Comparison of Tin-Silver-Copper Lead-Free Alloys
Tin-Silver-Copper alloys are the leading candidate lead-free substitute. However, as there are several different Tin-Silver-Copper alloys, background information is necessary to determine which alloy is best suited for the broadest range of applications. The Sn96.5/Ag3.0/Cu0.5, Sn95.5/Ag3.8/Cu0.7, and Sn95.5/Ag4.0/Cu0.5 alloys are compared for availability, cost, solder paste printing, melting, wetting, wave soldering, thermal fatigue and solder joint reliability.
Practical Guide to Achieving Lead-Free Electronics Assembly
To successfully achieve lead-free electronics assembly, each participant in the manufacturing process, from purchasing to engineering to maintenance to quality and inspection, must have a solid understanding of the changes required of them. This pertains to considerations regarding design, components, PWBs, solder alloys, fluxes, printing, reflow, wave soldering, rework, cleaning, equipment wear & tear and inspection.
in Lead-Free Electronics Assembly
The question of what happens to a lead-free solder joint if it becomes contaminated with lead is important because during the transition to lead-free soldering it is very likely that tin/lead parts will still be used in a great deal of production. In other words, just because one implements a lead-free solder alloy does not mean that tin/lead coated components and boards will disappear immediately. In fact, exposure to lead from boards, components and repair operations could occur for years to come. This paper discusses the dynamics of lead contamination and provides real-world examples of failures caused by the lead contamination of lead-free solders.
and Process Considerations for Lead-Free Electronics Assembly
With the WEEE Directive in Europe potentially outlawing lead from some electronic devices produced and imported in the EU by 2006 and foreign competition driving the implementation of lead-free electronics assembly around the world, additional questions regarding the integrity and reliability of various alloy compositions continue to arise. In short, the issue of which alloy(s) to select continues to loom. This paper shall take an in-depth view of Sn/Ag, Sn/Ag/Cu and Sn/Cu alloys and compare the reliability testing results and process considerations for these.
for Printing Lead-Free Solder Pastes
SMT printing will require reexamination and process adjustment when lead-free soldering is implemented. If a high quality solder paste is used and standard rules for SMT printing are followed, consistent stencil life, aperture release, print definition, high-speed print capabilities and print repeatability may be expected. However, implementation of lead-free solder paste does necessitate some adjustment, as well as providing an opportunity to review and fine-tune several key printing parameters.
Study of Lead-Free Wave Soldering
This brief study of lead-free wave soldering focuses upon copper dissolution and solder maintenance issues. Unfortunately, it is determined that waste and changeover costs can dramatically increase with lead-free wave soldering.
Study of Antimony
The issue of the toxicity of antimony has arisen as the search for viable lead-free alloys continues. Confusion regarding the toxicity of antimony has developed as a result of legislation concerning antimony trioxide, as well as unfounded speculation concerning the element in an alloyed form. This paper details third party and governmental studies and legislation concerning antimony and its "toxicity". This data then is compared to that of the "safe" elements that comprise the majority of lead-free solders, including silver, copper, zinc, compounds of tin, as well as lead. This data indicates that antimony is no more "toxic", often is far less-stringently regulated, and is classified as less of a health threat than many of the other aforementioned elements.
Study of Lead-Free Alloys
With the ongoing concerns regarding environmental pollutants, lead at one time was heavily targeted in the electronics assembly arena. AIM reacted to these concerns by developing its patented lead-free alloy CASTIN®. This paper highlights the development process and application information for CASTIN®.
One result of the push to find lead-free solder alternatives is that there are now many options available to the board assembler. Much development, patterning and research has gone into finding viable solutions for those who want to eliminate lead from their process. However, each of these alloys is different in significant ways and background information is
Comparison of Lead-Free Alloys
Based on recent market developments, it appears that the choice of suitable lead-free alloys to replace Tin-Lead for electronics assembly is narrowing. Three candidates have emerged as potential standards for the industry. They are the Tin-Copper eutectic (Sn99.3/Cu0.7), the Tin-Silver eutectic (Sn96.5/Ag3.5), and CASTIN® (Sn96.2/Ag2.5/Cu0.8/Sb0.5). This paper details extensive testing covering several variables that was conducted in order to make objective comparisons between the three alloys.