TW201606042A - Metal-coated resin particles and electroconductive adhesive in which same are used - Google Patents

Abstract

Provided are metal-coated resin particles that comprise resin particles and a metal coating layer that covers at least some of the resin particles, wherein it is possible to obtain a high-reliability electrical connection after repeated compression. There are used metal-coated resin particles that have an average grain diameter of 1-100 [mu]m and exhibit a recovery of at least 90% after 30% compressive deformation, the metal coating layer comprising a metal having a Vickers hardness of 100 or less and an average thickness of 20-150 nm.

Description

Metal-coated resin particles and conductive adhesives using the same Technical field

The present invention relates to a metal-coated resin particle and a conductive adhesive using the same.

Background technique

The metal-coated resin particles which are blended in the conductive adhesive such as the electrode connection of the printed wiring board are often coated with the following metal-coated resin particles, that is, the noble metal such as gold, and the nickel-coated layer is coated with the acrylic resin. The resin particles are composed.

For example, Patent Document 1 discloses a conductive microparticle for providing conductive microspheres having moderate compression deformation and deformation recovery property and excellent connection reliability, and has a conductive microparticle having a compression deformation of 10%. A surface of the microsphere having a K value of 50 to 250 kgf/mm ² and a high recovery coefficient of 15 to 100%, and a conductive layer composed of a nickel-gold plating film.

Further, Patent Document 2 discloses a conductive electroless plating powder which is subjected to nickel or nickel-gold plating on spherical particles of 1 to 30 μm.

The nickel layer is used as described above to improve the adhesion of the noble metal such as gold to the resin particles. However, the nickel layer is very hard, when the adhesive is pressed It is prone to cracks or cracks. Further, when the acrylic resin particles are deformed by pressing or the like, the stress generated in the direction in which the particle shape returns is strong, and this is combined with the presence of the nickel layer to cause a decrease in the adhesion between the resin particles and the metal layer. Therefore, the decrease in the adhesion force may cause the resistance to rise or break, and it is difficult to ensure stable conduction.

In order to face such problems, it is necessary to have a metal-coated resin particle which does not use a nickel layer to ensure adhesion between the metal and the resin, and to obtain a highly reliable electrical connection.

In order to solve this problem, on the one hand, the metal type or the coating method of the metal layer is explored. For example, it is proposed in Patent Document 3 that in order to obtain conductive fine particles in which the metal and the resin are in close contact with each other, a pH of more than 7 or less than 8 is used. The low-resistance metal plating bath is coated to reveal that the low-resistance metal ion is preferably copper ion or silver ion.

On the other hand, the orientation of the resin particles is also completed. As an example of using a resin other than the acrylic resin, Patent Document 4 discloses a synthetic resin fine particle copolymerized with a polymerized acrylic monomer and a carboxyl group monomer. The composition is constructed, and in the examples it is shown that silver is applied or gold is applied by sputtering.

Further, Patent Document 5 discloses a conductive fine particle coated with a polyimide resin having a predetermined glass transition temperature, a polyester resin, a polyamide resin, and a ring by a conductive metal such as silver. Polymer microparticles composed of an oxygen resin or the like.

However, in the metal-coated resin particles, the adhesion between the resin particles and the metal is also lowered as the resin is repeatedly compressed and deformed, and is used in the guide. In the case of an electrical adhesive, a highly reliable electrical connection is not obtained.

Advanced technical literature Patent literature

[Patent Document 1] Japanese Patent No. 3241276

[Patent Document 2] Japanese Patent Laid-Open Publication No. Hei 8-311655

[Patent Document 3] Japanese Patent No. 4347794

[Patent Document 4] Japanese Patent Publication No. Hei 10-259253

[Patent Document 5] JP-A-2006-12709

Summary of invention

The present invention has been made in view of the above, and it is an object of the invention to provide a metal-coated resin particle which exhibits high conductivity when blended with a conductive adhesive or the like, and which has a conductivity which is more stable against repeated compression deformation, and which can be reliably obtained. Higher electrical connection.

