Screaming Circuits: Getting on My Via-In-Pad Soapbox Again


Getting on My Via-In-Pad Soapbox Again

There's never enough time. There's never enough money. There's never enough room.

I certainly say those things often enough, and sometimes it's actually true. But other times, I'm just not looking in the right places. Here's a board that is pretty much plumb out of room. Everything is so tight that many of the vias have to be put in the pads. Well, maybe. Via holes in pads- how to fix-a

Take this IC footpront to the right. It needs a via to take a couple of connected pads to the other side of the pcb, but there isn't enough room between the IC and the part just below it. Naturally, the logical thing seemed to be to put the via in the pads. Unfortunately, doing so will make it difficult to get a good solder joint. The big open hole will wick solder down to the other side of the board.

Via holes in pads- how to fix-a-after At first glance there doesn't seem to be any thing to do. But upon closer examination, there is some unused space here. I'd just slide the part up a little bit as in the illustration on the left. Then move the via South a bit and connect it to the pads with a trace just long enough to accept some solder mask. The solder mask will stop the solder from chasing the via off the pad and getting sucked down.

Duane Benson
Some solder suckers sit South of Sunday


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That would be even easier. occam's razor

I'd just put it underneath the chip.

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