bluuebunny/crossref_metadata_2025 huggingface dataset:
Teknecomp SpA, Cavaglià, Italy Quality and Quantity
Authors: Ellis B.N.
Published: February 2008

The Piedmont region in Northern Italy stretches from the Southern slopes of the Alps across the upper reaches of the alluvial Po valley to beyond Turin. It is very varied, but mainly of agricultural vocation, the principal produce being wine, rice and maize. From just North of Ivrea, where the Olivetti headquarters are situated, to Cavaglia, there is a long, forested moraine called La Serra, from which the plain starts. It was on a crystal‐clear December day that we visited the Teknecomp headquarters in Cavaglia: the snow‐covered Alps beyond La Serra looked as if they were only a short distance away in the dazzling sunlight, contrasted by the intense blue of the sky. It was hard to believe that only a couple of hours beforehand we were in a howling blizzard as we entered the Grand St Bernard tunnel!
Coates Circuit Products—Curtain Up on Imagecure
Authors: Cullen Lorna
Published: February 2008

A recent invitation by Coates Circuit Products to visit their Midsomer Norton facility gave Circuit World an opportunity for some interesting discussion and observation of what the company is offering the printed circuit industry.
Multilayer Circuit Boards with Molybdenum‐copper Metal Cores
Authors: Klemencic R. , Kny E. , Schmidt W.
Published: February 2008

The thermal management of printed circuit boards with high component density is increasingly becoming an important factor in the efficiency and reliability of electronic systems. A well‐proven technique, which has been used to produce multilayer circuit boards in quantity for several years, is to incorporate metal foils. The metal foils significantly improve heat removal and impart to the circuit board a thermal expansion behaviour closely matching that of the ceramic chip carrier. Roll‐clad Copper‐Invar‐copper (CIC) and copper‐molybdenum‐copper (CMC) foils have been used for this purpose. This paper reports on the first use of Mo30Cu foils, a material produced by powder metallurgy consisting of 70% molybdenum and 30% copper. Contraves AG manufacture SMT multilayer circuit boards incorporating Mo30Cu foils produced by Metallwerk Plansee GmbH. With regard to machinability and physical characteristics, Mo30Cu foils are superior to roll‐clad foils. First of all, the high elastic modulus of Mo30Cu foils is worth mentioning. It positively influences thermal stability and mechanical stiffness of the circuit board.
Determination of Thermal Stress Resistance of Copper Electroplate by Hot Rupture Tests
Authors: Zakraysek L.
Published: February 2008

Multilayer printed wiring boards make use of electrodeposited copper from two sources. Copper for conductor traces comes from foil manufacturers through thin laminate suppliers. Copper plating for layer interconnection is performed in an in‐house PTH process. Each source makes use of plating chemicals that are obtained from industry suppliers, but production requirements inherent in foil manufacture or in PTH processing can cause variations that occasionally result in copper deposits that exhibit poor hot strength. In a PWMLB, this can result in corner cracks, barrel cracks and inner layer cracks because some of the copper deposits will be susceptible to fissuring under thermal stress conditions. The phenomenon of hot fissuring is caused by the presence of co‐deposited impurities that degrade the hot strength of the deposit due to easy grain boundary separation at elevated temperatures. Stresses imposed by a solder float test, by soldering or by thermal cycling are then sufficient to cause microcracking in a copper plate that is in this condition. In this paper, the author describes how changes in the quality of copper plate can be monitored with a hot rupture mechanical test method. By testing plated copper samples before board fabrication, it is possible to detect and evaluate harmful effects such as fissuring before the electroplated copper is used in a PWMLB assembly.
Tin‐lead Composition—Its Control and Effect on Solderability
Authors: Luke D.A.
Published: February 2008

Alloys deposited from plating solutions vary in composition with changes in solution constituents and processing parameters. With the increasing demand on miniaturisation and quality of subsequent solder joints made to plated tin‐lead alloys, it is important to ensure stable deposit composition and also to know to what extent changes in operating conditions will affect the composition. This paper examines the major causes of changes in composition of deposits plated from solutions based on fluoboric acid and organic sulphonic acid. The methods available for measuring the deposit composition are also discussed.
High Performance Laminate Systems for High Speed Electronics Applications
Authors: Paulus J.R.
Published: February 2008

This paper reviews some of the technology trends making it necessary to take the performance of laminate materials into account when designing and fabricating high speed PWBs. It also reviews the available materials for current matched impedance circuitry and discusses the various combinations of polymer resins and reinforcements used in these applications. Additionally, it provides a look at the new materials technologies being applied to high speed applications and what candidates hold most promise for achieving greater signal speeds via lowered dielectric constant while maintaining the compatibility with existing fabrication processes.
Interrelating Surface Insulation Resistance Test Patterns
Authors: Chan A.S.L. , Shankoff T.A.
Published: February 2008

