Rick: I think what you are seeing is that the pattern plate is not continuos
due to electroless Cu voids in the holewall. Unfortunately you do not state
the magnitude or frequency of the problem so it makes it a little more of a
guessing game. You need to work back up line to see where this is occurring,
then correcting the cause of it.

 The first place to start is your electroless Cu line. Do you do any
backlight tests after electroless to verify good electroless coverage? If
not you should probably start. The fissure1 picture looks like poor
electroless coverage of the glass fibers. This can be caused by a laundry
list of various things, debris from plasma desmear, poor holewall
conditioning, insufficient catalization, slow electroless initiation, etc,
etc.

If you are getting consistently good electroless coverage verified by
backlight testing then you might want to look further along in the process.
Do you use a microetch in your electroplate pre-clean line? Excessive times
and/or chemistry in the microetch can give this same voiding effect.

I have also seen similar voiding when entering the Cu electroplate bath live
with full amperage. The first rack/flight bar of boards gets over amped and
blows out the electroless Cu causing voids.


Regards

Michael Barmuta

Staff Engineer

Fluke Corp.

Everett WA

425-446-6076



-----Original Message-----
From: Rick [mailto:[log in to unmask]]
Sent: Friday, January 24, 2003 11:27 AM
To: [log in to unmask]
Subject: [TN] plating voids


Technetters, has anyone seen anything like this before.

For background information we see this phenomenon on both
polyimide and FR-4 material.  The process is similar to both
material types:
Drill
Plasma Etch for desmear or etchback
Deburr (RO Water)
High pressure water wash (RO Water)
Electroless Copper (about 60 microinches)
Panel plate (Flash - about .25 mils)
Photo image, develop
Pattern Plate

The picture identified as Fissure1 was pulled out at pattern
plate (No thermal contact).
All other pictures were taken after full processing.

Rick Babyak
Process Engineer

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