45031

RoHS compliant tin/lead plating [Ohio] 

May 7, 2007

Is tin/lead plating (maximum 97% tin and 3% minimum lead) RoHS compliant?

Jim Dawson
plating & finishing is a process within our manufacturing facility - Cincinnati, OH, USA

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."

Dave Wichern - Bronx, NY, USA

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.

Ken Vlach - Goleta, California

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 definately 'no', unless it falls under one of those exemptions

Dave Wichern
- Bronx, NY, USA