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Article
Publication date: 1 April 2004

Timo Liukkonen, Pekka Nummenpää and Aulis Tuominen

The electronics industry will implement lead‐free soldering in the near future. Lead‐free implementation steps are divided into lead‐free process and lead‐free product…

Abstract

The electronics industry will implement lead‐free soldering in the near future. Lead‐free implementation steps are divided into lead‐free process and lead‐free product. The eutectic Sn/Ag/Cu alloy seems to have become the most widely used alloy in the implementation of lead‐free processes. In this study, the requirements for component placement are discussed from the lead‐free process point of view. Experiments concerning the self‐alignment capability and tack strength of both tin‐lead and lead‐free solder pastes are presented. According to the results, a bigger variation in self‐alignment capabilities can be expected when using a lead‐free paste. The paste properties affecting the self‐alignment mechanism and tack strength are also discussed.

Details

Soldering & Surface Mount Technology, vol. 16 no. 1
Type: Research Article
ISSN: 0954-0911

Keywords

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

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.

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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

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

Article
Publication date: 7 February 2020

Min Wu and Bailin Lv

Viscosity is an important basic physical property of liquid solders. However, because of the very complex nonlinear relationship between the viscosity of the liquid…

Abstract

Purpose

Viscosity is an important basic physical property of liquid solders. However, because of the very complex nonlinear relationship between the viscosity of the liquid ternary Sn-based lead-free solder and its determinants, a theoretical model for the viscosity of the liquid Sn-based solder alloy has not been proposed. This paper aims to address the viscosity issues that must be considered when developing new lead-free solders.

Design/methodology/approach

A BP neural network model was established to predict the viscosity of the liquid alloy and the predicted values were compared with the corresponding experimental data in the literature data. At the same time, the BP neural network model is compared with the existing theoretical model. In addition, a mathematical model for estimating the melt viscosity of ternary tin-based lead-free solders was constructed using a polynomial fitting method.

Findings

A reasonable BP neural network model was established to predict the melt viscosity of ternary tin-based lead-free solders. The viscosity prediction of the BP neural network agrees well with the experimental results. Compared to the Seetharaman and the Moelwyn–Hughes models, the BP neural network model can predict the viscosity of liquid alloys without the need to calculate the relevant thermodynamic parameters. In addition, a simple equation for estimating the melt viscosity of a ternary tin-based lead-free solder has been proposed.

Originality/value

The study identified nine factors that affect the melt viscosity of ternary tin-based lead-free solders and used these factors as input parameters for BP neural network models. The BP neural network model is more convenient because it does not require the calculation of relevant thermodynamic parameters. In addition, a mathematical model for estimating the viscosity of a ternary Sn-based lead-free solder alloy has been proposed. The overall research shows that the BP neural network model can be well applied to the theoretical study of the viscosity of liquid solder alloys. Using a constructed BP neural network to predict the viscosity of a lead-free solder melt helps to study the liquid physical properties of lead-free solders that are widely used in electronic information.

Details

Soldering & Surface Mount Technology, vol. 32 no. 3
Type: Research Article
ISSN: 0954-0911

Keywords

Article
Publication date: 1 July 2006

Richard Ciocci and Michael Pecht

The purpose of this paper is to characterize the motivations used into migrating to lead‐free solder by providing examples and directions for those making the material change.

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Abstract

Purpose

The purpose of this paper is to characterize the motivations used into migrating to lead‐free solder by providing examples and directions for those making the material change.

Design/methodology/approach

This work achieves its objective of identifying which electronic industry actions towards lead‐free soldering have been successful and why. The research reported the various motivating factors considered in adopting lead‐free electronics. To that end, the authors researched industry literature and discussed approaches with various companies and agencies. The scope of this paper is largely the board‐component level soldering process and companies involved in the international electronics industry.

Findings

The motivation to migrate to lead‐free solder has been and continues to be multi‐faceted. Issues include regulatory, commercial, and technical. Processing with lead‐free solder is successful, so the electronics industry's move towards environmentally compatible processes will meet regulated dates for change.

Practical implications

A company can learn how to incorporate environmental improvement principles resulting from the migration to lead‐free solder. Using that migration as a case study, the company can realize additional benefits by applying these principles to other product lines. Those interested in developing environmentally friendly products and processes can adopt the lessons that this paper identifies. Incorporation of lead‐free techniques, rather than resistance to change, is the result of adopting the lessons.

