JPH01157589A - Manufacture of metal base substrate - Google Patents

Abstract

PURPOSE:To assure the formation of a micro-circuit and form a metal substrate with high reliability of connection by forming a ceramic spray coating layer on the surface of a plate of an alloy such as an invar alloy or a 42 alloy, and applying a thermosetting resin on the resulted layer and impregnating the layer, and curing the resin, and the thereafter polishing the surface of the resulted layer. CONSTITUTION:A metal plate 1 comprises a 42 alloy sheet of 1mm thickness for example, one surface of which is roughened by blushing. The roughened surface is applied with spray coating of alumina by a plasma spray coating machine to form a ceramic spray coating layer 2. Then, the surface of the ceramic spray coating layer is coated and impregnated with a solution made by diluting uncured epoxy resin in a solvent. After the plate is left at a room temperature, the plate is put into a heating oven for removal of the solvent and curing of the resin. Then, the resulted surface is polished by a rotary disk type polishing machine. Hereby, the epoxy rein layer on the surface is removed and the surface is smoothed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a metal base substrate with excellent thermal conductivity and heat dissipation.

(Prior Art and its Problems) Conventionally, paper-based phenol resin laminates, glass cloth-based epoxy resin laminates, and the like have been used as printed wiring boards.

However, recently, electronic devices have become more sophisticated and smaller.

How to handle the heat generated by higher density, and the ceramic chips to be mounted.

The challenge is how to make the thermal expansion coefficients of silicon chips and the like similar to those of the substrate, that is, how to reduce the thermal expansion of the substrate and improve connection reliability.

On the other hand, conventional plastic substrates have poor heat dissipation due to their low thermal conductivity, making high-density packaging difficult. For this reason, metal-based substrates, which are based on a metal plate and have an insulating layer formed on the surface thereof, are attracting attention as substrates with excellent thermal conductivity.

By the way, as the metal base substrate, a metal plate made of aluminum or the like with a thin insulating layer made of epoxy resin or the like provided on the surface is mainly used.

However, in the above structure, there is still a resin layer with poor thermal conductivity between the metal plate serving as the base and the conductor layer serving as the circuit, so heat generated from the components is efficiently transferred to the metal plate serving as the base. This makes it difficult to make full use of the high thermal conductivity of the base metal plate.

To deal with this, measures have been considered such as reducing the thickness of the insulating layer as much as possible, or mixing fillers with good thermal conductivity such as ceramics into the resin, but the effects are not sufficient. do not have.

For this reason, it has been considered to use ceramics with good thermal conductivity instead of resin as the insulating layer. That is, this is a method in which an insulating layer is formed by thermally spraying ceramic onto the surface of a base metal plate, such as aluminum.

However, this method does not provide sufficient adhesion due to the poor affinity between the ceramic and metal plate materials and the difference in their thermal expansion coefficients, and furthermore, due to the inherent characteristics of the ceramic sprayed layer, It has pores, which causes problems such as insufficient insulation properties such as moisture resistance and voltage resistance.

Additionally, the surface of the ceramic sprayed layer is rough, so electroless copper plating is required to form a circuit on top of it.

Although it depends on the application of conductive paste and even the thermal spraying of copper powder,
As mentioned above, there is also the problem that it is difficult to form fine circuits because the surface is rough.

(Object of the Invention) In view of the above-mentioned problems, the present invention manufactures a metal-based substrate that has excellent thermal conductivity and heat dissipation, and has a thermal expansion coefficient close to that of ceramic chips, silicon chips, etc. and excellent connection reliability. The purpose is to provide a method.

(Means for Solving the Problems) The present invention provides a plate of Invar alloy (alloy with 36% Ni and 64% Fe) or alloy 42 (alloy with 42% Ni and 58% Fe), or copper on both sides of Invar alloy or 42 alloy. A ceramic sprayed layer was formed by spraying ceramic on the surface of the plate clad with the above, and then an uncured thermosetting resin was applied to the ceramic spraying layer, impregnated, and cured, and further impregnated with the thermosetting resin. The present invention relates to a method for manufacturing a metal base substrate, which comprises polishing the surface of a ceramic sprayed layer.

Invar alloy (Ni36%) is used as the base metal plate.
, 64% Fe alloy (hereinafter referred to as Invar alloy) or 42 alloy (42% Ni, 58% Fe alloy, hereinafter referred to as 42 alloy), or a plate with copper clad on both sides of these plates is used because of the resulting metal. By making the thermal expansion coefficient of the base substrate close to that of the ceramic chip, silicon chip, etc. on which it is mounted, and also close to the thermal expansion coefficient of the ceramic insulating layer formed by thermal spraying, the ceramic insulating layer and the metal This is to improve adhesion to the plate and at the same time prevent warping.

