Torben: As you probably know the problems with resist lift during Ni/Au
electroplate have been an ongoing problem for years. Let me offer a few
things to consider.

1. Surface preparation prior to photoresist application. If you are applying
this over electroless Cu, use an acidified anti-tarnish after the
electroless. If you are applying onto foil or after strike plate use an
mechanical abrasive prep.

2. If possible use a semi aqueous photoresist. However these are becoming
rarer and rarer due to environmental issues.

3. Preclean prior to plate. If you are using a soak cleaner make sure it's
chemistry is compatible with the resist. Also excessive
times/temps/concentrations can cause lifting.

4. Au bath. Keep the Au conc. up in the 1oz/gal range. Use a bath with a
high plating efficiency, around 50%. The bath should be carbon treated on a
regular basis. Use a wetter to reduce surface tension. Use a solution
sparger across the face of the panel to scavenge off the hydrogen. All of
these things will help reduce the resist lift problems.

Since you are using sub-contractors for the plating some of these items may
be hard to implement or negotiate. Good Luck!

	
Regards
	
Michael Barmuta
	
Staff Engineer
	
Fluke Corp.
	
Everett Wa.
	
425-356-6076

                                                                	




-----Original Message-----
From: TOE /Torben Østeraa [mailto:[log in to unmask]]
Sent: Friday, August 13, 1999 2:45 AM
To: [log in to unmask]
Subject: [TN] Gold plating resist


Dear collegues, 

When producing strip-line boards with Nickle/Hard-gold as etch-resist, it is
a well
known problem that the hydrogen generation in the plating baths can
sometimes
cause lifting of the photoresist. This results in plating of nickle and/or
gold under
the resist.
Some tricks are known ( or at least told )  to minimize the problem, e,g,
baking or
UV bumping prior plating and reducing current densities.
Still, I find the proces far to unpredictable and  am thefore seeking advise
on this problem. 
Does brand of photoresist make a difference?. Several plating houses have
had
best experiences with a product from german 'Hoechst', but this is not
available anymore.

We are using sub-contractors for the plating proces, but apply the plating
resist
ourselves. 

Sorry if this problem has been on this forum resently, but perhaps new
information
is available today?....

regards

Torben Østeraa
tech. mgr.
Printca AS
Denmark

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