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Article
Publication date: 1 March 1991

J.L. Marshall, J. Calderon and J. Sees

A mechanical and microstructural study was performed of 43/43/14 tin/lead/bismuth solder. This alloy melts lower than the commonly used tin/lead solders and therefore…

Abstract

A mechanical and microstructural study was performed of 43/43/14 tin/lead/bismuth solder. This alloy melts lower than the commonly used tin/lead solders and therefore holds promise as a useful material in two‐step soldering processes or in processes with thermally sensitive components. Mechanical testing of 43/43/14 tin/lead/bismuth showed a strength comparable to that of tin/lead solders but increased creep rate. Microstructural analysis (scanning electron microscopy/energy dispersive X‐ray) exhibited the same mechanism of fatigue as for tin/lead solders, viz., heterogeneous coarsening. Thermocyclic fatigue demonstrated that the long‐term reliability of 43/43/14 tin/lead/bismuth is comparable to that of tin/lead solders.

Details

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

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Article
Publication date: 1 March 1989

M. Kucera

Nickel, as a barrier to the dissolution of termination materials, requires a solderable coating to prevent nickel oxidation and preserve solderability of surface mount…

Abstract

Nickel, as a barrier to the dissolution of termination materials, requires a solderable coating to prevent nickel oxidation and preserve solderability of surface mount devices. Most multilayer capacitors (MLCs) are supplied with tin or tin/lead coatings electrodeposited over the nickel barrier layer. There is general disagreement in the electronics industry about preferred solderable finishes and solderability test methods of component leads. Tin and tin/lead finishes have typically been compared on leaded devices. The results of these studies are not necessarily applicable to leadless surface mount chip components. This study compares 100% tin and 60/40 tin/lead electroplated coatings on nickel barrier terminated, multilayer chip capacitors (MLCs). Various thicknesses of tin and tin/lead were compared for solderability after steam‐age, solder joint strength, and chemical and physical composition of the reflowed termination surface. The results show no significant difference between the solderability and joint strength under vapour phase reflow conditions using 60/40 solder paste. The termination surfaces were reflowed at 215°C in the case of both pure tin and 60/40 tin/lead. The tin/lead finish reflowed to a composition of 60% tin/40% lead. The 100% tin finish reflowed to a composition of 90% tin/10% lead. Reflow was caused by diffusion of lead and tin.

Details

Microelectronics International, vol. 6 no. 3
Type: Research Article
ISSN: 1356-5362

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Article
Publication date: 1 January 1977

M.L. Ackroyd and C.A. MacKay

In the production of printed circuit assemblies, the demand for higher reliability levels has increased over the years. In order to achieve a high level of soldering…

Abstract

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

Details

Circuit World, vol. 3 no. 2
Type: Research Article
ISSN: 0305-6120

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Article
Publication date: 1 January 1974

R. Williams

The increase in printed wiring boards exhibiting de‐wetting characteristics after the fusing of electroplated tin/lead coatings prompted this investigation. Although it…

Abstract

The increase in printed wiring boards exhibiting de‐wetting characteristics after the fusing of electroplated tin/lead coatings prompted this investigation. Although it became clear during the course of the investigation that the development of the resist was a contributing factor to de‐wetting, it was shown that the sulphate ion concentration of the final rinse before tin/lead plating was the major cause of de‐wetting.

Details

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

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Article
Publication date: 1 June 2005

Girish S. Wable, Quyen Chu, Purushothaman Damodaran and Krishnaswami Srihari

Historically, tin‐lead solder has been a commonly used joining material in electronics manufacturing. Environmental and health concerns, due to the leaching of lead from…

Abstract

Purpose

Historically, tin‐lead solder has been a commonly used joining material in electronics manufacturing. Environmental and health concerns, due to the leaching of lead from landfills into ground water, have necessitated legislation that restricts the use of lead in electronics. The transition from tin‐lead solder to a lead‐free solder composition is imminent. Several alternative solder alloys (and their fluxes) have been researched for electronics assembly in the last few years. The objective of this research was to develop a systematic selection process for choosing a “preferred” lead‐free solder paste, based on its print and reflow performance.

Design/methodology/approach

After a detailed study of industry preferences, published experimental data, and recommendations of various industrial consortia, a near eutectic tin‐silver‐copper (SAC) composition was selected as the preferred alloy for evaluation. Commercially available SAC solder pastes with a no‐clean chemistry were extensively investigated in a simulated manufacturing environment. A total of nine SAC pastes from seven manufacturers were evaluated in this investigation. A eutectic Sn/Pb solder paste was used as a baseline for comparison. While selecting the best lead‐free paste, it was noted that the selected paste has to perform as good as, if not better than, the current tin‐lead paste configuration used in electronics manufacturing for a particular application. The quality of the solder pastes was characterized by a series of analytical and assembly process tests consisting of, but not limited to, a printability test, a solder ball test, a slump test, and post reflow characteristics such as the tendency to form voids, self‐centring and wetting ability.

Findings

Each paste was evaluated for desirable and undesirable properties. The pastes were then scored relative to each other in each individual test. An aggregate of individual test scores determined the best paste.

