Ag precipitation at the free interface of multilayer NiCuZn ferrites/LTCC components

The diffusion and precipitation of silver and copper in low-dielectric-constant low temperature cofired ceramics (LTCC) for multilayer NiCuZn ferrites/LTCC components are investigated in this study. Ag precipitation is formed at the free interface between NiCuZn ferrites and LTCC for multilayer NiCuZn ferrites/LTCC components after cofiring. During the heating stage Cu+ will segregate into the grain boundary from the NiCuZn ferrites due to the low oxygen partial pressure inside the sample and then dissolve into LTCC near the interface between NiCuZn ferrites and LTCC. Cu+ in glass would diffuse from the interior toward the surface and become oxidized into Cu2+ or precipitated as the CuO phase at the surface. To maintain charge neutrality this process requires an outward diffusion of Cu+ and Ag+ from the interior toward the free surface. The reduction of Ag+ into Ag on the free surface is accelerated by Cu+ oxidation.