Authors: Qing Duan Meng, Xiao Ling Zhang, Xiao Lei Zhang, Wei Guo Sun

Abstract: Based on viscoplastic Anand’s model, the structural stress of 8×8 InSb infrared focal plane array (IRFPA) detector is systemically analyzed by finite element method, and the impacts of design parameters including indium bump diameters, heights and InSb chip thicknesses on both von Mises stress and its distribution are discussed in this manuscript. Simulation results show that as the diameters of indium bump decreases from 36 μm to 24 μm in step of 2 μm, the maximum stress existing in InSb chip reduces first, increases then linearly with reduced indium bump diameters, and reaches minimum with indium bump diameter 30 μm, the stress distribution at the contacts areas is uniform and concentrated. Furthermore, the varied tendency has nothing to do with indium bump standoff height. With indium bump diameter 30 μm, as the thickness of InSb chip reduces from 21 μm to 9 μm in step of 3 μm, the varying tendency of the maximum stress value in InSb chip is just like the letter U, as the indium bump thickness decreases also from 21 μm to 6 μm in step of 3 μm, the maximum stress in 8×8 InSb IRPFA decreases from 260 MPa to 102 MPa, which is the smallest von Mises stress value obtained with the indium diameter 30 μm, thickness 9 μm and InSb thickness 12 μm.

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Authors: Qing Duan Meng, Xiao Ling Zhang, Xiao Lei Zhang, Wei Guo Sun

Abstract: Two-step method is used to research stress and its distribution in 64×64 InSb infrared focal plane array (IRFPA) employing finite element method. First, a small 8×8 InSb IRFPA is systemically studied by varying indium bump diameters, standoff heights and InSb chip thicknesses in suitable range, with indium diameter 30μm, thickness 9μm and InSb thickness 12μm, von Mises stress in InSb chip is the smallest and its distribution is uniform at contacting areas. Then, the sizes of InSb IRFPA is doubled once again from 8×8 to 64×64 to learn the effect from chip sizes, thus, the stress and its distribution of 64×64 InSb IRFPA is obtained in a short time. Simulation results show that von Mises stress maximum in InSb chip almost increases linearly with array scale, yet von Mises stress maximum in Si ROIC decreases slightly with increased array sizes, and the largest von Mises stress is located in InSb chips. Besides, stress distribution on the bottom surface of InSb chip is radiating, and decreases from core to four corners, and stress value at contacting area is smaller than those on its surrounding areas, contrary to stress distribution on top surface of InSb chip.

212

Authors: Qing Duan Meng, Li Gong Sun, Jie Xin Pu

Abstract: Based on viscoplastic Anand’s model, the structural stress of 8×8 InSb infrared focal plane array (IRFPA) detector is systemically analyzed by finite element method, and the impacts of design parameters including indium bump diameters, heights and InSb chip thicknesses on both Von Mises stress and its distribution are discussed in this manuscript. Simulation results show that the maximum stress existing in InSb chip reaches minimum with indium bump diameter 32μm. Under this condition, for the fixed indium height, as the InSb chip thickness reduces from 21µm to 9µm in step of 3µm, Von Mises stress maximum values of InSb chip seems increases gradually, and when the indium bump height reduces from 21µm to 9µm in step of 3µm, its maximum Von Mises stress increase at random increment, do not show certain rules, and indium bump height seems to have a comparable effect on stress value with InSb chip thickness. When indium diameter, height and InSb chip thickness are set to 32µm, 15µm, and 12µm, respectively, the maximal Von Mises value existing in InSb chip reaches minimal value 628MPa, simultaneously the stress distribution at the contacts areas is uniform and concentrated, and this structure is promising to avoid device invalidation.

108

Authors: Qian Yu, Li Wen Zhang, Qing Duan Meng

Abstract: To reduce the fracture probability of InSb infrared detector in thermal shock from room temperature to 77K, for 16×16 mesa structure InSb infrared focal plane array detector with underfill, here ANSYS, is employed to research the impacts from both indium bump diameters and heights on both Von Mises stress and its distribution. Simulation results show that when the diameters of indium bump increases from 20µm to 36µm in step of 4µm, the maximal Von Mises stress in the InSb chip increases slowly. Besides, when the height of indium bump increases from 8μm to 24μm in step of 8μm, the maximal Von Mises stress in the InSb chip reduces from 1200MPa to 1030MPa. Von Mises stress of Si readout integrated circuits is also much smaller than that of InSb chip.

4320

Authors: Li Wen Zhang, Ming Shao, Qiang Yu, Peng Fei Li

Abstract: Based on finite element analysis, the structural stress of 8×8 InSb Infrared Focal Plane Array integrating with microlens arrays dependent on indium bump sizes is systemically researched. Simulation results show that as the diameters of indium bump increase from 16μm to 38μm in step of 2μm, the maximum stress existing in InSb chip first reduces, then increases, and reaches minimum with indium bump diameter 32μm. Yet the maximum stress in the indium bump array is almost unchangeable and keeps at 16.5MPa. The maximum stress in Si readout integrated circuit almost half stress in InSb chip. Besides, the stress appearing on those regions situating just on microlens array is much smaller than its surrounding regions, and the stress distribution is uniform at contacting areas between InSb chip and indium bump.

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