Sunday, July 24, 2005
Kester on Sn/Bi 42/58
Kester - Alloys: "SnBi58 Alloy
* Low melt point lead-free alternative potentially suitable for some consumer electronics. Low melt point precludes its use for applications where operating temperature is close to 138C.
* Large Bi proportion greatly reduces melting point of the solder, but alloy is more brittle. Bi improves wettability, but is somewhat offset by higher oxidation rate. In the presence of lead from HASL boards or components Bi can greatly reduce thermal cycle fatigue resistance due to the formation of Sn16Pb32Bi52 (MP=95C) which can diffuse along the grain boundaries."
* Low melt point lead-free alternative potentially suitable for some consumer electronics. Low melt point precludes its use for applications where operating temperature is close to 138C.
* Large Bi proportion greatly reduces melting point of the solder, but alloy is more brittle. Bi improves wettability, but is somewhat offset by higher oxidation rate. In the presence of lead from HASL boards or components Bi can greatly reduce thermal cycle fatigue resistance due to the formation of Sn16Pb32Bi52 (MP=95C) which can diffuse along the grain boundaries."
