ENHANCED THERMAL CONDUCTIVITY IN LOW TEMPERATURE COFIRE CERAMIC (LTCC) USING THICK SILVER TAPE

摘要

Increased speeds for digital devices also equate to increased power dissipation. Discrete device power dissipation is projected to exceed 100W/cm~2 This level of concentrated power 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. An enhanced thermal via structure to transport heat through the LTCC was developed using a co-fireable thick film silver tape. The green thickness could be varied with tape casting, with successful fabrication and firing of tapes up to 0.5mm (20 mils) 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, although high metal loaded thermal vias could be developed in the ceramic layer. The via section had a theoretical thermal conductivity near 100 W/m-℃, resulting in a thermal impedance of less than .06℃-cm~2/W with a 1mm thick sandwich structure, a 100 times decrease compared to LTCC.