Abstract
The thesis describes the development of a novel LTCC material system for RF and
microwave telecommunication purposes.
The work has been divided into three parts. In the first section, the
compositional and firing properties of this novel LTCC dielectric have been
studied as well as its thermomechanical and dielectric properties. The second
section describes the multilayer component preparation procedure for the ceramic
material including tape casting and lamination parameters and the selection of
the conductor paste. In the last section, the novel LTCC material system has been
used to demonstrate its properties in RF multilayer resonators and a bandpass
filter.
The dielectric material for the novel LTCC system was prepared using magnesium
calcium titanate ceramic, the firing temperature of which was decreased to
900°C
by the addition of a mixture of zinc oxide, silicon oxide and boron oxide. The
powder was made without any prior glass preparation, which is an important
process advantage of this composition. The fired microstructure was totally
crystalline with high density (3.7 Mg m-3) and low
porosity (0.5 %). The mechanical properties were virtually identical to the values of the commercial
LTCCs, but the higher thermal expansivity makes it most compatible with alumina
substrates. The dielectric values were also good. The permittivity was 8.5 and
the dissipation factor (0.9·10-3 at 8 GHz) less
than that of the commercial
LTCCs. Furthermore, the temperature coefficient of the resonance frequency was
demonstrated to be adjustable between the range of +8.8 ... -62 ppm/K with a
simple compositional variation of titanium oxide.
The slurry for the tape casting was prepared using poly(vinyl butyral) -base
organic additives and the 110 μm thick tapes had a smooth surface (RA < 0.5
μm).
The multilayer components were prepared using 20 MPa lamination pressure,
90°C
temperature and 1 h dwell time. The most suitable conductor paste for this
composition was found to be commercial silver paste (duPont 6160), which produced
satisfactory inner and outer conductor patterns for multilayer components.
Finally, resonators with a resonant frequency range of 1.7 ... 3.7 GHz were
prepared together with a bandpass filter suitable for the next generation of
telecommunication devices. This demonstration showed the potential of the
developed novel LTCC material system at high RF frequencies.
| Identifer | oai:union.ndltd.org:oulo.fi/oai:oulu.fi:isbn951-42-6553-X |
| Date | 07 November 2001 |
| Creators | Jantunen, H. (Heli) |
| Publisher | University of Oulu |
| Source Sets | University of Oulu |
| Language | English |
| Detected Language | English |
| Type | info:eu-repo/semantics/doctoralThesis, info:eu-repo/semantics/publishedVersion |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess, © University of Oulu, 2001 |
| Relation | info:eu-repo/semantics/altIdentifier/pissn/0355-3213, info:eu-repo/semantics/altIdentifier/eissn/1796-2226 |
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