For reliable telecommunication systems, Bellcore recommends that Surface Insulation Resistance (SIR) be monitored at key points in printed wiring board and circuit pack manufacturing. The Bellcore SIR criteria are based on the old ‘Bell System’ test pattern having 0·025 inch conductor line widths, and 0·050 inch conductor spacings. Since divestiture, many equipment suppliers have suggested using different test patterns, or even conductors on actual product for SIR testing. Also, with the trend to high density packaging and smaller conductor spacings, the Bellcore pattern now represents old technology. This work confirms and advances prior work suggesting pattern translation based on the SIR per square concept. Essentially exact SIR per square correlation has been found over an order of magnitude of pattern conductor space widths. Critical experimental techniques to modify the FR‐4 epoxy surface appropriately and an important theoretical hypothesis involving shadowing (proven experimentally) are developed in this work.
Vibratory Agitation to Enhance Mass Transfer in Electrodeposition
Authors: Kalantary M.R. , Amadi S.A. , Gabe D.R.
Published: February 2008

A study has been carried out employing a vibratory motor, offering amplitudes of 0·4–4 mm at 50 Hz in acid copper sulphate as a model electrolyte in which α‐Al2O3 particles are suspended for co‐deposition, yielding a composite electrodeposit. Using a horizontal disc vibrator at the bottom of the container, perforated discs have been shown to give superior agitation and a laminar/turbulent transition has been identified. Incorporation of particles is a maximum at the transition. In the laminar regime Sh‐Re0·037 and in the turbulent regime Sh‐Re0·82. Mass transport enhancement was measured for a variety of disc and tank diameters and enhancement factors for electrodeposition of 3–40 times were obtained. In these circumstances a modified Reynolds number Re1 was employed Re1 = 100 ad2(d1−d2)/υd2 and, assuming a conventional dependence upon Sc, a full correlation of the type Sh1 = constant Re1a Sc0·33 was obtained where the constant took values of 10–40 and ‘a’ took values of 0·83–1·1 depending upon precise location within the tank of the mass transfer probe.
Erratum
Authors: Lea C.
Published: February 2008

This article has been withdrawn as it was published elsewhere and accidentally duplicated. The original article can be seen here: 10.1108/eb037680. When citing the article, please cite: C. Lea, (1989), “A Call for Action on CFC Usage”, Soldering & Surface Mount Technology, Vol. 1 Iss 2 pp. 69 - 70.
Depression Approaching from the Atlantic
Authors: Tyler Roger L.
Published: February 2008

One of the aspects of being in the consultancy business is that we have to do forecasting for our living. As somebody once said, ‘forecasting is fine when it comes to talking about the present, but the future gets a little bit more difficult’.
Internepcon UK, 1989
Authors: Cullen Lorna
Published: February 2008

To ‘report’ on this year's Internepcon, 14–16 March, at the NEC, Birmingham, is going to prove more difficult than anticipated. The average journalist would report on such an event—whether as a eulogy or critique—from the standpoint of the visitor, having time to saunter up and down the aisles, amass briefcasefuls of press releases, sniff out the genuinely new products from those merely flaunting a ‘New’ label, interrogate the occasional exhibitor regarding impressions, etc. Well, I too had hoped to follow this format, anticipating the occasional lull in activity. However, as an exhibitor, I found little opportunity to ‘escape’ from the Circuit World stand—even on Wednesday when I had the assistance of a colleague to share ‘booth‐duty’ (pardon the Americanism). This surely speaks volumes for the increased success of this year's event. Numbers of visitors undoubtedly seemed to be higher than in recent years. Of course, we should compare like with like and check this year's attendance figures against the figures for the last combined Packaging and Production Show held in Brighton in 1985. Even that comparison is not entirely valid either, as this year saw for the first time the running of Semiconductor International concurrently with the combined Internepcon Show and under exactly the same roof in Hall 5.
Three‐dimensional Moulded Printed Circuits
Authors: Whelan M.
Published: February 2008

The three‐dimensional moulded printed circuit board is no longer just a concept, but a vehicle ready to exploit the challenges of highly integrated and miniaturised electronic packages. Several types of technology now exist which enable circuitry to be built on three‐dimensional structures in varying degrees of complexity. This article is intended to review the developments of injection moulded printed circuit boards, some of the key advantages over conventional FR‐4 boards, the various processes and techniques involved in the 3‐D technologies, and finally to describe the most recent advancement, using a robotic laser technique.
Interlayer Alignment in Multilayer PCBs
Authors: Lodge K.J. , Pedder D.J.
Published: February 2008

A measurement tool, capable of monitoring misalignment of layers in multilayer printed circuit boards, is described. Its uses, limitations and its advantages for use in SPC and reliability predictions are highlighted.
‘Just in Time’ Cleaning Improves the Yields in Fine Line Circuit Manufacture
Authors: Hamilton S.
Published: February 2008

The purpose of this paper is to identify the major parameters which affect the chances of contamination occurring, and then to evaluate conventional cleaning techniques with respect to these factors. The paper will next describe a new approach to contamination control which minimises the risk of contamination in a cost‐effective manner. In conclusion, some aspects of the circuit board manufacturing process which are particularly sensitive to contamination and which may benefit from the application of ‘Just in Time’ cleaning are described.
Avoiding Electrolytic and Strain‐induced Shorting Mechanisms—A Review
Authors: Hitch T.T.
Published: February 2008

