To secure a terminal case on a cooling base and to prevent resin scraps from being generated when the terminal case is fixed by screw on the cooling base by a method wherein a male screw is screwed in the cooling base to a female screw buried in the terminal case.

A metallic female screw 4 is buried in a terminal case 1 made of a resin and the case 1 is secured on the base 2 by a male screw 3 through a through hole 6 formed in the base 2. The base 2 is one of a structure wherein a circuit board, such as an aluminum nitride board or a direct bonding copper board, having a patterned conductive film, is secured on an oxygen-free copper plate, which is a metal plate, with a solder. Of cause, the base 2 is good in heat conductivity and electrical insulation properties. A semiconductor chip or the like is secured on the patterned conductive film. Thereby, the need to fix the chip on a resin while a screw thread is made is eliminated and the case 1 can be fixed by screw on the base 2 without generating resin scraps.