of Claim 1 or Claim 2 was coated with the heat-resinable resin in the matrix resin,
A conductive adhesive comprising a curing agent having an average particle size of 0.1 to 0.9 times the average particle size of the conductive particles.

The invention according to claim 4 is a conductive film characterized in that a conductive back adhesive comprising the conductive adhesive according to any one of claims 1 to 3 is formed on a carrier film. .

A fifth aspect of the present invention is a printed wiring board in which an electronic component is electrically connected using the conductive adhesive according to any one of the first to third aspects.

The invention described in claim 6 is characterized in that the conductive particles contained in the conductive adhesive are oriented in a direction perpendicular to the connection surface by a magnetic field. It is a printed wiring board.

A seventh aspect of the present invention is a printed wiring board in which an electronic component is electrically connected using the conductive adhesive layer of the conductive film according to the fourth aspect.

The invention described in claim 8 is characterized in that the conductive particles contained in the conductive adhesive are oriented in a direction perpendicular to the connection surface by a magnetic field. It is a printed wiring board.

In the conductive adhesive of the present invention, since the average particle diameter of the conductive particles contained in the conductive adhesive is sufficiently small, the conductive particles do not settle in the coating liquid. Furthermore, when the conductive particles have an anisotropic shape, the bulk density of the conductive particles is improved, and the fluidity of the conductive adhesive is improved.

The conductive adhesive of the present invention uses a microcapsule structure as the curing agent contained in the matrix resin, and the average particle diameter of the curing agent particles corresponds to the average particle diameter of the conductive particles. The dispersibility of the conductive particles can be improved. Due to the effects of fluidity and dispersibility, the conductive adhesive of the present invention can achieve a significant improvement in screen printability as compared with conventional conductive adhesives.

The conductive adhesive of the present invention is characterized in that the conductive particles have a ferromagnetic metal as a nucleus and an anisotropic shape. This facilitates orientation by a magnetic field, and enables highly reliable connection even when connecting electronic components having efficient and fine circuits.

The conductive adhesive of the present invention is further characterized in that noble metal plating is further performed on the ferromagnetic metal nuclei of the conductive particles. Thereby, the oxidation of the ferromagnetic metal nucleus of the conductive particles can be prevented, and the increase of the resistance value of the conductive adhesive can be prevented. Due to these effects, the conductive adhesive of the present invention can obtain electrical characteristics sufficient for use as a solder substitute material. As described above, the conductive adhesive of the present invention overcomes the problems of conventional conductive adhesives and has sufficient connectivity and reliability as a solder substitute material. It is also excellent in workability, such as being suitable for screen printing.

A method of connecting an electronic component having a conductive terminal to the substrate surface using the conductive adhesive of the present invention will be described with reference to the drawings. First, a conductive adhesive containing the conductive particles according to claim 1 and claim 2 and the matrix resin according to claim 3 is prepared. The conductive adhesive or the conductive adhesive processed into a film shape is pressure-bonded between a printed wiring board (hereinafter referred to as PCB) and an electronic component such as a semiconductor package, and arranged as shown in FIG. .

Next, when a magnetic field is applied to the unbonded electronic member in the vertical direction, the conductive particles in the conductive adhesive are oriented vertically along the magnetic field as shown in FIG. 2, and conduction between the electronic members is ensured. The Furthermore, by heating the unbonded electronic member in a state where a magnetic field is applied or in a state where orientation is maintained after applying a magnetic field, a curing agent is released from the microcapsule-type curing agent in the conductive adhesive, The matrix resin is cured as shown in FIG.

In the conductive adhesive containing the matrix resin and the conductive particles of the present invention, the average particle size of the conductive particles is 0.5 to 5 μm. The average particle diameter is the average of the longest diameters among the length components of the conductive particles. When the average particle diameter of the conductive particles is less than 0.5 μm, the conductive particles are not absorbed by the irregularities on the surface of the electronic component, and a sufficient connection cannot be secured through the conductive particles. In addition, when it exceeds 5 μm, it is difficult to obtain a sharp particle size distribution, and there is a high probability that a large particle size is mixed, resulting in poor insulation between adjacent terminals and poor connection due to large particles. It may happen. In addition, sedimentation or the like may occur in the coating liquid that causes a decrease in screen printability. The average particle diameter is preferably in the range of 1 to 2 μm. A sharp particle size distribution is preferred.

