Patent GB-870503-A (GB)
Title: Electrical device
IPC: H01L35/00
Filed: 1957-12-13
Abstract: 870,503. Semi-conductor devices. MINNESOTA MINING & MANUFACTURING CO. Dec. 13, 1957 [Dec. 31, 1956], No. 38867/57. Class 37. A semi-conductor device is cooled by mounting one junction of a thermocouple in good heat-conducting relationship with the device and the other junction at a point remote from the device and passing a current through the couple in such a direction as to abstract heat from the semiconductor device at the first junction and to dissipate it to cooling means at the other junction. In one embodiment (Fig. 1) the collector zone 14 of a germanium or silicon junction transistor 11 mounted in a metal casing 19, 20 filled with a heat-conducting potting compound is cooled by passing current through a thermocouple comprising elements 22, 23, a coupling-member 25, the casing 19 and finned cooling member 26. The mixtures of lead sulphide and selenide, or selenide and telluride, containing more than the stoichiometric proportion of lead, and alloys of lead and tellurium containing more than the stoichiometric proportion of tellurium doped with certain so-called promoter impurities described in Specifications 766,999, 806,640, and 814,594 are suitable for the elements 22, 23. For the direction of current flow shown the element 22 should be doped to have P-type conductivity and 23 doped to have N-type conductivity. In this arrangement the contact 21 on the metal casing forms the collector contact as well as forming part of the cooling circuit. In another embodiment, Fig. 3, suitable for mounting on a chassis, a junction transistor with a ring base contact 40 is mounted with its collector zone 14b in direct contact with the base of a metal container, comprising a threaded hollow boss 41, in which is mounted an N-type semiconductor element 23b, and internally and externally finned member 48. In a further embodiment (Fig. 4) a transistor 12c is mounted in a metal cup 25c in a housing 19c, 20c. The thermoelectric cooling apparatus comprises a ring 24c of P-type material and a block 23c of N-type material. The Fig. 2 arrangement comprises a junction diode 31 mounted on the base 20a of a metal casing and thermoelectric elements 23a and 24a of N and P-type material respectively mounted on semi-circular plates 26a, 32. The casing is filled with insulating material 30a. In the above embodiments the current producing the cooling effect does not pass through the semi-conductor body. An arrangement in which the operating current of a device is also used to cool the device is shown in Fig. 6. A junction diode 31e comprising an N- type zone 12e and P-type zone 14e is mounted between and in substantially ohmic contact with P-type thermoelectric element 24e connected to the base of a cup-like housing and an N-type thermoelectric element 23e connected to a cover 20e insulated from the housing proper by a sealing ring 49e. An electroformed point contact diode cooled in similar manner comprises an N-type germanium body 12d (Fig. 5) mounted on a terminal 26d extending through a wall of a sealed glass envelope 19d via a body of P-type thermo-electric material 24d, and a tungsten point contact 16d mounted directly on a similar terminal stub 18d.