Study On Technological Properties Of High-performance Metallo-organic-decomposition Silver Paste Without Solid Or Particle Phase

In recent years, the continuing drive for higher integration and flexibility in microelectronic devices is pushing the corresponding fabrication technology to higher level. Direct-writing technology with the advantages of masklessness, simple process and high flexibility has been widely applied in the area of electronic devic manufacturing s. It is very difficult for the conventional pastes to meet the processing requirements of manufacturing high-performance electronic products in direct-writing process because of their larger functional-phase particles and higher sintering temperatures. However, high-performance metallo-organic-decomposition silver pastes have many advantages to the conventional pastes, which may overcome the shortcomings of the pastes used for direct writing. The concerned research has become a hot pot in the field of electronic pastes applied in the direct-writing technology.In this dissertation, a metallo-organic-decomposition silver thick-film paste without solid or particle phase was developed by th use of silver alkylcarbamates ((CnH2n-1NHCOO)2Ag, n≤4) as the precursor of functional phase. The precursor was able to produce silver nanoparticles with electrical conductibility during post heat-treatment (sintering and/or laser irradiation). Besides the functional phase such as silver nanoparticles, the paste containes other components such as thickening agent (ethyl cellulose) and leveling agent.It was found that the paste was a non-Newtonian fluid with viscosity significantly depending upon the content of the thickening agent. Furthermore, the paste can maintain a good stability during storage.The experimental experiments showed that the paste had the optimal sintering process that the paste was heated to the final temperature in oxygen ambient at the rate of 10℃/min, then sustained 1h, and then cooled to room temperature. The paste with a solid content of 10-20 wt.% was found to have a volume electrical resistivity in the order of 10-5 ?·cm after it was sintered 1h at the temperature of 180℃. The cohesion strength within the sintered paste and the adhesion strength between the sintered paste layer and the substrate were tested according to test method B of the ASTM (American Society for Testing and Materials) Standard D 3359-08. It showed that the cohesion and adhesion strengths met the highest grade (5B) according to the standard when organic materials (e.g.: polyimide) were used as the substrate.After the paste was applied in micro-pen/micro-spring/laser micro-cladding processes, 60μm and 20μm resolution of line width was obtained, respectively. The obtained line had a smooth edge and no gas holes and cracks can be observed in the sintered paste layer.