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November 2002

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Subject:
From:
Don Vischulis <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Fri, 1 Nov 2002 11:53:50 -0600
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Victor-

I have three concerns about your situation:

1.  Copper migration through the gold.  Nickel is used as a barrier to
prevent migration.  I'm really not up on the theory regarding migration.
Possibly someone would care to add some facts about how fast or under what
conditions it occurs.

2.  If the deposit is used for a contact or connector surface the lack of
nickel will result in a short lived deposit.  Nickel acts as a hard surface
under gold that greatly extends the life of gold used as a contact surface.

3.  If the vias will be exposed to the plating solution (especially if they
are partially masked) there might be contamination or leakage from the vias
that would result in adhesion problems.

Hope this helps,

Don Vischulis

-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Victor Hernandez
Sent: Friday, November 01, 2002 7:23 AM
To: [log in to unmask]
Subject: [TN] Plating Au over Cu


Fellow TechNetters,

   Can you please share your concern with plating hard gold, 25 micro
inches, on fingers of a PCB over
an area adjacent to PTH's where some unplugged via exhibit SnPb.   I guess
my main concern is Au/SnPb.

Victor G. Hernandez

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