Investigation into the Effect of Gel Hardness on Solder Joints

This paper reports an investigation into the effect of low viscosity silicone gel potting on Ball Grid Array (BGA) solder joints and surface mount resistor solder joints showing it to be relative to the hardness of the encapsulant. Failures in BGAs and resistor solder joints negatively affect the reliability of electronic modules in any high temperature environment, especially the automotive underhood environment.

The empirical testing shows the effect of the gel hardness on solder joints by continuously monitoring the circuit continuity using an Anatech® Tester during various thermal environmental tests that simulate underhood conditions. The pass/fail criteria used will be two-fold. The first will be actual event failures registered on the Anatech cataloging solder joint failure and the Salt Water Immersion Test proving water intrusion. The second, a more subjective discourse, will concern the visual failures such as bubbles or areas lacking adhesion.