JP2001261974A - Paste composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an inexpensive paste composition slightly causing voids. SOLUTION: This paste composition comprises a metal powder consisting essentially of a scaly metal powder in which at least two kinds of the scaly metal powders different in thickness are used in combination in the paste composition comprising the metal powder and a resin composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a paste composition requiring thermal conductivity.

[0002]

2. Description of the Related Art Heretofore, a paste composition in which high heat conductive metal powder or high heat conductive inorganic powder is dispersed in a binder such as an epoxy resin has been used as a paste composition requiring heat conductivity. In addition, highly heat-conductive metal powder has been mainly used for paste compositions that require electrical conductivity.

[0003] Conventional paste compositions include electronic materials, 19
As described in paragraphs 42 to 46 of the October 1994 issue, a conductive powder such as gold, silver, copper, or carbon is used, and a binder, an organic solvent, and additives are added to the paste to form a paste. Was mixed and produced. Particularly in a field where high conductivity is required, gold powder or silver powder is generally used.

[0004] In addition, in the case of an adhesive paste composition such as die bonding which requires high thermal conductivity as well as electrical conductivity, it is often used with a large proportion of silver powder. However, when the mixing ratio of the silver powder is increased, there is a disadvantage that the silver powder is expensive and the paste composition is also expensive. Further, when the size of the scale is large and thin, the hiding power is large and voids are apt to remain when the solvent is dried.

[0005]

SUMMARY OF THE INVENTION The first aspect of the present invention is to provide an inexpensive paste composition in which the generation of voids is small. The inventions of claims 2 and 3 provide a paste composition having excellent thermal conductivity in addition to the invention of claim 1.

[0006]

According to the present invention, there is provided a paste composition containing a metal powder and a resin composition, wherein the metal powder is mainly flaky metal powder, and at least two kinds of flakes having different thicknesses. The present invention relates to a paste composition using metal powder in combination. The present invention also relates to the paste composition, wherein the thick flaky metal powder is 3 to 100 times as thick as the thin flaky metal powder. Furthermore, the present invention relates to the paste composition, wherein the flaky metal powder is obtained by flattening spherical or substantially spherical metal particles.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, scaly metal powder is a metal powder composed of small pieces that are almost flat in shape. Examples of the metal powder used for the flaky metal powder include silver powder, nickel powder, and aluminum powder. Of these, silver powder is preferably used.

In the present invention, the metal powder is mainly flaky metal powder, and it is necessary to use at least two types of flaky metal powder having different thicknesses together. For example, when a spherical or substantially spherical metal powder is used, the orientation of the metal particles deteriorates and the packing density does not increase, so that the thermal conductivity decreases. In order to increase thermal conductivity, a large amount of metal powder must be used, and if this is silver powder, it becomes expensive. Further, when one kind of flake-shaped metal powder having almost the same thickness is used, for example, when only a thin flake-shaped metal powder is used, a void is easily generated, and the heat conductivity is hindered. On the other hand, if only thick flake-like metal powder is used, the flakes become hard, and the viscosity control is difficult.

[0009] Of the flaky metal powder, the thick flaky metal powder is preferably 3 to 100 times the thickness of the thin flaky metal powder, and 3 to 50 times the thickness. More preferably, the thickness is less than three times, the effect of the combination is small, and voids tend to be easily generated. If the thickness is more than 100 times, the shape cannot be said to be scaly. Therefore, the orientation becomes poor, and the thermal conductivity tends to decrease.

The thin flaky metal powder used in the present invention generally has a mean particle size (size) of 2 to 10 μm which is sold as flaky metal powder (silver powder). Is preferably 0.05 to 0.5 μm,
More preferably, it is 0.05 to 0.3 μm.

On the other hand, the thick flaky metal powder has an average particle size (size) of 5 to 10 μm, and preferably has a thickness of 0.2 to 5 μm. 3 μm
Is more preferable.

In the present invention, if the spherical or substantially spherical metal particles are flattened as a means for obtaining scaly metal powder, the scaly particle diameter can be relatively easily controlled.
Further, depending on the conditions of the flattening treatment, the particle size and the thickness can be easily controlled, and the paste composition is preferable in terms of fluidity or easiness of plastic deformation.

The resin composition according to the present invention is composed of a thermosetting resin and its curing agent, a flexibility-imparting agent or, if necessary, a solvent. Examples of the thermosetting resin include epoxy resin, Phenol resin, polyamide resin, polyamide imide resin and the like can be mentioned. Among them, epoxy resins are liquid at room temperature, and can form a low-viscosity resin composition without a solvent or with a low solvent content.

