Hi Guy - well, we used to use electroplated SnPb as a standard printed
circuit board finish for years until the modern immersion type finishes
took over. However, we always reflowed/fused the electroplated SnPb
finishes (typically in peanut oil) as a non-fused electroplated SnPb finish
had poor solderability characteristics (i.e. oxidation). There is an "art"
to fusing an electrolplated SnPb surface finish uniformly. Perhaps what you
are observing is a supplier difference is their fusing process.

Dave Hillman
Collins Aerospace
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On Fri, Aug 2, 2019 at 3:07 PM Guy Ramsey <[log in to unmask]> wrote:

> One of our customers specifies electroplated tin-lead reflowed as a surface
> finish.
> It yields relatively nice flat pads and a good solderable finish.
> One of the drawings did not specify "reflowed". Everything seemed fine.
> Then, we had to switch vendors.
> The new vendor asked about this odd request for surface finish.
> Electroplated Sn-Pb, not reflowed.  But, they followed the drawing notes.
> Now, we have the boards in hand. They look bad. We are running a test print
> on the solder sample but I am dubious.
> Have any of you experience with electroplated Sn-Pb as a surface finish?
>