A study on the effects of electrical and thermal stresses on void formation and migration lifetime of Sn3.0Ag0.5Cu solder joints
Soldering & Surface Mount Technology
ISSN: 0954-0911
Article publication date: 27 October 2021
Issue publication date: 12 April 2022
Abstract
Purpose
The purpose of this study is to investigate the effect of electrical and thermal stresses on the void formation of the Sn3.0Ag0.5Cu (SAC305) lead-free ball grid array (BGA) solder joints and to propose a modified mean-time-to-failure (MTTF) equation when joints are subjected to coupling stress.
Design/methodology/approach
The samples of the BGA package were subjected to a migration test at different currents and temperatures. Voltage variation was recorded for analysis. Scanning electron microscope and electron back-scattered diffraction were applied to achieve the micromorphological observations. Additionally, the experimental and simulation results were combined to fit the modified model parameters.
Findings
Voids appeared at the corner of the cathode. The resistance of the daisy chain increased. Two stages of resistance variation were confirmed. The crystal lattice orientation rotated and became consistent and ordered. Electrical and thermal stresses had an impact on the void formation. As the current density and temperature increased, the void increased. The lifetime of the solder joint decreased as the electrical and thermal stresses increased. A modified MTTF model was proposed and its parameters were confirmed by theoretical derivation and test data fitting.
Originality/value
This study focuses on the effects of coupling stress on the void formation of the SAC305 BGA solder joint. The microstructure and macroscopic performance were studied to identify the effects of different stresses with the use of a variety of analytical methods. The modified MTTF model was constructed for application to SAC305 BGA solder joints. It was found suitable for larger current densities and larger influences of Joule heating and for the welding ball structure with current crowding.
Keywords
Acknowledgements
The authors would like to thank the Electronic Component Laboratory of the School of Reliability Systems Engineering, Beihang University, China, for providing equipment for electromigration test.
Funding: This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
Citation
Li, Y., Fu, G., Wan, B., Wu, Z., Yan, X. and Zhang, W. (2022), "A study on the effects of electrical and thermal stresses on void formation and migration lifetime of Sn3.0Ag0.5Cu solder joints", Soldering & Surface Mount Technology, Vol. 34 No. 3, pp. 162-173. https://doi.org/10.1108/SSMT-04-2021-0012
Publisher
:Emerald Publishing Limited
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