bluuebunny/crossref_metadata_2025 huggingface dataset:
Base, Substrate Materials for the Construction of Electronic Assemblies; Special Application of Surface Mount Technology Printed Circuit Boards
Authors: Angstenberger A.
Published: February 2008

The general section of the paper discusses in detail the demands of SMD‐Technology on Printed Circuit Boards, namely dimensional, thermal, electrical and chemical requirements on both substrates and finished PCBs, besides characteristic features of the production process and the overall performance of the assembly. The second part is concerned with a survey of materials and methods suitable for the needs of SMT printed circuitry. Emphasis is laid on appropriate substrates, thermal management of assemblies and PCBs for high speed/high frequency applications
Electrostatic Coating of Photoresists
Authors: Hultzsch G.
Published: February 2008

Electrostatic spray coating with liquid photoresists is described. The process takes place in a horizontal coating station especially developed for the printed circuit board. Thin layers as etching as well as thicker layers as solder mask can be applied onto rigid or flexible base materials and metallised glasses or ceramics. The holes are not coated during electrostatic spray coating. In contrast to a curtain or roller coater no reserve pumping or filtration of the primer is necessary. By using a paper conveyor belt the time taken for cleaning is very low when stopping the machine or changing the primer.
The Slow Return to Viability
Authors: Tyler Roger L.
Published: February 2008

In my previous article ‘At the Bottom of the Trough’ which was published in this journal in January, I suggested that a general upturn would be delayed until the late Spring/early Summer of 1986. At the time of writing this report in early June, the signs are that the return to viability has started in the UK. Companies both large and small are indicating improved order books and a general sense of optimism is beginning to return. It will be some time before this order flow becomes converted into actual production (with average lead times of about 6–8 weeks in the industry, the accelerated order flow will be some 1–2 months in coming through). At the same time, if increased orders means the hiring of extra people, then further delays may take place before the bottle‐necks are cleared and the product starts to be shipped.
Contraves AG, Zürich
Authors: Cullen Lorna
Published: February 2008

With Contraves AG celebrating the fiftieth anniversary of its foundation, 1986 seemed an appropriate year in which to visit its Zürich headquarters and multilayer production facility situated in Schaffhauserstrasse in a quiet suburb approximately five minutes' drive from Zürich International Airport. The advantages of this strategic location, convenient for intercontinental communication and an ideal focal point for business within mainland Europe, can hardly have been fully appreciated when in 1936 the small company was set up in a rural environment for technological and scientific research related to air defence. From its modest beginnings with four employees, that R&D company of Contraves (Latin: contra aves= against birds) has attained a widely respected reputation and currently employs some 5300 personnel worldwide, 2300 of whom are based in Zürich.
MANIA Elektronik Automatisation Entwicklung Gerätebau GmbH, Schmitten, W. Germany
Authors: Cullen Lorna
Published: February 2008

It has to be admitted that sometimes weekend travel has its compensations. Whereas previous sojourns in Frankfurt had meant busy days confined indoors in the city itself, with little opportunity to satisfy the writer's rarely indulged thirst for fresh air and exercise, a free Sunday based in the heart of the Naturpark Hochtaunus just thirty minutes drive from Frankfurt became an unforgettable experience. Schmitten (Niederreifenberg), nestling in a valley surrounded by forest‐clad hills, is the village location of the headquarters of MANIA, and the day before Circuit World's visit to the company in May offered the rare chance to enjoy the Taunus hills in their Spring glory. The fresh pale green of the new foliage on the beech trees presented Nature's artistic contrast with the backcloth of dark coniferous forest, and it was refreshing and exciting to explore the abundance of well marked Wanderwege, many serving in Winter as Langlaufloipen. It was remarkably peaceful, and possible to wander for hours without seeing anyone—alone among regiments of stately pines and clusters of fragile wood anemones, crunching underfoot the remains of last Autumn's beech leaves, invigorated by the clear air and smell of pine resin, and with only birdsong for company (and isn't it a crazy world—German birds ‘speak’ exactly the same language as their British counterparts!).
The Imaging of Fine Lines‐Conventional Technology or Laser Direct Imaging?
Authors: Britton P.
Published: February 2008

The continuing trend towards miniaturisation is constantly driving the printed circuit manufacturer to seek new or improved methods of imaging the circuit pattern onto base laminates. Significant advances have recently been made in conventional dry film technology to meet the needs for fine‐line applications. However, a new technology—Laser Direct Imaging of the dry film—is also emerging as a viable alternative. This paper will examine the state‐of‐the‐art of both conventional dry film technology and laser direct imaging of a photoresist for production of the next generation of high density printed circuit boards.
The Solderability Testing of Surface Mount Devices Using the GEC Meniscograph Solderability Tester
Authors: Gunter I.A.
Published: February 2008

