Design and optimization of cordierite-based glass–ceramic LTCC millimeter-wave materials

Cordierite ceramics, with a low dielectric constant ([Formula: see text]–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 [Formula: see text] 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 [Formula: see text] [Formula: see text]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[Formula: see text]wt.% BBS exhibited a dielectric constant of ∼6.7, a dielectric loss of [Formula: see text] at 11.7[Formula: see text]GHz, a [Formula: see text] of [Formula: see text] [Formula: see text]ppm/ ∘ , a Vickers hardness of 757[Formula: see text]HV, and a coefficient of thermal expansion of [Formula: see text]C, indicating its potential for LTCC-oriented high-frequency packaging applications.