ABSTRACT
This chapter reviews the history and use of molding compounds in plastic semiconductor packages, addresses some of the issues and failure modes associated with molding compounds, and touches on future trends. Epoxy cresol novolac replaced bisphenol-A as the preferred epoxy resin due to its better heat resistance. In general, epoxy resins became the preferred backbone for molding compounds due to their inherent low viscosity, fast cure properties, low shrinkage during cure, good adhesion to the other components in a chip package, and good overall mechanical stability. The properties of a molding compound are a balance between its moldability in a high-volume automated manufacturing environment and its relationship to the overall package’s performance and reliability. Biphenyl resins turned out to be the successful approach for reducing moisture uptake in compounds and increased resistance to popcorning. Flexure testing is typically done on relatively flexible materials, like polymers, wood, and composites—which would include molding compounds.
