I visited my fab house yesterday and according to them they do apply ENIG after solder mask application
but if there is a tenting/plugging of vias are required then that portion (of plugging) they do after
ENIG application.
I believe this should be a better solution as now solder won't go other side during reflow at assembly
house (via in pad). Engineering manager at assembly house said that most of flux will evaporate during
reflow and filler plus flux residue will be neutralized if not cleaned from the small vias using DI
water at wash.
Give me your thoughts
re,
ken patel
[log in to unmask] wrote:
> Hi, Ken,
>
> I believe ENIG (or any other plating) can be applied either before or after
> soldermask, but normally it's applied before to save on plating solution
> costs among other things.
>
> Yes, the immersion gold process is aggressive, so be sure your fab house is
> using an ENIG-compatible mask. This often involves using an alternative
> hardener in the mask mix, and it's better if your pads are not solder mask
> defined, as the plating tends to get underneath the edges.
>
> Masking from one side only, the holes can be cleaned, but it depends to a
> large extent on the diameter of the holes and the capability of your fab
> house. 10 mils and above, I believe, are OK, but smaller than that, the
> cleaning process may have trouble penetrating properly and cleaning out the
> bottom of the holes. I suggest you leave the holes open at both ends unless
> you absolutely have to mask one end.
>
> Peter
>
> Ken Patel
> <[log in to unmask] To: [log in to unmask]
> OM> cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST
> Sent by: Aero/ST Group)
> TechNet Subject: [TN] Fab Process question related to
> <[log in to unmask] ENIG
> ORG>
>
> 03/08/02
> 01:40 AM
> Please
> respond to
> "TechNet
> E-Mail
> Forum.";
> Please
> respond to
> Ken Patel
>
> At what stage the electroless nickel and immersion gold process is
> applied, is it after the solder mask application or before? I believe
> normally it is after the solder mask application but I want to verify
> it. I have heard that chemistry involved is very nasty if left on the
> board. If I plug or mask via holes from one side, I want to make sure
> that there is no residue left of that nasty chemistry. Can it be cleaned
> if mask from one end? Any comments?
>
> re,
> Ken Patel
>
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