As for the compounding quantity of the said electroconductive particle with respect to a conductive adhesive, it is desirable that it is 10-50 wt% with respect to the whole weight part of this conductive adhesive. If the blending amount does not reach 10 wt%, the connection area is reduced and the connection reliability is lowered. Conversely, if the blending amount exceeds 50 wt%, the insulation between adjacent terminals is lowered and short circuit occurs. Connected.

Regarding the shape of the conductive particles, anisotropic particles such as flakes, needles, and scales are used. Since the bulk density can be increased by using anisotropic particles, the fluidity of the coating liquid is improved. When the fluidity is improved, the conductive adhesive remains at the opening of the metal mask in screen printing, and the frequency of cleaning the metal mask can be reduced. This improves the workability and productivity during the process.

Further, since the conductive particles are anisotropic particles, orientation by a magnetic field is facilitated. It is considered that the greater the anisotropy, the better the orientation of the conductive particles by the magnetic field. For this reason, the larger the anisotropy of the conductive particles is, the more preferable, and specifically, the aspect ratio of the conductive particles is more preferably 2 or more.

The conductive particles have a ferromagnetic material as a nucleus in order to enable orientation by a magnetic field. Specifically, a ferromagnetic material made of Fe, Ni, Co or an alloy thereof is used. Then, by plating the surface with a noble metal such as Au or Ag, the surface oxidation of the conductive particles can be prevented and the connection resistance can be reduced. At this time, the cost can be reduced by performing the electroless plating.

After the conductive adhesive using the conductive particles is supplied onto the PCB electrode, an electric component is mounted and heated and bonded while applying a magnetic field in the vertical direction. Thereby, it is possible to maintain the bonding while maintaining the orientation of the conductive particles. Further, after supplying a conductive adhesive using the conductive particles onto the PCB electrode and applying a magnetic field in the vertical direction, it is possible to perform heat bonding while maintaining the orientation.

As the matrix resin used in the present invention, a thermosetting resin insulating layer resin is used. At this time, a microcapsule type coated with a thermoplastic resin may be used as the curing agent. The average diameter of the microcapsules is 0.1 to 0.9 times the average particle diameter of the conductive particles. Preferably, those having an average particle size of 0.5 to 0.7 times the average particle size of the conductive particles are used. Thereby, the dispersibility of electroconductive particle and the fluidity | liquidity at the time of adhesion | attachment can be improved, and screen printability can be improved.

Specific examples of the matrix resin used in the present invention include thermosetting resins such as epoxy resins, polyimide resins, polyurethane resins, urea resins, and phenol resins. Among these, an epoxy resin is most preferably used.

As the epoxy resin, any of an alicyclic type, a bifunctional type glycidyl ether type, a polyfunctional type glycidyl ether type, a glycidyl ester type, and a glycidyl amine type can be used.

Examples of the alicyclic epoxy resin include an alicyclic diepoxy acetal type, an alicyclic diepoxy adipate type, an alicyclic diepoxycarboxylate type, a vinylcyclohexene dioxide type, and a vinyl tricyclodecene type.

Examples of the bifunctional glycidyl ether type epoxy resin include bisphenol A type, brominated bisphenol A type, hydrogenated bisphenol A type, bisphenol F type, bisphenol S type, bisphenol AF type, biphenyl type, naphthalene type, fluorene type, etc. Is mentioned.

Examples of the polyfunctional type glycidyl ether type epoxy resin include a phenol novolak type, an orthocresone novolak type, a DPP novolak type, a tris-hydroxyphenylmethane type, and a tetraphenylolethane type.

Examples of the glycidyl ester type epoxy resin include those produced by condensation of carboxylic acids such as phthalic acid derivatives and synthetic fatty acids with epichlorohydrin (ECH).

