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|Low Fired X7R Dielectrics Buried into LTCC Substrates|
|Keywords: LTCC, X7R-Dielectric, Co-Firing|
|Low Temperature Co-fired Ceramics (LTCC) must be sintered at temperatures below 900 °C, which allows the use of low resistivity and low cost silver conductors. Integration of passive components such as capacitors into the LTCC substrate eliminates many solder joints and wire bonds and is required for miniaturization of electronic packaging. However, commercially available barium titanate ceramic powders which are mostly used for capacitor manufacturing are sintered at temperatures of above 1250 °C. Hence, it is required to develop capacitor materials, which can be fully densified at sintering temperature of 900°C. Therefore, the influence of different additives on sintering behaviour and dielectric characteristics of commercially available BaTiO3 was tested. Due to addition of minor amounts of suitable additive combinations to BaTiO3 powder the sintering temperature was reduced to 900 °C. Excellent densification (more than 98 % of theoretical density) and good dielectric properties were achieved after sintering at 900 °C for 2 hours. Dielectric properties can be improved by modifying the composition of sintering additives and addition of further dopants. The low sintering temperature of newly developed capacitor material allows a co-sintering with pure silver electrodes. No interfacial reaction between silver electrodes and ceramics was observed by microprobe analysis. The dielectric constants of about 1200 to 3000 and the dielectric losses of about 0.008 to 0.02 were measured (f = 1 kHz , T = 25 °C). The new capacitor materials satisfy X7R capacitor performance characteristics. Furthermore, the capacitor tapes were laminated with dielectric LTCC tapes and subsequently sintered at 900 °C for 2 h. Densification and dielectric properties of embedded multi-layer capacitors in LTCC were investigated.|
|Hamid Naghib-zadeh, Ph.D. Student
Federal Institute for Materials Research and Testing (BAM)