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RoHS: Eighteen Months Later
December 31, 1969 |Estimated reading time: 3 minutes
By Ronald Lasky, Ph.D.
Eighteen months ago, RoHS went into effect with predictions of imminent economic, logistic, and end-product-reliability disasters hanging in the air. I think it is now insightful to reflect on what has actually occurred.
As a review, the intent of RoHS is not primarily to protect the environment, it is to facilitate recycling. Witness this excerpt from paragraph 6 in the introduction of the EU's RoHS document: "Restricting the use of these hazardous substances is likely to enhance the possibilities and economic profitability of recycling of WEEE and decrease the negative health impact on workers in recycling plants."
With the initial goal of WEEE of about 75% of products being recycled, future generations can look forward to recycling rates approaching 100%. Such ambitious recycling goals can only be achieved if recycling is easy and safe. Interestingly, the recycling aspect of RoHS has yet to become common knowledge.
RoHS addresses the "safe" part of recycling, but what about the "easy"? Enabling recycling is part of the field of sustainable design. Future electronics products must be increasingly easier to disassemble and materials easier to reclaim. De-soldering is vital in this reclaiming processes. Since soldering forms a low temperature reworkable electrical and mechanical bond, it is easy to disassemble solder joints. Therefore, components can be readily removed from PCBs, for reuse or recycling.
SucessesI estimate that, since July 1, 2007, over $400 billion1 of electronic products have been manufactured worldwide. During this time the following successes have occurred:
1. There have been no reports of widespread failures attributed to lead-free assembly (with some products in the field since 1999).
2. Even though there have been a few prosecutions by the EU for RoHS violations, the EU appears to want to work with offending companies in an even-handed manner.
3. Although the assembly industry has had to work hard to resolve logistics issues, some leaders have developed effective strategies to build non-RoHS, RoHS 5, RoHS 5.5, and RoHS 6 products in one facility.2
4. Industry leaders have performed significant process R&D to optimize lead-free assembly yields by minimizing voiding in solder balls, tombstoning of passives, and assembling of mixed technologies (i.e. leaded solder and lead-free solder balls, often called RoHS 5.5).
5. SAC 305 (96.5% tin/3.0% silver/0.5% copper) was established as a de-facto solder alloy standard.
6. Intel and others have established a lead-free technology to replace high-lead solder joints for flip-chip.
Challenges1. Demonstration of long term reliability (longer than 10 years) of lead-free products for mission-critical applications is still elusive. The EU issues exemptions for military and other mission-critical products.
2. Tin whiskers remain a concern for high-reliability products. The project engineer responsible for something like the Hubble Telescope should assure that the component finishes offer no risk of metal whiskers. However, I do feel that the risk of whisker failures for consumer products is overstated. Mitigation techniques can reduce the risk to a level that is orders of magnitude below that of other reliability failure modes. Only scores of tin whisker failures have been recorded, whereas tens of millions of fails have been attributed to keypads, connectors, switches, and disk drives.
3. Obtaining non-RoHS (i.e, lead-containing lead finishes) compliant products for exempt applications. This concern is especially critical for military electronics. These products need the proven long-term reliability (in some cases more than 30 years) of tin/lead solder. When component suppliers no longer supply components with tin/lead lead finishes, military assemblers have to strip the lead-free finishes and reapply a tin/lead finish. This extra step is costly and may damage the component.
So RoHS is here to stay. It hasn't been an easy transition, but in many respects it has gone more smoothly than expected. Our grandchildren will be proud of us, when almost all of their electronics can be safely recycled because of RoHS and the legislation that follows it.
1. My estimating procedure follows: The total world electronics production is about $1,000 billion per year or $1,500 billion in 18 months. The EU produces and consumes about 20% of the world supply, in addition many companies that sell in the EU have made many of their products RoHS-compliant even where not needed to avoid having two or more product lines. Hence, I estimate that something like 2530% of all electronics are RoHS- (or lead-free) compliant. Admittedly, this calculation is "rough" because of exemptions, etc., but it mates well will anecdotal reports of solder paste type usage.
2. Bratinikov, Alexander, Jabil Corp.; Lasky, Ronald, Indium Corp, "Assembly of Large PWBs in a RoHS Environment," to be presented at APEX 2008, April 2008, Las Vegas, Nev.
Ronald Lasky, Ph.D., PE, an SMT Editorial Advisory Board member, is senior technologist at Indium Corp., instructional professor at the Thayer School of Engineering, and director of the Cook Engineering Design Center at Dartmouth College, Dartmouth, N.H. Contact him at (603) 646-9197; ronlasky@aol.com.