Enhanced Thermal Stress Reliability of Photodetector Devices Based on Thermal-Mechanical Simulation and Temperature Cycling Experiments

To improve the thermal stress reliability of photodetector packaging for a harsh application environment defined by AEC-Q102 standards, the approach by adding SiO 2 fillers into compression molding phenyl silicone for photodetector packaging was designed and optimized based on automotive level product requirements. The coefficients of thermal expansion (CTE) of molding silicones with and without SiO 2 fillers were characterized via thermal mechanical analysis (TMA). Thermal-mechanical stresses in the bonding gold wires were simulated by finite element analysis (FEA) method and validated by temperature cycling (TC) test. The reasons behind the improvement of the physical properties of the molding phenyl silicone are presented. Meanwhile, heat affected zone (HAZ) of gold wire was also taken into consideration by a more accurate analysis for the failure position of gold wire. This approach improves the temperature cycling reliability dramatically. The reliability result showed that inexpensive phenyl silicone with 40% SiO 2 filler can achieve over 1000 cycles from -40 ºC to 125 ºC without bonding wire failure via inexpensive approach, even better than high quality but expensive phenyl silicone. Finally, the electrical-optical performance of packaging devices was compared and characterized with different encapsulation material scenarios, which shows that inexpensive phenyl silicone with 40% SiO 2 filler also has a slight lower photocurrent response compared with expensive phenyl silicone without SiO 2 fillers.