Dear Richard
We do not do ENIG - but my 2 bits - Issue is the PWB manufacturer's ability
to maintain ENIG in the window throughout the year. ENIG is good in sound
hands. The replenishments of Gold and other chem is periodic. So better
choose a fab with auto replenish and good control plan. ENIG failures are
many a times not across the whole batch hence difficult to detect but easier
to prevent at fab. Also there is an issue with layout which needs to be
adjusted for in the process by the fab I think.
Anil Kher
-----Original Message-----
From: Stadem, Richard D. [mailto:[log in to unmask]]
Sent: Wednesday, August 03, 2011 11:57 PM
Subject: Re: 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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