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Journal of KWJS. 2006;24(6):21-27. Published online February 12, 2007.
- Thermo-Mechanical Reliability of Lead-Free Surface Mount Assemblies for Auto-Mobile Application
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Sang-Su Ha, Jong-Woong Kim, Jong-Hyuck Chae, Won-Chul Moon, Tae-Hwan Hong, Choong-Sik Yoo, Jeong-Hoon Moon, Seung-Boo Jung
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- Abstract
- This study was focused on the evaluation of the thermo-mechanical board-level reliability of Pb-bearing and Pb-free surface mount assemblies. The composition of Pb-bearing solder was a typical Sn-37Pb and that of Pb-free solder used in this study was a representative Sn-3.0Ag-0.5Cu in mass %. Thermal shock test was chosen for the reliability evaluation of the solder joints. Typical Cu6Sn5 intermetallic compound (IMC) layer was formed between both solders and Cu lead frame at the as-reflowed state, while a layer of Cu3Sn was additionally formed between the Cu6Sn5 and Cu lead frame during the thermal shock testing. Thickness of the IMC layers increased with increasing thermal shock cycles, and this is very similar result with that of isothermal aging study of solder joints. Shear test of the multi layer ceramic capacitor (MLCC) joints was also performed to investigate the degradation of mechanical bonding strength of solder joints during the thermal shock testing. Failure mode of the joints after shear testing revealed that the degradation was mainly due to the excessive growth of the IMC layers during the thermal shock testing.
Keywords :Lead free;Thermal shock;Intermetallic compound;Shear strength
