Towards a halogen-free package - green molding compound

Green packaging has been a subject of interest and development in semiconductor manufacturing in recent years. At present, encapsulation of semiconductor devices is based on conventional material, which contains halogen, and antimony (Sb). Unfortunately, such elements are a hazard to the environment and health. The alternative is to replace these elements with environmentally friendly flame retardant system which is halogen-and antimony-free, thereby giving rise to the name of green molding compound. In this paper, five green and one conventional molding compounds are discussed. The intention is to select a green compound which has good performance in terms of processibility and reliability. The conventional compound serves as a reference for the five green compounds. The evaluation began with material characterisation which gave a preliminary insight into the general compound behaviour. During material characterisation, several relevant thermo-mechanical properties were compared, such as coefficient of thermal expansion (CTE) and glass temperature (Tg). Moisture absorption, adhesion strength, flexural modulus and filler content will also be discussed. Thereafter, thermal-mechanical simulation was performed to study the stress distribution of the test package with the different compounds. The test package was also subjected to preconditioning at JEDEC level 1 at a 3× 260°C reflow temperature to ascertain its extent of delamination at various interfaces. As the test package is used in automotive application, an additional 100x temperature cycling at -55°C/+150°C was included in the preconditioning condition. This is the standard practice for automotive products. With the results from the various evaluation models, the best green molding compound was selected and confirmed through an additional temperature cycling (TC) test at -55°C/+150°C 1000x.