Examples of the glycidylamine type epoxy resin include tetraglycidyldiaminodiphenylmethane (TGDDM), triglycidyl diisocyanate (TGIC), hydantoin type, 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane (TETRAD-D), amino Examples include phenol type, aniline type, and toluidine type.

The illustrated epoxy resins may be used alone or in combination of two or more, but those of the bisphenol F type are particularly preferably used.

Examples of the curing agent used in the present invention include an acid anhydride curing agent, an amine curing agent, and an imidazole curing agent. The addition amount of the curing agent should be appropriately set in consideration of various factors such as the kind of the curing agent to be used, the curing speed to be achieved, or the pot life of the adhesive, but 100 parts by weight of the thermosetting resin. The amount is preferably in the range of 50 to 200 parts by weight.

Acid anhydride curing agents include phthalic anhydride, maleic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, methylhexahydrophthalic anhydride, hymic anhydride, tetrabromophthalic anhydride, Examples include merit acid, pyromellitic anhydride, benzophenone tetracarboxylic acid anhydride, and the like.

Examples of the amine curing agent include diethylenetriamine, triethylenetetramine, mensendiamine, isophoronediamine, metaxylenediamine, diaminodiphenylmethane, metaphenylenediamine, and diaminodiphenylsulfone.

Examples of imidazole curing agents include 2-phenyl-4-methylimidazole, 2-undecylimidazole, 2,4-diamino-6- [2-methylimidazole- (1)]-ethyl-S-triazine, 1-cyanoethyl. Examples include 2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole and the like.

The thermoplastic resin for coating the imidazole curing agent is appropriately selected in consideration of the relationship with the main agent and the type of curing agent (temperature at which the reaction is activated). In the present invention, a thermoplastic resin having a melting point in the range of 50 to 200 ° C. is preferably used. Examples of such a thermoplastic resin include polyethylene, polypropylene, polystyrene, polycarbonate, acrylic resin, acrylonitrile styrene resin, and acrylonitrile butadiene styrene. Examples thereof include resins and polyoxymethylene.

Examples of the curing accelerator used in the present invention include organic phosphines, imidazoles, diazabicycloundecene, diazabicycloundecene toluenesulfonate, diazabicycloundecene octylate and the like. These may be used alone or in combination as a curing accelerator. The addition amount of the curing accelerator should be appropriately set in consideration of the type and addition amount of the curing agent to be used, the curing speed to be achieved, and preferably 1 to 100 parts by weight of the thermosetting resin. The range is 50 parts by weight.

Examples of organic phosphines include triphenylphosphine, trimetatolylphosphine, tetraphenylphosphonium tetraphenylborate, triphenylphosphine triphenylborane, and the like.

As imidazoles, those listed above as curing agents can be used. When using imidazoles, a modified imidazole compound is preferably used. Examples of the modified imidazole compound include 2-ethyl-4-methylimidazole, 2-phenimidazole, 2-phen-4-methylimidazole, 1-benzyl-2-phenylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-methylimidazole, In imidazole compounds such as cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, and 1-methyl-2-ethylimidazole, H in the imino group (—NH—) is an alkyl having an epoxy ring. It shall be substituted by an atomic group such as a group.

The method for producing the conductive adhesive of the present invention does not specifically limit the order of addition of materials. Generally, a solid one of the adhesive resin components is dissolved in a solvent in advance, and after adding this and a liquid resin component, further additives, etc., the conductive particles are mixed and the resin is uniformly mixed. What is necessary is just to disperse | distribute in. When additives are added to the conductive adhesive or ultrasonic treatment is performed to improve dispersibility, aggregation of the conductive particles hardly occurs.

The method for connecting electronic components using the conductive adhesive of the present invention is not particularly limited. For example, the conductive adhesive is applied or printed on the surface of the substrate on which the electronic component is to be attached, and the electrodes of the electronic component are vertically aligned and bonded onto a previously selected conductive path. Alternatively, instead of directly applying the conductive adhesive, it is also possible to bond the substrate and the electronic component using a film coated with the conductive adhesive. At the time of bonding, the conductive particles may be collected at the bonding portion of the conductive adhesive between the conductive terminal and the conductive path, and the conductive adhesive may be cured in the presence of a magnetic field.