The paper describes two well‐known and occasionally confused mechanisms for degradation of electronic circuitry. Intended as a tutorial for individuals working in electronic packaging who have limited background in materials and little experience with these mechanisms, the paper defines and describes the two latent shorting phenomena. Major papers and conferences dealing with the phenomena are cited. Electrolytic or electrochemical shorting is an electrical field‐induced mechanism that can destroy the integrity of modern, densely packed circuits operated in the presence of moisture and ionic contaminants. Examples of copper migration to form electroplated shorts in both thick film hybrid multilayer and printed circuit multilayer boards are discussed, and common features to both systems are outlined. Related mechanisms that may occur with the simple electrochemical (metal plating) mechanisms to produce a broad array of electrical isolation breakdowns are also described. The closing of this part of the paper is a brief review of the Sarnoff‐developed RCA/GE multilayer copper materials system. By design this system solves the problems raised regarding thick film copper multilayer latent failure mechanisms. The discussion of whisker growth is limited to proper whiskers, including those that grow without the application of external stress, squeeze whiskers, and whiskers that result from classic electromigration. All of these grow from solid sources in contact with the whisker. The whisker growth direction is not electrical field related. Identification is made of Sn, Cd, Sb and Zn as the materials classically found to grow whiskers at room temperature. Avoiding the use of electroplated films of Cd, Sb and Zn in close proximity to electronic circuitry is encouraged, and the modern requirements that Sn films be used only after melting, or be alloyed with lead, and not on brass substrates are discussed. In more recent literature indium alloys have been identified as room temperature whisker growth systems. Finally, mechanical design to eliminate squeeze whisker shorting that can result from fasteners in contact with the above and other metals is briefly treated.
A Unique Way of Placing Via Hole Connections in the SMD Pads Gives Increased Routing Space on Printed Circuit Boards
Authors: Braun R.
Published: February 2008

Via holes in SMD solder pads normally disturb the flow of the solder during soldering. To avoid this, expensive processes whereby the holes are filled with solder cream are used by the assembler. The paper describes a technique which allows the designer to design ‘Vias in SMD Solder Pads’ and so gain additional routing space on the printed boards, yet maintaining good solderability, using standard soldering processes.
Defeating the Ozone Problem
Authors: Cullen Lorna
Published: February 2008

A highly successful one‐day conference was the outcome of the combined organisational efforts of the IMF PC Group and Dr Colin Lea at the National Physical Laboratory. Admittedly the theme heads the list of current ‘hot’ topics, but to attract over 250 delegates to a meeting at a busy time of year for the industry was evidence also of a well planned programme and effective promotion.
A Photoimageable Dielectric for Sequential PWB Fabrication
Authors: Knudsen P.D. , Brainard R.L. , Schell K.T.
Published: February 2008

As printed wiring boards move to thin laminate structures, there is growing interest in the use of photoimageable coatings to serve as dielectric. Shipley has developed a liquid photoimageable dielectric which combines liquid coating, imaging and plateability. This paper presents work using this material to produce electrolessly plated lines and blind vias, along with initial adhesion data. Some of the interesting properties of this material are: low dielectric constant, low moisture absorption and good compliance to stress. The material can be processed to provide a high Tg and high plated adhesion can be obtained using conventional swell and etch techniques. It can be imaged and processed using conventional printed circuit coating and imaging techniques. This material will offer a relatively low cost alternative to thin clad laminates and may find use for adding one or two layers to a conventional multilayer board or in providing surface topography for surface mount devices. The paper describes recent developments related to this dielectric and its use.
The Adhesion Promotion and Metallisation Process: The Critical Step in MID Manufacturing
Authors: Hunter P.
Published: February 2008

Like the conventional PCB, the Moulded Interconnect Device (MID), be it 2‐ or 3‐dimensional, will have, as its interconnection medium, conductive patterning or structuring upon the surface of the device. This interconnection pattern will, in the majority of MID products, take the form of a metal (usually copper) deposited upon the surface of the plastic. How this metal is deposited and remains attached to the surface is the critical step in the production of a MID. That is the bond, or adhesion, between plastic and the applied metal circuitry. Without a strong and reliable bond between circuitry and plastic it will not be possible to manufacture a MID with the characteristics of a conventional interconnection medium, the PCB, the technology it is probably replacing within the finished product. This paper describes the development of a chemical adhesion process, and how the selection of a suitable resin and its moulding parameters can influence the adhesion performance of the metallisation process.
X‐ray Inspection of Flip Chip Attach Using Digital Tomosynthesis
Authors: Rooks S. , Sack T.
Published: February 2008

