SMTA International Conference Proceedings


Author: David Hillman
Company: Rockwell Collins Inc.
Date Published: 8/17/2008   Conference: SMTA International

Abstract: The electronics industry is undergoing a materials evolution due to the Restriction of Hazardous Substances (RoHS) European Directive. Printed wiring board laminate suppliers, component fabricators, and printed wiring assembly operations are engaged in multiple investigations to determine what lead-free (Pbfree) material choices best fit their needs. Tin rich solder alloys and pure tin component surface finishes have been introduced to printed wiring assemblies as one material solution. Two metallurgical phenomena, tin whiskers and tin pest, have been associated with tin rich/pure tin materials. A study was initiated in 2005 to investigate the potential occurrence of tin pest in an actual “real world” process scenario using printed wiring assemblies. Static -40°C temperature soaking, -40°C to +40°C thermal shock conditioning and “inoculated” static -40°C temperature soaking were investigated. The ongoing, current results of this 3+ year study will be presented.

Key words: Tin Pest, tin surface finishes, allotropic transformation

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