Sintering and applications of inkjetprinted silver nanoparticles
The presented thesis addresses the composition, inkjet-printing and low-temperature sintering of the currently predominantly used silver nanoparticle based inks and their application in flexible electronic devices. The concept of stabilization of silver nanoparticles in the ink by organic compounds like polymers or amphiphilic molecules requires the removal of these organics in order to introduce electrical conductivity of the patterns after printing and drying. To develop a manufacturing process that is compatible with thermo-sensitive substrate materials as well as the short processing times that are required for high-throughput manufacturing, several non-conventional sintering methods like plasma sintering and intense pulsed light sintering were investigated. For the improvement of ink formulations and sintering technologies, an exact understanding of the sintering mechanisms is of critical importance. On account of this requirement, the thermal sintering behavior of a silver nanoparticle ink was investigated in detail. Subsequently, the experimental results were used as input parameters for a sintering and resistivity model. Another focus of this thesis was the improvement of argon plasma sintering in terms of reduction of the technical complexity, substrate friendliness and processing time. For that purpose, the sintering of several silver nanoparticle inks via atmospheric pressure plasma devices was investigated. Eventually, the implementation of inkjet-printed and low temperature sintered silver patterns into flexible electronic applications was investigated by the manufacturing of a biochip platform as well as ultra-high frequency (UHF) electromagnetically active devices.
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