Nickel plating of aluminum for good EMC still ok?

Joerg,

If you care to do it yourself, check

Regards, Bill

Thanks, William, but it really needs to be contracted that out. If you do this somewhere back in the shop pretty soon the goons will swoop in and find out that you didn't get this, that and the other permit, environmental impact study or some other bureaucratic hurdle done.

ENIG is a common lead-free process surface finish, so the nickel part shouldn't be an issue. Consult IPC TechNet.

RL

Yes, that will probably be the way (sans the gold). This one doesn't have to be RoHS.

Why not alodine on the alum and solder coat or immersion gold on the board?

John

Solder coat would creep and also gunk up. Gold would be nice and is easily done at board fab, but would that jibe with alodine from a dissimilar elements point of view? This gear is going to be used in very harsh and aggressive climates.

The other thing I heard (rumors) about is that alodine is a nasty process.

Alodine is the cheapest aluminum coating, a simple dip process. It's conductive and somewhat protective - not as good as anodize - and it's a good base for paint. We alodine some covers, mask the contact zones, paint, and then unmask the conductive strips.

John

Not really. It is a chromate conversion process, and anything having to do with chromium compounds is somewhat nasty, but then again, so is making paint.

Jim

Alodine is what I recommend to clients in nearly all EMI cases because what I often find is that dreaded anodized aluminum. Looks very posh but the surface is completely non-coductive.

The question is how long an alodine/gold or alodine/nickel combination (panel/board) would stand in coastal climates and such. Maybe I should gold-plate the aluminum :-)

RFI finger stock?

John

With copper-beryllium? No way.

There are some stainless ones but finger stock isn't quite feasible in most cases. Typically, a circuit board must be mounted into some type of milled or cast aluminum part. Everybody seems to default to aluminum, for whatever reason. I usually prefer steel, cheaper, more robust, screw threads won't strip out.

Depends on the project but, for example, aircraft stuff is expected to last 30 years, at the least. It'll probably fly well in excess of half a century, which is likely past my own expiration date. So you don't want any onset of corrosion because of dissimilar metal surfaces.

What's wrong with beryllium copper? It's not like the beryllium is going to get loose.

Cheers

Phil Hobbs

If you go steel, that's easy to nickel plate. And you can have the PB edge traces nickel plated, too, with maybe gold flash. If you spec the whole board for nickel+immersion gold, you should be OK.

Nickel on steel looks good and is tough. We do some thickish n-on-s enclosure bottoms just to give them heft, so they won't slide around the bench when you push buttons.

John

Quote "Processes which generate particulate (dust, mist, fume) from the alloys, for example grinding, electro-discharge machining, welding or melting, can cause risk of sensitisation and chronic beryllium disease (CBD), a potentially serious lung disorder."

I believe the danger in normal handling and touching is related to areas that have oxydized a bit. At any rate, I never touch food or anything like that when at an EMC lab session before thoroughly washing my hands.

performance

Steel could be a tough sell in this case, plus we need to heat sink a few watts into it. Gold versus nickel would be a bit dissimilar as well I'd think.

We did it on aluminum sometimes. I remember my first EMI case. After solving it there were a few cosmetic changes as a consequence so a guy from S&M was called in to take a look. When he saw the new nickel plated front connector area his comment was "Wow! Shazam!".

performance

aluminum.

process.

You sure are pickey.

I've bought lots of military-looking microwave stuff at flea markets that had hogged-out aluminum blocks with regular PC boards bolted onto the cavities. Use a gasket on the cover and keep it clean and dry inside.

John

performance

aluminum.

any

or

very

process.

Yes :-)

I've had mil stuff on my desk made from some kind of cast material (zinc cast?). Tap it too hard with something and part of it turns into a gray powder. But yeah, a gasket is possible since I am dropping the power waste of the new design down to very few watts.

I don't think there are issues with alloys like beryllium copper. But I was always WAY cautious while sawing BeO substrates for thick film hybrids. Sawing under oil was a royal pain... I finally out-sourced that work when I ran the Dickson Electronics hybrid facility.

...Jim Thompson

performance

We recently had some issues with Fast-Transient tests on our base unit. Scraping paint from the mounting areas and line filter contact area solved the problem. To prevent corrosion we then had those areas plated with nickel. It was a dirt cheap solution and looks quite good.

In a former job we had the entire cover nickel plated. Conductive paint was far more expensive.