15 October 2012 Warpage and thermal stress analysis of hybrid infrared focal plane assembly
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Abstract
Hybrid infrared focal plane array detector is always a heterogeneous components assembly. The thermal expansion mismatch between the components, HgCdTe detector chip and silicon readout integrated circuit, combined with large thermal variations (300 K-80 K), results in substantial thermal stress in the interconnection layer and large warpage of the whole assembly. In this paper, the thermal stress distribution and warpage of the assembly are analyzed by finite element method. The results show that the thickness of sapphire electrical lead board, Si-ROIC and GaAs substrate have influences on the thermal stress distribution and warpage of the assembly, and the warpage is affected significantly. Furthermore, we adopt the theoretical formula of multilayer structure to calculate the warpage of IRFPA module. The simulation results are in good agreement with those obtained from the theory. In order to improve the reliability of the IRFPA detector, the assembly is optimized according to the analysis result. After optimizing, the warpage of the assembly decreases from -10.2 um to -5.5 um, the maximum Von Mises Stress in HgCdTe layer decreases by 15.5%, and the uniformity of thermal stress distribution is improved effectively.
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Xing Chen, Fengmei Dong, Kai He, Jianxin Wang, Qingyao Zhang, "Warpage and thermal stress analysis of hybrid infrared focal plane assembly", Proc. SPIE 8419, 6th International Symposium on Advanced Optical Manufacturing and Testing Technologies: Optoelectronic Materials and Devices for Sensing, Imaging, and Solar Energy, 84191B (15 October 2012); doi: 10.1117/12.977431; https://doi.org/10.1117/12.977431
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