Investigations on Encapsulation Stress of a Silicone Elastomer and Its Syntactic Foam

Silicone encapsulation in electronic modules with strong structure constrains suffer the problem of large encapsulation stress, primarily due to the incompressible nature of the elastomeric material that has much higher bulk modulus than Young’s modulus. To tackle this problem, silicone syntactic foam that contains glass micro-balloons (GMB) was employed. The influence of GMB filling on the silicones, including thermo-mechanical properties of the materials and corresponding encapsulation stress was studied via analytical modeling, finite element simulation and experimental measurement. Results showed that the large thermal stress under strong structural constraints could be effectively reduced by GMB filling, which crushed upon compression and altered the elastic properties of the encapsulant.