Thick Film Resistors Research Articles

Pulse Conductivity in Ag-Pd Resistors Induced by Laser Pulses

Pulsed EMF in resistive thick-film Ag-Pd elements is experimentally studied when their surface is irradiated with a laser beam. The dependences of the pulsed EMF on the coordinate of the action of the laser beam on the film surface are obtained. It is shown that applying a constant bias voltage to a thick-film resistive element can significantly increase the amplitude of unipolar EMF pulses induced by laser pulses. It was found that the amplitude and frequency of the EMF signals depend, respectively, on the power and frequency of laser pulses. It is shown that by the value of the pulsed EMF it is possible to control the parameters of the high-power laser radiation incident on the surface in real time. The design of a receiver for recording the parameters of laser radiation based on an Ag-Pd sensitive element has been developed. The sensitivity of the device for measuring the power and pulse repetition rate is estimated. Keywords: measurement of laser parameters, thick-film resistor, thermo EMF.

Evaluation of Zn‐substituted La0.5Sr0.5CoO3 ceramics as functional materials for thick‐film resistors

AbstractThis work focuses on the evaluation of La0.5Sr0.5Co1‐xZnxO3 (LSCZ, x = 0.00–0.10) ceramics as an air‐fireable and economical functional material for thick film resistors. Solid‐state reaction experiments and first‐principles calculations were conducted to investigate the crystal structure, thermal behaviors, and electrical properties of LSCZ ceramics. The substitution of Zn2+ modified the bond properties, electron distribution, and band structure, resulting in more serious structural deformation, increasing the bond population of Co–O and weakening the charge transfer of LSCZ. Experimental results showed that the addition of Zn2+ lowered the densification temperature, activation energy, and crystallite size. As the ratio of Zn2+ increased, the conductivity and temperature coefficient of resistance showed a downward trend. Impedance variation with frequency and thermal aging tests were also performed. For the x = 0.05 specimen sintered at 1200°C, values of 95.5% for relative density, 2857 S/cm for conductivity, 1267 ppm/°C for temperature coefficient of resistance, –0.47% for conductivity change could be achieved.

Reduced Graphene Oxide Screen Printed Thick Film as NO<sub>2</sub> Gas Sensor at Low Temperature

Most of the recent reduced graphene oxide (rGO) based sensors shows gas sensitivity above 50o to 150°C. The present investigation deals with the gas sensing at 50°C temperature. In the present research work, thick film sensors of rGO were developed on glass substrate by using standard screen-printing technique. The silver paste of rGO was used to make electrodes for contact on thick films for the electrical and gas sensing system. The electrical properties of rGO thick films such as resistivity, activation energy and temperature coefficient were studied. The resistivity of rGO thick films was found to be 84.84 Ω/m. The morphological, elemental and structural properties of rGO thick films were analyzed by SEM, EDS and XRD techniques respectively. The crystallite size of rGO thick films was found as 28.42 nm by using Scherer’s formula. The rGO thick films were prepared and exposed to Ethanol, NH3, NO2 and LPG gases to determine sensitivity and selectivity. The sensitivity of NO2 has been found to be maximum among other exposed gases. The maximum sensitivity of NO2 gas was 92.55 % at 50 °C found with fast response (~ 11 sec) and recovery (~ 19 sec) time.

Conducting Property and Performance Evaluation of LNF as Cathode Current Contact Layer in Solid Oxide Fuel Cell

In this work, LaNi0.6Fe0.4O3 is prepared and applied as cathode current contact layer on anode supported SOFC. The conducting property of both thin (~7μm) and thick LNF film (~1mm) are tested using lateral Van der Pauw DC conductivity test method and direct DC conductivity test method. Results show that the LNF layer prominently improves electrochemical performance of industrial sized anode supported single cell by ~29% at voltage of 0.7V at 800 and 750℃. During long-term annealing, 950℃ pre-fired LNF film performs more stable conducting property than 900℃ prepared sample. While the area specific resistance of LNF thick film shows a small increasing by ~0.272% per 1000 hours at 750℃, under constant current load. Suggesting good application prospects in planar solid oxide fuel cell stack.

