bluuebunny/crossref_metadata_2025 huggingface dataset:
Proper Selection of Tip Style and Tip Temperature for PCB Connections
Authors: Urban P.L.
Published: February 2008

Control of soldering process variables dictates the quality of a hand soldered connection and among these feature the important parameters of tip temperature and tip style. Experimental work has investigated the temperature/time characteristics of typical PTH boards and the results are analysed, showing that maximum land temperature is increased when tip temperature is increased. Tip size causes variations in maximum land temperature at any selected tip temperature.
The Importance of Cleaning Equipment in PCB Assembly
Authors: Lambert W.
Published: February 2008

Factors relating to the cleaning of PCBs after soldering are examined, whereby the need to remove flux residues is justified and the choice of suitable cleaning agents analysed. After a description of recommended equipment design involving a 2‐stage system, methods of automating this are outlined.
Observations on the Growth and Impact of Intermetallic Compounds on Tin‐Coated Substrates
Authors: Warwick M.E. , Muckett S.J.
Published: February 2008

Tin and solder coatings interact with substrates commonly used in the electronics industry to produce layers of intermetallic compounds at temperatures above and below the melting point of the coatings. Observations on the rates of compound growth at room temperature for durations of up to 12 years are reported and related to the published results for shorter times at higher temperatures. Recent results concerning the effect of intermatallic compound growth on the solderability of coatings and on the strength of soldered joints are presented. In both cases it is apparent that retarding the rate of compound growth could be useful and the use of barrier layers for this purpose is considered.
Outgassing of Solder Joints: ‘Causes and Cures?’
Authors: Jones S. , Starkey P.
Published: February 2008

Financial and commercial pressures have led to the increasing trend for PCB users to want to reduce or eliminate rework after mass soldering. Whilst the phenomenon of outgassing is recognised, it is not generally well understood by either the manufacturers or users of PCBs. It is the intention of this paper to clarify and focus attention upon some apects of the problem from the manufacturing side of the industry.
Printed Board Assembly Cleanliness—Standards, Practice and Reliability Considerations
Authors: Taylor J.R.
Published: February 2008

The transition to complex printed board assemblies in modern high technology equipment is described. These low voltage, densely packed PBAs with their decreasing insulation paths, manufactured for greatest speed with highly activated solder fluxes, demand both awareness and action to achieve the degree of cleanliness compatible with reliability requirements. This paper sets forth activities under way in Australia to define and adopt cleanliness Standards for use throughout the nation's manufacturing industry. It identifies and defines cleanliness and methods used to achieve and measure contamination that is introduced during PBA manufacture.
Automatic Component Insertion
Authors: Nicholson E.N.E.
Published: February 2008

The Author's company was the first in New Zealand to install automatic insertion equipment. The paper covers the appraisal of the following systems: manual insertion; semi‐automatic insertion; and automatic component insertion. The last of these comprises various types, namely bench type, pantograph machine, computer controlled (axial lead and general) and an in‐line assembly system. The computer controlled axial lead insertion equipment including design criteria is detailed at length, with some discussion of advantages.
Surface Mounted IC Packages—Their Attachment and Reliability on PWBs
Authors: Brierley C.J. , Pedder D.J.
Published: February 2008

The hermetically sealed ceramic chip carrier package and the plastic small outline (SO) IC package are both now widely used in hybrid microelectronics. These packages are currently being applied with other discrete surface mount devices to PWB technology in order to increase circuit density and reduce weight. This paper discusses the evaluation of two soldering techniques for the attachment of the chip carrier and SOIC packages to epoxy glass PWBs: the first by solder cream printing or pretinning of the circuit board and subsequent attachment by solder reflow, and the second by a novel jet soldering technique. The thermally induced expansion mismatch between epoxy glass and ceramic chip carriers and the strain induced fatigue this causes in the solder joints are now well documented, and results are presented for the effects of temperature cycling ceramic chip carriers soldered onto PWBs. Various PWB materials have been assessed including FR4, elastomer coated FR4, polyimide kevlar, and epoxy glass laminated copper clad invar. Reliability of these assemblies is discussed in terms of the appearance of micro‐cracks in the solder fillets and the occurrence of electrical discontinuity in the solder joints during temperature cycling.
The Meniscograph as a Quality Control Tool—A Case Study in Solderability Testing
Authors: Bolton J.T.
Published: February 2008

With the ever increasing requirement for improved mass soldering defect levels, more and more emphasis is being placed on process control, one of the major variables being solderability, the testing of which was until recently very subjective.
Printed Circuits—Origins and Development
Authors: Pole‐Baker M.E.
Published: February 2008

