bluuebunny/crossref_metadata_2025 huggingface dataset:
Blowholing in PTH Solder Fillets
Authors: Howie F.H. , Tilbrook D. , Lea C.
Published: February 2008

For a given batch of printed circuit boards of a particular quality and with a particular level of moisture absorption, the parameters of a wave soldering machine may be tuned to minimise the amount of visible blowholing. This paper shows the inter‐relationships of blowholing with other soldering faults such as icicling, bridging and poor pull‐through. The inter‐relationships result from adjusting each machine parameter in turn. This is important since blowholing cannot be minimised without regard to these other effects. The effect of the quality of the printed circuit boards on the response to machine parameters is predicted from a model, and measurements are found to be in agreement with the predictions.
Some Causes of Problems with Existing SMT Solder Creams and Possible Improvements
Authors: MacKay C.A.
Published: February 2008

Many of the common defects observed when using solder creams can be related to the materials, formulation and blending of the product. Despite the fact that they have been used for the last 15–20 years some of the most serious of these problems remain. A correlation between material parameters and defects is presented. The three most serious defects are identified as Voids, Solder Balls and Residue and Cleanability and the mechanism and occurrence of these are discussed extensively. Suggestions are presented as to material and process improvements to reduce or eliminate the problem areas. Finally the suggested improvements are tabulated to indicate the effects on all the defects originally identified.
Optimising the Drilling and Etch‐back Parameters in Flexible Multilayer Manufacture
Authors: Menzel R.
Published: February 2008

For the drilling of polyimide multilayers with acrylic adhesives, more care must be taken than for epoxy glass material. Due to the different mechanical properties in the multilayer ‘sandwich’ of the polyimide and the acrylic adhesive layers, the drilling parameters require a higher level of control. To avoid defects in the hole, such as nail heading of the polyimide or an uncontrolled ‘rip‐out’ of the acrylic adhesive, the relation between the cutting speed of the drill and the feed needs to be adjusted for each drill diameter. The following guidelines are valid: Wider drill diameters require a lower rotational speed and a lower feed to avoid deformation of the polyimide in the hole. Smaller drill diameters need high rotational speeds and a higher feed to minimise smear. In general, the drilling performance of wider drills is better than that of smaller drills. In all cases, it was impossible to prevent smear of the acrylic adhesive in the multilayer holes. The only reliable method for removing acrylic smear is by plasma etching. The minimum etch‐back required for acrylic adhesive was found to be ≥6 µm, which would be equivalent to an etch‐back of only 2 µm of the polyimide film. To achieve the etch‐back rate, the time in the plasma chamber should be between 20 and 30 minutes at 90–110°C. After the etch‐back, a high pressure water rinse is needed to remove some residues in the hole prior to through‐plating.
Surface Mount Technology in Japan—From Consumer Electronics to Supercomputer
Authors: Nakahara H.
Published: February 2008

First, a short history of surface mount technology is given, followed by a section describing the current status of surface mount components and the impact of these on printed wiring boards. Then, two essential steps of SMT, component mounting and soldering, as practised in Japan, are discussed. The advantage of additive technology for SMT is briefly reviewed.
Packages for High‐density Surface‐mount Applications
Authors: Love G.F.
Published: February 2008

This paper addresses the various types of surface mounted packages used today for high‐density packaging of Very Large Scale Integrated devices. The paper discusses the pros and cons of both the leaded and leadless package, and provides the reader with general guidelines for their use.
Surface Mount Assembly Problems Elimination of PC Solder Resist
Authors: Hamilton P.G.B.
Published: February 2008

The successful formation of solder joints to attach surface mount devices to multilayer printed circuit boards requires the electroplated, reflowed tin‐lead surface of the connection land to be completely free from contamination prior to the application of solder cream. Solder resists and their application methods are seen as the most common source of contaminant and the elimination of this process, at least on expensive buried logic multilayers, has been seen as the only long term solution. The technology described cannot be applied to double‐sided or four‐layer multilayers using surface mount and therefore the pursual of the ideal solder resist system cannot stop.
Photo‐imageable Screen Printed Soldermasks
Authors: Kingsland J.
Published: February 2008

Over the last few years, the increase in size of printed circuit boards, together with the increase in density of components, has made successful application of soldermask by conventional screen printing more and more difficult. This is despite improvements in both the screen printing resists and the equipment used. The accuracy produced by the photo‐imaging technique has been firmly established with the now almost universal use of dry‐film resist for the plating and etching of printed circuit boards. This led to the introduction of the dry‐film soldermask, but, unlike the dry‐film resists used for plating and etching, this type of soldermask has failed to gain universal acceptance, mainly because of technical shortcomings and high costs. The application of liquid soldermasks overcomes many of these technical problems, although the first attempts to achieve acceptable results required special equipment and huge capital investment. Photo‐imageable soldermasks which can be applied using the conventional printing and exposure equipment, available at printed circuit manufacturers, are now available. Some are processed in aqueous solutions, whilst others are processed in halogenated solvents of the types used in the processing of dry‐film resists. The introduction of such soldermasks makes available the combined advantage of liquid application and photo‐imaging, which will increase the overall quality of printed circuit boards produced, while utilising existing screen printed, oven, photo‐exposure unit and conveyorised spray developer.
CQM—Consistent Quality Manufacturing of Laminates
Authors: Carreman J.
Published: February 2008