This paper outlines some techniques developed at GEC Research Laboratories to extend the range of specimen types which may be solderability tested by the wetting balance method. Particular emphasis is placed upon surface mounting components and substrates, which have not proved amenable to quantitative testing by conventional means.
Dynamic Mechanical Testing of Solder and Solder Joints
Authors: Lauer L.D.
Published: February 2008

Successful use of solder joints to attach surface mounted devices to printed wiring board substrates requires knowledge of the stress‐strain properties of solder as functions of temperature, time, and loading conditions. In addition, the relatively high operating temperature of solder in comparison to its absolute melting temperature introduces a requirement for an understanding of the influence of creep effects on the mechanical properties of solder under cyclical loading conditions. In the past, studies of these solder properties have been limited by the need to use relatively large bulk solder samples that may or may not be representative of actual solder joints in a printed wiring board‐chip carrier environment. A previously unreported test method for the evaluation of the dynamic mechanical properties of solder and solder joints has been developed. The method is based upon the use of a Rheometrics Dynamic Spectrometer, which has been shown to be capable of determining both the elastic and plastic responses of solder joints during cyclical loading under a variety of imposed strains, strain rates, and temperatures that are within the range of anticipated service conditions. In addition, stress relaxation properties of solder joints may be studied.
Blowholing in PTH Solder Fillets
Authors: Lea C. , Seah M.P. , Howie F.H.
Published: February 2008

The importance of the quality of the plated‐through‐hole copper barrel in double‐sided and multilayer PCBs is considered with regard to the problem of voids and blowholes in the solder fillet. The thickness of the copper, and its integrity and adherence to the drilled surface define its ability to withstand the pressure burst of gas from the outgassing laminate during the few seconds of the thermal spike induced by the molten solder prior to solidification. The ability of copper electroplate to bridge over areas devoid of electroless copper and produce a barrel free of pinholes is shown to be crucial to this problem. In addition, the use of a nickel layer is shown to enhance greatly the impermeability of the barrel to the evolving gases.
Blowholing in PTH Solder Fillets
Authors: Lea C. , Howie F.H.
Published: February 2008

Data from laboratory and production scale tests are given that show that the efficiency of catalyst adsorption controls the coverage by the electroless copper deposit in plated‐through‐holes in FR‐4 laminate, and that this, in turn, governs the outgassing performance of the finished board. The nature of electroless copper nucleation and growth is discussed and the reasons for the formation of voids in the deposit are identified.
New High‐resolution Dry Film Photoresist
Authors: Tilsley G.M. , Roos L.
Published: February 2008

A new family of high resolution laminar dry films has been developed for making the next generation of high density printed circuit boards. Resolution below 50 micron lines and spaces can be obtained on a production basis with these high resolution films using a mild surface preparation and a collimated light source. Using specialised equipment and processes, patterns have been etched and plated which have resolved 18‐micron (075 mil) lines and spaces. Exposure and development latitudes, although tighter than for normal dry films, are still sufficient for standard shop operations.
Genuine Etchback Using Permanganate Systems
Authors: Wynschenk J. , Delgobbo A.
Published: February 2008

Permanganate desmear technology has been widely accepted in the US as a quality and cost improvement over the traditional desmear methods. Based on two years intensive research and development efforts the paper describes a technological breakthrough resulting in a new application of permanganate technology: genuine etchback without the use of chrome, sulphuric or plasma.
The Rôle of the Stencil in High Definition Screen Printing
Authors: Partridge S.A.
Published: February 2008

This paper is intended to be of interest to those involved in electronic applications of the screen printing process, including PCBs, membrane switches, thick film printing and instrument control panels. In recent years there have been a number of advances in screen printing technology which have significantly increased the capabilities and versatility of the process. Developments have included improvements in performance of screen printing machinery, mesh fabrics, stretching equipment, screen frame design, exposure devices, stencil systems and ink rheology and printability. In spite of these advances, there are many applications in PCB production where screen printing is under‐utilised, despite its cost effectiveness for volume board production when compared with dry film resists. This paper outlines some of the developments which have produced the modern screen stencils, and describes the rôle of mesh and stencil in determining the properties of the final printed result.
Selecting the Accept/Reject Criteria for an Automated Solder Process Inspection Machine
Authors: Schoenbaum G.L. , Socha E.
Published: February 2008

The selection of the accept/reject criteria for any automated inspection machine depends first on what is deemed an acceptable quality level for the particular company/organisation doing the soldering. Although there are many specifications and guidelines, the criteria become those which were previously acceptable. As a result, a method has been developed for the Solder Process Inspector, SPI‐2000, to adjust the variable threshold settings based upon that particular solder line's previously acceptable performance. Once this has been accomplished and the automated machine is performing the function for which it was purchased, additional process data can be analysed and improvements considered. Utilising this method puts the machine to work in the existing environment rather than forcing undesired changes to the process, resulting from the new acquisition.
Quality Control of Surfaces for High‐reliability Electronics
Authors: Ellis B.N.
Published: February 2008

