I have read all the stuff on black pad etc. and my advice would be to try
immersion tin. Immersion tin is an easier process for the board shop to
control and therefore you have lower odds of receiving a board with plating
problems. I would only use ENIG if you NEED it e.g. edge connectors etc.
Immersion silver I have seen go black and unsolderable, that was some time
ago though and things may have improved?!?!? I have never had a
solderability issue with an immersion tin PCB.
If I were you I would try immersion tin - in my experience it has as good a
shelf life as ENIG if stored reasonably and is much more reliable from an
assemblers point of view, because as you are finding it wastes a hell of a
lot of time when you get solderability problems just finding out who to
blame!!!
One other thing, I am no expert on ENIG (other than the heartaches it
causes) but I have had boards in the past with solderability problems due to
voids in the nickel plating allowing the copper and gold to diffuse
resulting in unsolderable finish - could you be seeing this??
Neil
-----Original Message-----
From: Kirsch, Clif [mailto:[log in to unmask]]
Sent: 02 October 2001 21:45
Subject: ENIG v Immersion Ag
We are running into solderability issues with ENIG boards, especially under
dense (500+ pins) BGA devices. Once the BGA is removed some of the pads
indicate they did not / will not wet.
Does anyone have experience with immersion silver finished boards from a
reliability and NEBS compliant standpoint? Also are there surface resistance
issues for test pads that are not reflowed with solder?
Clif Kirsch
Mfg Eng
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