Multilayer boards development. The American Tinkertoy and Micromodule programmes had shown that layers of etched circuits could be built up to provide a complete unit, and high densities could be achieved. The Hazeltine Corporation in America perfected a technique in which three or more layers with coincident holes were bonded together with insulating sheets and the layers connected through by using the existing plated‐through hole technique. Their ‘Multiplanar’ process was disclosed in 1961, and is the only accepted method of making multilayer boards today, and the one on which all existing specifications are based.
Surface Mounting Assembly—A Practical Approach
Authors: Edwards P.F. , Stone R. , Willard G.A.
Published: February 2008

A general introduction is given to surface mounted devices, processes and machinery, followed by Mullard Electronic Assemblies Division's experience and a description of practical assemblies using surface mounted devices. Thoughts of future possibilities and requirements of substrate systems for the advancement of surface mounted assemblies are also presented.
Low Temperature Soldering
Authors: Strauss R. , Smernos S.
Published: February 2008

Soldering of electronic components on printed boards generally takes place at temperatures of between 240 and 250°C. During soldering, the components and printed boards are exposed to thermal shock that affects their long‐term reliability. A reduction in the soldering temperature to about 180°C using low melting point solders is expected to decrease component failures. The authors describe tests on a number of possible solders and the development of a suitable low temperature flux.
Tape Automated Bonding and its Impact on the PWB
Authors: Small D.J.
Published: February 2008

This paper briefly reviews the impact that tape automated bonding systems are having in the semiconductor industry and describes a recent development of a bumped testable TAB system suitable for direct assembly to PWBs. The impact that such a system will have on PWB technology is discussed.
Commercial focus
Authors: Smithson D.
Published: February 2008

Fibral materials consist of a matrix of nylon fibres through which a resin and abrasive slurry is sprayed. The slurry coats the fibres and, after drying and curing, the resin bonds the fibres together at their intersections and also bonds the abrasive grain to the fibres.
Printed Circuits—Origins and Development
Authors: Pole‐Baker M.E.
Published: February 2008

he development of printed circuit technology is almost inseparable from the development of materials. Copper clad laminates could be said to have started with the discovery of phenolic resins by Dr Leo Baekeland in 1909. He found that by using catalysts he could control the speed and extent of the reaction of phenol with formaldehyde, suspending the reaction at any time to add reinforcements. Using resins in a liquid form he was able to combine them with wood cloth, paper or fibre to build an insulating material.
The Role of Resin in Moisture Induced Laminate Failure
Authors: Vaughan D.J. , Householder K.A.
Published: February 2008

This paper considers the moisture induced failure of glass reinforced epoxy laminates, showing the loss of electrical properties versus time whether the environmental parameters are temperature or water. The authors describe in depth how moisture induced failure occurs. It is shown how water and various environments weaken the resin and result in premature laminate failure.
Troubleshooting Wave Soldering Problems with Statistical Quality Control (SQC)
Authors: Prasad P. , Fitzsimmons D.
Published: February 2008

In an attempt to reduce the incidence of wave soldering defects on printed wiring assemblies, Boeing Electronics Systems Division (BESD) has been investigating and implementing SQC (Statistical Quality Control). The concept is introduced in its historical context, explained and its application by this company to troubleshoot wave soldering problems outlined. Detailed results are provided to illustrate the value of the technique and indicate the important variables influencing soldering quality.
Techniques for Soldering Surface Mounted Devices to Printed Circuit Boards
Authors: Brierley C.J. , Considine L. , Pedder D.J.
Published: February 2008

The screen printing and reflowing of solder paste is compared with wave soldering for the attachment of surface mounted devices to PCBs. Both techniques have advantages and disadvantages which are fully discussed. The method chosen for a particular application will depend upon the production facilities available, the principal package types involved in the design, and the anticipated cost. The main advantages of the screen printing process have been found to be a relatively low soldering temperature, freedom from device orientation and package design constraints, and few proximity effects, while those for the wave soldering process have been found to be compatibility with present mass soldering operations, the ability to combine both through‐hole devices and SMDs on the same board, a single soldering operation, and a solder joint volume defined by the joint design. It is concluded that in the long term screen printing and reflow is likely to become the dominant technology, but in the intermediate term wave soldering is likely to remain attractive while manufacturers move from the established through‐hole technology to the more space‐efficient surface mounted technology.
Factors Involved in the Design and Manufacture of Bonded Heat Sinks
Authors: Pearl L.
Published: February 2008

A review has been made of the various factors involved in the design and manufacture of bonded heat sinks for printed circuit boards. Among the factors discussed are the design of heat sink thicknesses and the interrelationship with component lead geometry, the design of heat sink geometry as related to the fabrication of the heat sinks and bonding media, and the complexities of the bonding process itself.
The Manufacture and Reliability of the EPIC Chip Carrier
Authors: Sinnadurai F.N. , Small D.J.
Published: February 2008

