scholarly journals Development, Characterisation and High-Temperature Suitability of Thin-Film Strain Gauges Directly Deposited with a New Sputter Coating System

Sensors ◽  
2020 ◽  
Vol 20 (11) ◽  
pp. 3294
Author(s):  
Daniel Klaas ◽  
Rico Ottermann ◽  
Folke Dencker ◽  
Marc Christopher Wurz
Keyword(s):  
Thin Film ◽  
High Temperature ◽  
Protective Layer ◽  
Strain Gauges ◽  
Gauge Factor ◽  
Coating System ◽  
Component Size ◽  
Commercial Strain ◽  
Operation Temperature ◽  
Sputter Coating

New sensor and sensor manufacturing technologies are identified as a key factor for a successful digitalisation and are therefore economically important for manufacturers and industry. To address various requirements, a new sputter coating system has been invented at the Institute of Micro Production Technology. It enables the deposition of sensor systems directly onto technical surfaces. Compared to commercially available systems, it has no spatial limitations concerning the maximum coatable component size. Moreover, it enables a simultaneous structuring of deposited layers. Within this paper, characterisation techniques, results and challenges concerning directly deposited thin film strain gauges with the new sputter coating system are presented. Constantan (CuNiMn 54/45/1) and NiCr 80/20 are used as sensor materials. The initial resistance, temperature coefficient of resistance and gauge factor/k-factor of quarter-bridge strain gauges are characterised. The influence of a protective layer on sensor behaviour and layer adhesion is investigated as well. Moreover, the temperature compensation quality of directly deposited half-bridge strain gauges is evaluated, optimised with an external trimming technology and benchmarked against commercial strain gauges. Finally, the suitability for high-temperature strain measurement is investigated. Results show a maximum operation temperature of at least 400 °C, which is above the current state-of-the-art of commercial foil-based metal strain gauges.

scholarly journals Advances in Thin Film Sensor Technologies for Engine Applications

1997 ◽  
Author(s):  
Jih-Fen Lei ◽  
Lisa C. Martin ◽  
Herbert A. Will
Keyword(s):  
Thin Film ◽  
High Temperature ◽  
High Speed ◽  
Ceramic Matrix Composites ◽  
Surface Strain ◽  
Research Center ◽  
Strain Gauges ◽  
Nasa Lewis Research ◽  
Film Sensor ◽  
Thin Film Sensor

Advanced thin film sensor techniques that can provide accurate surface strain and temperature measurements are being developed at NASA Lewis Research Center. These sensors are needed to provide minimally intrusive characterization of advanced materials (such as ceramics and composites) and structures (such as components for Space Shuttle Main Engine, High Speed Civil Transport, Advanced Subsonic Transports and General Aviation Aircraft) in hostile, high-temperature environments, and for validation of design codes. This paper presents two advanced thin film sensor technologies: strain gauges and thermocouples. These sensors are sputter deposited directly onto the test articles and are only a few micrometers thick; the surface of the test article is not structurally altered and there is minimal disturbance of the gas flow over the surface. The strain gauges are palladium-13% chromium based and the thermocouples are platinum-13% rhodium vs. platinum. The fabrication techniques of these thin film sensors in a class 1000 cleanroom at the NASA Lewis Research Center are described. Their demonstration on a variety of engine materials, including superalloys, ceramics and advanced ceramic matrix composites, in several hostile, high-temperature test environments are discussed.

scholarly journals Creep adjustment of strain gauges based on granular NiCr-carbon thin films

2021 ◽  
Vol 10 (1) ◽  
pp. 53-61
Author(s):  
Maximilian Mathis ◽  
Dennis Vollberg ◽  
Matthäus Langosch ◽  
Dirk Göttel ◽  
Angela Lellig ◽  
...  
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Creep Behavior ◽  
Polymer Substrate ◽  
Strain Gauges ◽  
Gauge Factor ◽  
Strain Transfer ◽  
Spring Element ◽  
Force Transducers ◽  
Carbon Thin Film

