Mechanical stress induced whiskers

Electroplated tin surfaces grow whiskers easily and mechanical loads tend to accelerate this. Our aim was to define how the different kinds of mechanical loads induce the growth of tin whiskers. We have applied 3 types of mechanical loads on component leads covered by either electroplated tin or electroplated tin with silver underlayer. The method of testing was pressing perpendicularly three types of heads on the two types of layers, all equally with 3 N force for 400 hours. These types of head shapes were: spear (60°), pointed (30°), round (r = 250 ¿m). The observed results have shown that different mechanical defects induce the growth of whiskers in different ways and using underlayers have also changed the amount of whiskers grown on the surface in case of using the same needle shape and force.