| Summary: | 博士 === 國防大學理工學院 === 國防科學研究所 === 99 === In this study, a low-temperature, low-cost technique for fabricating patterned metallic thin films was developed. A catalytic precursor pattern was formed by inkjet printing thermo-responsive Pd nanocomposite (Poly(St-co-NIPAAm)Pd) on the substrate, and then metal was electrolessly plated to complete the metallization.
First, thermo-sensitive copolymer of uniform sizes was made with both styrene monomer and NIPAAm monomer by free radical polymerization. Poly(St-co-NIPAAm)/Pd was prepared via self-reduction of palladium ions by St-co-NIPAAm oligomer without using any reducing agent or surfactant. It was shown that Pd was reduced by the chain-end sulfate groups of PS when copolymer reacted with the metallic ions, and the hydrophilic NIPAAm plays the role of a dispersing agent to prevent agglomeration. This process provides a fast and convenient method for synthesizing thermo-responsive noble metal nanocomposites.
In the first part of this study, the preparation of thermal-responsive copolymers was the major issue. The effects of different processing parameters on the synthesis of copolymers were analyzed. Characterizations with GPC, NMR, FT-IR etc. confirmed the successful synthesis of copolymer, which was then used as the reducing agent to form Pd nanoparticles for the application to inkjet printing. The results confirmed that the catalytic Pd nanocomposite ink exhibits many desirable properties including thermal-responsivity, good stability, high catalytic activity, and good adhesion. Thus it can satisfy the requirements for inkjet printing. The properties of Poly(St-co-NIPAAm)Pd were analyzed with UV-vis, FT-IR, QCM, XRD, TEM, etc.
The second part of this study focused on metallization using electroless deposition. The Pd ink was printed as a catalyst layer for subsequent electroless deposition. The thermo-responsive catalyst was converted from hydrophilic to hydrophobic when the electroless deposition temperature was above LCST. Therefore it can strongly adhere to the substrate during electroless plating and thereby a continuous metal pattern can be formed on the catalyst layer. The metallic pattern was characterized with SEM, four-point probe, EDS, and tape test. In addition, the morphology of cross section was observed by TEM in order to understand the mechanism for metallization.
In the third part of this study, the printing parameters were studied and some applications were demonstrated. The printing parameters such as printing voltage and droplet spacing were studied in order to find the optimum conditions. Three different applications were successfully demonstrated: RFID, PTH, and OTFT. In the part of RFID, flexible RFID antenna was fabricated. The process is fast and low-cost, and the printed antenna shows good responsive properties. For the application to PTH, Pd nanoparticles also show good adhesion with the PCB substrates due to the reduction of LCST when the Poly(St-co-NIPAAm)Pd was immersed in the plating solution with high concentration of OH- ions. By this way, through holes were successfully metallized, and the result passed stringent industrial test standard. Finally, the printed metallic patterns were used as electrodes for OTFT, and the results verified that the OTFT had good properties for electron transport and device operation.
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