JPS59110485A - Production of molybdenum composite plate - Google Patents

Abstract

PURPOSE:To produce a molybdenum composite plate having good adhesion by superposing a metallic plate of copper, etc. via a thin coating layer of copper, etc. formed over the entire surface of a molybdenum base plate, and pressing the plates under heating in a nonoxdative atmosphere thereby joining the plates. CONSTITUTION:One or both surfaces covering a molybdenum base plate is washed and degressed and thereafter a thin coating layer of copper, gold, silver or their alloy is formed by plating, vapor deposition, melt-sticking, etc. thereon. The optimum thickness of the thin covering layer is about 0.3-5mum and the layer is preferably heat-treated to diffuse preliminarily the same into the above- mentioned base plate. A metallic plate of copper, nickel, gold or silver or their alloy plate having the same or larger width and length as or than the above- mentioned base plate is superposed over the entire surface of such thin coating layer and the superposed plates are clamped preferably by jigs to maintain the clad material and the thin coating layer in tight contact with each other. The assembly in this state is joined by heating and pressing in a vacuum, inert or reducing atmosphere, whereby the molybdenum composite plate is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a molybdenum substrate composite plate with good adhesion, which is used as a temperature compensating plate for a semiconductor device, in which a plate of another metal or alloy is adhered to one or both sides of a molybdenum plate.

Molybdenum has a coefficient of thermal expansion similar to that of silicon, and is therefore used as a temperature compensating plate to prevent silicon elements of semiconductor components from being damaged due to thermal strain. In order to simplify the bonding process for this molybdenum temperature compensating plate, a clad plate in which copper, silver, or the like is bonded to one or both sides of a molybdenum plate is sometimes used.

However, such a clad plate is prone to problems such as peeling of the cladding surface due to heating when bonding a silicon element to a metal header or repeated heat cycles during use of a semiconductor device. was required.

Sintered materials are generally used as molybdenum plates, but they have weak mechanical properties and high hardness, and the desired high adhesion strength cannot be obtained with the roll crimping method commonly used for manufacturing clad plates. There were no drawbacks.

An object of the present invention is to provide a method for manufacturing a molybdenum-based composite plate with good adhesion, which eliminates the above-mentioned drawbacks.

In order to achieve this object, the present invention forms a thin covering layer of a metal of the same kind or a strong affinity with the metal to be bonded on the entire surface of one or both sides of a molybdenum substrate, and then applies the thin covering layer to the substrate. Metal plates of equal or larger width and length are overlapped on their entire surfaces and bonded by pressure and heating in a vacuum, inert, or reducing atmosphere.

In the present invention, it is necessary to previously form a thin coating layer on the surface of the molybdenum substrate that is to be clad. The material of the thin coating layer is most preferably the same as the metal to be clad with copper, gold, silver, or an alloy thereof, but is not particularly limited as long as it is other than the above-mentioned materials.

As a coating method, general methods such as plating, vapor deposition, welding, etc. can be used after cleaning and degreasing the surface to be coated. The thickness of the thin coating layer is θ, ? The optimum thickness is approximately 5 μm. It is preferable that these coating N layers are diffused into the molybdenum substrate by heat treatment or the like. In the manufacturing method of the present invention, the metal to be clad is a metal plate of copper, nickel, gold, or silver, or a metal plate of copper, nickel, gold, or silver. A metal plate or an alloy plate with the same width and length as the molybdenum substrate is suitable, and a thin coating layer of the molybdenum substrate on which the thin coating layer has been formed may be stacked and subjected to pressure and heat treatment. If a metal plate or an alloy plate having a width and length larger than the molybdenum substrate is stacked on the thin coating layer of the molybdenum substrate on which the thin coating layer is formed, and subjected to pressure and heat treatment, the bond will be better bonded.

In this case, the dimensions of the metal to be clad are width, length,
If the width and length of the co-molybdenum substrate is 1.2 times or more, the adhesive strength will be further increased.

The heat treatment must be carried out in a vacuum, inert or reducing atmosphere, and an oxidizing atmosphere should be avoided.

The bonding strength can be maximized by heat treatment at a temperature slightly lower than the melting point of the metal or alloy to be clad, but the width and length of the molybdenum substrate
When the temperature is more than twice as high, the adhesive strength can be improved up to a temperature range about 300C lower than the melting point than when no thin coating layer is provided.