Following extensive studies that demonstrated that some types of plastic encapsulation can be used in high reliability environments, the EPIC chip carrier was conceived and developed as a cost‐effective micropackage for ICs. The EPIC chip carrier is manufactured by adaptations of PCB techniques with metallisation suitable for auto‐wire bonding. It is a low‐cost alternative to the ceramic chip carrier, but with a much better electrical performance, derived from lower parasitics of the materials employed. Reliability studies have confirmed the suitability of the EPIC for 20 year life operations to which an added benefit is the avoidance of TCE mismatch problems sometimes obtained with ceramic chip carriers on PCBs.
Machining Multilayer Circuit Boards
Authors: Hagge J.K. , Mather J.C.
Published: February 2008

Machining operations on multilayer circuit boards play the two major roles of establishing the finished geometry of the board and leading to the interconnection of the various conductor layers and it is likely that for some considerable time carbide cutting tools will continue to be used in the machining process. Fundamental and detailed considerations of the parameters influencing machining are presented prior to analysing the two predominant areas of use. Mention is made of some advanced machining techniques, involving mechanical, chemical and laser methods.
Creep and Fatigue Testing of Micro Solder Joints
Authors: Becker G.
Published: February 2008

Against the background of the fact that solder joints crack owing to thermal cycling, the method of predicting the lifetime of a solder joint is critically discussed. The conclusion is that the working conditions of the solder joints have to be carefully analysed and to be brought into agreement with the material properties. On the basis of experimental values, it is shown how this can be done. Creep, relaxation and fatigue of solder joints are discussed.
Some Metallurgical Studies Related to the Surface Mounting of Electronic Components
Authors: Thwaites C.J.
Published: February 2008

The introduction of high density surface mount technology may lead to a number of metallurgical problems. This paper considers two aspects which are currently being actively discussed. Firstly, incompatibility in expansion properties of the materials used and severe thermal cycling may induce creep and fatigue stresses on soldered joints, and the merits of different alloys are considered. Secondly, the necessary thermal treatments such as burn‐in and elevated service temperature can lead to intermetallic compound layer growth between the solder and the metallised layer on components which may be considered a potential source of joint strength reduction. Mention is also made of the different visual appearance of joints to chip components compared with conventional soldered joints.
Laser Drilling of Printed Circuit Boards
Authors: Watson M.N.
Published: February 2008

Many small holes need to be drilled in printed circuit boards to achieve a high packing density of circuit components. Even with NC control, conventional mechanical techniques are relatively slow and holes smaller than 035 mm diameter are difficult to achieve in production. Laser drilling has been suggested as a potentially fast technique capable of drilling small holes, so trials have been conducted on thin, flexible kapton board, and on 08 mm and 16 mm thick epoxide woven glass fabric board with 12 and 36 micron thick copper cladding. Using a 600 W CO2 laser, the proposed technique was to pre‐etch holes in the copper which would then act as a mask to the beam, so drilling only where etched holes existed. This technique was feasible on the flexible board, but not on the thicker boards because of damage to the copper. Using a pulsed Nd‐YAG laser to drill through both copper and laminate gave good results, but more work is necessary to eliminate occasional delamination of the copper around the hole. Through‐hole plating of the drilled holes appeared to present no special problems.
Machining Multilayer Circuit Boards
Authors: Hagge J.K. , Mather J.C.
Published: February 2008

Drilling is the first process step in creating a plated‐through hole (PTH). The purpose of the PTH is for electrically interconnecting two or more circuit locations and/or providing a means for electrical and mechanical connection of components to the MLCB.
Automatic Optical Inspection of Printed Circuit Boards
Authors: Doyle K.G.
Published: February 2008

An automatic optical printed circuit board inspection machine will be described which provides considerable improvements on existing methods of PCB inspection and testing. The machine can detect breaks, nicks, shorts, pinholes, inadequate track clearances, inadequate track widths and holes which are undersized, oversized, missing or not concentric with the pad. It can be used in a non‐comparison mode to detect small defects in boards or photographic negatives, and can also be used in a comparison mode to provide a complete functional test of a board similar to that provided by a bed‐of‐nails tester, but with improved detection of marginal faults. The board is optically scanned and the resulting large amounts of data are reduced by special hardware and software techniques which allow rapid throughput and virtually eliminate ‘false alarms’ caused by lettering, logos, dust specks etc. which do not affect the functionality of the board. This technique differs considerably from the ‘Feature recognition’ and the ‘Comparison’ techniques at present employed in automatic optical PCB inspection. Operation of the machine is very simple as the board does not need to be accurately positioned, and a simple ‘good/bad’ indication is provided as well as more detailed defect location information.
Economic Solvent Drying for Electronics Applications
Authors: Lambert W.
Published: February 2008

