The evaluation was initiated when significant resistance changes were observed after the die was attached during the fabrication of the hybrids for TDRS program. The silver filled conductive Ablestik 84-1 is a common die attachment and has a good electrical conductivity. In order to investigate the characteristics of the epoxy, the following experiments were performed to understand its effect on the increased resistance:

• Measurement of the resistance after aging  
• Inspection of the silver settlement of the cured epoxy  
• Finite Element Analysis (FEA) of thermal stress due to mismatch of coefficient of thermal expansion.

The resistance of the epoxy was measured after various stages. The epoxy was cured at 160 °C for 2 hours. The initial measurement was made after the cure. Then the epoxy is baked at 100°C for 24 hours up to 5 times to simulate the aging process. This study is to investigate the resistance increases as epoxy ages. The investigation of the silver settlement is to observe if the silver grains settle at the bottom of the epoxy blob during the cure. The settlement of the silver grains can cause inconsistency in resistance measurement. Finally, the FEA was performed to determine the thermal stress of the expansion/contraction of the epoxy due to temperature cycling.