LTCC materials for high density multilayer interconnect

A low temperature co-fired ceramic (LTCC) materials containing ceramic fillers and flux was developed with a matched silver conductor paste. They were used to fabricate multilayer chip band pass filters for the RF (radio frequency) circuits of the wireless telecommunication terminals. The material was sintered at 860 degreesC in 20 minutes to a density of 3.5g/cc. The properties of the densified ceramic are k = 7.8, Q > 500@2.1GHz, CTE = 4.5 ppm/degreesC, bending strength similar to 2000 kg/cm(2), and tau (f)= -8.7 ppm/degreesC. A multilayer band pass filter for the GSM1800 cellular radio was designed and fabricated. The size of the filter was 4.5mmx 3.2mmx 2.0mm. The properties of the fabricated filter are f(0)= 1873 MHz, bandwidth similar to 200MHz, insertion loss=0.52 dB, ripple < 0.5dB, attenuation > 35dB at f(0)- 470MHz. SEM and EDX were used to verify a limited diffusion of inner silver electrode during sintering process. This LTCC material system is suitable for high-density multilayer interconnect for wireless telecommunication as well as other applications.