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Q&A

Comments on Via on pad: acceptable or not?

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Via on pad: acceptable or not?

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I am designing a PCB with somewhat limited space. To save space, I am placing some vias on component pads. However, I am not sure if this is a good practice in PCB design. As far as I understand, there are certain pros and cons for such designs.

Pros

  • Lower impedance for circuits where this matters (RF).
  • Saves space on the PCB.

Cons

  • Wicks solder away if via is not plugged, affects reflow.

My layout contains vias that are directly placed on pads or at least intersect them (see example below, courtesy of Eurocircuits):

Via intersecting pad

Via directly on pad

However, it seems like big PCB houses (e.g. Eurocircuits) will offer plugging/filling of vias, eliminating the wicking concern. This makes the production more costly.

If the cost argument is not considered, what is the reason to use or not to use vias on component pads?

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1 comment thread

On the pad or very close to the pad? (4 comments)
On the pad or very close to the pad?
Lundin‭ wrote over 2 years ago

On the actual pad or very close to it? Could you post an example picture of the proposed via layout?

Mu3‭ wrote over 2 years ago

Lundin‭ the vias are placed on the pads or at the very least intersecting them. I will add the example pictures to the post.

Lundin‭ wrote over 2 years ago

Reason I ask is I've been in several projects where we placed the via more or less directly adjacent to a pad. Tight designs with 144QFP and similar. I don't know if it is actually good practice though, or if some tricks were used with solder masking or stencils. Though I don't recall the PCB vendor or the assembly contractor complaining about it.

Lundin‭ wrote over 2 years ago

That is, we did pretty much as in your upper left example picture.