Mechanical Behavior of Sn-3.0Ag-0.5Cu/Cu Solder Joints After Isothermal Aging

• Published in: Journal of electronic materials 2016-01, Vol.45 (1), p.125-135
• Main Authors: Nguyen, Van Luong, Chung, Chin-Sung, Kim, Ho-Kyung
• Format: Article
• Language: English
• Subjects: Characterization and Evaluation of Materials; Chemistry and Materials Science; Electronics and Microelectronics; Instrumentation; Joint strength; Materials Science; Mechanical properties; Optical and Electronic Materials; Soldering; Solid State Physics; Thermal energy
• ISSN: 0361-5235; 1543-186X
• DOI: 10.1007/s11664-015-4170-1

The tensile impact behavior of lead-free Sn-3Ag-0.5Cu/Cu solder joints aged at 413 K and 453 K for times ranging from 24 h to 1000 h has been investigated in this study. The activation energy for growth of the intermetallic compound (IMC) layer was estimated and compared with literature values. Additionally, the tensile strength of solder joints with IMC thickness of 17.6  μ m was found to be more sensitive to the strain rate as compared with solder joints with thinner IMC layers. Equations representing the relationships among the effective stress, strain rate, aging time, and aging temperature as well as IMC thickness were established using matrix laboratory (MATLAB) software. These equations show that the tensile strength decreases with increase in the IMC thickness to about 8  μ m, after which it becomes nearly constant when the IMC thickness is between approximately 8  μ m and 14  μ m, before decreasing significantly when the IMC thickness exceeds 14  μ m. The main reason for these characteristics was excessive increase in the IMC thickness of solder joints, causing a change in the stress concentration of the tensile load from the protruding region to the inside of the IMC layer at the same tested strain rate.