Hi Richard,
The only things that come to mind:
Run wetting balance tests along with your traditional dip and look tests. Sometimes these curves point out "interesting" things before they happen to you in assembly.
After simulating your soldering processes in your message below, choose a mechanical shock test to see how well you formed that nickel-tin intermetallic bond!
Regarding XRF, make sure you have a good unit, follow IPC procedure, and make sure your calibration standard set matches the ENIG deposit you are measuring.
Best of luck
Gerry
----------------------------------------
> Date: Wed, 3 Aug 2011 13:26:32 -0500
> From: [log in to unmask]
> Subject: Re: [TN] Steps to take to prevent ENIG issues
> To: [log in to unmask]
>
> 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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