Molding Compounds Adhesion and Influence on Reliability of Plastic Packages for SiC-Based Power MOS Devices

Adhesion and interface compositions of epoxy phenolic molding compounds (EMCs) for high-temperature plastic packages are studied. Interfaces are obtained by molding two EMCs onto aluminum oxide-hydroxide surfaces (oxide onto thin film of AlSiCu) and two die passivation layers consisting of fluorinated polyimide and cyclotene. One compound (A) is a “green” type, containing organic phosphorous-based flame retardant, and the other compound (B) is a conventional type containing antimony (III) oxide and bromined resin flame retardants. A high-temperature storage test at 250 °C is employed to study chemical modifications occurring at the previously mentioned interfaces. A high-temperature reverse bias test at 225 °C is employed to study the influences of the EMC chemical formulations on the reliability of plastic packages for SiC-based power MOS devices. Green compound A shows poor adhesion onto Al oxide and high adhesion strength onto both polymer passivations. The failure mechanism is mainly cohesive on the polymer passivations. The conventional compound B shows a high degree of delamination because of poor adhesion compared with the green compound. SiC-based power MOS devices assembled in plastic packages with compound A show better reliability under HTRB test at 225 °C compared with compound B.