JPS60202607A - Thermal conductive filler - 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 The present invention relates to a filler that has excellent heat dissipation properties and electrical insulation properties.

In recent years, as electronic products have become smaller and more highly integrated,
There is an increasing demand for the heat dissipation and electrical insulation properties of the components that make up these devices.

Conventionally, AJ, 03.5in2, Mg0%SiC has been used as an electronic circuit sealing material, thermal spraying material, or as a material for special substrates.
Single particulate fillers such as these are used.

However, Agi 203, SiO□, MgO, etc. have poor thermal conductivity and poor heat dissipation, and SIC has poor electrical insulation.

For this reason, it has been considered to improve thermal conductivity by coating metal particles with synthetic resin, such as epoxy resin, but these coated films have low strength and
In particular, the heat resistance and thermal conductivity were not sufficient.

In view of the above circumstances, the present invention aims to provide a thermally conductive filler with excellent heat dissipation, electrical insulation, and heat resistance. Thermal conductive filler has a core and the surface of the core is coated with metal oxide, soda-free glass, or a mixture thereof.

The present invention will be explained below.

The thermally conductive filler according to the present invention has fine particles of metal, carbon, or carbide with good thermal conductivity as a core with a particle size of 5 to 100μ, and the surface of the particles is coated with electrically insulating metal oxide or soda-free glass. It is a single substance or a mixture of the above metal oxide and soda-free glass coated with fine powder having a particle size of 4μ or less.

Examples of metals used for the core include Ag and Cu.

M o s F e SN i, W, and Si are used, but AJ has good thermal conductivity and can reduce the weight of the filler.
Each has advantages and disadvantages, and is used depending on the purpose: Cu has a low melting point and is thermally weak, Cu has good thermal conductivity but is heavy, and Sl is brittle and does not match the expansion coefficient with the Si substrate. Furthermore, artificial graphite is mainly used as carbon, and SiC is mainly used as carbide.

In addition, examples of electrically insulating metal oxides that coat the surface of the nucleus include he, Oa, S1o□, and MgO1Be.
A single substance such as O, mullite, or spinel, a single soda-free glass, or a mixture of an oxide and a soda-free glass are used. These coating materials are preferably fine powders of 4 microns or less.

The following methods can be used to coat the core with a metal oxide or soda-free glass (hereinafter referred to as coating material).

a) Method of granulating with binder As the binder, general-purpose adhesive resins can be used, but thermosetting resins such as phenolic resins and epoxy resins are preferred from the viewpoint of cost and resin properties.

The coating method is not particularly limited, but since the core particles are fine, high-speed agitation granulation is usually performed to prevent secondary agglomeration of the coating material to be coated. At the time of granulation, the finely powdered coating material and the binder may be made into a slurry and the cores may be added thereto, or the cores and the coating material may be mixed and the binder may be added thereto.

Furthermore, if a coupling treatment is performed as a pretreatment of the core and coating material, a strong coating layer will be formed. For example, a silane coupling agent (for example, KBM4 manufactured by Shin-Etsu Silicon Co., Ltd.
05) t- Pre-diluted with methyl alcohol, the coupling agent is finally applied to the core or coating material [L5w
The mixture was mixed with K so that t% remained, subjected to coupling treatment, and then dried at 80° C. for about 1 hour, and then subjected to the above-mentioned granulation.

In addition, the ratio of the core to the coating material in the above-mentioned granulation is preferably a weight ratio of core/coating material: 100/15 to 120, particularly a volume ratio of 1:1. If there is too little coating material, it will be difficult to coat it uniformly, and if it is too large, the coating layer will become thick and the heat dissipation of the filler will deteriorate. Also,
The amount of binder is a core/binder weight ratio of 100/1.
-7 is preferable.

If the amount of binder is too small, the film strength will be reduced, and if it is too large, heat dissipation will be poor.

b) Method using a completely volatile binder As the core, use a substance with a melting point of 700°C or higher, other than A6, which has a low melting point, and as a binder, one that completely decomposes and evaporates at 700°C or higher, such as a polyvinyl binder. Alcohol, polyethylene glycol, ethyl cellulose, CMC, cornstarch, etc. are used. These cores, coating material, and binder are granulated using substantially the same formulation as in a) above.