Abstract. An important property of high-precision mechanical sensors such as force transducers or torque sensors is the so-called creep error. It is defined as the signal deviation over time at a constant load. Since this signal deviation results in a reduced accuracy of the sensor, it is beneficial to minimize the creep error. Many of these sensors consist of a metallic spring element and strain gauges. In order to realize a sensor with a creep error of almost zero, it is necessary to compensate for the creep behavior of the metallic spring element. This can be achieved by creep adjustment of the used strain gauges. Unlike standard metal foil strain gauges with a gauge factor of 2, a type of strain gauges based on sputter-deposited NiCr-carbon thin films on polymer substrates offers the advantage of an improved gauge factor of about 10. However, for this type of strain gauge, creep adjustment by customary methods is not possible. In order to remedy this disadvantage, a thorough creep analysis is carried out. Five major influences on the creep error of force transducers equipped with NiCr-carbon thin-film strain gauges are examined, namely, the material creep of the metallic spring element (1), the creep (relaxation) of the polymer substrate (2), the composition of the thin film (3), the strain transfer to the thin film (4), and the kind of strain field on the surface of the transducer (5). Consequently, we present two applicable methods for creep adjustment of NiCr-carbon thin- film strain gauges. The first method addresses the intrinsic creep behavior of the thin film by a modification of the film composition. With increasing Cr content (at the expense of Ni, the intrinsic negative creep error can be shifted towards zero. The second method is not based on the thin film itself but rather on a modification of the strain transfer from the polyimide carrier to the thin film. This is achieved by controlled cutting of well-defined deep trenches into the polymer substrate via a picosecond laser.

LTCC Substrates for High Performance Strain Gauges

2012 ◽  
Vol 2012 (CICMT) ◽  
pp. 000175-000180
Author(s):  
Bjoern Brandt ◽  
Marion Gemeinert ◽  
Ralf Koppert ◽  
Jochen Bolte ◽  
Torsten Rabe
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
High Performance ◽  
Coefficient Of Thermal Expansion ◽  
Strain Gauges ◽  
Gauge Factor ◽  
Metal Foil ◽  
Accuracy Class ◽  
Film Sensor ◽  
Load Cells

Recent advances in the development of high gauge factor thin-films for strain gauges prompt the research on advanced substrate materials. A glass ceramic composite has been developed in consideration of a high coefficient of thermal expansion and a low modulus of elasticity for the application as support material for thin-film sensors. Constantan foil strain gauges were fabricated from this material by tape casting, pressure-assisted sintering and subsequent lamination of the metal foil on the planar ceramic substrates. The sensors were mounted on a strain gauge beam arrangement and load curves and creep behavior were evaluated. The accuracy of the assembled load cells correspond to accuracy class C6. That qualifies the load cells for the use in automatic packaging units and confirms the applicability of the LTCC substrates for fabrication of accurate strain gauges. To facilitate the deposition of thin film sensor structures onto the LTCC substrates, the pressure-assisted sintering technology has been refined. By the use of smooth setters instead of release tapes substrates with minimal surface roughness were fabricated. Metallic thin films deposited on these substrates exhibit low surface resistances comparable to thin films on commercial alumina thin-film substrates. The presented advances in material design and manufacturing technology are important to promote the development of high performance thin-film strain gauges.

Research on Interfacial Diffusion Reliability Model of Thin Film Thermocouple

2021 ◽  
Vol 881 ◽  
pp. 77-85
Author(s):  
Dong Yang Lei ◽  
Yu Feng Sun ◽  
Yu Qing Xue ◽  
Guang Yan Zhao
Keyword(s):  
Thin Film ◽  
High Temperature ◽  
Diffusion Model ◽  
Great Influence ◽  
Protective Layer ◽  
Reliability Model ◽  
Interfacial Diffusion ◽  
Parallel Diffusion ◽  
High Temperature Measurement ◽  
Thin Film Thermocouple

Thin film thermocouple (TFTC) is widely used in high temperature measurement, which is of short response time, less heat residual and integrated structure. Due to the ultra-thin structure of TFTC, the interfacial diffusion has a great influence on its reliability when exposed to high temperature environment, which leads to its performance degradation. Taking thermocouple on the turbine blade as research object, the parallel diffusion model of multilayer thermocouple is proposed based on Fick’s law. The reliability model of the protective layer, the sensitive layer and the insulating layer are established in the basis of the parallel diffusion model. According to the logical correlation among the multilayer films of TFTC, the TTF model of TFTC is given. Finally, an example of reliability model based on multilayer diffusion is simulated by Monte Carlo method, which demonstrates the feasibility of the method and model.

