Hi Murray - if you can get a true ENIG plating chemistry to put 15
inches of gold thickness on a board, you would never want to use the board
as the gold plating would have severe structure and/or solderability
issues. The IPC-4552 specification contains the industry consensus gold
plating thickness range that applies to producing an acceptable and
reliable ENIG plating layer. Any gold plating thickness outside of that
range would be questionable at best for quality and reliability unless you
are working closely with a plating chemistry supplier who is doing a custom
plating bath composition. One of the early issues of ENIG plating was the
industry asking the plating chemistry suppliers to provide an immersion
gold plating thickness that exceeded the acceptable physics of the plating
chemistry (basically this is how we discovered "black pad"!).

Dave Hillman
Collins Aerospace
[log in to unmask]

On Fri, Jan 3, 2020 at 3:30 PM Campbell, Murray <[log in to unmask]>
wrote:

> Happy New Year All,
>
> Is there any good reason to call out a maximum gold thickness / nickel
> thickness on fab notes or is it sufficient to rely on simply stating that
> the fabricator shall follow ipc-4552 minimum thickness?  I have seen some
> companies state that a maximum thickness upwards of 15 µin to be
> acceptable.  Is there any value in stating an upper range?
> I know it states in 4552 that an upper range had been debated and not
> necessary but I still see an upper added to fab notes.
>
> Regards,
>
> Murray Campbell
> PCB Design Specialist
> [log in to unmask]<mailto:[log in to unmask]>
> [cid:[log in to unmask]]
>
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