NPL scientists to research 'tin pest' and 'tin whiskers' in lead free solder

CEMMNT partner, NPL, has been using its expertise in the area of studying the allotropic phase transformation in tin and its alloys, commonly known as tin pest, to measure the implications of adopting lead free solder manufacturing practices. NPL has recently received funding and is committed to co-fund this work with industry support, and has allocated a budget over a two-year period to research the problem of tin pest.

Tin pest can decompose tin into powder at low temperatures and was thought to be a problem of the past, as tin alloys did not suffer the same effect. Yet the Restriction of Hazardous Substances Directive (RoHS) bans most uses of lead and the problem has returned, as lead-free alloys contain 95% to 99% tin. Tin pest could dangerously affect the safety and functionality of electronic products used across many manufacturing sectors, such as the avionics industry.

RoHS has also seen electronics component manufacturers moving to pure tin component termination finishes. These are prone to the spontaneous growth of 'tin whiskers', which can cause catastrophic failures in electronic circuits. Reported failures include the loss of at least two communications satellites and the unplanned shutdown of a nuclear reactor. It has been suggested that conformal coatings (materials applied in thin layers, often by dipping, spraying or flow coating) can be used to inhibit whisker growth.

NPL has developed a new measurement system and test method to assess the ability of different conformal coatings to stop or slow down tin whisker growth. The method can also help conformal coating developers to modify their coatings to inhibit whisker initiation, growth and penetration for electronic circuits.

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