Abstract
Over the last decade, a significant number of investigations have been performed to develop and optimize cold plates for direct-to-chip cooling with cold plates attached to processor packages. Many investigations have reported computational simulations using commercially available CFD tools that are compared to experimental data. Generally, the simulations and experimental data are in qualitative agreement but often not in quantitative agreement. The computational simulations are used for thermal and hydraulic characterization of these cold plates and are used to perform parametric analysis to address the cold plate’s optimal design. Unfortunately, the experimental characterizations have high uncertainty due to lack of proper attention to the basic measurements, particularly of temperature. Extensive experimental evaluations reported in this paper will be used to demonstrate the frequent errors in experimental thermal measurements used in forming the defined thermal resistance and the experimental artifacts during testing that lead to unacceptable inconsistency and uncertainty in the reported results. By comparing experimental thermal data such as the temperature at multiple points on the processor lid, and using that data to extract a meaningful measure of thermal resistance, it will be shown that the data uncertainty and inconsistency is primarily due to three factors: (1.) inconsistency in the thermal boundary condition supplied by the TTV to the cold plate; (2.) errors in the measurement and interpretation of the surface temperature of a solid surface, such as the heated lid surface or the base of the cold plate, and (3.) errors introduced by improper contact between cold plate and TTV. A standard thermal test vehicle (STTV) was designed and used to provide reproducible thermal boundary conditions to the cold plate. An uncertainty analysis was performed in order to discriminate between the sources of inconsistencies in the reporting of thermal resistance, including parameters such as mechanical load distribution, methods for measuring the cold plate base, and TTV surface temperatures.
