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- 2015 (2) (entfernen)
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- Englisch (2)
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- LTCC (2) (entfernen)
This paper presents, the investigation of tunable components based on LTCC technology, implementing ferroelectric tunable thick-film dielectric. The tunable loaded line phase shifters are fabricated with metal-insulator-metal (MIM) varactors to demonstrate the capabilities of this method for packaging of the tunable components. The MIM varactors consist of one tunable dielectric paste layer that is printed between two silver layers. The tunable ferroelectric paste is optimized for LTCC sintering temperature around 850°C. The phase shifters are fabricated in two different process. They were achieved a figure of merit of 24°/dB (phase shift 192°) at 3 GHz and 18°/dB (phase shift 98°) at 4.4 GHz by using seven unit cells that each unit cell consisting of two MIM varactors.
Pressure-assisted sintering (PAS) is an established procedure for the production of low-temperature cofired ceramics (LTCC) without lateral shrinkage and minimal shrinkage tolerances for automotive and high-frequency applications. To develop a feasible model for the prediction of densification during that process, master sintering curves (MSCs) for the commercial LTCC DP951 were generated from thermomechanical analysis (TMA) data in the pressure regime from 2 to 500 kPa. Strain mainly related to creep deformation of the LTCC was identified by evaluation of the strain rate and was discarded for the determination of MSC parameters. It was found that no creep occurred at any pressure up to a relative density of 0.9. Different pressure levels can be modeled with the same activation energy of 400 kJ/mol. Densification curves predicted by the model were in good agreement with experimental data. Based on MSCs, the pressure-assisted master sintering surface was compiled to illustrate the influence of pressure on densification. The results show that the MSC approach is a suitable method to feasibly predict the densification of LTCC during PAS.