This thesis employs computational and experimental methods to explore hotspot cooling and high heat flux removal from a 3-D stacked chip using thermoelectric and microfluidic devices. Stacked chips are expected to improve microelectronics performance, but present severe thermal management challenges. The thesis provides an assessment of both thermoelectric and microfluidic technologies and provides guidance for their implementation in the 3-D stacked chips.
A detailed 3-D thermal model of a stacked electronic package with two dies and four ultrathin integrated TECs is developed to investigate the efficacy of TECs in hotspot cooling for 3-D technology. The numerical analysis suggests that TECs can be used for on demand cooling of hotspots in 3-D stacked chip architecture. A strong vertical coupling is observed between the top and bottom TECs. As a result, TECs need to be carefully placed inside the package. Thermal contact resistances between dies, inside the TEC module, and between the TEC and heat spreader are also shown to have a crucial effect on the TEC performance.
TECs are most effective for cooling localized hotspots, but microchannels are advantageous for cooling large background heat fluxes. Water is normally used as a working fluid in microchannels, but it has been suggested by the previous studies that nanofluids could improve the cooling performance. In the present work, this is assessed through experiments and analytical models. First, the results of heat transfer and pressure drop experiments in the microchannels with water as the working fluid are presented and compared to empirical correlations and CFD simulations. Second, the experiments are conducted to compare the cooling effectiveness of spherical gold nanoparticle (10-100 nm diameter) based nanofluids with pure water. The nanofluids do not have a significant effect on either the pressure drop or heat transfer behavior in the channels compared to water.