The strength of the applied magnetic field is preferably in the range of 100 to 6000 gauss, and more preferably in the range of 300 to 2000 gauss. Below 100 gauss, the conductive particles do not collect between the conductive terminal and the conductive path, and above 6000 gauss, the conductive particles receive too much force in the direction of the applied magnetic field, and the electrical connection is unstable in both cases. Therefore, there is a risk of lack of reliability.

It is also possible to form a dry film by casting and drying the conductive adhesive of the present invention on a carrier film whose surface has been subjected to a release treatment. In that case, since the fluidity of the conductive particles is lowered, the applied magnetic field requires a higher magnetic field than the case of bonding using a conductive adhesive as in the previous section. Specifically, a range of 500 to 8000 gauss is desirable.

<Example 1>
As a matrix resin contained in the conductive adhesive in the present invention, epoxy resin (Epicoat 1001, manufactured by Yuka Shell Epoxy Co., Ltd.) / Polyvinyl butyral resin (ESREC BM-S, manufactured by Sekisui Chemical Co., Ltd.) = 1: 1. A matrix resin is prepared by mixing 200 parts by weight of a 25% solution dissolved in a mixed solvent of toluene / ethyl acetate = 1: 1 and 100 parts by weight of an imidazole microcapsule type curing agent (Novacure, manufactured by Asahi Kasei Co., Ltd.).

In this, the electroconductive adhesive which disperse | distributed 20 wt% of electroconductive particles with an average particle diameter of 2 micrometers and an average aspect ratio of 2 which performed electroless gold plating on the surface of nickel particles was obtained. At this time, the average particle size of the microcapsule-type curing agent should not be larger than the average particle size of the conductive particles, more preferably the average particle size of the microcapsule-type curing agent is the average particle size of the conductive particles. The diameter is in the range of 0.1 to 0.9 times.

A PCB having a conductive adhesive layer having a thickness of about 50 μm is applied by applying this conductive adhesive to a terminal portion to which a PCB having a circuit width of 0.1 mm, a circuit pitch of 0.2 mm, and 60 terminals is connected by screen printing. Got.

After that, this PCB is set in a crimping press so that the terminals of a tape carrier package (hereinafter referred to as TCP) having a circuit width of 0.1 mm, a circuit pitch of 0.2 mm, and 60 terminals are aligned with the circuit terminals of the PCB. They were put together and placed on the PCB, and pressure-bonding was performed by heating and pressing under the conditions of 175 ° C., 30 kg / cm ² and 15 sec. A magnetic field having a magnetic flux density of 1000 gauss was applied to the PCB in the vertical direction during the crimping connection by heating and pressing. The PCB used here is a substrate having an inner layer / outer layer copper foil of 18 μm, and the surface after circuit processing is nickel / gold plated. Further, TCP is made of a 75 μm polyimide base material and a 25 μm copper foil, and the surface after circuit processing is Sn-plated.

As a result of measuring the serial connection resistance value of 60 terminals on the PCB side of this connection body (measurement current 1 μA), it was good at 2Ω or less. The insulation resistance between adjacent terminals was also as good as 10 ¹⁰ Ω or more (measurement voltage 100 v, 30 sec). In addition, this sample was put into a HH (high temperature and high humidity treatment) test apparatus (85 ° C., 85% RH), and as a result of observing changes in connection resistance value and insulation resistance value, the connection resistance was 3Ω or less even after 1000 hours of treatment. The insulation resistance value was 10 ¹⁰ Ω or more, and good connectivity was obtained. When the voltage was measured while increasing the applied current and the current value at the point where the voltage-current characteristic deviated from the straight line was defined as the current capacity, the current capacity was 1000 mA / mm ² and was sufficiently large. The results are shown in Table 1.

