JP2001118960A - Carbon-based metal composite material board with electric insulating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electronic board device which is high in thermal conductivity by a method wherein an electric insulating film of ceramic or plastic is formed on a carbon-based metal composite material board, and an electronic circuit is provided to the electric insulating film, where the carbon-based metal composite material board is nearly equal to metal in thermal condcutivity and electrically conductive and whose thermal expansion coefficient is as small as that of a ceramic and Young's modulus is small, a ceramic insulating board is bonded to the carbon-based metal composite material board with metal brazing material to serve as a board device in a usual method, but the above board device is low in thermal condcutivity due to the fact that the ceramic insulating board and metal brazing material are high in thermal resistance. SOLUTION: An electric insulating film of ceramic or plastic is formed direct on a carbon-based metal composite material board taking advantage of the fact that Young's modulus of the composite material board is low. An electronic circuit is provided on the electric insulating film, by which an electronic board device of high thermal conductivity can be manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a product obtained by adding an electrical insulating film to a material called a carbon-based metal composite material in which a carbon component accounts for a majority in volume fraction and the remainder is metal. This product is mainly used as a substrate for a semiconductor package or an electronic circuit including the same.

[0002]

2. Description of the Related Art High-performance, high-output electronic devices generate a large amount of heat. In order to efficiently remove the heat, a material having good heat conduction and a small coefficient of thermal expansion is required. I have. Most of the heat generated from an electronic circuit including a semiconductor element, a resistor, a transformer, a capacitor, and wiring is radiated to the atmosphere or a cooling liquid by a cooling device via an electric insulating substrate and a base substrate.
Aluminum nitride ceramics, which have high thermal conductivity, are frequently used as the material of the electrically insulating substrate, and the base substrate material is made of a metal material of aluminum or copper or a sintered metal of silicon carbide or tungsten to reduce the coefficient of thermal expansion by impregnating the metal. In many cases, a composite material is used.

[0003] The electrically insulating substrate and the base substrate are usually soldered.
(Soft solder) or hard brazing material. In this joint,
Usually, high-temperature solder having a melting point of 220 ° C. to 300 ° C. or gold tin or silver brazing is used.

This structure has the following problems from the viewpoint of thermal resistance. The required thickness of the electrically insulating substrate is about 0.1 mm from the standpoint of the electric withstand voltage, but an aluminum nitride substrate having a thickness of 0.635 mm is usually used to prevent breakage in the manufacturing process. Therefore, the thermal resistance inside the substrate must be unnecessarily large. The thickness of the brazing material on the electrical insulating substrate and the base material is usually 0.05 mm or more to provide a function of buffering thermal stress caused by a difference in thermal expansion coefficient between the two substrates. Since the thermal conductivity of the brazing material such as solder is low, the thermal resistance of this layer is large.

[0005]

The carbon-based metal composite material has a good thermal conductivity and a small coefficient of thermal expansion, and has good characteristics as a semiconductor substrate material. Electric insulation cannot be installed. For this reason, this substrate is used as a substitute for a substrate made of aluminum, copper, or an alloy metal thereof, which is a conventional base substrate material. Specifically, the structure is such that an insulating substrate made of ceramics is joined with a brazing material on a substrate made of a carbon-based metal composite material, or a plastic film is laid. For this reason, the characteristics that the carbon-based metal composite material has a small coefficient of thermal expansion and a small Young's modulus are not fully utilized.

In addition, since a solder having a low thermal conductivity is used, the point that the thermal resistance between the electric insulating surface and the base substrate becomes large, and the thickness of the ceramic substrate is larger than a functionally necessary thickness due to restrictions on processing operations. In particular, when an inexpensive alumina substrate is used, the thermal resistance of the ceramic insulating substrate increases. Therefore, the good heat conduction of the carbon-based metal composite material is not utilized as a substrate device.

Conventionally, attempts have been made to directly lay a plastic film or a ceramic film in order to reduce the thermal resistance between the base substrate and the insulating substrate. In the case of a plastic film, the thermal resistance of the plastic film is not more than one-tenth of the ceramic film, so that the thermal resistance does not decrease. In the case of a ceramic film, if the base substrate is made of a metal such as aluminum or copper, the coefficient of thermal expansion will be large, making it impossible to form a film. In addition, a composite material in which silicon carbide or tungsten sintered body with a low coefficient of thermal expansion is impregnated with the metal However, it was difficult to form a solid ceramic film directly on the substrate. The reason is that the elastic modulus of the composite material substrate in which silicon carbide and tungsten sintered bodies are impregnated with a metal has a large elastic modulus.If there is a slight difference in the coefficient of thermal expansion between the ceramic film and the composite material substrate, a large stress is applied to the film. This is due to the occurrence of the problem.

