bluuebunny/crossref_metadata_2025 huggingface dataset:
E‐Commerce, document delivery and academia
Authors: Morris Anne
Published: February 2008

E‐commerce is big business providing exciting opportunities for library and information professionals. This paper examines the range of options available for libraries and researchers to obtain or access documents electronically. It lists suppliers and discusses selection criteria, both informed by the results of the eLib sponsored FIDDO (Focused Investigation of Document Delivery Options) Project completed in 1999.
GENfair and Shop@ssistant: Providing access to local & family history resources
Authors: Sandford Paul
Published: February 2008

This article describes how affordable e‐commerce solutions have increased access to local and family history publications produced through special interest groups. It points the way to future provision in Local Studies libraries for secure ordering facilities for public use, and explores some of the issues surrounding such provision.
Know How; making the enquiry process work for you
Authors: Beastall Graham
Published: February 2008

How libraries and information centres go about their work is changing. At the heart of this change is both technology and new trends for managing information in the context of knowledge management. This article examines the start of the process for gathering knowledge by managing enquiries. It looks at what has been done in the past, the failures, and why emerging technologies make it possible to develop systems for strategic gain to the professional and the organisation.
Why is Knowledge Management difficult to sell?
Authors: Birks Alan
Published: February 2008

This article is a concise overview of Knowledge Management — what does the term mean, who uses KM, what are the benefits? How do we make the process work, and how does it appeal to others? It is a current topic that is important to understand and make use of.
Knowledge Management in the NHS: half‐full or half‐empty?
Authors: Booth Andrew
Published: February 2008

Healthcare is a knowledge industry evidenced by substantial resources invested in staff development and the production of research evidence. This article examines knowledge management within the NHS in terms of explicit knowledge and tacit knowledge. It concludes that whilst progress with explicit knowledge is significant management of tacit knowledge is far less developed.
NHS Knowledge Management in Bradford: the evolution of a service to meet the demands of healthcare professionals
Authors: White Kim
Published: February 2008

Knowledge management and library services are intertwined now to the extent that it is inconceivable that there could not be a partnership between them. This article looks at a specific example.
Thickness Measurement of Gold Deposits
Authors: Reid F.H.
Published: February 2008

In both decorative and industrial applications of gold plating, but even more critically in the latter, accurate measurement of coating thickness is of vital importance to both the manufacturer and the user. To the former, working to increasingly stringent specifications, it may, in extreme cases, mean the difference between profit and loss if an excessive thickness is inadvertently applied due to some change in electrolyte or processing conditions, or if an unduly high average thickness must be used on barrel or vat plated components to ensure a minimum requirement on functional areas. To the user, it can equally mean the difference between operational success and failure of a gold plated part if plating thickness is below specification and the means used for measurement are not sufficiently precise to detect this. Control of coating thickness in gold plating is therefore a matter of vital concern, and never more so than at the present time when, in the face of the spectacular price increases of recent years, and in the virtual absence of viable alternatives to meet the exacting demands of applications in printed circuitry, semiconductor technology and the electronics industry in general, the need for maximum economy in gold usage has become increasingly urgent, as evidenced by the vigorous efforts currently devoted to the development and improvement of selective plating techniques, and the recent interest manifest in the possible replacement of essentially pure gold coatings by alloy deposits of 18 carat and lower where these may be technically acceptable. The present article offers a wide‐ranging survey of methods available for thickness measurement, with particular reference to gold plating, but including also some techniques which, whilst not finding current use, may be of potential interest in this context. This is the second and final part of this article, the first having appeared in Volume 1, Number 1, October (1974).
Calculation of the Copper Dissolved by P.C. Etchants
Authors: Freeman A.
Published: February 2008

A formula is derived for the calculation of the amount of copper dissolved by a litre of new etchant for machines in which losses are made up by periodic additions of water. The only parameters necessary are the number of make‐up additions and the initial and final concentrations of copper and of a constituent that is neither decomposed nor added to during the life of the solution.
Environmental Problems in the Production and Assembly of Printed Circuits
Authors: MacLeod Ross W.
Published: February 2008

Many potentially hazardous materials and processes are employed in the manufacture of printed circuits and printed circuit assemblies. This article draws attention to these and lists the salient properties of those most commonly employed. Methods of assisting in the assurance of the safety of personnel handling and processing these materials are suggested. It is stressed that it is important always to know exactly what is being handled and how it is being modified by process operations. Finally, suggestions are made with regard to the availability of information and assistance and the need for communication with, and education of, all personnel concerned.
Measurement and Control of Coating Thickness and Porosity in Printed Wiring Manufacture
Authors: Latter T.D.T.
Published: February 2008