A process for continuous pressing of copper‐clad laminates is described. The consistent quality manufacturing gives higher dimensional stability and better thickness profile of the FR‐4 laminate. The product also meets UL and MIL requirements.
The Impact of Metal Cored Multilayer Boards for Surface Mounted Devices
Authors: Wilson G.C.
Published: February 2008

The new generation of SMDs (LCCs) can now be mounted on multilayer printed circuits which offer a thermal expansion similar to that of ceramic. In addition, a thermal management solution is available as a means of removing heat generated by the devices. This paper discusses the new development in multilayer board design construction and component assembly associated with metal core boards. New methods of selective plating component footprints are also discussed.
Processing High Performance Multilayer Boards of Fluoropolymer Composite Materials
Authors: Noddin D.B.
Published: February 2008

Methods for producing multilayer boards of highly reinforced fluoropolymer composite systems are detailed. Both similarities and contrasts to conventional fabrication processes are discussed, as well as the relative processing effects on final electrical, mechanical, and physical properties of the MLB. Special emphasis encompasses the dimensional properties of these fluoropolymer MLBs and the overall simplicity of manufacture.
The Testing of Unpopulated SMD Printed Circuit Boards
Authors: Prokopp M.
Published: February 2008

The advent of SMD components will have an enormous influence on the future design of electronics systems. It is evident already that increasing numbers of present‐day surface‐mounted devices are being used for new circuit development. This paper seeks to demonstrate the problems and the potential of an aspect of this trend, the testing of circuit boards constructed for SMD technology.
Ericsson Telecom Ingelsta Multilayer PCB Facility, Norrköping, Sweden
Authors: Cullen Lorna
Published: February 2008

Not infrequently over the past few years it has been brought to Circuit World's attention that a multilayer production facility well worth a visit is the LM Ericsson plant at Ingelsta on the outskirts of Norrköping some 150 kilometres south of Stockholm, the major location of this, the largest electronics corporation in Sweden. The widely acclaimed reputation of the plant derives from its extremely high level of automation by European standards. Discussion with Dr Norman Nichols, recently appointed Director and General Manager at Ingelsta in February of this year, revealed, however, that it is not only the automation aspect which lends this production facility its uniqueness, but also an overriding concern for the human factor. Clearly, here, automation has not meant merely the introduction of programmed robots, with an associated dehumanising effect on the workforce.
Printed Circuit World Convention IV June 2–5, 1987 Tokyo, Japan
Authors: Cullen Lorna
Published: February 2008

Printed Circuit World Convention IV, which took place at the Tokyo Prince Hotel, Tokyo, Japan, from 2–5 June 1987, will be reported in two parts. Part 1, in this issue, covers an introduction to the event, the Opening Ceremony, Social and Accompanying Spouse Programmes, Closing Ceremony and some reflections on peripheral activities. In Part 2, in the next issue, a report on the technical sessions will be published, focusing on the highlights of the technical programme.
Comparison of Dry Film and Liquid Photo‐imageable Solder Masks for Surface‐mount Assemblies
Authors: Tilsley G.M. , Axon F.J.
Published: February 2008

The need for high packing density has led to a requirement for photo‐imageable solder masks, and the increase in surface mount technology is rapidly expanding the use of these systems into consumer electronics in addition to the traditional high‐technology outlets. This paper compares the properties and performance of the two broad types of photo‐imageable systems—dry film solder masks and liquid systems. The manufacturing and coating requirements are outlined. Dry film solder masks are supplied by major chemical companies as high‐quality pre‐formed films while producing coatings from liquid systems is the responsibility of the printed circuit board producer. The process for producing solder masked boards from the two systems is outlined. The relative performance of the systems is compared in detail. Resolution, encapsulation, topography and reliability are considered and these are discussed as well as the requirements for fluxing and defluxing and formation of tented via holes, a highly desirable feature for SMT. Finally, the attractiveness of the more established dry film technology for surface mount boards is summarised, with a request that designers consider the features available and build these into their designs for new circuit boards. Provided the appropriate application system is used and the thickness of dry film solder mask is matched to the requirement, cost advantages can be derived from their use.
Low Dielectric Constant—The Substrate of the Future
Authors: Balde J. , Messner G.
Published: February 2008

