Electronics Forum | Fri Aug 22 09:07:22 EDT 2008 | blnorman
Sulfur is probably the culprit. Board supplier should be providing boards with anti-tarnish sheets between the individual boards. Also, cardboard is a major source of sulfur and so boards should not be shipped in cardboard.
Tin Whiskering on PCBA Capacitors in Storage (Inside ESD Bag, Inside a Sealed Cardboard Box) Tin Whiskering on PCBA Capacitors in Storage (Inside ESD Bag, Inside a Sealed Cardboard Box) The tin whisker failures investigated in this paper were
SMTnet Express, July 16, 2015, Subscribers: 23,036, Members: Companies: 14,463, Users: 38,550 Testing Printed Circuit Boards for Creep Corrosion in Flowers of Sulfur Chamber iNEMI (International Electronics Manufacturing Initiative) Qualification