Design and Optimization of Cordierite-Based Glass-Ceramic LTCC Millimeter-Wave Materials

Cordierite ceramics, with a low dielectric constant (ε r = 4-6), are considered promising substrate materials for LTCC-oriented high-frequency packaging. However, systematic investigations on the influence of glass additives on the densification behavior and dielectric/thermal properties of cordierite-based ceramics remain limited. In this study, three types of R-B 2 O 3 -SiO 2 (RBS, where R = ZnO, CaO, and Bi 2 O 3 ) glass powders were employed as sintering aids to examine their influence on the sintering behavior, mechanical properties, dielectric properties, and thermal performance of Mn-Zn-modified cordierite-based ceramics. The results show that the incorporation of RBS glass significantly reduced the optimal sintering temperature of cordierite ceramics from 1250°C to 950°C. Among the tested additives, the Bi borosilicate glass (abbreviated as BBS) exhibited the most effective sintering promotion. Interestingly, an anomalous minimum in the shrinkage.composition curve was observed at x = 14 wt.% BBS. Analysis of the real-time shrinkage behavior, combined with the Frenkel and Mackenzie-Shuttleworth (M-S) viscous-flow models, suggests that this anomaly is associated with an increase in the effective viscous-flow resistance caused by premature liquid-phase encapsulation and pore closure. At 950°C, the cordierite-based composite with 16 wt.% BBS exhibited a dielectric constant of ~6.7, a dielectric loss of 1.024 × 10 -3 at 11.7 GHz, a ι f of ~ -10.19 ppm/ÀC, a Vickers hardness of 757 HV, and a coefficient of thermal expansion of 3.83 × 10 -6 /°C, indicating their potential for LTCC-oriented high-frequency packaging applications.