Paymon,
Sounds like it migh be skip plating to me - is the effect "random" ?- do
you have any bare boards? If so try baking a few out and see if the pad
surfaces discolor as gold dissolves into copper. Where you get nickel that
thin (unless the process is totally screwed up at the fab supplier) you also
tend to see pads where there is actually no nickel and the gold deposits
straight over the copper.
If you bake some bare boards out these will "discolor" which is a lot easier
that trying to XRF every pad on the board.
You did not mention if this was same in every board or if the problem takes
a random effect.
Hope you find root cause soon.........
Kind regards
John
John Burke
(408) 515 4992
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D.
Sent: Tuesday, February 12, 2008 2:45 PM
To: [log in to unmask]
Subject: Re: [TN] Through Hole Pad Solder Non-Wetting
No, it is not. Standard ENIG is optimally 150 uinches of nickel, with
between 3-6 uinches of gold over it, per the IPC spec. What Paymon has is
not ENIG.
Electroless Nickel Thickness APPENDIX 4 3.2.1
3 to 6 ìm
[118.1 to 236.2 ìin]
Immersion Gold Thickness APPENDIX 4 0
0.05 ìm minimum
[1.97 ìin minimum]
Paymon, if you in fact have only 1-3 uinches of nickel, you are really
screwed.
Even if you have 1-3 um of nickel, you are under the minimum of 3 um.
This will cause the copper to leach through the nickel and react with the
gold, and cause all kinds of solderability issues.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Igoshev, Vladimir
Sent: Tuesday, February 12, 2008 2:41 PM
To: [log in to unmask]
Subject: Re: [TN] Through Hole Pad Solder Non-Wetting
Sorry, I'm always confused with microinches and microns. :-( The thickness
is fine.
Vladimir
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Paymon Sani
Sent: Tuesday, February 12, 2008 2:30 PM
To: [log in to unmask]
Subject: [TN] Through Hole Pad Solder Non-Wetting
Hello All,
We experienced solder non-wetting to a PCB through-hole component pad
surface. The PCB surface finish is ENIG. The microsection results from the
suspect PCBs show that the Nickel plating is thin from 1 to 3 micro-inches.
We related the thin Nickel plating to Nickel corrosion and PCB surface
non-wetting. However, the microsection also revealed copper corrosion at
Copper to Nickel interface! I have never seen the copper corrosion in the
past and I would like to ask if any of you has a similar experience in the
past. What could be the cause of copper corrosion? I have few images if you
are interested to see them.
Regards,
Paymon
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