Don Vischulis wrote:
>
> Tom:
>
> I've never tried to plate solder over nickel, but nickel does passivate rapidly when exposed to
> air.  Back when hand lines were used for plating nickel/gold edge connectors, it was well known
> that the nickel plate had to be activated by a dip into 10% to 15% sulfuric acid.  In your case,
> I'd recommend attempting to activate the nickel with an acid compatible with your plating bath
> (usually fluorboric or sulfonic depending on your bath).  A 2 to 3 minute immersion in the acid
> followed by a quick rinse and into the solder bath.  Given that sulfuric is normally supplied at
> 98% to 96% and the others are considerably weaker, you might have to experiment with the
> concentration.
>
> As I recall, the reason for acid activation between nickel and gold plating was removal of the
> organics used in the nickel bath as well as the prevention of oxidation.  If the activation step
> was inadequate, the gold would plate the tabs, but the end product would fail a tape test.
>
> Don Vischulis
> [log in to unmask]
>
> Tom Bresnan wrote:
>
> >      All:
> >
> >      Is there a preferred nickel I should be trying to plate solder on top
> >      of? We're struggling with plating tin lead on top of nickel and it's
> >      subsequent reflow after soldermask. Anyone have any suggestions? We're
> >      seeing dewetting and I'm wondering how many others out there are
> >      trying to do this. We currently use a nickel sulfamate bath, if that
> >      has any bearing... I'm not sure of activators and such, but if you
> >      think it's important, I'll find them.
> >
> >      Thanks in advance all...
> >
> >      Regards
> >
> >      Tom Bresnan
> >      [log in to unmask]
> >
> >      PS. Please respond direct to me as well as to the forum. I'm presently
> >      disconnected from the service.
>
> snip--------------------------
>
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Solder plating over nickel.....
  This is very  unusual and tin component of solder will not diffuse
to  Nickel to create metallic interface bond  and non-wetting will
 happened while reflow.
    Instad of Nickel , use TIN-NICKEL plating  and then solder plating
and reflow. Problem will be minimised.There must be good judgement
for solder platig and reflow technics. Wish you best of luck...
    Fulabhai Patel
    [log in to unmask]

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