Low Temperature Coefficient Of Resistance Research Articles

A Comprehensive Study on Failure Modes and Mechanisms of Thin Film Chip Resistors

Usually, resistors and capacitors populate majority portion of a common electrical circuit, hence miniaturization drive of any package or subsystem starts with miniaturized resistor and capacitors. In this context, thin film chip resistors are the most sought-after components for any electronic/electrical circuit due to their small size, wide range of values, military temperature range, stringent tolerance, low TCR value (recognised with PPM). Increased use of thin-film surface mount chip resistors in military and space application has led to an increased awareness of its potential failure modes in harsh environments. Thin film resistor with lower TCR (5PPM, 10PPM and 25PPM) are most preferable and widely used because of very low temperature coefficient of resistance (TCR) and high resistivity, which suits for high precision measurement application. Low temperature coefficients characteristics of thin film resistors also makes them stable and reliable. Because of their high-volume usage in recent times, failure in thin film resistor with lower TCR/PPM (Parts per Million) are also being seen more predominantly. In general, there are two types of thin film chip resistors, one is discrete type and the other is die type or wire bondable type. Discrete type chip resistor are used directly on cards, whereas, die type/wire bondable type chip resistors used in hermetically sealed HMC packages. Standard failure mode of a resistor is open mode or high resistance mode, whereas short mode failure has a very low probability. Hence in this paper, failure modes and mechanisms of both types of thin film chip resistors, with respect to common failure causes such as EOS, ESD are discussed, which is in continuation to Fabrication/Workmanship related failures discussed in our earlier technical paper. With this, all possible failure modes and mechanism related thin film chip resistors are explained. Discussion in totality always provide in depth analysis on a subject of concern, which in turn facilitate reliability assessment of the component and corrective action, if any.

Unprecedented electrical performance of friction-extruded copper-graphene composites

Copper-graphene composites show remarkable electrical performance surpassing traditional copper conductors albeit at a micron scale; there are several challenges in demonstrating similar performance at the bulk scale. In this study, we used shear assisted processing and extrusion (ShAPE) to synthesize macro-scale copper-graphene composites with a simultaneously lower temperature coefficient of resistance (TCR) and improved electrical conductivity over copper-only samples. We showed that the addition of 18 ppm of graphene decreased the TCR of C11000 alloy by nearly 11 %. A suite of characterization tools involving scanning and transmission electron microscopy along with atom probe tomography were used to characterize the grain size, crystallographic orientation, structure, and composition of copper grains and graphene additives in the feedstock and processed samples. We posit that the shear extrusion process may have transformed some of the feedstock graphene additives into higher defect-density agglomerates while retaining the structure of others as mono-to-tri-layer flakes with lower defect density. The combination of these additives with heterogeneous structures may have been responsible for the simultaneous decrease in TCR and enhanced electrical conductivity of the copper-graphene ShAPE composites.

All-Three-Dimensionally-Printed AgPd Thick-Film Strain Gauge with a Glass-Ceramic Protective Layer for High-Temperature Applications.

A high-temperature thin/thick-film strain gauge (TFSG) shows development prospects for in situ strain monitoring of hot-end components due to their small perturbations, no damage, and fast response. Direct ink writing (DIW) 3D printing is an emerging and facile approach for the rapid fabrication of TFSG. However, TFSGs prepared based on 3D printing with both high thermal stability and low temperature coefficient of resistance (TCR) over a wide temperature range remain a great challenge. Here, we report a AgPd TFSG with a glass-ceramic protective layer based on DIW. By encapsulating the AgPd sensitive layer and regulating the Pd content, the AgPd TFSG demonstrated a low TCR (191.6 ppm/°C) from 50 to 800 °C and ultrahigh stability (with a resistance drift rate of 0.14%/h at 800 °C). Meanwhile, the achieved specifications for strain detection included a strain sensing range of ±500 με, fast response time of 153 ms, gauge factor of 0.75 at 800 °C, and high durability of >8000 cyclic loading tests. The AgPd TFSG effectively monitors strain in superalloys and can be directly deposited onto cylindrical surfaces, demonstrating the scalability of the presented approach. This work provides a strategy to develop TFSGs for in situ sensing of complex curved surfaces in harsh environments.