Experimental and theoretical study on the resistive properties of LaCo0·4Ni0·6O3 ceramic with Mg-ion substitution

To explore an air-fireable and economically functional phase for thick-film resistors, the crystal structure, microstructure, sintering, and resistive properties of LaCo0·4Ni0.6−xMgxO3 (LCNM, x = 0.00–0.08) ceramics are studied in this paper, based on solid-state reaction experiments and theoretical calculations. With Mg-ion increase, the impurity phases of NiO and La3Ni4O10 increased, the maximum shrinkage rate occurred at a higher temperature, and the microstructures became worse. The addition of the Mg ion increased the resistivity and decreased the temperature coefficient of resistivity (TCρ). The calculation results, including the bond population, electron density distribution, and density of states of the system agreed with the change in experimental resistivity. Relatively low resistivity and TCρ with a small absolute value could be achieved for specimens with x ≤ 0.02 sintered at 1200 °C and 1250 °C. Hence, the LCNM (x ≤ 0.02) ceramics are possible functional material for thick-film resistors.

Zn2SnO4 Modified ZnO Thick Film Resistors as LPG Sensor

Zn2SnO4 Modified ZnO Thick Film Resistors as LPG Sensor

High-performance electrical properties of La-based perovskite ceramics for the functional phase of thick film resistors

In order to explore an economical functional phase alternative material for thick film resistors, the crystal structure, microstructure, and electrical properties of (1-x)La0.5Sr0.5Co0.96Ni0.04O3-δ + xLaCo0.4Ni0.58Zn0.02O3 (x = 0.0–1.0) composite ceramics were studied through solid-state reaction experiments. The composite ceramics were characterized by x–ray diffraction, scanning electron microscopy, energy dispersive x–ray spectroscopy, X-ray photoelectron spectroscopy, and DC four–probe method. Results suggested that the main phases of La0.5Sr0.5Co0.96Ni0.04O3-δ and LaCo0.4Ni0.58Zn0.02O3 were formed, along with a small part of impurity phases. The addition of LaCo0.4Ni0.58Zn0.02O3 to La0.5Sr0.5Co0.96Ni0.04O3-δ decreased the electrical conductivity and changed the temperature coefficient of resistance from positive to negative. Zero temperature coefficient of resistance could be achieved around 0.6 < x < 0.8 and relatively low absolute temperature coefficient of resistance values could be obtained for the samples of 0.4 ≤ x ≤ 0.8. The ceramic of 0.6La0.5Sr0.5Co0.96Ni0.04O3-δ + 0.4LaCo0.4Ni0.58Zn0.02O3 showed the optimal performances of conductivity = 1923 S/cm, temperature coefficient of resistance = 379.54 ppm/°C, and relative density = 95.05%.

Pseudogap, Nanocrystals and Electrical Conductivity of Doped Silicate Glass

The ideas of pseudogap and nanocrystals have applied to mechanism of electrical conduction in silicate glass doped by oxides of transition metals (thick film resistors). Pseudogap is formed near the valence band of the glass due to diffusion of dopant atoms into the glass in calcination. Nanocrystals are generated in the glass in melting process and undergo structure transitions at high temperatures. This approach lets to explain the temperature dependence of conductivity of doped silicate glass from liquid helium up to 1100 K.

Detection of Corrosion in Thick Film Resistors by X-Ray Imaging

In this article, a non-destructive method is presented, using 2D X-ray imaging, to investigate corrosion defects in thick film resistors stressed by two different corrosion experiments, a single gas experiment and a flowers of sulphur experiment. In total, 370 devices under test (DUTs) were investigated, using the 2D X-ray imaging technique, of which 10 were imaged in a sequence of 2D X-ray images to evaluate the corrosion propagation. The observed underlying corrosion product was verified by using focused ion beam analysis combined with an energy dispersive X-ray spectroscopy. The presented 2D X-ray imaging technique enables a fast and non-destructive method for accurately identifying corrosion and corrosion progression in thick film resistors. The presented imaging method was found to be particularly suitable for supplier benchmarking purposes, as well as for the failure analysis of field returns as it allows for a proper corrosion evaluation of surface mount thick film resistors, while keeping the analysed assembly intact.

