Hi Francis,

        In the past, I have never experienced the problem of electroless not
plating on Copper. There are several possible reasons that I can envision.

        1.) Are you sure that the copper foil has the Antioxidant (usually a
Chromate treatment) removed? This is usually done by an acid or persulfate
microetch. If that treatment remains, it may inhibit the plating.

        2.)In consideration of the Catalytic steps, there is usually a rinse
following the Catalyst. The purpose of this rinse ( depending on the catalyst
you are using) is to Hydrolyze the Stannous/Palladium Chloride. This reaction
goes through a maximum with time and then begins to fall off. Two long a time
in this rinse will begin to remove the catalyst. Following this rinse is
usually an acid accelerator. The accelerator's purpose is two fold, 1) to strip
away the Stannous ions and 2) to reduce the Palladium Chloride to metallic
Palladium. This reaction also goes through a maximum with time: too long in
this bath will also strip away the palladium catalyst. In these latter cases,
I'm not quite sure that this should effect the ability to plate on copper.

        3.) Overstabilization of the electroless bath may tend to act like a
leveler in an acid copper bath. Since several electroless stabilizers contain
sulfide ions there may be a tendency to inhibit the plating at what would be
analogous to the high current density areas.

        For the most part, I would expect the first premise to be the problem.
I would be interested to know what you find out to be the real problem. ( I
never have ran up against this one before.)

Good Luck,
Les
>  From: Francis Lai <[log in to unmask]>, on 1/15/99 8:22 PM:
>  I experienced that electroless copper will plate more on teflon or fibre
>
>  glass than the copper surface on a panel. That is the PTH wall thickness
>
>  of electroless copper plated is more than that is plated on the surface
>
>  of the panel which is copper. PTH may have 65 u in. but the surface with
>
>  the final thickness of copper minus the original copper thickness is not
>
>  65 u in. Can any one help me with that?
>
>  Thanks!
>
>  my e-mail : [log in to unmask]
>
>  Francis
>
>  ################################################################
>  TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
>  ################################################################
>  To subscribe/unsubscribe, send a message to [log in to unmask] with following
>  text in the body:
>  To subscribe:   SUBSCRIBE TechNet <your full name>
>  To unsubscribe:   SIGNOFF TechNet
>  ################################################################
>  Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section
>  for additional information.
>  For technical support contact Hugo Scaramuzza at [log in to unmask] or
>  847-509-9700 ext.312
>  ################################################################
>
>

################################################################
TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c
################################################################
To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body:
To subscribe:   SUBSCRIBE TechNet <your full name>
To unsubscribe:   SIGNOFF TechNet 
################################################################
Please visit IPC's web site (http://www.ipc.org) "On-Line Services" section for additional information.
For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312
################################################################