Analysis and Characterization of Thermal Expansion-Matched Wick-Based Multi-Chip Passive Heat Spreaders in Static and Dynamic Environments

Ensuring adequate spreading of heat dissipated by high power density devices is a critical part of many electronics packaging designs. In many cases, passive wick-based heat spreaders can offer improved heat spreading performance relative to solid conductor alternatives. However, concerns related to performance degradation in high-inertial force environments frequently limit their use to static or near-static applications. In this work we investigate the performance of low coefficient of thermal expansion (CTE) wick-based heat spreaders cooling multiple high heat flux devices in static and high-g environments. Two high-power devices are simulated using custom-manufactured resistor-thermometer chips, enabling dissipation of die average heat fluxes in excess of 150W/cm². Comparative thermal performance is evaluated for wick-based heat spreaders and solid CuMo heat spreaders of equivalent CTE affixed with interface materials typical of those used when attaching a low CTE package to a high CTE cold plate (e.g., Al or Cu). Thermal performance is characterized as a function of heat input during exposure to increasing g-forces applied using a custom-built centrifuge. Experimental observations are interpreted through detailed modeling of fluid flow patterns within the wick structure of the passive heat spreader. Results from these experiments demonstrate that properly designed wick-based heat spreaders have utility in both static and dynamic environments, exhibiting effective conductivities in excess of that obtainable with competitive low-expansion composites.