Tin whisker formation of lead-free plated leadframes |
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Authors: | KS Kim CH Yu JM Yang |
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Affiliation: | aDepartment of Electronic Engineering, Yeojoo Institute of Technology, Yeojoo 469-705, Republic of Korea;bElectronics and Telecommunications Research Institute, Daejeon 305-350, Republic of Korea;cMeasurement and Analysis Team, National NanoFab Center, Daejeon 305-806, Republic of Korea |
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Abstract: | This paper presents the evaluation results of whiskers on two kinds of lead-free finish materials at the plating temperature and under the reliability test. The rising plating temperature caused increasing the size of plating grain and shorting the growth of whisker. The whisker was grown under the temperature cycling the bent shaped in matte pure Sn finish and hillock shape in matte Sn–Bi. The whisker growth in Sn–Bi finish was shorter than that in Sn finish. In FeNi42 leadframe, the 8.0–10.0 μm diameter and the 25.0–45.0 μm long whisker was grown under 300 cycles. In the 300 cycles of Cu leadframe, only the nodule-shaped grew on the surface, and in the 600 cycles, a 3.0–4.0 μm short whisker grew. After 600 cycles, the 0.25 μm thin Ni3Sn4 formed on the Sn-plated FeNi42. However, we observed the amount of 0.76–1.14 μm thick Cu6Sn5 and 0.27 μm thin Cu3Sn intermetallics were observed between the Sn and Cu interfaces. Therefore, the main growth factor of a whisker is the intermetallic compound in the Cu leadframe, and the coefficient of thermal expansion mismatch in FeNi42. |
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