The whiskering phenomenon has been a chronic problem plaguing the electronic industry for decades, especially with respect to pure tin coatings. With the advancements in tin bath chemistries and tin alloy plating with lead, this problem was surmounted to some extent. Recently, because of impending global environmental regulations and legislation, the expedition to eliminate lead from electronic components has picked up momentum. Concerns of whisker formation in lead-free finishes have resurfaced and have proved to be a nightmare to the electronic industry because of reliability and potential liability issues-especially in fine pitch applications. This paper addresses some of these concerns and attempts to examine the process variables contributing to whisker formation, employing several proprietary lead-free chemistries on a plating line. In manufacturing operations, several factors such as substrate, its surface preparation, micro-stresses in the deposits, nature of chemistry, and post-plating conditions were examined and their impact on whisker formation was evaluated. Applications in press-fit, plated-thruholes (PTH), and solder to board are also discussed in this paper.
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