Today the microelectronics market requires devices with failure levels approaching zero. To attain this goal all production processes must be subjected to extreme quality control. Molding is one of the most critical assembly processes in power plastic packages. This is related to the complexity of phenomena which may occur at the interfaces involved in this process. This paper reports an adhesion study of epoxy-phenolic molding compounds to the most relevant surfaces encountered in power devices assembled in plastic packages such as copper oxide-hydroxide, nickel oxide-hydroxide, aluminium oxide-hydroxide, and silicon 'nitride'. The study was carried out by combining delamination (scanning acoustic microscopy) and pull strength data with the interface chemistry studied using ESCA. Different adhesion failure mechanisms were found to be operative in these systems. These mechanisms are related to either the chemical nature and thickness of the inorganic layer or the segregation of various additives such as wax, polyoxyalkylene ethers, and alkylsiloxanes, contained in the molding compound.