Analysis and characterization of green compound material for high voltage application

Anhydride hardener molding compound has been widely accepted as an encapsulation technology for high voltage application products. The roles of encapsulation materials extend beyond just encapsulating the device; these materials also provide heat dissipation and insulation between the device and the package that essentially affects the performance of the device while operating in the field. The recent more stringent electrical test requirement for high voltage application package raises a great challenge to the molding encapsulation technology especially those without using anhydride hardener in the formulation. Anhydride hardener is particularly attractive because of its known intrinsic superior electrical properties and high degree of cross-linking. In this paper, material properties analysis, moldability studies, electrical performance and reliability testing for several types of molding compounds such as anhydride hardener, crystalline filler, low stress Ortho Cresol Novolac (OCN), and Biphenyl/Phenolic molding encapsulations will be presented. The low stress OCN green molding compound was found to work exceptionally well with no significant degradation of electrical performance when compared to anhydride hardener molding compound. More importantly, the low stress OCN molding encapsulation is more cost-effective, provides excellent moldability, good delamination performance and possibly a more reliable package.