Whiskers

It means "whisker-like thing" and refers to a whisker-like crystal precipitate mainly generated from tin plating in connectors.
It occurs and grows when stress is applied to tin, and its growth is accelerated by high temperature and high humidity. Growth beyond the pitch of the connector and falling off of objects larger than a certain size cause short-circuit defects. Although it is possible to control the plating condition to some extent, the risk cannot be eliminated with tin plating. It is necessary to select parts based on evaluations according to product specifications and installation environment.