We have had the following problems
Thin Nickel
Porous Gold
Peeling Gold
Nickel Creep
Skip plating (due to BGA area having remnant electrolyte in the vias)
Nickel passivation
Discolouration
And currently poor solderability where the tests performed by the
supplier say the board is perfect but NPL say it isn't and our process
definitely say it isn't. Currently the cause is unknown apart from the
accusation that we caused the problem.
These problems have been with different suppliers some of which have
supplied for years without a problem and then they will throw in a curve
ball just to remind us that ENIG is the pits. We do not buy at the
lowest price although cost is very much on our minds.
We do inspect at GIG, we do a tape test which really shouldn't find
problems but does. We inspect for the other visible problem.
If I was free to add a test I would add a coalescence test on a
salvedges coupon (1st & 2nd side). That would indicate in a quantative
way any change in solderability.
Regards
Rex
PS Thanks to those on the forum that have emailed me directly concerning
our problem. If there is bottom to it, I will see if I can share :-)
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: 03 August 2011 19:27
To: [log in to unmask]
Subject: Re: [TN] Steps to take to prevent ENIG issues
Boy, I cannot tell all of you how much I appreciate all of your
responses.
Now for the tougher part of the question:
What methods can be used to DETECT the ENIG plating issues in-house,
before the PWB ever gets to the manufacturing floor? Some things I can
think of are:
Use EDS/XrF testing per Appendix 4 of IPC 4552 to determine the
thickness of ENIG. This would help indicate that there may be issues
Use a solder test coupon of a particular design (board from Hell) with
SMT parts on both sides plus subsequent through-hole parts to be
hand-soldered and a single component to be hot-gas reworked to simulate
the conditions that the production boards will go through, such that if
one or two coupons are quickly assembled, reworked, and hand soldered
with a couple of bakes thrown in, and no issues are seen, one can
reasonably assume the rest of the production lot will also be good.
Use a coupon and run it through two reflow profiles, a selective solder
pass, and then solder only a handful of PTH and SMT components, and then
subject it to 15 thermal cycles of say -40 to +125 C to test for issues
before releasing the lot of PWBs. This would detect the failures of
delayed P-rich level, which typically show up later after soldering and
test are complete.
Any other ideas? Tell me your thoughts. Yes, I know some cost is
involved, but I need to know what tests would provide the best cost
versus assurance.
For those of us who either must use or prefer to use ENIG, but want to
prevent any issues from showing up, well, we all benefit here.
From: Reuven Rokah [mailto:[log in to unmask]]
Sent: Wednesday, August 03, 2011 12:17 PM
To: TechNet E-Mail Forum; Stadem, Richard D.
Subject: Re: [TN] Steps to take to prevent ENIG issues
Choose a reliable source and not jump from source to source searching
for better prices only...
Reuven
On Wed, Aug 3, 2011 at 6:16 PM, Stadem, Richard D.
<[log in to unmask]<mailto:[log in to unmask]>> wrote:
I have a client who is switching PWB fabricators for ENIG finishes. They
are fully aware of ENIG issues such as Black Pad, Brittle Nickel, etc.,
and want to know whatever steps can be taken to prevent ENIG PWBs from
reaching production with these issues.
Does anyone have any suggestions?
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