JPH01232796A - Manufacture of metal core insulated board - Google Patents

Abstract

PURPOSE:To manufacture a metal core insulated board excellent in heat dissipation by subjecting the board to thermocompression while interposing a bonding agent having metal powders mixed between a thermally sprayed ceramic layer formed by thermally spraying a ceramic on one side of a metal foil and a metal plate forming the core of the board. CONSTITUTION:Alumina is plasma sprayed onto one side of a copper foil 1 by using a plasma flaming device to form a plasma sprayed alumina layer 2. A bonding agent 3 in which aluminum powder is added to an epoxy resin is applied to the alumina layer 2 and the alumina layer 2 is arranged on an aluminum plate 4 which will form the core of the board. Further, this is subjected to thermocompression forming by a press to obtain a metal core copper foil laminated board which will cause the bonding agent to be set. Further, a pattern is formed on the uppermost surface copper foil layer by such conventional methods as etching. The metal core insulated board obtained in this way is not only excellent in interlayer adherence and thus resistant against thermal shock but also highly excellent in thermal dissipation.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a method for manufacturing a metal core insulating board with excellent thermal conductivity and heat resistance. laminate,
Epoxy super fat laminates were often used. However, as electronic equipment has recently become more sophisticated and more compact, it has become a problem how to deal with the high density of components.

On the other hand, 1. Conventional organic substrates lack heat dissipation properties due to poor thermal conductivity, and also have poor heat resistance, making it difficult to implement high-density packaging. .

Therefore, as substrates with excellent thermal conductivity, ceramic substrates such as alumina, aluminum nitride, silicon carbide, etc., or metal core substrates having a metal plate as a core and an insulating layer provided on the surface are attracting attention. In particular, metal core substrates are cheaper and easier to process than ceramic substrates,
Furthermore, since the core is made of a metal such as aluminum with high thermal conductivity, it is attracting attention because of its high heat dissipation properties.
It has become widely used. Research and development to improve performance for this purpose is actively being conducted.

(Problems to be Solved by the Invention) A general metal core board has an insulating layer of a glass epoxy resin layer with a thickness of 50 to 100 μm provided on the surface of a metal plate such as aluminum, and a copper plate on which a circuit is formed. It has a foil pasted on it. That is, what is in direct contact with the circuit is a resin layer with poor thermal conductivity. Therefore, the heat generated in the circuit is transmitted to the core metal plate through the extremely fat layer, which has poor thermal conductivity. For this reason, the thermal conductivity of the metal core cannot be fully utilized, and sufficient heat dissipation cannot be obtained.

For this reason, in order to improve this problem, an attempt has been made to spray ceramic such as alumina onto the surface of the core metal plate to provide a ceramic insulating layer instead of using a resin layer. In this way, heat is conducted to the metal core through the ceramic layer, which has a sufficiently higher thermal conductivity than resin, so that a large heat dissipation effect can be obtained. However, such a substrate has the following drawbacks.

The first problem is that the ceramic layer obtained by thermal spraying has pores, and the dielectric strength of the insulating layer is insufficient. That is, the withstand voltage of the ceramic insulating stone is poor, and moreover, there is a conductive metal underneath. The second problem is the adhesion between the ceramic layer and the metal core. When ceramic is thermally sprayed onto metal, its adhesion and bonding is due to the so-called anchor effect, in which the molten ceramic powder hits the rough metal surface at high speed. Therefore, chemical bonding strength cannot be obtained,
Furthermore, since metals and ceramics have different coefficients of thermal expansion, it is difficult to obtain adhesion that can withstand thermal shock. To address these drawbacks, methods such as infiltrating the ceramic layer with resin to seal the pores after ceramic thermal spraying have been considered, but the method is not sufficiently effective and the process is complicated. .

The present invention improves these drawbacks and provides a method for manufacturing a metal core substrate with excellent heat dissipation properties.

(Means for Solving the Problems) That is, the present invention sprays ceramic onto a piece m1 of metal foil to form a ceramic insulating layer, and mixes the ceramic layer and the metal plate serving as the core of the substrate with metal powder. It is characterized by being integrated by hot pressure molding via an adhesive layer.

As for the metal foil used in the present invention, copper foil, which is normally used for printed circuit boards, is most suitable in terms of cost and performance, but aluminum foil, zinc foil, stainless steel foil, nickel foil, silver foil, gold foil, or any of these may also be used. Laminated foil or alloy foil can be used.

Further, as the ceramic, alumina is most suitable due to its electrical insulation properties, thermal conductivity, ease of thermal spraying, etc., but spinel, mullite, beryllia, zirconia, etc., which have electrical insulation properties, can also be used. The thickness of this ceramic layer is preferably 30 μm or more and 500 μm or less.

