The suppression of tin whisker growth by the coating of tin oxide nano particles and surface treatment

Tin oxide nano particles dispersed in water solution were sprayed on the tin-plated copper surface and served as coating layer in order to study its effect on the prevention of tin whisker formation. The results indicated that tin oxide nano particles could inhibit the growth of tin whiskers to certain extent. Many hillocks instead of long whiskers grew on the surfaces of samples that underwent 25, 40 and 60 °C annealing for 10 weeks. Furthermore, a strong etchant and polishing were applied to the tin-plated samples. XPS results showed that the surface oxide was removed by surface treatments; the surfaces were then coated by spraying nano particles. It is found that the coherency of the re-grown oxide during annealing was reduced, leading to the growth of hillocks instead of long whiskers. This approach seems to successfully enhance the relaxation of stress to prevent the growth of long whiskers.