Amorphous/Nanocrystalline High-Entropy CoCrFeNiTix Thin Films with Low Thermal Coefficient of Resistivity Obtained via Magnetron Deposition.

High-entropy alloys are promising materials for novel thin-film resistors since they have high resistivity and a low-temperature coefficient of resistivity (TCR). In this work, a new high-entropy thin-film CoCrFeNiTix was deposited on a Si/SiO2 substrate by means of magnetron sputtering of the multi-component target produced by hot pressing of the powder mixture. The samples possessed a thickness of 130-230 nm and an amorphous atomic structure with nanocrystallite traces. This structure persisted after being annealed up to 400 °C, which was confirmed using X-ray and electron diffraction. The film had a single-phase structure with a smooth surface and a uniform distribution of all elements. The obtained film served for microresistor elaboration, which was produced using the lithography technique and tested in a temperature range from -60 °C up to 200 °C. Resistivity at room temperature was estimated as 2.37 μOhm·m. The results have demonstrated that TCR depends on temperature according to the simple linear law in a range from -60 °C up to 130 °C, changing its value from -78 ppm/°C at low temperatures to -6.6 ppm/°C at 130 °C. Such characteristics show the possibility of using these high-entropy alloy films for resistive elements in contemporary and future micro-electronic devices.

The Effect of W Content on the Microstructure, Mechanics and Electrical Performance of an FeCrCo Alloy.

In this paper, FeCrCoW alloys with different W contents (0.4, 2.1 and 3.4 at%) are designed and studied in order to overcome the existing shortcomings of resistance materials. These resistance materials have high resistivity and a low temperature coefficient of resistivity. It is observed that the addition of W has a remarkable effect on the phase structure of the alloy. In particular, when the W content is 3.4 at%, the single BCC phase of the alloy can be transformed into the BCC and FCC phase. Meanwhile, when analyzed by transmission electron microscopy, there are stacking faults and martensite in FeCrCoW alloy with W content of 3.4 at%. These features are related to excessive W content. In addition, the strength of the alloy can be improved, and the ultimate tensile strength and yield strength are both very high, which are considered as grain-boundary strengthening and solid solution strengthening, caused by the addition of W. The electrical resistivity of the FeCrCoW alloys decreases when the content of W is more than 2.1 at%. The maximum resistivity of the alloy is 170 ± 1.5 μΩ·cm. Moreover, the unique properties of the transition metal allow the alloy to have a low temperature coefficient of resistivity in the temperature range of 298~393 K. The temperature coefficient of resistivity values of the W0.4, W2.1 and W3.4 alloys are -0.0073, -0.0052 and -0.0051 ppm/K. Therefore, this work provides a vision for resistance alloys, which can achieve highly stable resistivity and high strengths in a certain temperature range.

Fabrication and characterization of NiCr-based films with high resistivity and low temperature coefficient of resistance

As a metal alloy, NiCr films have a relatively high resistivity and low temperature coefficient of resistance (TCR) and are widely used in electronic components and sensors. However, the resistivity of pure NiCr is insufficient for high-resistance and highly stable film resistors. In this study, a quaternary NiCrAlSi target (47:33:10:10, wt. %) was successfully used to prepare resistor films with resistivities ranging from 1000 to 10 000 μΩ cm and TCR within ±100 ppm/K. An oxygen flow was introduced during the sputtering process. The films exhibit high-temperature stability at 450 °C. The films were analyzed using Auger electron spectroscopy, x-ray diffraction, time-of-flight secondary-ion mass spectrometry, and x-ray photoelectron spectroscopy. The results show that the difference in the oxide proportion of the films caused the differences in resistivity. The near-zero TCR values were considered to be due to the competition between silicon and other metals. This study provides new insights into the electrical properties of NiCr-based films containing Si, which will drive the manufacturing of resistors with high resistivity and zero TCR.

