Effects of Surface Nanostructures on Bonding Using Carbon-Dioxide-Assisted Thermal Fusion Bonding Process

由於塑膠質輕、成本低及成型易等優點，是應用於檢測晶片微元件最佳材料。在微晶片製造中，封裝技術關係到保護內部結構與流道的密封性，是關鍵技術。 先前研究發現利用二氧化碳滲入PMMA表面，在玻璃轉折溫度（Tg）之下即可進行低溫接合。本研究為了提升接合強度，在PMMA材料表面製作奈米孔洞結構，以增加二氧化碳滲入與接合接觸面積，使PMMA接合介面間在分子擴散糾纏及結構嵌合的雙重作用下，提升接合強度。本研究實驗結果證實有表面奈米孔洞結構之PMMA薄膜，二氧化碳輔助接合強度提升至1.22 MPa，遠比無奈米結構接合的800 kPa為強。 本研究比較將相同尺寸的奈米孔洞或奈米圓柱製作於待接合之PMMA一面對二氧化碳輔助接合強度的優勢，發現奈米圓柱效果沒有奈米孔洞好，原因是在二氧化碳滲入後，全根奈米圓柱皆軟化，後續接合時受壓塌陷而無法提供結構嵌合效果，因此接合強度比有奈米孔洞結構者差。本研究也以飛秒雷射技術製作微米尺寸微結構，並探討該微結構用於PMMA接合效果，結果顯示當表面結構尺寸達微米級大小時效果不好，因基材中受二氧化碳滲入軟化的深度僅至奈米級，輕化塑料無法深入至微米級微結構深處，使介面間材料接觸面積過低，接合強度大幅遜於奈米結構。 本研究也探討奈米結構二氧化碳輔助熱融接合應用至PC與PMMA異質材料之接合。本研究先在PC表面製作奈米圓柱，二氧化碳滲入後，後續在低於PMMA Tg之溫度下受壓接合時，此結構深入PMMA軟化層中，PC奈米圓柱與PMMA藉分子擴散與結構嵌合提升接合強度。PC與PMMA間異質材料的接合強度也達1.20 MPa，遠比無奈米結構接合PC/PMMA的接合強度400 kPa為強，顯示以表面奈米結構於二氧化碳輔助熱融接合製程對提升接合強度的效果。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