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1 – 10 of over 1000Busi 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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M. Hrovat, D. Belavič and A. Markošek
The direct overlapping of thick film NTC thermistors and resistors was attempted to enable the trimming of NTC thermistors to relatively narrow tolerances with little influence on…
Abstract
The direct overlapping of thick film NTC thermistors and resistors was attempted to enable the trimming of NTC thermistors to relatively narrow tolerances with little influence on beta factors. Different combinations of 1 kohm/□ thick film NTC material (4993, Remex) and 1 and 10 kohm/□RuO2 and ruthenate based thick film resistors (HS‐80 series, Du Pont), fired either together or separately, were tested. The sheet resistivities, TCR and beta factors of these combinations were measured. Microstructures were investigated by SEM and analysed by EDS. The results, i.e., the large decrease of sheet resistivities (up to ten times) and a resistivity vs. temperature dependence which changed from negative to positive TCR for some combinations, indicate the interaction between NTC materials and resistors during the firing process. These interactions are more distinctive for materials fired together. In all cases the beta factors were lower than calculated. Based on these experiments, the ‘best’ thick film resistor paste for NTC/resistor combination (HS‐8041, Du Pont) was chosen. Several layouts with partially or entirely overlapped NTC thermistors/resistors were designed. Unprotected, glass protected or organic protected circuits were laser trimmed. The resistivities and beta factors were measured as a function of resistor geometries and laser cut lengths. The results obtained demonstrated that NTC thermistors, partially overprinted with an ‘ordinary’ thick film resistor, can be trimmed to tolerances around 0.5% without any special precautions during trimming.
Wojciech Steplewski, Andrzej Dziedzic, Janusz Borecki, Grazyna Koziol and Tomasz Serzysko
The purpose of this paper is to investigate the influence of parameters of embedded resistive elements manufacturing process as well as the influence of environmental factors on…
Abstract
Purpose
The purpose of this paper is to investigate the influence of parameters of embedded resistive elements manufacturing process as well as the influence of environmental factors on their electrical resistance. The investigations were made in comparison to the similar constructions of discrete chip resistors assembled to standard printed circuit boards (PCBs).
Design/methodology/approach
The investigations were based on the thin-film resistors made of NiP alloy, thick-film resistors made of carbon or carbon-silver inks as well as chip resistors in 0402 and 0603 packages. The polymer thick-film resistive films were screen-printed on the several types finishing materials of contact terminations such as copper, silver, and gold. To determine the sensitivity of embedded resistors versus standard assembled chip resistors on environmental exposure, the climatic chamber was used. The measurements of resistance were carried out periodically during the tests, and after the exposure cycles.
Findings
The results show that the change of electrical resistance of embedded resistors, in dependence of construction and base material, is different and mainly not exceed the range of 3 per cent. The achieved results in reference to thin-film resistors are comparable with results for standard chip resistors. However, the results that were obtained for thick-film resistors with Ag and Ni/Au contacts are similar. It was not found the big differences between resistors with and without conformal coating.
Research limitations/implications
The studies show that embedded resistors can be used interchangeably with chip resistors. It allows to save the area on the surface of PCB, occupied by these passive elements, for assembly of active elements (ICs) and thus enable to miniaturization of electronic devices. But embedding of passive elements into PCB requires to tackle the effect of each forming process steps on the operational properties.
Originality/value
The technique of passive elements embedding into PCB is generally known; however, there are no detailed reports on the impact of individual process steps and environmental conditions on the stability of their electrical resistance. The studies allow to understand the importance of each factor process and the mechanisms of operational properties changes depending on the used materials.
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Marko Hrovat, Darko Belavič, Jaroslaw Kita, Janez Holc, Silvo Drnovšek, Jena Cilenšek, Leszek Golonka and Andrzej Dziedzic
Aims to evaluate different thick‐film materials for use in strain sensors and temperature sensors on low‐temperature co‐fired ceramic (LTCC) substrates.
Abstract
Purpose
Aims to evaluate different thick‐film materials for use in strain sensors and temperature sensors on low‐temperature co‐fired ceramic (LTCC) substrates.
Design/methodology/approach
LTCC materials are sintered at the low temperatures typically used for thick‐film processing, i.e. around 850°C, The thick‐film resistor materials for use as strain and temperature sensors on LTCC tapes are studied. Thick‐film piezo‐resistors in the form of strain‐gauges are realised with 10 kΩ/sq. 2041 (Du Pont)and 3414‐B (ESL), resistor materials; thick‐film temperature‐dependent resistors were made from PTC 5093 (Du Pont), and NTC‐4993 (EMCA Remex) resistor materials.
Findings
The X‐ray spectra of the 2041 and 3414‐Bb low TCR resistors after drying at 150°C and after firing display more or less the same peaks. The electrical characteristics of 2041 resistors fired on alumina and LTCC substrates are similar indicating that the resistors are compatible with the LTCC material. After firing on LTCC substrates the sheet resistivities and TCRs of the 3414‐B resistors increased. Also, there is a significant increase in the GFs from 13 to over 25.
