PURPOSE: To obtain excellent air tightness and junction property by junction of iron family thin metal plates having a hole part provided corresponding to the through hole of cooling metal and the window provided corresponding to a protrusion, and junction of a cylindrical glass sealing metal to such hole and by sealing them with glass.

CONSTITUTION: A protrusion 14a for mounting a power transistor etc. is provided at the center of a flat heat dissipating metal 14, while four through holes 14b at the periphery thereof to be used as a base. At the center of iron family metal plate 5, windows 5a for loosely engaging with the protrusion 14a and holes 5b respectively corresponding to four through holes 14b of heat dissipating metal 14 are formed. Cylindrical glass sealing metals 8 having different upper and lower aperture diameters are connected to the holes 5b of iron family metal plate 5. Moreover, an electrical input/output terminal 2 is sealed by glass 13 at the center of cylindrical part. A prescribed space is reserved between the heat dissipating metal plate 14 and the glass sealing metal 8. The hatched part C plays a roll of a buffer which eases a thermal stress.