This paper discusses the requirements of quality assurance of electronics assemblies with respect to the surface conditions, and more particularly the problems introduced by modern assembly techniques. Ionic contamination testing and surface insulation resistance measurement are dealt with as complementary techniques. Particular emphasis is laid on the fact that standards related to both QC methods are inadequate and do not reflect modern needs. Cleaning, as a corollary to contamination, is touched upon without detail, other than a table comparing methods as a function of purchasing and operating costs, technical performance, etc.
SMA Technology—Current Practices and Criteria for Testability
Authors: Nicholas P.
Published: February 2008

Automatic in‐circuit testing is a cost effective facility for not only testing assembled printed circuit boards but for providing component level diagnostics very quickly with an average PCB test time of less than 30 seconds. The in‐circuit tester relies on a customised fixture (essentially a bed‐of‐nails) to interface particular PCBs to the system and a computer programme to control the hardware to test all the individual components on the PCB to their own specification irrespective of how the circuitry is configured. So if all the individual components work and are interconnected correctly, the complete assembly should function correctly. Traditionally the fixture requirements for most PCBs have been straightforward. In general, components are mounted on only one side of the board allowing easy access to the other side where all the tracks may be accessed by a bed of nails. However, the introduction of surface mount technology introduces mechanical restraints on this concept. Components can be mounted on both sides of the PCB, possibly causing an access problem. Not all circuit interconnections may be available on a single side of the PCB, necessitating dual side fixturing. The pitch of components together with pad and track sizes has dramatically reduced, possibly requiring the use of smaller test probes and certain SMDs do not allow direct probing at all. All these things can present problems but they do not mean that in‐circuit testing is no longer the solution to the test and repair problem. On the contrary, it is particularly well suited to the production problems being experienced by manufacturers. And where components are difficult to remove and replace on a PCB, it is particularly important that the fault diagnosis is to component level. This paper describes the problem in detail and goes on to demonstrate that if a code of practice is followed within the design of a new PCB, then there need not be a problem. Much can be achieved very simply within the design that can improve the testability of PCBs so that in‐circuit testing remains a very cost effective system. Experience demonstrates that most designs could be fixtured with traditional techniques and that means cheap and reliable fixturing.
Thermal Monitoring of Drill Bits During Laminate Drilling
Authors: Traub A.C. , Evans J.
Published: February 2008

Infra‐red thermal monitoring of drill bit temperatures is just coming into use for laminate drilling. Although not yet in production use, the method has been evaluated, with promising results, in the engineering laboratories of four major manufacturers. In addition, it has been used with excellent results as a research tool during studies of interactions between drill wear, drill temperature, compositions of entry and backup materials, hole quality, and other parameters of the drilling process. This paper will outline the principles of infra‐red thermometry and will then discuss the present and the anticipated applications to laminate drilling.
Pressing Flex and Rigid‐flex in a Vacuum Press
Authors: Hinton P.E.
Published: February 2008

The vacuum press when used for lamination of flex and rigid‐flex printed wiring boards produces boards which exhibit better dimensional stability and better fill characteristics at lower pressures than when a conventional hydraulic platen press is used. This paper presents how lamination with a vacuum press differs from lamination with a hydraulic press and what results can be achieved with this new type of equipment technology.
Optical Inspection of Printed Circuits: Requirements Placed on AOI in the Manufacturing Process
Authors: Angstenberger A.
Published: February 2008

Both the need for the introduction of automated optical inspection (AOI) systems in the PCB manufacturing process and the requirements, technically and on economic grounds, placed on such equipment are discussed in detail. Furthermore, emphasis is placed on the description of commonly used AOI concepts. The paper ends with a check list containing the most important questions concerning any system's capabilities.
Blowholing in PTH Solder Fillets
Authors: Lea C. , Howie F.H. , Seah M.P.
Published: February 2008

The amount of gas blowing into the molten solder in plated‐through‐holes during wave soldering is dependent upon the moisture content of the board and the strength of the copper barrels to withstand the pressure of gas. This strength is dependent, in turn, upon both the thickness of the copper electroplate and the quality of the original electroless copper deposit. The problem of blowholing may be overcome by improving the copper quality and/or by baking the PCB prior to soldering. This paper gives a scientific framework linking the important parameters involved in the control of blowholing. Full data are given to enable the allowable moisture content of a PCB to be calculated in respect of the pressure generated during soldering and of the strength of the copper barrels. If baking is required to attain the required low moisture levels, then certain data are required to quantify the effects of the storage times and the environment conditions between that bake and the subsequent soldering. These data are given.
Advances in MLB Technology
Authors: Deckert C.A.
Published: February 2008

