Chemical Interactions of Au and Ag Conductors in Ceramic Based Electronic Packages

Abstract

ABSTRACTIn electronic packages consisting of glass-alumina composite dielectric layers and thick film conductors, Au and Ag conductors on separate layers may alloy. Alloys are formed by Ag+ ion diffusion through the intervening dielectric. The extent of alloy formation is dependent upon whether the Au and Ag conductors are electrically isolated or connected. When the Au and Ag conductors are electrically isolated, alloying is self-limiting and occurs by reduction of Ag+ ions and dissolution of the metallic Ag into the Au. In this case, the reduction of Ag+ is accompanied by oxidation of the lattice oxygen anions forming O2 gas which accumulates to form blisters. If the Au and Ag conductors are electrically connected, then the alloying is not self-limiting and occurs without the formation of O2. In this study, we quantitatively characterize the alloying reactions which occur during firing and propose mechanisms for specific dielectric and conductor packages. The presence of these alloying reactions can affect the reliability and the performance of the electronic ceramic package.