JPS61185806A - Conductive resin paste - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a conductive resin paste used for printed wiring, electrode formation for electronic components, and the like.

[Conventional technology]

! Highly conductive resin pastes have come into widespread use for the purpose of easily forming subcircuits by printing or for the purpose of replacing electronic parts with metal brazing such as soldering.

This conductive resin paste is made of thermosetting resin with silver and carbon.
A mixture of fine powders of metals such as carbon and copper is used. However, although silver paste using silver powder has excellent conductivity and stability, it has the drawbacks of high price and large fluctuations, and short circuit phenomenon due to silver migration during multilayer integration. there were.

Car on the other hand? Although the paste was inexpensive, it had poor conductivity and could only be used for limited purposes.

On the other hand, copper paste has been developed in recent years because it is less susceptible to migration and is inexpensive, but it has had the problem of poor conductivity and solderability due to oxidation of the copper powder.

Pastes using silver-plated glass pieces or copper powder have also been proposed, but the former's Mononoke plating peels off and the soldering is poor, while the latter's copper powder flakes. Alternatively, since it is dendritic, it has a large specific surface area and requires a large amount of plating solution, and has problems such as poor dispersibility of the powder and inability to spread over a uniform plating film.

These 4-stroke silver and copper powders are limited in shape to flakes or dendritic forms, and are therefore inferior in printability, adhesion, thermal conductivity, etc. as yeast.

[Problem that the invention seeks to solve]

The present invention has been made in view of the current situation and as a result of extensive research aimed at improving this, we have developed a highly conductive resin paste that is excellent in quality, reliability, and economic efficiency.

[Means for Solving the Problems] The present invention provides a conductive resin paste in which a conductive additive is blended with a thermosetting resin, and the conductive additive has an apparent density of 2.01//lyn". Above, 0,5~20μ
Granular metal powders, such as copper, copper alloys, with an average particle size of
For metal powders such as nickel, nickel alloys, iron, and iron alloys,
The present invention is characterized in that it uses granular metal powder whose surface is plated with at least one metal different from the metal, such as gold, platinum, tsucladium, silver, tin, and solder.

The reason why the above metals are selected as the granular metal powder to be plated in the present invention is that these metals are inexpensive, have excellent conductivity, and can be easily subjected to chemical plating. The metal powder may be a fine spherical powder, a long spherical powder close to a sphere, or a mixture thereof, and the average particle size is limited to 0.5 to 20μ, preferably 1 to 10μ. However, the reason is that the average particle size is 0.5
If it is less than .mu., the surface of the metal to be plated will be significantly oxidized, making it difficult to form a uniform plating film and requiring a large amount of plating solution during plating. If the thickness exceeds 20 μm, the screen may become clogged during paste application, which may impede printability.

The reason for limiting the apparent density to 21/7cm3 or more is that if it is less than 211/(7)3, the plating properties of the powder, the printability of the paste, the adhesion to the substrate, and the thermal conductivity of the cured coating film. This is because they are inferior in sex.

The nuclear metal powder preferably has a surface as smooth as possible and is not oxidized.

As the conductive material, gold, platinum, palladium, silver, tin, or solder was selected as the metal to be plated on the granular metal powder to be plated. In the case of gold, platinum, and palladium, there are almost no problems caused by migration or oxidation of the metal powder to be plated, so they are used in fields that require high reliability, such as conductive bonding of crystal resonators and semiconductor silicon devices. . In the case of silver, there is a concern about silver migration, but since the paste itself is cheap and has excellent conductivity, and only the surface is coated with silver, only the silver on the surface is protected from being eaten away by the solder during soldering. The metal to be plated does not change at all, only the wrinkles are reduced. Therefore, good soldering indicates good soldering properties and soldering heat resistance.

In addition, in the case of solder or tin plating, there is no risk of migration and it is stable, and by changing the composition of the solder, sintering of the powder progresses under the curing conditions of the coating film at 100 to 300°C, so it is extremely good. It is possible to form a stable conductor circuit by using In particular, tin-plated products exhibit excellent solderability. This plating can be easily done by ordinary chemical plating, and the amount of plating applied depends on the particle size of the metal powder to be plated, but 1-20 wt of metal powder weight
% is preferred.

In the present invention, the thermosetting resin to which the conductive additive is blended forms a stable cured coating in a high temperature atmosphere of 300°C or less, and has heat resistance for about 10 seconds in molten solder at 150 to 300°C. Any material may be used as long as it has the same properties and adheres sufficiently to paper, phenol, glass epoxy, ceramics, and metal substrates, such as phenol resin,
Examples include thermosetting resins such as epoxy resins, polyimide resins, and polyamideimide resins, and mixtures of these resins.

The blending amount of the thermosetting resin is 5 to 2 with respect to the conductive material.
The content is preferably in the range of 5 wt%, and can be obtained by thoroughly kneading the two in a three-roll mill or the like.

[For production]

The first feature of the present invention is that the conductive material is formed by chemically plating the surface of spherical metal powder, and this spherical metal powder is different from flakes or dendritic powder having the same particle size distribution. When compared, it has a small specific surface area and can form the thickest plating film for the same amount of plating solution. Furthermore, since spherical metal powder has excellent dispersibility, a uniform film can be created by simply stirring the solution during plating.

