Hi Kathy! Think of any "passivated" metal surface as a surface which has
been intentionally changed or has naturally evolved (e.g. oxidation) into
surface that is nonreactive to a use environment. Two examples: stainless
steel can be passivated by an acid dip process which changes the surface
such that it is will not "rust" for certain use environments and copper
naturally grows an oxide which is passive for many use environments. The
level of passivity of a metal surface is dependent on the use environment
so don't assume a passive surface is immune to everything. Nickel forms a
very thin, coherent oxide which is very nonreactive to many use
environments. A passivated nickel surface doesn't accept additional plating
processes very elegantly and a passivated nickel surface requires pretty
active flux chemistries to allow acceptable solder processes. Most all
passivated metal surfaces can be "unpassivated" but the chemistries to
accomplish a task can be pretty ugly. I have some book references if you
are looking for a more in-depth answer. Hope this helps, good luck.
Dave Hillman
Rockwell Collins
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Kathy Kuhlow <[log in to unmask]>@ipc.org> on 02/07/2002 08:50:29 AM
Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond
to Kathy Kuhlow <[log in to unmask]>
Sent by: TechNet <[log in to unmask]>
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cc:
Subject: [TN] Nickel Passivation
What has actually happened to the nickel on a pad when it is passivated?
Can this nickel also be unpassivated?
TIA
Kathy
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