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68 SMT Magazine • February 2015 abstract Rockwell Collins initially investigated and qualified Samtec's SEARAY solder charge con- nector (hereafter referred to as "the connec- tor") technology with a focus on solder joint integrity. However, the connector in ques- tion, which has a matte tin finish on the sol- der tail, was found to have a potential risk of tin whiskers due to a small region of the con- nector that was not protected by either solder poisoning or the connector's mechanical con- figuration. An investigation was conducted in accordance with modified JESD201 tin whis- ker susceptibility protocols to assess the pos- sible tin whisker risk concern. The investiga- tion results, coupled with plating and reflow soldering data inputs, demonstrated that the connector's tin whisker risk was extremely low and deemed acceptable. background The implementation of the RoHS European Union Directive in 2005 led to the use of pure tin as an accepted surface finish for PCBs and component terminations. A drawback of pure tin surface finishes is the potential to form tin by david Hillman and ross Wilcoxon rOCKWell COllinS whiskers. Tin whiskers are a metallurgical phe- nomenon that is associated with tin rich/pure tin materials and has been a topic of intense in- dustry interest [1–6] . Figure 1 illustrates tin whis- kers observed on a component lead and in an immersion tin surface finished plated thru hole that was incorrectly plated. The acceptance and usage of pure tin by the electronics industry component fabricators is understandable as the pure tin surface finishes are inexpensive, are simple plating systems to operate and have reasonable solderability char- acteristics. However, the commercial electronics segment, which uses the majority of electronic components, often has product life cycles that are measured in months. In contrast, high per- formance/harsh environment electronics typi- cally have product life cycles that are measured in decades and therefore are much more sus- Tin Whisker Risk Assessment of a Tin Surface Finished Connector Feature Figure 1: Tin whiskers observed on a component lead (top) and in a plated thru-hole (bottom).

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