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Method Of Soldering Refractory Metals

IP.com Disclosure Number: IPCOM000097694D
Original Publication Date: 1961-Apr-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Connell, RA: AUTHOR [+2]

Abstract

The method prepares refractory metals for conventional soldering operations. Refractory metals such as tantalum and niobium are not amenable to soldering using standard techniques because of their persistent oxide coatings. Further, although these metals are normally superconductors, contacts formed between these and other superconductors are generally not superconducting. However, by heating the refractory metal in a vacuum above the decomposition temperature of its oxide and then wetting the resulting metallic surface with a lead tin solder, with at least 20% by weight of tin for good wettability, superconducting solder joints can then be formed.

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Method Of Soldering Refractory Metals

The method prepares refractory metals for conventional soldering operations. Refractory metals such as tantalum and niobium are not amenable to soldering using standard techniques because of their persistent oxide coatings. Further, although these metals are normally superconductors, contacts formed between these and other superconductors are generally not superconducting. However, by heating the refractory metal in a vacuum above the decomposition temperature of its oxide and then wetting the resulting metallic surface with a lead tin solder, with at least 20% by weight of tin for good wettability, superconducting solder joints can then be formed.

The method described is for realizing a superconducting contact between a
0.003 inch diameter niobium wire and a lead plated copper wire. One end of the
0.003 inch diameter wire is first wrapped around a length of 0.02 inch diameter niobium wire which is then formed into a three turn heater coil. A lead-tin solder is next placed upon the coil and the assembly is secured to a pair of supports within a vacuum system. This is evacuated to a pressure of about 10-4 mm Hg. At this time, current is passed through the heater coil, bringing the coil and its solder charge up to a temperature at which the oxide layers coating the niobium wires decompose. The removal of the oxide layers allows the solder to wet the wires.

Upon removal of the niobium wire from the system, the larger diameter wi...