Tony,
There are several consideration that have to be taken into account with
this type of process.  First, because you are applying the dry film to a
sever topography, you should be using a vacuum laminator to apply the
dry film.  Some companies apply the dry film with a HRL or CSL, but
inevitably they have seepage of the solutions under the resist along the
trace (soda straw effect).  Second, the gold plating should be as efficient
as possible to help with the success.  Third, the thickness of the dry film
should be greater than the plated circuit height.  Most companies are
using a 3 mil dry film for best success.

We normally recommend our Laminar GA30 for this type of application.  If
you would like to have more information please give me a call.
Ken Bridges - Dynachem

>>> Tony King <[log in to unmask]> 02/19/97
01:49am >>>

	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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