Validation of Electronic Package Reliability Using Speckle Interferometry

Abstract

In-situ measurements were performed on organic based substrates under mechanical loading as well as land grid array electronic packages under thermal cycling. Whole field displacement measurements obtained from this analysis were compared with results obtained from similar finite element models. The experimental flexibility and results obtained from speckle interferometry indicate that this method has several substantial benefits over moire´ interferometry. Due to coefficient of thermal expansion mismatches between the package and printed circuit board, creep shear strains developed in the 63/37 SnPb solder. When thermally loaded, these creep shear strains develop cracks in the joint leading to Mode II failure. A single thermal half cycle from 25°C to 125°C was applied to a specimen to simulate the fatigue life of the solder joints undergoing thermal loading and the resulting strains were entered into the Engelmaier reliability prediction model for 63/37 SnPb solder. The experimental results yielded 0.59% strain per cycle with 7485 cycles to failure.