Calculation and verification of thermal stress in InSb focal plane arrays detector
Both the InSb chip fracture and the local delamination appearing in the negative electrode region of InSb infrared focal plane arrays (IRFPAs) detectors in liquid nitrogen shock tests are the major failure patterns of the InSb IRFPAs. To analyze the inducements to these typical failure patterns, it is imperative to obtain both the thermal mismatch stresses values and their distributions in the InSb IRFPAs. In this paper, the analytical model developed by C. H. Hsueh is firstly employed to calculate the in plane normal stresses in the center region of the InSb IRFPAs, the in plane shear forces per unit width outside the center region of the InSb IRFPA, and the peeling moments per unit width outside the center region of the InSb IRFPA. Secondly, the structural model of the InSb IRFPAs created by us with ANSYS software is also employed to extract the distributions of the in plane normal stresses, the distributions of the interfacial shear stresses, and the distributions of the out of plane normal stresses. After that comparing both the calculated in plane normal stresses and the interfacial shear forces with the corresponding simulated results, we think that the calculating accuracy of the analytical model is comparable to the simulating accuracy of the ANSYS model of the InSb IRFPAs, and the relative errors are smaller than 10% All these findings provide the technical means in guiding both the structural design and the structural optimization of the InSb IRFPAs assembly in the future.