Abstract: A new type of white whiskers were found on assembled printed circuit board (PCBA) that caused battery leakage failure in field. The whiskers that formed on the powered side of the capacitor were not the result of electro-migration and differ from dendrite growth or tin whiskers. The white whisker failures investigated in this research were on functional RoHS-compliant hardware and were not conformal coated. The conditions associated with the whisker formation are with the following conditions; tin plated components, RoHS-compliant assembly, stored in a shield bag (not sealed), placed inside a box (taped shut) with power from a 3.3 volt battery on components with direct contact to the shield bag. Initial study has revealed the parameters that are needed for the growth: voltage bios, humidity and contamination source. This study has also narrowed down shield bag as the possible source of contamination.
white whiskers, ionic contamination, white residues, shield bag, microenvironments, tin whiskers, lead-free