Finite Element Analysis on Structural Stress of 32x32 InSb Focal Plane Arrays Integrated with Microlens Arrays

Abstract

Basing on the temperature dependent elastic model of underfill and the Anand's viscoplastic model of indium bumps, A three-dimension finite element model is developed to simulate the structural stress and its distribution in 32×32 InSb infrared focal plane arrays integrated with microlens arrays. To learn the stress and its distribution for large format array in a short time, a small 8×8 InSb IRFPAs is studied firstly, and the stress reaches the minimum with indium bump diameter 28µm, height 24µm. With the optimum typical structure, the stress in 32×32 InSb IRFPAs is obtained in a short time by twice over the arrays format from 8×8 to 32×32, Simulation results show that the largest Von Mises stress locates in InSb chip, as the array scale is enlarged, the Von Mises stress value in InSb chip is strongly determined by arrays format and almost increases linearly with array scale, but the Von Mises stress maximum in Si ROIC, underfill and indium bump almost keeps constant, and does not vary with increased array scale. The stress distribution for 32×32 arrays is uniform at contacting areas. These are favorable to reduce the crack in InSb chip, and improve the production ratio.