Tony
     
     We do Full body and selective Electroplated nickel / gold. As a 
     precaution we bake our panels at 250'F for 15 minutes after copper 
     plate or in the case of selective gold we bake after solder plate 
     before second image. The bake process if not controlled can make 
     subsequent dry film strip tougher. The process from 1st image through 
     gold plate must be done in a timely manner. No staging for 2-3 days 
     after image.
     We only do selective gold if circuits requiring gold are isolated. If 
     circuits are not isolated the etching process will reduce trace 
     thickness may even create opens at the butt line of the gold / copper 
     junction. We were successful once by nickel gold plating immediately 
     after solder strip but this is a dangerous process to let loose in a 
     production environment.
     I do not know of any hard electroless gold and I doubt that it is 
     possible. The only reliable source for electroless gold (soft) that I 
     know has yet to develop a temporary mask for a selective process.
     
     Kim
     [log in to unmask]
     


______________________________ Reply Separator _________________________________
Subject: Dry Film For Deep Gold Process
Author:  [log in to unmask] at SMTPLINK-HADCO
Date:    2/19/97 7:14 AM



 There are a variety of methods for
application of electrolytic nickel/gold
to printed circuit boards, most use a
buss connection to the features which
is removed at the routing or secondary
drill operations. The buss can be
internal or external however serves the
same function. Some designs do not
allow a buss type connection, it
becomes necessary to use the base foil
as the buss after pattern plate prior
to etch. A selective gold application
requires an additional coating of dry
film photo resist to cover all but the
features to be nickel/gold plated. The
nickel/gold process is very aggressive
on photo resist, causing film lifting
and under plate of nickel/gold under
the film.

 Does anyone in the manufacturing
industry know of a photo resist capable
to survive this process without 
lifting ? (double coat,image and
develop)

 How are other manufacturers coping
with nickel/gold application when buss
connections are not an option ? 

Electroless nickel/gold is an even more
aggressive process than the
electrolytic process, is there a
process to apply hard gold selectively
to boards with the electroless process?
What is used to mask the other portions
of the board ?

Tony King
Elexsys International Inc.
Nashua N.H.
[log in to unmask]
603-886-0066

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