Good morning from Spain,

I would like to know your opinion about a rework process requested by one
of our PCB suppliers once we rejected a lot of rigid multilayer gold plated
boards due to a non wetting problem. Boards are for class 3 applications
and they are bonded with adhesive to a metal plate (heat sink)

Solder paste didn’t wet the pads. Boards had a dark gold color, as if some
stuff was covered the board surface.

Our supplier has proposed the following method:

1/ Clean the boards @ 50ºC during 3 minutes with a solution of: degreasing
(5%)+ sulfuric acid (10%)+ deionized water (85%)

2/ Rinsing (water)

3/ Drying (air pressed + heat cabinet)

Our concern is if acid could be trapped into the vias (the board is bonded
to a metal plate) or if we could have any kind of problem in the future.

Thank you for your comments,

Juan T. Marugán López
Indra
Production Quality
Defense Electronic Equipment

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