Novel Pre-applied Under-fill Material Specialized for Multiple Die Bonding Process

Abstract

TCB (Thermal Compression Bonding) process with NCF (Non Conductive Film) is expected as an effective solution for fine pitch applications brought by the progress of IoT (Internet of Things), however the production volume is limited to small level because of its expensive assembly cost. To mitigate the cost impact, some multiple die bonding methods are being introduced by many players. So far, several NCFs were evaluated for these bonding processes, unfortunately, it is becoming clear that approaches coupled with conventional thermosetting resin compositions are very difficult to achieve required process-ability of the bonding processes due to miss-match between reactivity of the resins and process conditions. That is why the new type of pre-applied under-fill material specialized for multiple die bonding process was desired in the market and has been developed in this study. The developed NCF was designed to survive long time thermal exposure on a bonding stage of TCB bonder so that multiple die bonding such as collective bonding could be successfully performed with enough process margin. To achieve the target specifications, this study has started with the design of new resin composition applied to the developed NCF. Finally, TCB was demonstrated with the developed NCF and it was confirmed that reliable solder joints were formed and no abnormality was observed even after 180mins thermal exposure at 130degC on the bonding stage. Moreover, the developed NCF showed good insulation reliability in HAST. The final reliability tests on package level are ongoing and the results will be visible in no time.