The costs of going green: environmental requirements are forth coming but at what costs to industry (and consumers)? A primer on meeting WEEE and other laws.
The EC estimates (1) that electronics contributes 4% of the municipal waste stream, and it is growing at 3 to 5% per annum, three times the rate of growth of other wastes. Over 90% of this waste is landfilled. Four hundred million cell phones are produced a year, and perhaps 500 million PCs will be obsolete by 2007. As a result, the EC has assumed the lead in environmental opinion and legislation. A spate of regulations has spurred manufacturers into reexamining products and processes. The questions are: How effective are these measures at protecting the environment and what is the cost?
That issue is one of constant debate; environmental impact depends on toxicity and availability, and the assumptions made in the models can have a huge impact. The cost of environmental compliance may be high in hidden ways--one estimate found that, if all soldering were switched to lead free, the increased power consumption from the 27,500 reflow ovens installed worldwide would be equivalent to 1.2B kWh, the output of 60 small power plants. (2) Some aspects of green electronics such as lead-free solder seem to be unstoppable, until we have a worldwide en-of-use takeback and recycling initiative.
But few will mount an "I'm for lead" platform, and legislators eliminating an element is easier than setting up a recycling infrastructure and compelling consumers to pay for it. The attitude in many places is, therefore, that the environmental impact is uncertain and probably impossible to resolve unambiguously, but, if we can remove materials from the system, why shouldn't we?
Changes in Attitudes
In Europe the precedent for product takeback and recycling has been established with the ELV (vehicle end-of-life) directive, which places the responsibility for disposal firmly on the importer or manufacturer. The directive also sets restrictions on a range of hazardous materials in manufacturing, a list that is being revised, reportedly, to include electronics assemblies.
The WEEE (Waste Electrical and Electronic Equipment) directive and RoHS (Reduction of Hazardous Substances), adopted May 15, 2001, follow this pattern, setting recycling targets and limiting lead, mercury, cadmium, hexavalent chromium and some brominated flame retardants. The legal interpretation of product exemptions and inclusions will not become clear until EC country laws are passed in 2004. Exemptions stated are "servers, storage ... voice and data transmission and networking equipment," and wording has now been added for the first time to permit environmental risk assessment. Nevertheless, regulations that will affect a range of mainly consumer electronics will take effect July 1, 2006.
Some national legislation is already in place. Sweden's recycling law was enacted in 2001. Japan's electronic appliance recycling law, enacted in April 2001, covers larger domestic appliances and is expected to be extended progressively to computers and other areas. A user fee of $30 is charged, and recycling plants have been set up by major electronics manufacturers.
In the U.S. most activity has been at the state level and has been aimed at TVs and computer monitors, which can contain several pounds of lead used for radiation screening. Massachusetts started a disposal and recycling initiative in 2000, and several other states ate following suit.
The consumer attitude is changing worldwide, and the electronics industry had better be aware of it. In 1983 66% of consumers would switch to an equivalent brand with a "better" environmental impact; in 1998 the number was 76%. (3) Forty-four percent have bought a product specifically because of its environmental benefits. Yet the disconnect is that just 4% of corporate executives felt the company's environmental record was critical, as compared with 20% of consumers. Makers of consumer electronics, particularly in Japan, have been quick to identify this trend and launch "lead-free" and "halogen-free" products, followed closely by Europe, which will roll out similar products before the 2006 deadline.
The trend is not limited to Asia. HP, for example, employs an "environmental product steward" whose job is to work with the design team throughout the process of designing printers. (4) Success stories include a reduction in power consumption for laser printers from 120 W in 1986 to 21 W today for an equivalent model. At press time, HP's recycling plant in Roseville, CA, charges $13 to $34 for each item it recycles. (5)
The Decision Tree
Design for the environment (DfE) is extremely tough because of the tradeoffs. If lead is replaced with tin, perhaps the burden on the environment decreases in the nation that consumes it but increases disproportionately in the nation that mines and refines it. Replacing lead with silver creates a residue that is 100 times more toxic to aquatic life than pure lead.