That is, the thermal expansion coefficient of aluminum used in conventional metal base substrates is approximately 15X10-6/'C, and the ceramic chip mounted on the substrate (thermal expansion coefficient: 5
~7 x 10-6/'C), which is significantly different from silicon chips (thermal expansion coefficient: 3.5 x 10-6/'C). In addition, an insulating layer formed by thermal spraying on a base metal plate, for example, an alumina layer with a thermal expansion coefficient of 6 to 7 x 10-6/'
It is also very different from C. For this reason, the reliability of connection with mounted components or the adhesion between the base metal plate and the ceramic sprayed layer is poor, and furthermore, the metal base substrate itself is warped due to the difference in coefficient of thermal expansion.

However, the thermal expansion coefficient of the invar alloy used as a base in the present invention is 2.5X10-6/'C142 alloy is 4.4X10-6/°C, which is much lower than that of conventionally used aluminum. is low. In addition, by appropriately selecting the ratio of the thickness of copper and the low thermal expansion alloy, materials in which copper is clad on both sides of these low thermal expansion alloys can be easily made into metal substrates with a low thermal expansion coefficient equivalent to that of ceramics such as alumina. is obtained. Therefore, by using these materials, the thermal expansion of the substrate can be reduced.

Ceramic is sprayed onto the base metal plate as described above using gas spraying or plasma melting.

Thermal spraying methods used in general ceramic thermal spraying, such as low-pressure plasma spraying, water plasma spraying, and explosive thermal spraying, can be applied.

Additionally, thermal spraying ceramics are easy to spray.

From the viewpoint of electrical properties, alumina or mullite are suitable as an insulating layer, but spinel is also suitable.

Ceramics with good electrical insulation properties, such as aluminum nitride, cordierite, and silicon carbide, can be used.

Next, in the present invention, an uncured thermosetting resin is applied, impregnated, and hardened on the ceramic sprayed layer formed on the surface of the base metal plate by thermal spraying, but this seals the pores present in the ceramic sprayed layer. This is to form holes and to improve the adhesion between the ceramic sprayed layer and the metal plate. A ceramic sprayed layer formed by thermal spraying contains pores as a characteristic of the ceramic layer. Although the amount can be reduced by adjusting spraying conditions such as spraying distance and spraying power, or by performing spraying under reduced pressure, it is difficult to eliminate it completely.

By the way, if the ceramic sprayed layer used as an insulating layer has pores as described above, its electrical properties or withstand voltage properties when moisture is absorbed are insufficient, and it cannot be used as an insulating layer as is.

Therefore, in the present invention, these pores are then sealed with a resin. A preferred method is to apply an uncured thermosetting resin to the surface of the ceramic sprayed layer to impregnate the inside, and then harden the resin.

In addition, by performing such a sealing treatment, the impregnated resin penetrates to the interface between the ceramic sprayed layer and the metal plate and hardens, so the resin also acts as an adhesive, and the ceramic spraying The adhesion between the layer and the metal plate will also be improved.

As the uncured thermosetting resin used in the present invention, polyimide resin is suitable from the viewpoint of heat resistance, and epoxy resin is suitable from the viewpoint of adhesiveness, but phenolic resin, unsaturated polyester resin, melamine resin , fluororesin, vinyl ester resin, etc. can be used.

Next, the surface of the ceramic sprayed layer sealed with resin is polished. This is to smooth the surface and to remove the resin layer used for sealing the surface to expose the ceramic sprayed layer.

In other words, the surface of the ceramic sprayed layer is very rough, and it is difficult to form a circuit on it if it is left as is.Even if a circuit is formed by force plating, etc., it is difficult to form a fine circuit that can support high-density packaging. is not possible.

Further, when a resin is applied to the ceramic sprayed layer to seal the pores, the surface thereof is covered with the resin used for sealing. Therefore, when a circuit is formed on top of the circuit, a resin layer with low thermal conductivity forms immediately below the circuit, making it difficult for the heat generated from the mounted components to be transmitted to the base metal plate, which is a heat sink. In other words, the high thermal conductivity of the ceramic sprayed layer and the base metal plate cannot be fully utilized.

Therefore, by polishing the surface as in the present invention,
The resin layer on the surface is removed and the surface is smoothed. This makes it possible to form fine circuits and to obtain a metal base substrate with excellent heat dissipation properties.

(Explanation of Examples) Next, the present invention will be explained by examples.

FIG. 1 is a sectional view of a metal base substrate obtained according to the present invention, in which a ceramic sprayed layer 2 is provided on a metal plate 1.

