INTERACTION OF AG PD METALLIZATION WITH LEAD AND BISMUTH OXIDE-BASED FLUXES IN MULTILAYER CERAMIC CAPACITORS

An ongoing challenge for future developments in high-performance ceramic multilayer capacitors and integrated ceramics is to reduce the internal electrode cost and thickness without sacrificing yield or reliability. Kev to these developments is a thorough understanding of the interactions which occur between flux-sintered dielectrics and low-cost, Ag/Pd electrodes. In this paper we present results on the phase equilibria of Ag/Pd electrode systems with Bi2O3 and PbO fluxes. The conditions under which the bismuth reaction occurs and reactions in the Pd-PbO system are reported. Results show that the equilibrium phases which form depend strongly upon the Ag/Pd ratio and temperature. These phases include PdBi2O4, Pd(Bi), PdPbO2, Pd(Pb), and PbPd3. The PdBi2O4 and PdPbO2 phases decompose when PdO destabilizes, resulting in a series of reactions which result in oxygen evolution and partial melting of components. The exact phase relations of the Ag/Pd-Bi2O3-O2(air) system and Ag/Pd-PbO-O2(air) system have been established for the first time and are discussed in terms of their impact on multilayer, cofired structures.