The sintering and electrical properties of Zn-substituted LaCo0·4Ni0·6O3 ceramics based upon experiments and calculations

To explore a low–cost functional phase alternative material for thick film resistors, the thermal behavior, sintering and electrical properties of LaCo0·4Ni0.6-yZnyO3 (y = 0.00–0.08, LCNZ) ceramics were investigated through experiments and density functional theory calculations. Results of simultaneous thermal analysis, thermomechanical analysis, scanning electron microscopy, and DC four–probe method indicated that substitution of Ni-ion by Zn–ion could lower the phase formation and densification temperatures of LCNZ, as well as increase the resistivity and decrease the temperature coefficient of resistance (TCR). The resistivity of 0.94 mΩ cm (y = 0.00) and 1.03 mΩ cm (y = 0.02), as well as TCR value of −312.79 ppm/°C (for y = 0.00) and −872.82 ppm/°C (for y = 0.02) could be achieved as the LCNZ ceramics sintered at 1200 °C. The variations of octahedral bond population, electron density around oxygens, and partial density of states near the Fermi level firmly supported the results of experiments.

Chemical processes accompanying the formation of modified ruthenium resistors and their functional properties

The chemical processes of manufacturing thick-film ruthenium resistors, which are accompanied by an acid-base interaction between the inorganic components of the paste, were studied. The regularities of composition formation and consumer properties of the resistors were determined.

Electrical properties of graphite-glass thick-film resistors

PurposeThe purpose of this paper is to present the properties of thick-film resistors made of novel pastes prepared from glass and graphite.Design/methodology/approachGraphite-based resistors were made of thick-film pastes with different graphite-to-glass mass fraction were prepared and examined. Sheet resistance, temperature coefficient of resistance, impact of humidity and short-term overload were investigated. The properties of the layers fired in atmospheres of air at 550°C and nitrogen at 875°C were compared.FindingsGraphite-based resistors with various graphite-to-glass ratios made possible to obtain a wide range of sheet resistance from single O/square to few kO/square. These values were dependent on firing atmosphere, paste composition and the number of screen-printed layers. The samples made of paste with 1:1 graphite-to-glass ratio exhibited the temperature coefficient of resistance of about −1,000 ppm/°C, almost independently on the firing atmosphere and presence of a top coating. The resistors fired in the air after coating with overglaze, exhibited significantly lower sheet resistance, reduced impact of humidity and improved power capabilities.Originality/valueIn this paper, graphite-based resistors for applications in typical high-temperature cermet thick-film circuits were presented, whereas typical graphite-based resistors were fabricated in polymer thick-film technology. Owing to very low cost of the graphite, the material is suitable for low-power passive circuits, where components are not subjected into high temperature, above the typical temperature of operation of standard electronic components.

Experimental and theoretical study on enhanced electrical properties of nickel-substituted La0.5Sr0.5CoO3−δ ceramics

The effect of Ni substitution on the thermal behavior, crystal structure, densification, and electrical properties of La0.5Sr0.5Co1–yNiyO3-δ (y = 0.00–0.08) (LSCN) ceramics was discussed based on experimental measurements and theoretical calculations to search for a ruthenium–free and lead–free conductive oxide for thick film resistors. Ceramics were synthesized by the solid–state reaction, and calculations were performed with first–principle density functional theory (DFT). Results showed that the replacement of Ni ion to Co ion could help decrease the densification temperature and enhance the densification level and improve the conductivity of LSCN. Theoretical calculations, including the crystal structure, bond population, total energy, and density of states (DOS), supported the experimental results well. The maximum conductivity of 3155 S/cm was achieved as y = 0.04 was sintered at 1200 °C, and the peak temperature coefficient of resistance (TCR) of 2405.7 ppm/°C occurred at y = 0.06.

Statistical Description of High-Voltage Pulse Trimming of RuO2 and Bi2Ru2O7-Based Thick Resistive Films

The revival of thick-film technology can be attributed to the increasing demand for thick-film resistors that are being used both as sensing and as resistive elements in various contemporary applications such as various types of micro-electromechanical system (MEMS) sensors based on low temperature co-fired ceramic (LTCC) technology. New stricter requirements that, among others, include precise resistance values and increasing use of buried components brought to the focus the high-voltage pulse trimming process that can provide precise and reliable resistance tuning. In order to improve understanding of experimental findings related to resistors trimmed using energy of high-voltage pulses, this article focuses on statistical approach to high-voltage pulse trimming of RuO2 and Bi2Ru2O7-based thick resistive films. The bimodal conductance distribution model is used in the analysis of trimming effects on the resistive film and in evaluation of low-frequency noise induced by the high-voltage pulse trimming process where conduction fluctuations noise is caused by fluctuations of two local conductances. Expressions for the total conductance and the relative voltage noise spectrum of thick resistive film are given and analyzed using experimental investigations.