In this embodiment, the metal plate 1 is made of a 42 alloy plate with a thickness of 1 mm, and one side 1A is roughened by blasting, and alumina is thermally sprayed on this roughened surface by a plasma spraying machine to give a thickness of 1 mm.
A ceramic sprayed layer 2 made of alumina with a thickness of 50 μm was formed.

Next, the surface of the ceramic sprayed layer obtained as described above is coated with a solution of uncured epoxy resin diluted with a solvent, and after being left at room temperature, it is placed in a heating furnace to remove the solvent and harden the resin. I let it happen.

Next, the surface is polished using a rotating disk type polishing device,
The epoxy resin layer on the surface was removed and smoothed.

The metal base substrate obtained as described above exhibited high heat dissipation properties, and no deterioration in electrical properties due to moisture absorption was observed. Furthermore, the circuit can be formed into fine patterns using electroless copper plating, and since the coefficient of thermal expansion is small, the connection reliability with mounted components is also good.

As mentioned above, the metal base substrate according to the present invention uses a ceramic layer as an insulating layer, whereas conventional metal base substrates use a layer mainly made of resin with low thermal conductivity as an insulating layer. There is.

Therefore, thermal conductivity can be greatly improved compared to conventional metal-based substrates, and thereby heat dissipation performance is also greatly improved.

Furthermore, in conventional metal-based substrates, the insulating layer is a layer mainly made of resin, and the metal plate serving as the base is mainly made of aluminum. For this purpose, a ceramic chip with a thermal expansion coefficient is mounted on the substrate.

Since the coefficient of thermal expansion is significantly different from that of a silicon chip, there was a problem with connection reliability. However, in the present invention, the base metal plate is made of 42 alloy, Invar alloy, which has a small coefficient of thermal expansion, or copper is coated on both sides of these. Since a clad metal plate is used and the insulating layer is a ceramic layer, the thermal expansion coefficient of the resulting metal base substrate is close to that of the mounted components, greatly improving connection reliability.

Furthermore, since the ceramic layer, which is an insulating layer, is formed by thermal spraying directly onto the base metal plate, there is no need for an adhesive layer with low thermal conductivity between the metal plate and the ceramic layer. The high thermal conductivity of the layer can be fully utilized.

In addition, the ceramic sprayed layer obtained by thermal spraying originally has pores as a characteristic of the ceramic layer, and due to its surface roughness, it does not have sufficient voltage resistance or moisture absorption characteristics to be used as an insulating layer. Furthermore, it is difficult to form fine circuits.

However, in the present invention, the pores are sealed by applying an uncured thermosetting resin to the ceramic sprayed layer, impregnating it, and curing it. On the other hand, the impregnated resin reaches the interface between the ceramic spray and the metal plate and also acts as an adhesive. Therefore, the adhesion between the ceramic sprayed layer and the metal plate also increases.

Furthermore, after impregnating and curing the resin, the surface is polished to smooth the surface, and the resin layer on the surface is removed to expose the ceramic layer.

This makes it possible to form fine circuits, and at the same time, since the circuits are formed directly on the ceramic layer, its thermal conductivity can be effectively utilized.

Incidentally, the circuit can be formed on the metal base substrate obtained by the present invention by a method such as applying a conductive paste, electroplating of copper, nickel, etc., or electroless plating method, etc., as is generally practiced. Of course.

(Effects) As described above, the method for manufacturing a metal base substrate according to the present invention involves spraying ceramic onto the surface of an Invar alloy or 42 alloy plate to form a ceramic sprayed layer, and applying an unhardened layer to the ceramic sprayed layer. The metal base substrate is formed by coating, impregnating, and curing a thermosetting resin, and then polishing the surface of the ceramic sprayed layer impregnated with the thermosetting resin, so it has excellent thermal conductivity and heat dissipation. The coefficient of thermal expansion of the substrate is close to that of ceramic chips, silicon chips, etc., making it possible to form fine circuits and providing a metal substrate with excellent connection reliability.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a metal base substrate obtained according to the present invention. 1...Metal plate 2...Ceramic sprayed layer

Claims (3)

[Claims] (1) Invar alloy (36% Ni, 64% Fe alloy)
Alternatively, a ceramic sprayed layer is formed by spraying ceramic on the surface of a plate of 42 alloy (an alloy of 42% Ni and 58% Fe), or a plate in which both sides of an invar alloy or 42 alloy are clad with copper, and then the ceramic sprayed layer is A method for manufacturing a metal base substrate, comprising: coating, impregnating, and curing an uncured thermosetting resin; and polishing the surface of the ceramic sprayed layer impregnated with the thermosetting resin. (2) The method for manufacturing a metal base substrate according to claim 1, wherein the ceramic has alumina or mullite as a main component. (3) The method for manufacturing a metal base substrate according to claim 1 or 2, wherein the thermosetting resin is a polyimide resin or an epoxy resin.