Bill,
While the gurus are quarreling about black pad definition, I try to see if there is a logical alternative. You said that you soldered only ONE side, the backside. And the topside was NOT soldered, is that right? I remember we had a similar problem many, many years ago. What happened then was this: the Immersion Gold was nearly non-existent, and the underlying nickel plating was not the best either. So, when we mounted the topside, after having soldered the backside, and ran the boards through the oven, the solder melted, wetted on the Immersion Gold, but after the gold was consumed and the solder was expected to wet on the nickel, there was no proper wetting, so the solder withdraw, or with other word, dewetted. When the backside was soldered, the topside ENIG was degraded, i.e. the nickel was oxidized. There was nothing we could do about it, other than send back the boards. There were many tours before our board supplier got a proper process control.
Inge
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of [log in to unmask]
Sent: onsdag 21 oktober 2009 01:21
To: [log in to unmask]
Subject: [TN] ENIG Issue
Fellow TechNetters: I ran into a problem and I am looking for more information. We had some PCB made with ENIG for SMT applications. We populated the backside, ran them through the convection oven, the solder fillets were fine. Populated the first five (5) PCBs on the topside, ran them through the convection oven, and the solder fillets were quite bad, actually dewetted. Could not even be touched up. Tried two (2) more random PCBs and got the same results. Never have run into this before but have been told it is NOT a unique problem. Has anybody had this happen? Have to tell our customer that they are not going to be getting their PCBs on time and would rather not look like the north end of a southbound mule.
Thanks in advance for your assistance.
Bill Black
1 631 667 9699 X13
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