Modified brown oxide treatment as an adhesion promoter for copper lead frame in plastic integrated-circuit packages

Improvement of electronic device packaging reliability, more specifically moisture attack resistance (commonly known as moisture sensitivity level or MSL), has been a hot topic in recent years due to the increase in solder reflow temperature for lead-free solder. In preceding failure mode analysis [1], delamination between lead frame and encapsulation molding compound (EMC) interface plays an important role. Thus a modified brown oxide treatment was developed and applied onto the copper lead frame surface, which is field proven an effective way to elevate package MSL performance. Comparing with typical brown oxide treatment developed in older days for use in printed circuit board (PCB), this modified treatment was specially for use in copper lead frame so that it not only enhances the adhesion with die-attach epoxy glue and EMC, but also leaving a clean silver plating surface for wire bonding.