Self-constrained sintering of Al2O3/glass/Al2O3 ceramics by glass infiltration

Though need for precise alignment of interlayer patterning in LTCC application, there have been few reports about zero-shrinkage sintering techniques. In this study, ceramic substrate with minimal x–y shrinkage was prepared by glass infiltration method with ‘Al2O3/glass/Al2O3’ structure. Glass infiltration into alumina particle layer was observed with variation of both sintering temperature (700 ≤ T sint. ≤ 900 °C) and alumina particle size distribution (0.5 ≤ D 50 ≤ 1.8 μm). Since glass had low viscosity enough to infiltrate at 700 °C, infiltration started at that temperature and infiltrated up to 20 μm or so with temperature increase, but infiltration depth did not increase noticeably above 750 °C. Based on these results, when sintered at 900 °C with controlled sheet thickness of both glass and alumina, the shrinkage in x–y direction was calculated as less than 0.2%, with 40% in z direction. Dielectric constant (ɛ r) measured 6.19 with quality factor (Q) of 552 at 1 GHz of frequency. From these results, it is thought that zero-shrinkage ceramic substrates would be obtained without de-lamination.