We have been working on the development of Ag paste which is used for high-frequency components for some time, focusing especially on improving their characteristics. We have learnt from our thorough study involving a series of experiments and evaluations that the characteristics of the Ag paste could be improved considerably by adapting the conventional technology of heat-resistance treatment for Ag powder. Our study concentrated on the characteristics of the Ag paste particularly in connection with solder leaching, adhesive strength (against aging, heat cycle, high temperature and high humidity) and migration. We have managed to actualize the improvement on the characteristics of the Ag paste to be as beneficial as or even superior to those of more widely used Ag/Pd (=80/20) and Ag/Pt (=99/1) pastes. Another fact, which our study indicates, is that the application of heat-resistance treatment to Ag powder helps to suppress solder leaching and migration. Our study also revealed that the adhesive strength of Ag paste could be intensified by mixing metal oxide dopants in with the heat-resistance treatment ingredients. It is understood that the application of this coating mixture boosts the chemical bonding action. According to our study, a low degree of sheet resistance is retained by the Ag electrode, for which our newly developed Ag paste has been adopted, as found with currently used Ag electrodes. However, the fact that the new-type Ag paste is free from glass flit may bring a further improvement to the high-frequency characteristics of Ag electrodes. Consequently, the new-type Ag paste is suitable to adopt for manufacturing terminal electrodes and surface electrodes, which are used for high-frequency components and LTCC (Low Temperature Co-fired Ceramics).
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