Numerical Analysis for Thermo-Mechanical Reliability of Polymers in Electronic Packaging

The universal applicability of polymeric materials in microsystem technology is based on a wide adaptability of their thermo-mechanical as well as their electric/dielectric characteristics. However, as they are generally sensitive to temperature and moisture, obey a misfit in thermal expansion to other electronic materials, and lack a high mechanical strength they are often the weakest link in packaging applications. Finite- element analyses (FEA) are in widespread use to determine the thermo-mechanical performance of the precision material compounds. In theoretical strength analyses the property dependencies on temperature and loading rate are taken into account by viscolelastic material modeling. It is shown the stress effects above the glass transition temperature depend on the constraint situation. In some applications moisture diffusion and swelling has additionally to be considered. Since the adhesive properties are mostly taken advantage of, interface adhesion strength is an additional concern. Accordingly, the phenomenon of stresses at interfaces between dissimilar materials is of special importance within the variety of failure criteria and is therefore discussed in more detail.