Michael,

We use ENIG on most of our boards with brass roll form swage standoffs plated with Electro Tin ASTM B545-13 Class A, B or C.  We then solder the standoff on both sides of the board whether it is purely mechanical or an electrical conductor.  Don't shoot me for using "non-standard" assembly practices.  Yes, tin and gold are a long way apart on the Galvanic scale.  If that is of concern you could get closer on the scale if you used Nickle plating on the brass standoffs.

For purely mechanical support we also use stainless steel threaded standoffs with stainless hardware.

Phil

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Giamis, Andy
Sent: Friday, May 27, 2016 11:06 AM
To: [log in to unmask]
Subject: Re: [TN] ENIG Board Finish with Tin Plated hardware

Hi Michael,
With electroplated Sn on your hardware, I'd first be concerned about whiskers.
If you are using electroplated Sn on hardware, have you ever had Sn whisker issues?  Is your hardware anywhere near active, leaded parts.

With Sn finish up against Au, I'd be worried about frit corrosion - but if all you have for Sn plating is mechanical fixtures (no electrical function), I don't think this would be an issue.
As a board finish, immersion Sn has its drawbacks, especially with shelf life and solderability.


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Kuczynski, Michael
Sent: Friday, May 27, 2016 9:44 AM
To: [log in to unmask]
Subject: [TN] ENIG Board Finish with Tin Plated hardware

We've been using ENIG finish for our PCB's and installing tin plated hardware (self clinching, broaching nuts and standoffs)

We use anywhere from 1 or 2 pieces, to maybe a dozen, of this hardware on various assemblies.
These items are used just to hold or mount some items in place (no serious stress on these items).

Our mfg/assy facility in EU is balking at the finish mismatch and suggesting we change the board finish to immersion tin (which we've never used).

We've built all these assemblies, many, many times without issue.

Is there any other merits I should consider, before I tell them please build them as is?


Michael Kuczynski
Mgr. ECADS - Electrical  511 Benedict Ave.
914-524-3118 (Ph)            Tarrytown, NY 10591
914-524-3322 (Fax)           Mail Stop P25-1-C
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