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Thick film superconductors with the nominal composition Bi2Pb0.5Sr2Ca2.5Cu3.5Ox were fired on stainless steel substrates and on alumina substrates covered with silver or gold thick film conductors. Films on stainless steel substrates were semiconducting due to reaction between the superconducting film and oxidised chromium and iron from the steel. Tc(R=0) of films on silver was between 80 K and 90 K while Tc (R=0) on gold was below 60 K. The low Tc (R=0) of films on gold is attributed to the interaction between the gold layer and copper from the superconductor.

To find properties of screen printed PZT (PbZr_0.53Ti_0.47O₃ with 6 per cent of PbO and 2 per cent of Pb₅Ge₃O₁₁) thick films layers on LTCC substrate.

The influence of PZT firing time and electrode materials on electrical characteristics and microstructure were examined. A scanning electron microscope (SEM) equipped with an energy‐dispersive X‐ray (EDS) analyser was used for the microstructural and compositional analysis.

Microstructural and compositional analyses have shown the diffusion of SiO₂ from LTCC into PZT layers and the diffusion of PbO in the opposite direction. SiO₂ presumably forms low permitivity lead based silicates in PZT layer. The new phase deteriorates the piezoelectric properties. The amount of diffused materials was dependent upon the electrode material and increased with increasing firing time. Better properties, i.e. higher remanent polarisation and dielectric constant were achieved for samples with PdAg electrodes and shorter firing time.

New information on electrical and microstructural properties of thick film PZT made on LTCC substrate.

Interactions between stainless steel and silver and gold based thick film conductors and YBa2Cu3O7 thick film superconductors were studied by SEM and EDX. The stainless steel reacted with the superconducting layer, forming a Ba‐Fe‐O compound on the interface, while BaO‐depleted YBa2Cu3O7 compound transformed into insulating Y2BaCuO5 compound. When YBa2Cu3O7 is fired on a gold thick film conductor, a thin layer of Y2BaCuO5 compound forms between the conductor and the superconducting film. In the case of a thin Ag conductor, BaO diffused through the silver film and reacted with alumina ceramic to the depth of a few μm. When a thicker silver layer (40–50 μm) was used, diffusion did not occur.

A superconducting material with a composition Y1−xBa2Cu3O7−3/2x − x/2 Bi2O3 (x = 0·1 and 0·2) was synthesised. The influence of Bi2O3 additions on sintering was studied. Preliminary investigations of the Bi‐Sr‐Ca‐Cu‐O system were also made. Thick film pastes, prepared from Y1−xBixBa2Cu3O7 compositions, from the compound YBa2Cu3O7 with 10 w/o addition of Bi2CuO4 and from two compositions in the Bi‐Sr‐Ca‐Cu‐0 system, were fired on Al2O3 and ZrO2 substrates. All thick film materials based on YBa2Cu3O7 compound were superconducting at temperatures above 77 K when fired on ZrO2 substrates, while only a material with the starting composition Y0·8Ba2Cu3O6.7 − 0·1 Bi2O3 reached zero resistivity above 77 K on Al2O3 substrates. Tc (onset) of samples based on the YBa2Cu3O7 compound was around 95 K, and of samples from the Bi‐Sr‐Ca‐Cu‐O system between 95 and 100 K.

Thick film resistor materials' microstructure, sheet resistivity and temperature coefficient of resistivity during the firing process in the temperature range between 350°C and 950°C were investigated. During firing the sheet resistivities at first decrease because of evaporation and/or oxidation of the organic phase and later, at higher firing temperatures, increase due to sintering of the glass phase and the rearrangement of conductive particles. The TCR is negative for firing temperatures below 450°C, due to the presence of partly pyrolysed organic vehicle, and positive for higher firing temperatures.