The reasons for the essential drying of electronic components are enumerated prior to a description of several drying methods currently employed in industry. A process involving drying with fluorocarbons that utilises a water displacement system is found to perform efficiently. The displacement effect is outlined and the benefits of using this system with fluorocarbon solvents are listed. Various applications exist in the electronics field for which this method proves to offer marked advantages.
Metallographic Examination of Solder Joints on Surface‐mounted Components
Authors: Steen H.
Published: February 2008

Some special characteristics of solder joints made between surface mounted electronic components and circuit boards as compared with conventional wave soldered lead‐through joints are discussed, and the types of defects to be expected are listed. Following a description of metallographic methods suitable for examining surface soldered joints, some metallographic features, both normal and defective, of solder joints between chip carriers and substrates are illustrated and discussed. The features include porosity, intermetallic phases, solder microstructure, and low cycle fatigue cracking resulting from temperature cycling.
Printed Circuit World Convention III Report
Authors: Manfield H.G.
Published: February 2008

Previous attendance records were broken this year as 1,534 delegates, representing 19 countries, gathered together for Printed Circuit World Convention III from May 22–25, 1984 in Washington, DC.
High Density Multilayer Printed Wiring Boards Using UTC as the Surface Layer
Authors: Hanabusa T. , Yamamoto K. , Yamashita M. , Takagi K.
Published: February 2008

High density packaging mounted VLSI demand highly dense and highly accurate multilayer printed wiring boards. The authors have studied Ultra Thin Copper (UTC) technology of printed wiring boards for application to the packages of high speed and high performance computers for more than 10 years. This paper describes the requirement for fine line and highly dense multilayer printed wiring boards and the study of the development of a suitable process using the UTC. The discussions include the behaviour of pattern etching and effects of plating thickness, the improvement of plating thickness uniformity, the selection of carrier types, the measurement of peel strength between copper foil and substrate, and so on. The UTC application reduces the defects caused by surface contamination of epoxy resin. Degradation of surface resistance is also discussed, which may be caused by surface creeping of alkaline ions arising from residues of plating solution within the plated‐through hole wall. These investigations could establish UTC technology for fine line printed wiring boards.
Vapour Phase Soldering of SMDs—Reliability Characteristics
Authors: Caswell G.
Published: February 2008

This paper will outline a viable, in use, production process that focuses on the utilisation of vapour phase soldering. The process will address the soldering of surface mounted devices, the repeatability of solder joint quality, and the resultant environmental characteristics of assemblies produced using the mentioned techniques. The paper will also address the field history obtained by SMD hardware produced at the author's company, to illustrate the environments into which vapour phase soldered joints can be successfully implemented.
The Nature of Insoluble Residues Formed on Printed Circuits Soldered with Rosin Fluxes
Authors: Lovering D.G.
Published: February 2008

Insoluble residues may be formed for a number of reasons as a result of flux‐solder‐conductor reactions occurring during the crucial operation of soldering, in which both metals and fluxes are molten and at elevated temperatures. The consequences can be serious, since corrosion of joints may be aggravated, coatings may not adhere or bridging between conductors may occur. One such residue, which was formed during defluxing of printed circuits with a commercial methanol‐fluorocarbon solvent, has been characterised in some detail. It appears to be a tin abiate complex which remains insoluble in most solvents except organic amides.
An Unsymmetric Metal Base PWB—Design Parameters and Thermal Considerations
Authors: Flodman G.
Published: February 2008

A new central processor for the AXE telephone switching system was developed. Using surface mounting on a metal base board a large reduction of size was obtained coupled to an improvement in electrical and thermal performance.
The Theory of Cleaning
Authors: Ellis B.N.
Published: February 2008

A theoretical treatise will be presented in two parts focusing on the mechanics, physics and chemistry of cleaning (in simple terms) of electronics components and assemblies.
The Fourth Electronic Revolution
Authors: Sage M.G.
Published: February 2008

The electronics industry is now entering a phase in its development where significant increases in the use of its products (in volume terms) will take place. This growth, triggered by performance and cost advances in ICs, will in turn have a considerable impact on the packaging and interconnection of these electronic products. This paper looks at the problems and opportunities associated with the necessary innovations in electronic packaging and interconnection and what progress is being made around the world.
Quintec Manufacturing Company, Anaheim, S. California
Authors: Cullen Lorna
Published: February 2008

Orange County, currently boasting around two million highly independent and diverse inhabitants, is wedged between the United States' third largest metropolis (Los Angeles) and its seventh ranking city (San Diego). Emerging from its conservative cocoon in 1955, the year that witnessed the advent of Disneyland, the county developed during the 1970s into one of the nation's most rapidly growing areas. Land had lain unchanged and unchallenged prior to 1955, a year that saw the opening of the Santa Ana Freeway with eight lanes connecting Orange County to Los Angeles. The county now entices 36 million tourists annually to Disneyland, Knotts Berry Farm and other sightseeing attractions, in addition to which the area's benign climate and strawberry and citrus covered hills have been discovered by thousands of new residents who have moved in, in recent years, with new industries and by sheer numbers have shattered the very tranquillity that enticed them there. These affluent newcomers enjoy a median annual family income of $40,000 and new houses in the region are marketed at an average of $200,000.
The Theory of Cleaning
Authors: Ellis B.N.
Published: February 2008

