Hi Russ: Yes you are absolutely correct, passivation is definitely a cause
of poor plating adhesion, and probably the primary cause.
However in this case I think it falls within the oxidation/contamination
category that Rudy and Richard were referring to.
Since I was giving examples of other causes of plating adhesion besides
oxidation I didn't go into any detail on it, as it was already covered.
Just to throw out another one in the same passivation vain; excessive rinse
temperature either too hot or too cold after Ni plate can also result in
plating adhesion problems.
Regards
Mike Barmuta
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Russell Burdick
Sent: Tuesday, November 01, 2005 9:08 AM
To: [log in to unmask]
Subject: Re: [TN] Gold Plating Peeling...
Also consider for gold plate peeling off the base nickel can also be a
passivated nickel surface. Several ways to passivate nickel are: excessive
rinsing after nickel plating and prior to gold plating, excessive time left
in the air while trying to minimize amount of nickel bath drag out, nitric
acid fumes from nearby processes for plating rack strip solutions or tin
and/or tin-lead stripping area.
Passivation is not a visual characteristic so looking for it is not
possible. And excessive time or rinse after acid activation immediately
before gold plate can cause passivation.
Russ Burdick
>From: "Stadem, Richard" <[log in to unmask]>
>Reply-To: TechNet E-Mail Forum <[log in to unmask]>, "Stadem,
>Richard" <[log in to unmask]>
>To: [log in to unmask]
>Subject: Re: [TN] Gold Plating Peeling...
>Date: Tue, 1 Nov 2005 07:54:36 -0600
>
>Mike,
>This is really good information. I have run into gold peeling problems
>several times and because I do not have any pwb fab experience, I feel
>sort of helpless when I talk to the pwb vendor and they tell me they
>cannot be sure what caused the problem to happen. This list should be a
>good reference point from which to ask questions and make sure the
>process is controlled. Thank you for taking the time to put it together.
>What you have here is a Gold Tab FMEA!
>
>-----Original Message-----
>From: TechNet [mailto:[log in to unmask]] On Behalf Of R Sedlak
>Sent: Tuesday, November 01, 2005 7:44 AM
>To: [log in to unmask]
>Subject: Re: [TN] Gold Plating Peeling...
>
>Phew Mike, this level of insight and understanding was only earned
>through a LOT of pain and pressure... I am impressed!
>
>Rudy Sedlak
>
>"Barmuta, Mike" <[log in to unmask]> wrote:
>Hi Rudy and All: Careful on compartmentalizing the cause of peeling
>plating to only improper cleaning or oxidation. In general terms it's
>true that things like stripping, cleaning, surface preparation, rinsing
>and activation can result in peeling plating. Which I would include in
>your cleaning/oxidation category. However the list of overall causes is
>quite long.
>
>I know this doesn't really apply to Steve's original question, he's more
>concerned with the cure than the cause.
>
>FYI Here is a partial list of some other causes of plating adhesion on
>bussed Ni-Au that may be of value to those fighting this problem.
>
>Additional food for thought:
>
>* Improper sealing or conformance of the plating resist around the
>circuits.
>
>* Plating resist not compatible with the temperatures and chemistry of
>the preclean and plating process.
>
>* Plating resist not compatible with the gas evolution of the Au plate
>at the cathode.
>
>* Entering the plating at an incorrect amperage.
>
>* Malfunctioning rectifier.
>
>* Bad anode connections
>
>* Bad cathode connections
>
>* Incorrect anode/cathode ratio
>
>* Incorrect anode/cathode spacing.
>
>* Improper metal concentration in the plating bath
>
>* Organic contamination in the plating bath.
>
>* Trace metal contamination.
>
>* pH of plating bath out of specification.
>
>* Excessive brightner/leveler in the plating bath.
>
>I've spent many late Friday nights chasing these problems around the
>board shop after the dreaded scream "PEELERS" emanated from the QA dept.
>Why was it always Friday afternoon when they found them??
>
>
>Regards
>
>Michael Barmuta
>
>Staff Engineer
>
>Fluke Corp.
>
>Everett WA
>
>425-446-6076
>
>
>
>
>-----Original Message-----
>From: TechNet [ mailto:[log in to unmask]]On Behalf Of R Sedlak
>Sent: Friday, October 28, 2005 12:56 PM
>To: [log in to unmask]
>Subject: Re: [TN] Gold Plating Peeling...
>
>
>Steve: The usual cause of peeling plating is plating on to a
>dirty/oxized surface.
>
>Can it be reworked.... possibly, making sure that you get rid of the
>original problem which caused the problem initially.
>
>Can it be reworked in a way which is essentially guaranteed to work 99+%
>of the cases? Probably not.
>
>Perhaps some sort of incoming inspection/test might be worth
>considering?
>
>Rudy Sedlak
>RD Chemical Company
>
>Steve Gregory wrote:
>Well, I just got back from "Sin City", and as they say; "no rest for the
>wicked".
>
>I really wasn't that wicked, but I was confronted with a new problem
>this morning.
>
>We just built some assemblies and conformal coated them, but when they
>were being de-masked, the gold plating on the fingers started peeling
>up! Check out:
>
>
>http://www.stevezeva.homestead.com/files/Peeling_Plating.jpg
>
>http://www.stevezeva.homestead.com/files/Peeling_Plating_2.jpg
>
>I have a couple of questions:
>
>Can I repair this?
>
>If I repair this, should all fingers be stripped and repaired?
>
>Kind regards,
>
>-Steve Gregory-
>Senior Process Engineer
>LaBarge Incorporated
>Tulsa, Oklahoma
>(918) 459-2285
>(918) 459-2350 FAX
>__________________________________________________________________
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>and kindly notify the sender by reply e-mail.
>
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