Authors: Keith Sweatman, Junya Masuda, Takashi Nozu, Masuo Koshi, and Tetsuro Nishimura Company: Nihon Superior Co., Ltd Date Published: 1/26/2010
Pan Pacific Symposium
Abstract: Corrosion has been identified as one source of the compressive stress that is a driver of whisker growth in high tin lead-free solders and in this paper the authors report a study directed at identifying the relationship between the extent of corrosion and the concomitant whisker growth. Printed circuit coupons with an OSP finish were soldered with SAC305 solder using wave, reflow, and hand soldering methods with “no-clean” fluxes typical of current commercial practice. These coupons were exposed to conditions of 40°C/95%RH, 60°C/90%RH and 85°C/85%RH for up to 5000 hours. As well as recording the location of whiskers, their density, and length as a function of time, the extent of corrosion was measured on cross-sections through the solder. The highest incidence and fastest growth rate occurred on test pieces exposed to 85°C/85% RH. The incidence and growth rate of whiskers was found to vary with the soldering method.