Conductive coating

[cpy911]

Hi,
I am looking for a conductive coating for Aluminum. So far, I have come up with electroless nickel plating, but have found it to be VERY expensive. Are there any other solutions out there that meet WEE and ROHS requirements?

TIA,
Justin

 

[sreid]

I don't know what WEE or ROHS specs are but Iridite is a common conductive aluminum coating. The generic name is "Chem Film" or "Clear Chem Film."

 

[YLWEA]

Have you considered any of the thermal-spray coatings? You can apply a very wide range of coatings (including conductive metallics) at a range of thicknesses and densities (different methods result in different % porosity)

 

[kenvlach]

WEE and RoHS are some of the health or environment-related standards resulting from the Workshop on the New Approach in Setting Product Standards for Safety, Environmental Protection and Human Health (Copenhagen, 29-30 November 2001).

http://www.mst.dk/udgiv/publications/2002/87-7972-191-5/html/default_eng.htm

RoHS = Restriction of Hazardous Substances
WEE = Waste Electrical and Electronic Equipment

Chemfilm would be ruled out due to the hexavalent chromium content. Also, it lacks abrasion resistance. Although you haven’t given many details, I think tin coating (either hot dipped or electroplated) may be the best choice. I have bought quite a few tin-coated Al terminals for power cables, and they have been very satisfactory. Don’t know your contact resistance requirements, but an electroless nickel surface gets very passive over time. Tin is better, as its oxide is a (semi)conductor. Also, tin is considered relatively non-hazardous (safe for food contact), whereas nickel can cause dermititis, has wastewater effluent limits ca. 1 mg/L, and some nickel compounds are considered carcinogenic (by the State of California, at least).

Hope this helps,
Ken

 

[cpy911]

Kenvlach,
You are right, the hexavalent chromium content in chemfilm makes it "verboten" for the EU. I am looking at tin coating now.

FYI,

We are looking for a solution to reduce EMI emissions from electronic enclosure systems. Each module that goes into our system must have a somewhat conductive surface. Anodizing is out, since it is non-conductive. Nickel plating turns out to be more expensive than the part itself, so that is out.

Thanks.
Justin

 

[funnelguy]

Is there a reason the modules could not be fabricated from clad aluminum? Would the pure Al skin provide sufficient resistance to oxidation? Certainly Kenvlach's tin suggestion would seem to meet all requirements.