The Effect of CaF ₂ on the Properties of High‐Thermal Expansion B ₂ O ₃ ‐Bi ₂ O ₃ ‐SiO ₂ ‐ZnO‐Al ₂ O ₃ /CaO Low‐Temperature Cofired Ceramic Composites

B 2 O 3 ‐Bi 2 O 3 ‐SiO 2 ‐ZnO‐Al 2 O 3 (BBSZA)/CaO composite is a kind of low‐temperature cofired ceramic (LTCC) material with low cost and high thermal expansion coefficient. Due to the unique grain structure of CaO, it is difficult to be wetted by commonly used glasses. In this work, we improved the comprehensive performance of BBSZA/CaO composites by adding a small amount of CaF 2 to wet the particles and relieve thermal stress. The influence of CaF 2 on the properties of the BBSZA/CaO composites was systematically investigated. The coefffcient of thermal expansion (CTE) of BBSZA/CaO with 0 wt% ~5 wt%CaF 2 was between 11.30 and 12.40 ppm/K, meeting the requirements for thermal matching of electronic devices. After adding 1 wt% CaF 2 , the thermal conductivity of the composite composite increased from 4.41 to 5.02 W m −1 K −1 , the bending strength increased from 78.58 to 103.25 MPa, and the density increased from 3.72 to 4.06 g/cm 3 . Meanwhile, the composite material with 1 wt% CaF 2 achieved a dielectric constant of 9.68 and a dielectric loss of 1.49 × 10 −3 at 16 GHz. The BBSZA/CaO/CaF 2 composite material has achieved a synergistic optimization of high thermal expansion coefficient, high thermal conductivity and high mechanical strength, and can meet the high thermal expansion requirements of electronic devices, demonstrating broad application prospects.