To accommodate increasing levels of device integration at the chip level, circuit line densities in electronic packages are continually increasing. Greater circuit line density, in turn, necessitates a corresponding increase in package‐to‐board interconnection density, with I/O counts expected to reach over 600 by 1995. In conjunction with the upward trend in I/O counts are a complementary upward trend in clock speed and an opposing downward trend in package sizes driven by the need to provide more functionality in less space, particularly in notebooks and PCMCIA cards. To satisfy the requirements of increased I/O counts and clock speed, and reduced package sizes, various package‐to‐board interconnection technologies are being developed, such as flip chip attach (FCA) using C4 joints. However, FCA interconnections have a disadvantage of being very difficult, if not impossible, to visually inspect. Though automatic test equipment (ATE) can determine whether the package is functional, it cannot determine the quality and reliability of FCA interconnections. Of the possible inspection techniques available to assess the quality of FCA interconnections — differential laser thermal analysis, acoustic microscopy and cross‐sectional X‐ray radiography — only cross‐sectional X‐ray radiography is capable of accurate, automated inspection of production volumes. This paper will first examine the requirements for inspecting FCA joints and will then describe the various inspection alternatives, outlining their advantages and disadvantages. Having described the potential advantage of one particular cross‐sectional X‐ray technique, digital tomosynthesis, the paper will conclude with some cross‐sectional images of FCA and SMT joints taken by a digital tomosynthesis system being developed for the inspection of FCA joints.
Low Cost Solder Bumped Flip Chip MCM‐L Demonstration
Authors: Kelly M. , Lau J.
Published: February 2008

A low cost multichip module employing solder bumped flip chips mounted on an organic substrate was demonstrated. This functional prototype was used to help assess the preliminary feasibility of low temperature solder bumped flip chip applications, from wafer design, sourcing and bumping, substrate design and fabrication, to MCM‐L assembly.
IPC Printed Circuits Expo/38th annual meeting
Authors: Ellis Brian N.
Published: February 2008

This event is not just one event but a whole series of them running more or less concurrently. The main parts consist of meetings of the various IPC Technical Committees and their Working Groups, a number of Tutorials and Workshops, some Forums, a Technical Conference with 21 sessions and, of course, the Printed Circuits Expo. The last‐named is the second of its type, the first having been held in Boston last year. The only real problem with this series of events is that there is so much going on at any one time that it is impossible to split oneself into parts to attend them all or even a fraction of them. For example, on the Monday morning, there were 28 Committee and Task Group meetings, some of them lasting four hours, five Workshops and as many Tutorials. By Tuesday, the Conference and Expo had started, so there were fewer, only ten Committee meetings, one forum and three Paper Sessions in the Conference, and so on.
Irlandus Circuits Ltd, Craigavon, N. Ireland
Authors: Popkiss Doug
Published: February 2008

Situated on the southern shore of Lough Neagh, the largest freshwater lake in the British Isles, is the new city of Craigavon, home of PCB manufacturer, Irlandus Circuits. By way of contrast to typical industrial locations, Craigavon Borough boasts considerable unspoilt countryside, featuring the Oxford Island nature reserve, breathtaking parklands, warden organised bird‐watching, and a series of scenic walks along river and canal banks which form part of a network of paths across Northern Ireland called the Ulster Way.
The Chip Carrier, Universal Chip Support for High Level Integration
Authors: Val C. , Kersuzan G. , Dreyfus‐Alain B.
Published: February 2008

The ‘chip carrier’ or CC is an intermediate support, hermetically sealed or otherwise, (of alumina, beryllium oxide or plastic) requires to connect an integrated circuit chip with numerous output pins to the outside world. This carrier at present represents the best compromise in terms of technology and economy, because of the use of standard multi‐source chips and the simple testing it permits.
Comparative Study of Thick Film Dielectrics
Authors: Vermeirsch W.
Published: February 2008

Increasing density requirements urge the thick film hybrid manufacturers to print high resolution patterns and to consider the application of multilayer hybrids. The introduction of compact interconnection technologies such as TAB and chip carrier will no doubt accelerate this process. Paste manufacturers are carrying out research to develop inks suited for fine line printing. The properties of dielectric pastes, necessary for multilayer applications, have not been studied so extensively. A programme was initiated to compare various dielectrics in combination with various conductors. From the test programme two tests were found to be most significant for the dielectric's characterisation. These tests, in combination with an SEM‐study of surface and bulk porosity, permitted a quick and reliable selection of an appropriate dielectric paste to be made.
Thermal Expansion and Laser Trim Stability of Ruthenium Based Thick Film Resistors on Alumina and on Multilayer Dielectric
Authors: Taitl I.
Published: February 2008

Fired resistors exhibit variations which are minimised by abrasive and laser trimming. The latter may cause unstable behaviour which is further aggravated by thermal shock. The chemical structure of a thick film resistor is analysed with respect to mechanical stress, and the theoretical conclusion that the coefficient of thermal expansion of the resistor should be equal to or smaller than that of the substrate is verified experimentally. The thermal behaviour of ruthenium dioxide is examined and a range of CTE values are determined for materials of varying chemical composition. The relationship between CTE and post laser trimming stability is demonstrated on four thick film resistors which differ in thermal expansion. It is pointed out that formulations with high metallic content can absorb tensile stress by elastic deformation, thus minimising the formation or propagation of laser induced cracks.
Mounting Leadless Chip Carriers onto Printed Circuit Boards
Authors: Fishman D. , Cooper N.
Published: February 2008