The metal-coated resin particles of the present invention are composed of resin particles and a metal coating layer covering at least a part of the resin particles, and the average particle diameter of the resin particles is 1 to 100 μm, and the recovery ratio after compression at 30% is 90. Above or more, the metal coating layer is composed of a metal having a Vickers hardness of 100 or less and an average thickness of 20 to 150 nm.

Further, the metal-coated resin particles of the present invention preferably have a force of 30 mN or less which is required to have a displacement of 30% or less.

The above resin particles can be made of a urethane resin to make.

The metal coating layer is preferably composed of one or more metals selected from the group consisting of gold, silver, palladium, platinum, and copper.

The conductive adhesive of the present invention can be obtained by blending the metal-coated resin particles of the present invention in a ratio of from 1 to 100 parts by mass based on 100 parts by mass of the resin component.

Further, the printed wiring board of the present invention is formed by connecting the electrodes using the above-mentioned conductive adhesive.

As described above, the metal-coated resin particles of the present invention are coated with a metal having a predetermined Vickers hardness without using a nickel layer, and resin particles having a predetermined recovery ratio are used, whereby the highly reliable electrical connection is further excellent.

Therefore, when the metal-coated particles are used for, for example, an anisotropic conductive adhesive for electrode connection, a printed wiring board having improved connection reliability can be obtained.

1,1’‧‧‧ particles

2‧‧‧ platform

3‧‧‧Indenter

4‧‧‧resistance tester

11‧‧‧Flexible printing plate

12‧‧‧Glass epoxy substrate

Fig. 1 (a) and (b) are schematic views showing a compression test method of particles using a micro compression tester.

Figure 2 is a graph showing the relationship between the load applied to the particles and the displacement of the particles.

Fig. 3 is a schematic view showing a method of measuring the resistance value of the metal-coated resin particles.

Figure 4 is a plan view showing the measurement method of the connection resistance.

Form for implementing the invention

Hereinafter, embodiments of the present invention will be described more specifically.

The resin particles used in the present invention preferably have a recovery ratio of 30% or more after 30% compression deformation, and more preferably 98% or more. In the case of such resin particles having a high recovery ratio, even if the compression and recovery are repeated, the recovery rate is not lowered, and a highly reliable electrical connection can be obtained.

Further, when the metal-coated resin particles are used for the anisotropic conductive adhesive, the conductive adhesive can be obtained by a small pressing pressure and can be electrically connected with a highly reliable electrical connection. The pressure of the metal-coated resin particles used in the present invention, which is preferably 30% displacement, is 20 mN or less, and more preferably 10 mN or less.

Although the acrylic resin used in the past has high elasticity and recovery rate, since the stress required for deformation is large, plastic deformation is usually caused by compression deformation of 10% or more, and if it is larger than this, the recovery rate is remarkably lowered. . Further, when the acrylic resin recovers from deformation, the stress equivalent to that at the time of deformation acts on the electrode to be bonded, and it is generally considered that the peeling of the adhesive layer and the electrode is likely to occur around the conductive particles. The resin particles used in the present invention have a high recovery ratio after 30% compression deformation and a small stress required for deformation, whereby the above problems are solved, and it is considered that the reliability of the metal-coated resin particles is improved.