Effect of nanometric and micronic particles size on physical and electrical properties of graphite thick film

Precise control and design of the microstructure of active layers in thick films is essential as it has a profound impact on the overall thick film properties. This includes the particle size effect of the starting material which forms the active layer of the thick film. Given the fact that nanosized particles have distinct properties from their bulk counterpart, the effect of the size of graphite starting material towards the formation of thick film graphite and its properties is worthwhile studying. Herein, we report on the study of effect of different particle size of graphite starting material towards the thermal stability and rheological properties of nanographite and micrographite thick film paste, and electrical conductivity of graphite thick film. Graphite starting material with the average particle size of <20 μm was used as source of micron size particles while the same material was milled for 6 h to generate nanosized particles in the range from 13.3 mm to 116.5 nm. Organic binder solution comprising linseed oil, m-xylene and α-terpineol was mixed with the nano and micron-sized particles of graphite powder respectively at 40°C for 24 h. Thermal analysis results showed that thick film paste obtained from nanosized graphite starting material (A) decomposed at lower temperature than the paste prepared from micron-sized graphite starting material (B). Both graphite paste samples with different particle size were printed onto alumina substrates using tape casting method followed by subsequent heating at 300°C and 350°C. Viscosity measurements revealed that the viscosity of paste obtained from nanosized graphite was significantly higher than the paste obtained from micron-sized graphite. The electrical resistance of thick film obtained from micron-sized graphite was lower than the resistance of thick film obtained from nanosized graphite, suggesting that the defects introduced to the particles from the milling process could have impeded the movement of electrons. In addition, the tendency of nanosized particles to react with other molecules, namely oxygen is much greater due to increased surface area, which in turn has also contributed to the higher value of electrical resistance.

Temperature characteristics of thick-film resistors and its application as a strain sensor with low temperature-sensitivity

Strain gauge made of thick-film resistors (TFRs) has great potential for civil engineering applications due to its relatively high strain sensitivity, good stability, low manufacturing cost, mass productability, and long life. Nevertheless, a persistent shortcoming of strain sensors is their thermal sensitivity. Temperature-insensitive strain measurement is important for applications. To address this issue, a thick-film resistor strain sensor with low temperature-sensitivity should be proposed and fabricated. In this paper, the effect of resistor paste components and firing temperatures on the temperature coefficient of resistance (TCR) of TFRs were studied systematically. TFRs made of various RuO2 concentrations (10 wt% to 30 wt%) fired on Al2O3 substrate at different firing temperatures (Tf) was investigated. The relationships between sheet resistivity, TCR and gauge factor (GF) were studied. The results show that hot TCR increases with increasing RuO2 concentration and firing temperature. In the vicinity of the minimum of the resistance–temperature curve (Tmin), the temperature has the least influence on the resistance value, and it can be considered that the TFR is temperature insensitive in a certain range. The effect of temperature on output strain can be evaluated by the ratio of TCR to GF. The results show that TCR, the ratio of TCR to GF and Tmin are all depended on sheet resistivity of thick-film resistors. By changing the concentration of the conductive phase and firing temperature, the sheet resistivity of TFRs can be controlled, and then strain sensors with low temperature-sensitivity for different ambient temperatures can be achieved.

MEMS piezo-resistive force sensor based on DC sputtering deposited amorphous carbon films

The rapid growing demand of micro-electromechanical system (MEMS) sensors brings an urgent need for high performance and low cost sensitive materials. In this work, amorphous carbon (a-C) film was in-situ deposited on silicon substrate as strain sensitive component using economical direct current (DC) magnetron sputtering process and the a-C sensor was systematically designed, fabricated and tested. By adjusting the negative bias voltage in the range of 0–400 V, the gauge factor (GF) of the a-C film was adjusted within the range of 3.3–6.9. What’s more, the film’s sp2 cluster size played an important role in their piezo-resistive performance and conductivity, which illustrated the thick-film resistors (TFRs) theory. Additionally, CAFM results also supported the applying of TFRs theory in this work. Benefiting from the outstanding performance of a-C film, the MEMS force sensor, consisted a Wheatstone full-bridge with four a-C piezo-resistors, had a sensitivity of 9.8 μV/V/mN and non-linearity about 2.0% FS in the testing range of 0–210 mN, while it also showed a good repeatability. These investigations provided deeper insight into the piezo-resistive behavior of a-C film and contributed to the development of high performance and more economical sensitive materials for MEMS sensors.

