Properties Of Thick-film Resistors Research Articles

Investigation of sensing performances of thick-film resistors sintered on fluorophlogopite glass-ceramic substrates

Strain gauges made of thick-film resistors (TFRs) offer a promising solution for monitoring the structural health of civil engineering projects, owing to their exceptional durability and stability. To address the issue of strain mismatch between alumina substrates and concrete materials, fluorophlogopite glass-ceramic (FGC), which has a low elastic modulus and good machinability, was utilized as a substrate for thick-film resistors. Compatibility between resistor pastes and substrates should be considered, as the substrate can significantly impact the performance of thick-film resistors. TFRs with varying concentrations of RuO2 were screen printed and fired at different temperatures on both FGC and 96% Al2O3 (as a control) substrates. The sheet resistivity, temperature coefficient of resistance (TCR), and gauge factor (GF) of TFRs were evaluated. The strain sensing performances of TFRs on FGC evaluated under compressive loading. The results indicate that TFRs on FGC substrates exhibit higher hot TCRs, lower sheet resistivities, and lower gauge factors than those on Al2O3 substrates under typical firing conditions of 850°C for 10 minutes. As the concentration of RuO2 increases, the differences in properties between TFRs on the two substrates become less pronounced. Microstructural analyses of the interface between the resistor layer and substrate indicate that changes in properties of TFRs on FGC substrates are primarily attributed to variations in RuO2 concentration and glass phase composition, which result from interactions between the resistor layer and FGC substrate. The interaction between the FGC substrate and the resistor layer can be significantly alleviated by lowering the firing temperature from 850°C to 750°C, resulting in TFRs on FGC substrates with properties comparable to those on alumina substrates. The TFRs on FGC exhibit favorable sensitivity, linearity, repeatability, and hysteresis within the input compression strain range of 0–3043με, thus showcasing significant potential for application in structural health monitoring (SHM) in civil engineering.

Fabrication and characterization of Screen-printed Graphite and Nickel Based Thick Film Resistive Strain Sensor

Piezo resistive properties of thick film resistors are shown by a variety of nanomaterials, in which graphite and nickel are used to study the piezo resistive response in this paper. The present work proposes to fabricate stain sensor on substrates like PVC, and transparent plastic sheet. Screen printing method is used for patterning of sensor on the substrates with two different inks namely piezo resistive ink made of graphite and nickel powder and conductive ink made of silver. Change in resistance of the fabricated sensor is noted for the changes in force applied on the sensor and corresponding gauge factor is observed to be around 10.5 and 11 for PVC and OHP respectively. The screen-printed strain gauge performance is investigated and presented in this paper. This study of mechanical test results demonstrate that the sensor can be used for micro strain detection in various applications.

PREPARING MICROCOMPOSITE POWDERS DOPED WITH ANTIMONY DIOXIDE AND PROPERTIES OF THICK FILMS BASED ON THOSE POWDERS

The goal of the work reported here was to develop a method of applying glass nanolayers of variable thickness to Sn0.9Sb0.1O2 particles and to investigate how this affects the electrical properties of thick-film resistors. We prepared Sn0.9Sb0.1O2 powders by calcinating coprecipitated tin and antimony hydroxides. Thin layers of aluminum, barium, and boron compounds were then precipitated from aqueous solutions onto powder particles. Nanolayers of glass in the BaO ― Al2O3 ― B2O3 system were obtained by dissolution followed by heat treatment. Resistive thick films made from such microcomposite powders have a higher resistivity than do those prepared by traditional methods and that resistivity changes little after repeated heat treatments. The thermal coefficient of electrical resistance decreases with increasing thickness of the glassy layer on the surface of the conducting particles.

Application of percolation concepts to electrical conductivity of polyaniline–inorganic salt composites

The dependence of the resistivity of protonated polyaniline–inorganic salt composites with the volume fraction of electrically conducting component was analyzed on the basis of percolation theory. A short analysis and a discussion of basic treatment in the evaluation of percolation parameters are included. Microscopical observations showed a non-uniform distribution of polyaniline particles in the composites. The composites of polyaniline sulfate with ammonium sulfate and potassium bromide have a low percolation threshold (<3 vol.% conducting component). This has been explained as a property of the segregated structure of the composites, which is formed because of a large difference in the particle sizes. Basic quantitative characteristics of the morphological structure have been obtained using the percolation model, as proposed by Ewen and Robertson, to explain the properties of thick film resistors.

