SUBJECT: Ph.D. Proposal Presentation
BY: David Woodrum
TIME: Wednesday, December 5, 2018, 2:00 p.m.
PLACE: GTMI (formerly MARC Building), 201
TITLE: Mechanical Characterization of Silicon-Glass Interface for High-Pressure Two-Phase Microfluidic Cooler
COMMITTEE: Dr. Suresh Sitaraman, Chair (ME)
Dr. Muhannad Bakir (ECE)
Dr. Yogendra Joshi (ME)
Dr. Peter Kottke (ME)
Dr. Ross Wilcoxon (Rockwell Collins)
Dr. Shuman Xia (ME)


As power demands for microelectronic devices continue to rise, new techniques for heat dissipation require innovative fabrication solutions such as on-chip cooling methods. The mechanical reliability of these high-powered, high-pressure systems is particularly sensitive to the interfacial strengths within the microelectronic architectures. Ongoing cutting-edge research focuses on on-chip cooling methodologies and involves utilizing thermal test vehicles with high-pressure coolant pumped through a microchannel to dissipate heat fluxes exceeding 1 kW/cm2. In one method the microchannels are etched directly into a silicon wafer and then capped by a second wafer possibly made of silicon or, alternatively, Pyrex glass. When fluid flows through the flow channels of the system, internal pressures can exceed 2000 kPa. These high pressures are required to sustain saturation conditions for two-phase flow of high-pressure coolants. The use of two-phase cooling offers the advantage of exploiting extremely high heat transfer coefficient as well as coolant latent and sensible heat. System failure due to cracking of the brittle materials is of particular interest given the potential for catastrophic crack propagation at these pressure levels.

The intent of this work is to accurately characterize the mechanical behavior and reliability of the silicon-glass brittle interface native in high-pressure designs for microfluidic cooling devices. The primary proposed objectives include three separate but related areas of focus. The first objective establishes the overall features of the microfluidic cooler design and examines the thermomechanical analysis of a high-pressure two-phase microfluidic cooler using finite element modeling methodologies. The second objective involves the analytical characterization of the silicon-glass interface through multiple finite-element models. These models will work in tandem with the experimental methodology of the third objective which is to develop an experimental test technique for evaluating the mechanical performance of a silicon-glass interface. By using a pressurized cavity to apply load on the silicon-glass interface, this test will more accurately mimic the working conditions of a high-pressure microfluidic cooler. By satisfying these three objectives, the work will provide methods for testing and modeling which characterize the mechanical behavior and reliability of the high-pressure microfluidic system.