During the past several years, technical requirements of the printed circuit board industry have increased greatly, due to the need for greater processing latitude, higher density devices and higher reliability in the finished parts. This need has resulted, in many cases, in the emergence and/or recognition of numerous problem areas which have created greater demands on the desmear and PTH processes, specifically. Problems such as hole‐wall pullaway, resin recession, blistering, gross voiding, and blow holes have grown in importance and severity as a result of today's needs. The development of a reliable and practical permanganate desmear process has proven to solve numerous of these technical problems. The characteristics, operation, and advantages of this three‐step permanganate process will be discussed in some detail, with particular emphasis on demonstrated improvement in PCB production results.
Effect of Process Parameters on the Insulation Resistance of Conformal Coating for PCBs
Authors: Calahorra A. , Sali S. , Drori L. , Kenig S.
Published: February 2008

The insulation resistance of polyurethane and poly (para dichloroxylelene) conformal coating was characterised following exposure to hygrothermal environment. Three types of test specimens were used—the standard Y type pattern, the ‘comb’ pattern and the ‘twin’ conductor type. The PCB with the comb pattern has been found to be the best testing specimen for the evaluation and comparison of conformal coating materials and processes. Using this type of PCB, the effects of predrying and thickness in polyurethane coated PCBs have been studied. While predrying has proved to be beneficial for preventing degradation of insulation resistance upon exposure to hygrothermal conditions, only marginal improvement of resistance is obtained when the polyurethane coating thickness has been doubled from 50 to 100 µm. Tin‐plated copper exhibited enhanced insulation resistance compared with bare copper for both polyurethane and polyxylelene coatings. Finally, a thin polyxylelene coating has demonstrated improved moisture barrier properties compared with a thicker polyurethane coating as determined from the resistance degradation with exposure duration to heat and humidity.
Flexible Interconnections—Materials and Design
Authors: Shepler T.H.
Published: February 2008

Flexible circuitry and flexible interconnects are high technology products that require a good understanding of flexible laminates and their properties to ensure the proper design of a functional part. Many designers use flexible interconnects for packaging and multiplane interconnections, but incorrectly compare flexible materials to rigid laminates. Flexible materials and design considerations when using flexible materials are reviewed, with a brief overview of the combination of flex and rigid materials in a flex/rigid multilayer circuit.
The Impact of Moulded Thermoplastic PWBs: An Emerging Technology
Authors: Germany R.
Published: February 2008

The printed circuit industry is on the verge of witnessing a change in structure, brought about by the advent of Moulded Thermoplastic PCBs and accompanying electroless plating technology. Currently all fabricators use essentially similar technology and pressed laminates, except a few innovative companies who are exploring the new technology for moulded thermoplastic printed circuit boards. The new moulded PCBs (MPCBs) have many claimed advantages over traditional boards, such as: lower production costs through faster moulding fabrication; more precise drilled holes and board dimensions; custom designed hole shape and board shape; integral moulding of board and device enclosure; higher thermal stability and dimensional stability; better dielectric properties for reduced cross‐talk; and adaptable integration of circuit design and components. Certainly the industry will not change overnight, but, as changes take place, the traditional materials will be replaced by new polymers, chemicals and equipment, as MPCBs are introduced into relevant fields of application. Some firms believe that MPCBs are only a small specialised market, while others feel that they will eventually replace many of the traditional PCB constructions of today. Chem Systems has analysed these views and prepared a study which will help to discover the real impact of MPCBs on designers, fabricators and suppliers on a worldwide basis.
Multilayer Rigid‐flex Printed Wiring Design Considerations
Authors: Nicewarner E.
Published: February 2008

Rigid‐flex printed wiring constructed in different multilayer configurations and with varying features is discussed. Materials used in rigid‐flex construction have widely varying properties which cause processing difficulties and thermal stress related problems which can be minimised by proper construction features. Examples of failure mechanisms due to improper construction or material usage are given. Design considerations which will avoid construction related defects are summarised.
Three‐dimensional Circuitisation of Plastic Mouldings
Authors: Stevens B.J.
Published: February 2008

This paper briefly discusses various solutions to 3‐D PCBs by giving an overview of available technologies. Specific attention is then directed to the author's company's technique. Coverage of aspects such as: Potential Market Size and Relationship to Existing Technologies, Functional Specification, Test Results, and Low Tool Costs is given.
Phototools for Printed Circuit Board Production
Authors: Junginger H. , Werner W.
Published: February 2008

Photographic films and glass plates are widely used as phototools for PCB production. In this two‐part paper photographic and physical characteristics of the products are discussed as well as their differences and specific features. Terms such as contrast, density, speed, processing, etc. are explained and dimensional stability is discussed in depth. Suggestions are made for proper handling of the photographic materials.
Application of Electrochemical Principles to Acid Copper Plating
Authors: Birdsall P.W.
Published: February 2008