The resin particles having the above recovery ratio are not particularly limited, and resin particles composed of a urethane resin can be suitably used. More specifically, from the viewpoint that the physical properties can be easily obtained, for example, the following bullets disclosed in JP-A-2008-156610 can be cited. Resin particles or the like, that is, an elastic resin particle containing a crosslinked copolymer of a urethane resin (A1) and a compound (B), and the aforementioned urethane resin (A1) is selected from At least one of the polymer polyol (a) and the diisocyanate (b), which are composed of a polyester polyol, a polyether polyol, a polyether ester polyol, and a polycarbonate polyol, has an essential component and has a carbon-carbon double bond, the above compound (B) does not have a urethane bond, and has a number average molecular weight of 100 to 1000 and has two or more carbon-carbon double bonds; and an elastic resin particle containing an amine group a crosslinked copolymer of a formate resin (A2) and a compound (B), and the aforementioned urethane resin (A2) has a diisocyanate trimer (h) as an essential component and has a carbon-carbon double bond The compound (B) does not have a urethane bond, and has a number average molecular weight of 100 to 1,000 and has two or more carbon-carbon double bonds. Among the commercially available products, for example, DAIMICBEAZ CM (trade name) manufactured by Dairi Seiki Co., Ltd. can be cited.

The shape of the resin particles is not limited, but it is preferably spherical if it is considered to be used for an anisotropic conductive adhesive or the like. Further, when the use of the anisotropic conductive adhesive is also considered, the particle size is preferably an average particle diameter of 1 to 100 μm, and more preferably 10 to 30 μm.

Next, in the present invention, the metal layer to be coated with the resin particles is preferably composed of a flexible metal having a Vickers hardness of 100 or less, and the Vickers hardness is more preferably 50 or less, and further preferably 30 or less.

Specific examples of the metal having such Vickers hardness include gold (Au) (Vickers hardness of about 22), silver (Ag) (Vicker hardness of about 26), and palladium (Pd) (Vicker's). Hardness is about 47), platinum (Pt) (Vicker hardness is about 56), copper (Cu) (Vicker hardness is about 37), and it is preferable to use one or more of these kinds of gold. Genus. When two or more kinds of metals are used, the two or more kinds of metals may be alloys, or the single metal may be mixed in a layer structure or a matrix structure, or may be a combination thereof.

The thickness of the metal layer is preferably an average thickness of 20 to 150 nm, and more preferably 50 to 100 nm, in consideration of conductivity and connection stability and cost.

The metal layer is formed as at least a part of the surface of the coating resin particle. However, when it is considered to be used for an anisotropic conductive adhesive or the like, it is preferable to coat the entire surface of the resin particle.

The metal coating method is not particularly limited, and the method used so far can be widely used. Examples thereof include a method using electroless plating, a method using electroplating, vacuum evaporation, ion plating, ion sputtering, and the like. However, since film formation is uniform, electroless plating is preferable.

Further, as an ideal aspect of the electroless plating, in order to form a uniform coating of the metal coating layer and to improve the adhesion to the surface of the resin particles, first, a catalyst layer is provided on the resin particles, and then the metal layer is coated. The catalyst layer can be formed by palladium (Pd), platinum (Pt), gold (Au) or the like. The thickness of the catalyst layer is preferably from 1 to 100 nm.

As described above, by forming a resin particle having a high recovery ratio with a moderate thickness by a flexible metal and not having a hard layer such as a nickel layer, the shrinkage and expansion of the adhesive can be freely accommodated, and therefore, even if it is repeated The metal-coated resin particles are repeatedly deformed by compression and the particles are returned without causing metal peeling. Therefore, even an electrode such as a material which is thin and fragile like an electrode using vapor deposition or ink jet can be used without being damaged. Also, in the case of an anisotropic conductive film (ACF), the interlayer distance should be uniformly limited. In the use of the (adhesive thickness), since the resin particles are freely deformable for pressing, it is possible to obtain an advantage that it is not necessary to use resin particles which strictly conform to the particle diameter distribution.

