Read an interesting article tonight about the implications of removing lead from solder to keep it out of our landfills. It seems that lead was alloyed with tin in solder in the first place to prevent "whiskering", where small hairlike filaments naturally grow out from the surface of the soldered joint, similar to rust or other corrosion. It's not completely understood why tin and a few other metals used in soldering do this in the first place, but alloying the metals with lead eliminates the problem. When the whiskers grow long enough to come into contact with the nearest neighbor's soldered joint on a circuit board, it results in.. yep.. a dead short. Seems the problem affects most of the alternative alloys proposed or mandated by "green" legislation in various countries (including the United States, most recently). So the price goes up and the MTBF (mean time between failures) drops to half that of things made with lead based solder due to whiskering. Just a heads up- it will be interesting to see in the coming years how this affects the work we do .. commerical lighting control boards come to mind, as well as the myriad types of dimmers, photocells, and various other devices we work with. It will probably take a good year before the existing stock of products made with leaded solder are sold off the shelf and all that is left are products made with the new lead free alternatives. I suppose it will become a script we have to memorize, explaining to customers why their expensive electronic device failed so quickly. Whiskering also begins from the time of manufacture, so maybe we will need freshness dates on the things we buy, similar to milk, cheese or beer.
A link to a NASA article on problems they have had with whiskering and some good pictures of what it is and what it looks like:
Time will tell... leaded solder was banned from commercial use in the EU at least one year ago and so far I haven't heard of a spectacular rise in equipment failures. I do know development of new technologies was problematic at first, but it seems to have worked out by now (I know a bunch of people whe experimented with lead free soldering of photovoltaic cell and concluded proper flux is the key to success.)
Tin whiskering isn't the only problem with the new solder formulations. The lead-free alloys tend to be much more brittle than the standard Sn/Pb solder, and the joints tend to crack with repeated heat/cool cycles. The problem is exacerbated by the use of surface mount components, which have no wire leads to absorb the stress.
Microsoft is learning about this the hard way with massive field failures on their "X-box 360" videogame systems. The lead free solder joints are failing, prompting LOTS of warranty repairs.
Conventional tin/lead solder can still be sold here for "special" purposes, so fortunately those of us who want to keep on using it for repairing vintage radio equipment are still O.K. for the moment. It's getting harder to find sources though.
If they ever decide to completely ban lead in solder, I think we'll be back to stockpiling as much as we can afford. Better make room alongside all those boxes of filament lamps!
I think this became an issue when people started realizing the impact of throwaway electronics. Nobody fixes anything these days, you throw it away and buy a new one so a lot more lead is finding it's way into the waste stream. Unfortunately some of these widgets are not even lasting long enough to survive their short design life
Unfortunately, with the reliability problems caused by the lead-free solder, there will probably end up being even MORE junked electronics headed for landfills in the future. If the manufacturers can get the solder joints to hold together long enough to get through the 90 day warranty, then failures after that just help ensure the sale of MORE cheap Chinese TVs and DVD players.
Wait until analog TV goes dark in the US next year--the curbsides are going to be flooded with discarded sets...