What's Inside Your PC?

CALCE has recently discovered tin whisker on USB housings on a computer motherboard and USB housings in computer monitors. USB ports are very common in computers and peripheral equipment. USB ports provide easy connections and interfaces devices such as external hard drives, flash drives, printers, and cameras. In examining computer systems produced 2003 time frame (earlier for the motherboard), CALCE has observed very long whiskers. In a set of flat panel monitors, a CALCE Research Associate documented a 900 micron tin whisker.

Tin whiskers have been linked to a variety of field failures. Tin whisker are known to form on tin finished metal surfaces. Alloying lead (Pb) with tin is know to suppress the formation of tin whiskers. Due to European government regulations and market pressures, lead (Pb) can no longer be used in the majority of electronics. As a result of the lead ban, the use of pure tin finish has increased. While test standards have been established to assess tin whisker propensity, no accepted acceleration model for whisker growth based on the standard tests has been established. As a result, these tests cannot be used to predict the growth of whisker in the field or the probability of field failures associated with whiskers.