Electronic Materials Letters

, Volume 14, Issue 6, pp 678–688 | Cite as

Oxidation and Repeated-Bending Properties of Sn-Based Solder Joints After Highly Accelerated Stress Testing (HAST)

  • Jeonga Kim
  • Cheolho Park
  • Kyung-Mox Cho
  • Wonsik Hong
  • Jung-Hwan Bang
  • Yong-Ho Ko
  • Namhyun KangEmail author


The repeated-bending properties of Sn–0.7Cu, Sn–0.3Ag–0.7Cu (SAC0307), and Sn–3.0Ag–0.5Cu (SAC305) solders mounted on flexible substrates were studied using highly accelerated stress testing (HAST), followed by repeated-bending testing. In the Sn–0.7Cu joints, the Cu6Sn5 intermetallic compound (IMC) coarsened as the HAST time increased. For the SAC0307 and SAC305 joints, the Ag3Sn and Cu6Sn5 IMCs coarsened mainly along the grain boundary as the HAST time increased. The Sn–0.7Cu solder had a high contact angle, compared to the SAC0307 and SAC305 solders; consequently, the SAC0307 and SAC305 solder joints displayed smoother fillet shapes than the Sn–0.7Cu solder joint. The repeated-bending for the Sn–0.7Cu solder produced the crack initiated from the interface between the Cu lead wire and the solder, and that for the SAC solders indicated the cracks initiated at the surface, but away from the interface between the Cu lead wire and the solder. Furthermore, the oxide layer was thickest for Sn–0.7Cu and thinnest for SAC305, regardless of the HAST time. For the SAC solders, the crack initiation rate increased as the oxide layer thickened and roughened. Cu6Sn5 precipitated and grew along the grain and subgrain boundaries as the HAST time increased, embrittling the grain boundary at the crack propagation site.

Graphical Abstract


Highly accelerated stress testing Solder joint Oxide Repeated-bending Flexible substrate 



This work was supported by the Technology Innovation Program (Grant No. 10051318, Development of SiC Automotive OBC Power Module with Environment-Friendly High-Temperature Bonding Materials) funded by the Ministry of Trade, Industry & Energy (MOTIE, Korea) and by the National Research Foundation of Korea (NRF), funded by the Korea government (MSIT) through GCRC-SOP (Grant no.2011-0030013).


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Copyright information

© The Korean Institute of Metals and Materials 2018

Authors and Affiliations

  1. 1.Department of Materials Science and EngineeringPusan National UniversityBusanKorea
  2. 2.Components and Materials Physics Research CenterKorea Electronic Technology InstituteSeongnamKorea
  3. 3.Microjoining CenterKorea Institute of Industrial TechnologyIncheonKorea

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