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RoHS compliant tin/lead plating
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Tin-lead alloys were used as contact finishes before. It seems that nowadays, contact finishes are almost noble metals. Are there any tin-lead plated connectors in manufacturing and in use? If so, could you give me some real examples? And how big is the market share? Since lead-free solder is expected to replace tin-lead solder in electronic industry, will this affect the field of connectors?
Ji Wu- College Park, Maryland, USA
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Is tin/lead plating (maximum 97% tin and 3% minimum lead) RoHS compliant?
Jim Dawsonplating & finishing is a process within our manufacturing facility - Cincinnati, Ohio, USA
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I'm working very hard on understanding this. I'm still not there. I see your letter has gone unanswered for a while, so I'll run this up the flagpole...and see who shoots it full of holes. Take what I say with a grain of salt.
The rule is, as far as I can understand, that not more than 0.1% of any "homogenous" part can consist of lead. A plated coating is not considered "homogenous" in that it's not something you can unscrew - it's part of the metal.
So, I suppose you would determine the thickness of the coating, the density of the alloy, then, the surface area of the part. Now, you have the weight of the coating...multiply by 0.03, now, you have the weight of the lead.
Now, weigh the whole component, and divide the weight of the lead by that weight. If the number is less than 0.001, it's compliant. If it's greater, it's not. That is what I think it all means, anyway.
There are numerous exemptions. They are also still arguing about what's "homogenous."
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Dave Wichern - The Bronx, New York |
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Dave, that seems a long way of saying 3% lead exceeds 0.1% lead so non-RoHS.
Jim, there are exemptions to the 0.1% lead limit, but probably none applies. See the Global Automotive Declarable Substance List (GADSL), which includes both RoHS & ELV, at http://www.gadsl.org
Exemptions include free-machining alloys and critical electronics applications in aerospace and computers. Some exemptions are being phased out as replacements are developed. Intel uses a 5% Pb solder on present CPU chips but has announced next generation, 0.45 nm chips will use a new, Pb-free solder.
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Ken Vlach - Goleta, California |
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Not only was it long, Ken, it was wrong.
Apparently plated coatings are considered to be a "homogenous" part, because they can be physically separated from the substrate. So, the answer to the original posters question is pretty definitely 'no', unless it falls under one of those exemptions.
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Dave Wichern - The Bronx, New York |
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Hi, Dave. No one can fault you for your difficulty in accepting this weird definition of "homogeneous" :-) The goals of RoHS are obvious and probably admirable, but getting there involves really weird definitions of words, whereby a chromate conversion coating that is easily rubbed off the plating with a pencil eraser is considered homogeneous with the plating, but plating that can't be removed with a chisel is considered to be not homogeneous with the part :-) They want people to stop using lead and hexavalent chromium, and it may be best to ask Ji and Jim to simply accept it that way because words will be continuously redefined as necessary to achieve that end. Regards,
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