Plating productivity is often limited by the deposition rate of the electrolytic copper system. Using electrochemical engineering principles, a high speed copper process has been developed which addresses this need. This paper describes the new high speed system and illustrates how the same electrochemical fundamentals can be applied to high aspect ratio‐high throw requirements.
Internepcon/Semiconductor Korea 1987
Authors: Muir Christine
Published: February 2008

‘Made in Korea’, ‘mass production’, ‘cheap labour’ and ‘Where exactly is Korea?’ are some of the typical comments made regarding the country often called ‘The Land of the Morning Calm’—the Republic of South Korea.
PC Based CAD for the Electronics Designer
Authors: Battell R.D. , Wallace J.C.
Published: February 2008

This paper is more than just a guide to the points to look for when contemplating the purchase of a CAD system for electronics to run on personal computers. It offers many helpful hints and points out the main pitfalls to avoid falling into. The limitations of the simplest systems are explained, as are the advantages offered by the more complex ones. It is pointed out that some modern PC‐based softwares on the latest machines running on 80386 processors can out‐perform mini‐computer systems costing several times more. In particular, this paper explains many of the difficulties that may be encountered when using such softwares for SMT designs, including those using both conventional and SM devices. It is based on many years' experience in designing and selling such software, so that the potential user can judge better the philosophies behind the software concepts. It is therefore the opposite viewpoint to the more common article on the experience of a user having purchased a particular type of software.
Critical Aspects of Multilayer Manufacture
Authors: Bayes M. , Chiba K. , Kurokawa Y.
Published: February 2008

The key to the production of high quality multilayer PWBs lies in a clear understanding of the many interactions between the chemical and mechanical processing involved. This describes some of these interactions, namely those between oxide treatment, lamination and drilling and the subsequent chemical processing steps, up to, and including, copper electroplating. Choice of oxide treatment has consequences that are not limited to the lamination and drilling operations. Process problems, such as ‘pink ring (haloing)’ are discussed in the context of their sensitivity to particular stages in the manufacturing process.
Contamination Problems within SMT
Authors: Ellis B.N.
Published: February 2008

This paper is intended as a guide towards increasing the reliability of electronics assemblies, particularly SMAs, by going through the stages of production and examining the contamination sources. A particular accent has been put on the local situation in Central Europe, where the materials and techniques used are somewhat different from those in certain other parts of the world. Some of the particular points mentioned are: problems arising prior to soldering, as well as from soldering and subsequent flux removal; solder balling; contamination control and the ‘Green Factor’—environmental problems caused by cleaning processes and products. Obviously, in a short paper, it is not possible to give an in‐depth treatment, so it must be considered more as a summary with references given for those desiring further information.
Evolution of Glass Finish Technology in the Past Decade
Authors: Vaughan D.J. , Tsujioka N.
Published: February 2008

Over the past ten years, there has been continuing development of coupling agent technology and the utilisation of these materials in treating reinforcing fibres in composite manufacture. This paper reviews these developments and examines both the chemistry and the methods used in analysing the surfaces and interfaces of glass reinforced laminates, with special emphasis on how these areas affect the performance of printed circuit boards.
The Impact of Microwave Theory on MLBs for High‐speed Digital Applications‐Design, Production, Qualification
Authors: Angstenberger A.L.M.
Published: February 2008

Multilayer boards for high‐speed digital applications are no longer solely substrates for the electrical interconnections needed but play an active role regarding the overall performance of electronic assemblies. In the general part of this paper all the important parameters regarding achievable impedances and their tolerances are discussed in detail. The second part is concerned with the practical realisation of Microwave Theory on a selected example of a high‐speed MLB.
Printed Circuit World Convention IV June 2–5, 1987 TOKYO JAPAN
Authors: Cullen Lorna
Published: February 2008

In this second part of the report on Printed Circuit World Convention IV held at the Tokyo Prince Hotel, Tokyo, from 3–5 June 1987, a general synopsis of the content of the papers presented in the eighteen technical sessions will be given. As three sessions were run in parallel throughout the 2½‐day conference, and therefore not all presentations were heard by those reporting on the technical programme, a number of them have been briefly summarised from the Convention Proceedings.
Print Service BV, Echt, Holland
Authors: Cullen Lorna
Published: February 2008

A gloriously sunny August day set the natural beauty of the Limburg countryside off to perfection during Circuit World's brief journey through this area to visit Print Service BV in the small town of Echt near Roermond. Tree‐lined roads, fertile farming land, fields of maize and the remnants of the season's asparagus crop characterised the landscape on the short drive from the German border after arrival at Dusseldorf airport. Until fairly recently a coal‐mining area, this southernmost strip of Holland extending down to the rolling Ardennes was part of the Roman Empire for four centuries and retains traces of this heritage with a wealth of cultural monuments. Continuing the heritage, over 300 artists have settled here in recent years, creating an intriguing variety of work. Farming and light industry provide the main present‐day occupations in this province in which Echt, centrally situated, is the location of Holland's largest printed circuit board manufacturing company.
Shipley Europe Ltd, Coventry, England
Authors: Cullen Lorna
Published: February 2008

