Patent GB-1033982-A (GB)
Title: A process for use in the production of a semi-conductor device
IPC: H01L23/40
Filed: 1963-03-08
Abstract: 1,033,982. Semi-conductor devices. SIEMENS-SCHUCKERTWERKE A.G. March 8, 1963 [March 9, 1962], No. 9423/63. Heading H1K. [Also in Division H2] In a semi-conductor device a good electrical and thermal contact between two parts thereof comprising matched contact face portions and the material forming one of the contact faces consisting of a ductile metal, is produced by roughening one of the matched contact faces and then partially smoothing the roughened face by means of a pressing operation using a tool. The two contacts faces are then pressed and held together. The finished contact is as shown in Fig. 2 (not shown), the partly flattened out ridge &c. on the part 5 forming a plurality of contact regions with the upper part 4. Such a contact is used in a semi-conductor rectifier, Fig. 3, between the base 13a of a copper housing 13 and a cooling block 12. The surfaces of both the base 13a and the cooling block 12 are finely ground and the surface of the base is then rough lapped and partly smoothed by pressing with a hardened steel tool. Bolts 19, clamps 20, 20a and rings 21 hold the two contact faces together. The rectifying arrangement may comprise a silicon wafer 14 comprising a PN junction, mounted on a molybdenum carrier plate 15 secured to the base of the housing 13. An electrode 16 makes contact with the wafer 14 and a lead-in conductor 17 which is connected to the housing 13 in a gas-tight portions by a glass seal 18. The cooling block may be cooled by water, or, with the provision of cooling fins 22, by air. In another semi-conductor rectifier, Fig. 4 (not shown), the semi-conductor wafer 35 is connected to the molybdenum carrier plate 34 by means of an aluminium solder layer, and a a thick layer of silver 37 honeycomb roughened on both sides and partly flattened according to the invention, is placed between the base of the carrier plate 34 and the top of the cooling block 32, thus producing a good thermal and electrical contact. A disc of gold 36 is welded to the upper surface of the semi-conductor wafer, at the same time as the aluminium solder layer is melted, to form an alloyed electrode. A copper pin 38 has a copper ring 39 and a molybdenum disc 40 soldered to its end. The exposed face of the molybdenum disc 40, which may be coated with silver and treated according to the invention, is laid on electrode 36 and pressed thereon by a steel ring 41, a centring and insulating ring of mica 42, and three dished springs 44, 45 and 46, the rings being held down by a retaining cylinder 47 having a lip trapped by an inwardly turned flange 33a on the cooling block 32. A bell-shaped housing comprising a lower part 48 of steel or an iron/nickel/cobalt alloy, a central ceramic part 49, and an upper part 50 of the same material as part 48, is positioned with a bottom lip trapped by an inwardly turned flange 33b on the cooling block 32 and a neck portion embracing a copper cylinder 51 gripping the upper end of pin 38 and the end of lead 52. As alternatives the roughened and partially press-smoothed metal surface may be applied directly to a lapped and etched surface of the semi-conductor wafer on the semi-conductor wafer surface may be plated with nickel on silver and the metal may be gold or silver or comprise gold or silver plating. Contacts according to the invention may be made to both sides of a semi-conductor wafer and may be used in multi-electrode, e.g. transistor, devices.