It is reasoned that wide penetration of chip carriers into equipment for professional and commercial applications depends on developing methods for mounting the leadless types directly on to conventional polymer type printed circuit boards. The main problem to be overcome is fatigue failure of the solder joints due to the mismatch in thermal expansion, evidenced by poor thermal cycling performance. In this paper the thermal cycling performance is compared when four sizes of ceramic leadless chip carrier are mounted on a selection of printed circuit board materials ranging from the conventional to those specially formulated, either on the basis of matching the coefficient of thermal expansion of the chip carrier material, or to provide a layer of compliant elastomer material underneath the layer bearing the copper contact layer, so that strain due to thermal expansion mismatch is not transmitted to the solder layer. Over 400 thermal cycles (−55 to + 125°C) were recorded using proprietary versions of elastomer coated substrates. For appropriate applications the basis is thus laid for an economic and technically acceptable solution. The practical implications of two methods of soldering—wave (jet) and vapour phase—are also discussed.
A True Air Speed Sensor for Miniature Unmanned Aircraft
Authors: Beattie J.A.C.
Published: February 2008

This paper describes the development of a laboratory prototype true air speed sensor for use on unmanned aircraft. The sensor works on vortex shedding principles and has a digital output. The vortices are sensed by thick film thermistor elements that are non‐critical in the signal circuitry.
The Business of Thick Film
Authors: Sage M.G.
Published: February 2008

This paper looks at the growth, current situation and future of the thick film hybrid industry worldwide. The approach taken has been to regard the thick film hybrid as primarily a sub‐assembly, both from a commercial and technical point of view. This helps to identify those major features that have shaped the industry and will influence its future.
Editorial
Authors: Fairbairn Alan J. , Waterfield Brian
Published: February 2008

We, in the International Society for Hybrid Microelectronics, are reflecting the changes in our industry but we must also brace ourselves to accept the challenges. In our efforts within the Society to become more professional we have in fact initiated many changes and already faced many challenges. The Corporate Membership policy has been one whereby companies involved in all aspects of the hybrid microelectronic industry, suppliers, manufacturers and, of even greater importance, customers can become Corporate Members of ISHM and nominate two individual members to represent their interests. It was hoped that this would encourage more corporate backing for our projects which, if our annual exhibition, Hybrid MicroTech, is any guide, has been very successful. Our Corporate Members have beaten a path to our door in order to exhibit at this new Hybrid Microelectronics event, surely now becoming the premier meeting place for our industry in the UK.
Microjoining Developments for the Electronics Industry
Authors: Johnson K.I.
Published: February 2008

The dramatic expansion in the use and capability of electronic devices in recent years has been facilitated by the substantial development of production techniques. Modern electronic circuits as used in the computer, defence, aerospace, vehicle and domestic appliance industries contain a great many joints and these have to be made reliably and economically without degrading sensitive circuit components. This article describes the major microjoining developments currently of interest to the microelectronics industry, with emphasis on the work conducted by the microjoining section of The Welding Institute, much of which has been directly sponsored by the UK Ministry of Defence (DCVD).
Philosophy and Practice in Tolerancing Passive Components for Hybrid Circuits in ‘Long Life’ Electronic Equipment
Authors: Boswell D.
Published: February 2008

This paper reviews the need for a more realistic and professional approach by UK OEM circuit designers and hybrid engineers to the philosophy and practice of long life—‘total excursion’—tolerancing. It offers simple methods, including offset calculations, for both thick film resistors and multilayer ceramic chip capacitors (X7R), e.g., in B/T Class 1 and Class 2 applications. Acceptance of these principles enables improved product life for the same initial setting (selection) tolerance and width.
TCR's of Thick Film Resistors Produced in High Volume
Authors: Hauschild F.D.
Published: February 2008

In the manufacture of resistors with low TCR values it is found that difficulties start at TCR values of less than ±50 ppm/°C. This paper will show if ±50 ppm/°C is a realistic value for high volume production.
Enhanced Static Problems with Reduced MOS Chip Geometry
Authors: Molyneux Child J.W.
Published: February 2008

The escalating problem of electrostatic discharge damage to MOS devices, resulting from the need for a continual reduction in chip geometry, is examined, with data provided on the range of ESD susceptibility for various component families. It will clearly be of benefit to implement measures that will offer long‐term protection against device degradation.
CIT‐Alcatel, ‘Division Microélectronique (Hybride)’, France
Authors: Waterfield Brian
Published: February 2008

The CIT‐Alcatel Group, with a turnover of more than 10 billion French francs, is a subsidiary of the huge ‘Compagnie Générale d'Electricité’ and is deeply involved in the telecommunications industry. It is particularly known for its experience in digital techniques. 6000 of its 40,000 workforce are employed abroad, and with an increasing number of turnkey telecommunication systems installed in so many countries they will undoubtedly have a large share of the message‐handling and office automation markets in addition to direct speech business. Their E10, time‐division switching system ordered by 30 countries, alone represents 10·5 million subscriber lines to 1982.
Industry news
Authors: Gross Dennis , Waterfield Brian
Published: February 2008

