Lead-free? Not so fast
Brad Thompson, Contributing Technical Editor -- Test & Measurement World, 10/1/2007 2:00:00 AM
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Lead surrounds us. Lead and other high-atomic-weight ingredients blended into CRTs’ glass funnels and faceplates help suppress soft x-radiation. Also, heirloom “crystal” glass wine goblets, vases, serving dishes, and paperweights in our homes contain lead.
In the 1920s, petroleum companies sold leaded gasoline to solve automobile-engine knock and valve-wear problems. Structural and decorative paints contained lead compounds, and lead pipes carried drinking water. Further back in time, lead sealed food cans and served as a component of pewter dishes. Romans used lead to solder water pipes.
Ahh, yes…solder. Now that RoHS and WEEE have kicked in, exotic alloys are supplanting tin-lead alloy solder in electrical and electronics applications. We’ve had a century of experience with tin-lead solder and thus understand its chemistry and behavior. Now, we’re switching to tin-silver solder and other formulations that we don’t understand as well. Tin propagates crystalline whisker growth, and silver forms interesting compounds with sulfur. The increased rigidity of tin-silver solder joints may cause fracture problems under thermal cycling.
I’m concerned that removal of lead from solder presents a reliability disaster in waiting—a wave of product failures caused by bad solder joints. I suppose that those of us in the electronics-test profession shouldn’t complain, as a new technology’s problems offer business opportunities and new generations of inspection instruments to play with. In the future, desktop x-ray solder-joint scanners may take their place alongside oscilloscopes as everyday test equipment.
To solve the electronics-lead problem, let’s encourage consumers to recycle castoff electronics and not toss them in the trash. Hefty rebates for recycled products will work better than education alone. Otherwise, failed and castoff silver-soldered products (and their byproducts) will end up in landfills and incinerators anyway.
If we truly understood the human cost and environmental damage inflicted by the products we use and discard every day, reuse and recycling wouldn’t be merely “good ideas”—they’d be sacraments.
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