Effect of V Substitution on the Electrical Properties of La0.5Sr0.5Co1−xVxO3 (x = 0.00–0.10) Ceramics

In this paper, the microstructures, resistivity as well as temperature coefficient of resistance (TCR) of La0.5Sr0.5Co1−xVxO3 (x = 0.00–0.10) ceramics were studied. These ceramic samples were prepared through conventional solid-state reaction method. Results showed that the substitution of Co ions with V ions improved the densification level of ceramic samples and changed their resistive characteristics accordingly. A uniform microstructure of La0.5Sr0.5 Co1−xVxO3 ceramic was realized at x = 0.05 when sintered at 1100°C. The resistivity of ceramics increased slightly as the V content varied in the range of 0.00–0.10. The TCR value of all tested samples was maintained between +1304.35 ppm/°C and +2958.26 ppm/°C. A low resistivity value of 0.38 mΩ cm and the minimum TCR value of +1304.35 ppm/°C were achieved as x = 0.05 in La0.5Sr0.5Co1−xVxO3. It was found that the substitution of Co ions with V ions facilitated lowering the TCR value without changing the resistivity too much. Thus, these ceramics are promising materials for conductive oxide used in thick-film resistors.

Reliability of printed power resistor with thick-film copper terminals

This paper is focused on the thick-film power resistors with copper terminals. These terminals are created by the new Thick Printed Copper (TPC) technology. This technology is based on sequential screen printing and firing of copper paste in nitrogen atmosphere on an alumina substrate. Thick-film power resistor with copper terminals represents a potential replacement of standard wirewound power resistors and allows the direct integration of resistors on TPC substrates. Printed resistors on TPC substrates can be supplemented with discrete electronic components which creates the possibility to realize really complex power electronic circuits. The direct integration of printed components is not possible in case of using the standard Direct Bonded Copper (DBC) technology. The main benefits of printed resistors based on TPC technology are their low thickness and good thermal conductivity. The low thickness of resistors is important for miniaturization of final electronic devices. The resistor main electrical parameters as the temperature coefficient of resistance, temperature coefficient and nominal resistance value after dry heat aging and after thermal cycling, insulation resistance, dielectric strength etc., are described in this paper.

Structure and mechanism of electrical conductivity of resistive compositions for thick-film metal-ceramic heating elements

The work is devoted to the solution of scientific and technical problems of creating granular resistive thick films used in the manufacture of metal-ceramic heating elements. Using the method of mechanosynthesis, particles of transition metal borides and aluminoborosilicate glass of complex chemical composition were obtained.&#x0D; The electrical and thermal properties of thick-film metal-ceramic heating elements with a resistive layer based on modified particles of a conductive material are studied.&#x0D; The heating elements of the new generation are made by the method of thick-film technology, which is widely used in microelectronics in the manufacture of hybrid electronic circuits. Structurally, the thick-film heater is a base (metal with a dielectric coating, ceramics, glass, glass), which is consistently applied through a mesh stencil resistive paste and a dielectric protective coating.&#x0D; Direct heat transfer from the heating film to the substrate of the heat remover, due to the very low thermal inertia of the design, provides a quick exit of the heating element to the operating temperature. This feature of heaters opens new opportunities for their special use.&#x0D; The resistive layer is a complex heterogeneous disordered system containing regions with a metallic conductivity and dielectric portions. The electrical conductivity in such systems is a superposition of the metallic type — in the conducting phase and the activation phase — through the interlayer between the particles. The layer plays the role of a potential barrier for current carriers and largely determines the predominance of one of the electromigration mechanisms. Its composition and properties are formed during the interaction of molten glass with oxide films of particles of the conductive phase and doping of the compositions.&#x0D; Obtaining composite particles of the conductive phase in the process of preparation and heat treatment of materials allows you to purposefully change the properties of the nanoscale interlayer between these particles, which leads to the possibility of creating a group of materials and heating elements based on them with a complex of new properties.