This is not an issue if the plating is thick enough.
We make fairly complex boards, a regular repeat order  has the following features:-

FR4 material Tg 140
154 mils thick
8 layers
controlled impedance( microstrip and stripline)
hole sizes 12 mil to 380 mil maximum aspect ratio 12.5 : 1
large plated slots (slots and large holes peck drilled)
edge board plating
hot air solder levelling

Shadow direct plate system and pulse plating are in use.
The boards are for use in main frame computer systems.
There are more people doing this sort of thing than you would suppose.
The boards are assembled without special precautions.

Roger Hanmmond

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