The automotive industry has struggled with tradeoffs, substituting lighter metals for steel to increase fuel economy. (6) An aluminum-bodied auto uses less gas but is more complex to join, and more energy is used to produce it. The breakeven point for the environment is hard to determine--and will the initial buyer accept a significant cost increase if not mandated to do so via legislation?
In electronics, we need to consider design for manufacturability, use, demanufacturing and reuse and then consider the viability of the recycle and reclaim route. As an example of how a move aimed at another part of the design chain (disposal) can affect manufacturability, consider lead-free solders. The main consequences of moving to most lead-free solders are higher processing temperatures, different wetting characteristics and different joint appearance. A literature search turns up many islands of good information separated by a sea of unknowns. Test methods and systems used are not always compatible. The processing temperature is increased 20[degrees]C to 40[degrees]C, and the process window is reduced from 40[degrees]C to less than 20[degrees]C. Many lead-free boards have been produced--certainly in the millions in Asia, hundreds of thousands in Europe, and probably only in the tens of thousands in the U.S. Most manufacturers are still gearing up to lead-free assembly and find the array of choices bewildering.
The rules for design for use are fairly simple on the surface but not so easy to apply. Products should function as intended for the lifetime of the product and should not consume excessive amounts of consumables, such as non-rechargeable batteries.
Manufacturers also have to deal with unintended consequences of the product's use or disposal. Pressure to eliminate bromine-containing flame-retardants from casings comes from the volatility of the compounds and their detection in the bloodstreams of users and dismantling operators. The use of underfills on handheld packages makes rework and reclaim of integrated circuits (ICs) almost impossible.
Some of the steps taken by manufacturers to identify casing components are an important first step in segregating for recycling. One example is Nokia phone face plates, which are clearly labeled with the plastic type. Disassembly is enhanced by using snap-fit rather than adhesives or screws--some devices such as laptop computers are extremely difficult to dismantle and contain a huge range of materials. The temptation here is to shred the device and separate the materials by flotation and other techniques, but this practice precludes the recovery of usable components, some of which may have a high value.
The diversity of materials is a real issue when dealing with post-consumer scrap. Over 300 types of plastic have been used in monitor production and separating them all into high-value scrap is not economical. A typical board contains 15 to 20% copper, 7 to 10% solder and about 1,000 g/tonne precious metals (gold, palladium, silver). Most of the balance is thermoset epoxy and glass, with less than 10% ceramic and other materials. If the value of the components does not merit their removal, ceramics, thermoset epoxies and glass are not recyclable into any valuable form, which means that the only valuable materials are the metals, at about 20 to 30% by weight. The epoxy has calorific value, but, if incinerated at low temperatures, bromine analogs of dioxins form; these long-lasting substances are in some cases suspected carcinogens.
The definitive work on the recycling of electronics is available for download from www.deer2.com as the Mission Needs Statement of the U.S. Army's DEER2 program, paraphrased below. Three main options are available in the decision tree:
* Sale as-is (only 40% work on receipt).
* Test and sale (higher value).
* Test, repair, and sale (same value as above but higher labor content).
* Segregation and sale of valuable components (ICs, drives, processor packages, modem cards, etc.).
* Sale as-is.
* Test and sale.
* Test, repair, and sale.
* Physical separation (density, magnetism, electrostatics).
* Monitors--separate glass recycling loop (see www.enviroinc.com).
* Pyrometallurgy (copper smelters--recovers the energy value of epoxy, recovers metals and uses glass as flux).
* Chemical separation (need to use a closed system to minimize effluent).
The document outlines key considerations in each area; the decisions are really driven by economics. If you are considering electronics recycling, read this report.