Effects of Ag content and the annealing process on the microstructure and properties of Cu–7Mn–Ag–0.2Ce–0.2Zr resistor alloys

Designing alloys with a low resistance over a wide temperature range, specifically a low temperature coefficient of resistance (TCR), remains a great challenge from a material application perspective. In this study, the effects of Ag content and the annealing process on the microstructure, resistivity, TCR, hardness, and electrochemical corrosion properties of a Cu–7Mn–Ag–0.2Ce–0.2Zr resistance alloys were investigated. The results indicate that adding Ag to the Cu–Mn alloy can improve the solid solubility and change the lattice constant, resulting in a lower resistivity, TCR and better corrosion resistance. The hardness of the alloy increases because Ag segregates and is dispersed in the matrix to form a second phase during the annealing process. The Cu–7Mn–0.5Ag–0.2Ce–0.2Zr alloy performs the best, with a resistivity of 24.1 μΩ·cm and a TCR of 76 × 10−6/°C at 300 °C for 1 h. The alloy had low resistivity and TCR over a wide temperature range, and it also had high stability as well as long-term performance.

A low TCR MEMS heater developed for cryogenic application

A microheater with a small temperature coefficient of resistance (TCR) at liquid hydrogen temperature was designed and fabricated by microfabrication technology. The NiCr heater annealed in N2 at 250 °C achieved the smallest TCR. The crystal structures of the NiCr film annealed in nitrogen were analyzed using a scanning electron microscope (SEM) and by x-ray diffraction (XRD). The crystallization of the NiCr film improved with the increase in annealing temperature. The failure mechanism of the microheater is studied, and it is seen that the central area of the heating film and the joint of the heating film and the electrode are most vulnerable to destruction.

Design and Analysis of High-Performance and Small-Size Piezoresistive Pressure Sensors

In this article, a rapid thermal process is proposed to manufacture piezoresistance to improve the performance of piezoresistive devices, and an absolute piezoresistive pressure sensor is prepared by anodic bonding between silicon film and glass with the cavity to reduce the size of the device. The size of the sensor is only <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.0\times 1.0\times0.513$ </tex-math></inline-formula> mm. At the same time, the arrangement of piezoresistance is optimized by the finite element method. In addition, the deformation of the diaphragm is measured with a profiler, which verified the feasibility of Ti as the absorption of oxygen generated in the anodic bonding process. In the pressure range of 0–200 kPa, the output voltage and nonlinearity of the pressure sensor prepared by the rapid thermal annealing (RTP) process are 91.6 mV and 0.14%FSO, respectively, and the temperature coefficient of resistance (TCR) and the temperature coefficient of sensitivity (TCS) are 571 and −1676 ppm/°C respectively. Compared with the pressure sensor prepared by the common piezoresistive process, the TCR and TCS of the designed sensor are reduced by 73% and 24%, respectively, which has the advantages of high output voltage, low TCR and TCS, and small-size.

A Bilayer Thin-Film Strain Gauge With Temperature Self-Compensation

A Karma–CuNi bilayer strain gauge with a low-temperature coefficient of resistance (TCR) is designed for temperature self-compensation. The impact of heat treatment and structural parameters on its performance is investigated. The TCR of the bilayer thin-film strain gauge can be adjusted to near 0 ppm/°C by controlling the thickness ratio and the annealing temperature. Besides, the Karma–CuNi thin films had a gauge factor (GF) of 2.2. Finally, the Karma–CuNi bilayer thin-film strain gauge was fabricated on the metal substrates and bone-like metal elastomer. An experimental setup based on bending beam theory was developed to determine the GF of the strain gauges fabricated on metal substrate. It shows promising applications for in situ strain or torque measurement of some metal component when high sensitivity and high spatial resolution is required.

