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The Impact of Reflowing A Pbfree Solder Alloy Using A Tin/Lead Solder Alloy Reflow Profile On Solder Joint Integrity |
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Abstract:
The electronics industry is undergoing a materials evolution due to the pending Restriction of Hazardous Substances (RoHS) European Directive. Printed wiring board laminate suppliers, component fabricators, and printed wiring assembly operations are engaged in a multitude of investigations to determine what leadfree (Pbfree) material choices best fit their needs. The size and complexity of Pbfree implementation insures a transition period in which Pbfree and tin/lead solder finishes will be present on printed wiring assemblies. Ball grid array is one component style that has generated concern with respect to mixed finish scenarios. To better understand the reliability effect of mixed surface finish manufacturing, an investigation was conducted to evaluate the solder joint integrity impact of reflowing a Pbfree solder alloy using a tin/lead reflow profile. In this study, ball grid array components with tin/silver/copper (SAC) solder spheres were processed using a tin/lead reflow profile and then subjected to thermal cycle testing from -55ºC to +125ºC. Solder joint life measurements and failure analysis revealed premature solder joint failures due to non-uniform microstructure and poor wetting characteristics.
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Electroplated Tin and Tin Whiskers in Lead Free Electronics |
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Introduction:
The electronics industry is under extreme pressure from the environmental community to remove elemental Lead (Pb) in the form of the commonly used tin-lead solders from electronic components and assemblies. Pure tin is being electroplated onto component terminals as an inexpensive, solderable, drop-in replacement for the tin-lead alloy electroplated component terminal finishes that have been successfully used for some 60 years. This replacement of tin-lead alloy with pure tin makes the formation of whiskers by tin (Sn) and tin alloys in electronic assemblies a major concern for failure (1). When these electrically conductive, single crystal tin whiskers grow significantly, (e.g.>50 microns and sometimes several mm), electrical shorting between fine pitch circuits becomes possible, leading to catastrophic electrical short circuit failures in high reliability systems such as heart pacemakers, spacecraft, or military weapons and radars. Worse yet, the thin filamentary tin whisker can fuse, creating a plasma that can conduct hundreds of amperes, destroying electronic equipment such as power supplies in high-current applications.
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Lead-free SMT Soldering Defects - How to Prevent Them |
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Introduction:
Tin-Silver-Copper alloys are the primary choice for lead-free SMT assembly. Although there are other options available such as alloys containing bismuth or indium and other elements, tin-silver-copper solders, also known as SAC alloys are by far the most popular. They are used by approximately 65% of users, as last surveyed by Soldertec in 2003.
The lead-free SMT process differs from a 63/37 process in numerous ways. A good understanding of these differences when using SAC alloys, will enable process engineers to bring about the necessary changes to the SMT process and reduce soldering defects, increase lead-free assembly reliability and maintain production yields.
Often when a manufacturer transitions to lead-free soldering an increase in defects is noticed. This is often the result of a not properly implemented process. A well-defined, optimized and controlled lead-free process will not augment defect rates.
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Lead-Free Components Problems - A Need for Change |
Source: Bob Willis - www.leadfreesoldering.com |
Introduction:
With the impending move to lead-free production there are really two main component issues that engineers must address as quickly as possible. These are the temperature requirements of processing lead-free solder alloys and the termination finishes used as alternatives to tin/lead. New design are being conceived every week and design engineers must consider component temperature requirements for all future design, now. They need to ask suppliers about process limitations at the same time as questioning the components electrical parameters. If not they need to pass on the specific requirements in a specification to purchasing staff as often the purchasing department are the main interface with component producers or distributors.
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Joint Lead-Free Solder Test Program for
High Reliability Military and Space Applications |
Source: JG-PP/JCAA Lead-Free Solder Project |
Abstract:
Current and future space and defense systems face potential risks from the continued use of tin-lead solder, including: compliance with current environmental regulations, concerns about potential environmental legislation banning lead-containing products, reduced mission readiness, and component obsolescence with lead surface finishes. For example, the United States Environmental Protection Agency ( US EPA ) has lowered the Toxic Chemical Release reporting threshold for lead to 100 pounds. Overseas, the Waste Electrical and Electronic Equipment ( WEEE ) and the Restriction on Hazardous Substances (RoHS) Directives in Europe and similar mandates in Japan have instilled concern that a legislative body will prohibit the use of lead in aerospace/military electronics soldering. Any potential banning of lead compounds could reduce the supplier base and adversely affect the readiness of missions led by the National Aeronautics and Space Administration ( NASA ) and the U.S. Department of Defense (DoD). Before considering lead-free electronics for system upgrades or future designs, however, it is important for the DoD and NASA to know whether lead-free solders can meet their systems’ requirements. No single lead-free solder is likely to qualify for all defense and space applications. Therefore, it is important to validate alternative solders for discrete applications.
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Materials Control for Lead-Free Manufacturing |
Source: François Monette - Cogiscan Inc |
Abstract:
The upcoming transition to Lead-Free electronics assembly has been a subject of much research and discussion lately. To manage this important transition requires a significant effort in many areas. The challenge does not stop when the new process and materials have been selected and qualified.
The key issue that remain is that of managing the material logistics.
A successful transition will require a significant collaborative effort between production, engineering, procurement, and a large number of component suppliers and distributors. During this process one area that should not be overlooked is the actual production floor. After all this is where all the different materials come together to make the finished product. The assembly line is where the largest number of people are involved and the complexity of their task translates in the highest risk of errors.
This paper focuses on the practical considerations of managing the materials on the production floor during the transition to Pb-free.
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WEEE and RoHS Directives: New Requirements Impacting the Global
Supply Chain of the High-Tech Industry |
Source: Kenneth S. Rivlin, Jean-Philippe Brisson and David Wharwood - Allen & Overy LLP |
Introduction:
On January 23, 2003, the European Union (EU) adopted two significant environmental laws that are already having a far-reaching impact on the U.S. high-technology industry. These laws are the Directive on the Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment (RoHS Directive) and the Directive on the Waste Electrical and Electronic Equipment Directive (WEEE Directive).
The WEEE and RoHS Directives apply to electrical and electronic equipment (EEE) sold in Europe and falling into specific categories listed in the Directives. EEE essentially means any product that requires electricity to function properly. By July 1, 2006, t he RoHS Directive will prohibit the use of six substances, including lead, in EEE subject to certain exceptions. Under the domestic laws of the countries members of the EU (Member States), companies that sell non-compliant EEE may be subject to civil and criminal fines and penalties. In addition, non-compliant products may be impounded. The WEEE Directive obliges producers of EEE to set up recycling systems or otherwise make arrangements to collect the waste of their EEE (WEEE).
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