Most of the basic requirements for the manufacture of printed wiring are, of course, well known; so much so that literally hundreds of companies or divisions of larger companies are formed annually to produce these products. However, a high percentage of such companies fail, especially when new specifications are introduced or existing specifications are adhered to by the purchasing authority. There is a wide diversity of reasons for failure of printed wiring products to meet the requirements of quality and performance. Since some of these can be attributed to coating thickness and/or coating porosity, it is therefore the purpose of this article to outline the ways and means to control these parameters.
Technologically Based Market Research in Printed Circuits
Authors: Montgomery Jeff D.
Published: February 2008

Of all the market surveys prepared on the printed circuit industry, one of the most comprehensive is that reported in the October issue of the Journal and carried out on behalf of the Institute of Printed Circuits by Gnostic Concepts Inc. Since market surveys are currently in vogue, it was considered topical to invite a specialist company operating in this field to outline their particular approach in the preparation of such a document. In this article Mr. J. D. Montgomery, Vice‐President of Gnostic Concepts, has outlined the approach taken by his company in compiling the survey made on behalf of the Institute of Printed Circuits.
Metallising of Circuit Boards Using Mixed SnCl2 / PdCl2 Catalysts
Authors: Rantell A. , Holtzman A.
Published: February 2008

Mixed SnCl2/PdCl2 catalyst solutions are often used to catalyse the board surface prior to metallising by electroless deposition. An accelerator is also required in the catalysing sequence in order to boost the catalytic activity of the surface. Skip plating is a prime source of unreliability and can often be traced to low catalytic activity. Processing variables directly affecting catalytic activity are discussed. These include surface roughness, type of accelerator employed and its operating conditions, and the efficiency of rinsing as well as the composition of the catalyst solution. The mechanism of catalysis is also discussed, involving theories of the colloidal and complex nature of the catalyst solution.
National and International Committees for Printed Wiring
Authors: Antony Clayton P.
Published: February 2008

In this issue of the Journal we continue with our series on National and International Committees by examining the work carried out by Panel J of the Radio and Electronic Components Manufacturers Federation (RECMF). Note: Readers who are associated with, or are members of committees dealing with printed circuits or applied techniques are invited to contact the Editor with a view to preparing an article on their behalf for publication in this series. This invitation is extended to readers on a world wide basis.
Gold Plating of Printed Circuit Boards and Wire
Authors: Missel Leo
Published: February 2008

In this paper, reproduced by permission of “Metal Finishing” (New Jersey), the author enumerates the required properties of electroplated gold coatings on printed circuit boards and wire to ensure satisfactory bonding by ultrasonic means. The gold plating procedures and process control methods which are necessary to produce coatings yielding consistently high bond strengths are described.
Solders, Solderable Finishes and Reflowed Solder Coatings
Authors: Ackroyd M.L. , MacKay C.A.
Published: February 2008

In the production of printed circuit assemblies, the demand for higher reliability levels has increased over the years. In order to achieve a high level of soldering quality, it is essential that solderability is built into the system at all stages and various factors must be taken into account. In the first section of this paper some of these factors are discussed. The various solderable coalings that are available are reviewed, some of the problems that can be encountered are illustrated and the effects of impurities in solders discussed. In the second part of the paper, the use of circuit boards having fused tin/lead coatings is discussed from the solderability point of view.
Troubleshooting in the Electroless Copper Process
Authors: Stone Frank E.
Published: February 2008

In this paper, reproduced by permission of the Institute of Printed Circuits (USA), the author discusses the factors which can affect the quality and adhesion of electroless copper plating on printed circuit boards and recommends procedures to ensure optimum results.
A Review of Software Artwork Preparation and Printed Circuit Board Fabrication, Problems and Trends
Authors: Fassini M.G.
Published: February 2008

The use of computers in the printed circuit industry is discussed in relation to improving productivity and quality of work. Computers can be particularly useful in artwork production and in providing tapes for drilling machines, component inserting machines, etc.
Quality Engineering—User Experience
Authors: Smith D.
Published: February 2008

From his experience as a Quality Engineer the Author concludes that an average printed circuit board reject rate of 12% is due to inadequate process control from the photographic stage through to final handling, packing and despatch.
Some Facts and Figures on India's Printed Circuit Industry
Authors: Mitter V.
Published: February 2008

In this issue of the Journal we continue with our series of articles describing the current situation of the printed circuit industry in various countries throughout the world and as such focus our attention on India. This article has been submitted by Mr. V. Mitter of Hegde & Golay Ltd., Bangalore, India and his co‐operation is gratefully acknowledged.
The Implications of Automated Assembly
Authors: Smith R.B.
Published: February 2008

It is imperative to the successful automation of any product to establish and maintain satisfactory standards of component input.
Some Thoughts on Crossovers
Authors: Aggleton R.G.
Published: February 2008