The metal-coated resin particles of the present invention can be used in various applications such as various conductive adhesives in place of the conductive particles conventionally used. The resin component constituting the conductive adhesive is not particularly limited as long as it has adhesion to the subsequent object, and can be widely used for the same purpose. For example, examples of the thermosetting resin include an epoxy resin, a phenol resin, and a melamine resin. Examples of the thermoplastic resin include a polyolefin resin, an acrylate resin, and a polystyrene resin. Resin. Examples of the polyolefin resin include polyethylene, an ethylene-vinyl acetate copolymer, and an ethylene-(meth)acrylate copolymer. Examples of the acrylate-based resin include polymethyl (meth) acrylate, polyethyl (meth) acrylate, and polybutyl (meth) acrylate. Examples of the polystyrene resin include polystyrene, styrene-acrylate copolymer, styrene-butadiene block copolymer, styrene-isoprene block copolymer, and the like. Isoblock polymers and the like. Further, a composition which is cured by heat or light, such as a curable resin composition obtained by a reaction with a curing agent such as a monomer or oligomer having an epoxy group and an isocyanate, may be used. Further, as an example, a resin component disclosed in Japanese Laid-Open Patent Publication No. 2010-168510 (Patent No. 4,580,021), which is composed of a polyamine-based elastomer, 10 to 80 parts by weight, and a polyaminocarboxylic acid can be suitably used. 10 to 80 parts by weight of the ester elastomer and 10 to 80 parts by weight of the styrene-isobutylene-styrene copolymer, and having a polyurethane elastomer and styrene-isobutylene dispersed in the polyamide elastomer - phase of styrene copolymer Separate construction. Further, it can also be suitably used as an adhesive for metal parts containing a phenoxy resin having a predetermined glass transition temperature and a filler as essential components.

The content of the metal-coated resin particles in the above-mentioned conductive adhesive is different depending on the use of the adhesive, etc., and is preferably 1 to 100 parts by mass based on 100 parts by mass of the resin component, and more preferably 1 to 50 parts by mass.

In the conductive adhesive of the present invention, other additives used for the conductive adhesive may be further blended as long as it does not contradict the object of the invention. Examples of such an additive include a filler, an antioxidant, an antifoaming agent, a tackifier, an adhesion-imparting agent, and the like.

The use of the above-mentioned conductive adhesive of the present invention is not particularly limited, and it is intended to be suitably used when a transparent electrode is connected to a printed wiring board. The method is not particularly limited, and specific examples include a method in which a conductive adhesive is screen-printed on a substrate, and the substrate is heated together to volatilize the solvent, and electronic components such as transparent electrodes are mounted thereon. The cured adhesive is hot pressed.

Example

The embodiments of the present invention are shown below, however, the present invention is not limited to the following embodiments. In the following, as long as it is not specifically stated in advance, the blending ratio or the like is used as a quality standard.

1. Adjustment and evaluation of metal coated resin particles

Metal-coated resin particles were formed using the resin particles shown in Table 1 respectively. The recovery rate of the resin particles after 30% compression deformation is used in a small amount The compression tester (Shimadzu Corporation, MCT-510) was used to measure by the following method.

As shown in Fig. 1, the micro-compression tester used compresses the particles 1 on the platform 2 by the indenter 3, and electrically compresses the compression load as an electromagnetic force, and the compression displacement is made according to the displacement of the actuating transformer. It can be detected by electrical means. The platform 2 is composed of a steel plate and is a smooth gantry. The ram 3 is made of stainless steel and has a truncated cone shape that converges downward. The end surface is rounded and has a smooth surface before being joined with the particles. Fig. 1(a) shows that the indenter 3 presses the state before the start of compression of the particles on the stage 2 with a minimum force, and (b) shows the state in the compression, and the particles 1' are deformed by compression. As indicated by the arrow mark in (b), the indenter 3 is configured to be lowered in the vertical direction with respect to the upper surface of the stage 2 during compression, and can be stopped at a predetermined position. The distance X from the state in which the indenter 3 is moved from the state of (a) to the state of (b) is regarded as the displacement amount of the particles. The diameter of the particles is R μm, and the compression ratio when the a μm is compressed in the vertical direction (X = a μm) is expressed by the following formula.

