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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