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1 – 10 of over 1000
Article
Publication date: 1 January 1993

H. Fick

Power electronics used in consumer product assemblies require thermal management. Several current products rely on ‘printed wiring’ designs. These have copper patterns…

Abstract

Power electronics used in consumer product assemblies require thermal management. Several current products rely on ‘printed wiring’ designs. These have copper patterns separated from a metal substrate by a performance dielectric. The acceptance of this design concept ensures the availability of insulated metal substrates (IMS) for these applications. Available design guides do not describe the design constraints forced on these assembly designs by the physical characteristics of the materials in use. The following three design issues are discussed in this paper: — Dielectric strength testing does not relate to the proof stress testing required for product agency approval. — There is a special case for conformal coating or the use of potting compounds when IMS assemblies are used. — The choice of the metal substrate is based on quantity, thermal coefficient of expansion and thermal conductivity, often in that order.

Details

Microelectronics International, vol. 10 no. 1
Type: Research Article
ISSN: 1356-5362

Article
Publication date: 1 January 1989

L.M. Leung and K.K.T. Chung

Traditional B‐staged epoxy film adhesives have been used as substrate attach adhesive for hybrid circuits. The advantages of using film adhesive instead of paste adhesive…

Abstract

Traditional B‐staged epoxy film adhesives have been used as substrate attach adhesive for hybrid circuits. The advantages of using film adhesive instead of paste adhesive are precise bond‐line, clean operation, ease of application for larger bonding area and possibility to automate the process for large volume production. Epoxy, in general, is more stable than polyurethane and is better in adhesion with no contamination problems in comparison with silicone. Traditional epoxy, however, has high bond strength and is therefore limited only to substrates with matched thermal expansion properties. Combining the advantages of excellent adhesion of epoxy and flexibility of rubbery substance, a low glass transition temperature (Tg) epoxy which is flexible in nature has been developed for bonding substrates with mis‐matched thermal expansion coefficient. The new epoxy adhesive is also designed to meet the requirements of MIL‐STD‐883C/5011 in application without sacrificing ionic purity, low outgassing, thermal conductivity and long‐term dielectric or conductive properties. The new flexible film adhesive, in both its insulating and conductive forms, has attracted new applications and designs that were not previously feasible. For example, the flexible film adhesive can be used to bond ceramic hybrids directly to a lower cost metal substrate such as aluminium or copper. Testing has been performed by users on the combination of alumina/aluminium for over 1000 thermal cyclings and shocks from −55 to 150°C for large area bonding (up to a maximum of 6 x 6 inches square). The cured flexible epoxy adhesive, while very pliable, also exhibits more than 1,000 to 2,000 psi lap‐shear strength (depending on the type of substrate) and withstands more than 15,000 g acceleration test.

Details

Microelectronics International, vol. 6 no. 1
Type: Research Article
ISSN: 1356-5362

Article
Publication date: 1 January 1986

J.I. Steinberg, S.J. Horowitz and R.J. Bacher

Modern complex integrated circuits require more input/output connections and operate at faster switching speeds and higher power levels than was the case before LSI and…

Abstract

Modern complex integrated circuits require more input/output connections and operate at faster switching speeds and higher power levels than was the case before LSI and VLSI devices. As a result, there is a need for packages with high electrical conductivity, low dielectric constant, high thermal conductivity, precise line resolution and low unit cost. Ideally, it should also be possible to include resistors and for the package to be manufactured in‐house for maximum control. Multilayer printed circuit boards, complex multilayer hybrid circuits and high temperature co‐fired ceramic packages have been used to accomplish the interconnection of complex ICs. A new technology has been developed which combines the benefits of thick film with the processing advantages of co‐fired ceramic. The thick film process begins with a bare substrate, usually 96% alumina, upon which gold, silver alloy or copper metallisation, and screen‐printable dielectric paste are applied. Processing is a series of printing and firing operations; the firing temperature is usually between 800°C and 1000°C. Interconnecting vias are typically formed by screen printing and are usually a minimum of 250 ?m (10 mil) in diameter. The high temperature co‐fired approach uses no substrate. Printing of tungsten, molybdenum or molymanganese metallisation is carried out on alumina tape dielectric. The vias are formed by mechanical punching and are typically a minimum of 200 ?m (8 mil) in diameter. A single firing is performed in a special atmosphere, usually at 1500°C. This paper describes a new materials system which consists of a tape dielectric and gold, silver and silver/palladium inner layer and via fill conductor compositions. Circuits and packages made with the system are fired in an air atmosphere in standard thick film furnaces and are compatible with other conventional thick film materials. The process for making these parts is described and critical process parameters are identified. The results of reliability testing under temperature, humidity and bias are discussed and supporting microstructural analysis is presented.

