Influences of electrode material and design on the reliability of IRFPAs detector under thermal shock

Under thermal shock, high fracture probability in indium antimonide (InSb) infrared focal plane arrays (IRFPAs) limits its applicability. Typical fracture photographs under thermal shock shows that the cracks originating from the area above public electrode are dominant. In order to learn the influences of electrode material parameter and design on the reliability in InSb IRFPAs detector, the proposed improved equivalent modeling method is employed to build three dimensional InSb IRFPAs structure analysis model. Simulated results show that different electrode materials greatly influence the maximal thermal stress appearing in InSb chip and public electrode, and among the electrode material parameters, the coefficient of thermal expansion is the main affecting factor on thermal stress. With the increasing electrode thickness, the maximum thermal stresses in InSb chip and public electrode both decrease, which means the smaller electrode thickness leads to larger thermal stress in InSb chip and electrode. Besides, it is also found that adjusting the electrode layout to avoid the overlap between indium bumps and the embedded part of electrode can effectively reduce the stress concentration in the area of InSb chip above public electrode. All these are beneficial to optimize the structure of InSb IRFPAs and reduce the fracture probability.