Structural, magnetic, and transport properties of epitaxial thin films of equiatomic quaternary CoFeCrGa Heusler alloy

We present the first report on the structural, magnetic, and transport properties of epitaxial thin films of equiatomic quaternary CoFeCrGa, grown on a single crystal MgO(001) substrate. From the structure and surface morphology analyses, we have shown that the films grown are ordered, epitaxial, and homogeneous. Magnetic measurements confirm the soft ferromagnetic nature of the film along the in-plane direction with a coercivity of 4.6 Oe. The resistivity measurements indicate semiconducting nature with a very low temperature coefficient of resistivity (TCR) value, suggesting an almost temperature independent resistivity, similar to other reported spin-gapless semiconductors (SGSs) among the Heusler alloys. A non-saturating, quantum linear magnetoresistance is observed even in high fields of up to 12 kOe, another prerequisite for gapless materials. Hall measurements are also performed, and a detailed analysis has been carried out to estimate the ordinary and anomalous Hall contributions. The conductivity value (σxx) at 300 K is found to be 4280 S cm−1, which is comparable with the other reported SGS materials. We have also studied the effect of L21 and B2 type disorder on the electronic properties based on the first principle calculations and found that the SGS nature in CoFeCrGa is quite robust against the Co–Fe swap disorder (L21 disorder); however, with swap disorder (≥25%) between Cr and Ga sites, the system transits from SGS to half-metallic state. All these results indicate the possibility of spin-gapless semiconducting nature in the CoFeCrGa film, making it highly suitable for spin-based device applications.

Low temperature coefficient of resistivity in antiperovskite Mn3Ga0.7Sn0.3N compound

Low temperature coefficient of resistivity in antiperovskite Mn3Ga0.7Sn0.3N compound

A strong ferritic high‐resistivity multicomponent alloy with tunable ordered coherent multicomponent nanoprecipitates

We design and investigate a ferritic multicomponent alloy with high electrical resistivity, low temperature coefficient of resistivity (TCR) in a wide-temperature range, high strength, and moderate deformability, aiming to overcome the bottlenecks limiting the development of cost-efficient high-quality resistors. The developed bulk alloy with nominal composition Fe55Cr28Al12Ti3Si2 (at. %) shows a body centered cubic (BCC) matrix phase embedded with ordered coherent multicomponent nanoprecipitates in as-cast condition, which enables a high resistivity of 183 µΩ·cm, a low TCR of -35 ppm/K (from 298 to 673 K), a high yield strength of 1055 MPa, a high ultimate compressive strength of 1980 MPa and a moderate uniform compressive strain of 33% (at 673 K). The fully coherent and ordered multicomponent L21 nanoprecipitates in the BCC-α matrix enhance the stress required for dislocation propagation, leading to the improved strength and work hardening ability, according to the comparative study on the alloy variants with and without nanoprecipitates. Also, the multicomponent L21 nanoprecipitates enable the effective tuning of Kondo-like scattering and contribute to the low TCR of the material. The work thus demonstrates a design strategy for low-cost precision resistance alloys to achieve high and stable resistivity in wide temperature ranges combined with high strength and moderate compressive deformability by introducing well-tuned ordered coherent multicomponent precipitates in multicomponent alloy systems.