In order to improve packing density and make fuller use of standard DIL insertion machines, a range of inexpensive multiple crossover networks in DIL packages is proposed.
Photography for Printed Circuits
Authors: Walter C.
Published: February 2008

This paper deals with the techniques and processes used in the manufacture of printed circuit boards from photographic masters. The basic theory is to produce the working photomasters, for silk screen or photo‐resist imaging, using as few steps as are compatible with the required quality and resolution. Various techniques will be discussed for artwork preparation, darkroom techniques and so on. This paper was originally presented at the First Printed Circuit World Convention held at the Cafe Royal, London in June, 1978.
Institute News
Authors: Walker J.B.
Published: February 2008

A Symposium on Circuit Technology was held at The Holiday Inn, Newcastle upon Tyne, on Thursday, 7th December, 1978.
The Resistance of Space‐Quality Solder Joints to Thermal Fatigue
Authors: Dunn B.D.
Published: February 2008

An evaluation programme involving the extensive thermal cycling of component‐assembled printed circuit boards has been undertaken to assess the suitability of ESA‐approved hand‐soldering techniques for use on long‐life satellites. The modes of joint degradation are discussed and the metallurgical changes that result from material thermal expansion mismatch and repeated strain within the solder alloy (63% tin, 37% lead) are highlighted by photomicroscopy.
Quality Assessment
Authors: Bulwith Ronald A.
Published: February 2008

With the advent of stricter tolerances and higher reliability requirements on electronic assemblies, PWB contamination has arisen as a significant contributing factor to these performance criteria.
Soldering and Fusing by Condensation Heat Transfer
Authors: Wood E.R.
Published: February 2008

When saturated vapour condenses to liquid, latent heat of vapourisation is released to the item causing the condensation, this item which is itself heated. Use is made of this natural phenomenon in order to melt solder alloys melting below 216°C in a relatively new process known both as Condensation Soldering and Vapour Phase Soldering. Solder joints of the conventional type can be produced by using condensation heating to melt strategically placed preforms or solder creams and very many joints are produced simultaneously in correctly designed equipment. Plated tin‐lead coating on printed circuit boards can also be successfully fused, in some instances without application of external fluxes. Advantages over existing heating processes include geometry independent heating, oxygen‐free environment, absolute temperature control, excellent chemical compatability, absence of residues and very high heating rates. Major benefits can include operator independence, extremely low joint cost combined with excellent joining reliability both leading to greatly reduced re‐work and consequent improvement in quality and economies. There are presently about 150 facilities operating in the USA and about ten in the UK. Many tens of millions of joints are produced each year in this way with joint costs as low as 0.03 cents and reject rates less than 0.2%
Effect of Surface Contamination of Copper, Arising from Water Rinsing on Solderability
Authors: McCarthy T.J. , Mackay C.A. , Thwaites C.J.
Published: February 2008

Rinsing treatments on copper after etching are investigated by using the adverse effect they have on solderability. The wetting time, as measured by the GEC Meniscograph, is a sensitive indicator of the effect of varying contact times with water (the most obvious way of removing etching residues). Several variables of the water were examined such as dissolved impurities (as indicated by a comparison of demineralised, boiled demineralised and tap‐water) rinsing time in tap water and water temperature. Wetting time is found to rise with all of these and demineralised water is superior to tap water, as might be expected. Very small amounts of acid added to the rinsing solution appear to retard almost completely the contamination effects of the water. All the findings underline how important surface cleanliness is to a successful soldering operation. By corollary it appears that solderability tests (especially the GEC Meniscograph) are very good indicators of extremely low levels of surface contamination.
I/C Packaging and Interconnection Developments
Authors: Sage M.G.
Published: February 2008

This paper describes the major new I/C packaging technologies now coming into use, i.e., chip carriers and tape automated bonding. It deals with the reasons for their development, where they are most likely to be used and their impact on current interconnection technologies, i.e., PCBs and thick film hybrids. The paper also looks briefly at some new developments in ‘off‐the‐chip’ interconnection, e.g., laminates and materials.
Some Practical Aspects of Flexible Circuit Design
Authors: Hogan T.P.
Published: February 2008

Flexible circuits are true components in their own rights—not solely replacements for discrete wiring—and must be designed as an efficient component for production. This paper discusses all the parameters which must be met.
Improved Laser Trimming Geometry for Thick Film Resistors—Philosophy and Example
Authors: Aggleton R.G.
Published: February 2008

Laser trimming method suitable for close tolerance film resistors is examined further and a simple analysis leading to an outline computer programme is described.
Treatment of Copper Surfaces in Printed Circuit Manufacture
Authors: Menzies G.D.M.
Published: February 2008

