Disrance between Via and pad

[Guest]

As IPC standard says we need to keep the distance between via and pad more than 0.5 mm. Because solder can migrate from pad to via.
Why most of the time you put the via very close the pad.

[robertferanec]

Do you mean unmasked VIAs? We mask (tent) all the VIAs. That helps to prevent solder to flow inside the VIA.

[Guest]

Hi ROBY,

If we do not defined the solder mask is it tent via?
when we do not use tent mask?

[robertferanec]

Some people like to tent VIAs, some not.

If you do not mask VIAs, you can easily use them as testpoints. Some people also say, they do not tent VIAs, because tenting VIAs may trap acid inside the VIA and after some time it may cause VIA damage (I am not sure about this claim, I am not sure if it is happening, when and how often .. I have never experienced that problem).

We tent VIAs, because it helps preventing to make short circuits (e.g. unmasked VIAs under BGA can make short circuit between a pad and an VIA, but also in different situations - simply just a small piece of solder can short circuit uncovered VIAs).

Tenting of VIA is defined directly on VIA (double click on VIA and look for "Force complete tenting on ...").