Substrateless sensor packaging using wafer level fan-out technology

In this paper, we present the application of a substrateless packaging technology consisting of sub sequential molding of ASIC and MEMS dice und forming redistribution layers (RDL) on the molding compound. Acceleration sensors and pressure sensors were packaged, each sensor type presenting its own challenges. For pressure sensors it is crucial to ensure the access of the surrounding media to the pressure sensitive membrane. This was achieved by structuring the redistribution layer without changing the process, making the application of standard equipment and materials relatively easy. The acceleration sensors needed to be modified by trough silicon vias to fit the packaging process. For the redistribution layer, a novel approach was evaluated in parallel to the standard thin-film technology for the acceleration sensor package. All sensor packages fabricated by the process have been found to be within the specifications of standard packages using the same MEMS dice.