Celebrating in 1987 thirty years of activity, predominantly in the field of electroless chemicals for the printed circuit industry, the Shipley organisation worldwide can justifiably claim to have fulfilled and to continue to fulfil the original company slogan cited above.
Industry news
Authors: Muir Christine
Published: February 2008

M & T Chemicals have announced the appointment of Mr David Smith as Director of PCB Systems and as a member of the company's Board of Management. Mr Smith, who was formerly Sales and Marketing Director of Lea Ronal (UK) Ltd, has had more than seventeen years experience in the printed circuit industry.
Advanced Discrete Wiring Technology: A Solution for High Density Sub‐nanosecond Interconnection
Authors: Buck T.J.
Published: February 2008

Advanced discrete wiring systems are being developed to produce state‐of‐the‐art circuit boards for packaging the next generation electronic systems. The demands placed on electronic interconnection by very high speed VLSI devices have created a need for large circuit boards that will support high interconnection density. At the same time these circuit boards must maintain the necessary transmission line parameters to transport signals with sub‐nanosecond rise times and retain signal fidelity.
Repair of Printed Circuit Boards Carrying Surface Mount Components
Authors: Verguld M.M.F. , Leenaerts M.H.W.
Published: February 2008

Removal and replacement instructions for surface mounted components are given, as well as certain precautionary measures and examples. Some of the figures have already been published in service manuals. A distinction is made between methods for replacing one or a few components, several components and many components. It is indicated which method can be applied, which equipment is available and what must be considered.
Low Voltage Insulation Resistance Measurement of Printed Circuits and its Implications
Authors: Ellis B.N.
Published: February 2008

The use of surface insulation resistance testing has been restricted to QC laboratory applications. The extension of this technique to modern electronics and, in particular, to contamination control of SMAs has forced the development of new methods of SIR measurement. These have revealed that existing standards are rapidly becoming obsolete because the premises on which they are founded are no longer valid. Even more alarming, it is revealed that we are rapidly reaching, not only the limit of our knowledge in the field, but also the technical limits of existing standard materials used in industry today. This paper is a warning against too much complacency, as the risk of running into real problems, at all process stages, will become very pertinent within a few years. The technical content of this paper is based on about three years' study of the subject resulting in the measurement of SIR at about 10 V, as opposed to the traditional values of 100 and 500 V, which have been proved to be of little value with conductor spacings such as are usual on SMAs.
Automated Edge Connector Plating Equipment for Printed Circuit Boards
Authors: Hemsley J.D.C.
Published: February 2008

This paper describes the development of a new generation automated edge connector plating system specifically concerned with the even distribution of precious metal on the connector surfaces. Other aspects include the minimisation of process chemical contamination through the development of special interstage sealing methodology, and the introduction of high speed process chemical technology.
T300 Graphite Core Printed Wiring Board: Predicting the Coefficient of Thermal Expansion
Authors: Williams R.L. , Hauch R.J. , Noblett A.W.
Published: February 2008

Materials with low thermal expansion rates are being used in printed wiring boards (PWBs) to obtain a thermal expansion factor compatible with that of surface mounted leadless ceramic chip carriers (LCCCs), thus improving solder joint survivability and reliability. Boeing Electronics Company (BECo) selected T300 graphite, a constraining core material, as its baseline in establishing methodology for predicting and then measuring coefficient of thermal expansion (CTE). Predicted results from the Interactive Composite Analysis Program (INCAP) were compared with CTE measurements derived from a relatively new strain gauge technique.
New Process Technology for High Tolerance Circuit Boards
Authors: Kreisel R.
Published: February 2008

The design of PCBs is highly influenced by the components being mounted on them. Holes with diameters as small as, for example, 0·008 in. and aspect ratios of 10:1 will become standard. More complicated PCBs of higher value need enhanced security and uniformity in processing. An answer to these requirements is provided by UNIPLATE, a horizontal processor developed by Schering Electroplating. To secure hole wall treatment, this system uses floodbars for forcing the solution through the holes. Together with chemicals, tuned to this very application, very high quality PCBs can be accomplished.
Bepi Matrix Systems Hosts Successful Multiwire Conference
Authors: Cullen Lorna
Published: February 2008

Bepi Matrix Systems, Galashiels, Scotland, organised a Multiwire Conference held on 28th and 29th September 1987 which aimed to bring together current and potential Multiwire users to hear a number of presentations by speakers from the US, Japan and the UK. The papers given focused on Multiwire's technical advantages and the latest manufacturing techniques used with this discrete wiring technology.
Substrates for the New Generation of SMT
Authors: Kingsley D.S.
Published: February 2008