Low dielectric constant printed circuit board materials are becoming available. There are four or more materials that can produce boards with a dielectric constant of 28. This paper will discuss the electrical and system advantages of having a lower dielectric constant, and the advantages and disadvantages of each of the principal new materials. In particular, the use of lower dielectric to increase circuit density will be stressed, rather than the more usual expectation that the lower dielectric constant will be used to increase propagation velocity or reduce capacitance. The increase in circuit density will reduce the size of boards, and achieve the reduction in propagation delay even though the capacitance and characteristic impedance are unchanged.
Developments in Passive Thermal Management Systems for Electronics
Authors: Hamilton S.
Published: February 2008

Increasing power densities within electronic equipment have led to a rise in the number of heat related problems being experienced. This paper describes the use of computerised thermal analysis techniques to optimise the design of passive thermal management systems for electronic equipment.
A New, One‐component Dicy‐free Epoxy Resin System Developed for FR‐4 Glass/Epoxy Laminates
Authors: Sexton D.
Published: February 2008

This new system does not use dicyandiamide or any other amine as the curing agent and has no problems with crystallisation either of the varnish or on the prepreg. The system can be used at a relatively low solvent content and the solvents used have favourable toxicity. Since it is a one‐component system it reduces the number of products stored by the laminator and eliminates some blending steps in his manufacturing process. The system produces laminates with an excellent all‐round performance in Tg, moisture resistance, etc. Laminates also exhibit significantly increased resistance to CAF growth, a cause of long‐term failure in PCBs.
Copper Foil for Flexible Circuits
Authors: Avery D.
Published: February 2008

The paper attempts to describe the versatility of flex circuits and discusses how the component raw materials which are used in the manufacture of flexible laminates contribute to this versatility. The focus of the paper is the range of copper foils available for flex circuit manufacture and a discussion of their properties and the metallurgical characteristics which govern these properties.
MIL‐P‐13949 G and Its Consequences for the PCB Industry
Authors: Huschka M.
Published: February 2008

The new military specification for PCB base material was published on February 11th, 1987. This ‘G’ version is not merely an amendment of the ‘F’ version, but basically a new specification with far reaching consequences for both the base material manufacturers and the printed circuit board manufacturers. In this paper the major changes and also the latest introductions are discussed.
Packlayer—Alternative to Conventional Printed Circuit Boards
Authors: Weiss D.G.
Published: February 2008

The printed circuit board version, ‘packlayer’, represents an alternative to printed circuit boards with conventional solder mask systems which is not yet widely known. This alternative type does, however, offer some considerable advantages in comparison with printed circuit boards with solder resist, with the result that the higher cost involved is thoroughly acceptable. Through the development of a new system called ‘Low‐Cost‐Packlayer’, bearing the special name MeSoMask, a variant has emerged within the packlayer sector. This special version combines the advantages of the packlayer with the costs of a conventional solder resist system and therefore presents a genuine alternative to the normal printed circuit board.
Development of Copper‐clad Polyimide Glass Laminates
Authors: Matsuda I.
Published: February 2008

Copper‐clad polyimide glass laminates that pass the GPY/Polyimide Specifications of IPC‐L‐108A have been developed using the Michael reaction of bismaleimide and m‐aminophenol. The addition reaction of m‐aminophenol to N‐phenylmaleimide has been confirmed from NMR, IR, and ultimate analysis. The peel strength of copper‐clad laminates is 1·8–2·0 kg/cm. The coefficient of expansion in the Z direction (25°C–246°C) is 0·96%. The glass transition temperature with post‐curing for an hour at 250°C is about 295°C. Water absorption by IPC‐L‐108A is 0·25%.
Valtronic SA, Les Charbonnières, Switzerland
Authors: Ellis Brian N.
Published: February 2008

Switzerland has an essentially rural image, emphasised by the CH plates on the back of every car; what wag hasn't said that this is because it is the land of CHeese and CHocolate? This image is, in fact, false as the country employs nearly 90% of its work force in manufacturing and service sectors. That having been said, the Vallée de Joux is a beautiful valley, 1000 metres above sea level in the Jura Mountains about 40 km north of Lausanne. The floor of this valley is occupied mainly by two lakes upstream of which are primeval peat bogs. The larger lake, the Lac de Joux, is popular for all sorts of aquatic and ice sports. It flows into the Lac de Brenets, a small lake which has no apparent outlet. In fact, the River Orbe flows out from it underground, to gush out of a mountainside again some kilometres downstream. Above the lakes, cattle pastures slope upwards towards forested escarpments, much admired by nature lovers and, in winter, skiers.
Towards a Busier 1988
Authors: Tyler Roger L.
Published: February 2008

This article is being drafted virtually on the eve of the Productronica Show in Munich. By the time it comes to press, the electronics world will have converged on that beautiful city, gone through the expensive and invigorating process of ‘setting up shop’ in the Munich Exhibition grounds and returned home to face the winter and prepare for the rigours of 1988. It would be interesting to calculate the number of millions of passenger miles that will be travelled by the participants in visiting Productronica and the total costs to the electronics world of this massive event. It obviously goes far beyond the superficial costs of all the exhibition stands, hotel bills and air fares which go towards it and must represent a massive investment for the industry worldwide.
Quality and Reliability — Relevance and Assessment for Electronic Assemblies
Authors: Lea C.
Published: February 2008