As the epoxy resin used in the present invention, known resins are used, and compounds containing two or more epoxy groups in the molecular weight, for example, bisphenol A, bisphenol AD, bisphenol F, novolak, cresol novolaks and epichlorohydrin Aliphatic epoxy resins such as polyglycidyl ether, dihydroxynaphthalenediglycidyl ether, butanediol diglycidyl ether, neopentyl glycol diglycidyl ether, and heterocyclic epoxies such as diglycidyl hydantoin, vinylcyclohexene dioxide, Alicyclic epoxy resins such as cyclopentanedienedoxide and alicyclic diepoxy adipate are exemplified.

As the flexibility-imparting agent, those known in the art are used, and compounds having only one epoxy group in the molecular weight, for example, n
And ordinary epoxy resins such as butyl glycidyl ether, versidic acid glycidyl ester, styrene oxide, ethylhexyl glycidyl ether, phenyl glycidyl ether, cresyl glycidyl ether, butylphenyl glycidyl ether and the like. These epoxy resins and flexibility-imparting agents can be used alone or in combination of two or more.

The curing agent added to the resin composition includes
For example, amines such as mensendiamine, isophoronediamine, metaphenylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, methylenedianiline, phthalic anhydride, trimellitic anhydride, pyromellitic anhydride, succinic anhydride, tetrahydrophthalic anhydride Acid anhydrides such as, imidazole, compound-based curing agents such as dicyandiamide, polyamide resins, phenolic resins, resin-based curing agents such as urea resins are used, if necessary, with a curing agent such as a latent amine curing agent. It may be used in combination,
Further, a compound generally known as a curing accelerator between an epoxy resin and a phenolic curing agent, such as a tertiary amine, imidazoles, triphenylphosphine, and tetraphenylphosphenylborate, may be added.

[0017] The content of the above-mentioned curing agent is determined in terms of Tg (glass transition point) of the cured product of the conductive paste.
It is preferably in the range of 0.1 to 20 parts by weight, more preferably 1 to 10 parts by weight, based on part by weight.

The resin composition used in the present invention may further comprise a thixotropic agent, a coupling agent,
It is obtained by adding an antifoaming agent, a powder surface treating agent, an anti-settling agent and the like, and mixing them uniformly. The content of the thixotropic agent, the coupling agent, the defoaming agent, the powder surface treating agent, the anti-settling agent and the like added as needed is 0.01 to 1 with respect to the conductive paste.
%, Preferably from 0.03 to 0.5% by weight.
More preferably, it is in the range of weight%.

The mixing ratio of the flaky metal powder and the resin composition is not particularly limited as long as it can be handled as a paste. For example, the weight ratio of the flaky metal powder: resin composition is 95: 5-8.
A ratio of 5:15 is preferable in that good adhesive strength, electrical conductivity, thermal conductivity, and the like can be obtained, and a ratio of 93: 7 to 87:13 is more preferable.

The paste composition according to the present invention comprises, in addition to the metal powder and the resin composition, a thixotropic agent, a coupling agent, an antifoaming agent, a powder surface treating agent, an anti-settling agent, etc. It can be obtained by uniformly mixing and dispersing with a grinder, kneader, three rolls or the like. The content of the thixotropic agent, the coupling agent, the defoaming agent, the powder surface treating agent, the anti-settling agent, etc. added as necessary is in the range of 0.01 to 1% by weight based on the paste composition. Is preferred, and 0.
More preferably, it is in the range of 03 to 0.5% by weight.

In the present invention, when a paste composition containing flaky metal powder is applied thinly and a flat plate is pressed against the coated surface, the flaky metal powder in the paste composition is flattened. This is preferable because it is easy to orient in parallel.
At this time, if the scaly metal powder is only thin, the degree of orientation of the scaly does not increase because the scaly is easily deformed. The effect that not only the pieces are easily oriented but also the heat conductivity in the thickness direction of the paste composition is increased is obtained. Further, the contact effect between the thick flaky metal powders can be exerted by the deformation of the thin flaky metal powders.

[0022]

The present invention will be described below with reference to examples. Example 1 Bisphenol A type epoxy resin (oiled shell epoxy)
72 parts by weight, manufactured by Asahi Denka Kogyo Co., Ltd., trade name: ED
-503) 18 parts by weight, 2-phenyl-4-methyl-5
6 parts by weight of -hydroxymethylimidazole (manufactured by Shikoku Chemicals Co., Ltd., trade name: Curazole 2P4MHZ) and 4 parts by weight of dicyandiamide were added and uniformly mixed to obtain a resin composition.

