Mitigating Lead-Free Issues in Electronic Circuit Board Manufacturing With an Advanced Conformal Coating to Manage Tin Whisker Risk

The use of pure tin plating on the leads of electronic components is prohibited in many military contracts, because over time the pure tin grows conductive whiskers that causes short circuits. Unfortuneately, pure tin plating is now used by many of the component manufacturers as part of the "lead-free" movement. One of the tin whisker risk mitigators that has been tried is the use of conformal coatings on the circuit boards to captivate the tin whiskers as the grow. Multi-year testing has shown that available coatings are punctured by tin whiskers. This proposed project will demonstrate the feasibility of a "Whisker Tough" conformal coating, one that is tougher than the tin whiskers and will not be punctured. Five years of conformal coating/tin whisker testing, plus 2 years of whisker puncture "failure mode" research and modeling have preceded this proposal. Smith & Co has collaborated with both Raytheon Missile Systems and the Navy Best Manufacturing Practices Center of Excellence on this effort. Combined with the specialty knowledge obtained from the development of 29 proprietary coatings, sealers, and adhesives, the R&D so far indicates that a "Whisker Tough" coating can be created.