However, when the dimensions of the metal plate to be clad are the same as those of the molybdenum substrate, the adhesive strength can be improved by maintaining the temperature within a range of 200 C lower than the melting point than when no thin coating layer is provided.

Pressure during heat treatment can be applied by means such as clamping the material in an appropriate jig and tightening it with pressure screws so that the thin coating layer of the molybdenum substrate and the cladding material are in close contact with each other. It is preferable to interpose a mica plate or the like on the contact surface with the material to prevent sagging.

Cladding material may be attached to the molybdenum substrate on one side or both sides depending on the application, and the materials on both sides of the substrate may be different, or two or more molybdenum substrates may be attached in the middle. It is also possible to manufacture composite plates in which multiple layers are stacked together with cladding materials in between.

Examples will be described below.

Example/Length θmm, width 11Qmm, and length 3somz
Width 3Q mm.

An oxygen-free copper plate with a thickness of /rnm is immersed in an organic solvent,
- Ultrasonic cleaning and surface degreasing. On the other hand, length 3s
o rum, width 3Q mm, thickness/thickness of sintered molybdenum> After degreasing the surface of the plate in the same way, copper plating with a thickness of approximately 1/μm was applied to both surfaces, and the plate was plated for 70 minutes in an inert atmosphere.
Heat at 0C for 2 hours to diffuse copper into molybdenum, then apply the degreased copper plate on both sides of the molybdenum plate in a clean environment, and if the copper plate is larger than the molybdenum plate, the copper plate will protrude around the molybdenum plate. The two plates are overlapped on their entire surfaces, and a mica plate is placed on the outermost layer and set in a pressure jig to press the stacked plates together. The stacked plates together with the pressure jig were placed on a boat and charged into a furnace, heat treated in a hydrogen atmosphere of 1000 U for 2 hours, then cooled in the furnace in an inert atmosphere, and then taken out. A sample with a length of Q m, m and a width of approximately 3 mm was cut from the center of the composite plate obtained, and both ends of the sample were held in a vise and a chuck in the thickness direction at intervals of 30 mm, and the chuck was held at qθ°. Turn clockwise, return to original position, then turn counterclockwise 9 degrees and return to original position. Counting the torsion test as 7 times, the number of times until a crank occurs in the sample is expressed as the value of sample/θ. The quality of adhesion was investigated.

Using the same materials as in Example λ~Left Example/, only the temperature at which the clad material was brought into contact with the molybdenum plate and heated under pressure was 900 g3.
A torsion test was conducted in the same manner as in Example except that the temperature was changed to 0, goo, and 73OC.

Example Length: 11, to: width: θ mm, length: 3:0:0, width:: 3
Rmm.

A silver plate containing 5% by weight of copper with a thickness of /tnm was degreased and cleaned, while a sintered molybdenum plate with the same dimensions as in Example / was prepared, and the same treatment was applied to the molybdenum plate. The degreased copper-containing silver plate was brought into contact with both sides in the same manner as in Example/1, and heat-treated in a hydrogen atmosphere of gooC (common phase line gqo C) for 2 hours, and then cooled in a furnace in an inert atmosphere. A sample was cut out from the composite plate and subjected to a torsion test in the same manner as in Example.

Comparative Example The same oxygen-free copper plate as Example/ was degreased and cleaned, and
The same sintered molybdenum plate was degreased, but the degreased oxygen-free copper plate was brought into pressure contact with both surfaces without applying a thin surface coating layer, and treated in a hydrogen atmosphere at 1000 C for 2 hours, and then A sample was cut out from the composite plate obtained by cooling in a furnace in an inert atmosphere and subjected to a torsion test in the same manner as in Example.

The test results of the above Examples/--B and Comparative Examples are summarized in Table 1.

Chapter / Table

Claims (1)

[Claims] (1) A thin coating layer of copper, gold, silver, or an alloy thereof is formed on one or both sides of a molybdenum substrate, and the thin coating layer is coated with copper, nickel, or the like having a width and length equal to or greater than that of the molybdenum substrate. A method for producing a molybdenum-based composite plate, which comprises stacking gold and silver metal plates or alloy plates thereof over the entire surface and joining them by heating and pressing in a vacuum, inert or reducing atmosphere.