As a result of reorganisation within the Company, AVX Limited have appointed Keith France as General Manager, Sales and Marketing. Previously General Manager, Sales, Europe, Mr France now assumes the added responsibility for the marketing of AVX products throughout Europe.
Ceramic‐Coated Copper Substrates for Hybrid Circuits
Authors: Kužel R. , Broukal J. , Bouše V. , Votruba Z.
Published: February 2008

Copper substrates covered with ceramic insulating coating were tested for their ability to be used in thick film technology. The ceramic coating was prepared by screen printing from a dielectric composition containing special glass and aluminium oxide and was fired at 820°C–1,000°C. The electrical properties of the coatings studied included voltage breakdown, surface and bulk insulation resistance and dielectric constant. Resistor compositions designed for use on ceramic substrates were screen printed, as on the substrates mentioned, on alumina or ceramic‐coated steel substrates and fired up to the required temperatures (820–875°C). The resistivity and TCR of the prepared resistors were measured in relation to firing temperature. The distribution of lead, bismuth, ruthenium, barium, palladium, silver and copper in the system resistor (or conductor) ceramic coating/copper substrate was investigated. Reference was made to the application of ceramic coatings on copper in other fields, e.g., in heavy‐current electronics.
The Influence of Microcracks on the Temperature Dependence of Resistance in Ruthenium Based Thick Film Resistors
Authors: Kozlowski J.M.
Published: February 2008

This paper presents a computer model which describes the influence of microcracks on the temperature dependence of resistance in thick film resistors. The tunnelling barrier model for a single particle‐barrier‐particle ‘unit cell’, proposed by Seager and Pike, is assumed. The model presented is based on an analysis of the critical percolation path that forms in the sample. It is shown that the growth in density of the microcracks induces a shift of the minimum resistance to higher temperatures, and that the value of this minimum decreases. The theoretical temperature dependences of resistance are compared with experimental data, obtained in the temperature range 295K–425K, for thick film resistors made using Du Pont 1421 and 1431 Birox resistor pastes.
Performances of Thick Film Resistors with Reduced Dimensions
Authors: Bellardo A. , Lovati G.
Published: February 2008

The results of a characterisation carried out on thick film resistors (TFRs) with dimensions reduced below the usual limits are reported in this paper. The test vehicle was a purpose‐designed test pattern with resistors whose dimensions reached a limit of 0·3 mm in length and 0·4 mm in width. The proposed aim of the work was to look for dimensional limits where TFRs could still give acceptable performances, though, if possible, keeping unchanged the materials system and the process conditions which are used in the authors' thick film hybrids facility.
Microelectronic Applications for Polymers: Structure‐Property Relationships
Authors: Rooney J.M.
Published: February 2008

The design of polymeric materials for microelectronic applications is based on the recognition that structural features in a polymer chain influence the physical properties of the polymer. Illustrations of structure‐property relationships are drawn from applications in lithography, dielectric interlayers and packaging. Among the properties discussed are resolution, plasma etch resistance, thermal stability, electrical properties, permeability, adhesion, mechanical properties and thermal expansion.
Ageing Mechanisms and Stability in Thick Film Resistors
Authors: Coleman M.
Published: February 2008

Thermal ageing experiments on various thick film resistor systems have shown that resistance change is caused by a number of different mechanisms with different time dependences. Three distinct types of behaviour have been identified: corrosion due to ambient attack; diffusion through resistor interfaces with conductor terminations or through the resistor top surface; and stress relief within the bulk of the resistor. Wherever possible the dominant mechanism has been identified and the activation energy and time dependence of the ageing process have been determined.
Hybrid Circuit Manufacture Using an Infra‐red Furnace and Standard Thick Film Materials
Authors: Aitken D.W. , Pittson R.W.
Published: February 2008

A fast firing infra‐red furnace has been evaluated with a standard thick film resistor series at a belt speed of 10 inches/minute giving a door‐to‐door time of 11 minutes. Results are given for a number of furnace profiles at this speed.
CTI and MEDL in Transatlantic Alliance
Authors: Waterfield Brian
Published: February 2008

Less than an hour from New York and just off the Long Island Freeway lies Farmingdale which, apart from containing a very large war cemetery, has a well ordered industrial park. Here on Smith Street is to be found CTI, an autonomous company within GEC's Marconi Electronic Devices Ltd.
ISHM—The international society
Authors: PAPSØE JØRGEN , Waterfield Brian
Published: February 2008

