TEC cracking in temperature margining liquid-cooled thermal tools in post-silicon validation

Abstract

The thermal electric cooler (TEC) is a solid state heat pump and is a fundamental building block of liquid-cooled thermal tools used for temperature margining in platform validation systems. TECs are prone to cracking and thermal performance degradation during power cycling similar to those in flip-chip packages. A modeling methodology is developed to enable analysis of the thermal tool and understand better the stresses and deformations that the TEC go through during power cycling. TEC cracking and performance degradation have been perennial issues for liquid-cooled thermal tools. Prior method to deal with TEC reliability issues for thermal margining tools deployed in the field was to rework the thermal tools by refreshing the TECs. This is costly and time-consuming process and has a direct impact on the time to market of the silicon. In this paper, we introduce a combined computational fluid dynamics and finite element modeling techniques to explain the reliability issues observed in the TEC. This novel modeling methodology offers a physics-based analysis of the inner mechanics of the thermal margining tool. This paper focuses on a typical liquid-cooled thermal tool and uses experimental data to validate the model. The study also uses the model to do sensitivity analysis on Thermal Interface Material (TIM), fastening, and material properties. This technique can be used to reduce thermal stresses in the TEC, predict the performance of future thermal tool designs, optimize the performance of thermal tools, and extend their useful life while reducing the amount of reliability testing necessary during development. This is especially critical as the number and variety of thermal tools proliferate. This method can serve as a best known method (BKM) for future liquid-cooled thermal tool designs.