| 摘要 |
1,190,048. Semi - conductor rectifiers. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. 23 Aug., 1967 [26 Aug., 1966], No. 38757/67. Heading H1K. In the manufacture of a high-voltage rectifier comprising a stack of diode elements 10 held under pressure between current supply members in an insulating holder 20, the individual diode elements are subjected after their assembly in the insulating holder to a common etching step. By this means the risk of contamination of the diode elements subsequently to their etching is substantially eliminated. In the embodiment described the diode elements are produced by diffusing phosphorus into one face and boron into the other face of a P-type silicon wafer to create an NPP+ type structure which is then provided with a nickel coating on the two faces by electroless deposition. The nickel layers are sintered by heating to 650‹ C. and intensified by the electrolytic deposition of gold. One gold layer then has a further rhodium layer deposited on it in order that the electrodes in the diode elements may be distinguished. The diode elements are then obtained by cutting the wafer into circular or rectangular elements. These elements are stacked in a jig upon the spring-loaded cap 18 of the current-supply member 13 until a sufficient number have been assembled; the other current supply member 15 is then pressed upon the stack which is then transferred to the insulating holder 20. In order to clean the diode elements, particularly where the junctions emerge to the surface, the holder with its stack of elements is immersed for 30 seconds in an etching solution containing 100 parts of concentrated nitric acid and 20 parts of concentrated hydrofluoric acid. The assembly is then rinsed in water, etched again in a 2¢% caustic soda solution, rinsed again and dried. As a result of this treatment the gold and rhodium layers project slightly from the sides of the elements. After drying, the space between the stack and the inner surfaces of the holder is filled with a silicone resin and the complete assembly is then encased in a thermoplastic resin, which may be slightly conductive or have a high permittivity to improve the uniformity of the voltage distribution over the stack, Fig. 10 (not shown). |
