Sirius Glass
Subscriber
In early space shots they had a problem with solder evaporating in the vacuum of space. It often redeposited, making a shorter circuit than the original thus destroying the electronics. We lost several probes due to this.
PE
In space when solder contains tin, tin forms whiskers that cause short circuits and the thread can break off and cause electrical [short circuits] and mechanical problems. As a result, space qualified equipment must have tin free solder.