Creating Single‐Crystalline β‐CaSiO3 for High‐Performance Dielectric Packaging Substrate

Abstract β‐CaSiO 3 based glass‐ceramics are among the most reliable materials for electronic packaging. However, developing a CaSiO 3 glass‐ceramic substrate with both high strength (>230 MPa) and low dielectric constant (<5) remains challenging due to its polycrystalline nature. The present work has succeeded in synthesizing single‐crystalline β‐CaSiO 3 for a high‐performance glass‐ceramic substrate. This is accomplished by introducing Al 3+ into the CaO‐B 2 O 3 ‐SiO 2 glass system, and by optimizing the sintering condition. Al 3+ doping facilitates a heterogeneous network structure that energetically favors the precipitation of polycrystalline particles, including nanosized β‐CaSiO 3 crystals and sub‐nanosized α‐CaSiO 3 crystals. As the sintering temperature increases, the nano α‐CaSiO 3 crystals (2–10 nm) are gradually absorbed by the β‐CaSiO 3 crystals. Through atomic rearrangement, α‐CaSiO 3 crystals transform into micrometer‐sized single crystal β‐CaSiO 3 (1–2 µm) with layered structure. The low temperature co‐fired β‐CaSiO 3 glass‐ceramics exhibit exceptional properties, including a low dielectric constant of 4.04, a low dielectric loss of 3.15 × 10 −3 at 15 GHz, and a high flexural strength of 256 MPa. This work provides a new strategy for fabricating high‐performance single‐crystalline glass‐ceramics for electronic packaging and other applications.