The physical and mathematical definitions, as well as the practical significance, of quality and reliability are explained, with particular regard to surface mount electronic components and assemblies. The validity of accelerated assessments of long‐term service performance is also discussed.
Trends in Surface Mounting Technology and Beyond
Authors: Sinnadurai N.
Published: February 2008

Surface Mounting Technology becomes more essential with increasing pin count of ICs. The opportunities for improved performance, miniaturisation and cost are being exploited largely in Japan and increasingly in the USA, but there remains a lack of comprehension and vision in our own community. Nevertheless, there are some very promising developments of packaging and interconnection in the UK and in Europe. While substrates for hybrids and PCBs are heading towards standard Eurocard size, micropackage types are still proliferating rather than consolidating on a preferred standard. Assemblies of these increasing pin‐count components can be soldered reliably, and improved techniques continue to be developed. Quality and reliability of such assemblies are increasingly aided by on‐line vision and inspection procedures including optical, X‐ray and infra‐red techniques. The compactness and complexity require the emerging solutions in design‐for‐testability. Testability and built‐in self‐test revive the viability and emerging trend towards chip‐on‐board (formerly the well established bare‐chip‐and‐wire hybrid technology), now incorporating VLSI and supported by more advanced interconnections including advanced TAB and integrated thin‐film active devices.
Tailored Coefficient of Thermal Expansion Printed Wiring Boards to Improve the Solder Joint Life of Leadless Ceramic Chip Carriers
Authors: Williams R.L. , Noblett A.W.
Published: February 2008

A computer program was used to predict the coefficient of thermal expansion (CTE) of four printed wiring board (PWB) designs. Designs consisted of low CTE materials, E glass/epoxy and copper. Twenty PWBs were fabricated to duplicate four computer models. CTE was measured by a strain gauge technique developed at Boeing. The measured CTE was then compared with the predicted CTE value and a design curve developed. Following CTE verification, the PWBs were assembled with 20, 44, 68, and 84 I/O leadless ceramic chip carriers. The printed wiring assemblies were then thermal shocked from −55 to 125°C and continuously monitored to detect the first solder failure for each I/O chip carrier. The results illustrate the dependence of solder joint life on PWB CTE and verify the use of a computer model to design surface mount PWBs.
PCB Vacuum Bonding Autoclave—Vacuum Bagging Techniques
Authors: Ford G.
Published: February 2008

This paper describes the new technique used by International Computers Limited for vacuum bagging multilayer PCB bonding stacks. It is used as a cost‐effective alternative to previous consumable bagging systems used in autoclave vacuum bonding.
Norplex/Oak (UK) Technical Seminar — High Performance Materials
Authors: Cullen Lorna
Published: February 2008

Conference presentations, the technical literature and industry debate are focusing increasingly on the requirement for high performance laminates to meet the needs of high signal speeds, reduced dielectric constant, controlled impedance, tighter tolerances and improved dimensional stability.
Electronica 88
Authors: Goldie W.
Published: February 2008

It is reputed that PCBs worth approximately £83 billion were produced worldwide by about 7,000 manufacturers with 200,000 employees in 1987. The United States accounted for about 33% of the market and Japan 28%. Well down the list in third place was West Germany with 77%, but by comparison they produced more PCBs than the UK, France and Italy together. However, there is a shift of production facilities for complete PCBs from the high wage‐earning European countries to low‐wage earning South East Asia, i.e., Taiwan, Hong Kong, Singapore and Korea, where substantial capacity is under construction.
Use of Excimer Lasers in the Electronics Manufacturing Industry
Authors: Poulin G.D. , Eisele P.A. , Wong H.B.G. , Znotins T.A.
Published: February 2008

Excimer lasers are finding increasing use in the electronics manufacturing industry. In contrast to other types of laser processing in which material is removed by localised heating, excimer laser processing involves a non‐thermal ablative material removal mechanism. This is due to the ultra‐violet output and short pulse duration of these unique light sources. The result is a high precision means of patterning thin dielectric films, removing such films from metal substrates, or removing thin metal films from underlying dielectrics. Through proper selection of operating parameters it is possible to achieve smooth sidewall profiles with selectable amount of taper while leaving the surrounding and, in the case of film removal, the underlying material virtually untouched. This paper will review the growing use of excimer lasers in applications such as the skiving of access holes and windows in flexible wiring, the drilling of via holes for multilayer boards, the stripping of microwires and other chip bonding applications. The differences between excimer laser processing and conventional laser based techniques will be highlighted.
Technological Implications of Restructuring in the European PCB Industry
Authors: Hannon M.
Published: February 2008

