FLAT TYPE PRESSURE WELDING STRUCTURE OF SEMICONDUCTOR DEVICE

PROBLEM TO BE SOLVED: To prevent a heat sink which is to be welded in an SI thyristor by pressure from holding an edge protection member, i.e., the positioning member of the heat sink between the SI thyristor. SOLUTION: The structure of a flat type pressure welding of a semiconductor comprises a circular thin plate type semiconductor device 10 and a protection member 23 which covers the edge of the semiconductor device. The protection member carries out the positioning of a heat sink to be welded on the flat plane of the semiconductor device by pressure. The protection member comprises an extendable ring member having a cross section of approximately U-shape, which has a side wall portion facing the side edge face of the semiconductor device and an upper side portion and an under side portion 23c each facing plain faces of the semiconductor device made one body with the side wall portion. The inner periphery of the above upper portion is circular in the plain view and has a plurality of notches and narrow portions 23b. Thus, the difference between the diameters of the heat radiation plate and the inner periphery of the upper side portion is absorbed by the deformation of notches so that the above holding is prevented.