Amandate coming out of the European community, the Restriction of Hazardous Substances or RoHS, bans lead, mercury, cadmium, and three other hazardous substances from electronic equipment sold in Europe. Adhering to this international directive will take a bit more than just replacing leaded components with lead-free versions.

The directive will affect manufacturers of household appliances, IT and telecommunications equipment, lighting equipment, electrical and electronic tools, toys, sports equipment, medical devices, and eventually monitoring and control instruments. The European deadline is July 1, 2006, and other countries follow soon thereafter. Component manufacturers are already discontinuing non-compliant parts, and every electronic product is impacted.

Those tasked with getting the lead out, the most often mentioned material, can start with two questions: Do you know if lead-free substitutes are available? And if so, will they handle the higher reflow temperatures needed by lead-free solders?

If you can't answer these, you're not alone. Over half of the respondents to a recent survey on the topic say their companies have not begun designing the six materials out of their electronics. Fortunately, contract manufacturers of electronic products are a little more on the ball and have been preparing for July 2006. Here's a glimpse at what to expect and how some contract manufacturers have prepared.

What designers should know

First of all, don't think that the mandate is a manufacturing-only problem. EMA Design Automation, a supplier of electronic-design software, Rochester, N.Y., (ema-eda.com) says there are certainly significant manufacturing issues, but simply replacing parts with lead-free equivalents creates new issues. A lead-free version, for instance, might be larger and heavier than its leaded variation. Not all parts have lead-free replacements. Late changes to a design are costly, unpredictable, and wasted manufacturing time.

What's more, EMA marketing director Greg Roberts says the directive has already caused several minor crises. In one, an OEM discovered a supplier had discontinued production of a leaded connector while retooling for a lead-free version. The OEM would not sanction a change and so scoured the country buying up every leaded connector with the original part number it could find. This is a temporary fix for the OEM, but Roberts wonders what happens with the next batch of equipment, or the next company that needs the leaded connector? Another problem is that just raising temperatures in reflow equipment is likely to damage components. And a few component suppliers are substituting lead-free items without changing part numbers.

The Directive, however, does not call for a total elimination of the six substances. “The directive mandates that homogeneous materials within compliant products, or materials that cannot be mechanically disjointed into different materials, contain less than the maximum concentration levels for the six substances,” says Roberts.

But because the required reflow temperatures in wave soldering ovens are headed up to accommodate lead-free replacements, all components on a printed circuit board should be reviewed to see if they are sufficiently temperature rated. Lead-free solders call for a reflow temperature about 25°C higher in the wave-soldering machines, so components will have to be more rugged. And as you probably expected, costs will also rise. Leaded solder bars, for example, cost about $2/lb, while a lead-free substitute will be about $8/lb.

Zulki Khan, president of Nexlogic Technologies Inc., San Jose, Calif., (nexlogic.com) suggests designers examine these several areas:

Laminates are board materials on which circuits are printed. “They are likely to change from conventional FR4 to materials referred to as FR406 and FR408,” says Khan. “These are fiberglass laminates with higher transition temperatures.”

Board surface finishes provide a solderable surface that keeps copper from oxidizing. The most used surface finishes are OSP (organic solder preservative), electroless nickel immersion gold, and immersion silver. All have been around for some time.

The finish depends on what the board is used for and the needed reliability of component joints and assemblies. For example, gold finishes are most reliable and durable but also cost most. They are recommended in military applications where reliability is of absolute importance. After gold in terms of cost comes immersion silver, then OSP, and lastly HASL. OSP performs similarly to bare copper. It contains no lead so it is gaining favor as a friend of the environment.

Solder paste is available in many nonleaded recipes, notes Khan. A widely used variation, SAC, contains varying amounts of tin (Sn), silver (Au), and copper. A frequently used variation is SAC 305. “It's somewhere in the range of 97% tin, 2% silver, and the rest copper. New solder also means using a flux with better wetting characteristics for the solders,” says Khan.

The thermal profile or temperature cycle governs how PCBs are processed. “Lead-free solder has a higher melting point than lead-based components,” adds Khan. “For instance, leaded solder has melt temperatures of 205 to 230°C, while lead-free solders melt at 230 to 255°C. Components should be at least rated for peak temperatures required by the solders. Solder stations doing rework will also operate with higher temperature tips. And if processed incorrectly, solder masses may peel or slightly resemble popcorn.

A view from contract manufacturers

Contract manufacturers are preparing for the looming deadline several ways. For instance, engineers at Nexlogic Technologies hired a consultant to audit company equipment and employee skill levels, and recommend new equipment and training. “On his recommendations, we purchased a wave-soldering machine, an automated optical inspection machine, and X-ray equipment for about $250,000, and began a retraining program for those involved in transitioning from leaded to lead-free PCBs,” says Khan. The company now maintains two production lines, one for leaded components and a lead-free line.

“Once we nail down the process for lead-free soldering, there should be little difference in production times,” says Khan. Such times will be more influenced by part availability. But be aware, cautions Khan, vendors might want 10-week lead times for some components.

Likewise, Roberts expects RoHS to directly affect the development and supply chain, such as purchasing, material control, marketing, all the way to R&D.

Even simple definitions, such as that for homogeneous materials has caused some confusion. It has been cleared up in draft guidelines published by the European Commission. There, they define a homogeneous material as one “that cannot be mechanically disjoined in to different materials”, such as PVC insulation on copper wire.

EMA Design's application engineer Gopu Achath says it should not be difficult to design lead-free PCBs because there is a sufficient variety of components available. The trick is to find the data that describes them and having it on hand when doing the design. The company has combined several software programs to make that possible. For instance, combining an online component database of some 47 million parts (about 6 million are RoHS compliant) with parametric search functions and schematic design software makes it easy to design lead-free, says Achath.

Most companies caution that there is no drop-in solution that meets RoHS, says Khan, and the transition to lead-free won't happen over night. “We'll need the process in place with the equipment and trained people. If someone wakes up on July 1 and expects products to pop out lead free, they'll be sadly disappointed.”

More than Europe

Don't think RoHS is only for Europe. California is initiating its own version of RoHs and some 20 states are planning similar directives. What's more, California's Electronic Waste Recycling Act of 2003 (SB20), is scheduled to take effect January 2007.

In addition, China's Regulation for Pollution Control of Electronic Products (RPCEP) is modeled after RoHS and WEEE but has even more restrictions. It's slated to go into effect around July 2006. In Japan, green procurement practices (JPSSI) have more stringent mandates than RoHS. And Taiwan, Korea, Canada, and Australia are initiating their own versions of RoHS.

RoHS' traveling companion

The hazardous substance mandate is not alone. In fact, an accompanying mandate, WEEE, for Waste of Electrical and Electronic Equipment, goes into effect December 31, 2006. It governs products sold after August 13, 2005 and was spawned by having to dump and recycle some 6 million tons of industrial waste each year. Manufacturers will have to handle collection of components such as PCB-containing capacitors, mercury-containing components, batteries, plastics, and more. Each manufacturer will be responsible for financing collections, treatments, recovery, and disposal of qualified waste.

The BIG BAD 6

For the time being, RoHS targets these heavy metals and flame retardants.

• Lead
• Mercury
• Cadmium
• Hexavalent chromium and the flame retardants
• Polybrominated biphenyl, PBB
• Polybrominated diphenyl ether, PBDE

The heavy metals must be reduced to 1,000 ppm, except for cadmium which must be reduced to 100 ppm. Military products are exempt.