Breakdown voltages phenomena at molding compound-chip interface

The effects of molding compounds chemical formulation on some electrical failure, faced with plastic encapsulated Power MOS's devices under high temperature reverse biased test (HTRB), have been studied. For this purpose various molding compounds with different chemical formulation were prepared. The chemical formulations were modified in order to study the influence of volume resistivity, ion content, glass transition temperature as well as the segregation of organic additives at the molding compound-die interfaces. X Ray Photoelectron Spectroscopy (XPS) was used to characterize the die molding compound composition in these characterize the die interfacial chemical devices.Volume resistivity, ion content as well as the glass transition temperature characteristics are not enough to explain the power MOS failures.The segregation of polar components like polyoxyalkylene ethers and, in less extent, the presence of polar chemical bonds coming from the matrix resin at the relevant interfaces were found the main cause of the observed failures.