Effect of Frit Added in Ag-Paste on Warpage of Multilayered Glass-Ceramics Substrate

The effect of frit added in Ag-paste on warpage of co-firing multilayered glass-ceramics substrate was investigated. BaO-Al2O3-SiO2 system glass was used as the added frit. The difference of shrinkage between Ag paste and the glass-ceramics increased with increasing the frit added in the Ag-paste. But, the warpage of co-firing multilayered substrate reduced with increasing the frit added. From these results, it was found that the warpage in our system was not due to the shrinkage mismatch between the substrate and the inner conductor materials, but it was caused by the change of glass-ceramics sintering behavior according to diffusion of silver, as previously reported by other investigators. Electron probe micro-analysis (EPMA) revealed that the glass layer suffered modifications from the added frit formed around the Ag-inner conductor, and that this layer prevented Ag from diffusing into the glass-ceramics. Therefore, the sintering behavior of the glass-ceramics in the neighborhood of the Ag-inner conductor did not change locally, and the warpage of cofiring substrate reduced with increasing the frit added in Ag-paste.