Papers by Eric Bastow
by Eric Bastow
Low melting-temperature alloys are vital to successful electronics assembly.
Solder is a critical material that physically holds electronic assemblies together while allowing the various components to expand and contract, to dissipate heat, and to transmit electrical signals. Without solder, it would be impossible to produce the countless electronic devices that define the 21st century.
Solder is available in numerous shapes and alloys. Each has its particular properties, providing a solder for nearly every application. Many times, solder is an afterthought in the design and engineering process. However, by considering the soldering step early in the design process, problems can be minimized. In fact, with the proper information, the characteristics of a solder can be part of an optimal design.
solder
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Posted on 1 Dec 2005
by Eric Bastow
With the predominance of no-clean soldering processes and ever decreasing component standoff, the industry has had to consider the reliability of, what may be, partially activated or "gooey" flux residues under component bodies. Similarly, questions have also risen about the reliability of flux residues resulting from the reflow of no-clean solder pastes that are "entrapped" under RF shields or "cans", where escape of the volatile ingredients of the flux is greatly hindered. In this paper, discussion will be made regarding an experiment designed to mimic the aforementioned conditions and how these conditions affected the SIR performance of the no-clean flux residues. A variety of no-clean solder paste flux residues will be discussed, including a halogen-containing, Pb-free solder paste flux; a halogen-free, Pb-free solder paste flux; a halogen-free, Pb-free solder paste flux with a residue optimized for pin probing; and a halogen-free SnPb solder paste flux.
Apex 2011, solder paste, pb-free, halogen-free, no-clean flux, flux residue
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Posted on 11 Apr 2011
by Eric Bastow , Timothy Jensen
The advent of the EU’s RoHS law has encouraged a significant amount of research to find an alloy, for electronic assembly that will satisfy RoHS’s lead-free requirement and have optimum process ability and field reliability. The resulting research, much of it lead by iNEMI, resulted in the near eutectic tin-silver-copper alloy SAC387 (Sn95.5Ag3.8Cu0.7) as an initial favorite to fill this need in the early 2000s. By 2004 or so, many people were using SAC305, partially because of its greater resistance to tombstoning. It appeared that SAC305 would become the de-facto lead-free standard alloy for RoHS compliant electronic assembly. However, with the dramatic increase in silver prices in the last few years, SAC105, having 2% less silver was being evaluated and used for its obvious cost savings. Reliability testing of SAC105 also showed that although it did not perform as well as SAC305 in thermal fatigue cycle testing, it was better than SAC305 in drop shock tests. The explosive growth of mobile phone sales, over 1 billion per year, made SAC105’s superior drop shock performance attractive for these and other portable devices.
In addition to research relating to SAC305 and SAC105, much work has been performed on the study of the effects of small quantities (<0.1%) of alloying metals on lead-free alloys’ process ability and reliability performance. These "dopants" can dramatically affect an alloy’s performance.
All of the above work has resulted in what many are calling lead-free alloy proliferation as more and more alloys are being considered for implementation. This proliferation drives up solder paste cost as manufacturers cannot achieve economies of scale. In addition, with so many alloys to consider, it is difficult for researchers to develop extensive data bases of process and reliability performance.
This paper is an overview of this lead-free alloy proliferation and an outlook on how alloy convergence might occur.
solder, SAC, pb-free, dopants, Reliability, thermal cycling, drop testing
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Posted on 15 Oct 2009
by Eric Bastow
The indium-lead (In/Pb) binary system offers numerous alloy combinations. These materials possess mechanical and physical properties which make them useful in many
demanding applications. With small additions of silver (Ag), additional alloys are created, rounding out this set of materials and providing us with a full set of performance capabilities. This is especially valuable in the electronics assembly soldering arena.
With melting temperatures ranging from 154°-313°C, this alloy family offers numerous choices for accommodating temperature sensitive applications, as well as step-soldering operations. In/Pb alloys also possess metallurgical properties that make them particularly suitable for soldering to thick Au metallizations.
Assemblers should not be dissuaded from using this versatile alloy family just because the joints that they form may not have the same visual characteristics that Sn/Pb and Pb-Free alloys have.
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Posted on 10 Mar 2010
by Eric Bastow , Chris Nash
Many electronics manufacturers perform SIR testing to evaluate solder materials and sometimes the results they obtain differ significantly from those stated by the solder material provider. The difference in the results is typically the result of SIR coupon preparation. This paper will discuss the issue of SIR coupon preparation, board cleaning techniques, and how board cleanliness directly affects SIR results.
solder paste, flux, SIR, surface insulation resistance, solder materials
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Posted on 20 Jun 2011