The EEC Nation States' 1992 Single Market awareness campaigns have achieved their objectives. The underlying EEC policies have ignited a fuse which will lead to an increase of Corporate Activity in the European PCB Industry. Having witnessed a rash of OEM activity including acquisitions, disposals and equity swaps there is now the feeling of the pace quickening in the PCB industry. This short paper looks at the technological implications of PCB Industry restructuring on a European scale and provides at least a taste of the larger global restructuring of which it is a part. The paper first views the European Electronics Industry restructuring and the types of deals involved, then analyses some recent PCB Industry activity before going on to draw some implications for the Technical and Production Manager. The other option, Organic growth, is not covered in this article as it is felt the reader will be more aware of this route to growth.
Contamination Control and the Montreal Protocol
Authors: Ellis B.N.
Published: February 2008

This paper gives a general survey of the methods of contamination control related to assembled printed circuits. Particular emphasis is given to those aspects of the subject which are currently in a state of change because of environmental difficulties, notably those due to the curtailment of use of chlorofluorocarbon solvents.
GE Plastics Demonstrate Robotically Controlled Laser Fabrication of Moulded Circuit Boards
Authors: Moran P.L.
Published: February 2008

The applications team of GE Plastics in Russelsheim near Frankfurt, in common with several other GE groups, has been working in the general field of moulded circuit boards for many years. Recently, however, they have taken the imaginative step of developing a fundamentally new approach to moulded board processing and by working closely with several companies brought the technique to the point where it is possible to add electroplated copper tracking in three dimensions to any suitable moulding made of an appropriate plastic without the need for any additional tooling. In order to launch this technology, GE held a seminar in front of an invited audience in Russelsheim on 25 and 26 January, the earlier date being for German speaking participants and the later English. It is a measure of the interest in this technology that almost all the invitations were taken up and there was standing room only in the lecture theatre. As anybody familiar with moulded circuit boards will be aware, the technology employs skills from several disciplines and considerable congratulations must go to U. Hartman of GE for organising the programme and co‐ordinating the work of the participating companies.
International institute news
Authors: Cullen Lorna
Published: February 2008

The California Circuits Association has moved to the following new mailing address: CCA, 8855 Atlanta Avenue, 210 Huntington Beach, CA 92646. Telephone: (714) 536 3519.
Base Materials with Predetermined Technological Properties for Advanced PCB Production Processes
Authors: Borisov M.B. , Belkin N.D. , Toushinsky A.I. , Evzhenko V.M.
Published: February 2008

The design and technological requirements of base materials for PCB production are considered. The problems of catalytically active base materials development and production are also discussed. Examples of the realisation of the problem under consideration are given.
Wave Soldering Concerns for Surface Mount Assemblies
Authors: Elliott D.A.
Published: February 2008

For over 30 years, wave soldering has been the most popular and most economical method for mass soldering of electronic assemblies. For conventional circuits, this is a mature technology. Training, proper board design, process control during board fabrication, assembly and soldering and, finally, an awareness of the need for solderability have resulted in very high manufacturing yields in some companies with the associated high quality and much improved profits which result by doing it right the first time. With the introduction of surface mount technology, the same concerns need to be addressed. However, due to the smaller size of components and higher densities, new problems arise. This paper presents some of the concerns encountered in wave soldering of surface mount assemblies.
Improved Printed Circuit Reliability by Risk Site Analysis
Authors: Haining F.W. , Shaul R.F. , Keim R.W. , Murcko R.M.
Published: February 2008

The circuit elements of every printed circuit board have the potential for failure during test and/or use. These failures can occur by forming short‐circuits between adjacent circuit elements, or by forming open‐circuits in the conductors. The risk sites can be identified by type, and the total number enumerated by manual inspection of the photolithographic masks used to fabricate the printed circuit layers. However, the circuit density of high performance printed circuit boards has become so great that meaningful manual analysis has become impractical. A more effective method is to use special graphics programs to analyse the computer‐aided design (CAD) data. The methodology developed to perform the CAD analysis of high performance printed circuit boards for short‐circuits utilises two powerful computer graphic tools: the Interactive Graphics System and the Unified Shapes Checking system. Test data for open‐circuits are generated using specially written alphanumeric routines. The data can be used for stress testing the printed circuit boards by wiring up special test modules that are plugged into the boards and then placing the boards into environmental test chambers. The printed circuits are checked for short‐circuits by putting them into groups that have no risk of shorting to each other (zero risk), and placing the groups in parallel under an electrical potential. The flow of current between the groups would indicate a short‐circuit. Similarly, the printed circuits can be checked for open‐circuits, by stringing them together into groups in series, and measuring the changes in resistance under thermal stress. Both types of test data can also be used for in‐process testing.
Overview of Tape Automated Bonding Technology
Authors: Lau J.H. , Erasmus S.J. , Rice D.W.
Published: February 2008