This is the second part of a theoretical treatise focusing on the mechanics, physics and chemistry of cleaning (in simple terms) of electronics components and assemblies.
Small Hole Drilling
Authors: Brösamle H.
Published: February 2008

Back taper drills, back taper drills with cylindrical tips and spade type drills were the three types available in the past for drilling multilayer boards in the diameter range of 0·8 to 1·1 mm. With packaging developments, drilling of smaller diameters, such as 0·4 mm, became necessary and care had to be taken to avoid drill breakage. The effects of board thickness, drill diameter and feed on drill breakage are analysed, followed by discussion of parameters affecting drilling accuracy and drill run‐out. The paper then deals with the effect of drill design on drill breakage, resin smear, nailheading and hole wall roughness. Results obtained using one back taper reference drill and seven other different spade type drill designs are analysed.
Design Economics of Surface Mount PCBs
Authors: Kalenik S. , Anderson B.
Published: February 2008

This paper presents an experience in designing a printed circuit board prototype as part of a general surface mount investigation for commercial electronics application. The point of view is that of a low volume assembler of relatively large, complex PC boards which use standard components. Three prototype versions were designed using different criteria. FR‐4 substrate was used for all of the designs. A comparison of the three designs with the through‐hole version indicates that the economic success of surface mounted printed circuit assemblies is heavily dependent on the physical design of the printed circuit board. Some of the aspects of a surface mounted circuit assembly that are discussed include design philosophy and tools, printed circuit board fabrication and bare board test. Design practices that would ideally utilise the small size of surface mount components are contrasted with those practices necessary to provide low cost and manufacturability of the printed circuit board.
Using Thermochemical Analysis in the Quality Control of Prepregs and Laminates for Multilayer PCB Manufacture
Authors: Smith C.A.
Published: February 2008

Differential Scanning Calorimetry (DSC) is an ideal technique for characterising polymeric materials such as the epoxy resin in epoxy glass prepregs and laminates, the technique having evolved from the older qualitative method of Differential Thermal Analysis (DTA). In DSC the heat flow to or from the sample is measured as a function of temperature or time. Epoxy glass prepregs are used as the bonding/insulating layer in multilayer printed circuit boards. When a sample of the epoxy resin in prepreg is heated, the heat flow that results from the exothermic curing reaction is measured and used to calculate the enthalpy ΔH of the reaction. ΔH is related to the degree of B stage curing and the flow achievable in the laminating press. Methods are given for calculating ΔH and the differences found in two manufacturers' prepreg material are discussed. The effect of ageing on ΔH, which has been found to decrease with time and with the extent of cure, is examined at room temperature and under refrigeration. The difference in the ageing properties of the two prepregs is explained by reference to a plot of the degree of conversion with time. This plot also enables the curing time required in the lamination press and the shelf life of the prepreg at room temperature to be calculated. Monitoring the degree of cure of laminates and cured prepreg using the glass transition temperature of the resin is examined. Insufficient cure may lead to problems of resin smear in multilayer printed circuit boards. Thermochemical analysis is used as a routine quality control method in the Microcircuit Assembly Techniques Facility at Marconi Research Centre for testing incoming prepreg and laminates used in multilayer printed circuit board manufacture.
Surface Mount Assembly in High Volume Manufacturing
Authors: Marques L.
Published: February 2008

This paper reports on the planning, introduction, and implementation of surface mount technology (SMT) for printed circuit board assembly at Convergent Technologies. It is written from the production personnel's view‐point. The report starts with a brief history of the company, describes its dynamic environment, outlines the factors that led to the decision to implement SMT and provides the time‐frame for said implementation. With this background the paper then deals at length with design and manufacturing issues and questions that arose during this undertaking. The report concludes with a summary that outlines the benefits and concerns of SMT and highlights the future trends for this technology.
LEITRON, Leiterplatten‐Electronic, GmbH & Co. KG, Schwäbisch Gmünd
Authors: Cullen Lorna
Published: February 2008

The opportunity earlier this year to gain a more complete picture of production operations at the LEITRON printed circuit board manufacturing facility in the vicinity of Schwäbisch Gmünd proved to be an enlightening, interesting and enjoyable experience. More time would have been needed to explore to advantage the town itself which dates back to the 7th century, as well as the attractively unspoilt surrounding area.
Perstorp Electronics—Industrial Laminates Division Perstorp, Sweden
Authors: Cullen Lorna
Published: February 2008

