Flow Boiling in Microgap Coolers - an Enabling Technology for 3D Integrated Circuits, Year 1

Emerging electronic devices offer unprecedented functionality and efficiency, but their operation is constrained by the remote cooling paradigm. An embedded cooling approach, which facilitates integration of coolant channels within the chip stack or electronics assembly, provides high heat flux cooling, reduces heat exchanger and radiator size, and negates gravity effects on the two-phase coolant flow. The goal of the FY18 effort is to validate the orientation-independent two-phase flow data acquired during ground tests by operating a compact flow loop in microgravity and high-g during a suborbital flight in mid-2018 (flight awarded by the Flight Opportunities Program). The FY18 study is follow-on to a multi-year Center Innovation Fund (CIF) effort initiated in FY15 with goals of characterizing the thermofluid performance of embedded two-phase microgap coolers (particularly for 3D integrated circuits), assessing the role of gravity on the two-phase coolant flow in such coolers, and developing a map of parameters for achieving gravity-independent performance. The success of the pioneering FY15 study led to follow-on awards in FY16, FY17, and FY18. Collectively, the research program has: 1. Revealed that existing criteria for achieving gravity-independent flow boiling cover several orders of magnitude of channel sizes, particularly for rectangular ducts that are expected in most embedded cooling applications; 2. Demonstrated orientation-independent flow boiling in "chip-scale" channels with heights ranging from 80 to 430 μm (0.003 to 0.017"); 3. Dissipated as much as 80 W of heat from a 1.6 cm2 thermal test chip (50 W/cm2); 4. Transported 32 W of heat using only 0.9 W of pumping power (COP of 36); 5. Developed a state-of-the-art test facility that supports rapid turnaround testing of microgap coolers (and other innovative evaporators) with a wide range of channel sizes and at differ-ent orientations and flow rates; and 6. Advanced the TRL of microgap flow boiling for space applications from 2 to 4. More »