Lead-Free Conference Highlights Fabricators' Issues
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to Lead-Free Seminars pageRestriction of Hazardous Substances Directive
San Jose, CA. July 2005
As the RoHS (Restriction of Hazardous Substances Directive) compliance deadline approaches, it is becoming more difficult for PWB fabricators to deny that by this time next year, they must be prepared to manufacture lead-free printed circuit boards-or be out of business.To that end, several suppliers to the PWB industry have made it their mission to educate fabricators about the potential and pitfalls of incorporating lead-free manufacturing processes. Electrochemicals' vice president of marketing and strategic development, Michael Carano, welcomed approximately 37 attendees to San Jose, mostly PCB manufacturers and OEMs, eager to learn more about working with lead-free materials.
Are You Ready for Lead-Free?
In his presentation titled "Are You Ready for Lead-Free?" Carano provided an overview of lead-free and high performance lead-free materials that promise to change the way printed circuits are made. He also discussed desmear and metallization issues regarding high performance and lead-free laminates.Simply put, new materials (lower Dk, Df, greater Td) are more difficult to desmear, thus more difficult to metallize.
"Let's frame the issue," began Carano. "The implementation of lead-free is no laughing matter. It's like 'Alligators in the Sewers.' Two fabricators recently told me lead-free is more like a legend; it's not really going to happen. Well, it is going to happen, and it's happening now. Some of our Japanese colleagues are already [lead-free compliant]. Sony is already making electronics that are completely green. No lead, halogen."
Carano then led a discussion that dealt with the primary challenges when implementing lead-free manufacturing, including solderable surface finishes electroless nickel immersion gold, immersion silver, immersion tin, and high temperature OSPs. He also addressed several frustrating problems PWB manufacturers experience including the dreaded "black pad" phenomenon, small hole voiding, interconnect defects, and tin whiskers.
He summarized the issues of reliability and performance by stating that lead-free soldering temperatures will put more stress on interconnects, thus reducing fatigue strength. Strength, Carano argued, needs to be at the interconnect. Also, higher layer counts and an increase in 0.5 ounce foils dramatically shrink the reliability window. Finally, as boards become more sophisticated (blind and buried vias, high aspect ratio back panels, sequential laminations), the necessity of accurate testing will only increase.
Discussions on research
After a short break, an OMG Fidelity representative discussed reliability testing, and how board fabricators and their customers can learn from the research OMG and Electrochemicals have done in this area. Among the issues discussed, black pad was clearly a hot topic for several attendees in the room. "Everyone has their theories regarding how black pad comes about, but we think we've pinpointed it," said the OMG representative.He explained that the contributing factors to black pad formation include: the type of sulfur stabilizer used; and the use of lead as the metal stabilizer. In conjunction with a sulfur additive and/or excessive solution movement and aeration, the combination essentially forms a "bad actor." How to avoid black pad? Make the proper choice of sulfur stabilizer; lead-free electroless nickel; minimize solution movement; and avoid bath aeration.
At the end of the conference, Mike Freda of Sun Microsystems shared Sun's roadmap regarding lead-free compatibility and reliability issues. "All of our product moving forward will be lead-free," he warned. "We're planning on using immersion silver…. But on products for mixed metallization, we're looking at OSPs."
After the conference, guests were treated to cocktails and hors-d'oeuvre.