Electrical properties of thick film resistors from noise measurements

Thick film resistors (TFRs) are currently the only materials in microelectronic use whose conductivity can be tailored through composite mixtures of conductive phases within a glassy matrix [1, 2], to span resistivities in the wide range of 10y3 – 103 U cm, giving sheet resistances of 1 U=u to 1 MU=u. Although DuPont-Birox 1400-series or similar ruthenium based TFRs are widely used in modern microelectronic circuits, there is limited data on their intrinsic electrical transport properties such as the charge carrier concentration, drift mobility, etc. TFRs have generally been found to be relatively noisy in the audio frequency range and up to ,105 Hz above which the 1= f noise becomes buried in the white noise. Although the noise characteristics of TFRs have been studied (e.g. [3, 4]), most of the results published to date have not been correlated to, or used to infer, their electrical properties such as carrier concentration, drift mobility, momentum relaxation time, etc. Given the lack of data on the latter electrical transport parameters we have therefore tried to extract these electrical properties from the measured noise spectra and conductivity. We have measured the excess noise (or 1= f noise) in a number of well-defined TFRs made from inks of the Birox 1400 series in an effort to evaluate, at least as an order of magnitude, the free carrier concentration (nc), the drift mobility (μ), mean free path (λ) diffusion coefficient (D), Debye screening length (L), etc. Three values of nominal thick film sheet resistance were chosen — 1, 10 and 100 kU=u which were used to span the resistors range used in hybrid microelectronic circuits. Table I gives the basic geometries and data for some of the samples investigated. The resistors were produced by the standard method specified by the manufacturer of the Du-Pont resistive inks series Birox-1400 [5] and then trimmed by laser to their final values. The Birox 1400 series of TFR inks is based on pyrochlore (Bi2Ru2O7) embedded in lead containing glass. The sheet resistance is decreased by increasing the ratio of pyrochlore in the composition. The noise measurement system and procedures used have been described in detail previously [6]. All measurements were carried out in an electromagnetic (EM), shielded cell and a PC-586 hardware and software environment was used to process the noise spectra obtained from the low-noise amplifiers [6] in real time. Variable bias current was obtained from a series connection of the TFR with a higher value wirewound resistor with a very low noise, i.e. C ˆ 1:5 3 10y16, where C is the relative noise index (a unitless coefficient) defined in Equation 1 below. The smallest detectable spectral noise current density was 10y14 A Hzy1=2 in the frequency region of 1–105 Hz. Ohmic I–V behaviour was observed for all the resistors measured throughout the current range used, i.e. 1–100 μA. Noise spectra were acquired many times for each resistor to ensure reproducibility. The measured excess noise power spectral density Si was found to be well-described by the usual 1= f behaviour,

Influence of the contacts and firing process on the properties of thick film resistors on alumina and dielectrics

This paper describes the behaviour of thick film ruthenium resistors when printed and fired onto standard 96% alumina substrates and onto alumina substrates covered with a dielectric film during long-term thermal ageing. It was observed that the behaviour of the resistors on alumina and dielectric depends upon the firing process of the resistors and the kind of terminations. An analysis of the effects of thermal ageing was made as well as some SEM observations of diffusion processes between the resistor and its terminations.

Effects of substrate thermal expansion coefficient on the physical and electrical properties of thick film resistors

The way in which the difference between the thermal expansion coefficient of a thick film resistor and that of an alumina substrate affects the physical and electrical properties of a resistor was examined. The difference between their thermal expansion produces a compression or a tension in the resistor. Consequently, the electrical resistance and temperature coefficient of resistance of the resistor without a substrate are larger than those of the resistor with a substrate. Also, the values of the compression and tension were obtained.

The Relationship Between the Electrical Properties of Thick Film Resistors and the Thermal Expansion Coefficient of the Substrates

The temperature characteristics of RuO2-based thick film resistors on various substratcs having different thermal expansion coefficient have been investigated.It became clear that, if the thermal expansion coefficient of the substrate is larger than that of the thick film resistor, a compression is being exerted by the substrate on the as-fired resistor at low temperature. As temperature rises, the resistance value increases, and the TCR becomes positive.On the contrary, if the thermal expansion coefficient of the resistor is larger than that of the substrate, the as-fired resistor is being stretched by the substrate at low temperature. As temperature rises, the resistancc value decreases, and the TCR becomes negative.

The Properties of Thick Film Resistors Fabricated on Various Dielectric Layers

The paper presents a comparative analysis of the properties of ruthenate resistor layers produced on alumina substrates and on dielectric layers previously deposited on them. The effect of dielectric type and the peak firing temperature of ruthenate layers upon the value of their resistance and TCR (temperature coefficient of resistance) has been investigated. The reproducibility and stability of these parameters have been evaluated.

