Influence of thermal shock cycles on Sn-37Pb solder bumps
Soldering & Surface Mount Technology
ISSN: 0954-0911
Article publication date: 20 February 2019
Issue publication date: 16 April 2019
Abstract
Purpose
With continuous concerning on the toxic of element Pb, Pb-free solder was gradually used to replace traditional Sn-Pb solder. However, during the transition period from Sn-Pb to Pb-free solder, mixing of Sn-Pb and Pb-free is inevitable occurred in certain products, and in China where Sn-Pb solder was still used extensively in certain areas especially. Correspondingly, understanding reliability of Sn-Pb solder joints was very important, and further studies were needed.
Design/methodology/approach
Thermal shock test between −55°C and 125 °C was conducted on Sn-37Pb solder bumps in the BGA package to investigate the microstructure evolution and the growth mechanism of interfacial intermetallic compound (IMC) layer. The effects of thermal shock on the mechanical property and fracture behavior of Sn-37Pb solder bumps were discussed.
Findings
Pb-rich phase was coarsened and voids were increased at first; Pb-rich phase was refined and voids were decreased secondly with the increase of thermal shock cycles; the shear strength of solder bumps was slightly decreased after thermal shock, but was back up to 73.67MPa at 2,000 cycles; interfacial IMCs of solder bumps was from typical scallop-type into smooth, the composition of IMCs was from Cu6Sn5 into Cu6Sn5 and Cu3Sn after thermal shock with 1,500 and 2,000 cycles; 20.0 per cent of solder bumps at 1,500 cycles and 9.5 per cent of solder bumps at 2,000 cycles were failure respectively.
Originality/value
Compared with the board level test method, the impact shear test for the single solder bump is more convenient and economical and is actively pursued by the industries. The shear strength of solder bumps was slightly decreased after thermal shock, but was back up to 73.67 MPa at 2,000 cycles; 20.0 per cent of solder bumps at 1,500 cycles and 9.5 per cent of solder bumps at 2,000 cycles were failure.
Keywords
Acknowledgements
This work was supported by the National Natural Science Foundation of China (Grant No. 61774066), the Innovate Program of Common Special Key Technology in Focus Industries of Chongqing (NO.cstc2016zdcy-ztzx0047 and cstc2016zdcy-ztzx0036), the Scientific and Technological Research Program of Chongqing Municipal Education Commission (NO.KJQN201803701), the students’ research projects of Chongqing University of Technology in 2018 (NO.KLA18001) and College Students Innovation and Entrepreneurship Training Program in 2018 (NO.2018CX024) and the Research Projects of Experimental Techniques of Chongqing University of Technology (NO.SK201708).
Citation
Gan, G., Xia, D.-q., Liu, X., Liu, C., Cheng, H., Ming, Z., Gao, H., Yang, D.-h. and Wu, Y.-p. (2019), "Influence of thermal shock cycles on Sn-37Pb solder bumps", Soldering & Surface Mount Technology, Vol. 31 No. 2, pp. 85-92. https://doi.org/10.1108/SSMT-08-2018-0026
Publisher
:Emerald Publishing Limited
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