This granulated material is fired at a temperature of 700 to 1400°C,
The firing temperature varies depending on the material used, and is selected from a temperature range at which sintering occurs and is below the melting point. The higher the temperature and the longer the firing in this temperature range, the stronger the coating layer will be obtained. Further, as a matter of course, the firing atmosphere is usually a non-oxidizing atmosphere in order to prevent oxidation of the nuclei. However, if the oxide is easily reduced, such as Cu or Mo, the core may be fired in an oxidizing atmosphere and the oxide may be reduced in a hydrogen reducing atmosphere. For example, if the core is Cu, it can be heated to 900°C in a hydrogen stream, held for 2 hours, cooled to 200°C or less, and then taken out into the atmosphere, or heated to 900°C in the atmosphere and 2 hours later. After holding for an hour, it may be changed to a hydrogen atmosphere and held for one hour for reduction, and then cooled to 200°C and taken out into the atmosphere. When the core particles have a relatively low melting point, such as Cu, a filler with strong film strength can be obtained by adding 10 to 20 wt % of soda-free glass to the metal oxide.

C) Method of sintering by ejecting in a plasma stream First, using the same binder, core, and coating material as in a) or b) above, coat the core in the same manner. After this is dried, it is passed through a plasma stream to instantaneously sinter the coating material.

This method can also be applied when using low melting point metals such as Ag, and the coated insulating film is extremely strong.
And a uniform product is formed.

Next, the present invention will be specifically explained with reference to Examples and Comparative Examples.

In Examples and Comparative Examples, various fillers were made, the particles were sized to 10 to 105 μm, and the thermal conductivity,
The electrical insulation properties and coating film strength were measured and their superiority and inferiority were compared.

In addition, the electrical insulation property is 50% in the acrylic resin cylinder.
Filler was packed to a thickness of m, and both ends of the filled filler were sandwiched between Cu plates, a voltage of D~50° was applied, and the presence or absence of current between them was measured. As long as the insulation is 500V or more, there is no problem in practical use.

In addition, the film strength was measured using 13
Two +mOO steel balls were inserted and shaken 50 times at a stroke of approximately 10 strokes and 5 times/second. After shaking, the amount of powder of 5 μm or less was measured using a microphotosizer. The strength of the film was expressed by the generation rate of this powder.

In addition, a high-speed stirrer (trade name: Henschel mixer) was used for coating.

Examples 1 to 16 Fillers were made by the above methods using various cores, coating materials, and binders, and their properties were compared. The fillers used and the measurement results are shown in Table 1.

Comparative Examples 1 to 11 The same physical properties as in Examples were measured using samples without coating material and single particles, etc., which were sized to a particle size of 10 to 105μ. The particles used and their physical properties are shown in the second table.

As is clear from the table, it can be seen that there are defects in the following physical properties.

1. Filler coated with resin (Comparative Examples 1 to 3)
has a low service temperature of 150 to 200°C and has extremely poor thermal conductivity.

2 The ceramic alone (Comparative Examples 4 to 6) has poor thermal conductivity.

& Resin alone (Comparative Examples 7 to 9) has a low service temperature and extremely poor thermal conductivity. ◎ 4. Metals (Comparative Examples 10 to 11) have good thermal conductivity but no insulation at all.

In contrast, the product of the present invention has a high heat resistance of 200 to 800°C, excellent thermal conductivity, and has sufficient insulation properties for practical use, and the strength of the insulation film is sufficient.

As mentioned above, the filler according to the present invention has thermal conductivity,
It has good electrical insulation properties and coating film strength, making it particularly excellent as a material for electronic components, and is expected to have a wide range of other uses.

Claims (1)

[Claims] (Sato) It is characterized by having a granular core of one of metal, carbon, or carbide, and coating the surface of the core with metal oxide, soda-free glass, or a mixture thereof. Thermal conductive filler. (2) Particulate metal, carbon, or carbide is A6. Cu
. The thermally conductive filler according to claim 1, which is Mo, W, Fe, Nt, Sl, artificial graphite, and S1C. (3) The metal oxide is ke, O,, S 1o, , pg
o. The thermally conductive filler according to claim 1, which is BeO or mullite.