LTCC system with new high-ɛr and high-Q material co-fired with conventional low-ɛr base material for wireless communications

The authors have developed a new LTCC material with characteristics of high dielectric constant (ɛr), high quality factor (Q) and low temperature coefficient of capacitance (TCC). This material can be co-fired with a conventional base LTCC material and buried resistors with low temperature coefficient of resistance (TCR). The base material which consists of Al2O3 filler and glass, has low ɛr of 8.7 at 3 GHz. The newly developed LTCC material, which consists of Ba–(Re)–Ti–O filler, Al2O3 filler, and glass, has the following characteristics of ɛr of 15.1, Q of 900 at 3 GHz, and TCC of −10 ppm/K. The buried resistors consist of RuO2 and glass. Two different LTCC materials, a resistor material and a silver electrode paste can be co-fired as multi-layer substrates and are regarded as a new LTCC system.Constrained sintering could be applied to this LTCC system and the dimensions of substrates could be controlled with quite high accuracy. This LTCC system is expected to contribute to further miniaturization of RF circuits and the reduction of electrical loss.