Steve,
I've seen exactly the same, but what looked like copper was indeed a very
thin layer of nickel, despite the coppery nuance. IF you had bare copper, of
course the solder would wet. Solder loves copper. What we found was this:
the gold was extremly thin and had not protected the underlying nickel, so,
the gold was solved instantly and the solder met at bad and oxidised nickel,
with other words dewetting. We tried RA and a lot of tricks, but it all got
worse, so we had to return several lots to the supplier. Try handsoldering
with a good flux. If it won't wet, you may have same problem as we had. If I
remember well, we got not explanation why only these throughs. The failure
type never reocurred.
Inge
----- Original Message -----
From: "Steve Gregory" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, September 20, 2006 5:47 PM
Subject: [TN] ENIG Problem...
Hi All!
Wouldn't you know it, all these postings about ENIG and all of a sudden
an issue just started happening with some ENIG boards we're building.
The problem is sporadic. We're building a double-sided SMT board using a
SAC 305 paste, and I haven't seen any non-wetting problems with the SMT
yet.
We're selective wave soldering using SN96 and a RMA flux, and after
about 250-300 boards my touch-up operators flagged me down and said that
they're seeing some boards that have through-hole pads that aren't
wetting no matter what they do. Here's some pictures:
http://stevezeva.homestead.com/files/Non_Wetting_Pads.jpg
http://stevezeva.homestead.com/files/Non_Wetting_Pads_2.jpg
http://stevezeva.homestead.com/files/Non_Wetting_Pads_Close.jpg
The pads look like bare copper...no nickle. Is this related to the
latest thread? Like I said I haven't seen any SMT with this issue (yet),
and it just started showing up...we've built a few hundred boards with
no problems until now.
I'm having the operators set the boards aside with the problem. Am I
pretty much hosed with these boards?
-Steve Gregory-
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