JPH0654833B2 - Method for manufacturing insulating substrate - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a metal core insulating substrate having excellent heat conductivity and heat resistance.

(Prior Art) Conventionally, as a printed wiring board, a phenol resin laminated board,
Epoxy resin laminates have been widely used. However, recently, with higher performance and smaller size of electronic devices, high density mounting of components has been desired, and how to deal with high density generation of heat generated thereby has become a problem.

On the other hand, the conventional organic substrate has poor heat conductivity, lacks heat dissipation, and has poor heat resistance. Therefore, high-density mounting is difficult. Therefore, as a substrate having excellent thermal conductivity, a ceramic substrate made of alumina, aluminum nitride, silicon carbide, or the like, or a metal core substrate having a metal plate as a core and an insulating layer formed on the surface of the metal substrate has attracted attention. In particular, metal core substrates are cheaper than ceramic substrates, have excellent workability, and are made of metal such as aluminum, which has a high thermal conductivity, as the core, and are attracting attention because of their large heat dissipation properties. It has come to be used for. Research and development of performance improvement for that purpose are also actively carried out.

(Problems to be Solved by the Invention) In a general metal core substrate, an insulating layer of a glass / epoxy resin layer having a thickness of 50 to 100 μ is provided on the surface of a metal plate such as aluminum, and a circuit is further formed thereon. It is made by sticking copper foil. That is, the resin layer having poor thermal conductivity is in direct contact with the circuit. Therefore, the heat generated in the circuit is transferred to the metal plate which is the core through the resin layer having poor thermal conductivity. Therefore, 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, there is an idea to provide a ceramic insulating layer by spraying a ceramic such as alumina on the surface of a metal plate as a core without using a resin layer. By doing so, heat conduction is transmitted to the metal core through the ceramic layer having a sufficiently higher thermal conductivity than that of resin, so that a large heat dissipation effect can be obtained. However, such a substrate has the following drawbacks.

First, the ceramic layer obtained by thermal spraying has pores, and the withstand voltage characteristic of the insulating layer is insufficient. That is, this is because the withstand voltage of the ceramic insulating layer is inferior and the underlying layer is a conductive metal. The second is the problem of adhesion between the ceramic layer and the metal core. When the ceramic is sprayed on the metal, the adhesion and the bonding are due to the so-called anchor effect, in which the molten powder of the ceramic sticks to the rough surface of the metal at a high speed. Therefore, no chemical bond is obtained,
Further, since the coefficients of thermal expansion of metals and ceramics are different, it is difficult to obtain an adhesion force capable of withstanding thermal shock.

Regarding these drawbacks, a method of sealing the pores by infiltrating a resin into the ceramic layer after spraying the ceramic has been considered, but a sufficient effect cannot be obtained, and the process becomes complicated. Will end up.

The present invention has improved these drawbacks, has excellent heat dissipation,
Moreover, the present invention provides a method of manufacturing a metal core substrate having excellent characteristics and mass productivity.

(Means for Solving Problems) That is, according to the present invention, a metal plate A is sprayed with a ceramic to form an insulating layer, the ceramic layer and the metal plate B are integrated via an adhesive layer, and then the metal plate is formed. It is characterized in that A is separated from the ceramic layer.

In the present invention, as the metal plate A on which the ceramic is sprayed, a metal plate made of iron, copper, aluminum, nickel, stainless steel or the like can be used.

Alumina is most suitable as the ceramic because of its electrical insulation, thermal conductivity, and ease of thermal spraying, but spinel, mullite, beryllia, zirconia, etc., which have electrical insulation, may be used. The thickness of this ceramic layer is preferably in the range of 30 μ or more and 500 μ or less. This is because if the thickness is less than 30 μm, the sprayed layer tends to be non-uniform, the heat dissipation effect is not sufficient, and if it is 500 μm or more, the cost increases and defects such as cracks are likely to occur in the sprayed layer.

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

As an adhesive layer for integrating the ceramic sprayed layer and the metal plate 2 serving as a core, glass fiber or Kevlar fiber with an epoxy resin or an epoxy resin is used from the viewpoint of ensuring a uniform thickness of the adhesive layer and reliability of adhesive strength. It is desirable to use a prepreg impregnated with a polyimide resin and perform thermocompression molding for bonding. By doing so, it is possible to integrate the ceramic layer and the core metal plate with the adhesive layer having excellent electric insulation and having a uniform thickness. It is possible to obtain reliable products such as withstanding voltage.

