Synthesis of Sn, Sn-Cu and Sn-Ag nanoparticles and fabrication of highly conductive ink for printed electronics

Abstract

Inkjet printing technology is currently attracting a great deal of attention because its process has the advantages of being fast, simple and inexpensive as compared with conventional vacuum deposition and photolighographic. The search for conductive ink materials that can be used in inkjet printing has focused on several materials, particularly molten metal, conductive polymer, and metal nanoparticles. Of these, metal nanoparticles are considered the most promising candidate for inkjet printing material. Ink made of metal nanoparticles can be operated at room temperature; it also has better conductivity (typically $10^4-10^5$ S/cm) than conductive polymer (typically $10^2-10^3$ S/cm). Due to the high conductivity and thermal stability, noble metals such as Au ($T_m$ = 1064℃, melting point) and Ag ($T_m$ = 961℃) nanoparticles have been widely studied for application to inkjet printing materials. However, the high cost and the high sintering temperature tend to hinder the use of these noble metals because the high melting temperatures induce energy consumption, substrate warpage, and thermal stress problems. In this regard, Sn is a good alternative material because it has a lower melting temperature (232℃) and a significantly lower cost than noble metals. Hence, Sn based nanoparticles, Sn, Sn-Cu and Sn-Ag nanoparticles were synthesized using a modified polyol process for inkjet printing materials. In chapter 2, monodispersive Sn-Cu nanoparticles were synthesized. By controlling the size and the compositin of Sn-Cu nanoparticles, a significant melting temperature depression of 30.3℃ was achieved. In chapter 3, a monodispersive sug-gram of Sn nanoparticles were successfully synthesized. The yield of Sn nanoparticles was higher than 80% (0.6g) and melting temperature depressed up to 56.8℃ by reducing the size of Sn nanoparticles. In chapter 4, conductive Sn ink was fabricated by controlling the viscosity and the surface tension. After the surface treatments such as...