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December 2000

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Subject:
From:
Russell Burdick <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Fri, 15 Dec 2000 11:19:27 -0700
Content-Type:
text/plain
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text/plain (63 lines)
I am a process engineer for a board manufacturer and am responsible for an
ENIG(electroless nickel/immersion gold) process. IPC-TM-650 (number
2.4.28.1) is the method we use to confirm adhesion of soldermask to copper
and gold to nickel both electroplated and electroless/immersion plated.

You are correct that the immersion gold finish should not be peeling from
the electroless nickel plate. The immersion gold peeling from the
electroless nickel is a one time problem I experienced. My first thoughts
were to blame the gold bath. Cooler heads prevailed and the electroless
nickel was examined. The result was that some of the  electroless nickel
bath organics were "killed off", the suspect was potential nitric acid
poisoning (nitric acid is used to strip the tank of nickel and to passivate
a stainless steel tank, if used). The gold solution would then severely
attack the nickel deposit resulting in non-adhesion.

The peeling gold disappeared when a new electroless nickel bath was
prepared(same gold bath as before).

Hopefully this is not too long a discussion, but it is what I have
experienced. I am not sure if peeling gold is any indication of a passive
nickel surface prior to immersion gold. Perhaps the chemistry vendors or
others can comment on that area.

Good luck and you may contact me if needed at:
602-276-1600
Russell Burdick, Process Engineer
Mosaic Printed Circuits

>From: ­J§»¶©\(allenhu\) Q80_5380              <[log in to unmask]>
>Reply-To: "TechNet E-Mail Forum." <[log in to unmask]>,
>­J§»¶©\(allenhu\) Q80_5380              <[log in to unmask]>
>To: [log in to unmask]
>Subject: [TN] tape test on the IMG surface
>Date: Fri, 15 Dec 2000 09:06:11 +0800
>
>Dear technetters,
>
>There are methods to test the adhesion of platings, markings or paints,that
>is, the tape test method.
>Someone told me that the tape testing should not apply on the IMG surface
>since the adhesion between electroless gold and nickel is weaker (because
>of its deposition characteristic)than other kinds of interface. So the IMG
>product failed in the tape test is normal.
>I can't agree his opinion but I can't proof myself that the TM-650 did not
>state that the tape test is able to test the IMG adheresion.
>Anyone who could advise the adheresion test of IMG or help me to proof
>"someone " is right or wrong will be deeply appreciate!
>
>Allen Hu

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