The influence of firing temperature on the electrical and microstructural characteristics of thick-film resistors for strain gauge applications (original) (raw)

Characterisation of thick film resistor series for strain sensors

Journal of the European Ceramic Society, 2001

Some 10 kohm/sq. thick film resistors based on RuO 2 , ruthenates or a mixture of RuO 2 and ruthenates, were evaluated for strain gauge applications. The resistors were fired at different temperatures to estimate the influence of firing temperature on the electrical characteristics. Temperature coefficients of resistivity (TCR), noise indices and gauge factors (GF) were measured. Microstructures of the thick film resistors were analysed by SEM. The results indicate that the microstructure of thick film resistors influences the gauge factors much more significantly than the ''nature'' of the conductive phase. #

A Characterisation of Thick Film Resistors for Strain Gauge Applications

Journal of Materials Science, 2001

Some commercial thick film resistors with sheet resistivities from 1 kohm/sq. up to 1 Mohm/sq. were evaluated for strain gauge applications. Temperature coefficients of resistivity, noise indices and gauge factors (GFs) were measured. For the same resistor series GFs and noise indices increase with increasing sheet resistivity. However, both GFs and noise indices are different for resistors with the same nominal sheet resistivity but from different resistor series. The results indicated that the microstructure rather than the different chemical composition of the conductive phase in thick film resistors is the primary reason for the different gauge factors. C 2001 Kluwer Academic Publishers

Thick-film resistors on various substrates as sensing elements for strain-gauge applications

Sensors and Actuators A: Physical, 2003

The characteristics of 10 kohm/sq. thick-film resistors (2041, Du Pont and 2341-B, ESL) fired on tetragonal ZrO 2 , low-temperature cofired ceramic (LTCC) and dielectric-on-steel substrates were investigated with the aim of determining the compatibility of these resistor materials, which were developed for firing on Al 2 O 3 , with other substrates. Possible interactions between the thick-film resistors and the substrates were investigated. Sheet resistivities, temperature coefficients of resistivity, noise indices and gauge factors (GFs) were measured. The results indicate that the 2041 and 3414-B thick-film resistors could be used on the evaluated substrates if an allowance is made for the increased temperature coefficient of resistivities (TCRs) of both resistor materials on the zirconia substrates and for the increased sheet resistivities and TCRs of the 3414-B resistors on the LTCC substrates.

Piezoresistive properties of RuO2-based thick-film resistors: the effect of RuO2 grain size

Sensors and Actuators A: Physical, 1997

The piezoresistive properties of thick-film resistors are well documented and widely used in sensors of strain-related quantities. However, the origin of the effect is not well established, and correlations between resistor composition and relevant properties (such as strain sensitivity, temperature coefficient of resistance (TCR) and excess noise) have been not worked out yet. This paper reports a systematic study of these correlations in RuO 2 -based model resistors prepared with the same glass frit and RuO 2 powders covering a range of particle sizes from a few nanometres to micrometres. Gauge factors (GFs) from 2 to 30 have been observed in resistors of sheet resistance R h in the range 1 kV/h to 3 MV/h. At a selected R h value, the GF increases linearly with the logarithm of RuO 2 grain size, while the TCR and excess noise do not significantly depend on the RuO 2 powder size.

Lead-free ruthenium-based thick-film resistors: a study of model systems

Journal of Materials Science: Materials in Electronics, 1991

A model system of thick-film resistor (TFR) was prepared starting from RuOa powders and a lead-free glass. The microstructural development was investigated by scanning and transmission electron microscopies, energy dispersive X-ray fluorescence, X-ray diffraction, thermogravimetry and other complementary techniques. The electrical properties of the resistors were analysed with particular attention to sheet resistance, temperature coefficient of resistance, size effects and piezoresistive properties. It was found that these simple systems are interesting with respect to their stability in ageing tests at relatively high temperatures but they are not promising for high-temperature piezoresistive gauges because of low strain sensitivity. Some samples were also prepared with a Bi2Ru2Ov; a notable exchange reaction occurs between the conductive grains and the glass matrix which prevents the formation of pyrochlore-type based resistors with this glassy matrix.

Electrical properties of conductive materials used in thick-film resistors

Journal of Materials Science, 1988

Layers of conductive oxide powders (IrO2, RuO2 and Bi2RuzO7) were prepared on alumina substrates by a thick-film technique. The films were fired at 875~ for different dwell times. The temperature dependence of resistance was measured in the range-1 96 to 850 ~ SEM observations of the initial powders and the resistive layer surface after firing, as well as X-ray diffraction investigations, were carried out. The RuO2 and IrO2 oxides exhibit a high sintering ratio and the resistance of the fired layers increases with temperature as in the single crystal. The R(T) curve for Bi2Ru207 layers is in qualitative agreement with the polycrystalline material. The role of the grain surface area and the regions between the grains is dominant.

Size Effects in Ruthenium-Based Thick-Film Resistors: Rutile vs. Pyrochlore-Based Resistors

Active and Passive Electronic Components, 1991

The size effect, namely the change of sheet resistance, Rs as a function of resistor length, has been investigated in layers whose conductive phase evolves from Pb-rich (Ru-deficient pyrochlores) to Pb2Ru206.5 and finally to RuO2 by increasing the firing temperature. It is found that Bi diffusion from the terminations is responsible for lower sheet resistance values in shorter resistors whatever the conductive phase is. On the contrary, Ag diffusion is responsible for lower sheet resistance values in shorter resistors only in the case of ruthenate conductive grains while the reverse is observed in RuO2-based layers. Size effect can be suppressed with Pt/Au-based terminations provided that no Bi is contained and with Au-metallorganic-based contact provided that the peak firing temperature is not too high.

Very high strain sensitivity in thick-film resistors: real and false super gauge factors

Sensors and Actuators, 1989

An investigation has been carried out on the correlations between composition/morphology of Ru02-based thick-film resistors and their strain sensitivity. Very high gauge factors (GFs), as well as satisfactory performance in terms of TCR (temperature coefficient of resistance), excess noise and reliability, are obtained with an appropriate choice of glassy matrix, RuOp grain size and concentrations. Resistive systems modified with metal and metal oxide additions are also analysed. In some cases notable changes of electrical properties are observed, related to defective structures. Methods for a simple and accurate diagnosis of reliable or fictitious performance of thick-film strain gauges are identified.