Copper surfaces of laminates can be damaged by abrasively brushing prior to chemical processing. This is especially important where gold plated edge connectors are made to the latest Post Office specification of 2·5 µm. Chemical rather than abrasive treatment results in a pore‐free surface which is vital when the gold is thin.
Quality Assessment
Authors: Bulwith Ronald A.
Published: February 2008

Due to the unique configuration of DIP package leads having a flat shouldered structure, extra care must be exercised in hole size design and insertion. Too large a hole diameter which results in the shoulder contacting the edge of the PTH, combined with too high an insertion force, could result in fracture of the copper plated layer at this point. Even at normal insertion forces, the localised pressure exerted at the small contact area is increased considerably and could result in failure of the plating. Creating a fissure, or discontinuity of any kind in the plated layer, leaves a path open for laminate degassing during the soldering operation. The result of the degassing is a poorly formed solder joint with voids and blowholes present, the source of which is not clearly evident to the board manufacturer unless careful metallographic work is carried out. Unless precise orientation of the samples and accurate control of polishing is carried out, the source of the problem might very easily be missed when examining the microsections.
Electron Beam Lithography at the Rutherford Laboratory
Authors: Lawes R.A.
Published: February 2008

The Science Research Council has opened a mask‐making facility at the Rutherford Laboratory based on the EBMF‐2 Electron Beam Microfabricator. Ancillary equipment designed to support the EBM resolves features down to 1 micron or below. The paper discusses the principles, design parameters and the performance of the EBM and outlines mask manufacturing procedure.
Predicting the Punchability of Laminates
Authors: Rippington G.W. , Holmes J.B.
Published: February 2008

In laminate specifications, attention is rarely paid to punching requirements. Although printed circuit manufacturers often assess the punchability of laminates in situ by trial and error, there is an increasing need for the laminate manufacturer to have access to laboratory punching tests in order to conform with quality control requirements and keep abreast of current demands on laminate properties. Several national specifications refer to existing punching tests of varying efficacity, a selection of which are discussed. The success of in‐house punching tests is analysed. The EXCELL tool has proved its value in the assessment of blanking and laddering, and two versions of a specially designed piercing tool have been devised to contend with large quantities of small holes. Laboratory investigations have been carried out into the measurement of the forces required for punching, with a variety of laminates, temperatures and punch/die clearances. Penetration/withdrawal force ratios have also been studied in detail. It now remains to research into the area of hole blocking during piercing.
New Non‐Precious Metal Catalyst for Through‐Hole Plating
Authors: Luke D.A.
Published: February 2008

Until recently the majority of catalysts used in through‐hole plating of printed circuits have been based on processes containing tin and palladium. These have been adequate although, with the ever increasing demands on quality of subsequently assembled printed circuits, they have shortcomings which are functions of the basic formulae and mechanisms of operation. The new non‐precious metal catalyst based on copper operates over a much wider range of conditions and, unlike palladium catalysts, promotes complete coverage of epoxy glass laminates. The operation of both catalyst systems is discussed in depth and compared, significant emphasis being placed on the mechanism of surface activation.
… but what are we doing to the copper?
Authors: Toms K.R.
Published: February 2008

RESCO, the Milan based PCB equipment manufacturer, has recently published the results of an investigation into the surface treatment of copper‐clad laminate. The following article is a synopsis of these investigations.
The Distribution of Power and Earth on Boards for High Speed Digital Logic
Authors: Scarlett John A.
Published: February 2008

To provide an efficient interconnection system, compromises must be made on materials and packing density within acceptable limits, and designers must understand electrical characteristics and the functioning of signal generating devices. High speed digital logic devices are analysed with special attention given to signal swings. Solutions to the problem of line reflection currents are suggested, and the decoupling process is explained. Board design is vitally important and the power and earth distribution contribute strongly towards its success or failure. Power distribution on double‐sided boards is examined, with a consideration of various arrangements of capacitors used for decoupling. After discussion of the effects of other tracks, it is evident that signal tracking lengths should be kept to a minimum, while line impedances are maximised. Guidelines for efficient tracking are provided and an explanation of the trackability factor of a PCB reveals power distribution past the ends of packages to be the most effective arrangement for achieving high packing densities. Double‐sided boards should be used where possible in preference to multilayers.
The Automatic Visual Inspection of Printed Circuit Boards
Authors: West G.A.W. , Norton‐Wayne L. , Hill W.J.
Published: February 2008

Printed circuit boards are scanned with a CCD linescan camera and a motorised table, under the control of a microcomputer. The camera signal is thresholded to produce a binary image of the track pattern, and this image is processed further in the microcomputer. The processing consists partly of comparisons against a stored master track pattern, and partly of an examination of the scanned track pattern alone to detect anomalies such as whiskers and broken tracks. The system will detect all defects so far presented to it, with an acceptable false alarm rate.
Editorial
Authors: O'Hara Brian
Published: February 2008

