Effects of Surface Nanostructures on Bonding Using Carbon-Dioxide-Assisted Thermal Fusion Bonding Process
Date Issued
2011
Date
2011
Author(s)
Yao, Tsung-Fu
Abstract
Through the multi advantages of light weight, low cost, and easy-to-manufacture, plastic material has become a widely-used engineering material. Plastic material has been used for micro-fluidic devices. In the manufacture of micro-fluidic devices, bonding and packaging is critical for sealing of the devices and protecting the microstructures.
This research focuses on enhansing the bonding strength of PMMAs by carbon-dioxide-assisted below-Tg thermal fusion bonding process. In this study, surface nano-pore will be pre-made on one of the PMMA before CO2-assisted thermal fusion bonding. Experimental results show that the bonding strength between PMMAs achieve 1.22MPa; it is much higher than that between plain PMMAs, which is 800 kPa. Due to the nano-pore structures, there will more contact areas, more mutual molecular chain diffusion and structure inter lock after bonding.
This research also investigates the effect of nano-pillar and nano-pore structures on bonding strength. Experimental results show that the bonding strength of PMMAs with nano-pillar structures on PMMA surface is inferior to that of PMMAs with nano-pore structures after carbon-dioxide-assisted bonding fusion. By the influence of CO2, the whole nano-sized pillars had been softened and collapsed under holding pressure. They fail to provide the effect of inter-lock at the interface, resulting in inferior bonding strength. As far as the effect of all micro-sized structures on the bonding, this research also used femtosecond laser to fabricate the micro structures, and then applied the microstructure to PMMA bonding process. The experiment showed inferior results either. When structures’ size comes to micro order, the PMMAs will not be able to be in conform contact and inter-lock because the softened CO2 layer is just nanometer deep.
Finally, the nanostructure inter-lock concept has also been applied to heterogeneous material bonding in this study. The research attempts to bond the two kinds of plastic, PC and PMMA, using CO2-assisted thermal fusion bonding. Results show that a bonding strength of 1.20 MPa can be achieved with nano-pillar structures on the PC, utilizing the higher material strength of PC to plug in the softened layer of PMMA surface. This research has proven that well-planed nanostructures enhance the bonding strengths of PMMAs and PMMA/PC using CO2-assisted below-Tg thermal fusion bonding.
Subjects
Carbon dioxide(CO2)
Polymethyl methacrylate(PMMA)
nanostructure
femtosecond laser
heterogeneous bonding
Type
thesis
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