Thick silver tape in low temperature cofire ceramic (LTCC) for thermal management

Power dissipation for devices is projected to exceed 100W/cm(2) which requires the development of novel thermal management systems to manage the thermal load from the device to some heat sink. The entire system must be considered, as the path with the highest thermal resistance will dominate the overall thermal performance. This work developed a cofireable thick (0.5mm) silver tape, which could be used for lateral heat transfer or combined with an enhanced thermal via structure to transport heat through the LTCC The green thickness could be varied with tape casting, with successful fabrication and firing of tapes up to 0.5mm in thickness with no camber in the fired structure. The sintering dynamics were optimized by selection of the particle size and initial porosity (by organic loading of the tape) to match the firing kinetics of the LTCC tape. To inhibit camber, a sandwich structure of ceramic/metal/ceramic had to be used. The metal tape also constrained the LTCC on firing, allowing high metal loaded (similar to80%) hermetic thermal vias to be developed. For enhanced cooling using fluid cooling, a micro heat exchanger was developed by extending the thick silver tape into a open channel Because of the difference in shrinkage kinetics, constrained sintering was used to minimize bowing in the fired silver plates.