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1 – 10 of 237Busi Rambabu and Y. Srinivasa Rao
The purpose of this paper is to study high-voltage interactions in polymer thick-film resistors, namely, polyvinyl chloride (PVC)-graphite thick-film resistors, and their…
Abstract
Purpose
The purpose of this paper is to study high-voltage interactions in polymer thick-film resistors, namely, polyvinyl chloride (PVC)-graphite thick-film resistors, and their applications in universal trimming of these resistors.
Design/methodology/approach
The authors applied high voltages in the form of pulses and impulses of various pulse durations and with different amplitudes to polymer thick-film resistors and observed the variation of resistance of these resistors with high voltages.
Findings
The paper finds that high voltages can be used for trimming of polymer thick-film resistors in both directions, i.e. upwards and downwards.
Research limitations/implications
The research implication of this paper is that polymer thick-film resistors can be trimmed downwards or upwards practically using this method.
Practical implications
The practical implications of this paper is that one can trim the polymer thick-film resistors, namely, PVC–graphite thick-film resistors, in both directions, i.e. upwards and downwards, by using this method.
Originality/value
The value of the paper is in showing that high voltages can be used to trim downwards and also upwards in the case of polymer thick-film resistors. This type of trimming is called universal trimming, developed first time for polymer thick-film resistors.
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Kandagaddla Venkatasubrahmanayam, Busi Ram Babu, Billa Poornaiah and Yarravarapu Srinivasa Rao
The purpose of this paper is to study the microwave interactions in polymer thick film resistors, namely, polyvinyl chloride (PVC)-graphite thick film resistors, and its…
Abstract
Purpose
The purpose of this paper is to study the microwave interactions in polymer thick film resistors, namely, polyvinyl chloride (PVC)-graphite thick film resistors, and its applications in trimming of these resistors.
Design/methodology/approach
We applied microwave radiation in the form of pulses of various pulse durations and with different powers to polymer thick film resistors and observed the variation of resistance of these resistors with microwave radiation.
Findings
The paper finds that microwave radiation can be used for trimming of polymer thick film resistors.
Research limitations/implications
The research implication of this paper is that polymer thick film resistors can be trimmed practically using this method.
Practical implications
The practical implication of this paper is that we can trim the polymer thick film resistors, namely, PVC-graphite thick film resistor, by using this method.
Originality/value
The value of the paper is in showing that microwave radiation can be used to trim downwards in the case of high-value resistors and trim upwards in the case of low-value resistors.
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The paper aims to study the variation of electrical properties like electrical resistivity and current noise of a polymer thick film resistor, namely, PVC‐graphite thick film…
Abstract
Purpose
The paper aims to study the variation of electrical properties like electrical resistivity and current noise of a polymer thick film resistor, namely, PVC‐graphite thick film resistor, with parameters such as volume fraction, grain size, temperature and high voltage.
Design/methodology/approach
A model is proposed to explain the observed variations, which assumes that the texture of the polymer thick film resistor consists of insulator granules coated with conducting particles and also having cavities. The resistivity of these resistors is controlled mainly by the contact resistance between the conducting particles and the number of contacts each particle with its neighbors.
Findings
The variation of resistivity with temperature and high voltage is explained with the help of the model and it is attributed to the change in contact area and number of contacts. The current noise of these resistors is controlled mainly by the average relative resistance fluctuations between the conducting particles and the number of contacts each particle with its neighbors.
Originality/value
The variation of current noise with high voltage has also been explained with the help of this model and it is attributed to the change in number of conducting particles and conducting layers.
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Janusz Borecki, Aneta Araźna, Kamil Janeczek, Jerzy Kalenik, Michał Kalenik, Wojciech Stęplewski and Rafał Tarakowski
Nowadays, using of material properties for monitoring of phenomena occurring in the surrounding environment is very desirable. Taking into account the dynamic development of…
Abstract
Purpose
Nowadays, using of material properties for monitoring of phenomena occurring in the surrounding environment is very desirable. Taking into account the dynamic development of Internet of Things and the technological development of printed electronics, research into the using of printed electronic components for sensor applications can be one of the most prominent directions of searching for new innovative solutions. Among others, it is possible to apply them to produce the strain gauges, as well as for construction of advanced sensors for medical applications. The goal of this paper is to present the possibilities and using different constructions of embedded polymer thick-film resistors as the sensors of tension or strain.
Design/methodology/approach
The investigations were based on the polymer thick-film resistors made of carbon or carbon–silver inks printed on copper pads made on FR-4 material on two sides. The longitudinal samples laminated with resin-coated copper foil material and without lamination were bent on a strength machine. During the tests, the resistors depending on their placement were stretched or compressed. Some of the samples were also tested under high pressure. Under the influence of applied stresses, there was a reversible change in electrical resistance, which was monitored.
Findings
The study showed that the polymer thick-film resistors are characterized by a measurable piezoresistive effect. By analyzing the value of the observed resistance changes, a magnitude of strain or pressure can be worked out. During the bending, the piezoresistive effect depends on the location and orientation of the resistor. After stopping of the mechanical strains, the electrical resistance of the resistive elements does not return exactly to the initial value. This is probably related to the substrate material and the resistive paste composition. The results are very promising and further research will be done.
