Can Nickel Barriers Eliminate Tin Whiskers?

摘要

Like it or not, lead-free requirements are coming and will be here to stay, along with one of their biggest problems: tin whiskers. Agere Systems (Allentown, Pa.) recently announced promising results from using a nickel barrier layer to hinder the growth of tin whiskers when tin is used as a pad or pin finish over copper. Tin is ubiquitous in soldered electronic interconnections and pin finishes, because it wets well in soldering processes and makes good metallurgical contact with typical pad and pin metals. It also has a well documented tendency to form whiskers (Fig. 1) that can cause shorts and puncture conformal coatings. It is commonly understood that whisker formation in tin is a stress-relief mechanism. Using lead as a companion metal for tin has been effective in terms of relieving stress, but now other ways must be developed for relieving stress in tin solders.