Details

Microelectronics International, vol. 3 no. 1
Type: Research Article
ISSN: 1356-5362

Article
Publication date: 2 July 2018

Arkadiusz Dabrowski, Przemyslaw Rydygier, Mateusz Czok and Leszek Golonka

The purpose of this study was to design, fabricate and test devices based on transformers integrated with low-temperature co-fired ceramic (LTCC) modules with isolation…

Abstract

Purpose

The purpose of this study was to design, fabricate and test devices based on transformers integrated with low-temperature co-fired ceramic (LTCC) modules with isolation between primary and secondary windings at the level between 6 and 12 kV.

Design/methodology/approach

Insulating properties of the LTCC were examined. Dielectric strength and volume resistivity were determined for common LTCC tapes: 951 (DuPont), 41020, 41060 (ESL), A6M (Ferro) and SK47 (KEKO). According to the determined properties, three different devices were designed, fabricated and tested: a compact DC/DC converter, a galvanic separator for serial digital bus and a transformer for high-voltage generator.

Findings

Breakdown field intensity higher than 40 kV/mm was obtained for the test samples set, whereas the best breakdown field intensity of about 90 kV/mm was obtained for 951 tape. The materials 41020 and 951 exhibited the highest volume resistivity. Fabricated devices exhibited safe operation up to a potential difference of 10 kV, limited by minimum clearance. Long-term stability was assured by over 20 kV strength of inner dielectric.

Practical implications

This paper contains description of three devices made in the LTCC technology for application in systems with high-voltage isolation requirement, for example, for power or railway power networks.

Originality/value

The results show that LTCC is a suitable material for fabrication of high-voltage devices with integrated passives. Technology and properties of three examples of such devices are described, demonstrating the ability of the LTCC technology for application in reliable high-voltage devices and systems.

Details

Microelectronics International, vol. 35 no. 3
Type: Research Article
ISSN: 1356-5362

Keywords

Article
Publication date: 1 June 2001

Igor Tičar, Jože Pihler, Oszkár Bíró and Kurt Preis

The term “partial discharges” (PD) is a common term for various phenomena: discharges at points or edges of cylindrical conductors, in gases and gas insulated devices…

Abstract

The term “partial discharges” (PD) is a common term for various phenomena: discharges at points or edges of cylindrical conductors, in gases and gas insulated devices, liquid insulation materials, at borders between different insulation materials and, of course, in solid dielectrics. These phenomena result in insulation breakdowns, various disturbances to the environment, and after longer periods, some large‐scale failures. This paper presents the results of theoretical research of the behavior of a system of medium voltage covered conductors. This research work has been elaborated by the use of computer aided electric field calculations. For the confirmation of theoretical findings, practical measurements of partial discharges have been made.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 20 no. 2
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 22 June 2012

Helmi Wasoh, Lee Yook Hengb, Fatimah Abu Bakar, Rahman Wagiran, Abu Bakar Salleh, Nor Azah Yusof, Norhisam Misrond and Fatin Hazimah Abdul Rahmane

The purpose of this paper is to describe a capacitive biosensor device consisting of an enzyme electrode and a simple detector which has been developed for histamine measurement.

Abstract

Purpose

The purpose of this paper is to describe a capacitive biosensor device consisting of an enzyme electrode and a simple detector which has been developed for histamine measurement.

Design/methodology/approach

In this analysis, degradation of histamine through enzymatic reaction produces signal that is monitored using a simple detector equipped with “astable” multivibrator operation circuit (in capacitor‐resistor circuit).

Findings

Different frequency (f) readings have been obtained for glucose, alcohol and histamine in different concentration levels, showing the ability of this simple device system to measure their dielectric constant (k) as formulated by the equation f=(1.44d)/ [kA (R1+2R2)]. The analysis using smaller electrode gap (d) produces higher value of f, indicating that d, is directly proportional to f. For histamine, by using immobilized enzyme electrode, the results show that the change of dielectric properties during the 300‐second reaction period could also be monitored. A linear relationship is obtained between concentration and frequency from 50 to 200 ppm.

Practical implications

Based on this result, an enzyme electrode and “astable” operation circuits have the potential to be used in the development of a simple capacitive biosensor device.

Originality/value

The paper is an outcome of experimental work carried out to observe capacitive sensing behavior using an immobilized enzyme, to measure biological samples, especially histamine.

Details

Sensor Review, vol. 32 no. 3
Type: Research Article
ISSN: 0260-2288

Keywords

Article
Publication date: 7 September 2015

Ankita Pritam Praharaj, Dibakar Behera, Tapan Kumar Bastia and Arun Kumar Rout

This paper aims to focus on the development and study properties of bisphenol-A glycidyldimethacrylate (BisGMA) and ethylene–propylene–diene monomer (EPDM) blend-based…

Abstract

Purpose

This paper aims to focus on the development and study properties of bisphenol-A glycidyldimethacrylate (BisGMA) and ethylene–propylene–diene monomer (EPDM) blend-based nanocomposites containing amine-functionalised multi-walled carbon nanotubes (MWCNT-NH2) as a compatibiliser.

Design/methodology/approach

First, BisGMA was synthesised from epoxy and methacrylic acid followed by the amine functionalisation of MWCNTs. A novel two-roll milling technique was then conducted to prepare nanocomposite specimens with MWCNT-NH2 as compatibiliser. Effect of MWCNT-NH2 content on the mechanical, thermal, electrical, corrosive and water absorption properties of the nanocomposites was investigated and results have been reported.

