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Vias Too Close To Pads Of The Same Net?, Why is it bad?

Hello,

why is it that putting a via near a pad of the same net makes a board non-manufacturable?

-Also, why is it bad practice?

I have been told to re-do a double-sided layout because i have a few 0.6mm/1.2mm vias just 0.1mm away from SMD resistor pads of the same net.

...the via "restring" is not touching the pad of the resistor....as i said, it is 0.1mm away...and in any case, it's of the same net.

(-the vias are 0.6mm drill, and 1.2mm overall diameter)

So do you know why this is a bad thing?

hpattie over 14 years ago

At a minimum, you want the space between the pad of the resistor, and the pad for the via to be large enough for a solder mask dam between them. This will prevent bridging. With the resistor pad and via on the same net, the bridging is not an electrical issue, however it would allow the via hole to wick solder away from the resistor pad, potentially creating a poor solder joint. Spacing standards vary from company to company. Check with your company for minimum spacing requirements. You might also check with you PCB fabricator on their minimum space to create the solder mask dam.
Regards,
Harold Pattie CID+
harold.pattie@ericsson.com
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