Glass-free LTCC microwave dielectric ceramics

The sintering behavior, microstructure and microwave dielectric properties of complex pyrophosphate compounds AMP2O7 (A = Ca, Sr; M = Zn, Cu) were investigated in this paper. All compounds could be densified below the temperature of 950 °C without any glass addition, and exhibit low permittivity (ɛr < 8), high Q × f value and negative temperature coefficient of resonant frequency. The Q × f value was discussed from the point of view of bond strength. The chemical compatibility with silver and copper was also investigated. All compounds seriously react with silver at ∼700 °C. However SrZnP2O7 could be co-fired with copper in reduced atmosphere. The microwave dielectric properties of SrZnP2O7 sintered at 950 °C in reducing atmosphere are: ɛr = 7.06, Q × f = 52781 GHz, τf = −70 ppm/°C. In terms of its lower sintering temperature, chemical compatibility with copper and good microwave dielectric properties, SrZnP2O7 ceramic is very promising for low temperature co-fired ceramic (LTCC) applications.