Electrical Shorting Propensity of Tin Whiskers

When a tin whisker bridges two differently biased conductors, an electrical short is not guaranteed. In many instances, the voltage must exceed a threshold level in order to produce current flow due to weak physical contact and the presence of a non-conductive film such as an oxide layer. This paper presents a study that examines the breakdown voltage of tin whiskers and its relation to contact force. Whisker contact force studies were conducted using gold- and tin-coated tungsten probes, and the breakdown voltage was measured using a semiconductor parameter analyzer. It was verified that contact force is a critical factor in determining the type of current-voltage transition and level of breakdown voltage. Lower contact force between the probe and the whiskers caused the multiple transitions in current-voltage characteristics. The tin oxide layers on whiskers were analyzed using field emission transmission electron microscopy (FE-TEM).