SEMICONDUCTOR RECTIFIER STRUCTURE HAVING SEMICONDUCTOR ELEMENT ASSEMBLY SCREWED INTO PLACE ON SUPPORT BASE

1,011,171. Semi-conductor devices. BROWN, BOVERI & CO. Ltd. March 28, 1963 [March 30, 1962]. No. 12320/63. Heading H1K. In a semi-conductor device in which the semiconductor element is sandwiched between and soldered to two carrier plates having the same coefficient of thermal expansion as that of the semi-conductor element, the plates are forced into thermal and electrical contact with metallic members forming heat conduction and electrical connection elements (and which may have any coefficient of thermal expansion) by at least one screwed connection. Fig. 1 shows one embodiment in which the (molybdenum or tungsten) carrier plates 2, 3 which are soldered to opposite faces of the semi-conductor element 1 are formed with threaded pins 4, 5 of the same material as the plates and screwed into the base contact member 6 and the top contact element 7, the pins, if desired, being pre-tinned and soldered to the base and top contacts after assembly to prevent loosening. The remainder of the assembly comprises a spacing element consisting of a ceramic ring 11 soldered to member 6 and to a cover-plate 8 through an opening in which the connecting wire 10 is soldered via a ring 9. In this embodiment and in the embodiments to be described below, discs 12, 13 consisting e.g. of gold foil, may be positioned between the carrier plates and the base and top contact members to ensure uniform distribution of pressure. Instead of forming the threaded pins 4, 5 integrally with the carrier plates they may be formed separately and be of a different material, e.g. nickel or silver, as described in connection with Figs. 2a and 2b (not shown). In a modification, the lower carrier plate 2 (Fig. 3) which is not provided with a threaded pin is pressed against base member 6 by means of a pressure ring 14 constrained by at least three screws 15. In a further arrangement (Fig. 4) neither carrier plate is formed with threaded pins and the required pressure is effected by means of a resilient cover-plate 16 clamped to the base 6 by means of at least three screws 17 provided with insulating bushes 19 retained between pressure distribution rings 20, 21 to avoid subjecting the ceramic spacing ring 18 to tensile stress. Fig. 5 shows an arrangement in which the sandwich of semi-conductor element 1 and the carrier plates 2, 3 is formed with a central aperture through which a screw 31, the head of which is seated on a shoulder formed in a central aperture in contact element 25 engages the base mem