All,
We currently apply ENIG prior to soldermask, or should I say
our subcontractor recommended that we allow them to do so
to prevent "black pad". I was told that the reason being was because they recieve such a wide variety of different soldermasks from so many different board shops that their could be sross contamination. The boards we build are very expensive so we yielded their advice and have not had a solderability problem with a customer since. Sometimes trying to save a buck is not worth the effort.
I would rather have a satisfied customer than a few extra dollars saved, especially this day and age.
 
Tony Steinke
AIT-Atlanta Inc.
----- Original Message -----
From: [log in to unmask] href="mailto:[log in to unmask]">Damon DeSilva
To: [log in to unmask] href="mailto:[log in to unmask]">[log in to unmask]
Sent: Monday, July 22, 2002 11:47 AM
Subject: Re: [TN] Au-Ni coating

I suppose you could Au plate your entire panel prior to solder mask, if you like giving away $. Solder mask is applied prior too not as a post process.
 
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of [log in to unmask]
Sent: Monday, July 22, 2002 1:56 PM
To: [log in to unmask]; [log in to unmask]
Subject: Re: [TN] Au-Ni coating

Sorry, but in most cases the immersion gold process follows soldermask. We have a link to an article about black pad at http://www.protoengineering.com/immersion_gold.htm


At 08:39 AM 7/22/02, you wrote:
Bruce:

My understanding of Black Pad was it is caused by too much phosphorus in the nickel (as I recall) plating bath.
Solder mask contamination is a new one for me.
With mask going on after the gold, how does it contaminate the nickel? Mask should not come in contact with the nickel at all in my experience

I am interested in learning all nuances of black pad causation.
Would appreciate your comments.

Charlie McMahon

Misner, Bruce wrote:

Congratulations. Sounds like you are the proud owner of Black Pad
Disease or
better known as Black-line Nickel (BLN), an unpredictable low-level
defect
of ENIG. It has been traced to electroless nickel plating bath
contamination
by uncured soldermask, although I'm not convinced this is the only
cause.

Good Luck,
Bruce Misner


----------
From:         Marki
Sasportas[[log in to unmask]">SMTP:[log in to unmask]]
Reply To:     TechNet E-Mail Forum.;Marki Sasportas
Sent:         Monday, July 22,
2002 8:03 AM
To:   [log in to unmask]
Subject:      [TN] Au-Ni coating

Hello All,

I have problem in BGA rework, In some cases after, heating specific
zone
on
the board ( gold finish)
A near BGA joints are being defected. After taking off this BGA I
noticed
that some of the pads are black,
What can cause the problem?

Thanks in advance,
Sasportas Marki,
CreoScitex Corporation Ltd.

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