A Fused Bath for Electrodeposition of Molten Cadmium -Indium Alloy

Abstract

A fused salt bath for electrodeposition of molten cadmium ‐indium alloy is described, from which ellipsoidal beads of molten alloy are plated onto wires used as leads to emitter and collector electrodes of transistors. Electrodeposition of molten metals can be very rapid, and the deposits are smooth, dense, and nonporous. The fused salt bath, containing 6% cadmium chloride, 56% indium monochloride, and 38% zinc chloride, by weight, is operated at about 260°C. Tungsten anodes are used. With 6 v d.c. applied, a 2 mg ellipsoidal bead of cadmium ‐indium alloy of approximately eutectic composition can be deposited on a 0.5 mm wire that is immersed a depth of 1.5 mm into the plating bath in about 4 sec. Under these conditions, current density is of the order of 40 amp/cm2. The effect of bath composition and of plating conditions on alloy composition and plating rate is discussed.

Structural and energetic assessment in cadmium–indium liquid alloys

“…The Cd-In system has been investigated by several researchers [1][2][3][4][5]. Cadmium and indium form a eutectic alloy (eutectic temperature 123 C) at the composition of 25% Cd and 75% In by weight [1].…”

“…Cadmium and indium form a eutectic alloy (eutectic temperature 123 C) at the composition of 25% Cd and 75% In by weight [1]. It can be considered a satisfactory solder for electrodeposition in electronic devices.…”

“…It can be considered a satisfactory solder for electrodeposition in electronic devices. In the fabrication of alloyed-junction and surface-barrier type transistors, indium metal cannot be used as a solder since it is not desirable to melt the electrodes during soldering [1]. Eutectic cadmium-indium alloy of the above-mentioned composition can be used for soldering whisker wires, ribbons, stem leads or other electrical connections to the emitter and collector electrodes without melting the In electrodes [1].…”

“…In the fabrication of alloyed-junction and surface-barrier type transistors, indium metal cannot be used as a solder since it is not desirable to melt the electrodes during soldering [1]. Eutectic cadmium-indium alloy of the above-mentioned composition can be used for soldering whisker wires, ribbons, stem leads or other electrical connections to the emitter and collector electrodes without melting the In electrodes [1]. The Cd-In eutectic alloy is harder (has greater tensile strength) than In metal at a given temperature and hence the joints soldered with it are considerably stronger than joints soldered with In alone.…”

“…Moreover, unlike transistor soldered with Sn-In alloy, transistors having In electrodes soldered with Cd-In alloy can be clean-up etched in acids such as aqueous solutions containing HNO 3 and HF. Cdþþ and Inþþþ ions do not deposit chemically on the Ge during the clean-up etching process [1]. These interesting features of Cd-In alloy led authors for its thermodynamic and structural investigations.…”