With Christmas over it is time for me to take a short breath and be thankful for all that I have and try to remember that I am only the custodian of these worldy goods. Each year about this time, I make my New Year resolutions, but before I do that yet again I will take a look back and see how many times I failed last year.
A New Method of Testing the Ductility of Electroplated Foil
Authors: Smith P.M.
Published: February 2008

This paper examines the behaviour of acid copper baths with regard to ductility. The necessity for a fast and consistent method of measuring ductility is emphasised and various established techniques and their drawbacks are discussed. The more recently developed procedure, the Duktilomat method, is detailed and its success analysed.
A plea from the heart
Authors: House Russell
Published: February 2008

Recently I read John Scarlett's editorial where he made a statement — ‘if our education establishment …’. My first reaction was — what establishment?
A review of U‐V curable resists
Authors: Elsberg E.
Published: February 2008

The paper reviews U‐V curable screen‐printable etch plating and solder resists, their basic components, principles of U‐V curing, their performance in the liquid as well as in the solid state and their advantages. Also discussed are the basic construction and performance of U‐V curing equipment.
Polyethersulphone—A Thermoplastic PCB Substrate
Authors: Thompson M.K.
Published: February 2008

‘Victrex’ polyethersulphone (PES) is introduced as a high temperature thermoplastic with properties attractive to the electronics industry. The polymer can be fabricated by conventional thermoplastic techniques, such as extrusion and moulding, and the parts metallised in several ways. Applications utilising these aspects are shown. Parts can be reflow or wave soldered and flux residues washed off without damaging the substrate. Some current PCB developments are discussed and a look into the future is offered as designers begin to take advantage of the thermoplastic nature of polyethersulphone.
Aspects of Manufacture, Selection and Use of Stainless Steel Woven Mesh in Fine Line, High Density, Precision Screen Printing
Authors: Chandler D.B.
Published: February 2008

Increasingly stringent quality and cost requirements have brought about a revival in the use of stainless steel cloth as a production tool for screen printing. Process factors are examined to support the choice of stainless steel for its stability and potential for high registrational accuracy printing. Screen making is of vital importance to the end result, and the achievement and maintenance of uniform tension are as critical for stainless steel as for other screen media. Full specification of printing screen requirements is essential, as is incoming goods inspection of cloth and finished screens. The entire weaving process contributes to the overall quality of stainless steel cloth and, although post‐production correction procedures are available, they are undesirable and can be avoided by a carefully controlled weaving process.
Printed Circuits—Origins and Development
Authors: Pole‐Baker M.E.
Published: February 2008

This study reviews the development of printed circuit technology from its origins before the Second World War until the present day. Various inventions appeared before the war for producing circuits on a flat surface, but it was not until Dr Paul Eisler had the idea of utilising the long established arts of the printing industry that viable methods of production were established. Stimulated by the release of an American official secret of the use of a printed circuit in a proximity fuse, and the first Technical Symposium in 1947, government and industries researched into the best ways of producing planar circuits. Dr Eisler's etched foil method emerged as the most practical technique. The first decade of the technology was spent learning and refining print and etch techniques, during which time printed circuits gradually became accepted by the consumer industry, as well as by industry and government bodies. Most of the major advances were made during the second decade, such as plated‐through hole, multilayer and additive processes. Since then manufacturing technique has been consolidated and refined, affected by the continuing demands of the electronics industry for increasing miniaturisation and packaging densities.
Plasma Desmearing of Multilayer Boards
Authors: Ongley P.E.
Published: February 2008

The paper briefly reviews the problems associated with resin smear in the manufacture of multilayer boards, the various types of material involved, and their influence on smear, and some of the techniques available for assessing the degree of smear. Following a short discussion on current methods of removing smear, the paper goes on to provide a critical comparison of traditional ‘wet’ chemical processes with the newer ‘dry’ plasma techniques. Key advantages of plasma desmearing are highlighted and the paper concludes with a more detailed description of the I V Products approach and current systems, together with results of recent development work.
Computerised Information Management for Printed Circuit Board Production
Authors: Davé M.J.
Published: February 2008

After thoroughly analysing the needs of the PCB industry through close collaboration with several PCB manufacturing companies and with an understanding of ongoing activities of IPC software guidelines, the author's company has designed a highly comprehensive Advanced Integrated Manufacturing System (AIMS) to manage the overall PCB operation with emphasis on production planning and scheduling. This computer system enables the user to achieve real‐time on‐line control of the entire PCB manufacturing operation from quotations through order entry, order edit, production planning and scheduling to shipments including invoicing, accounting, purchasing and keeping track of inventory.
Photographic Imaging of UV Liquid Photoresists—A New, Fully Automated Process
Authors: Elsberg E.
Published: February 2008