Findings

The results of the present work reveal that MWCNT-NH2 acts as a potential compatibiliser and nanofiller in BisGMA/EPDM blend-based nanocomposites. The authors report here that the nanocomposites exhibit improved mechanical, thermal and electrical properties with increased addition of MWCNT-NH2. Moreover, desirable results are obtained at 5 phr of nanofiller loading beyond which the properties deteriorate due to particle agglomeration. The nanocomposites display negligible corrosion and water absorption characteristics. Thus, the above fabricated nanocomposites with optimum compatibiliser content can serve as low-cost structural, thermal and electrical materials which can also be utilised in corrosive and moist environments.

Research limitations/implications

The present investigation has come up with the successful and cost-effective fabrication of BisGMA/EPDM blend-based nanocomposites with optimum nanofiller/compatibiliser (MWCNT-NH2) content that can be used for a wide range of structural, thermal and electrical projects, as it is corrosion and moisture resistant. It is also the most durable from the mechanical point of view.

Originality/value

The above nanocomposites have never been designed before.

Details

Pigment & Resin Technology, vol. 44 no. 5
Type: Research Article
ISSN: 0369-9420

Keywords

Article
Publication date: 12 April 2018

Ramesh S., M.P. Jenarthanan and Bhuvanesh Kanna A.S.

The purpose of this paper is to investigate the performance of powder-mixed electric discharge machining (PMEDM) using three different powders which are aluminium (Al)…

Abstract

Purpose

The purpose of this paper is to investigate the performance of powder-mixed electric discharge machining (PMEDM) using three different powders which are aluminium (Al), silicon carbide (SiC) and aluminium oxide (Al2O3). Besides that, the influence of different tool materials was also studied in this experimental investigation. Hence, the work material selected for this purpose was AISI P20 steel and tool materials were copper, brass and tungsten. The performance measures considered in this work were material removal rate (MRR), tool wear rate and radial over cut (ROC).

Design/methodology/approach

The process variables considered in this study were powder types, powder concentration, tool materials, peak current and pulse on time. The experimental design, based on Taguchi’s L27 orthogonal array, was adopted to conduct experiments. Significant parameters were identified by performing the analysis of variance on the experimental data.

Findings

Based on the analysis of results, it was observed that copper tool combined with Al powder produced maximum MRR (58.35 mm3/min). Similarly, the Al2O3 powder combined with tungsten tool has resulted least ROC (0.04865 mm). It was also observed that wear rate of tungsten tool was very low (0.0145 mm3/min).

Originality/value

The experimental investigation of PMEDM involving three different powders (Al, SiC and Al2O3) was not attempted before. Moreover, the study of influence of different tool materials (Cu, brass and W) together with the different powders on the electric discharge machining performance was very limited.

Details

Multidiscipline Modeling in Materials and Structures, vol. 14 no. 3
Type: Research Article
ISSN: 1573-6105

Keywords

Article
Publication date: 1 September 1997

J. Fjelstad

This article comprises Chapter 6 from the recently published book ‘An Engineer’s Guide to Flexible Circuit Technology by J. Fjelstad

383

Abstract

This article comprises Chapter 6 from the recently published book ‘An Engineer’s Guide to Flexible Circuit Technology by J. Fjelstad

Details

Circuit World, vol. 23 no. 3
Type: Research Article
ISSN: 0305-6120

Keywords

Article
Publication date: 1 February 1992

A. Derebail, K. Srihari and G. Westby

The last decade witnessed the increasing use of Surface Mount Technology (SMT) in the assembly of Printed Circuit Boards (PCBs). This fact coupled with increasing…

Abstract

The last decade witnessed the increasing use of Surface Mount Technology (SMT) in the assembly of Printed Circuit Boards (PCBs). This fact coupled with increasing component densities, decreasing component pitch, and the need for reliable PCBs has focused attention on the critical components of the manufacturing process including the adhesive used. Components used in PCBs manufactured using SMT, which are to be wave soldered, must be adhesively attached to the board so that they remain in place during the wave soldering process. Utilisation of non‐conducting adhesives for the attachment of electronic components prior to wave soldering has become common throughout the electronics manufacturing industry. The knowledge based adhesive selection adviser described in this paper assists the user (process engineer) in the selection of adhesives for wave soldering of surface mount components. In addition to guiding the user through the adhesive selection process, it provides dispenser related information. This ‘advice’ is derived from the restrictions imposed by the user (including the user's facility temperature), material property requirements, productivity measures and the adhesive dispensing method. The adhesive selection adviser helps the user understand the relationships that need to be considered during adhesive selection. It is applicable to any existing SMT line that uses adhesives within the commercial PCB manufacturing domain.

Details

Soldering & Surface Mount Technology, vol. 4 no. 2
Type: Research Article
ISSN: 0954-0911

1 – 10 of over 1000