Master of Science (MS)
An innovative method of thermoplastic fusion bonding using a pressure assisted boiling point control (PABP) system was characterized to determine the optimum parameters for bonding polymethyl methacrylate (PMMA) components containing microchannels and thin, 250 µm cover sheets. The PABP system enables precise control of the temperature boundary condition and the applied pressure by immersing the components being bonded in boiling water and varying the vapor pressure. Test structure geometries containing microchannels of two depths and four different aspect ratios were designed: 1:10 (Depth: 10µm, Width: 100 µm and Depth: 5µm, Width: 50 µm), 1:50 (Depth: 10µm, Width: 500µm and Depth: 5µm, Width: 250 µm), 1:100 (Depth: 10µm, Width: 1000µm and Depth: 5µm, Width: 500µm) and 1:200 (Depth: 10µm, Width: 2000µm and Depth: 5µm, Width: 1000µm). Microchannels were hot embossed using micro-milled brass mold inserts. Bonding conditions were optimized by observing microchannel deformation under a microscope. The quality of the bonded samples were rupture and leak tested to determine the integrity and strength of the bonds. Mean rupture pressures for channels of AR of 1:10, 1:50 and 1:100 were 851.02 kPa, 780.14 kPa and 706.09 kPa repectively for shallower channels and 831.93 kPa, 739.3 kPa and 524.38 kPa respectively for deeper channels bonded using open loop system. Rupture pressure decreased with decreasing AR and was higher for shallower channels. A closed loop control system was developed for the automatic temperature control. Results of bonding with both open loop and closed loop systems were compared. Mean rupture pressure for channels of AR 1:10, 1:50 and 1:100 for 5 µm depth were 977.54 kPa, 930.93 kPa and 751.39 kPa respectively and 912.11 kPa, 800.07 kPa and 550.96 kPa respectively for 10 µm depth. It was found that the rupture test results were more consistent and repeatable with closed loop system because of better control of the bonding temperature.
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Dathathreya, Kavya, "Characterization of Thermoplastic Fusion Bonding of Microchannels using Pressure Assisted Boiling Point Control System" (2016). LSU Master's Theses. 4537.