For military applications the use of LCCCs is generally accepted and welcomed because of their availability, reliability and relative ease of assembly. Moreover, the problems of TCE mismatch, substrate flatness and thermal management have been overcome by the use of copper‐clad Invar as a substrate material. The cost and availability of such substrates lead to a continuing search for more suitable materials or refinements in the present‐day manufacturing processes. The emergence of the new epoxy based laminates such as BT and High Temperature is encouraging designers to move away from the more expensive‐to‐make polyimide materials. However, polyimide has superior physical properties that make it more suited to SMT and should not be discarded without fully understanding the penalties that may occur with alternative polymers. The further development of VHSIC and gallium arsenide integrated circuits means that future substrates will not only have to provide solutions to present problems but will also need to accommodate the increase in signal speeds, control of impedance and other properties. Thus substrate design will see a move towards finer line widths, low‐loss dielectric material, stripline construction and special copper foils.
Electrophoretic Photoresist Technology: An Image of the Future—Today
Authors: Vidusek D.A.
Published: February 2008

Line widths are rapidly shrinking and the complexities of boards place increased demands on the resolution capabilities of the photoresists. A new technology is emerging that offers the user unparalleled resolution, a completely aqueous system, and complete, uniform, three‐dimensional coverage of the panel. The unique properties of this system result from the extraordinary method of application of the photoresist. Electrophoresis, or electrocoating, allows the deposition of a very thin, uniform, highly chemically resistant photoresist layer. Any exposed conductive surface, including scratches or other panel imperfections, are coated. The combination of a very thin layer and no cover sheet allows the printing of sub‐mil geometries without the need for a collimated light source. This new application offers the user high yields, both from the chemistry and in circuit yields. Even more so, the resolution capabilities offer opportunities beyond the limitations of dry film and other liquid resists. The photoresist no longer needs to be the gating factor in process capability.
Low Solids Content Fluxes
Authors: Toubin A.
Published: February 2008

The arrival of low solids content flux on the electronics production market represents something of a revolution. Traditionally, the electronics industry has used, and is still using, successfully rosin fluxes containing between 15% and 35% solids content, for wave soldering electronics assemblies (PTH and single‐sided PCBs). It is therefore surprising to find that today fluxes containing between 2% and 10% rosin can be both efficient and cost‐effective.
Electro‐static Controls
Authors: Wells L.C.
Published: February 2008

The packaging of static sensitive devices is just one aspect of the control process. It should never be considered in isolation, otherwise it will be just another item of expenditure that does nothing to solve the overall problem. Efficient and effective static protection involves a chain of precautions and the strength of the chain is determined by its weakest link. The best packaging in the world will not prevent static damage if just one of the other controls is inadequate.
Pulse Plating of Electrolytic Copper
Authors: Montgomery A.
Published: February 2008

The paper outlines the application of a unique Pulsed Current technique to the Acid Copper Electrolyte used in the PCB industry. It discusses some of the inherent difficulties associated with conventional DC plating and how these pulsing techniques can overcome them to enable the production of a higher quality product despite the ever increasing demands being placed on manufacturers for better distribution and through‐hole plating.
Down the Slippery Slope Again
Authors: Tyler Roger L.
Published: February 2008

The Electronica Show in Munich has ended and the Pronic Exhibition in Paris is now a thing of the past. As I write this article we are on the run‐up to Christmas and the days are getting shorter and colder. A year ago I went to press with an article called ‘Towards a Busier 1988’ and it seems that many of the predictions made in that article have come to pass. Across the world of printed circuits (I hesitate to say ‘circuit world’ for obvious reasons) the industry has seen healthy growth in most of the major world economies. The United States has enjoyed some significant increases in activity with both the board shops and the laminators working hard to keep up with the predicted increases in demand which came through in the earlier months of the year.
PRONIC 88
Authors: Cullen Lorna
Published: February 2008

For those arriving in Paris the weekend before Pronic, what could almost be described as a holiday atmosphere prevailed. The visit by the Prince and Princess of Wales had left its mark in the proliferation of front‐page features of ‘Lady Di’ displayed on news stands. The Champs Elysées looked elegant and resplendent with a profusion of French tricolours marking the royal visit combined with commemoration of Armistice Day. Autumn sunshine—and green leaves still on the trees—brought throngs of Parisians onto the streets. At present the Arc de Triomphe is closed to the public for cleaning and restoration, but on 11 November there was the unique opportunity, taken by lengthy queues of people, to visit the Tomb of the Unknown Warrior and view the floral wreaths laid there during the commemorative ceremony.
PCIF News
Authors: Cullen Lorna
Published: February 2008

