JPH0435052A - Manufacture of circuit board - Google Patents

Abstract

PURPOSE:To manufacture a circuit board excellent in workability and having high size accuracy by means of a simple method by providing a recessed part in the same shape with a copper plate to become the circuit in advance on a ceramic board to become the circuit board and directly connecting the copper plate to the recessed part. CONSTITUTION:A ceramic circuit board 1 is composed of a laminated copper plate 2 to become a circuit and a ceramic board 3 having a recessed part 4 to be formed into a shape almost the same with the copper plate 2 on the surface by a press process. Then, the depth of the recessed part 4 to be provided on the surface of the ceramic board 3 to constitute the ceramic circuit board 1 requires above 1/5 of the thickness of the laminated copper plate 2 to prevent lowering of positional accuracy due to deviation of the copper plate 2 at the time of heating while being optimal less than 1/2 of the thickness of the copper plate 2 to prevent damage of the ceramic board 3 due to thermal stress at the time of thermal junction.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of manufacturing a circuit board used in a high-power semiconductor device, such as a power transistor module, a thyristor module, or a tie-in module.

(Prior art) Conventionally, circuit boards used in high-power semiconductor modules have generally been made by bonding a metal plate such as a copper plate to a ceramic substrate. In order to shorten the manufacturing process and thereby reduce costs, a copper metal bonding method has come to be used in which a copper circuit board is placed directly on a ceramic substrate and bonded by heating.

In this steel welding method, a copper plate that has been formed into a pattern by press punching or the like and has an oxidized surface is positioned on a ceramic substrate using a positioning jig before being heated. They are removed or heated to 1070° C. together with a positioning jig to generate a Cu-Cu2O eutectic liquid and then bonded.

(Problem to be solved by the invention) However, in the above-mentioned conventional method, a patterned copper plate is placed on a ceramic substrate using a positioning jig, and the positioning jig is removed or heat bonding is performed together with the positioning jig. In this case, it takes time to place the copper plate on the ceramic substrate using the positioning jig, which reduces work efficiency, and if heat bonding is performed together with the positioning jig, the positioning jig Since the tool is also heated to 1070° C., the cost of the positioning jig becomes extremely high.

Furthermore, in order to ensure the dimensional accuracy of the circuit pattern,
Thermal expansion of the copper plate and positioning jig must be taken into consideration during heat bonding, and a certain distance is required between the copper plate and the positioning jig, which has the disadvantage of reducing the dimensional accuracy of the circuit pattern. .

Therefore, the present invention aims to improve the drawbacks of the above-mentioned conventional products, and manufactures a circuit board with excellent workability and high dimensional accuracy using a simple method.

(Means for solving the problem) For this purpose, a concave portion having the same shape as the copper plate serving as the circuit is provided on the ceramic substrate, and the concave portion is bonded by heating.
The depth of this recess is 115 to 1/2 of the thickness of the copper plate.

(Function) With the above configuration, positioning can be performed by placing a steel plate formed into a circuit pattern in a recess on a ceramic substrate, eliminating the need for a positioning jig that was conventionally required for positioning. In this case, workability can be improved.

(Example) This invention will be further explained with reference to embodiments shown in the drawings.

(1) is a ceramic circuit board which is an embodiment of the present invention, and this ceramic circuit board (1) is formed by pressing a laminated copper plate (2) which becomes a circuit and the surface of the copper plate (2). It is composed of a ceramic substrate (3) having four parts (4) formed in approximately the same shape as the one shown in FIG.

The ceramic substrate (3) constituting the ceramic circuit board (1) has a length of 66 mm and a width of 42 mm.
It is made of a 96% alumina green sheet with a thickness of 0.7601 TIITl, and a recess (
In 4), the shape of the copper plate (2) that will become the circuit is made larger than that of the copper plate (2) and the depth of the recess (4) is also larger than that of the copper plate (2) when heated, taking into consideration shrinkage during firing.
) is required to have a thickness of 115 or more than the thickness of the laminated copper plate (2), and to prevent damage to the ceramic substrate (3) due to thermal stress generated during heat bonding, the copper plate ( The optimal thickness is 172 mm or less, which is the thickness of 2).

On the other hand, the laminated copper plate (2) that will become the circuit has a length of 50 mm.
, an oxygen-free copper plate (2') with a radius of 30 mm and a thickness of 0.3 mtn.
It consists of a tough pitch copper plate (2") with a length of 50 mm, a width of 30 mm, and a thickness of 0.07 mm. To make the above laminated copper plate, one side of the tough pitch copper plate (2") is chrome plated, By heating at 1000℃, chromium is diffused into the surface of the tough pitch copper plate (2”),
Further, Evonol treatment is performed at 100℃ to oxidize both sides of the tough pitch steel plate (2''), and then the oxygen-free copper plate (2') and one side of the tough pitch copper plate (2') that has not been subjected to chromium treatment are placed in a nitrogen atmosphere. , heat bonded at 1060° C. and formed into a circuit pattern by press punching or the like.

Since the present invention has the above configuration, the surface of the chromium-treated tough pitch copper plate (2") is placed on the four parts (4) of the ceramic substrate (3). Place it in contact with the
By heating and holding at 70° C. for 5 minutes, joining can be performed without the steel plate (2), which is a circuit pattern, coming off during heating or reducing positional accuracy.

(Effects of the Invention) As described above, by placing a copper plate serving as a circuit in a recess provided on a ceramic substrate and then heat bonding, it is possible to improve the positional accuracy of the circuit board during heat bonding. This has the excellent effect of simplifying the positioning work and reducing costs.

[Brief explanation of the drawing]

FIG. 1 is an overall perspective view of a ceramic circuit board according to an embodiment of the present invention, FIG. 2 is a sectional view taken along line II, and FIG.
FIG. 1...Ceramic circuit board 2...(Laminated) copper plate 2''...Tough pitch steel plate 4...Concave portion 2''...Oxygen-free copper plate 3...Ceramic substrate patent applicant Nippon Spark Plug Co., Ltd. company

Claims (2)

[Claims] (1) A method of manufacturing a circuit board, in which a recess having the same shape as a copper plate, which will become a circuit, is provided in advance in a ceramic plate that will become a circuit board, and the copper plate is directly bonded to the recess. (2) Claim (1) wherein the depth of the recess provided in the circuit board made of ceramic is 1/5 to 1/2 of the thickness of the copper plate.
), the method for manufacturing the circuit board described.