Novel Lead-free Glass/Ceramics System with Low Permittivity, Low Loss for LTCC Application

The lead‐free, low‐softening point ZnO‐Bi2O3‐B2O3 glass with low permittivity, low loss and small coefficient of thermal expansion was prepared by melt‐quenching method. ZnO‐Bi2O3‐B2O3 glass + Al2O3 system were prepared below 850°C by the conventional ceramic route. Sintering behavior and microstructure of this system were investigated using X‐ray diffraction, differential scanning calorimetry, and scanning electron microscopic techniques. Results revealed that ZnO‐Bi2O3‐B2O3 glass and Al2O3 reacted during the firing process, which led to the formation of ZnAl2O4. Glass concentration needed to be 65 wt% for better densification. The dense system sintered at 825°C for 30 min exhibited good dielectric properties: small permittivity of 5.73 and low loss tangent of 8.94 × 10−4 at 1 MHz. Its coefficient of thermal expansion (5.57 × 10−6/K) well matched to that of GaAs chip (5.6 × 10−6/K). The bending strength was also characterized (129.9 MPa). The prepared system was suitable for LTCC application.