Frank,
Two thoughts:
1. Are your NPTHs drilled, run through electroless copper,
tented then etched out? If so, check to make sure you etch
all of the metal out of these holes before going through
'chemical' Ni/Au (is this electroless nickel, immersion
gold?)
2. Are you using a palladium catalyst on your electroless
Ni, immersion gold line? Leaving some of this catalyst in
the NPTHs will cause plate out in these holes. I've
certainly seen plateout on laminate areas with these
not-so-stable catalysts even with good rinsing after the
catalyst step. When this begins to happen, changing out the
catalyst seemed to be the only thing which worked to get rid
of this plateout.
To check out the second of these ideas, run some NPTH test
boards through the electroless nickel, immersion gold line
skipping the catalyst and catalyst rinse steps. If the
plating in NPTHs goes away, yet returns when you go through
the catalyst and rinse, you've come close to pinpointing the
source of your plateout.
I hope this helps.
Regards,
Dave Sullivan
Rockwell Collins, Inc.
[log in to unmask]
______________________________ Reply Separator _________________________________
Subject: chemical Ni/Au in NPTH.
Author: [log in to unmask] at ccmgw1
Date: 4/15/97 3:48 AM
Hello everybody,
Now and than we are seeing that chemical Ni/Au is covering the NPTH
wall. We and also the supplier of chemicals doesn't know what is causing
this phenomenon.
Is there somebody out there who does?
Any help would be appreciated.
Frank Petit
ACB
Belgium
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