Growth Mechanism of Tin Whiskers by Changing Current Density in the Matte Tin System

• Main Authors: Chun-Lei Hsu, 徐君蕾
• Other Authors: Yee-Wen Yen
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/35200882314893171792

碩士 === 國立臺灣科技大學 === 材料科技研究所 === 96 === Tin whisker growth mechanism and wettability with different electroplating conditions were studied in this work. It was expected that the optimal processing parameters to prevent the whisker growth could be found. Matte Sn was electroplated on the copper at various current densities, and then surface morphology was observed. The different heat treatment conditions were applied to each specimen. The Sn layer with thicker thickness and smaller crystal grain size was observed under passing the higher current density. The formation of intermetallic compounds at the Sn-Cu interface induced the compressive stress to accelerate the growth of the Sn whisker. Meanwhile, the whisker was easily found with the longer aging time. At the high heat-treated temperature, the surface grain tends to be isotropic to eliminate the residual stress between the base interfaces to prevent the growth of the Sn whisker. The wettability between the molten Sn-3.0Ag-0.5Cu solder and Cu substrate was measured by the wetting balance. The Cu deposited the Sn can improve the wettability. The range of the surface tension between the Cu and solder is between 0.4- 0.6 N/m and the contact angle is at 20-70°. Using the lower current density to electroplate the tin on the Cu and applied the long time heat treatment might temporarily relax the compressive stress among Sn layer to prevent the Sn whisker growth. Thus, the reliability of devices can be obtained.