Three types of discontinuous growth behaviour of tin whiskers are described. First, growth bands were observed in whiskers on a tin finish held in an ambient environment for 30 days after plating; the spacing between the growth bands was 0.2-0.4 mu m. Second, growth of a whisker was discontinuous with time, in which there was about 30 days of stagnation, after which whisker growth reoccurred. Third, an irregular whisker with a triangular morphology and abruptly changing cross-section was observed by SEM. Discontinuous whisker growth behaviour challenges the previously proposed mechanism of tin whisker growth. It is postulated that alternating breakdown and self-curing in air of an oxide film at point defects could be a reason for discontinuous growth of whiskers.
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chinese acad sci, inst met res, shenyang natl lab mat sci, shenyang 110016, peoples r china.;xian, ap (reprint author), chinese acad sci, inst met res, shenyang natl lab mat sci, 72 wenhua rd, shenyang 110016, peoples r china;ap.xian@imr.ac.cn
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