As I considered my theme for this editorial, I could not help asking myself just how International ISHM really is. Are we really part of one great family of engineers all preoccupied with exploiting a technology that is significant today and will be even more so in the future as more and more complex requirements for interconnect are contrived, or is the Society something to which each individual country or continent belongs for what can be got out of it at the present moment, with little thought of the advantages the true breadth of ISHM membership should offer? Today a large part of the electronics activity is centred around the transmission and utilisation of information, so surely we of all people should take some advantage of this and ensure that we communicate with each other as this after all is one of the original aims of the Society.
Reliability and Quality Assurance Basic Concepts and Their Application to Microcircuits
Authors: George A.H.
Published: February 2008

An understanding of reliability physics, failure analysis and failure mechanisms as applied to semiconductor technologies is essential in assessing microcircuit reliability. The use of valid thermal accelerated tests and the correct use of the data therefrom is crucial in assessing reliability. Improved technical data are required from most manufacturers if user analysis of accelerated testing is to be more easily and accurately carried out.
A Survey of Laser Trimming
Authors: Bancroft R.C.
Published: February 2008

This paper provides a technical background and overview of the rôle played by the computer controlled laser trimming system in the thick film industry.
Designing for Testability
Authors: Jacob G.W.
Published: February 2008

Semiconductor devices and systems containing them have become so complex that it is difficult and costly to test them adequately. The solution is to design them to be testable. In this the author considers testability cost trade‐offs, outlines the interrelationship of test programming and designing for testability, and presents several methods of designing for testability.
Chip Carrier Based Systems and their Testability
Authors: Maunder C. , Roberts D. , Sinnadurai N.
Published: February 2008

Testing has become one of the dominant costs in the process of bringing a product from initial conception to the market place. Because of this, it is now imperative that the impact of any technology change on the test process is considered at an early stage. In this light, the increasing trend towards the use of surface‐mounting techniques in the fabrication of electronic systems is examined, with particular emphasis on the consequences on product testing during design validation, manufacture and repair. The aim is to highlight areas in which new attitudes and replacements for traditional solutions will be needed if surface‐mounting techniques are to be as cost‐effective as possible.
Autronica Hybrids—Roros, Norway
Authors: Waterfield Brian
Published: February 2008

Situated to the south of Trondheim and just 50 kilometres from the Swedish border, Roros is a fine example of a small town which found that its traditional industry had come to an abrupt halt and, with that realisation, set to establishing alternative industry to provide employment for the inhabitants and income for the businesses of the town. Curiously enough, it is the industry that had provided Roros with its livelihood since Hans Olsen Aasen first started mining copper in the area over 300 years ago that is the provider of much of the new income. Now one of the 70 monuments on the UNESCO World Heritage List, Roros has become a popular tourist attraction, where the smelting works including the slag heaps and the mine at Olav, which has been preserved exactly as it was the day it closed in 1972 owing to bankruptcy, and the ancient wooden houses of the workers must remain externally at any rate preserved in their original condition. Other new industries include windscreen manufacture, chair making including a novel ‘posture control’ design, a tweed mill and the Hybrid Circuit manufacturing plant of Autronica.
Editorial
Authors: Johnson Keith , Waterfield Brian
Published: February 2008

Interconnection, packaging and mounting of electronic devices tend to be too often neglected in development of the increasingly sophisticated devices of today. Whilst the electronics sector is probably the most innovative of all manufacturing industries and has an excellent record in the production of miniature devices of increasing complexity and capability, development of reliable, efficient joining techniques, essential for manufacture of marketable systems, is too often considered to be a secondary activity. Recommendations for interconnection and packaging techniques are frequently demanded towards the end of a costly development programme, at a stage when device design has been decided and when it is too late to make modifications which would facilitate these joining operations.
Parameters Affecting the Incidence of Pad Bridging in Surface Mounted Device Attachment
Authors: Roos‐Kozel B.L.
Published: February 2008

The chip carrier industry and the mounting of chip carriers with solder paste are growing rapidly. Recent papers have covered the advantages of increased board density and design flexibility. This paper addresses how percent metal, paste viscosity, paste constituents, pad dimensions and spacing, print thickness, chip carrier weight, and reflow profile correlate with the incidence of undesired pad bridging and solder balls. This information can be used in circuit design and process optimisation.
VLSI Packaging
Authors: Reiner H.
Published: February 2008

The ever greater complexity of VLSI devices is resulting in increases in pin count, power dissipation, and chip area. Furthermore, the increase in speed because of the smaller feature sizes leads to more stringent electrical requirements on the packaging. For high reliability under adverse ambient conditions, hermetic sealing is mandatory. However, for less severe requirements, plastic encapsulation is proving a cost‐effective alternative. It is expected that improvements in plastic materials and in chip surface passivation will further enhance the reliability of plastic‐packaged VLSI devices. Packaging materials and processes, as well as packaged shapes, will have to be modified to cope with the demands of future VLSI devices.
Resistor Chips for Thick Film Hybrids
Authors: Diletti H. , Hoffmann R. , Sele G. , Rees J.
Published: February 2008

Applications for thin film resistor chips in thick film hybrid circuits are discussed in relation to the different technologies involved, namely naked and encapsulated forms of mounting.
Functional Trimming
Authors: Thompson P.
Published: February 2008

