Finite Element Analysis on Structural Stress of large format InSb Infrared Focal Plane Array

Two-step method is used to research stress and its distribution in 64x64 InSb infrared focal plane array (IRFPA) employing finite element method. First, a small 8x8 InSb IRFPA is studied by changing indium bump diameters from 24 mu m to 36 mu m, with indium bump thickness 20 mu m and InSb thickness 10 mu m, the simulated results show that von Mises stress in InSb chip is dependent on indium bump diameters, the varying tendency is just like the letter V, here when indium bump diameters is set to 30 mu m, the smallest von Mises stress is achieved and its distribution in InSb chip is uniform at contacting areas. Then, InSb IRFPA array scale is doubled once again from 8x8 to 64x64 to learn the effect from array size, thus, the stress and its distribution of 64x64 InSb IRFPA is obtained in a short time. Simulation results show that von Mises stress maximum in InSb chip and Si readout integrated circuit almost do not increases with array scale, 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.