Hi
I've been using solder mask over reflowed tin/lead for about four years,
having almost no problems during assembly (IR reflow assembly).
Only problems I got were when heavy grounds appeared on CS or PS, and not in
inner layers.
For this purposes I use an epoxy based dry film solder mask.
If your customers agree I would use OSP or SMOBC, if they don't, you may try
giving a thinner Sn/PB and a double layer of SM.

Roberto Tulman
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Roberto Tulman
e-mail: [log in to unmask]
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