Exposed die wafer level encapsulation by transfer molding

In recent years 12" wafer level packaging has evolved from development to actual production with the eWLB product as the main example. To facilitate this, new encapsulation processes and dedicated equipment have been introduced into the market. In addition, also the wafer level package itself is evolving. Old package designs are often over-molds with thick mold caps obtained by compression molding. New designs are focusing more on mold cap thicknesses of 100 μm or less. Higher integration levels, warpage reduction and geometric efficiency are the obvious main drivers behind this. The thinnest mold cap can be achieved when the cap height is equal to the die thickness, resulting in exposed die molding, which can be accomplished with the transfer molding process. This paper highlights compound viscosity and dynamic clamping, two topics that are crucial for successful transfer molding process of thin 12" exposed wafer level packages. Finally, an actual example of an expose 12" wafer level molded sample is presented.