<Example 2>
As a matrix resin contained in the conductive adhesive in the present invention, epoxy resin (Epicoat 1001, manufactured by Yuka Shell Epoxy Co., Ltd.) / Polyvinyl butyral resin (ESREC BM-S, manufactured by Sekisui Chemical Co., Ltd.) = 1: 1. A matrix resin is prepared by mixing 200 parts by weight of a 25% solution dissolved in a mixed solvent of toluene / ethyl acetate = 1: 1 and 100 parts by weight of an imidazole microcapsule type curing agent (Novacure, manufactured by Asahi Kasei Co., Ltd.). In this, the electroconductive gold-plating which carried out electroless gold plating on the surface of nickel particle | grains and disperse | distributed 20 wt% of particles with an average particle diameter of 2 micrometers and an average aspect ratio of 2 was obtained. At this time, the average particle size of the conductive particles should not be larger than the average particle size of the microcapsule-type curing agent, more preferably the average particle size of the microcapsule-type curing agent is the average particle size of the conductive particles. The diameter is in the range of 0.1 to 0.9 times.

The conductive adhesive is applied by screen printing, dried onto a polyethylene terephthalate carrier film, dried and applied to a conductive adhesive layer having a thickness of about 50 μm, and then slit into a 2 mm width to conduct electricity. A conductive film was prepared. When the appearance of this film was observed, the conductive particles were uniformly dispersed.

This conductive film is placed on a terminal portion to which a PCB having a circuit width of 0.1 mm, a circuit pitch of 0.2 mm, and 60 terminals is connected, and is heated and pressed under conditions of 70 ° C., 5 kg / cm ² , and 2 seconds to perform temporary pressure bonding. went. Thereafter, the carrier film on the surface is peeled off, set in a pressure press, and the terminals of the tape carrier package having a circuit width of 0.1 mm, a circuit pitch of 0.2 mm, and 60 terminals are aligned with the circuit terminals of the PCB. The product was placed on a PCB and heated and pressed under the conditions of 175 ° C., 30 kg / cm ² , and 15 sec to make a crimp connection. This cross-sectional shape is schematically shown in FIG. Magnetic fields having a magnetic flux density of 800 gauss and 1000 gauss were applied to the PCB in the vertical direction during the temporary pressure bonding and the pressure bonding by heating and pressing, respectively. Then, as shown in FIG. 2, the conductive particles of the conductive adhesive layer are aligned along the magnetic field. The microcapsules are collapsed by heating, and the matrix resin is cured by the curing agent. Then, a connection state as shown in FIG. 3 is obtained. The PCB used here is a substrate having an inner layer / outer layer copper foil of 18 μm, and the surface after circuit processing is nickel / gold plated. Further, TCP is made of a 75 μm polyimide base material and a 25 μm copper foil, and the surface after circuit processing is Sn-plated.

As a result of measuring the serial connection resistance value of 60 terminals on the PCB side of this connection body (measurement current 1 μA), it was good at 2Ω or less. The insulation resistance between adjacent terminals was also as good as 10 ¹⁰ Ω or more (measurement voltage 100 v, 30 sec). In addition, this sample was put into a HH (high temperature and high humidity treatment) test apparatus (85 ° C., 85% RH), and as a result of observing changes in connection resistance value and insulation resistance value, the connection resistance was 3Ω or less even after 1000 hours of treatment. In addition, the insulation resistance value was 10 ¹⁰ Ω or more, and good connectivity was obtained. When the voltage was measured while increasing the applied current and the current value at the point where the voltage-current characteristic deviated from the straight line was defined as the current capacity, the current capacity was 1000 mA / mm ² and was sufficiently large. The results are shown in Table 1.

<Example 3>
Example 2 and a matrix resin were prepared, and 40 wt% of conductive particles subjected to the same treatment as in Example 1 were dispersed therein to produce a conductive film having a conductive adhesive layer thickness of 50 μm. When the appearance of this film was observed, the conductive particles were uniformly dispersed.

A sample of this conductive film was prepared and evaluated in the same manner as in Example 1. The connection resistance value was 2Ω or less, and the insulation resistance between adjacent terminals was 10 ¹⁰ Ω or more. In addition, the connection resistance value after HH treatment was 3Ω or less, and the insulation resistance value was 10 ¹⁰ Ω or more. The current capacity was 1200 mA / mm ² and was sufficiently large. The results are shown in Table 1.