Originality/value
The results provided information about the piezoresistive effect of polymer thick-film resistors printed on the deformable substrate which could be interesting for engineers involved in printed sensor development dedicated for different fields of application. This phenomenon can be used to manufacturing cheap and uncomplicated sensors to monitor deformation. There are several aspects to be solved, but with the use of new types of resistive pastes and substrates, there is a potential possibility of using such resistors as sensors.
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Polymer thickfilm (PTF) resistors have been effectively used for many years in consumer goods liketimers, motor controls, computers and a wide variety of high performance…
Abstract
Polymer thick film (PTF) resistors have been effectively used for many years in consumer goods like timers, motor controls, computers and a wide variety of high performance equipment. The potential for this technology has reached only a small portion of the market; its full potential is still to be determined. The cost savings relationship of printed resistors should be considered by factoring the design and the number of resistors printed. Printed resistor savings vs discrete component costs can be a factor of three. This is dependent on the number of printed resistors per board of the same sheet resistance (based on 400 printed resistors of the same sheet resistant values on a 18 × 24 panel vs discrete components). By minimising the printing operations, resistor costs will be effectively controlled. Resistive ranges of thick film material are from 1 ohm to 10 Mega Ohm.The printing quality of resistors may vary from 10‐20%; however, resistors may be trimmed to 1% in value. Many values of resistors may be achieved with the same decade of resistor pastes. The determining factor is the design and layout of the circuit. The power rating of the printed resistor is proportional to the geometric surface area and is highly dependent on the substrate selection. The ability for resistors to be printed and buried into the multilayer will give design engineers more flexibility in active circuit density. Up to a 30% increase in surface area may be realised if resistors are buried into the inner layer of the PCB or under other surface components.
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The purpose of this paper is to study the variation of the temperature coefficient of resistance (TCR) of polymer thick film resistors, namely, PVC‐graphite thick film resistors…
Abstract
Purpose
The purpose of this paper is to study the variation of the temperature coefficient of resistance (TCR) of polymer thick film resistors, namely, PVC‐graphite thick film resistors, with parameters such as volume fraction, grain size, and high voltage.
Design/methodology/approach
A model is proposed to explain the observed variations, which assumes that the texture of the thick film resistors consists of insulator granules coated with conducting particles.
Findings
The paper finds that the TCR of these materials is controlled mainly by the contact resistance fluctuations between the conducting particles and the number of contacts each particle has with it neighbours. The variation of TCR with high voltage has also been explained with the help of this model and it is attributed to the changes in contact area and the number of contacts.
Originality/value
The value of the paper is in showing that apparently the TCR of polymer thick film resistors can be controlled by the expansion properties of the insulating medium. The variation of TCR with high voltage is also due to change in number of contacts between the conducting particles. These types of material may find applications in thermal sensors or as temperature control elements.
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Polymer thick film resistors are selected for various commercial applications in view of their performance, reliability and cost advantages. They are, however, only as efficient…
Abstract
Polymer thick film resistors are selected for various commercial applications in view of their performance, reliability and cost advantages. They are, however, only as efficient as the processing procedures used in their production. This paper outlines the factors that require control and presents test data relating to the important parameters. The value of laser trimming of polymer resistors is assessed.
Y. Srinivasa Rao and M. Satyam
This paper deals with the investigations carried out on the variation of current noise (1/f noise) in polymer thick film resistors, when they are subjected to pulse voltage…
Abstract
This paper deals with the investigations carried out on the variation of current noise (1/f noise) in polymer thick film resistors, when they are subjected to pulse voltage trimming. The current noise is measured in terms of noise index (micro volts of noise per volt of DC applied, in a decade of frequency) using Noise Meter Model 315 C manufactured by Quan‐Tech of New Jersey. It has been found that current noise decreases as the resistors are trimmed to lower values. An attempt has been made to explain the decrease in current noise with the trimming of resistors.
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Y. Srinivasa Rao and M. Satyam
The effects of material parameters and processing conditions on the resistance drop by high voltage discharge in PVC – graphite thick film resistors are studied in this paper. The…
Abstract
The effects of material parameters and processing conditions on the resistance drop by high voltage discharge in PVC – graphite thick film resistors are studied in this paper. The resistance drop increased upon an increase in graphite aggregate size, which is a function of material parameters and processing conditions. The resistance drop has been attributed to the dielectrophoretic motion of graphite particles in PVC by the application of high voltages to polymer thick film resistors.
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Paweł Osypiuk, Andrzej Dziedzic and Wojciech Stęplewski
The purpose of this paper is to determine the influence of mechanical factors (such as longitudinal elongation or cyclic compressive and tensile stresses) on electrical properties…
Abstract
Purpose
The purpose of this paper is to determine the influence of mechanical factors (such as longitudinal elongation or cyclic compressive and tensile stresses) on electrical properties of thin- or thick-film resistors or conductors.
Design/methodology/approach
All test samples were made on Kapton foil. Copper foil or silver-based polymer thick-film conductive inks were used for fabrication of conductors. Resistive structures were made with the aid of two polymer thick-film resistive inks or OhmegaPly Ni-P resistive foil. Test structures differ not only in materials applied for resistors or conductors but also in geometrical shape of functional tracks (meanders consisted of many horse-shoes, semicircles, squares or triangles).
Findings
Presented results showed significant role of material on range of reversible resistance changes. But shape of test samples also affects relation between relative resistance changes and relative elongation.
Originality/value
In general, changes induced by cyclic compressive and stretching stresses were smaller than those caused by substrate elongation.
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