A conductive paste made by kneading this conductive additive material into a thermosetting resin exhibits good printability without clogging the screen during printing, and also has good adhesion to the substrate as a paste containing flaky powder. Since the bonding area between the resin and the substrate is larger than that in the conventional method, the adhesion strength is improved.

Furthermore, since the amount of the conductive additive contained in the conductive resin paste of the present invention is based on spherical powder, the cured coating film has excellent thermal conductivity and is suitable for bonding semiconductor elements. Note that since semiconductor elements generate heat, a conductive adhesive with good thermal conductivity is required for bonding them.

Next, examples of the present invention will be described.

Examples (1) to (6) 1 kg of each of the metals and alloys shown in Table 1 was heated and melted and pulverized by the molten metal atomization method. Hanging density 3.6-4.0 I
/lvn'' spherical metal powder was obtained.

These metal powders 100. F was immersed in a silver plating solution (Kojundo Kagaku Kenkyujo [8-900)], heated to 40°C, and the solution and powder were stirred to obtain a plated metal powder coated with 8 to 10 wt%.

85 parts by weight of this powder and 15 parts by weight of resol type phenolic resin were kneaded to obtain a conductive resin paste of the present invention.

Examples (7) to (11) Pure copper molten metal was atomized to have an average particle size of 8.1μ and an apparent density of 4.2! i'/an'' copper powder was prepared, and this was applied to gold plating solution (Kojundo Kagaku Kenkyujo fiK-24), platinum plating solution (Kojundo Kagaku Kenkyu Shinsei Pt-5), and palladium plating solution (Kojundo Kagaku Kenkyu Shinsei Pt-5). Pd-5, a new product), tin plating solution (GLS-500B, a new product of Kojundo Kagaku Kenkyu), solder plating solution (Kojundo Kagaku Kenkyujo [5P-64El), etc., and the same procedure as in Example (1) was carried out. and obtained plating metal powder.

Next, 85 parts by weight of these plated metal powders and 15 parts by weight of resol type phenolic resin were kneaded to obtain a conductive resin paste of the present invention.

Comparative Examples (1) to (4) Flake-like silver powder, flake-like copper powder, flake-like silver-plated copper powder, and dendritic electrolytic copper powder having particle sizes and apparent densities shown in Table 1 were each resol-formed to 80 wt*. A comparative example conductive resin paste was obtained by heating 20 wt % of type phenolic resin. In the case of steel yeast, 0.5 wt '4 of organic acid was added and the product of the present invention and comparative example were obtained in this manner. In order to test the performance of the product, a zigzag TJ? Im width and 200 sll length was used with a 200 mesh screen. print the turn,
A circuit with a thickness of 30 μm was prepared by heat curing at 160° C. for 30 minutes, and the circuit volume resistivity, printability, adhesion strength, solder properties, solder heat resistance, and thermal conductivity of the JigDekno pattern were measured. The results are summarized in Table 1.

The printability in the table is evaluated from the variation in circuit resistance by running the same circuit 500 times in a row, and 0. All values falling within ±80 degrees were marked Δ, and all others were marked ×.

Adhesion to the substrate was evaluated by soldering a 3 mm diameter copper wire onto the heat-cured coating film, pulling both together using a tensile tester, and evaluating the strength at the time the coating peeled off from the substrate.

In addition, for soldering, after immersing the board on which the circuit is printed for 2 seconds in a thin flux solution, the Pb-63%Sn
The sample was immersed in molten solder at 230° C. for 2 seconds, taken out, and the solder wetting area relative to the printed area was measured.

To determine the solder heat resistance, the same circuit was subjected to the same test as above for 10 seconds and the change in circuit resistance was measured.

In the solderability and solder heat resistance 1c, ◯ indicates good, ∆ indicates fair, and × indicates poor.

As is clear from the above table, the conductive resin paste according to the present invention was found to have excellent properties.

〔effect〕

The conductive resin paste of the present invention has excellent adhesion to a substrate, soldering properties, etc., and is extremely economical because it uses an inexpensive metal as the paste. Therefore, it is extremely useful as a conductive yeast for electronic parts, and has extremely large industrial value.

Applicant's agent Patent attorney Takehiko Suzue Procedural amendment 41 Year 61. Office, 11 Commissioner of the Patent Office Michibe Uga1, Indication of the case, Patent Application No. 1988-248812, Name of the invention Conductive resin paste3, Person making the amendment Relationship to the case Patent applicant (529) Koga area Ki Kogyo Co., Ltd. 4, agent 5, voluntary amendment 6, subject to arrest 1. :,
-7. Contents of amendment (1) In Table 1, page 12 of the specification, the numerical value in the "Thermal conductivity" column is corrected as follows.

Record

Claims (3)

[Claims] (1) In a conductive resin paste made by blending a conductive additive into a thermosetting resin, the conductive additive has an apparent density of 2.0 g/cm^3 or more and a thickness of 0.5 to 20μ. A conductive resin paste characterized by being made of a granular metal powder having an average particle size and plated with a metal different from the metal on the surface of the granular metal powder. (2) The conductive resin paste according to claim 1, wherein the granular metal powder is made of any one of copper, copper alloy, nickel, nickel alloy, iron, and iron alloy. (3) The conductive resin paste according to claim 1, wherein the plating metal is made of any one of gold, platinum, palladium, silver, tin, and solder.