The new process was developed to offer a superior method of forming a resist pattern on a copper‐clad laminate acting as plating and etch resist. The advantages over existing methods include superior resolution, increased automation, improved reliability, and lower applied cost. The process is unique, combining the precise coating of the blank board with UV coating resist, exposing the resist through a phototool held precisely off‐contact and the development of the formed latent image with an aqueous solution. The processing is carried out using fully automated equipment without any manual handling of either laminates or phototool.
Chemical Copper Plating in the Additive Process
Authors: Ehrich H‐J
Published: February 2008

The copper plating of through holes and PCB surfaces in the additive process places high demands on the chemical copper bath and the resultant deposit. This paper illustrates the extent to which specific characteristics of the deposition and inhibition mechanism can be used to advantage.
A Review of Electroless Gold Deposition Processes
Authors: Ali H.O. , Christie I.R.A.
Published: February 2008

The literature on electroless gold deposition processes is reviewed both with respect to bath formulation and the kinetics of the electrochemical reduction and oxidation reactions involved. Some modified formulations are discussed in more detail and components processed by the use of electroless gold deposition are illustrated.
Understanding Electrical Measurements of Printed Circuit Boards
Authors: Manfield H.G.
Published: February 2008

Electrical testing of PCBs is important to ensure the maintenance of adequate insulation between tracks and from side to side of the boards; the properties of the base materials should not be degraded below an acceptable level before boards are loaded with components. The paper describes testing methods relating to resistance, voltage clearance, capacitance, inductance, insulation resistance, volume resistivity, dielectric measurements, Q factor, and DC resistance of tracks and holes.
Rheology Testing of Multilayer Prepregs
Authors: Carreman J.
Published: February 2008

To meet higher requirements on multilayer PCBs, good control of the prepreg parameters is essential. The standard prepreg tests of gel time and flow are insufficient. New test methods such as melt viscosity, scaled flow test and differential scanning calorimetry give the required information. The test methods are compared for different materials. Rheology testing using a melt viscosimeter is an important tool for both prepreg and PCB manufacturers.
Zero Defects Inc., Santa Clara, N. California
Authors: Cullen Lorna
Published: February 2008

Moving further north in California to the San Mateo Peninsula we arrive at California's premier high technology industrial zone familiarly and universally known as Silicon Valley. The area comprises a chain of communities in the Santa Clara Valley south of San Francisco, including Santa Clara, San Jose, Mountain View, Sunnyvale, Cupertino, Los Altos, Palo Alto, Menlo Park, Redwood City and San Carlos. In excess of 1,500 companies are based here, constituting about one fifth of US high‐tech industry and population has increased from 290,000 in 1950 to its present 1·3 million or more.
An Ultra‐violet (U‐V) Conformal Coating System: Materials and Processes
Authors: Goldman I.B. , Krajewski A.
Published: February 2008

The use of U‐V technology in conformal coating applications has come of age. This paper discusses the material, process, and equipment which recently have been utilised for the conformal coating of printed wiring boards. First is presented a description of the coating material properties, both uncured and in the cured state. Next follows a discussion of the processing scheme, parameters such as time, speed, and U‐V light source requirement. Hardware to enable the coating operation to fit into an automated assembly line is also described. Of special interest will be the employment of masking techniques to prevent coating of certain critical areas. Lastly, typical performance data on the actual product having the U‐V coating are presented. An overall appraisal of the entire U‐V system is included.
Multilayer Specification: Thermal Analysis Techniques?
Authors: Leckenby J.N.
Published: February 2008

During recent years, the PCB industry has become more aware of the use of analytical test techniques to aid in materials testing. Repeatable quality of base materials, together with the monitoring of the production process and the finished product, has caused supplier and fabricator to consider existing methods and to see whether modern instrument techniques can improve such tests. During meetings such as Internepcon and Productronica, the author has presented developments by DuPont which have used Thermal Analysis techniques to evaluate the materials and processes involved in the manufacture of a multilayer printed circuit board. The purpose of this paper will be to give an up to date review of the work. It will discuss the successes to date and will show where modifications to experimental methods have been made to give more practical data. Specific test methods currently used in the industry will be discussed and recommendations will be made showing Thermal Analysis techniques may offer a more objective test as well as giving the user time savings and a reduction in manpower through increased instrument productivity and versatility.
Soldermasks Reappraised
Authors: Knight W.G.
Published: February 2008

This paper examines the different types of soldermask and their suitability in terms of insulation properties and adhesion, and their processing properties, parameters and costs.
Quality Improvement by Vacuum Laminating of Complex Multilayer Boards
Authors: Müller G.
Published: February 2008