Always having heard that PCA Conferences are a blend of interesting technical and marketing presentations in a congenial atmosphere in the pleasant environment of the Runnymede Hotel, Egham, Surrey, and having attended my first such event on 21–22 September last, I can now confirm that this is indeed the case. The Thames‐side location has obvious attractions, but it was more the feeling of camaraderie that prevailed among the 110 delegates which added to enjoyment of the two‐day conference.
The Production and Through‐hole Plating of Modern Base Materials
Authors: Haug Th. , Magnani P. , Bressel B. , Grapentin H.‐J. , Meyer H.
Published: February 2008

Today modern epoxy base materials for printed circuit board production are designed with properties which ensure high dimensional stability, resistance to chemical action, and increased glass transition temperature, in order to meet the stringent demands now encountered in electronics use. Polyfunctional epoxy resins and the appropriate hardener/accelerator compositions are in widespread, effective use in the design of superior laminates. The quality of the through‐hole plating for holes drilled in these improved materials will depend on various parameters, including those covered by three main complexes: base material, mechanical processing, and chemical processes used for treatment of the drilled hole. Special attention is paid in this paper to the resin recession phenomenon in terms of processing parameters.
Application of Non‐destructive Testing to Inspection of Soldered Joints
Authors: Forshaw M.
Published: February 2008

There is an increasing requirement for inspection of electronic components, assemblies and interconnections, and to meet this demand there are new developments in inspection techniques. None of the techniques is universally applicable, but many are capable of consistent and reliable results. This paper outlines the major techniques which are available and summarises their capabilities. The limitations on types of component and boards which may be examined are listed, and the difficulties of detecting some flaws with some techniques are highlighted and the reasons considered.
Restrictions on the Production and Consumption of CFC‐113—An Update
Authors: Lea C.
Published: February 2008

An earlier paper gave the background to the rôle of chlorofluorocarbons (CFCs) in the observed depletion of the Earth's stratospheric ozone, plus details of the Montreal Protocol that restricts the production and consumption of CFCs. In this paper, recent data on both the ozone depletion and the global greenhouse warming that result from CFC emissions are given. The progress by the chemical companies to identify replacements for CFCs is also discussed.
The Feasibility of Ultrasonically Bonding Surface Mount Components to Printed Circuit Boards
Authors: Goold E.
Published: February 2008

The potentially highly automated process of surface mounting electronic components directly onto a substrate or printed circuit board possesses a very weak link. Component movement subsequent to placement and before or during solder reflow leads to defect conditions such as tombstoning or rotational misalignment. This work investigates the feasibility of replacing this ‘weak’ assembly step(s) with ultrasonics. The selection and modification of suitable ultrasonic equipment is described as in the bonding of chip components onto PCBs. Reliability analysis of the resultant bonds along with bond quality in terms of shear strength and appearance under scanning electron microscope and optical microscope is studied. The results show that, with certain preferred directions of ultrasonic weld, weld preload and weld time bond strengths obtained compare very favourably with those achieved with the present surface mount technology reflow process, hence establishing the feasibility of ultrasonics for this application.
Adhesion Test for Dry Film Photoresist on Copper by the Peeling Method
Authors: Lu N.‐H.
Published: February 2008

This study describes a peel test to quantitatively measure the adhesion of dry film photoresist on copper. Using this peeling method, the adhesion effects of: (a) the copper surface treatments, (b) the UV radiation of a laminated resist, and (c) the baking of a resist laminated coupon were measured. Adhesive tape with rectangular or wedge‐shaped openings was placed between the photoresist and copper surfaces with the adhesive side facing the resist. The openings in the tape allowed for contact between the copper surface and the resist, and the opening dimensions determined the width and length of contact. With the aid of the adhesive tape, a better grip of the resist was obtained during the peeling. The results of this study led to the following conclusions: A tin‐silane (SNS) treated copper surface with a peeling strength of 4–7 lbs/in. was the most effective surface treatment. A UV radiation dose below or equal to 32 mJ/cm2 produces an adhesion of the resist with micro‐etched copper of 38±03 lbs/in; above this dose, adhesion increases. Thermal baking improves adhesion; the calculated activation energy of a micro‐etched copper surface with the resist is 65 kcal/mole.
Centrifugal Cleaning—A New Technology for Cleaning Printed Circuit Boards and Hybrid Circuits
Authors: Rich R.
Published: February 2008

Cleaning or defluxing of populated printed circuit boards has become a very difficult problem as component stand‐off clearances have become smaller, line spacings tighter, and solvents limited because of the CFC/ozone issue. This paper discusses the new technology of Centrifugal cleaning where ACCEL Energy™ is harnessed inside an enclosed chamber to provide significant cleaning benefits. Among these benefits are: superior washing, effective rinsing, superior drying, reduced solvent consumption by orders of magnitude, small footprint, and compatibility with H2O, saponifiers, chlorocarbons, fluorocarbons and terpenes.