Package structure interaction induced molding issues in MCM packages

As we move forward to newer silicon technologies that requiring MCM dual pad leadframe design and packaging solutions with tighter process margins, it is becoming imperative to resolve ppm wire sweep failure which is critical in transfer molding process as excessive results in shorting of wires, current leakage and electrical failure. Wire sweep has been proved to be closely related to bond span, wire length, height, mold flow direction, mold gate design...etc. With the MCM dual pad leadframe design, architecture dependent mold flow phenomena and race track profile are observed and impact on wire sweep failure rate. Although the impact could be positive on wire sweep, it is considered not acceptable as it would restrict the package design and could introduce incomplete filled or void issues. Besides, it could not meet today´s zero ppm mindset in the automotive and critical applications industry.The deep dive study on mold process and mold compound is carried out. Firstly, key molding parameters were identified, namely transfer speed, clamp pressure and transfer pressure point. Wire sweep locations, wire sweep distribution were used as the output parameter to identify the mold process window. Furthermore, the effects of mold compound material properties were also investigated. The results suggest mold compound properties play a critical role in resolving random wire sweep for the MCM dual pad packages. This paper documents all the studies, evaluations and verification runs done on multi package structures, optimized mold process and mold compound properties to establish a robust package solution for MCM packages.