An Approach on the Use of Co-Sputtered W-DLC Thin Films as Piezoresistive Sensing Materials

2021 ◽  
Vol 14 ◽  
Author(s):  
Gabriela Leal ◽  
Humber Furlan ◽  
Marcos Massi ◽  
Mariana Amorim Fraga
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Synthesis Method ◽  
Pressure Sensors ◽  
Strain Gauges ◽  
Gauge Factor ◽  
Diamond Like Carbon ◽  
Piezoresistive Sensors ◽  
Thin Film Resistors ◽  
Lift Off

Background: Miniaturized piezoresistive sensors, particularly strain gauges, pressure sensors, and accelerometers, have been used for measurements and control applications in various fields, such as automotive, aerospace, industrial, biomedical, sports, and many more. A variety of different materials have been investigated for the development of these sensors. Among them, diamond-like carbon (DLC) thin films have emerged as one of the most promising piezoresistive sensing materials due to their excellent mechanical properties, such as high hardness and high Young’s modulus. At the same time, metal doping has been studied to enhance its electrical properties. Objective: This article explores the use of co-sputtered tungsten-doped diamond-like carbon (W-DLC) thin films as microfabricated strain gauges or piezoresistors. Methods: Different serpentine thin-film resistors were microfabricated on co-sputtered W-DLC thin films using photolithography, metallization, lift-off, and RIE (reactive ion etching) processes. In order to evaluate their piezoresistive sensing performance, gauge factor (GF) measurements were carried out at room temperature using the cantilever beam method. Results: GF values obtained in this study for co-sputtered W-DLC thin films are comparable to those reported for W-DLC films produced and characterized by other techniques, which indicates the feasibility of our approach to use them as sensing materials in piezoresistive sensors. Conclusion: W-DLC thin films produced by the co-magnetron sputtering technique can be considered as sensing materials for miniaturized piezoresistive sensors due to the following key advantages: (i) easy and well-controlled synthesis method, (ii) good piezoresistive properties exhibiting a GF higher than metals, and (iii) thin-film resistors formed by a simple microfabrication process.

Direct Deposition of Thin-Film Strain Gauges with a New Coating System for Elevated Temperatures

2020 ◽  
Author(s):  
Rico Ottermann ◽  
Daniel Klaas ◽  
Folke Dencker ◽  
Marc Christopher Wurz ◽  
Dominik Hoheisel ◽  
...  
Keyword(s):  
Thin Film ◽  
Elevated Temperatures ◽  
Strain Gauges ◽  
Coating System ◽  
Direct Deposition

High-temperature thin-film strain gauges

1993 ◽  
Vol 37-38 ◽  
pp. 328-332 ◽  
Author(s):  
P. Kayser ◽  
J.C. Godefroy ◽  
L. Leca
Keyword(s):  
Thin Film ◽  
High Temperature ◽  
Strain Gauges

STRAIN SENSITIVITY AND TEMPERATURE INFLUENCE OF NICHROME (80/20 wt.%) THIN FILM FABRICATED BY MAGNETRON SPUTTERING

2007 ◽  
Vol 21 (21) ◽  
pp. 3719-3731 ◽  
Author(s):  
JIANWU YAN ◽  
JICHENG ZHOU
Keyword(s):  
Thin Film ◽  
Magnetron Sputtering ◽  
Thermal Annealing ◽  
Strain Gauges ◽  
Gauge Factor ◽  
Temperature Influence ◽  
Electromechanical Properties ◽  
Temperature Coefficient Of Resistance ◽  
Atomic Force ◽  
Resistance Stability

