GB886451A - Improvements in or relating to semi-conductors - Google Patents

Abstract

886,451. Semi-conductor devices. BOSCH G.m.b.H., ROBERT. Jan. 25, 1960 [Jan. 28, 1959], No. 2564/60. Class 37. In a semi-conductor device such as a diode or transistor, a semi-conductor body comprising at least one PN junction is soldered, directly or indirectly, on to a carrier of easily solderable metal which is held in a casing of poorly solderable metal having good heat conductivity, primarily by compression between contacting surfaces of carrier and casing, no separate fastening means being used. In the diode shown in Fig. 1, a carrier plate 13 of copper is a force-fit in a blind bore 12 in a casing 10 of aluminium comprising radial cooling ribs 11. To the plate 13 is tin soldered one surface of a nickel plate 16, to the other surface of which is soldered one side of a wafer 17 of N-type germanium which has had a pill of indium alloyed to its other side in vacuo at 530-550‹ C. A copper lead 20 has one end indium coated and soldered to the indium pill. After being washed and tested the device is sealed by an insulating annular disc 26 covered with a moulding composition 27, a few grains 24 of a drying medium, e.g. silica gel, being sealed in the enclosure. The nickel plate 16 may be replaced by a coating of nickel on at least one main surface of the carrier plate 13 ; alternatively, the nickel plate may be thick enough to constitute the carrier plate, in which case it is pressed into the bore 12 by means of a peripheral punch which does not damage the wafer. In the embodiment shown in Fig. 5, the nickel plate holding the germanium wafer 39 is soldered to the end of a blind bore 32 in a copper body 33 around which an aluminium casing 34 with cooling ribs 35 is formed by injection moulding. In addition to the clamping of the casing to the body on cooling, the former is keyed to the latter by an annular groove 40 in the body.