Electrical Transport in Thick Film (Cermet) Resistors

Though for many decades have we had thick-film resistors (TFRs) with good electrical properties, no well established model for describing their conduction mechanisms has been achieved. However the efforts of some research groups in U.S.A. and Europe in the last years have had success in improving our knowledge of the microstructure and of a large spectrum of electrical properties of TFRs. The available information narrows the field of possibilities for conduction mechanisms in TFRs. Though no conclusive assessment is yet possible, some lines for further progress can be precisely delineated.

Particle size effects in thick film resistors

This paper describes the effect of conducting oxide particle size on the electrical conduction properties of thick film resistors based on finely divided Bi2Ru2O7 and Pb2Ru2O6. We show that the critical conduction behavior at low conducting oxide concentration can be described as percolative, and that the conducting threshold is lower for smaller particle size. We also measure an increase in the effective activation energies for the low-temperature resistivity, as the conducting oxide particle size decreases. This, we show, is consistent with a tunneling model for conduction in thick-film resistors.

Preparation and properties of thick film resistors containing cadmium glasses and cadmium oxide: R. Kuzel and J. Broukal. Electrocomp. Sci. Technol.7, 29 (1980)

Preparation and properties of thick film resistors containing cadmium glasses and cadmium oxide: R. Kuzel and J. Broukal. Electrocomp. Sci. Technol.7, 29 (1980)

Influence of the Substrate on the Electrical Properties of Thick-Film Resistors

The thick-film technology is widely used for hybrid circuit manufacturing and there is a definite trend to use it in other applications. However, the understanding of the electrical, mechanical, and chemical characteristics of thick-film materials has been approached essentially on an empirical basis, even if many hypotheses have been formulated on their conduction mechanisms. In fact, thick-film resistors present a temperature coefficient of resistance that is negative at lower temperatures and positive at higher temperatures with a TCR vanishing in the range of the room temperature. Recent papers attribute the conduction mechanism to percolation tunneling of electrons through conductive grains embedded in the glassy matrix of the resistor layer. The model assumes that the resistance of the percolation paths dominates the resistance of a network electrically equivalent to the thick-film resistor. With this model a good fitting of the experimental data is obtained. However only data concerning Ru-based resistors screened and fired on 96 percent alumina substrates were considered. In order to better understand the influence of the ceramic substrates on thc electrical and thermal characteristics of thick-film resistors, zirconia, beryllia, and alumina (with different purity) were employed in the present study. The results indicate that the "substrate effect" plays an important role in ruthenium-based resistors, so that, in order to understand the thick-film conduction mechanisms, it is necessary to take into consideration the "substrate resistor system" and not to limit the analysis to the film in itself. Of particular interest is the fact that the minimum of the resistance-versus-temperature curve varies for different substrate materials, even if the resistors under test are made with the same resistor series and are characterized by the same sheet resistivity. An equation is proposed that correlates the resistor gauge factor to thermal expansion coefficient of the ceramic substrate. By assuming the validity of a recently proposed model of conduction mechanism in thick film, a new set of equations is proposed that fits the experimental results obtained on resistors screened and fired on substrates of different compositions or with a different content of impurities.

Influence of the Substrate on the Electrical Properties of Thick-Film Resistors

The effect of substrate type on the electrical properties of thick film resistors is determined. Five different substrates are used. The following properties are investigated: – thermal expansion, resistor profiles, resistance, TCR and resistor gauge factor. The resistors are physically inspected using X-ray diffractometry and electron probe analysis. This paper shows that conduction mechanism models for thick-film resistors generally need not take into account chemical and structural interactions with the substrate. However the effect of substrate on TCR values is significant for resistors exhibiting a large piezoresistive effect.

Effects of Refiring Processes on Electrical and Structural Properties of Thick-Film Resistors

in order to analyze the influence of the refiring processes in thick film resistors, electrical and structural properties of resistors, refired up to ten times, through the original profile, were compared.The apparent sheet resistivity and TCR were measured as a function of the number of the firing cycles, and these electrical characteristics analyzed in connection with observations of structural and chemical modifications evidenced through X-ray diffraction, SEM inspection and microprobe analysis.Marked effects were observed, such as segregation of the conductive grains in the resistor thickness, chemical reactions of glass-modifiers with glass, crystallization of new phases, together with substrate/thick-film interactions.It is found that in some cases (e.g. for DP 1400 resistor series) the phenomena induced by refiring are few and simple enough for us to interprete the corresponding electrical modifications, while in other systems the presence of many competitive chemicophysical effects inhibit their unambiguous correlation with the electrical properties of these resistors.