Dear Torben,

You neglected to say whether or not the voids are resin or predominantly on
the glass.(not to forget about the voids on the Kapton).
We have always experienced that an alkaline based(and free rinsing)
conditioner should help in this situation. Another thing to check is the
neutralizer step after permanganate. Not enough strength here will cause
voiding.

Another question,. When you do see the voids, are they in smaller holes, and
in the center, versus other parts of the barrel?

Is the low dep electroless copper solution overstabilized? Check out your
weight gains.

Good luck,


Mike Carano   

        -----Original Message-----
        From:   TOE /Torben Østeraa [SMTP:[log in to unmask]]
        Sent:   Tuesday, June 29, 1999 2:26 PM
        To:     [log in to unmask]
        Subject:        [TN] Voiding, through plating, conventional

        Dear collegues, 
         
        I have run into a problem of sporadic ' voiding ' in my through
plating 
        process. the problem has the following characteristics:
        - is observed a few times per month
        - affects all materials ( fr4, bt/epoxy, kapton, GI, teflon[s] )
        - on kapton-containing builds ( i.e. rigid-flex ) , voiding takes
place
        predominantly
         on the kapton surfaces. Typically, all the kapton is without
coverage.
        - I have not (yet ) ben able to establish any correlation with time
of day, 
        batch maintenance or other obvious influences
        - Is independent of type of desmear, plasma or permanganate, even
        kombinations
        have failed. Therefore,  point of my focus at the pth-line itself.
        - The obvious cause would be under catalysation, so an alkaline
substitute
        for my 
        present acid conditioner has been tried. Nice results, but the
expected poor
        hole wall
        adhesions is just not good enough to prevent excessive
hole-wall-pullaway
        during HASL.
        - Supplier is no help ( sorry to say.... ).
         
        - Line chemistry is Shipley, Cleaner/cond 815 ( acid) , Etch 3330 (
        persulfate/acid stabil. ).
        Catalyst 3344 + predip 3340, Accel 19H, copper Cuposit 328 (
'classic' low
        build ), Acid strike 4 microns. 
        - Water rinses are all 'fresh' tap-water. ( good quality in our part
of the
        world )
         
        Any advice or hint in this matter is highly welcome
         
        regards
         
        Torben Østeraa
        Printca AS
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