Despite the April sunshine, the landscape in southern Sweden remained devoid of fresh Spring colours—the result of a prolonged and severe Winter—when Circuit World made the visit to Perstorp earlier this year. The journey to this tranquil inland village crosses fairly flat arable land interrupted here and there by belts of forestation.
Pri‐Dana Elektronik, Hedensted, Denmark
Authors: Cullen Lorna
Published: February 2008

The Jutland peninsula is the only part of Denmark attached to the continent of Europe, its Southern boundary constituting the Danish/German frontier. About one‐tenth of the peninsula consists of moors and sand dunes, the latter found predominantly along the West coast, while the remaining nine‐tenths is devoted to agriculture and, to a lesser extent, forestry. On the East side, at intervals, picturesque wooded fjords run for miles inland.
Electrical Characteristics of Unilayer II A Discrete Wire Alternative to Multilayer PWBs
Authors: Grant J.L.
Published: February 2008

As the speed, density, power dissipation, and overall performance of semiconductor chips continue to improve, electronic equipment designers are finding that their ability to utilise new, high performance ICs is limited by the electrical performance, cost and turnaround time associated with the higher levels of packaging and interconnection. With the evolution of silicon foundries, CAD systems, logic array and standard cell technology, the designer now has the ability to develop and implement custom IC functions rapidly at a fraction of the cost and time associated with full custom IC development. The driving force for this evolution is the need for reduction of product development time and cost. As electronic product life cycles continue to decrease, so must the development time. Although the need to reduce component development times has been acted on first by the semiconductor manufacturers, suppliers of packaging and interconnection components are also feeling the need to provide customised designs rapidly and at low cost. Unilayer II is a discrete wire circuit board technology with a wiring density capability approximating that of multilayer printed wiring boards. However, since the wiring is defined in software and implemented on a numerically controlled wiring machine, the time and cost associated with development, and also with wiring changes, is greatly reduced. This paper presents the results of extensive electrical testing performed to characterise the electrical performance of the discrete wire Unilayer II transmission lines. Characteristic impedance, propagation velocity, capacitance, inductance, and crosstalk are discussed in detail.
The Importance of High Quality Electroless Copper Deposition in the Production of Plated‐through‐hole PCBs
Authors: Lea C.
Published: February 2008

For zero‐defect wave soldering of double‐sided and multilayer printed circuit boards, the copper through‐hole‐plating must be impervious to gas generated in the laminate for the period of a few seconds while the solder is molten. The kinetics of the gas evolution during soldering have been related quantitatively to the integrity of the plated copper. This in turn is related to the quality of the electroless copper (evaluated using the backlighting test), the nature and distribution of the catalyst (evaluated using X‐ray photoelectron spectroscopy) and the methods and effectiveness of the hole‐wall preparation (evaluated using scanning electron microscopy). The relevance of laboratory measurements has been confirmed on a wide range of industrial production plating lines.
True Temperature Measurement of Electronic Components Using Infra‐red Thermography
Authors: Kallis J.M. , Samuels A.H. , Stout R.P.
Published: February 2008

Great savings can be achieved by detecting and isolating design problems early in an electronic programme. Many design problems, including electrical overstress, poor thermal design and circuit layout problems, are detectable by their infrared (I‐R) signature. A reliability and design improvement tool utilising current I‐R scanning technology has been developed. Specifically, an I‐R scanning method for making accurate temperature measurements for the purpose of electronic design reliability improvement and qualification has been developed and verified experimentally. Field‐actual conditions, in which radiative and convective heat losses from the components are negligible, are simulated with a thermally insulating enclosure. The enclosure is designed for rapid removal just before the scan, obviating the need for exotic materials that are transparent to I‐R in the scanner's passband. With typical hardware thermal lags, the method allows determination of true temperatures simulating field conditions. Corrections for unwanted scanner‐produced radiation and for the target emissivity are made with a three‐scan method and specially designed apparatus. An integral part of this apparatus is the aforementioned quickly removable thermal enclosure. The three scans take approximately an hour for a typical circuit board after initial set‐up time. True‐temperature measurements of circuit boards can be made with the I‐R design improvement tool now.
On the Utility of Insulation Resistance Tests to Assess the Life Performance of Printed Wiring Boards
Authors: Eisenmann E.T.
Published: February 2008

Based on new data insulation resistance tests have little capacity to predict the life performance of double‐sided rigid printed wiring boards. This conclusion arises from an elaborate insulation resistance evaluation after 2300 hours of accelerated life testing. The study considers the effects of two sources of contamination and five material combinations on the initial insulation resistance at 23°C and 90% RH. Life test samples were exposed to four levels of humidity and three levels of temperature. Using 1 Megohm as failure criterion there are clear‐cut effects of humidity, temperature and material combination, but there is only a weak correlation between failures and the initial insulation resistance.
Blowholes in PCB Soldering Their Causes and Cures
Authors: Turnbull R.B.
Published: February 2008