Compression ratio (%) = (a / R) × 100

When the relationship between the load P applied to the particles and the displacement amount X of the particles is shown in a graph, it will be as shown in FIG. As the amount of displacement X of the particles is decreased as the indenter 3 is lowered, as shown by the solid curve a of the graph, the load acting on the particles becomes large. After compressing the particles to the inversion load value (if the target displacement amount is 30%, the load value reaches 30%), if the indenter 3 is raised to reduce the displacement amount X of the particles, a curve d is obtained as a broken line b. Chart.

When the load is reduced and the indenter 3 is naturally stopped (the load value at this time point is made the "origin load value". 0.05 g or more.) The measurement is stopped. And the value of the ratio (L2/L1) of the displacement amount L1 from the origin load value point to the reversal point and the displacement amount L2 of the origin point load value point is obtained by %, and the compression deformation is performed. Response rate.

Further, in the specific operation, the resin particles 1 are spread on the stage 2, and one of the resin particles 1 selected from the resin particles 1 is compressed by a circular front end surface of the indenter 3 having a diameter of 50 μm. The compression was carried out at a constant load speed, and the compression rate was 0.15 mN/sec in the urethane and 10.4 mN/sec in the acrylic acid. The maximum stress is 50-1960 mN, and the measurement temperature is 20 °C.

A palladium layer (average thickness: 5 nm) as a catalyst was formed on the surface of the above resin particles by the following method. Further, here, an example of 1 g of urethane particles (DAIMIC CM) having an average particle diameter of 20 μm is shown. However, even if the types of particles or the particle diameters are different, they can be carried out according to them.

10 g of sucrose was added to 1 L of an aqueous solution containing palladium chloride (PdCl ₂ ) 20 mM (mole) and sodium chloride (NaCl) 0.1 M (mole), and sodium borohydride (NaBH ₄ ) was added dropwise while stirring. A colloidal palladium solution having an average particle diameter of 5 nm was obtained. The resin particles which have been previously washed with a 1 M aqueous solution of sodium hydroxide (NaOH) are immersed in a 1% aqueous solution of trimethyloctadecylammonium chloride, and then immersed in the above-mentioned colloidal palladium solution and dried. The entire surface of the particles forms a palladium layer having a substantially uniform thickness.

Next, the metal-coated resin particles shown in Table 1 were formed on the resin particles having the palladium layer by electroless plating to prepare metal-coated resin particles.

As shown in Table 1, the metal layers of Examples 1 to 3 and Comparative Examples 3 to 5 were a single layer of Ag (Vickers hardness 26), and the metal layer of Example 4 was Au (Vicker's). A single layer of hardness 22). Example 5 is a two-layer structure in which an Ag layer is provided as the outermost layer on the Cu layer (Vicker hardness 37), and Comparative Example 1 is a two-layer structure in which an Au layer is provided as the outermost layer on the Ni layer, and Comparative Example 2 is An Ag layer is provided on the Ni layer as a double layer structure of the outermost layer.

The Vickers hardness of the above metal is measured in accordance with JIS Z 2244:2009.

Further, the average thickness of the metal layer is measured by the weight change before and after the metal particle coating of the resin particles, and the difference is made into the weight of the metal layer, and the weight is divided by the average surface area of the resin particles of the adherend. In the examples, it is assumed that the size of each of the fine particles is constant and the material of the metal coating step is not lost, and the total weight of the metal-coated resin particles is M, and the total weight of the resin particles before the metal coating is set to M ₀ . The total surface area of the particles was set to A, and the specific gravity of the metal layer was calculated by the following formula by setting the specific gravity of the coated metal to ρ.

T=(MM ₀ )/ρ A

Further, the value of the total surface area of the resin particles is an approximation using the following values, that is, the weight of the total resin particles divided by the weight of one particle obtained from the average particle diameter of the resin particles, and multiplied by the average The surface area of one particle of the particle diameter.