With increased application of hybrids, methods have been developed enabling resistor films to be cut away until the resistor has precisely the required value for correct functioning. Passive trimming is giving way to active or functional trimming where the frequency response itself is adjusted using a sine wave generator and waveform analysis equipment. Some of the problems encountered in trimming are discussed, including those caused by the high energy laser light itself; the effect on active circuits caused by the generation of Ipp currents; and DC offset or level shifts produced by low level light. The importance of producing a system in which laser, instrumentation and computer are programmed in one language is emphasised. Finally the advantages of functional trimming are summarised.
Polymer Thick Film Circuits in Japan
Authors: Kabe A. , Morooka I.
Published: February 2008

Polymer thick film circuits have been used in consumer appliances, a trend that is growing as one of the major technologies in Japan in this field. This paper discloses the state of the art of the processes involved along with the main features of the circuits. PTF has established a performance that equals that of the cermet type in some applications, which produces cost advantages for PTF circuits on polymer and/or ceramic substrates for wider applications.
Glass‐ceramic Coated Metal Substrates
Authors: Jones R.W.
Published: February 2008

A historical review of the development of metal‐cored substrates is given, together with a detailed account of glass‐ceramic coated metal substrates as currently manufactured by Wade plc. The advantages over monolithic ceramics are discussed, and an indication is given as to future developments in this technology.
New Compositions for Hybrid Circuits
Authors: Kužel R. , Broukal J.
Published: February 2008

New resistor compositions prepared by using special kinds of glass, CdO, RuO2 and Nb2O5, have been developed. This system is typical in containing only a small amount of RuO2, ranging from 2 wt% to 8 wt%. The properties of resistors prepared from various compositions were tested in relation to peak firing temperature varying in the range from 720°C up to 800°C. In this way conditions were found for resistor preparation with low TCR and high long‐term stability at 95% relative humidity and at 40°C. By adding very small amounts (0·4–0·9%) of Nb2O5 the TCR was very drastically reduced and could achieve almost zero value. The resistance changes after 4,000 hours ranged from 0·1% to 0·8%. Further new types of dielectric compositions were prepared. The bulk insulation resistance of fired layers reached values in the range of 1012ohms/cm2; the dielectric constant (≈7) and dissipation factor (≈10−3) were also measured. This composition is well suited to applications in both oxidation and inert atmosphere.
Thermal Problems in Micro Assemblies
Authors: Lacruche B.
Published: February 2008

Except in specific activities in electronic equipment, thermal management is not the most exciting subject for those involved in design. With micro‐assembly (surface mounting of components) the cooling of components and PCB is now being seen in a new light. This paper, very rapidly, highlights the problems every designer has to take into account today. Solutions are checked and the importance of simulation, an economical and powerful tool for evaluation, is enhanced. An example of the method is mentioned, followed by a calculation. Components and basic materials manufacturers may also find some ideas as to the development of new and/or improved products.
Ruthenium Contacts Resist Chemical Attack in Communications Use
Authors: Lanam R.D. , Robertson A.R.
Published: February 2008

In general, sputtered ruthenium films attain platinum‐group properties that make them candidates for various uses in electrical, thermal and decorative areas. Advanced communications devices are one of these areas. Ruthenium could possibly be used as a diffusion barrier and adhesive layer, as a suicide former for low ohmic contacts, and as a final metallisation over platinum suicide for very large scale integration (VLSI) applications.
Wire Bonding as a Technique for Semiconductor Device Assembly
Authors: Weston A.D.
Published: February 2008

This paper is aimed at Engineers involved in production wire‐bonding processes and system maintenance. It traces the development of microbonding from its origins to the present day. Principles and techniques are examined and some approaches to fault diagnosis are explored.
The Fundamentals of Thin Film Resistive Technology for the Production of Ultra‐stable Resistors and Networks
Authors: Simon P.R.
Published: February 2008

The paper describes the physical phenomena which influence the electrical and mechanical characteristics of low temperature coefficient, high stability thin metal resistive films. Emphasis is placed on the Matthiensen and Arrhenius rules in respect of resistivity and time‐temperature stabilities. The phenomena outlined are highly dependent on the deposition methods used and film properties are discusssed in terms of the film formation kinetics, substrates, and deposition technologies. The production of thin metal film resistive films based on these principles readily achieves temperature coefficients of <5 ppm/°C over the temperature range −55°C to + 155°C with load stress stabilities of <300 ppm with full dissipation, 155°C, 2000 hours, which is as good as bulk nickel‐chromium alloy foil.
Present and Future Applications for Laser Processing of Hybrids and Semiconductors
Authors: Swenson E.J.
Published: February 2008

Present and future development of laser processing as a production technique for modifying semiconductor devices, improving yields, and decreasing development times are described. Current applications covered include thick‐ and thin‐film resistor trimming, deposited film and polysilicon resistors on silicon trimming and redundant memory repair. Emerging applications include microcircuit mask making and capacitor trimming. Examples of processes still under development include selective annealing, minority‐carrier lifetime doping, and device diagnostics by laser imaging.