For pre-consumer scrap the disposal mechanism is a contract between the manufacturer and an approved recycler. This scrap is often high value and has the advantage that it is homogenous in nature. For post-consumer scrap the cycle becomes more complex. All components of the recycle loop must be present for it to work:
* The consumer. Needs an incentive to recycle electronics goods. Typically the cost is $30 per item. Assessing that cost as a penalty will be an incentive to dump illegally rather than to dispose of lawfully. Incentives include tax rebates for giving to charitable organizations or balanced as a rebate against future purchases. Each country seems to have a different approach.
* The collector. Must collect and assess the goods. May be collection from the customers' site (electronics store) or a drop-off point for easily portable items.
* The dismantler. Must be skilled in identifying valuable components.
* The reclaimer. Must be able to segregate and reclaim components in an environmentally responsible way.
* The semi-finished product maker. Recycles dross into solder, polymer grindings into phone cases, etc. Has to see value in the products from the reclaimer.
* The producer. Must have a view of the supply chain and create demand for recycled materials (aided by legislation).
* Contract manufacturers and component manufacturers. Need guidelines from OEMs: Should they use more expensive halogen-free boards or lead-free solders. Who will pay?
* Retail outlets. Have the potential to be effective collectors and manage customer incentives on new purchases.
The steps to participate profitably from the changes include:
* Be informed. Excellent material is available from conferences, (7) the EC, industry associations such as Tin Technology Ltd. (8) and private companies such as Entec. Sign up for the e-mail forums on halogen-free, lead-free manufacturing and general environmental awareness through IPC. Results of the IDEALS, NEMI and NCMS studies have been published.
* Communicate. Talk to your suppliers and customers to understand their issues and see how they are coping. Lean on each other to get through challenging areas.
* Be involved. Give input to trade associations, workshops, multi-client studies, consortia, standards and road-mapping activities.
WEEE and RoHS: www3.europarl.eu. int/omk/omnsapir.so/pv2?PRG=CAL END&APP=PV2&LANGUE=EN&TPV= PROV&FILE=010515
Massachusetts CRT Recycle Law: www. state.ma.us/dep/recycle
Entecuk (EC legislative updates): www. entecuk.com/client/ec/downloads/en_ appb.doc
Lead Development Association: www. ldaint.org
DEER2 Electronics Recycling Initiative: www.deer2.org
Soldertec--Tin Technology Ltd.: www. lead-free.org
This guide is an example of one supplied to companies starting to become involved in lead-free assembly. It is based on a study involving 700 boards and 750,000 components assembled on boards of three thicknesses, six solder alloys, five surface finishes, reflow and wave, with air to air and liquid to liquid reliability testing.
Do I have to print differently than eutectic alloy?
Lead free paste printing must take into account the fact that the molten solder will not spread to cover pad areas left open in the print process. All alloys and surface finishes show this effect.
Will I have to reflow at 260[degrees]C?
Not necessarily. On smaller boards with low thermal mass, 230[degrees]C can be possible. More complex boards will require higher temperature and attention to detail on heat distribution.
Do I need nitrogen?
Nitrogen will buy 10[degrees]C; solder at a lower temperature and get a better joint but incur nitrogen cost. The different rate of flux evaporation in nitrogen as opposed to air has been blamed for tomb-stoning in some assemblies when 0201 components are reflowed in nitrogen and the lightweight components can float on flux exudates.
Is new equipment necessary?
For really simple boards the existing reflow oven is probably fine. Complex boards require use of a multi-zone--seven zones of more--oven with integral flux management and nitrogen capability for when it is needed. Wave solder pots of corrosion-resistant cast iron are fine, but stainless steel components are attacked by lead-free alloys over a period of months. Retrofits of specially coated stainless steel for wearprone components ate available.
What temperature is needed for the solder pot?
You may be able to use the same temperature you use with eutectic tin--lead-250[degrees] to 260[degrees]C.
Do I need a special board material?