Originality/value

The paper presents a synopsis of the electronic industry's migration to lead‐free products and processes. It compares motivations for change that other studies have not compared. Manufacturers searching for direction and example to meet waste minimization goals will find the paper useful in providing such.

Details

Soldering & Surface Mount Technology, vol. 18 no. 3
Type: Research Article
ISSN: 0954-0911

Keywords

Article
Publication date: 1 June 2004

Richard Ciocci and Michael Pecht

Eliminating lead in electronics is an environmentally considerate approach that is made prior to manufacture. Recently enacted legislation encourages increased recycling…

465

Abstract

Eliminating lead in electronics is an environmentally considerate approach that is made prior to manufacture. Recently enacted legislation encourages increased recycling of electrical and electronic products. However, recycling is typically an end‐of‐use action occurring just before final disposal. From an environmentally‐considerate perspective, lead elimination or replacement is a better approach. Short of having a definitive study to follow, industry, regulators, and consumers are proceeding with the change. Various lead‐free alloys have been tested and used for electronic components and assemblies. There are many replacements for eutectic tin‐lead solder, and alloys containing tin, silver, copper, and bismuth have been used successfully. Assessing how the electronics industry is addressing the change to lead‐free materials and processes requires answers to various questions. These questions regard the effects of changes to electronic products and their processes. What drives lead‐free migration, how processes can develop, and when products will be available are issues which define the assessment.

Details

Circuit World, vol. 30 no. 2
Type: Research Article
ISSN: 0305-6120

Keywords

Article
Publication date: 1 December 2001

L. Yang, J.B. Bernstein and K. Chung

This paper will review the challenges brought by lead‐free soldering and some preliminary experimental evaluation results will be discussed. The initial results show that…

Abstract

This paper will review the challenges brought by lead‐free soldering and some preliminary experimental evaluation results will be discussed. The initial results show that the lead‐free soldering process with 260°C reflow peak temperature does not directly cause failures for bismaleimide‐triazine (BT)‐based fine pitch ball grid array (FPBGA) packages. However, the strict lead‐free soldering condition could degrade the integrity of weak interface joints and potentially damage the package in subsequent unbiased highly accelerated stress test (unbiased HAST) evaluation. The impacts of lead‐free soldering with high reflow temperature on concurrent available electronics components could be more severe than previously believed. In the future, new materials and design concepts should be applied to enhance the package reliability under strict lead‐free soldering conditions.

Details

Microelectronics International, vol. 18 no. 3
Type: Research Article
ISSN: 1356-5362

Keywords

Article
Publication date: 1 April 2004

Joe Smetana, Rob Horsley, John Lau, Ken Snowdon, Dongkai Shangguan, Jerry Gleason, Irv Memis, Dave Love, Walter Dauksher and Bob Sullivan

The High Density Packaging Users Group conducted a substantial study of the solder joint reliability of high‐density packages using lead‐free solder. The design, material…

Abstract

The High Density Packaging Users Group conducted a substantial study of the solder joint reliability of high‐density packages using lead‐free solder. The design, material, and assembly process aspects of the project are addressed in this paper. The components studied include many surface mount technology package types, various lead, and printed circuit board finishes and paste‐in‐hole assembly.

Details

Soldering & Surface Mount Technology, vol. 16 no. 1
Type: Research Article
ISSN: 0954-0911

Keywords

Article
Publication date: 1 June 2004

Paul Casey and Michael Pecht

This paper presents the analysis of information collected from numerous patent searches on lead‐free alloys. The significance of claim structure and content is discussed…

Abstract

This paper presents the analysis of information collected from numerous patent searches on lead‐free alloys. The significance of claim structure and content is discussed in view of the growing number of lead‐free patents. Patent analysis software was developed to effectively compare over 350 lead‐free alloy patents. A case study was conducted to assess Sn‐Ag‐Cu and special purpose lead‐free candidate alloy intellectual property. The results show that there are a number of patents and patent applications that may affect the use of “popular” Sn‐Ag‐Cu formulations.

Details

Circuit World, vol. 30 no. 2
Type: Research Article
ISSN: 0305-6120

Keywords

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