Fabrication, performance and reliability of a thermally enhanced wafer level fan out demonstrator with integrated heatsink

The leading Fan-Out Wafer-Level Packaging technology, WLFO by NANIUM, stemmed from Infineon's embedded Wafer-Level BGA (eWLB) technology, has limited heat dissipation capability, as the materials used in, namely the epoxy mold compound (EMC), originally aimed process ability and mechanical stability, but not heat conduction. As WLFO technology expands to WLSiP (Wafer-Level System-in-Package) for very high-density system integration, the thermal performance becomes a critical factor. In a broader scope, improving heat dissipation capabilities opens WLFO technology platform to power applications. The main challenge for power dissipation on WLSiP packaging is that the EMC must be electrical insulator, placing challenges on both heat conduction and bonding to metallic heat spreader. Whereas mold compounds are typically organic resins filled with inorganic fillers, high performance thermal interface material (TIM) are designed for metal-metal interfaces, not for organic-metal interface as required for chip backside overmolded WLFO package. Another challenge is the assembly of an integrated heatsink, over and larger than the package, on a volume manufacturing capable process, to yield both good thermal conduction and reliable thermomechanical bonding. The work done is part of the collaborative European FP7-ICT project NANOTHERM (Innovative Nano and Micro Technologies for Advanced Thermo and Mechanical Interfaces), together with a consortium of leading IDM, OEM, OSAT, material suppliers and academic/institutes.