A new high strength copper-tin-zinc alloy for connectors and other conductive springs

Waterbury Rolling Mills, over the past decade, has developed many High Performance Alloys (patented). Six of these alloys have been improved tin brass alloys which exhibit an excellent combination of mechanical strength, including tensile and yield strength, and formability, as measured by the radius to thickness ratios in bending. The alloys also have very good electrical and thermal conductivity and high resistance to thermal stress relaxation. These alloys were targeted for applications which included conductive springs, contacts and terminals for electronic, electric and automotive connectors and other electromechanical components. Earlier technical papers have previously introduced these alloys. These alloys have already been selected and specified in many applications over higher cost alternative alloys. The current paper describes the latest and strongest alloy in the high performance tin brass alloy family developed by Waterbury Rolling Mills. The alloy is an improved tin brass with additions of small amounts of iron, nickel and phosphorus, with special processing that results in the formation of iron nickel phosphides, with controlled particle sizes. Presence of these particles facilitates high strength with good formability. Contrary to the normal experience, the high strength is also accompanied by higher conductivity. The new alloy, containing 3% tin and approx. 8% zinc, is an inexpensive substitute for many existing alloys. One of them is alloy C52100, a phosphor bronze which contains 8% tin. The alloy presented has similar strength and formability as C52100 but has approximately double the electrical conductivity and superior resistance to stress relaxation at elevated temperatures. Besides C52100, the alloy presented is also capable of replacing very expensive alloys like beryllium coppers and copper-nickel-silicon alloys, in many applications. This paper presents comparative data of the new alloy with other alloys commonly considered by design engineers for high performance applications. The alloy described in this paper addresses the growing demand of the connector industry for cost-effective high performance alloys.