High Efficiency Polymer Based Direct Multi-jet Impingement Cooling Solution for High Power Devices

To cope with the increasing cooling demands for future high-performance devices and 3D systems, conventional liquid cooling solutions such as (microchannel) cold plates are no longer sufficient. Drawbacks of these conventional cold plates are the presence of the thermal interface material (TIM), which represents a major thermal bottleneck, and the temperature gradient across the chip surface. Alternative advanced liquid cooling solutions have been proposed such as intertier and intra-tier cooling for 3D systems. These solutions are however not compatible with the fine pitch requirements for high bandwidth communication between different tiers of a 3D system. Liquid jet impingement cooling is an efficient cooling technique where the liquid coolant is directly ejected from nozzles on the chip backside resulting in a high cooling efficiency due to the absence of the TIM and the lateral temperature gradient. In literature, several Si-fabrication based impingement coolers with nozzle diameters of a few tens of μm have been presented for common returns, distributed returns or combination of micro-channels and impingement nozzles. The drawback of this Si processing of the cooler is the high fabrication cost. Other fabrication methods for nozzle diameters of a few hundred μm have been presented for ceramic and metal. Low cost fabrication methods, including injection molding and 3D printing have been introduced for much larger nozzle diameters (mm range) with larger cooler dimensions. These dimensions and processes are however not compatible with the chip packaging process flow. This PhD focuses on the modeling, design, fabrication and characterization of a micro-scale liquid impingement cooler using advanced, yet cost efficient, fabrication techniques. The main objectives are: (a) development of a modeling methodology to optimize the cooler geometry; (b) exploring low cost fabrication methods for the package level impingement jet cooler; (c) experimental thermal and hydraulic characterization and analysis of the fabricated coolers; (d) applying the direct impingement jet cooling solutions to different applications.status: publishe