Thermal stability of non-halogenated "green" mold compounds in electronic packaging industry

Abstract

New inorganic flame retardant systems are now being introduced in mold compound formulations to comply with the global demand for a halogen-free technology. One such system is the inorganic magnesium hydroxide Mg(OH)₂, which does not release hazardous chemicals upon incineration or reclamation. Like other metal hydrates, Mg(OH)₂ exerts a cooling effect when it undergoes endothermic dehydration reaction releasing oxides and water. The other fire-retardant system is the phosphorous type, known for its charring effect during combustion, wherein it effectively cuts off the supply of oxygen by forming a carbon layer on the surface of the burning substrate.
Global efforts to reduce and eventually eliminate the use of potentially hazardous halogenated compounds have driven research in the semiconductor industry to find suitable alternatives for existing product formulations. At ON Semiconductor Philippines Inc., different non-halogenated molding compounds (called green molding compounds – GMCs) were evaluated in terms of thermal stability as compared to existing formulations for microchip encapsulation. The study was conducted parallel to the study of the manufacturability and reliability of different electronic packages based on these green molding compounds. Knowing the thermal stability of the molding compounds can be helpful in optimizing mold process parameters, if needed, and in predicting reliability, when necessary. In this paper, we present thermal stability data of GMCs as compared to existing formulations using thermogravimetric analysis. Evolved by-products were also analyzed using TGIR. Lastly, a thermomechanical stress model using finite element analysis is presented to compare and validate thermal and mechanical performance of SOIC 8L package with standard and GMCs.