As one of the key reliability issues, tin whisker problem has perturbed the electronics industry for several decades. Developing an effective way to mitigate the growth of tin whiskers is of great importance. In this study, we develop a novel multilayer method through alternately plating bright Sn and matte Sn layers to control the tin whisker growth. The samples of bilayer, trilayer and quadlayer were fabricated and stored at 55°C/85 % relative humidity and room temperature to evaluate the whisker growth. Experimental results revealed that the tin whiskers tended to grow on the bilayer and trilayer samples with bright Sn as the top layer. The whiskers originated from the middle or bottom layer and broke through the top layer. Compared to the bottom layer of matte Sn, bright Sn as the bottom layer was prone to promote whisker growth, due to irregular formation of intermetallic compound. With increase of the number of Sn layers, the grain structure of bottom layer became the main factor to affect Sn whisker growth. Uniform thickness of individual Sn layers could help to reduce whisker density. Optimal Sn multilayers are obtained to be matte/bright/matte Sn and bright/matte/ bright/matte Sn with uniform thickness of individual layers.

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