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Journal of Sensors
Volume 2014, Article ID 952323, 7 pages
Research Article

Analysis on Structural Stress of 64 × 64 InSb IRFPAs with Temperature Dependent Elastic Underfill

1School of Electrical Engineering, Henan University of Science and Technology, Luoyang 471023, China
2Luoyang Institute of Electro-Optical Equipment, Aviation Industry Corporation of China, Luoyang 471009, China

Received 6 May 2014; Revised 7 August 2014; Accepted 7 August 2014; Published 26 August 2014

Academic Editor: Laurent Francis

Copyright © 2014 Liwen Zhang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


To improve the reliability of InSb IRFPAs, underfill has usually been filled between InSb chip and Si ROIC. Around the glass transition temperature, underfill shows viscoelasticity, yet, far below it, which shows apparently temperature dependent mechanical properties. Basing on the temperature dependent elastic model of underfill, firstly a small format array of elements InSb IRFPAs is investigated by changing indium bump diameters and heights; simulated results show that the maximum stress in InSb chip has nothing to do with underfill height and is dependent on indium bump diameter; the varying tendency is just like the horizontally extended letter U. When indium bump diameter is set to 24 m with height 21  m, the maximal stress in InSb chip reaches minimum. To learn the stress in elements in short time, with the above optimal structure, InSb IRFPAs array scale is doubled once again from to elements. Simulation results show that the stress maximum in InSb chip is strongly determined by arrays format and increases with array scale; yet, the stress maximum in Si ROIC almost keeps constant and is independent on array sizes; besides, the largest stress locates in InSb chip, and the stress distribution in InSb chip is uniform.