Power Transistor

摘要

1,199,266. Transistors. R.C.A. CORP. 29 April, 1969 [6 May, 1968], No. 21784/69. Heading H1K. A transistor comprises an emitter region in the form of a plurality of portions 4 (a, b, c, d) each of which comprises a trunk, 8 extending radially away from a central area 61 and having pairs of latteral branches 10 extending from opposite sides and progressively increasing in length towards the periphery of the wafer, a base region 6 including the central surface area 61 and having branches 14 interdigitated with the emitter region branches, an emitter electrode comprising a metal plate 36 connected to each of the emitter portions near its periphery and having a central aperture 38 through which extends a base electrode 46 connected to the central base area 61. As shown, Fig. 3, the transistor comprises a collector region 19, a base region 16 and four mesa type emitter regions 4a, (b), c, (d). Emitter, base, and. collector contacts are formed by providing layers 20, 24, 28 of Ni covered with layers 22, 26, 30 of solder respectively, by electrolessly depositing a thin layer of Ni on the whole upper face and sintering, covering areas to which contacts are not required with a photoresist mask, electrolessly depositing a second layer of Ni and dipping in molten solder without removing the mask. The wafer is then etched to remove the photo-resist and to etch the exposed edges of emitter junction 18. The collector contact is mounted on a Mo plate 32 brazed to a Cu header 34. The emitter electrode comprises a plate 36 the corners of which have dimples 44 which contact and are soldered to the outer edges of the emitter contacts. An arm (40) extends from one edge of the plate 36 and is soldered to a lead-out pin (42) insulated from the header 34 by a ceramic eyelet. The electrode comprises a phosphor bronze strip one end of which is soldered to a second insulated lead-out pin (48) and the other end extending through an aperture 38 in the emitter electrode plate 36 to contact the central area 61 of the base contact.