According to the present invention, there is provided a product in which an electrically insulating film is directly laid on a carbon-based metal composite material by removing a solder layer having poor thermal conductivity in order to increase the thermal conductivity from the electrical insulating surface to the base substrate. The purpose is to provide.

[0009]

In order to achieve the above object, a film made of electrically insulating heat-resistant plastic or ceramics is directly laid by utilizing the low Young's modulus of the carbon-based metal composite material. .

The carbon-based metal composite material is a composite material of carbon and metal having a Young's modulus of 30 GPa or less and a thermal conductivity of 10 GPa or less.
0 W / (mK) or more, the linear expansion coefficient of 5 × 10 ^{- 6} / ℃ least 11 × 10 ^{- 6} / ℃ following materials is desirable. The Young's modulus of a carbon-based metal composite is the Young's modulus of a composite substrate whose thermal expansion coefficient is reduced by impregnating a conventional base substrate material such as aluminum, copper or silicon carbide, or tungsten with a metal. It is less than 1/10. For this reason,
The stress on the film on the surface of the carbon-based metal composite substrate is small,
Particularly, in the case of a ceramic insulating film, a good film without cracks can be formed.

The plastics for electrical insulation include epoxy, polyurethane, polyester, polyimide, polyaminobismaleimide, bismaleimide, polyetherimide, polyamideimide, and siloxane.
It is not limited to these materials. A plastic that is laid as a film on a substrate made of a carbon-based metal composite material and has no blistering or peeling in a solder immersion test at 246 ° C. or more for 5 seconds.

As ceramics for electrical insulation, alumina, aluminum nitride, silica, silicon nitride, titanium oxide, zirconia or vitreous are used, but are not limited to these materials. An inorganic material that is laid as a film on a carbon-based metal composite material product and that can be used at 300 ° C. or higher where so-called high-temperature solder can be used.

The thickness of the plastic for electrical insulation is 0.5 mm or less because the thermal conductivity of the plastic is low. Desirable thickness is from 0.01 mm to 0.1 mm.

The thickness of the ceramic for electrical insulation is 1 m
m or less. Desirable thickness is 0.01 mm to 0.1 mm.
1 mm.

As a method of forming a plastic film for electrical insulation, there are dipping, spray coating, spin coating, screen printing, electrodeposition, MOCVD, and lamination of a plastic film.

As a method for forming a ceramic film for electrical insulation, there are PVD, CVD, and plasma spraying methods. When a semiconductor chip is mounted, film formation by sputtering, which is a kind of PVD method, is particularly desirable. In plasma spraying, it is necessary to seal the glass with a vitreous glaze after spraying ceramics.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings based on embodiments. The product of the present invention is characterized by comprising a carbon-based metal composite and an electric insulating film. Its basic structure is shown in FIG. In FIG.
1 is a substrate made of a carbon-based metal composite material, 2 is a metal thin film when spraying ceramics, and an adhesive resin when laminating a plastic film. P
This is unnecessary when laying a plastic film using VD, CVD, or varnish. 3 is a ceramic or plastic film. Reference numeral 4 denotes an electric circuit, which is usually made of copper. Reference numeral 5 denotes an electronic component such as a semiconductor element, a resistor, and a capacitor.

[0018]

EXAMPLES The present invention will be further described below with reference to examples, but the technical scope of the present invention is not limited to these examples.

Example 1 A carbon fiber unidirectionally arrayed carbon composite material having a void of 8% by volume was impregnated with molten copper at a high pressure. A substrate having a thickness of 3 mm and a square of 30 mm is adjusted in the thickness direction. On the substrate, a metal film having a thickness of 10 μm mainly composed of molybdenum and chromium is laid by plasma spraying. White alumina having an average particle diameter of 1 μm and a purity of 99.6% or more is plasma-sprayed on the metal film to prepare a ceramic film having a total thickness of 0.1 mm together with the metal film. Since this film has pinholes, apply a thin glass frit to 900 ° C.
Baking. 10 μm thick aluminum foil on this film,
Further, a copper foil having a thickness of 0.3 mm is stacked thereon and subjected to a treatment at 2 MPa and 650 ° C. for 30 minutes by hot pressing to obtain a substrate with a copper plate.

