Vias don't go well in pads, of course. In fact, I think
it's fair to say that vias go as well in pads as large
igneous rocks go in peanut butter and jelly sandwiches.
But it's not just vias in pads that annoy people. Vias
near pads can be pretty much a nuisance too. In the SOIC pictured
here on the right, the pin 1 lead is at risk of having the solder
wicked off the pad and down into the via. If you've got to
have a via right near a pad like that, always make sure there is
something between the pad and the via that will keep the solder
away. A thin line of solder mask, or even silk screen, like with
the pads and vias on pins 12 and 14, will do. Anything to stop
the solder from going where you don't want it to go.
Duane Benson
Jersey barriers, perhaps?