Hi Kenneth,
I certainly agree with Vladimir that the choice of calling any of this 'Black Pad' is a bad one—it has caused confusion, including the 'disagreement' between Vladimir and myself.
I would be much happier with 1) 'Excess Phosphorous Concentration'--this is what most people call 'Black Pad;' 2) 'Insufficient Phosphorous Content'--this causes corrosion and cavitation in the nickel plating during the Au-plating process; 'De-Wetting' or 'Non-Wetting' which is what you get with poor Au plating not protecting the underlying nickel and thus the solderability of the Ni is compromised to some degree. Indeed, all of these can give a 'black' appearance at some stage or other.
Werner
-----Original Message-----
From: Igoshev, Vladimir <[log in to unmask]>
To: [log in to unmask]
Sent: Thu, 20 Nov 2008 10:40 pm
Subject: Re: [TN] black pad
Hi Kenneth,
I don't think such a "list" exist as there are quite a few reasons why ENIG pads
can look black.
In some cases it can be caused by the plating process (corrosion
streaks/cavitation in the layer of E-Ni) but this days it's a rare guest. In
some cases it's caused by overloading the joints, so when they crack - the
surface looks Black. It also can be poor Au plating, so one can see dewetted
pad, which also will look black.
The best way to deal with a specific case is to analyse it and figure out what
the root cause is.
Regards,
Vladimir
----- Original Message -----
From: TechNet <[log in to unmask]
>
To: [log in to unmask] <[log in to unmask]>
Sent: Thu Nov 20 20:45:02 2008
Subject: Re: [TN] black pad
ok experts...time for a definitive posting.
Black Pad is ? (any photos?)
Caused by:
1) ?
2) ?
Fixed By:
1) ?
2) ?
A little while back a new customer asked me what RoHS finish I prefer. I told
him that I liked ENIG for a few reasons
over silver or tin. He quickly asked me "Aren't you worried about black pad?"
Being that I recently had a tetanus shot and take a daily multi-vitamin
I thought I was in pretty good shape so I said that I was not worried about it.
That being said...I too would like to know more about this issue since I've used
gold finishes for many years now and have never had an issues with it. I've seen
soldering issues due to the type of solder used or thickness of gold but nothing
like this issue.
_____________________________________
Kenneth J. Wood
President
Saturn PCB Design, Inc. [log in to unmask]
2737 Bishop Lane Phone:(407) 340-2668
Deltona, Fl 32725 Fax: (386) 789-2765
www.saturnpcb.com
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier /*
Sent: Thursday, November 20, 2008 6:18 PM
To: [log in to unmask]
Subject: Re: [TN] black pad
Agreed, the prescription for the fix will be different.
Werner
-----Original Message-----
From: Igoshev, Vladimir <Vla
[log in to unmask]>
To: [log in to unmask]
Sent: Thu, 20 Nov 2008 5:52 pm
Subject: Re: [TN] black pad
Hi Werner,
I completely agree on what we disagree on :-)
I think that the same appearnce can (and is in that particuar case) be caused by
completely different phenomena, therefore the recepie to fix/avoid it will be
different.
Regards,
Vladimir
----- Original Message -----
From: TechNet <[log in to unmask]>
To: [log in to unmask] <[log in to unmask]>
Sent: Thu Nov 20 17:28:06 2008
Subject: Re: [TN] black pad
Hi Vladimir,
That is where we disagree--the definition of 'Black Pad.'
I define it as the phenomenon root cause regardless of what caused it--that is
not to say that who caused it is unimportant.
Werner
-----Original Message-----
From: Igoshev, Vladimir <[log in to unmask]>
To: [log in to unmask]
Sent: Thu, 20 Nov 2008 5:20 pm
Subject: RE: [TN] black pad
Hi Werner,
I should have referred to your exact phrase,
so you wouldn’t have to correct me J
As far as the definition of BP is
concerned, then I still prefer to define it as a manufacturing defect, which
has nothing to do with the assembly process.
The presence of thicker P-enriched layer
isn’t a good thing but in true cases of BP it’s normal
(thickn
ess-wise) but the joints has almost zero strength.
Regards,
Vladimir
=0
A
From:
[log in to unmask] [mailto:[log in to unmask]]
Sent: Thursday, November 20, 2008
5:06 PM
To: [log in to unmask]; Igoshev,
Vladimir
Subject: Re: [TN] black pad
Hi Vladimir,
I did not say 'excessive temperature'-- I said 'the more you expose
an ENIG layer to soldering temperatures'--that means multiple or lengthy
exposures.
If you define 'Black Pad' as the presence of P at the Ni/NiSn-IMC interlayer to
a degree significantly weakening that interface, then you can arrive at that
condition by
multiple paths.
One is faulty manufacturing, the other is excessive Ni-dissolution--of course,
these can work in combination.
Werner
-----Original
Message-----
From: Igoshev, Vladimir <[log in to unmask]>
To: [log in to unmask]
Sent: Thu, 20 Nov 2008 4:45 pm
Subject: Re: [TN] black pad
Well, with all due respect I would have to disagree with you Werner (not
for the first time :-)). I wouldn't associate Black Pad with excessive
soldering temperature. It's rather a board manufacturing related issue.
Regards,
Vladimir
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier /*
Sent: Thursday, November 20, 2008 4:38 PM
0A
To: [log in to unmask]
Subject: Re: [TN] black pad
The more you expose an ENIG layer to so
ldering temperatures, the more
Ni dissolves leaving more P at the layer between the Ni and the
NiSn-IMC. The more? P the weaker this interface, leading to 'Black Pad'
Werner
-----Original Message-----
From: henry rekers <[log in to unmask]>
To: [log in to unmask]
Sent: Thu, 20 Nov 2008 3:41 pm
Subject: Re: [TN] black pad
=0
A
Can you give me any examples of black pad being caused by anything other
than a
"bad board"? ie.? Is there anything in processing "perfect board" that
would
cause a de-wet condition that indicates black pad??? I guess where I'm
going is,
can this be anything other than a supplier issue?
--- On Thu, 11/20/08, Werner Engelmaier /* <[log in to unmask]> wrote:
From: Werner Engelmaier /* <[log in to unmask]>
Subject: Re: [TN] black pad
To: [log in to unmask]
Received: Thursday, November 20, 2008, 1:26 PM
Hi 'rekers,'
You canno
t broad-brush like this. Some FAB houses do quite well, others
not.
ENIG, from various sources and at various conditions, has shown
nickel
corrosion or high phosphide concentrations. The underlying reasons for
these are
different, actually diametrically opposed. Some are the fault of the FAB
house
others not.
Werner
-----Original Message-----
From: henry rekers <[log in to unmask]>
To: [log in to unmask]
Sent: Thu, 20 Nov 2008 12:45 pm
=0
A
Subject: [TN] black pad
Anybody out there experiencing mass dewetting issues from North American
board
shops?
?
From what I understand primary causes for dewetting (assuming the
reflow/wave
profile is bang on) is all on the board, ie nickel corrosion,
degeneration of
the nickel, or outgassing of the nickel/copper.? (I'm talking enig
here.)
?
Anybody?
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