INTERACTIONS BETWEEN LEAD-OXIDE AND CERAMIC SUBSTRATES FOR THICK-FILMTECHNOLOGY

This paper deals with the mechanisms and kinetics of interactions betw een screen printed and fired PbO layers and ceramic substrates: alumin a and beryllia. The interaction with alumina occurs via two main proce sses: (i) a reaction between PbO and Al2O3 grains, which induces the f ormation of a crystalline phase, Pb2Al2O5; and (ii) an interdiffusion process involving Pb and the intergranular amorphous phase in the cera mic substrate. This latter process results in a compositional change o f the intergranular phase at considerable depths inside the ceramic su bstrate, as well as in the formation of a high lead glass layer on the substrate surface, Since PbO is not completely reacted, the Pb penetr ation in the ceramic is diffusion limited (penetration depth w approxi mate to t(d)(1/2) where t(d) is the reaction time) with an activation energy of 1.20 +/- 0.05 eV. The ceramic microstructure significantly a ffects the interaction processes.