Development of innovative substrate and embedding technologies for high frequency applications

This paper brings into light all the new developmental work performed in the wide domain of high frequency PCBs for the realisation of innovative metasurfaces at 5GHz as well as compact highly integrated 5G antenna-in-modules at 40 GHz. There is a fast growing demand in high frequency market that justifies the intense R&D work also on microwave and especially mmWave technologies, comprising both “beyond the state-of-the-art high frequency PCBs” and advanced PCB integration concepts. In this context, this paper intends to highlight new knowledge in materials, processes as well as thermal dissipation concepts, that have been derived from various R&D projects, but especially in the framework of the FET-EU “Visorsurf” and the EU-Serena projects. In specific, R&D work will be shown on the emerging concepts of metamaterials that can be software programmable and adapt their properties. The Visorsurf main objective is the development of a hardware platform, the Hypersurface, whose electromagnetic behavior can be programmatically defined. The key enablers for this are the metasurfaces whose electromagnetic properties depend on their internal structure. The Hypersurface hardware platform will be a 4-layer build-up of high frequency PCB substrate materials with the metasurfaces on the top and custom electronic controller nodes at the bottom of the PCB hardware platform. This paper will elaborate on how innovative PCB processes have been tailored to high frequency substrates for the manufacturing of the first 4-layer Hypersurface PCB hardware platform with a size of 300mmx300mm.}{In a complimentary way, the paper will describe in detail new chip embedding concepts in the same family of high frequency PCB substrates toward the realization of highly miniaturized advanced packages for 5G mmWave applications at 40 GHz. These concepts show vividly the potential of PCB embedding technologies as the mean for heterogeneous integration in high frequency advanced packages/modules. The paper discusses in detail all process chain developments in high frequency PCBs for the embedding of GaN and SiGe chips in PCBs, their interconnection path concept, the embedding of passives, the fabrication of the antenna module and its stacking on a high power or low power PCB module for the final formation of a 6-layer antenna-in-module package which could be separately assembled on the system board. Furthermore, the paper will present for the first time innovative thermal dissipation concepts for the “Serena” antenna module, with the prevailing scenario of thermal vias to the bottom of the GaN and SiGe chips for direct heat removal. All processes for realization of high frequency substrates and embedded 5G 40 GHz antenna modules will be discussed in detail.