SEALING STRUCTURE OF MULTI-CHIP MODULE

PROBLEM TO BE SOLVED: To provide a multi-chip module sealing structure which is superior in cooling performance and sealing reliability. SOLUTION: A semiconductor device 2 is mounted on a wiring board 1, the top surface of the wiring board 1 is fixed by soldering 8 to the undersurfaces of first frames 5 of which each thermal expansion coefficient conforms to that of the wiring board 1. Each of the upper parts of the first frames 5 is extended outside of the edges of the wiring board 1, the lower part of the air-cooling heat sink 7 and the top surfaces of the second frames 10 are fastened by bolts 9 through the intermediary of an O-ring between a large air-cooling heat sink 7 covering the frames 5 sufficiently and the first frames 5, and through the intermediary of plastic pieces 6 between the inner middle stages of second frames 10 of which each thermal expansion coefficient conforms to that of the air-cooling heat sink 7 and the outer middle stage of the first frames 5.