In the production of multilayer boards with 10 and more single layers it was found that air and gas, entrapped in the cured prepreg resin, caused unacceptable scrap. The amount of scrap was growing with increasing pattern density, scrap signifying each board with one air‐ or gas‐bubble ≥50µm in diameter in one of the different bonding areas. To improve the yield in this area, a laminating process under vacuum conditions was developed. The effect of the different process data on the quality will be shown. Besides the laminating process itself, the kind of vacuum seal is an important item. Laminating under vacuum conditions has led to much higher yields in the production of high density multilayer boards. The process is simple in application and the equipment expense is acceptable. Running costs for the process will be shown in detail.
Economics of Bare Printed Circuit Board Testing
Authors: Hroundas G.
Published: February 2008

The increasing complexity of today's Printed Circuit Boards inevitably leads to higher failure rates at the assembled board and product levels. Electrical testing of PCBs at the bare board level always results in early identification of failures, and thus in increased production economies. The escalating costs to identify faults at various levels of the PCB manufacturing and assembly process are discussed and illustrated. The typical PCB spectrum of faults, including contamination, shorts, opens, and holes is discussed, along with reliable methods of fault removal. In addition to the economic factors such as capital equipment cost, programming, fixturing, and operating costs, several technical factors are discussed and illustrated. These include test comprehensiveness and test speed. Since fault coverage is directly proportional to the measurement capability of the test equipment, the effects of measurement threshold on fault coverage and the resultant failure rates at the assembled board and product levels are discussed and illustrated. The importance of using the standard 100 megohm threshold is also discussed and illustrated.
Advanced Solder Masks
Authors: Sculpher M.R.
Published: February 2008

Conventional screen printed two pack solder resists have served the industry well for many years, and will continue in their present form into the foreseeable future. However, with the introduction of newer printed circuit board technologies, such as PTH boards with 4 thou tracks and gaps, and less, hot air solder levelling and the use of SMD and VLSIs require a solder mask to be applied with definitions and specifications not easily achieved. Exciting developments in resin technology have opened new horizons in UV setting and photo‐imaging which allow the advantages of screen printing to be retained with considerable improvements in efficiency and definition. Photo‐imaging also opens up new ways of coating solder mask onto printed circuit boards and these will also be discussed with their implications on future trends. The introduction of these new solder masks and novel applications will be for specific areas in the market and these will be identified and coupled with predictions for market growth into the 1990s.
The Reliability of Surface Mounted Solder Joints Under PWB Cyclic Mechanical Stresses
Authors: Brierley C.J. , McCarthy J.P.
Published: February 2008

The advent of Surface Mounting Technology (SMT) has led to concern about the long term reliability of solder joints during environmental thermal cycling, power cycling and PWB mechanical flexure. This paper describes the results of testing PWB assemblies of both through hole and SM components in a mechanical flexure jig in which the amplitude and frequency of cycling were varied. The apparent degradation of through hole solder joints (particularly to DIL devices) was often found to be worse than the SMT joints. Lower flexure cycle frequencies were much more damaging to all solder joints than higher frequencies. The results indicate that most SMT solder joints survive realistic flexure cycling very well but that poorly formed joints, which may appear visually to be acceptable, can fail prematurely. Solder joints to leadless ceramic chip carriers are the most susceptible to flexure stresses and special precautions should be taken in their application to substrates which are not entirely rigid, such as PWBs.
Wave Soldering of Surface Mount Components
Authors: Boey W.K. , Walker R.J.
Published: February 2008

In facing the upcoming surge of ‘surface mount technology’, many manufacturers of printed circuit boards have taken steps to convert some portions of their boards to this new process. However, as the availability of surface mount components is still limited, many have taken to mixing the lead‐inserted standard dual‐in‐line packages (DIPs) with the surface mounted devices (SMDs). Furthermore, to take advantage of using both sides of the board, surface‐mounted components are generally adhered to the bottom side of the board while the top side is reserved for the conventional lead‐inserted packages. If processed through a wave solder machine, the semiconductor components are now subjected to extra thermal stresses (now that the components are totally immersed into the molten solder). A discussion of the effect of wave soldering on the reliability of plastic semiconductor packages follows. This is intended to highlight the limitations which should be understood in the use of wave soldering of surface mounted components.
Screenprinting in the Printed Circuit Board Industry
Authors: Wall C.I.
Published: February 2008

Screenprinting has formed an integral part of the manufacturing process for PCBs since the first boards were produced. This paper describes the types of product used, the areas of application, and suggests methods for obtaining the best results by exploring printing parameters and indicating methods of optimising them to minimise faults.
Blowholing in PTH Solder Fillets
Authors: Lea C. , Howie F.H.
Published: February 2008

