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Effects of Be and Co addition on the growth of Sn whiskers and the properties of Sn-based Pb-free solders

Published online by Cambridge University Press:  12 June 2012

Jaewon Chang ,
Sun-Kyoung Seo ,
Moon Gi Cho ,
Dong Nyung Lee ,
Kyoo-Sik Kang  and
Hyuck Mo Lee
Jaewon Chang
Affiliation:
Department of Materials Science and Engineering, KAIST, Daejeon 305-701, Republic of Korea
Sun-Kyoung Seo
Affiliation:
Department of Materials Science and Engineering, KAIST, Daejeon 305-701, Republic of Korea; andPackage Development Team, Semiconductor R&D Center, Samsung Electronics, Hwasung-city, Gyeonggi-do 445-701, Republic of Korea
Moon Gi Cho
Affiliation:
Department of Materials Science and Engineering, KAIST, Daejeon 305-701, Republic of Korea; andPackage Development Team, Semiconductor R&D Center, Samsung Electronics, Hwasung-city, Gyeonggi-do 445-701, Republic of Korea
Dong Nyung Lee
Affiliation:
Department of Materials Science and Engineering, Seoul National University, Gwanak-gu, Seoul 151-742, Republic of Korea; and R&D Center, Iljin Materials Co., Ltd., Mapo-gu, Seoul 121-716, Republic of Korea
Kyoo-Sik Kang
Affiliation:
R&D Center, Iljin Materials Co., Ltd., Mapo-gu, Seoul 121-716, Republic of Korea
Hyuck Mo Lee*
Affiliation:
Department of Materials Science and Engineering, KAIST, Daejeon 305-701, Republic of Korea
*
a)Address all correspondence to this author. e-mail: hmlee@kaist.ac.kr
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Abstract

To enhance the reliability of Pb-free solders in high temperature and high humidity conditions, the minor alloying elements of Be and Co are investigated in terms of the growth of Sn whiskers and various properties of Sn-based Pb-free solders. Sn whisker growth is suppressed by adding up to 0.02 wt% Be to Sn-based solders. Adding Be and Co can effectively reduce the undercooling of Sn–1.0Ag–0.5Cu (wt%) solders. And the microstructures of Sn–1.0Ag–0.5Cu–0.02Be solders are similar to those of Sn–1.0Ag–0.5Cu. Furthermore, adding Co to solders increases the microhardness number as a result of the solid solution hardening. Adding Be causes no changes in the morphology or thickness of Cu6Sn5 at the Cu/OSP (organic solderability preservative) under bump metallurgy interface. However, the scallop-like Cu6Sn5 microstructure changes to a flat (Cu,Co)6Sn5 microstructure when 0.05 wt% of Co is added to Sn–1.0Ag–0.5Cu–0.02Be solders.

Keywords

solderingBeCo
Type
Articles
Information
Journal of Materials Research , Volume 27 , Issue 14 , 28 July 2012 , pp. 1877 - 1886
Copyright
Copyright © Materials Research Society 2012

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