The adhesion between the ceramic sprayed layer and the adhesive layer is extremely strong because the surface of the ceramic sprayed layer is rough and the pores are present so that the adhesion area is large.
On the other hand, since the adhesion between the ceramic sprayed layer and the metal plate A is low, it is possible to easily peel the metal plate A from the ceramic sprayed layer after the bonding work. Further, in order to facilitate the peeling, it is possible to perform no roughening treatment such as sandblasting before the thermal spraying of the metal plate A, or to perform it very lightly, or to perform a releasing treatment.

Since the surface of the ceramic layer on the side where the metal plate A is peeled off is a surface on which the surface state of the metal plate A is transferred, the surface is excellent in smoothness and a conductor circuit can be directly formed by plating, printing, or the like. It is possible.

The core metal plate B may be made of aluminum, iron, copper, stainless steel, nickel, or the like.

(Operation) In the present invention, instead of directly spraying the ceramic to the core metal plate as in the conventional sprayed substrate, by bonding the ceramic sprayed layer and the core metal plate using the adhesive layer, It is possible to obtain strong adhesion. Further, the surface of the ceramic sprayed layer is rough, and since the pores are present, the adhesion area is large, and the adhesive layer penetrates into the inside of the sprayed layer, so that the adhesion is further enhanced.

Further, the surface of the metal core substrate thus obtained is a transfer of the surface of the metal plate A on which the ceramic is sprayed in the first step, so that it is much smoother than the sprayed substrate obtained by the conventional method. It will be a face. Therefore, it is possible to form a fine conductor circuit pattern as it is by plating or a printing method.

The metal core substrate thus obtained is excellent in heat dissipation and heat resistance because the ceramic layer under the conductor circuit is excellent in heat conductivity.

(Example) Alumina sprayed layer 2 having a thickness of about 100 μ was formed on one surface of a stainless steel plate 1 having a thickness of 2 mm by spraying alumina using a plasma spraying device. Next, as shown in FIG. 1, the alumina sprayed layer 2 of the stainless steel plate 1 on which the alumina sprayed layer 2 is formed.
An epoxy resin-impregnated glass cloth prepreg 3 (thickness: 50 μ at the time of molding) was placed between the aluminum plate 4 having a thickness of 1 mm and the aluminum plate 4 and was thermocompressed to be integrated.

After the resin was cured, it was cooled and the stainless steel plate 1 was peeled off from the alumina sprayed layer 2. Since the alumina sprayed layer 2 is firmly adhered to the aluminum plate 4 with an epoxy resin, the stainless steel plate 1 can be easily peeled off by prying it with a steel blade.

The substrate thus obtained is smooth because the surface of the alumina sprayed layer 2 transfers the surface condition of the stainless steel plate 1 on which alumina was first sprayed, as shown in FIG. The circuit could be formed by electrolytic copper plating → etching. Further, unlike the conventional metal core substrate, the area directly under the circuit is the alumina thermal sprayed layer 2 having excellent thermal conductivity, so that its heat dissipation property is very excellent. Further, since the alumina sprayed layer 2 is firmly bonded to the aluminum plate 4 serving as the core by the glass epoxy resin adhesive layer 5, the glass epoxy layer has excellent heat resistance and thermal shock resistance, and has an intermediate withstand voltage. Because of the existence of
The withstand voltage characteristics were also good.

(Effects of the Invention) According to the method of the present invention, it is possible to mass-produce a highly reliable metal core substrate having excellent heat dissipation and heat resistance at a low cost in a simple process. As a result, high density mounting of components on a substrate becomes possible, and the effect of miniaturizing electronic components is extremely large.

[Brief description of drawings]

FIG. 1 is a laminated constitution diagram when an adhesive layer is formed according to an embodiment of the present invention,
FIG. 2 is a schematic sectional view of the obtained metal core insulating substrate. Explanation of symbols 1 ... Stainless steel plate, 2 ... Alumina sprayed layer 3 ... Glass / epoxy resin prepreg, 4 ... Aluminum plate 5 ... Glass / epoxy resin adhesive layer

Claims (4)

[Claims] 1. A method of manufacturing an insulating substrate in which an insulating layer made of ceramic is provided on the surface of a metal plate, comprising: a. A first step of spraying a ceramic onto the metal plate A to form a ceramic layer, b. A second step of interposing an adhesive layer between the ceramic layer and the metal plate B serving as the core of the substrate and integrating them, c. 3. A method for manufacturing an insulating substrate, comprising: a third step of peeling the metal plate A on which the ceramic is sprayed in the first step from the ceramic layer. 2. The method for producing an insulating substrate according to claim 1, wherein the electrically insulating ceramic contains alumina as a main component. 3. The method for producing an insulating substrate according to claim 1, wherein the adhesive layer is glass fiber or Kevlar fiber impregnated with an epoxy resin. 4. The method for producing an insulating substrate according to claim 1, wherein the adhesive layer is glass fiber or Kepler fiber impregnated with a polyimide resin.