A blowhole is a defect in a soldered joint on a printed circuit assembly which incorporates plated through‐hole circuitry. Blowholes are caused by volatiles being generated in the through‐hole during the soldering process and it is often thought that these volatiles originate from the flux. Examination of the problem shows this not to be the case; the most likely cause is bad drilling of the hole and/or poor plating. The construction of the glass fabric used in laminate manufacture may be a contributory factor to bad drilling. The incidence of blowholes can often be reduced by baking the boards immediately prior to soldering. If this treatment is successful in reducing blowholes, it merely confirms that the problem is inherent in the boards themselves and not in the soldering process.
Prepreg Testing—Quick, Informative, Reliable A Critical View
Authors: Schiffer W.
Published: February 2008

This paper is a critical comparison of the currently used methods to test prepregs which do not describe to a sufficient extent the flow behaviour of a prepreg resin during the pressing process. The new test method introduced herein is a characterisation of the viscosity of the resin melt. International standardisation of this test method is recommended.
The Offset Printing Method of Inner Layers—One of the Improved Methods for PCB Manufacturing Technology
Authors: Toushinsky A. , Evjenko V.
Published: February 2008

The paper describes an offset printing method for the production of inner layers based on an automatic laser engraving machine. The operation of the machine is outlined; characteristics of the various pattern generation methods for PCB inner layers are compared before a final summary of the advantages of the offset printing method is given.
Predicting Reliability of LSI Printed Circuit Carriers
Authors: Tomaine J.J.
Published: February 2008

The arrival of Large Scale Integration (LSI) devices forced the development of products which could reliably package these high density chip carriers. Until LSI, printed circuit technology designers were only moderately challenged to make high density products. This change occurred in the early 1970s at IBM with the printed circuit packaging for the IBM 4300 models. This was the first system application of LSI chip carriers. Since then, numerous LSI printed circuit carrier designs have been used in IBM systems. The methods to predict reliability of the LSI printed circuit carriers have not kept up with the hardware technology. This paper will describe an enhanced method of prediction which more closely represents the performance of today's LSI printed circuit cards and mother boards. Computer processed algorithms will be used to estimate the failure rates of a particular printed circuit carrier and the effects of this estimate on the complete system will be discussed. The estimation algorithms are contained in programmes resident on floppy diskettes and run on an IBM Personal Computer. The flexibility and ease of use of the PC allows the user to make any necessary additions or changes to the algorithms quickly. The algorithms are derived from standard Weibull reliability techniques but include internally derived factors which enhance the accuracy of the Weibull predictions. Data from extensive field reporting of any defects and detailed failure analysis are used to enhance the accuracy of the algorithms. Using the enhanced algorithms, one can generate new estimates easily. Quick access and fast turnaround times result in a convenient and cost effective technique to provide these estimates to system users on a timely basis. Design changes to the carrier which could affect the reliability are quickly modelled in the algorithms and new reliability estimates are provided allowing the final user to make the required system trade‐offs easily. These design changes and new reliability projections can be presented to management in a timely manner and allow them to make the cost/performance decisions which result in the optimum marketable product.
Use of Thermoplastics and Injection Moulded PWBs
Authors: Frisch D. , Cleveland E.
Published: February 2008

Moulded substrates offer a wide spectrum of performance at economical prices, featuring enhanced electrical, physical and environmental properties. By expanding interconnection into a third dimension by providing connectivity between or along non‐planar surfaces or planes, moulded boards allow designers the freedom to be highly creative in devising circuitry comprising complex shapes or forms of unique sculpture. Opportunities abound for achieving cost reductions, savings being achieved first through eliminating processing steps in PCB fabrication and secondly by simplifying or minimising sub‐assembly or final assembly labour or hardware costs. In addition, further savings can be achieved by incorporating attachment joining techniques like ultrasonic welding. Discussion covers the characteristics of moulded substrates, metallisation of unclad substrates using the additive process, and several applications of moulded circuitry and 3‐D assemblies, before a prediction of the future potential for this technology.
Surface Mount Technology for High Reliability Telecoms Applications
Authors: Taylor K.
Published: February 2008

The technology of printed circuit boards suitable for surface mount assembly is discussed with reference to solder mount tolerances and board finishing. Some design features which aid the production of reliable assemblies are described. The importance of preconditioning surface mount components with the soldering conditions to be utilised during the assembly process is emphasised. Some data which show the suitability of both SOIC and small PLCC packaged components, which have been vapour phase reflow soldered, are given. The reliability for long‐life applications of surface mount components and assemblies has not been demonstrated in general as yet and all manufacturers of such assemblies must validate their own assembly methods and components.
Flexible Circuit Materials for Use as Interconnections in High Speed Digital Systems
Authors: Gazit S.
Published: February 2008

