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Journal of Electronic Materials

, Volume 43, Issue 1, pp 259–269 | Cite as

Investigation of Sn Whisker Growth in Electroplated Sn and Sn-Ag as a Function of Plating Variables and Storage Conditions

  • Jaewon Chang
  • Sung K. Kang
  • Jae-Ho Lee
  • Keun-Soo Kim
  • Hyuck Mo LeeEmail author
Article

Abstract

Sn whiskers are becoming a serious reliability issue in Pb-free electronic packaging applications. Among the numerous Sn whisker mitigation strategies, minor alloying additions to Sn have been proven effective. In this study, several commercial Sn and Sn-Ag baths of low-whisker formulations are evaluated to develop optimum mitigation strategies for electroplated Sn and Sn-Ag. The effects of plating variables and storage conditions, including plating thickness and current density, on Sn whisker growth are investigated for matte Sn, matte Sn-Ag, and bright Sn-Ag electroplated on a Si substrate. Two different storage conditions are applied: an ambient condition (30°C, dry air) and a high-temperature/high-humidity condition (55°C, 85% relative humidity). Scanning electron microscopy is employed to record the Sn whisker growth history of each sample up to 4000 h. Transmission electron microscopy, x-ray diffraction, and focused ion beam techniques are used to understand the microstructure, the formation of intermetallic compounds (IMCs), oxidation, the Sn whisker growth mechanism, and other features. In this study, it is found that whiskers are observed only under ambient conditions for both thin and thick samples regardless of the current density variations for matte Sn. However, whiskers are not observed on Sn-Ag-plated surfaces due to the equiaxed grains and fine Ag3Sn IMCs located at grain boundaries. In addition, Sn whiskers can be suppressed under the high-temperature/high-humidity conditions due to the random growth of IMCs and the formation of thick oxide layers.

Keywords

Sn whiskers electroplating minor alloying 

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Copyright information

© TMS 2013

Authors and Affiliations

  • Jaewon Chang
    • 1
  • Sung K. Kang
    • 2
  • Jae-Ho Lee
    • 3
  • Keun-Soo Kim
    • 4
  • Hyuck Mo Lee
    • 1
    Email author
  1. 1.Department of Materials Science and EngineeringKAISTTaejonRepublic of Korea
  2. 2.IBM T.J. Watson Research CenterNew YorkUSA
  3. 3.Department of Materials Science and EngineeringHongik UniversitySeoulRepublic of Korea
  4. 4.Fusion Technology LabHoseo UniversityAsanRepublic of Korea

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