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August 2001

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From:
"Creswick, Steven" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 22 Aug 2001 10:37:22 -0400
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Bill,

You should be able to get away with 30 microinches of gold.  I have gone
anywhere from 150-350 microinches of electroless, or electrolytic nickel
(subject to board layout constraints) with good success.

Word of caution - IMHO, if the board will sees multiple thermal excursions
(reflows - not to mention adhesive cure/s), and long WIP times (weeks)
before it gets to you, I would opt for heavy nickel, and going heavier on
the gold.  The reason for this is:  With each thermal excusion the base
copper tries to find pores/holes in the nickel to diffuse through/into.  If
successful, the gold is next.  Thermosonic gold bonding to corrupted gold is
problematic.  Thickness just delays the inevitable.  Nitrogen storage (at
least dry air) is assumed.

Steve Creswick - Gentex Corp



-----Original Message-----
From: Bill Christoffel [mailto:[log in to unmask]]
Sent: Wednesday, August 22, 2001 10:04 AM
To: [log in to unmask]
Subject: [TN] Ni/Au Plating Question


Ok all you plating guru's.......I am currently specifying a gold
(Thermosonic) wire bondable electrolytic gold for a new board design.
This in my mind was the easy part (Mil G-45204, Type III, Grade A, 40-50
microinches thick).    Now for the Nickel,   Currently we spec. a
Electrolytic Ni, 4-9% Phos., 150-200 microinches thick.

Questions:  Since my bonding is to the gold, is there a concern if the
Ni plating is Electroless or Electrolytic.  Which is easier to control ?
Which is a less expensive process ?  Any other concerns I should be
aware of ?

Thanks,
Bill C.

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