The electromechanical properties of nichrome ( Ni – Cr 80/20 wt.%) used as a common material for application in thin film strain gauges have been studied. The surface topography and chemical composition of Ni – Cr thin films grown on the glass substrate by magnetron sputtering have been analyzed by atomic force microscope (AFM) and energy dispersive spectroscopy (EDS), respectively. The temperature coefficient of resistance (TCR) has been determined by a Nano-volt/Micro ohm meter. The gauge factor (FG) has been determined by the cantilever method. Low stable TCR values (22 ppm to 46 ppm in the 50–150°C temperature range) have been obtained. Resistance stability is achieved by rapid thermal annealing (RTA) at 300°C for 10 min combined with a 24 h thermal annealing (TA) at 150°C. The desired 45 Ω/m sheet resistance and a gauge factor of 2.6 have been attained for 40-nm-thickness films. The films have very small roughness of 2.1~4.4 nm.

Performance Characteristics of Additively Printed Strain Gauges Under Different Conditions of Temperature and High Stress Loads

2021 ◽  
Author(s):  
Pradeep Lall ◽  
Tony Thomas ◽  
Jinesh Narangaparambil
Keyword(s):  
Strain Gauge ◽  
High Stress ◽  
Consumer Electronics ◽  
Performance Characteristics ◽  
Curing Temperature ◽  
Strain Gauges ◽  
Gauge Factor ◽  
Direct Write ◽  
Commercial Strain ◽  
Silver Ink

Abstract Applications of printed sensors have increased to industrial, consumer electronics, and medical fields with the advancements in the technology of printing and the adaptability of ink. These sensors are used to monitor a variety of measurements, including temperature, humidity, strain, and sweat, with different systems. This paper studies the performance characteristics of additively printed strain sensors using a nScrypt machine with a direct-write printing technique. The ink used in this study is silver ink which is thermally cured and also has a solderable property. The thermal curing temperature and trace width of the printed silver trace is optimized for better performance in the strain measurements, shear load to failure, and resistivity. Once the printing characteristics of the trace are defined, strain gauges are printed on printed wiring boards (PWB) and are tested at different loading and temperature environments. The sustainability and repeatability of the sensor measurements at high-stress conditions are studied using combined temperature and vibration loads of up to 50 degrees Celsius and 10g acceleration levels. The strain characteristics of the printed strain gauges are studied by comparing them to a commercial strain gauge at a similar position on the test substrate. The repeatability and variation of the strain profile are studied with different conditions of temperature and acceleration conditions at different time instants during vibration. The gauge factor of the printed strain gauge is quantified using a 3-point bending experiment with printed and commercial strain gauges at symmetrical locations of the substrate.

Influence of Sputtering Temperature and Layer Thickness on the Electrical Performance of Thin Film Strain Sensors Consisting of Nickel-Carbon Composite

2019 ◽  
Vol 809 ◽  
pp. 413-418
Author(s):  
Christos Karapepas ◽  
Daisy Nestler ◽  
Guntram Wagner
Keyword(s):  
Thin Film ◽  
Layer Thickness ◽  
Carbon Composite ◽  
Operating Conditions ◽  
Strain Sensors ◽  
Electrical Performance ◽  
Gauge Factor ◽  
Commercial Strain ◽  
Phase Development ◽  
Hybrid Laminates

Hybrid laminates consisting of fibre-reinforced thermoplastic films and metallic thin sheets are successively replacing thermoset based systems due to their obvious advantages of higher formability and aptitude for mass production. In order to monitor the material under operating conditions, hybrid laminates need to be equipped with smart sensor units. Artifact-free integration of commercial strain gauges into hybrid laminates is almost impossible. Therefore, a new thin film strain sensor based on a PVD sputtering process was developed.The aim of this work was to evaluate the influence of the layer thickness as well as the elevated temperature during the sputtering process on the electrical performance of Ni-C strain sensors. The Ni-C films with different layer thickness and different sputtering temperatures manufactured by means of a magnetron sputtering process were investigated for the sheet resistance and the change of temperature coefficients of resistance. In addition, Raman spectroscopy was utilized to investigate the phase development with regard to different sputtering temperatures. It can be seen that the gauge factor gets doubled while optimizing the layer thickness. When the sputtering temperature was increased, the graphitic phase formation was preferred and the impurities were reduced. These results are discussed in this paper and appropriate solution concepts are provided.

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