A review of state‐of‐the‐art technology pertinent to tape automated bonding (for fine pitch, high I/O, high performance, high yield, high volume and high reliability) is presented. Emphasis is placed on a new understanding of the key elements (for example, tapes, bumps, inner lead bonding, testing and burn‐in on tape‐with‐chip, encapsulation, outer lead bonding, thermal management, reliability and rework) of this rapidly moving technology.
Development Scheme of a Novel Polyimide Matrix System for Multilayer Boards
Authors: Lopez P.R. , Giraud Y.J. , Koonce S.J.
Published: February 2008

Following a quick survey of the resin systems commercially available, this paper focuses on the design considerations of high temperature matrices. The report examines in detail the key points of the final target properties of a resin system and, by illustrating some of the transfer mechanisms, how they relate to the matrix reinforcement and the copper environment. Based on this, the construction of a development scheme incorporating the various parameters relating structure, chemistry and properties is presented. In high temperature systems, particular emphasis is placed on fracture toughness and related effects in the case of polyimides, such as copper peel strength, delamination, cracking subsequent to drilling operations or thermal cycling. The conclusion is that the number of controllable matrix parameters is surprisingly small: Tg, CTE, K1c/G1c, modulus and elongation at break, in addition to a few others. Finally, this study shows how all of these data were collectively applied to the practical development of a new Kerimid(™). Further studies are now under way to enhance the importance of additional parameters regarding more complex phenomena such as the drilling operation.
A New Strategy in the Recycling of Printed Circuit Boards
Authors: Legarth J.B. , Alting L. , Danzer B. , Tartler D. , Brodersen K. , Scheller H. , Feldmann K.
Published: February 2008

The resource parameter in life cycle assessments is used to evaluate present efficiency in resource recovery from printed circuit boards. It is shown that only a fraction of the resources held by PCBs are recovered today, and that in order to improve resource recovery a good knowledge of the chemical content of electronic components is necessary. Analytical techniques specially suited to the analysis of electronic components are discussed, and it is concluded that critical resources are indeed concentrated in certain electronic components. Finally, an automated system for removing components from the boards and for recognising and sorting the components is discussed.
Characterisation and Evaluation of the Underfill Encapsulants for Flip Chip Assembly
Authors: Wun B. , Lau J.
Published: February 2008

Studies of solder‐bumped flip chips on organic substrates reported in the literature have so far suggested the necessity of a polymeric underfill to compensate for the large thermal mismatch between the silicon and the substrate. In this company's target applications of this process, the underfill not only has to meet the much published mechanical and chemical requirements, but also has to flow through a vertical clearance of 0.020 to 0.0375 mm quickly as well as being cured in a relatively short time. The evaluation of the underfill materials starts with some basic understanding of how the different ingredients in the underfill formulation might affect its physical and chemical properties. The flow characteristics of the underfills were a first priority in the selection. A detailed thermal‐mechanical analysis then helped to determine the optimal cure schedule with the desired physical properties. A simple test die/test board system has been designed to evaluate how the underfill might work in a quasi‐production process and to allow for subsequent reliability evaluation. This paper highlights the ‘pluses and minuses’ of the currently available commercial underfills in relation to the optimisation of a high‐volume production process.
High Strength, Low Profile Copper Foil for High Performance PCBs
Authors: Chiang S.K. , DiFranco D.F. , Pucci D.G.
Published: February 2008

A new high strength, low profile copper foil (AM) has been developed by the authors' company. This foil is designated AM foil, which refers to its advanced metallurgy. The unique attributes of this foil arise from its unconventional processing approach and the resulting microstructure. An extremely small and uniform grain structure enhances the metallurgy and decreases the foil profile. Random crystal orientation and high nucleation density eliminate porosity for all foils of various thickness. Other benefits related to this high strength and low profile foil include good handleability, outstanding etching performance, better control of dielectric thickness, very high elongation to reduce innerlayer cracks, improved oxide adhesion, as well as other advantages.
A Model of the Solder Flux Reaction; Reactions at the Metal/ Metal Oxide/Electrolyte Solution Interface
Authors: Nasta M. , Peebles H.C.
Published: February 2008

A good solder flux must simultaneously perform a number of important functions. It must promote thermal transfer to the area of the solder joint, enhance wetting of the solder on the base metal, and prevent oxidation of the metal surfaces at soldering temperatures. However, its primary task is to remove the tarnish layer from the metal joint that is about to be soldered. Despite the fact that the process of soldering electronic devices is a part of a multi‐billion dollar industry, the actual chemical reactions that occur during this cleaning process are not well documented. In the case of organic acid or water‐soluble fluxes, the flux reactions can be modelled by considering the interactions at the metal/metal oxide/electrolyte solution interface. Although such modelling systems have not frequently been applied to the behaviour of solder and fluxes, they are common for a number of other closely related chemical systems which are of practical interest, e.g., passivation layers on metals, electrochemical cells and metal oxide semiconductors. There are two types of reactions that can occur at the oxide/solution interface: acid‐base reactions and oxidation‐reduction reactions. The factors which affect the reaction rates and mechanisms are such variables as the structure of the metal oxide, temperature, pH, concentration of the electrolyte, and the chemical nature of the solute and solvent. By combining information about flux behaviour with available models of surface reactions, it should be possible to develop the theory of the flux reactions and to gain a better understanding of the factors which control the process.
Some Fundamental Aspects of UV Laser Direct Imaging
Authors: Choi J.H.
Published: February 2008

