Electrodes fugitive

Broadly speaking there are two significant manufacturing processes, the dry and the wet there is a third, the fugitive electrode process, developed to replace the expensive palladium-containing electrodes with a cheap metal, but it has ceased to be of any commercial significance. The steps in the various processes are summarized in Fig. 5.12. 

With reductions in ceramic sintering temperature, the cost of electrodes has been reduced by the use of Ag-Pd alloys, typically 70at.% Ag/30at.% Pd. The reduction in palladium content is limited to about 15 at.% because at lower levels silver migration becomes a problem. The drive to lower cost has led to efforts to avoid it entirely. One approach is based upon the injected or fugitive electrode (see Section 5.4.3 and Fig. 5.12) and the other on the use of the base metals nickel or copper for the electrodes (BME) combined with dielectrics resistant to the reduction firing necessary to retain the electrodes in the metallic state. 

Although the fugitive electrode approach is viable it is presently little used, if at all. In contrast BME technology presently accounts for about 50% of MLCC production. 

Electrical Water-soluble, fugitive binder for microporous battery and fuel-cell electrodes... 

Screen printing Ag-Pd electrodes. The cost of the electrode materials is a big concern. In fact, the noble metals account for more than half the cost price of MLCCs. Alternative nonprecious metals such as copper and nickel have been used. A different approach to reducing the cost of metallization is the fugitive electrode process. The electrodes are made of carbon, which is removed during sintering in air. The remaining cavities are then pressure infiltrated with either molten lead or a tin-lead alloy to produce the electrodes. 

Sintering HA powders, or a mixture of suitable reactant powders, uses naphthalene particles that volatilize during heating to create an interconnected porous network. Similar approaches have been used to produce foam glass (Section 26.9) and in the fugitive electrode method of producing multilayer chip capacitors (MLCCs) (Section 31.7). 

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