The increasing use of high switching speed systems in both microwave electronics and high speed logic devices has created the need for printed circuit boards which are based on low dielectric constant and low loss materials. In addition, these circuit materials must be capable of withstanding elevated temperatures typical of hostile service environments and of board fabrication processes. Such low dielectric constant rigid boards are commercially available from a few sources. However, there is a growing demand for low dielectric constant flexible printed circuit boards for interconnecting rigid boards or in rigid/flex applications where high speed, fast rise times, controlled impedance and low crosstalk are important. A new family of thin laminates which are suitable for fabrication of flexible low dielectric constant printed circuit boards have been developed by Rogers Corporation. These circuit materials are called ROhyphen;2500 laminates and offer flexible interconnections in high speed electronic systems. RO‐2500 circuit materials are based on microglass reinforced fluorocarbon composites and have a typical dielectric constant of 25. The transmission line properties of these materials have been evaluated by the IPC‐FC‐201 test method. The results indicated that these circuit materials improve the propagation velocity by about 10% and the rise time by about 30% when compared with the same geometry, polyimide film based, flexible PCs in stripline constructions. Also, dimensional stability of these laminates after etch and heat ageing is improved over that of the standard flex circuit materials based on polyimide film. RO‐2500 laminate properties have been evaluated by the IPC‐TM‐650 test methods, which are widely accepted by the flexible PCB industry.
Designing for Zero‐defect Soldering
Authors: Weinhold M.
Published: February 2008

This paper describes how PCB designers must adjust their approach to take into account the new requirements for the production of high technology printed circuit boards using the latest plated‐through hole and surface mounting techniques. It also describes how the correct use of dry film solder masks is contributing towards the achievement of zero‐defect soldering.
Influence of Substrate Thickness and Preheat Treatment on the Adhesion and Dimensional Stability of Polyacrylate‐based Photoresist Lamination in Printed Circuit Fabrication
Authors: Kong E.S.W.
Published: February 2008

During fuser‐roll resist lamination processes, the copper‐clad FR‐4 substrate surface temperature was found to be inversely proportional to the substrate thickness. This temperature fluctuation has resulted in changes of adhesive forces in the copper/resist interface which in turn can affect the yield in the printed circuit manufacturing processes. By using infra‐red preheat treatment on the substrate prior to fuser‐roll lamination, the adhesion was found to be improved in the copper/resist interface. This adhesion improvement was found to be reflected in yield increase in fine line printed circuit fabrication.
Blowholing in PTH Solder Fillets
Authors: Howie F.H. , Lea C.
Published: February 2008

This paper is the second of a series dealing with the blowholing problem on through‐hole plated printed circuit boards. In the previous paper the authors have considered the impact of the problem on the UK electronics assembly industry. Here they consider the nature of the gas causing blowholes and voids, its origin and the kinetics of its generation and evolution. When a printed circuit board with plated‐through‐holes is wave soldered, the thermal spike of the molten solder activates the evolution of gas, sometimes in relatively enormous quantities. The gas is seen bubbling from the surface of the molten solder in the joint. Upon freezing, the solder either traps the gas in a void enclosed within the fillet or, if the gas is escaping from the surface as freezing occurs, forms a blowhole.
Statistics, Designed Experiments and Printed Wiring Board Assembly
Authors: Lichtenberg L.R. , Sleiman M. , Harry M.J.
Published: February 2008

During the past few years, statistical process control and experiment design concepts have taken a prominent place within the industry. The use of such tools within the Motorola, GEG manufacturing environment, has grown to the point where reflow and wave solder process development and optimisation has significantly benefited. The ability to evaluate statistically and model various known and unknown phenomena has provided GEG's manufacturing technology with a series of very powerful tools to aid in process control and development. The primary purpose of this paper is to present the various approaches used by GEG to implement the previously mentioned statistical tools, with respect to the development of infra‐red (I‐R) reflow solder processes and enhancement of certain quality characteristics associated with wave soldered printed wiring boards (PWBs). Beyond specific GEG applications, the paper discusses the role of statistically designed experiments and process control methods as a vehicle for providing answers to complex manufacturing problems. In addition, a discussion of the mathematical and graphical methods underlying the interpretation of quantitative data is presented. Perhaps the most important benefit derived from the use of statistics to solve manufacturing and quality problems is related to decision making. When experiments are conducted to isolate unwanted sources of process and product variation, decisions must be made to determine whether or not certain experimental effects are important. Through the application of statistics, the researcher can ascertain the mathematical probability associated with the random chance occurrence of various experimental effects. With this knowledge, the researcher can make decisions with known degrees of risk and confidence. Without such knowledge, an organisation might possibly expend valuable resources and derive no direct benefit. Ultimately, the principal reason for applying statistical methods and procedures is to increase quality and yield, while simultaneously reducing costs.