Thermal Modeling of Microfluidic Channels for Cooling High Power Resistors on Multilayer Organic Liquid Crystal Polymer Substrate

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Abstract
Thermal management is an important aspect for any packaging technology incorporating high power devices. In this paper, we present an integrated microfluidic cooling solution for high power surface mount thin film resistors on liquid crystal polymer (LCP) substrate. High power resistors are mounted on top of a 50.8 μm (2 mil) LCP layer, a coolant can circulate, thanks to a micropump, inside a Duroid micromachined channel beneath the LCP layer in order to take away the generated heat. A thermal model is combined from existing thermal models in literature to predict the overall thermal resistance of the organic heat sink in the case of a moving coolant inside the microfluidic channel. Four sets of microfluidic channels with different thicknesses are fabricated and tested. Temperature measurements of resistors with different power ratings and sizes on top of these channels agree with the model predictions and the simulations in the case of static (nonmoving) and dynamic (moving) distilled (DI) water. With this integrated solution, the case temperature of the 40 W resistor, which is mounted on the 254 μm (10 mil) microchannel, can be cooled down to 121 °C at room temperature while the resistor is dissipating 23.2 W of power; this resistor fails to operate beyond 13.3 W in the absence of fluid circulation. This is, to the best of our knowledge, the best thermal cooling performance ever achieved on multilayer organic substrates.

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