Photoresist imaging traditionally uses silver halide or diazo based phototools for contact exposure to an actinic UV light source. By contrast, laser direct imaging uses digital imaging data to control a laser beam scanner to write directly on to the photoresist, therefore eliminating the need for phototools. In the past, even though the benefit of a UV system was recognised, laser direct imaging was mainly limited to the use of a visible laser as early UV lasers were low in power, unreliable and expensive. So far, no visible systems have gained commercial recognition because of the inherent deficiencies of the visible system. Recent advantages in UV laser equipment and UV sensitive photoresist have now made UV laser direct imaging a viable alternative to traditional contact imaging. As new UV laser imaging systems start to emerge, interest and attention are also growing among printed circuit board manufacturers. This paper discusses various attributes of a UV laser direct imaging system and fundamental differences in photophysics between laser direct imaging and conventional UV imaging.
Weak Organic Acids and Surface Insulation Resistance
Authors: Sohn J.E. , Ray U.
Published: February 2008

Weak organic acids (WOAs) are commonly used as activators in no‐clean fluxes. Surface insulation resistance (SIR) was determined as a function of WOA type and residue level through three temperature/humidity test environments. Acidic residue levels were determined after wave solder processing, and after exposure to each of the three test environments. With each of the WOAs studied, the greater the residue level, the lower the SIR. Chemical structure and physical property differences of the WOAs are discussed in the context of differences in SIR observed. WOA volatilisation is found to occur with all four WOAs when exposed to the highest test temperature (85°C). This work shows that testing WOA‐containing solder fluxes at 85°C may not be useful or appropriate.
A Review of Distributed RC Thick Film Components
Authors: Moran P.L.
Published: February 2008

Some of the unique properties of distributed RC thick film components are reviewed and discussed. In particular the evolution of a method of functionally adjusting active low pass filters containing distributed RC components is presented. The use of a finite element computer programme, specially written for this work, to justify the validity of the trimming method is demonstrated. The problems remaining in the development of the technique are mentioned and the potential for overcoming them is discussed.
The Use of Polymer Thick Film for Making Printed Circuit Boards
Authors: Martin F.W.
Published: February 2008

The electronics industry is facing a situation in which the cost of electronic functions is dropping continuously while the cost of interconnecting the functions by traditional means, especially through the use of printed circuit boards, continues to rise. Polymer thick film is one proven approach to reversing the trend of rising interconnection costs. It is relatively easy for the typical printed circuit board manufacturer to convert to or adapt polymer thick film because he has most of the necessary equipment, technical knowledge and personnel.
Complementary Technologies—A Comparison of Electronic Packaging Technologies for Circuit Realisation
Authors: Spiller D.O.
Published: February 2008

This paper outlines the results of a study (initiated in June 1981) of the optimum packaging and interconnection techniques for a specific electronic sub‐system which was to go into production by the end of the first quarter of 1982. The risks and advantages of using various technologies were investigated and the technology chosen was a compromise between manufacturing cost, risk and time scale.
EMPIRIC/SHM—A Noble Art
Authors: Kirby P.L.
Published: February 2008

As Vice‐President of ISHM‐UK, I am very pleased to have this opportunity to express a few thoughts about our technology in this first issue of the new Journal. In the UK we do not have a ‘President’ of our Society and thus the post I have the honour to hold may appear as the first of numerous anomalies and inconsistencies which abound in the subject area in which we work.
Processing Polymer Thick Film Circuitry with Radiation Curing
Authors: Green W.J.
Published: February 2008

Polymer thick film, as an additive process for making circuitry, is not new but has recently received considerable attention. The process has a number of attractive features to offer and when radiation curing is used to accelerate the curing process the technology becomes even more attractive. To be accepted by industry on a large scale, however, these materials must be certified by independent circuit board testing laboratories. Using infra‐red as the curing process, Methode prepared a polymer thick film version of a test pattern used for testing to Mil 55110 and produced some very promising results.
Automation of Resistor Networks, CTS, USA
Authors: Simon J.
Published: February 2008