With respect to the obtained metal-coated resin particles, the force necessary for the 30% displacement and the repeated compression test (measurement of the resistance values after the cycle compression of 1, 5, 50, and 100) were carried out by the following method. Table 1 shows the results.

The force necessary for the 30% displacement of the metal-coated resin particles is to investigate the respective metal-coated resin particles using the above-described micro compression tester and conditions. The relationship between the displacement amount X of the sub-particle and the load P, and the load in the displacement amount X (a μm) which is 30% in the compression ratio obtained by the above formula is obtained.

The reverse compression test was carried out by the following method using a micro compression tester (manufactured by Shimadzu Corporation, MCT-510). That is, for each sample, a load-unload cycle of the load required for the 30% compression deformation determined as described above was performed to 100 cycles, and 1, 5, 50, and 100 were respectively performed at a measurement temperature of 20 ° C. The resistance of the metal-coated resin particles during the cycle was measured.

In addition, the compression is performed by a certain load speed, and is set to a holding stroke of 10 seconds, an unloading stroke of 10 seconds, a maximum load, and a minimum load (origin load) of 1 second. Further, as shown in Fig. 3, the electric resistance of the metal-coated resin particles is formed between the platform 2 made of a steel plate and the end surface of the stainless steel indenter, and a resistance measuring device 4 (ADC1, 7351E, DC) is used. Method) to determine.

2. Adjustment and evaluation of conductive adhesives

The conductive coating agent is prepared by blending the metal-coated particles obtained as described above with a thermoplastic resin component. The details of the resin component used were as follows, and 1.5% by mass of the obtained conductive adhesive was prepared. Conductivity was investigated by the following method for the obtained conductive adhesive. Table 1 shows the results.

Resin: Thermoplastic elastomer (resin component of "CBP-700" manufactured by TATSUTA Wire Co., Ltd.)

Conductivity (initial): as shown in FIG. 4, it has been fabricated by a conductive adhesive followed by a flexible printed board (FPC) 11 and a glass epoxy substrate 12. The FPC/PTF test sample was measured for the connection resistance between the terminal terminals (between ab, bc, and cd) of the flexible printed board 11 by using a low resistance meter (manufactured by Hioki Electric Co., Ltd., DC mode 3227 Milliohm HiTester). And find the average.

As is clear from the results shown in Table 1, the measured values of the metal-coated resin particles of the examples in the respective cycles of the reverse compression test were error-free and stable, whereas the comparative examples showed large errors, and also included as Comparative Example 4 And 5 kinds of infinitely large.

Further, the initial conductivity of the conductive adhesive using the metal-coated resin particles of the present invention was equal to or higher than that of the comparative examples, and in particular, Examples 2, 3, and 5 were remarkably excellent. The initial conductivity of Example 1 was substantially the same as that of Comparative Examples 1 to 3 and 5. However, as described above, since the results of the reverse compression test were excellent, it was generally inferred that the long-term electrical connection reliability was higher than that of the comparative example.

Claims (6)

A metal-coated resin particle comprising a resin particle and a metal coating layer covering at least a part of the resin particle, wherein the resin particle has an average particle diameter of 1 to 100 μm and a recovery after 30% compression deformation The rate is 90% or more, and the metal coating layer is composed of a metal having a Vickers hardness of 100 or less and an average thickness of 20 to 150 nm. The metal-coated resin particles of claim 1 have a force necessary for 30% displacement of 20 mN or less. The metal coated resin particle of claim 1 or 2, wherein the resin particle is composed of a urethane resin. The metal-coated resin particles according to claim 1 or 2, wherein the metal coating layer is composed of one or more metals selected from the group consisting of gold, silver, palladium, platinum, and copper. A conductive adhesive which is a metal-coated resin particle according to claim 1 or 2 in an amount of from 1 to 100 parts by mass based on 100 parts by mass of the resin component. A printed wiring board using the conductive adhesive of claim 5 to connect the electrodes.