In order to confirm the electrical insulation of the ceramic film, a potential difference of 500 V was applied between the carbon-based metal composite substrate and the copper plate, and the electrical resistance was measured with an electrical insulation tester.
The resistance was infinite and the electrical insulation of the ceramic film was confirmed.

Example 2 The same carbon-based metal composite substrate as in Example 1 was polished on a 10 mm square, 1 mm thick surface to have an average plane roughness of 0.1 μm. Atmospheric pressure 1 Pa, argon gas and oxygen gas 9/1 on the same substrate using a magnetron sputtering device.
Is flowed at a rate of 10 ml per minute, and an alumina film is applied to a thickness of 0.03 mm at an output of 300 W for 12 hours. At this time, the substrate temperature is 300 ° C.

Scanning the alumina substrate film with a scanning electron microscope 500
Observed at 0x. The membrane was clear and vitreous. No defects such as pinholes could be observed.

In order to confirm the heat resistance of the substrate, a process of heating the substrate to 400 ° C. in the air and then naturally cooling it was repeated five times, and then observed with a scanning electron microscope at a magnification of 5,000. No defects such as pinholes were observed on the film, and heat resistance at 400 ° C. was verified.

Gold was vapor-deposited on the alumina film provided by a magnetron sputtering apparatus, and the electrical insulation between the gold film and the carbon-based metal composite substrate was measured with an electric insulation tester to measure the withstand voltage of the film. As a result, the withstand voltage of this film was 500 V or more and 650 V or more.
It was the following. The specific resistance of the film is 10 ¹² Ω · m
It was actually measured above.

[0025]

The carbon-based metal composite substrate has a small coefficient of thermal expansion similarly to a conventional composite substrate manufactured by impregnating a metal into a powder sintered body of silicon carbide, alumina, tungsten, or the like. And the Young's modulus is one digit lower. By utilizing this characteristic, a ceramic electrical insulating film having good film quality and withstanding thermal cycling could be laid on the carbon-based metal composite substrate.
By disposing an electronic circuit on this insulating film, an electronic substrate device having good thermal conductivity can be easily manufactured.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a basic structure of an electronic substrate device of the present invention.

FIG. 2 is a conceptual diagram of a magnetron sputtering apparatus used in Example 2.

[Explanation of symbols]

1 Carbon-based metal composite substrate 2 Bonding layer, when spraying ceramics, when metal thin film is laminated with plastic film,
Adhesive resin is used. (This is not necessary when a plastic film is laid using PVD, CVD, or varnish.) 3 Electric insulating film (ceramic or plastic film) 4 Electric circuit (usually copper is used) 5 Semiconductor element, resistor Components such as heaters and condensers 6 Chamber 7 Cathode 8 Anode 9 Solenoid coil

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D075 CA17 CA23 DB63 DC21 EB02 4G046 AA00 AB01 4K018 AA02 AA04 AA15 AB07 BB02 DA19 DA50 FA24 FA25 JA14 JA16 JA38 KA32 5F036 AA01 BB08 BD01 BD03 BD11

Claims (4)

[Claims] An alloy in which carbon and a metal are mixed with each other, and a volume ratio of a carbon component is 60% or more, and the balance is aluminum or an alloy thereof, copper or an alloy thereof, silver or an alloy thereof, or an alloy containing one or more kinds of the above metals A product whose surface is partially or entirely covered with an electrically insulating film with a carbon-based metal composite material consisting of 2. The carbon-based metal composite material according to claim 1, having a Young's modulus of 30 GPa or less and a thermal conductivity of 100 W / (m ·
Material with any of the characteristics of ⁶ / ° C. or less ^- K) or more, or linear expansion coefficient is 12 × 10. 3. The product according to claim 1, wherein the electrically insulating film material is made of plastic, the electric insulating film and an electric circuit are laminated in a single layer or a plurality of layers, and the thickness thereof is 0.5 mm or less. 4. The product according to claim 1, wherein the electrically insulating film material is made of ceramics, the electric insulating film and the electric circuit are laminated in a single layer or a plurality of layers, and the thickness thereof is 1 mm or less.