No surprise at all.
Assembly went through lead free SAC selective soldering. Thick, 20 internal
layers motherboard. Immersion silver plated.
Lots of connectors (not only), populated on both sides. Conventional 25um
copper in holes, outer layers over 1/2 oz copper.

Was soldered before with Sn/Pb.

No free meals, haha.

Want to redesign to ENIG - seems to be the only choice.

I wonder if there is a thumb rule for selecting the possibility of selective
soldering according to design and platings.

Also, if ENIG is safe for this process, even if rework with SAC ot Sn100 for
hole fill and shorts must be performed.

We will try to overcome the problem, in the meantime by using Nihon
superior, but in order to get good hole fill for such a thick board, the
parameters will be too harsh , I suppose.
Cross sections look very beautiful- pads are gone, knee is gone, barrel is
playing hide and seek, inner layers just end to nowhere.
How did you wise people validate this process and never mentioned anything
on the NET?



Gaby




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