A method of electrolytically etching the surface of an alloy-type germanium junctiontransistor

摘要

864,621. Electrolytic etching of germanium junction transistors. SONY KABUSHIKI KAISHA. Aug. 30, 1957 [Aug. 31, 1956], No. 27341/57. Drawings to Specification. Classes 37 and 41. The surface of a germanium junction transistor in which the impurity element has been introduced alloyed with lead is electrolytically etched in an aqueous solution of phosphoric acid. Typically the base of an NPN germanium transistor is connected through a 200 # resistor to one pole of a battery to which the collector and emitter are each directly connected in turn for 12 seconds through a changeover switch, the other pole being connected to a platinum cathode to give a current of 500- 800 mA. in a bath of 25% phosphoric acid at 15-30‹ C. The transistor leads of nickel, " Kovar " (Registered Trade Mark) and solder are only slightly discoloured, as are the emitter and collector which are of lead-antimony or lead-arsenic alloy.