<Example 4>
The same matrix resin as in Example 2 was prepared, and in this, particles having an average particle diameter of 5 μm and an average aspect ratio of 3 with gold plating on the surface of nickel particles were dispersed in an amount of 20 wt%, and the thickness of the conductive adhesive layer A conductive film having a thickness of 50 μm was produced. When the appearance of this film was observed, the conductive particles were uniformly dispersed.

A sample of this conductive film was prepared and evaluated in the same manner as in Example 1. However, here, the pressure connection was performed by heating and pressing under conditions of 150 ° C., 30 kg / cm ² , 15 sec, and magnetic flux density of 600 gauss. The connection resistance value was 2Ω or less, and the insulation resistance between adjacent terminals was 10 ¹⁰ Ω or more. In addition, the connection resistance value after HH treatment was 3Ω or less, and the insulation resistance value was 10 ¹⁰ Ω or more. The current capacity was 1300 mA / mm @ 2, which was sufficiently large. The results are shown in Table 1.

<Example 5>
The same matrix resin as in Example 2 was prepared, and in this, 20 wt% of particles having an average particle diameter of 2 μm and an average aspect ratio of 2 with gold plating applied to the surface of the cobalt particles were dispersed, and the thickness of the conductive adhesive layer A conductive film having a thickness of 50 μm was produced. When the appearance of this film was observed, the conductive particles were uniformly dispersed.

A sample of this conductive film was prepared and evaluated in the same manner as in Example 1. The connection resistance value was 2Ω or less, and the insulation resistance between adjacent terminals was 10 ⁹ Ω or more. Further, the connection resistance value after HH treatment was 3Ω or less, and the insulation resistance value was 10 ⁹ Ω or more. The current capacity was 1200 mA / mm @ 2, which was sufficiently large. The results are shown in Table 1.

<Example 6>
The same matrix resin as in Example 1 was prepared, and the surface of the nickel particles was plated with gold, and the particles having an average particle diameter of 2 μm and an average aspect ratio of 2 were dispersed by 10 wt%, and the thickness of the conductive adhesive layer A conductive film having a thickness of 50 μm was produced. When the appearance of this film was observed, the conductive particles were uniformly dispersed.

A sample of this conductive film was prepared and evaluated in the same manner as in Example 1. The connection resistance value was 3Ω or less, and the insulation resistance between adjacent terminals was 10 ¹⁰ Ω or more. In addition, the connection resistance value after HH treatment was 3Ω or less, and the insulation resistance value was 10 ¹⁰ Ω or more. The current capacity was 1000 mA / mm @ 2 and was sufficiently large. The results are shown in Table 1.

<Example 7>
The same matrix resin as in Example 2 was prepared, in which 50% by weight of particles having an average particle diameter of 2 μm and an average aspect ratio of 2 with gold plating applied to the surface of nickel particles was dispersed, and the thickness of the conductive adhesive layer A conductive film having a thickness of 50 μm was produced. When the appearance of this film was observed, the conductive particles were uniformly dispersed.

A sample of this conductive film was prepared and evaluated in the same manner as in Example 1. The connection resistance value was 2Ω or less, and the insulation resistance between adjacent terminals was 10 ⁹ Ω or more. Moreover, the connection resistance value after the HH treatment was 3Ω or less, and the insulation resistance value was 10 ⁹ Ω or more. The current capacity was 1100 mA / mm @ 2, which was sufficiently large. The results are shown in Table 1.

<Comparative Example 1>
As the conductive particles, the same conductive film as in Example 2 was prepared except that 20 wt% of particles having an average particle diameter of 10 μm and an average aspect ratio of 2 were plated on the surfaces of nickel particles. When the appearance of this film was observed, large conductive particles having a diameter of 10 μm or more were mixed, and many aggregates of particles were observed.