Already one-third of the U.S. industry has switched to higher Tg materials--170[degrees]C vs. 140[degrees]C--for a greater margin of safety in rework. These materials work fine in lead free but take care that the time to delamination of the grade you choose--typically the T260 rating--is also improved over regular FR-4. The above refers to complex boards for professional electronics. With single-sided boards for TV or other applications, even FR-2 boards can be soldered lead free with care.
What surface finish should I use?
Lead-free HASL is available and works well. Data show that organic solderability protectant (OSP), despite some rumors, works well even in air as long as the number of reflow cycles is limited. Tin and silver finishes perform well. Nickel-gold is fine also but is being relegated to a more minor role as OSP, tin and silver usage increases.
Will components popcorn?
Popcorning may occur, depending on the size of the components, their design and your thermal profile. Although epoxy molding compound makers have produced compounds that will comfortably take 260[degrees]C for Jedec level 2A, most components are working well with standard molding compound. Reliability of large ceramic components such as 1206 resistors may be an issue because of thermal mismatch with the circuit board material causing failure in thermal cycling.
How do the joints look?
Because of the different crystallization of lead-free solders, they look matte rather than shiny. Joints are typically not as shiny as eutectic joints due to the formation of relatively large crystals of a tin-rich phase during cooling. This result is seen in all alloys and surface finishes. Voids are an issue, particularly in fine-pitch BGA joints due to the high surface tension of tin-rich alloys preventing the escape of bubbles from flux solvents or microvia in pad voids. They can be minimized by careful process and materials control. Tin-silver-copper alloys and tin-lead appear in our study to give less voids than other alloys.
How do I clean?
Air-reflowed boards will be tougher to clean than nitrogen-reflowed boards because of flux residue oxidation, but equipment and surfactant vendors do have systems that perform well on lead-free boards.
What other precautions will I need to take?
Segregate lead-free and lead-tin solder in processing and rework. Lead-contamination could cause reliability issues according to several studies.
What is the reliability compared to eutectic solder?
We tested reliability--air to air, liquid to liquid--between 550[degrees]C and 1250[degrees]C. We found no major difference between the alloys and surface finishes, but we did find that large resistor components (1206) failed frequently due to joint cracking under thermal stress,
What alloy should I use? Aren't there several tin-silver-coppers?
Much of the work in Europe and the U.S. has been on 3.8 to 4.0% silver with 0.5 to 0.7% copper. Japanese work focused on 3% silver to reduce costs. Realistically, all these alloys melt around 217[degrees]C, and in our study the 3% and 4% silver alloys performed about the same. Make sure your solder manufacturer has cross-licensed the alloys you need to cover the global market as the patent situation is complex.
(1.) Kay Nimmo, "European Legislation on Lead in Electronics Circuits Moves Forward," Solder & Assembly Technology, no. 2, p. 2, 2001.
(2.) Harvey Miller, "Lead-Free Electronic Solder--Why?" Infrafocus, 2002.
(3.) Iwona Turlik, "Electronics and the Environment," IPCWorks Proceedings, October 1999.
(4.) Russ Arenson, "The Greening of Technology, Electronic Business Asia, July 2001.
(5.) Colleen Valles, "Electronics Recycling," Associated Press, May 22, 2001.
(6.) Anish Kelkar et al., "Automobile Bodies: Can Aluminum Be an Economical Alternative to Steel," Journal of Materials p. 28-32, August 2001.
(7.) H. Reichl and H. Griese, ed., "Electronics Goes Green 2000+," September 2000.
(8.) Soldertec (Tin Technology Inc.), "European Lead-Free Technology Roadmap," February 2002.
Alan Rae is vice president of technology at Cookson Electronics Inc. (Foxborough, MA). He can be reached at 508-698-7238; e-mail: arae@cookson electronics.com.
Originally published in PC FAB, now Printed Circuit Design and Manufacture; www.pcdandm.com.
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|Date:||Jul 1, 2003|
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