Identifier

etd-06052009-153559

Degree

Doctor of Philosophy (PhD)

Department

Mechanical Engineering

Document Type

Dissertation

Abstract

Microsystem technologies are believed to be an important part of the contemporary technological foundation and are becoming a commercially significant specialty area in manufacturing. The design and fabrication of microscale engineering structures has the potential of generating revolutionary changes in many products over a wide range of industrial sectors. Metal-based microchannel heat exchangers (MHEs) promise high heat transfer coefficients together with mechanical robustness, and are of interest for a wide range of applications. Fabrication technologies capable of creating high-aspect-ratio microscale structures (HARMSs) in metals such as Cu at low cost and high throughput are of particular interest. Likewise, simple and reliable bonding and assembly techniques are critical for building functional metal-based microfluidic devices. This dissertation focuses on various aspects of fabrication, bonding, assembly, and testing of metal-based microdevices. In chapter 1, existing techniques for fabricating metal-based HARMSs are reviewed briefly and compared with each other. A new technique for fabricating metal-based HARMSs, high temperature compression molding, is introduced. Two related issues, bonding and assembly of metal-based HARMSs and testing of assembled metal-based microdevices are discussed respectively. In chapters 2-6, Cu- and Al- based HARMSs were successfully bonded using Al or Sn thin foil intermediate layers and co-deposited Al-Ge thin film intermediate layers, respectively. Quantitative evaluation of bond strengths was carried out as a function of various bonding parameters. Tensile bond strengths are shown to be ~30MPa for bonded Cu pieces and to exceed 75MPa, reaching as high as 165MPa, for boned Al pieces. Detailed characterizations of the micro-/nano- scale structure of buried bonding interfaces were conducted to rationalize results of mechanical testing. Chapters 7&8 talk about systematic experimentation of fabrication, bonding, and testing of Cu- and Al- based MHEs, and detailed results and discussion on flow and heat transfer performance of these MHEs under two different testing configurations, constant heat flux and constant wall temperature. The results show the increase of surface roughness in the replicated microchannels can cause significant improvements to microchannel heat exchanger performance. Finally, chapter 9 summarizes this dissertation research with main results and achievements. Future work is also discussed in this chapter.

Date

2009

Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Wen Jin Meng

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