A sample of this conductive film was prepared and evaluated in the same manner as in Example 1. Many samples with a connection resistance of 3Ω or more were observed. In addition, many samples with an insulation resistance between adjacent terminals of 10 ⁶ Ω or less were observed due to aggregation. Further, the connection resistance value after the HH treatment also increased to 5Ω or more, and the number of samples having an insulation resistance value of 10 ⁶ Ω or less increased, and it was confirmed that the connection was unstable. Further, the current capacity was 200 mA / mm ² and was quite small. The results are shown in Table 1.

<Comparative Example 2>
As the conductive particles, the same conductive film as in Example 1 was produced except that 60 wt% of particles having an average particle diameter of 2 μm and an average aspect ratio of 2 were plated on the surface of nickel particles. When the appearance of this film was observed, a number of aggregates of particles were observed.

A sample of this conductive film was prepared and evaluated in the same manner as in Example 1. Because of the large amount of particles, many samples with an insulation resistance between adjacent terminals of 10 ⁶ Ω or less were observed. The connection resistance value was as good as 2Ω or less. Although the connection resistance value after the HH treatment remained as good as 3Ω or less, samples with an insulation resistance value of 10 ⁶ Ω or less increased. The current capacity was 1100 mA / mm @ 2, which was sufficiently large. The results are shown in Table 1.

<Comparative Example 3>
As the conductive particles, the same conductive film as that of Example 1 was prepared except that 3 wt% of particles having an average particle diameter of 1 μm and an average aspect ratio of 1.1 were plated on the surface of nickel particles. When the appearance of this film was observed, the connection between the particles was unstable.

A sample of this conductive film was prepared and evaluated in the same manner as in Example 1. Due to the unstable connection, some samples with a connection resistance value of 5Ω or more were found. Moreover, the insulation resistance between adjacent terminals was 10 ¹⁰ Ω or more due to large particles. Further, the insulation resistance value after HH treatment remained at 10 ¹⁰ Ω or more, but the connection resistance value increased to 7 Ω or more. Also, the current capacity was 1100 mA / mm @ 2, which was sufficiently large. The results are shown in Table 1.

A summary of the results of <Example> and <Comparative Example> is shown in Table 1.

FIG. 1 is a schematic cross-sectional view after bonding PCB and TCP with the conductive adhesive of the present invention. FIG. 2 is a schematic cross-sectional view in a state where PCB and TCP are bonded with the conductive adhesive of the present invention and a magnetic field is applied. FIG. 3 is a schematic cross-sectional view in a state where PCB and TCP are bonded with the conductive adhesive of the present invention, a magnetic field is applied, and further bonded with a thermosetting resin.

Explanation of symbols

1 Printed wiring board (PCB)
2 Conductive particles 3 Microcapsule curing agent 4 Matrix resin 5 Tape carrier package (TCP)
6 Resin after curing

Claims (8)

In a conductive adhesive containing matrix resin and conductive particles,
The conductive particles are particles having an average particle diameter of 0.5 to 5 μm with a noble metal plating on the surface, and the conductive particles are 10 parts by weight with respect to the total weight part of the conductive adhesive. A conductive adhesive characterized by containing ˜50 wt%. The conductive adhesive according to claim 1, wherein an aspect ratio of the conductive particles is 2 or more. In the conductive adhesive according to claim 1 or 2,
The conductive adhesive is the matrix resin.
It is a microcapsule structure coated with a heat flexible resin,
And the conductive adhesive characterized by including the hardening | curing agent whose average particle diameter is 0.1 to 0.9 times the average particle diameter of the said electroconductive particle. A conductive film comprising a conductive adhesive layer made of the conductive adhesive according to any one of claims 1 to 3 formed on a carrier film. The printed wiring board which electrically connected the electronic component using the conductive adhesive in any one of Claims 1 thru | or 3. 6. The printed wiring board according to claim 5, wherein the conductive particles contained in the conductive adhesive are in a state of being oriented in a direction perpendicular to the connection surface by a magnetic field. The printed wiring board which electrically connected the electronic component using the conductive adhesive layer of the conductive film of Claim 4. The printed wiring board according to claim 7, wherein the conductive particles contained in the conductive adhesive are in a state of being oriented in a direction perpendicular to the connection surface by a magnetic field.

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