Self-constrained sintering of Al₂O₃/glass/Al ₂O₃ 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≤D₅₀≤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 (ε_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.