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Article
Publication date: 1 December 1999

Bernhard Wessling

As an alternative to hot air levelling, a fundamentally new surface finish chemistry and process for solderability preservation of printed circuit boards is described: a…

Abstract

As an alternative to hot air levelling, a fundamentally new surface finish chemistry and process for solderability preservation of printed circuit boards is described: a pretreatment of the copper followed by an optimized formulation of an immersion tin. The precise and reproducible surface finish formation offers reliable solderability, economic and technical advantages for all kinds of PCBs, even for those with the most modern miniaturized structures. The deposition chemistry and ageing properties of the new Organic Metal/tin surface is discussed, based on electrochemical, wet chemical and electron microscopy studies. The results culminate in an almost complete basic understanding of the tin chemistry and the surface finish performance.

Details

Circuit World, vol. 25 no. 4
Type: Research Article
ISSN: 0305-6120

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Article
Publication date: 1 March 1999

Paul T. Vianco

An overview has been presented on the topic of alternative surface finishes for package I/Os and circuit board features. Aspects of processability and solder joint…

Abstract

An overview has been presented on the topic of alternative surface finishes for package I/Os and circuit board features. Aspects of processability and solder joint reliability were described for the following coatings: baseline hot‐dipped, plated, and plated‐and‐fused 100Sn and Sn‐Pb coatings; Ni/Au; Pd, Ni/Pd, and Ni/Pd/Au finishes; and the recently marketed immersion Ag coatings. The Ni/Au coatings appear to provide the all‐around best options in terms of solderability protection and wire bondability. Nickel/Pd finishes offer a slightly reduced level of performance in these areas which is most likely due to variable Pd surface conditions. It is necessary to minimize dissolved Au or Pd contents in the solder material to prevent solder joint embrittlement. Ancillary aspects that include thickness measurement techniques; the importance of finish compatibility with conformal coatings and conductive adhesives; and the need for alternative finishes for the processing of non‐Pb bearing solders are discussed.

Details

Circuit World, vol. 25 no. 1
Type: Research Article
ISSN: 0305-6120

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Article
Publication date: 1 April 1982

Americus

Polymer Structure. A number of articles describe basic research on polymers of interest to the paint industry. Thus Sperling [Journal of Polymer Science, Macromolecular

Abstract

Polymer Structure. A number of articles describe basic research on polymers of interest to the paint industry. Thus Sperling [Journal of Polymer Science, Macromolecular Reviews, 12 (1977) p. 141] describes interpenetrating polymer networks as structures which result when a crosslinked polymer is swelled by a monomer which contains also a crosslinking or polymerising agent. The monomer is thus polymerised in situ, presumably in the voids and intersticies provided by the initial crosslinked polymer. In this way, Sperling describes the morphology and mechanical properties of interpenetrating polymer networks.

Details

Pigment & Resin Technology, vol. 11 no. 4
Type: Research Article
ISSN: 0369-9420

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Article
Publication date: 1 January 2006

Gary Brist and Don Cullen

To examine the impact of oxide and oxide alternative processes on signal loss in commercial RF applications.

Abstract

Purpose

To examine the impact of oxide and oxide alternative processes on signal loss in commercial RF applications.

Design/methodology/approach

Stripline conductors were formed using traditional oxide, oxide dissolution/reduction, and oxide alternative processes. Conductor geometry was measured and surface topography was characterized. Effective dielectric constants and characteristic impedance for each system was determined. Finally, line loss for each treatment and rework condition was charted to nearly 20 GHz. Electrical measurements were performed by taking S‐parameter measurements through 20 GHz using an agilent vector network analyzer (VNA).

Findings

The methods employed were sufficient to statistically characterize the increased loss associated with thick oxides and high‐microetch oxide alternatives. Lower etch oxide alternatives yielded benefits for signal integrity. Of importance, rework procedures gave unacceptable increases in line loss. Overall, however, the loss due to innerlayer bonding processes was not of sufficient magnitude to elevate oxides as a primary contributor to conductor loss. For the relative simple, high production system employing epoxy substrate, oxide loss was found to be far less than substrate effects, imaging quality, and foil treatment.

