In the belief that a proactive approach is the best way to take the lead out, the Solder Products Value Council of IPC (previously the Institute of Interconnecting and Packaging Electronic Circuits) has just released the first of two white papers on lead-free alloys. With power system requirements fast changing, though, widespread use of lead-free solders in the United States may still be some time in coming.
The white paper addresses round-robin testing of three variations of tin-silver-copper alloy, favored as a standard drop-in replacement for traditional lead-bearing solders. IPC found no statistical difference among the three front-runners (silver content varying from 3 to 4 percent, tin content between 95.5 and 96.5 percent) for melt characterization, wetting balance response and solder spread in surface-mount reflow application.
It's a bit unusual for suppliers, who normally field products to meet OEM requirements, to take the leader's role in such a hot area. But the subject of lead-free does reflect various environmental concerns long existent worldwide, although not too much here.
But the report isn't meant as a ringing endorsement for lead-free, said Tony Hilvers, IPC's vice president of industry programs. "The report is not saying 'you'd better use lead-free.' But what it hopes to say is that if you go that way, there's a body of evidence to support the reliability of lead-free solder," he said. Whether IPC will, in fact, be able to say this won't be known until early next year, pending completion of a second white paper on long-term reliability, including thermal shock and cycling.
Indeed, going lead-free doesn't even now seem automatic. That's especially true for power systems and boards with systems-on-a-chip, where high power densities are creating thermal problems of their own. System requirements will likely change faster than new solders can be formulated.
Most power vendors are involved in a lead-free developmental program, but they've made it clear that the new solders can't be applied if there's a sacrifice in reliability. Many still argue that only one-half of 1 percent of all applications use lead-type solders, and that the environment can easily handle it.
IPC's white paper is available free to qualified personnel at http: //leadfree.ipc.org/LeadFreeWP006.asp. A hard copy is also offered at $20 for members and $30 for nonmembers at www.ipc.org.
Vincent Biancomano covers power products for ProductWeek. Contact him at 103520.355@compuserve.com.
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