This is because if the thickness is less than 30 μm, the sprayed layer tends to be non-uniform and the electrical insulation and withstand voltage properties are insufficient, while if it is greater than 500 μm, the cost increases and defects such as cracks are likely to occur in the sprayed layer.

As the thermal spraying method, gas spraying, plasma spraying, water plasma spraying, reduced pressure plasma spraying, etc. can be applied.

As the adhesive for integrating the ceramic sprayed layer and the core metal plate, epoxy resin, polyimide resin, unsaturated polyester resin, urethane NT resin, etc. can be used.

As the metal powder mixed into the adhesive, aluminum is suitable because it has good thermal conductivity and is advantageous in terms of cost, but other materials such as copper, iron, nickel, and 4270I can also be used.

Further, the metal plate serving as the core material may be made of aluminum, 4270I, copper, iron, stainless steel, nickel, or the like.

(Function) In the present invention, instead of spraying ceramic directly onto the core metal plate as in conventional thermal sprayed substrates, the metal foil on which the ceramic sprayed layer is formed and the core metal plate are mixed with metal powder. Since it is bonded using adhesive, strong adhesion and high thermal conductivity can be obtained. The strong adhesion is due to the fact that the surface of the ceramic sprayed layer is rough and the adhesion surface is large due to the presence of pores. Further, the resin in the adhesive penetrates into the pores in the ceramic layer and fills the pores, thereby preventing deterioration of insulation properties and voltage resistance when moisture is absorbed. Furthermore, in conventional metal core substrates, the adhesive layer or insulating layer is made of a single resin with extremely poor thermal conductivity, or a resin containing glass fiber, Kevlar fiber, silica, alumina, etc. In either case, the problem was that the adhesive layer or the insulating layer had poor heat dissipation properties. However, in the present invention, by mixing metal powder with excellent thermal conductivity into the adhesive, it was possible to significantly improve the heat dissipation properties of the adhesive layer, which had been a problem in the past. As a result, we were able to obtain a board with extremely good heat dissipation properties that can quickly transfer the high-density heat generated from the electronic components on the board's surface to the metal plate that forms the core of the board. Further, since the particle size of the metal powder is sufficiently larger than the pores of the ceramic layer, there is no deterioration of the insulation properties and sub-voltage properties due to the metal powder penetrating into the pores of the ceramic layer. Furthermore, since a metal foil layer is formed on the surface of the substrate, a circuit can be easily formed by etching or the like.

(Example) An embodiment of the present invention will be described below with reference to FIG.

Alumina was thermally sprayed onto one side of a copper foil 1 having a thickness of 35 μm using a plasma spraying device to form a sprayed alumina layer 2 having a thickness of approximately 100 μm. Then, an adhesive 3 made by adding 200 parts by weight of aluminum powder to an epoxy resin is applied to this alumina layer 2, and the adhesive 3 is placed on an aluminum plate 4 that will serve as the core of the substrate, and then hot-pressed using a press. By molding and curing the adhesive, a metal core copper foil laminate having the structure shown in FIG. 1 was obtained. Furthermore, a pattern was formed on the surface copper foil layer by a conventional method such as etching.

The metal core insulating substrate thus obtained had excellent interlayer adhesion and therefore good thermal shock resistance, and also had an extremely excellent heat dissipation effect.

(Effects of the Invention) As described above, according to the method of the present invention, a metal core insulating substrate with excellent adhesion between the metal foil layer, ceramic layer, and metal plate layer and excellent heat dissipation can be easily manufactured. It can be obtained through a process and at a low cost. This allows components to be mounted on the board at a higher density, and has an extremely large effect on the miniaturization of electronic components.

[Brief explanation of the drawing]

Figure 1 is an explanation of the cross-sectional schematic symbols of a metal core copper-clad laminate 1...Copper foil 2...Alumina sprayed layer 3...Adhesive layer mixed with aluminum powder 4...Aluminum plate agent Patent attorney Professor Akira Hirose, “゛

Claims (1)

[Claims] 1. Ceramic is sprayed on one side of metal foil to form a ceramic sprayed layer, and an adhesive mixed with metal powder is interposed between the ceramic sprayed layer and the metal plate that serves as the core of the substrate, and these are formed by hot pressure forming. Method for manufacturing a metal core insulating substrate characterized by integration 2. The method for manufacturing a metal core insulating substrate according to claim 1, wherein the metal foil is a copper foil. 3. 2. The method of manufacturing a metal core insulating substrate according to claim 1, wherein the ceramic contains alumina as a main component. 4. The method of manufacturing a metal core insulating substrate according to claim 1, wherein the adhesive contains an epoxy resin as a main component. 5. 2. The method of manufacturing a metal core insulating substrate according to claim 1, wherein the metal powder mixed in the adhesive is aluminum.