Thermally enhanced FOWLP-development of a power-eWLB demonstrator

Current FOWLP (Fan-Out Wafer-Level Packaging) technology, eWLB (embedded Wafer-Level Ball Grid Array), has limited heat dissipation capability, as the materials used in, namely the EMC (epoxy mold compound), originally aimed process ability and mechanical stability, but not heat conduction. As eWLB technology expands to WLSiP (Wafer-Level System-in-Package) and WLPoP (Wafer-Level Package-on-Package) with very high density system integration, combining multiple active chips and different components in the same package, the thermal performance becomes a critical factor. In a broader scope, improving the heat dissipation capabilities opens eWLB technology platform also to more power consuming applications. A specific difficulty for all encapsulated packages is that the EMC must be electrical insulator, which places challenges both on heat conduction and on reliable mechanical bonding to a heat spreader or integrated heat sink. Good heat conductors are, generally, electrical conductors and cannot be used as encapsulate materials. The molding compounds are typically organic resins highly filled with inorganic fillers, but high performance thermal interface material (TIM) are design for metal-metal interfaces, not for organic-metal as required. This paper describes the developments and results achieved towards a Power-eWLB demonstrator using NANIUM's eWLB technology know-how and manufacturing capabilities. This demonstrator aims the improvement of thermal dissipation capabilities of a typical-size eWLB package, by using novel materials, adhesives and assembly processes suitable for high-volume production. It starts from baseline thermal characterization of eWLB package and the selected measurements methods; discusses the selected materials and techniques for the coupling of the WLSiP body to a heat spreader; and presents the 8×8mm2 WLSiP capable of multi-pattern heating and dissipating up to 15W. 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, academic and institutes.