GB1294532A - Improvements in semiconductor devices - Google Patents

Abstract

1294532 Semiconductor devices ALLMANNA SVENSKA ELEKTRISKA AB 23 March 1970 [24 March 1969] 13907/70 Heading H1K A semiconductor device comprises a wafer arranged under pressure between two contacts at least one of which is a heat spreading body of Cu or Cu alloy comprising a plate-like part having a plurality of pins extending from the face opposite to that connected to the wafer, and a pressure plate engaging the ends of the pins to transmit pressure via the pins to the platelike part of the heat spreader which forms part of a hermetically sealed casing for the wafer, the space round the pins forming a duct for a cooling fluid: As shown. Fig. 3, a diode comprising a Si wafer 20 soldered by means of an Al layer (not shown) to a Mo support plate 21 and having an alloyed Au-Sb foil 22 on the opposite side is mounted in a hermetic enclosure comprising a ceramic or porcelain ring 25 and contact plates 26 and 17. The plate 17 forms part of a Cu heat spreader 15 and has projecting pins 16 the ends of which are contacted by a pressure plate 33. The upper housing plate 26 is contacted by a member 28 pressed towards the housing by spring washers 29 supported in a steel dome 31 by an insulator 30 and a pressure adjusting screw 34. The dome 31 and pressure plate 33 are secured to the plate 17 by bolts 32. Pressure plate 33 has a central aperture 38 through which cooling fluid is introduced so that it flows outwardly between the pins 16. In a second embodiment, Fig. 4, a thyristor is mounted between two heat spreaders 15a, b the edges of which are connected to an insulator 41 by flexible members 40a, 40b to form a hermetic enclosure. The upper heat spreader 15b has an insulated lead 56 connected to the gate electrode of the thyristor. Two pressure plates 33a, 33b contact the-ends of the pins 16a, 16b of the heat spreader 15a, 15b, and are pressed towards each other by means of yokes 43a, 43b clamped together by bolts (47, 48, Fig. 5, not shown) which have spring washers under their heads. The edges of the pressure plates are joined by a glass fibre reinforced polyester resin member 49 to form a duct 50 so that coolant introduced through an inlet 45 flows between pins 16a through duct 50 round the edge of the insulator 41, between pins 16b and out through outlet 46. A stack of such devices, Fig. 6 (not shown) is formed by utilizing pressure plates of increased thickness, provided with grooves to receive sealing rings (58), taking the gate lead (56c) laterally through a series of holes in the pins 16b and out through a seal in the member 49, and applying the yokes to the end pressure members of the stack. The coollant inlets and outlets connect the devices so that the coolant flows through each device in turn. The device may be a diode, thyristor or transistor, the semiconductor wafer may of Si or Ge and may have surface layers of Au, Ag, Cu, Al, Ni, or Pb applied by vapour deposition, cathode sputtering or electrolytic deposition. The metal layers may be omitted if highly doped outer layers are provided. The support plate may be of Mo or W and may be secured to the heat spreader by means of a Au-Sn solder. The heat spreader is of Cu either pure or containing small proportions of Zr, Cr or Ag, the pins may be circular parallelepipedic or somewhat conical and may be produced by hot or cold pressing. The pressure plate may be of Cu or Al and the cooling fluid may be water, oil or air.