Low temperature coefficient of resistance and high conductivity: Enhanced Cu–substituted LaCo0.4Ni0.6O3 ceramics for functional material

The LaCo0.4Ni0.6-yCuyO3 (LCNCu, y = 0.02–0.08) ceramics were prepared and their possibility as a cheap alternative functional material for thick film resistors was studied. Scanning electron microscopy, differential–thermal and thermomechanical analyses showed that the incorporation of Cu2+ lowered the densification temperature and enhanced the compactness of LCNCu ceramics. All of the samples revealed relatively high conductivity. When y < 0.05, both Cu2+ substitution and sintering temperature showed a strong influence on the conductivity of LCNCu ceramics. However, the simulation results indicated that the density of states almost did not change after Cu2+ substitution despite the weakened electron transport. The temperature coefficient of resistance (TCR) gradually decreased with the addition of Cu2+. Low TCR values (absolute values < 300 ppm/°C) and high conductivity were realized for the samples with y ≤ 0.04 sintered at 1200 °C and y = 0.02 sintered at 1225 °C. Consequently, the improved LaCo0.4Ni0.6-yCuyO3 ceramics may be a potential economical functional material for thick film resistors.

Achieving high strength and electrical properties in drawn fine Cu matrix composite wire reinforced by in-situ grown graphene

Graphene/Cu composite wire with a diameter as fine as 195 μm was successfully fabricated for the first time by using a synergistic methodology consists of in-situ growth high-quality graphene, spark plasma sintering, hot-extrusion and drawing. The graphene/Cu composite with a continuous severe drawing deformation of 99.7% was easily achieved, which can be benefited from the uniformly dispersion of graphene in Cu matrix. As a result, the graphene/Cu composite wire exhibited an ultrahigh strength (581 MPa), excellent electrical conductivity (4.59 × 107 S/m) and low temperature coefficient of resistance (TCR, 2.98 × 10−3/oC). This work presents a breakthrough in the fabrication and plastic deformation of graphene/Cu composite and has a great promoting effect on its applications for high-power cables and new energy devices.

Study of New Nitrogen-Fireable Copper-Nickel Thick Film Paste Formulation Compatible with Thick Printed Copper.

This paper is focused on a new copper-nickel thick film resistive paste which was designed and experimentally developed for the realization of low-ohmic power resistors. This copper-nickel paste has been designed for use in combination with thick printed copper conductors and in comparison with conventional ruthenium-based thick film resistor pastes allows firing in a nitrogen protective atmosphere. The copper-nickel paste was prepared from copper and nickel microparticles, glass binder particles and a combination of organic solvents optimized for its firing in a nitrogen atmosphere. This paper covers a detailed description of copper-nickel paste composition and its thermal properties verified by simultaneous thermal analysis, a description of the morphology of dried and fired copper-nickel films, as well as the electrical parameters of the final printed resistors. It has been proven by electron microscopy with element distribution analysis that copper and nickel microparticles diffused together during firing and created homogenous copper-nickel alloy film. This film shows a low temperature coefficient of resistance ±45 × 0−6 K−1 and low sheet resistance value 45 mΩ/square. It was verified that formulated copper-nickel paste is nitrogen-fireable and well-compatible with thick printed copper pastes. This combination allows the realization of power substrates with directly integrated low-ohmic resistors.

Study of Copper-Nickel Nanoparticle Resistive Ink Compatible with Printed Copper Films for Power Electronics Applications.

This paper is focused on copper–nickel nanoparticle resistive inks compatible with thick printed copper (TPC) technology, which can be used for power substrate manufacturing instead of conventional metallization techniques. Two types of copper–nickel inks were prepared and deposited by Aerosol Jet technology. The first type of ink was based on copper and nickel nanoparticles with a ratio of 75:25, and the second type of ink consisted of copper–nickel alloy nanoparticles with a ratio of 55:45. The characterization of electrical parameters, microstructure, thermal analysis of prepared inks and study of the influence of copper–nickel content on electrical parameters are described in this paper. It was verified that ink with a copper–nickel ratio of 55:45 (based on constantan nanoparticles) is more appropriate for the production of resistors due to low sheet resistance ~1 Ω/square and low temperature coefficient of resistance ±100·10−6 K−1 values. Copper–nickel inks can be fired in a protective nitrogen atmosphere, which ensures compatibility with copper films. The compatibility of copper–nickel and copper films enables the production of integrated resistors directly on ceramics substrates of power electronics modules made by TPC technology.