This paper introduces a series of eight describing the research work undertaken into the most pervasive of quality assurance problems in the mass soldering of plated‐through‐hole (PTH) printed circuit boards, namely the occurrence of voids and blowholes in the solder fillets. The research programme has been carried out at NPL with advice and practical involvement of members of the Soldering Science and Technology Club whose contributions have played a large part in its successful outcome. The work has led to an understanding of the mechanisms giving rise to this problem and recommendations for production procedures to fully control it. In this first paper, results are presented of a UK‐wide survey of the electronics assembly industry and of the assessment made regarding the extent, the harmfulness and the cost of the problem of voids and blowholes.
Blowholing in PTH Solder Fillets
Authors: Seah M.P. , Howie F.H. , Lea C.
Published: February 2008

This is the third paper in the series of eight, studying voids and blowholes in PTH printed circuit boards. In the previous papers the industrial significance of this problem has been established and moisture identified as the primary cause of the gassing. Now, particular attention is focused on the understanding of the mechanisms and kinetics of moisture uptake in the FR‐4 laminate. From the authors' data the rate of moisture uptake and the rate of drying of laminate can be predicted as a function of temperature and relative humidity.
Contamination Control: Quo Vadis?
Authors: Ellis B.N.
Published: February 2008

This paper essentially describes what is believed will become the norm in contamination control over the next decade, as applied to laminate and PC manufacture, components, assembly, soldering and protection. Particular attention is paid to the special requirements imposed by the increasing use of surface mount technology, especially when trying to extrapolate current techniques towards modern applications. Test methods are mentioned and these are also likely to undergo considerable development over the next few years but, above all, more precise, scientifically‐established standards are urgently needed for both ionic contamination and surface insulation resistance testing. Cleaning technology is, of course, an essential part of contamination control and future development of both solvent and aqueous methods will lie in a better understanding of the time‐energy relationship required to break contamination‐substrate bonds at a molecular level.
Recent UL Printed Wiring Changes May Affect You
Authors: Furness J.
Published: February 2008

New requirements for printed wiring base materials were announced by the Underwriters Laboratories, Inc. They will impact on the OEM, the printed wiring manufacturer, and his base material suppliers. This paper presents an overview of past and present base material requirements, followed by the rationale and specifics of the augmented criteria. Action required by the printed wiring manufacturer to comply with these new UL 796 Standard revisions is explained.
Electroplating Copper for Printed Circuit Manufacture
Authors: Luke D.A.
Published: February 2008

In through‐hole plated double‐sided and multilayer printed circuit boards, electroplated copper forms the main electrically conductive path on hole walls. To ensure high reliability of electrical connection during component assembly, soldering and subsequent service, the properties of process solutions and deposits must be controlled. This paper discusses the methods of measuring and controlling copper plating processing parameters to achieve the optimum deposit properties. Plating pre‐treatment is discussed also as this can influence significantly process performance.
In Search of the Ultimate Test Strategy
Authors: Smith P.
Published: February 2008

In an attempt to illustrate the variety of test methods available to the modern electronic manufacturer, the paper describes the major alternatives and offers a method of matching alternative strategies to the particular test problems being faced. Test efficiency is described as a means of comparing alternative test strategies and choosing that which ‘fits best’. One form of test, In‐Circuit test, is examined in more detail and guidelines for improving test coverage are described.
Wave Soldering: The Efficiency of Debridging with a Hot‐air Knife
Authors: Verguld M.M.F.
Published: February 2008

This paper describes the results of experiments to remove short circuits after wave soldering Surface Mounted Devices (SMDs), using an air‐knife debridging system. The air knife can improve the results of wave soldering by removing short circuits which otherwise cannot be removed by adjusting the solder waves; however, the knife must be properly adjusted. Furthermore, it appears that the most serious problem found by using the air knife is the formation of solder balls. The number of these can be reduced if a suitable agent is added to the second wave of the soldering machine, which makes the air knife more or less superfluous.
DENSTRATE® Technology
Authors: Schmidt W.
Published: February 2008

With SMD‐Technology, the first purpose of plated‐through holes—to fix the components to the board—is no longer relevant. The utilisation of blind vias, preferably in combination with buried vias, results in an extremely high interconnection and packaging density and in most cases in fewer signal layers. Technology problems like drilling with precisely controlled Z‐axis as well as through‐plating of blind vias have been overcome. Reliability tests have shown a substantially lower failure rate in thermal cycling tests for DENSTRATE® multilayers.
The Necessity for Machine Intelligence in Automatic Optical Inspection
Authors: Icough M.
Published: February 2008

Despite the influx of companies and systems offering automatic inspection for the PCB industry, its acceptance rate in Europe has been slow. The problem seems to be lack of machine intelligence and inflexibility—factors that European companies cannot tolerate due to the nature of the market and the product mix. A new optical inspection system based on the ‘comparison’ method offers the required flexibility, but has needed a great deal of research into mechanics, electronics and software to overcome inherent problems. As this programme nears completion, a new generation of automatic optical inspection and statistical control systems will be possible.