Originality/value
Investigates the compatibility of thick‐film materials and the characteristics of the force and temperature sensors.
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Wojciech Steplewski, Andrzej Dziedzic, Janusz Borecki, Grazyna Koziol and Tomasz Serzysko
The purpose of this paper is to investigate the thermal behaviour of thin- and thick-film resistor with different dimensions and contacts embedded into printed circuit board (PCB…
Abstract
Purpose
The purpose of this paper is to investigate the thermal behaviour of thin- and thick-film resistor with different dimensions and contacts embedded into printed circuit board (PCB) and compare them to the similar constructions of discrete chip resistors assembled to standard PCBs.
Design/methodology/approach
In investigations the thin- and thick-film embedded resistors with the bar form in different dimensions and configurations of contacts as well as rectangular chip resistors in package 0603 and 0402 were used. In tests were carried out the measurements of dissipated power in temperature of resistor about 40°C, 70°C and 155°C. The power dissipation was calculated as a multiplying of electrical current flowing through the resistor with voltage across the resistor. The dissipation of heat generated by electrical current flowing through resistors was examined by means of the FLIR A320 thermographic camera with lens Closeup×2 and the power source.
Findings
The results show that, in case of chip resistors, the intensity of heat radiation strongly depends on dimensions of copper contact lands and also depends on the dimensions of the resistor. In case of embedded resistors, with comparable dimensions to chip resistors, they have lower ability to power dissipation, as well as the copper contact lands dimensions have lower influence. The thermal radiation through resin material is not as effective as it is in case of resistors assembled on PCB. However, the embedded thick-film resistors, especially made of paste Minico M2010, have already the similar parameters to 0402 chip resistors.
Research limitations/implications
Research shows that embedded resistors can be used interchangeably with SMD resistors it allows to open up space on the surface of PCB, but it should be taken into account the lower energy dissipation capabilities. It is suggested that further studies are necessary for accurately determining the thermal effects and investigate the structures of embedded passive components that allow for better heat management.
Originality/value
Thermal stability of embedded resistors during operation is a critical factor of success of embedded resistor technology. The way of power dissipation and heat resistance are one of the important operating parameters of these components. The results provide information about the power and the energy dissipation of embedded thin- and thick-film resistors compared to the standard surface mount technology.
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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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This paper gives a popular introduction to thin film and some reasons for using this technology. The miniaturisation techniques at Brel & Kjaer are described and the background…
Abstract
This paper gives a popular introduction to thin film and some reasons for using this technology. The miniaturisation techniques at Brel & Kjaer are described and the background for the work with thin film techniques is given. The company's method of realising thin film circuits is described by going through the resistor materials, resistor design and photolithography and etching steps. The kind of equipment needed and what B & K use to make prototypes and small scale production are shown. TCR‐values and the resistor stability after 10,000 hours at different environmental exposures are given. Examples of applications with single layer and double layer structures are shown. A thick film circuit is transformed to thin film, and the size reduction can be seen. Finally, for this circuit, the cost calculations are stated for both versions.
H. Diletti, J.R. Noser and G.J. Sele
In hybrid technology, components (e.g., ICs, capacitors, resistor chips) are mounted onto a thin or thick film circuit. Bare chip resistors are usually incorporated into…
Abstract
In hybrid technology, components (e.g., ICs, capacitors, resistor chips) are mounted onto a thin or thick film circuit. Bare chip resistors are usually incorporated into hermetically sealed hybrid circuits (die and wire bonding). Encapsulated chip resistors or chip resistors with a protective layer are required in the case of non hermetic sealing (flip chip soldering, surface mounting). The electrical performance of resistor chips with and without polyimide protective coating was investigated and is compared. This investigation was performed on NiCr based and Ta2N thin resistive films.
Percy Chinoy, Marc Langlois, Raj Hariharan, Mike Nelson, Anthony Cox and Tony Ridler
Embedded passives technologies can provide benefits of size, performance, cost, and reliability to high density, high‐speed designs. A number of embedded passive technology…
Abstract
Embedded passives technologies can provide benefits of size, performance, cost, and reliability to high density, high‐speed designs. A number of embedded passive technology solutions are available to the designer. Based on our experience with Rohm and Haas's thin‐film, high‐ohmic, InSiteTM embedded resistor materials (500 and 1000 Ω/sq), this paper provides some guidelines for selecting the appropriate embedded resistor technology and implementing it at a board fabricator. The design of embedded resistors, and the trade‐offs between resistor size, tolerance, and capability of board fabrication processes, are analyzed in detail. This paper also discusses selection of the appropriate embedded capacitor technology and introduces some initial results on Rohm and Haas's thin‐film, high‐Dk, InSite embedded capacitor material (200 nF/cm2).
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