Laser-defined graphene strain sensor directly fabricated on 3D-printed structure

A direct-write method to fabricate a strain sensor directly on a structure of interest is reported. In this method, a commercial graphene ink is printed as a square patch (6 mm square) on the structure. The patch is dried at 100 °C for 30 min to remove residual solvents but the printed graphene remains in an insulative state. By scanning a focused laser (830 nm, 100 mW), the graphene becomes electrically conductive and exhibits a piezoresistive effect and a low temperature coefficient of resistance of −0.0006 °C−1. Using this approach, the laser defines a strain sensor pattern on the printed graphene patch. To demonstrate the method, a strain sensor was directly fabricated on a 3D-printed test coupon made of ULTEM 9085 thermoplastic. The sensor exhibits a gauge factor of 3.58, which is significantly higher than that of commercial foil strain gauges made of constantan. This method is an attractive alternative when commercial strain sensors are difficult to employ due to the high porosity and surface roughness of the material structure under test.

Flexible ferroelectric wearable devices for medical applications.

SummaryWearable electronics are becoming increasingly important for medical applications as they have revolutionized the way physiological parameters are monitored. Ferroelectric materials show spontaneous polarization below the Curie temperature, which changes with electric field, temperature, and mechanical deformation. Therefore, they have been widely used in sensor and actuator applications. In addition, these materials can be used for conversion of human-body energy into electricity for powering wearable electronics. In this paper, we review the recent advances in flexible ferroelectric materials for wearable human energy harvesting and sensing. To meet the performance requirements for medical applications, the most suitable materials and manufacturing techniques are reviewed. The approaches used to enhance performance and achieve long-term sustainability and multi-functionality by integrating other active sensing mechanisms (e.g. triboelectric and piezoresistive effects) are discussed. Data processing and transmission as well as the contribution of wearable piezoelectric devices in early disease detection and monitoring vital signs are reviewed.

Spin-gapless semiconductors: Fundamental and applied aspects

Spin-gapless semiconductors (SGSs) are new states of quantum matter, which are characterized by a unique spin-polarized band structure. Unlike conventional semiconductors or half-metallic ferromagnets, they carry a finite bandgap for one spin channel and a close (zero) gap for the other and thus are useful for tunable spin transport applications. It is one of the latest classes of materials considered for spintronic devices. A few of the several advantages of SGS include (i) a high Curie temperature, (ii) a minimal amount of energy required to excite electrons from the valence to conduction band due to zero gap, and (iii) the availability of both charge carriers, i.e., electrons as well as holes, which can be 100% spin-polarized simultaneously. In this perspective article, the theoretical foundation of SGS is first reviewed followed by experimental advancements on various realistic materials. The first band structure of SGS was reported in bulk Co-doped PbPdO2, using first-principles calculations. This was followed by a large number of ab initio simulation reports predicting SGS nature in different Heusler alloy systems. The first experimental realization of SGS was made in 2013 in a bulk inverse Heusler alloy, Mn2CoAl. In terms of material properties, SGS shows a few unique features such as nearly temperature-independent conductivity (σ) and carrier concentration, a very low temperature coefficient of resistivity, a vanishingly small Seebeck coefficient, quantum linear magnetoresistance in a low temperature range, etc. Later, several other systems, including 2-dimensional materials, were reported to show the signature of SGS. There are some variants of SGSs that can show a quantum anomalous Hall effect. These SGSs are classic examples of topological (Chern) insulators. In the later part of this article, we have touched upon some of these aspects of SGS or the so-called Dirac SGS systems as well. In general, SGSs can be categorized into four different types depending on how various bands corresponding to two different spin channels touch the Fermi level. The hunt for these different types of SGS materials is growing very fast. Some of the recent progress along this direction is also discussed.