The electrical and microstructural characteristics of thick-film PTC thermistors with high positive temperature coefficients of resistivity, fired either on “green” LTCC) substrates or buried within LTCC structures, were evaluated.. The results show that PTC thermistors cofired on LTCC substrates can be used for temperature sensors in MCM-Cs as well as in MEMS structures. However, when the thermistors were buried in the LTCC substrates, the LTCC structures delaminated during firing and blisters formed, leading to high sheet resistivities and high noise indices.
COBISS.SI-ID: 20533799
Thick film pastes based on piezo electric PZT materials were prepared. Pastes were printed and fired on alumina and LTCC substrates. Dielectric, ferroelectric and piezoelectric characterustics were evaluated. Measured piezoelecztic constants as well as dielectric constants of films on LTCC substrates were lower than constants of films on alumina substrates. A study of interactions between LTCC substrates indicated that this is due to the diffusion of the glass phase from LTCC into PZT films and the formation of secondary phases.
COBISS.SI-ID: 21319975
Piezoelectric thick films based on Pb(Zr,Ti)O3 (PZT) were prepared on different types of LTCC. The results obtained on alumina substrates were used as a reference. The microstructures of the cross-sections were investigated using SEM and EDS analysis. The dielectric and piezoelectric characteristics of the PZT fired on the LTCC substrates deteriorated in comparison to the samples on alumina, due to interactions between the LTCC substrate and the PZT layer. Lower values indicate the formation of phases with a low permittivity during firing.
COBISS.SI-ID: 21623847
Many of applications demand possibility of structuring of buried channels or cavities within LTCC ceramics. To obtain these buried structures without delamination and/or sagging during lamination processes (compressing of green LTCC foils at around 70°C) so called sacrificial layers are often used. The sacrificial material based on graphite, either pastes or tapes, were evaluated. The thermo gravimetrical analysis (TGA) was used to establish the starting temperatures of oxidation and burn-out profiles. Realised structures were investigated by SEM and EDS.
COBISS.SI-ID: 22627879
The electrical and microstructural characteristics of thick film NTC thermistors fired either on LTCC substrates or buried within LTCC structures were evaluated. The sheet resistivities and beta factors were higher than these of thick-film thermistors on alumina substrates. The increase of the sheet resistivities was attributed to the diffusion of the glass phase from the rather glassy LTCC substrates into the NTC thermistors. The re results show that the evaluated NTC thermistors on LTCC substrates can be used for temperature sensors in MCM-Cs as well as in MEMS LTCC structures.
COBISS.SI-ID: 22815783