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Thermal-mechanical reliability analysis of WLP with fine-pitch copper post bumps

Haiyan Sun (Nantong University, NanTong, China)
Bo Gao (Nantong University, NanTong, China)
Jicong Zhao (Nantong University, NanTong, China)

Soldering & Surface Mount Technology

ISSN: 0954-0911

Article publication date: 2 November 2020

Issue publication date: 17 May 2021




This study aims to investigate the several parameters in wafer-level packaging (WLP) to find the most critical factor impacting the thermal fatigue life, such as the height of copper post, the height of solder bump, the thickness of chip. The FEA results indicate the height of solder bumps is the most important factor in the whole structure.


The copper post bumps with 65 µm pitch are proposed to investigate the thermal-mechanical performance of WLP. The thermal cycle simulation is used to evaluate the reliability of WLP by using finite element analysis (FEA). Taguchi method is adopted to obtain the sensitivity of parameters of three-dimension finite element model, for an optimized configuration.


It can be found that the optimal design has increased thermal fatigue life by 147% compared with the original one.


It is concluded that the finite element simulation results show outstanding thermal-mechanical performances of the proposed 65 µm pitch copper post bumps of WLP, including low plastic strain, high thermal fatigue life, which are desired for mobile device.



This research was funded by the National Natural Science Foundation of China, 61974077 and 61804084.


Sun, H., Gao, B. and Zhao, J. (2021), "Thermal-mechanical reliability analysis of WLP with fine-pitch copper post bumps", Soldering & Surface Mount Technology, Vol. 33 No. 3, pp. 178-186.



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