For several years, competition within the resistor network industry has greatly increased sizeable increases in demand. To remain competitive and a leader in the field, CTS Corporation has chosen to initiate constantly new technologies for automation. To improve overall costs, automation must take place in the area of support personnel such as clerks, engineers, management and technicians as well as with the direct production workers. It is also believed that automation should take place under a well formulated planning system. Some of the techniques being implemented at CTS of Berne to accomplish this come under discussion. First, the capability of the process should be proven. Dealt with briefly are ways in which this is accomplished and the important role it plays in the fore‐running steps of automating. Before an automation project is undertaken, the payback to the company must be assured. The steps taken to accomplish this, starting with determining the variance in output rates (not cycle rates), yield and/or quality improvements, acquiring quotations, establishing total costs, and finally computing the ROI and payback factors are all reviewed. CTS Corporation has graduated from high labour intensified manual operations to semi and fully automatic ones. Some of the techniques used to effect this transition such as bowl and vibratory feeders, walking beams, and pick‐and‐place units, are discussed. Also portrayed is the way in which a constant improvement in the automation of the process and material handling is being undertaken at CTS. Among the new generation developments are: Multiple handling of parts via tubes, magazines, and pallets; robotics; automatic 100% visual inspection, and computer and microprocessor controlled processes.
Thick Film Screen Techniques
Authors: Hargrave C.E.
Published: February 2008

Basic properties of screen materials are defined, with a study of different mesh formations and coatings and their effect on the printed image. Detailed specifications are given for a range of stainless steel, polyester, and nylon fabrics. A table then summarises recommendations for specific thick film applications such as conductor tracks, fine line conductor tracks, resistors, solder paste deposition, dielectric layers, and overglazes. The requirements for the artwork and photopositive are examined, with recommended procedures for exposing and processing the mask. The survey concludes with notes on other factors which commonly influence quality at the print stage.
Gate Array Packaging—The Forgotten Problem
Authors: Silver N.
Published: February 2008

As semi‐custom devices increase in complexity, much time is being devoted to solving the problems of automating their design. The associated problems of packaging are being overlooked. The increasing pin count is becoming a major problem. Surface mount components and hybrid circuits are proposed as a solution.
Alumina with a Thermal Conductivity Close to Beryllia
Authors: Val C. , Humbert N.
Published: February 2008

Previous studies on special dielectrics for multilayer screen printing led to defining a new concept for standard alumina substrate. The modification of the process and structure permits an increase of the thermal conductivity. The thermal conductivity of this new material is between that of alumina and BeO. It is possible to increase the thermal conductivity of 94% standard alumina (used in chip‐carriers) up to 3·6 times. It it known that the thermal conductivity of beryllia is 7 times higher than that of alumina. The thermal model gives an increase of 4 times for other configurations non‐tested in this study. With this material, the other characteristics such as thermal expansion, adhesion of the conductors, etc., scarcely change. The ‘percolation’ effect of the physical properties can usually be found with the addition of another material inside the matrix. In this particular case, the material is not submitted to the percolation law. Different configurations of metallic insert alumina with beryllia are compared by a simulation programme. The main applications are in the field of electronic packaging such as chip‐carriers with higher thermal dissipation and substrates for power devices. Since the process used to produce this new material is based on standard operations well known by alumina manufacturers, the cost is potentially much lower than for BeO.
ISHM news
Authors: Waterfield Brian , Moran Peter , Sinnadurai Nihal
Published: February 2008

ISHM (UK) presented a technical meeting on this topic on the 23rd October 1982 at the Cunard International Hotel, London. The meeting was attended by some 50 engineers, both those involved in the field of hybrids and potential users. It was generally felt that this was a useful meeting but more especially that it would have appealed to many potential users of hybrids, had the right people been able to be contacted.
Studies of Thick Film Thermistors
Authors: Fu S.L. , Chiou R.M.
Published: February 2008

Thick film thermistors based on the thermistor powder of the sintered ceramic thermistor, prepared from oxides of nickel, cobalt and manganese, were fabricated and studied. The ingredient compositions, including the composition proportions, influenced the properties of thick film thermistors. The effects of the compositions of the sintered ceramic thermistors, the amounts of additives used and the compositions of the glass binders on the properties of the thick film thermistors were also studied.
Microwave Integrated Circuits on Alumina Substrate up to 20 GHz Frequency Range
Authors: Giavarini A. , Ferraris G.P. , Marconi F.
Published: February 2008

A line of thin film microwave integrated circuits (MICs) on alumina substrate in the microwave frequency range up to 20 GHz is presented. Technological aspects and electrical performances are shown.
ISHM news
Authors: Kersuzan G. , Batt Nigel , Waterfield Brian , Law Hamish , Herod B. , Whiteside M.A. , Sinnadurai Nihal
Published: February 2008

The International Electronic Components Show in Paris in November, 1983, provided the occasion for a very successful meeting of ISHM‐France which attracted 170 attendees. The following presentations were given:
Modèles de Calcul Précis pour la Détermination de l'Augmentation de Température de Sources de Chaleur Rectangulaires dans les Circuits Hybrides
Authors: Kersuzan G. , van Nie A.G.
Published: February 2008

To enable adequate transfer of heat from a hybrid circuit in many cases the substrate is attached to a heatsink. This paper examines the two principal means of calculating the dispersion and transfer of heat generated by active elements on the surface when both thin and thick film techniques are employed. The paper concludes by presenting formulae for making the relevant thermal resistance calculations.