Next, as a thin flaky metal powder,
A flaky silver powder having an average particle size of 3.2 μm and a thickness of 0.1 μm (trade name: TCG1 manufactured by Tokuri Kagaku Kenkyusho Co., Ltd.) is used. A reduced silver powder having an average particle size of 3 μm is 3 mm in diameter. Was flattened using a ball mill into which the glass beads were placed to obtain a thick flaky reduced silver powder having an average particle diameter of 7.7 μm and a thickness of 0.5 μm. Next, 20 parts by weight of the thin flaky silver powder and 80 parts by weight of the thick flaky reduced powder obtained above were blended and uniformly mixed to obtain a composite flaky metal powder.

To 13 g of the resin composition obtained above and 87 g of the composite flaky metal powder, 4 g of ethyl carbitol was added and uniformly mixed with a grinder to obtain a paste composition. Thereafter, the paste composition obtained above was dropped on a copper plate from which the surface was polished to remove rust.
A silicon chip having a size of 10 mm and a thickness of 0.3 mm is placed and pressed with a load of 100 g.
165 ° C at a rate of 30 minutes, and 165
The paste composition was cured by holding at 45 ° C. for 45 minutes.

When a cross section of the paste composition after curing was observed, no void was observed. Further, regarding the thermal conductivity, the thermal conductivity of the cured paste composition obtained above was set to 1 and compared with the following Examples and Comparative Examples. The thermal conductivity can be measured using a laser irradiation type thermal conductivity measuring device.

Example 2 The amount of silver was 1 with respect to the substantially spherical copper powder having an average particle size of 5.2 μm.
4% by weight silver-plated silver-plated copper powder with a diameter of 2
Flattening was performed using a ball mill containing zirconia beads having a diameter of 7.5 mm to obtain thick flaky silver-plated copper powder having an average particle diameter of 7.5 μm and a thickness of 3 μm. Next, Example 1
30 parts by weight of the thin flaky silver powder used in the above and 70 parts by weight of the thick flaky silver-plated copper powder obtained above were blended, and these were uniformly mixed to obtain a composite flaky metal powder. I got

Next, 4 g of ethyl carbitol was added to 11 g of the resin composition obtained in Example 1 and 89 g of the composite flaky metal powder obtained above, and the mixture was uniformly mixed with a grinder to obtain a paste composition. Was. Thereafter, the paste composition was cured through the same steps as in Example 1. The cross section of the paste composition after curing was observed, but no void was observed. Also,
As a result of measuring the thermal conductivity, it was 1.7.

Example 3 15 parts by weight of the thin flaky silver powder used in Example 1 and 85 parts by weight of the thick flaky silver-plated copper powder obtained in Example 2 were blended. By mixing uniformly, a composite flaky metal powder was obtained. Next, 5 g of ethyl carbitol was added to 8 g of the resin composition obtained in Example 1 and 92 g of the composite scaly metal powder obtained above, and uniformly mixed with a grinder to obtain a paste composition.

Thereafter, the paste composition obtained above was dropped on a copper plate whose surface was polished to remove rust, and a silicon chip having a size of 10 × 10 mm and a thickness of 0.3 mm was further dropped thereon. And press it with a weight of 200 g,
The temperature was raised at a rate of 100 ° C. for 60 minutes and further to 165 ° C. at a rate of 60 minutes, and held at 165 ° C. for 45 minutes to cure the paste composition. The cross section of the paste composition after curing was observed, but no void was observed. Moreover, the result of measuring the thermal conductivity was 3.2.

Comparative Example 1 Ethyl carbitol 5 was added to 13 g of the resin composition obtained in Example 1 and 87 g of the thin flaky silver powder used in Example 1.
g was added and uniformly mixed with a grinder to obtain a paste composition. Thereafter, the paste composition was cured through the same steps as in Example 1. Observation of the cross section of the paste composition after curing revealed small voids. The thermal conductivity was measured and found to be as low as 0.5.

[0031]

The paste composition according to the first aspect is an inexpensive and industrially very suitable paste composition which is free from voids. The paste compositions according to the second and third aspects are, in addition to the invention according to the first aspect, paste compositions having excellent thermal conductivity.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09D 187/00 C09D 187/00 F term (Reference) 4J002 CD011 CD021 CD031 CD051 CD061 CD101 CD131 CD191 EL037 EL138 EN038 EN078 ET008 EU118 FA016 FD116 FD148 GJ01 GQ02 4J038 DA061 DB001 DB051 DB061 DB071 DB261 DF001 DJ051 HA066 KA06 KA20 NA13 5G301 DA02 DA03 DA06 DA57 DD01

Claims (3)

[Claims] 1. A paste composition comprising a metal powder and a resin composition, wherein the metal powder is mainly scaly metal powder and a paste comprising a combination of at least two types of scaly metal powders having different thicknesses. Composition. 2. The thick flaky metal powder is 3 to 100 times as thick as the thin flaky metal powder.
A paste composition as described. 3. The paste composition according to claim 1, wherein the flaky metal powder is obtained by flattening spherical or substantially spherical metal particles.