Originality/value

This paper summarizes a systematic approach adopted to evaluate lead‐free solder pastes for extreme reflow profiles expected to be observed in reflow soldering lead‐free boards.

Details

Soldering & Surface Mount Technology, vol. 17 no. 2
Type: Research Article
ISSN: 0954-0911

Keywords

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Article
Publication date: 1 October 2006

Todd Castello, Dan Rooney and Dongkai Shangguan

This paper aims to describe and document the application of commonly utilized solder joint failure analysis techniques to lead‐free solder joints.

Abstract

Purpose

This paper aims to describe and document the application of commonly utilized solder joint failure analysis techniques to lead‐free solder joints.

Design/methodology/approach

Traditional failure analysis techniques, including visual inspection, X‐ray radiography, mechanical strength testing, dye and pry, metallography, microscopy and photomicrography, are reviewed. These techniques are demonstrated as applied to lead‐free and tin lead solder joints. Common failure modes observed in lead‐free and tin lead solder joints are described and compared.

Findings

It is shown that the traditional failure analysis techniques previously utilized for tin lead solder joints are widely applicable to the analysis of lead‐free solder joints. The changes required to effectively apply these techniques to the analysis of lead‐free solder joints are described.

Originality/value

This paper will be instrumental to the process, quality, reliability and failure analysis engineering disciplines in furthering understanding of the application of failure analysis techniques of both tin lead and lead‐free solder joints.

Details

Soldering & Surface Mount Technology, vol. 18 no. 4
Type: Research Article
ISSN: 0954-0911

Keywords

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Article
Publication date: 1 March 1988

D.A. Luke

To permit multilayer ceramic capacitors to be soldered directly onto printed circuit boards and other components, the terminations are plated with a barrier layer (usually…

Abstract

To permit multilayer ceramic capacitors to be soldered directly onto printed circuit boards and other components, the terminations are plated with a barrier layer (usually nickel) followed by either pure tin or a tin‐lead alloy. Pertinent properties of deposits and solutions are discussed and these include deposit thickness requirements, internal stress, solderability, effects of cross‐contamination, variations of tin‐lead composition with operating parameters and effluent treatment.

Details

Microelectronics International, vol. 5 no. 3
Type: Research Article
ISSN: 1356-5362

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Article
Publication date: 1 August 2002

Sami Tapani Nurmi and Eero Olavi Ristolainen

This paper will describe tests of the interconnect reliability of BGA components with tin‐lead bumps soldered with lead‐free solder paste during temperature cycling…

Abstract

This paper will describe tests of the interconnect reliability of BGA components with tin‐lead bumps soldered with lead‐free solder paste during temperature cycling. Tin‐lead BGA components soldered with tin‐lead solder paste and lead‐free BGA components soldered with lead‐free solder paste were used as a reference. The lead‐free solder used was eutectic tin‐silver‐copper. Two kinds of surface finishes were used on the printed circuit boards (PCB), an immersion gold over electroless nickel and an organic solderability preservative. The test PCBs were temperature‐cycled for 2500 cycles in the range of −40°C to +125°C and they were continuously electrically monitored during the cycling. The results of the temperature cycling test showed that lead‐ containing BGA components soldered with lead‐free solder paste don't show any serious reliability risks and can actually withstand temperature cycling stresses better than entirely lead‐free BGA assemblies.

Details

Soldering & Surface Mount Technology, vol. 14 no. 2
Type: Research Article
ISSN: 0954-0911

Keywords

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Article
Publication date: 1 April 1992

E.C. Couble, O.B. Dutkewych, S.M. Florio, M.V. Marsh and R.F. Staniunas

The technological development and characteristics of an innovative process and composition for immersion plating and fusing of a solderable tin/lead deposit over copper…

Abstract

The technological development and characteristics of an innovative process and composition for immersion plating and fusing of a solderable tin/lead deposit over copper are discussed. The process offers a viable alternative to hot air solder levelling, electrodeposition/selective stripping, or inhibitor coatings for maintaining solderability of printed wiring boards. A flat, uniform solderable tin/lead coating on all feature surfaces and edges is achieved. A number of important benefits are derived. The ability to coat any copper surface uniformly, including fine pitch features, is substantially enhanced. Solderability is improved because of a thick, flat, co‐planar and uniform tin/lead deposit on all copper surfaces. Typical thickness and composition of the fused alloy are 150 to 300 microinches (4 to 8 microns) and 65 to 75% tin.

Details

Circuit World, vol. 19 no. 1
Type: Research Article
ISSN: 0305-6120

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Article
Publication date: 1 March 1989

D.A. Luke

Alloys deposited from plating solutions vary in composition with changes in solution constituents and processing parameters. With the increasing demand on miniaturisation…

Abstract

Alloys deposited from plating solutions vary in composition with changes in solution constituents and processing parameters. With the increasing demand on miniaturisation and quality of subsequent solder joints made to plated tin‐lead alloys, it is important to ensure stable deposit composition and also to know to what extent changes in operating conditions will affect the composition. This paper examines the major causes of changes in composition of deposits plated from solutions based on fluoboric acid and organic sulphonic acid. The methods available for measuring the deposit composition are also discussed.

Details

Circuit World, vol. 15 no. 4
Type: Research Article
ISSN: 0305-6120

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