Hello Folks,
Got a big project done and goes into fab now. A surprise just popped up where the turn-key fab house said they can't get boards tin-lead plated and nickel-plated anymore. So we are going with gold immersion since some areas are mechanically contacted and thus can't have HASL. The rest could be HASL but that makes it complicated and black-pad isn't really an issue these days anymore.
Did nickel-plating become totally outlawed by now? How about Canada and other countries?
-- Regards, Joerg http://www.analogconsultants.com/
I don't think you would have a useful gold-plated board without a nickel barrier layer between the Cu and the Au, so I call B.S.
(AFAIUI, without a barrier, the copper atoms migrate through the few hundred atoms of gold and do bad things in a relatively short time)
Not so sure about that one:
There seem to be issues with lead-free solder but we won't use that.
I was puzzled in the past as well when Ni-Au was the usual process. Whenever I requested Ni-only lately there was balking. Back in the late
80's there never were any issues with that, we did it a lot. It was nice, you could also have parts of the chassis nickel-plated and thus had no dissimilar metals problems.-- Regards, Joerg http://www.analogconsultants.com/
But Joerg, you're not in the US -- you're in California :P.
Seriously, I'd try other fab houses before I gave up. Or try board vendors, and if you find one go back to the fab house and point out that board vendor X can do it, so why can't they buy from X?
-- Tim Wescott Control system and signal processing consulting www.wescottdesign.com
That page says that you can wirebond to a _heavy_ gold layer deposited over an electrolytic gold layer directly onto copper- not quite as good as Cu-Ni-Au, but acceptable.
Again, AFAIUI, heavy gold is not great for soldering- I remember dealing with some of the old Tek boards that had a very thick gold layer and the solder tended to fracture easily at the interface. Flash gold just disappears into the solder*. Even at today's bargain price of < $1,500 USD/oz, it's also not cheap.
Interesting note here:
.. pointing out that the usual (ferromagnetic) Ni layer causes increased losses, and that confining the nickel to selective areas such as contacts and pads can help mitigate the issue.
Best regards, Spehro Pefhany
-- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
You do NOT want to F with gold due to corrosion (purple plague) created by the inter-metallic potential (copper-gold) created.
"Joerg = Jerk "
** Nickel and tin are not " outlawed " anywhere.Lead based solder is outlawed in the EU - with exceptions for things like avionics and medical apps.
99% tin solder is the main alternative.Nickel plated connectors are used everywhere.
... Phil
Heavy gold is very bad for soldering, hand or machine.
It gets dissolved into the solder alloy and causes embrittlement.
Even mil contacts which have solder cups require that the assembler fill and release the solder tinning a couple times to release any loose gold molecules in the solder cup to tinning interface. That way, the solder joint does not get made with gold mixed into it, since you already suspended and released or wicked it out.
I have seen the differences and the embrittlement, and the broken contact leads. It is a real concern. The assembly steps are required since the contact gets plated evenly, and the desired gold thickness out on the pin or socket itself needs to be thicker, so that means one has to thin it in the area where the connection gets made.
It's AAPCB the turn-key house in Colorado. They usually try a fairly large number of PCB places.
-- Regards, Joerg http://www.analogconsultants.com/
Black pads issues? Those are long gone with controlled processes, I think. I have solder NiAu boards a lot, worked well. On this one I have to trust the circuit assembly house. It's a pretty big place, they should know because they'll get the heat (and lose a contract) if it doesn't work.
-- Regards, Joerg http://www.analogconsultants.com/
Yup.
The removal of gold from connector pins is mentioned in Procedure 7.
Best regards, Spehro Pefhany
-- "it's the network..." "The Journey is the reward" speff@interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com
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Then there is something deuced odd with this one response. Check a few board houses, if your responses are different challenge the assembler.
?-)
Well, we went with ENIG. Ni-only was not possible for whatever reason, even though that would merely be the leaving out of one step.
-- Regards, Joerg http://www.analogconsultants.com/
There's the Nicholson approach:-
Come to think of it, he never got his toast either.
Cool. But then my client wouldn't get any boards :-)
-- Regards, Joerg http://www.analogconsultants.com/
few
Amazing, or not. You got some short lived enviro-twit the first time.
?-)
Reminds me of a case where some sort of zinc plating was no longer allowed in California and we had to do it farther east. Heavy stuff, so there were regular truck transports back and forth. Picture Diesel plumes belching towards the sky at every steep pass when shifting gears. Which of course in its net effect was an environmental shot into the foot. Of course politicos cannot understand even such simple things.
-- Regards, Joerg http://www.analogconsultants.com/
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