Originality/value

Electrical engineers and printed circuit board (PCB) designers strive to focus their efforts on improving the PCB processes leading to maximum conductor loss in the electronic system. This work shows that oxide treatments are not a primary factor in affecting loss. Significant improvements in signal integrity may be achieved, however, with the use of low‐etch oxide alternatives and with restrictions on oxide rework. In addition, this paper allowed for new interpretations of VNA data for better modeling of PCB system data using non‐classical analysis.

Details

Circuit World, vol. 32 no. 1
Type: Research Article
ISSN: 0305-6120

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Article
Publication date: 1 March 1963

E.R. BRAITHWAITE and G.W. ROWE

LONG before man learnt to make fire by the friction of wood, he experienced the burden of friction in dragging home his kill. Perhaps it is not too fanciful to suppose…

Abstract

LONG before man learnt to make fire by the friction of wood, he experienced the burden of friction in dragging home his kill. Perhaps it is not too fanciful to suppose that the torn sides of his beast gave the first solid lubricant. Blood and mutton fat were seriously recommended as lubricants for church bell trunnions as recently as the 17th century. Indoed we still reckon fatty acids the best of all boundary lubricants. The range of man's activities has increased enormously in the present century, and particularly in the last few decades. Men have circled the earth in space; a space ship is on its way to examine another planet; terrestrial man is boring to the bottom of the earth's crust; others have descended to the depths of the ocean, and oven established a home on the floor of the Mediterranean, Speeds have increased by factors of thousands, temperatures range from near absolute zero to thousands of degrees; and a new environment of high‐intensity nuclear radiation has been created. Still, objects must move over and along each other in these exotic conditions; and to a large extent solid lubricants can provide the answer to the frictional problems.

Details

Industrial Lubrication and Tribology, vol. 15 no. 3
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 1 January 1985

M. Bakszt

Protective cover coating of bare copper boards is necessary to resist long‐term storage. Both water‐soluble and rosin‐based fluxes are used in the evaluation. The…

Abstract

Protective cover coating of bare copper boards is necessary to resist long‐term storage. Both water‐soluble and rosin‐based fluxes are used in the evaluation. The inhibitors have been practically tested on coupons which were soldered after accelerated ageing tests. All investigations were carried out with respect to the impact on waste treatment, and the adjustment to various fluxes.

Details

Circuit World, vol. 11 no. 2
Type: Research Article
ISSN: 0305-6120

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Article
Publication date: 1 December 1999

Paul Harris

A variety of lead‐free solders are now commercially available. Of those suitable for mass soldering perhaps the ones closest to a direct, drop‐in, replacement for tin‐lead…

Abstract

A variety of lead‐free solders are now commercially available. Of those suitable for mass soldering perhaps the ones closest to a direct, drop‐in, replacement for tin‐lead are the tin‐zinc‐bismuth alloys. For most tin‐based solders it is the tin which is the active element and dominates the all‐important interfacial reactions. As a result they have many properties in common. The addition of zinc, however, radically alters this picture. Zinc oxidation products are formed at the surfaces. Zinc intermetallic compounds are also formed in preference to tin‐compounds at the substrate interfaces. The nature and implications of these changes are outlined for the common basis materials.

Details

Soldering & Surface Mount Technology, vol. 11 no. 3
Type: Research Article
ISSN: 0954-0911

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Article
Publication date: 1 June 2002

Kim Clay, Ian Gardner, Eric Bresler, Mike Seal and Stuart Speakman

The industry standard for applying the identification nomenclature to Printed Circuit Boards (PCBs) is silkscreen legend printing, using white ink. This multi‐step process…

Abstract

The industry standard for applying the identification nomenclature to Printed Circuit Boards (PCBs) is silkscreen legend printing, using white ink. This multi‐step process has minimal flexibility for applying unique legends e.g. serialization numbers to individual boards. This paper describes a new, alternative single step direct legend printing system which uses piezoelectric inkjet technology, the leading digital imaging method for a variety of industrial applications. The advantages that this, inherently clean and efficient, drop‐on‐demand, printing process brings to legend printing include increased flexibility, shorter process times, good legend definition, accurate placement, small footprint equipment and reduced labour and material usage.

