Snap Cure Wafer Back Glue Coating as Die Attach Method for Transistor and Diode Dice

Waferback coating (WBC) is a glue coating on the backside of the wafer as replacement for the present die attach methods like dispense glue and hard soldering with f.i. AuSi and AuSn. The key advantages are cost saving, improved bondline quality, and larger die to die pad ratio. The application of such glue coating for different dice sizes in existing reel to reel lines has been evaluated. Fast processing and curing, suited for high assembly process temperatures, good electrical and thermal conductivity and package reliability are the key study areas. The best coating type that is suited for the complete die size range is investigated. The situation of the large dice is less critical as there are more glue types suitable. Die attach speed, material wirebondability, and package performance are the key challenges addressed in the current study. The final glue version has been run in several carrier packages with satisfactory results. There are some remaining issues, that have to be solved but these are not considered to be showstoppers.