A superconducting material with the composition YBa1.8Pb0.2Cu3O7 was synthesised. The influence of PbO addition on the sintering and formation of the superconducting compound YBa2Cu3O7 was investigated. A thick film paste, prepared from prereacted material and an organic vehicle, was fired on Al2O3 and ZrO2 substrates. The resistivity of samples on ZrO2 substrates decreased to zero around 90 K, while samples on Al2O3 substrates did not reach zero resistivity until 77 K, which is probably due to the differences in thermal expansion coefficient between Al2O3 and the superconducting material. Interactions between Pt alloy based thick film conductors and superconducting material were studied.

The direct overlapping of thick film NTC thermistors and resistors was attempted to enable the trimming of NTC thermistors to relatively narrow tolerances with little influence on beta factors. Different combinations of 1 kohm/□ thick film NTC material (4993, Remex) and 1 and 10 kohm/□RuO2 and ruthenate based thick film resistors (HS‐80 series, Du Pont), fired either together or separately, were tested. The sheet resistivities, TCR and beta factors of these combinations were measured. Microstructures were investigated by SEM and analysed by EDS. The results, i.e., the large decrease of sheet resistivities (up to ten times) and a resistivity vs. temperature dependence which changed from negative to positive TCR for some combinations, indicate the interaction between NTC materials and resistors during the firing process. These interactions are more distinctive for materials fired together. In all cases the beta factors were lower than calculated. Based on these experiments, the ‘best’ thick film resistor paste for NTC/resistor combination (HS‐8041, Du Pont) was chosen. Several layouts with partially or entirely overlapped NTC thermistors/resistors were designed. Unprotected, glass protected or organic protected circuits were laser trimmed. The resistivities and beta factors were measured as a function of resistor geometries and laser cut lengths. The results obtained demonstrated that NTC thermistors, partially overprinted with an ‘ordinary’ thick film resistor, can be trimmed to tolerances around 0.5% without any special precautions during trimming.

Pressure‐sensor miniaturization requires high‐density packaging. This means that designers are constantly faced with all kinds of challenging, and sometimes impossible, requirements. In this paper we will present three examples with specific technologies and aspects of miniaturization and packaging. The first example is a pressure switch, the second a pressure sensor and the third a smart pressure sensor.

Aims to evaluate different thick‐film materials for use in strain sensors and temperature sensors on low‐temperature co‐fired ceramic (LTCC) substrates.

LTCC materials are sintered at the low temperatures typically used for thick‐film processing, i.e. around 850°C, The thick‐film resistor materials for use as strain and temperature sensors on LTCC tapes are studied. Thick‐film piezo‐resistors in the form of strain‐gauges are realised with 10 kΩ/sq. 2041 (Du Pont)and 3414‐B (ESL), resistor materials; thick‐film temperature‐dependent resistors were made from PTC 5093 (Du Pont), and NTC‐4993 (EMCA Remex) resistor materials.

The X‐ray spectra of the 2041 and 3414‐Bb low TCR resistors after drying at 150°C and after firing display more or less the same peaks. The electrical characteristics of 2041 resistors fired on alumina and LTCC substrates are similar indicating that the resistors are compatible with the LTCC material. After firing on LTCC substrates the sheet resistivities and TCRs of the 3414‐B resistors increased. Also, there is a significant increase in the GFs from 13 to over 25.

Investigates the compatibility of thick‐film materials and the characteristics of the force and temperature sensors.

Strain gauges can be realised by printing and firing thick‐film resistors on ceramic substrates that are usually based on alumina. However, sensing elements made on some other substrates – tetragonal zirconia or stainless steel – would exhibit some improved characteristics, either due to a lower modulus of elasticity or a higher mechanical strength. As thick‐film resistors are developed for firing on alumina substrates their compatibility and possible interactions with other kinds of substrates have to be evaluated. The sheet resistivities and noise indices of the resistors were comparable, whereas the gauge factors were lower for the dielectric‐on‐steel substrates. The temperature coefficients of resistivity (TCR) of the resistors on the ZrO₂ and dielectric‐on‐steel substrates were higher than the TCRs on the alumina substrates, which was attributed to the higher thermal expansion coefficient of the tetragonal zirconia and the stainless steel.