Details

Circuit World, vol. 28 no. 2
Type: Research Article
ISSN: 0305-6120

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Article
Publication date: 27 July 2012

A. Safdar, H.Z. He, Liu‐Ying Wei, A. Snis and Luis E. Chavez de Paz

Ti‐6Al‐4V is one of the most attractive materials being used in aerospace, automotive and medical implant industries. Electron beam melting (EBM) is one of the direct…

Abstract

Purpose

Ti‐6Al‐4V is one of the most attractive materials being used in aerospace, automotive and medical implant industries. Electron beam melting (EBM) is one of the direct digital manufacturing methods to produce complex geometries of fully dense and near net shape parts. The EBM system provides an opportunity to built metallic objects with different processing parameter settings like beam current, scan speed, probe size on powder, etc. The purpose of this paper is to determine and understand the effect of part's thickness and variation in process parameter settings of the EBM system on surface roughness/topography of EBM fabricated Ti‐6Al‐4V metallic parts.

Design/methodology/approach

A mathematical model based upon response surface methodology (RSM) is developed to study the variation of surface roughness with changing process parameter settings. Surface roughness of the test slabs produced with different parameter settings and thickness has been studied under confocal microscope. Response surface methodology was used to develop a multiple regression model to correlate the effect of variation in EBM process parameters settings and thickness of parts on surface roughness of EBM produced Ti‐6Al‐4V.

Findings

It has been observed that every part produced by EBM system has detectable surface roughness. The surface roughness parameter Ra varies between 1‐20 μm for different samples depending upon the process parameter setting and thickness. The Ra value increases with increasing sample thickness and beam current, and decreases with increase in offset focus and scan speed.

Originality/value

Surface roughness is related to wear and friction property of the material and hence is related to the life time and performance of the part. Surface roughness is an important property of any material to be considered as biomaterial. The surface roughness of the material depends upon the manufacturing method and environment and hence it is controllable either during fabrication or by post processing. From the 1st order regression model developed in this study, it is also evident that sample thickness, scan speed and beam current have relatively more effect on roughness value then the offset focus. With the model obtained equation, a designer can subsequently select the best combination of sample thickness and process parameter values to achieve desired surface roughness.

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Article
Publication date: 18 April 2017

Yang Guo, Huseini S. Patanwala, Brice Bognet and Anson W.K. Ma

This paper aims to summarize the latest developments both in terms of theoretical understanding and experimental techniques related to inkjet fluids. The purpose is to…

Abstract

Purpose

This paper aims to summarize the latest developments both in terms of theoretical understanding and experimental techniques related to inkjet fluids. The purpose is to provide practitioners a self-contained review of how the performance of inkjet and inkjet-based three-dimensional (3D) printing is fundamentally influenced by the properties of inkjet fluids.

Design/methodology/approach

This paper is written for practitioners who may not be familiar with the underlying physics of inkjet printing. The paper thus begins with a brief review of basic concepts in inkjet fluid characterization and the relevant dimensionless groups. Then, how drop impact and contact angle affect the footprint and resolution of inkjet printing is reviewed, especially onto powder and fabrics that are relevant to 3D printing and flexible electronics applications. A future outlook is given at the end of this review paper.

Findings

The jettability of Newtonian fluids is well-studied and has been generalized using a dimensionless Ohnesorge number. However, the inclusion of various functional materials may modify the ink fluid properties, leading to non-Newtonian behavior, such as shear thinning and elasticity. This paper discusses the current understanding of common inkjet fluids, such as particle suspensions, shear-thinning fluids and viscoelastic fluids.

Originality/value

A number of excellent review papers on the applications of inkjet and inkjet-based 3D printing already exist. This paper focuses on highlighting the current scientific understanding and possible future directions.

Details

Rapid Prototyping Journal, vol. 23 no. 3
Type: Research Article
ISSN: 1355-2546

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