Electronics > Projects, Designs, and Technical Stuff
Via in pad
OM222O:
Hi
I've been using the "via in pad" pretty extensively for different things, such as: reinforcing the screw mounting holes, connecting signals or power / gnd to chips while using the underside as a bus, etc.
So far I've had no issues with singal integrety, power issues,soldering components, or any other issues. Watching today's dave video about PCB layout practices made me wonder why he didn't recommend this method? Is there something wrong with them? It saves a ton of space when routing, especially on 4 layer boards where it basically eliminates all the power and ground routing.
voltsandjolts:
Only downside I am aware of is that via in pad can suck molten solder away from the pad-component joint and reduce reliability.
For manual soldering that doesn't apply, just add more solder.
TheUnnamedNewbie:
--- Quote from: OM222O on July 25, 2020, 09:38:42 am ---Hi
I've been using the "via in pad" pretty extensively for different things, such as: reinforcing the screw mounting holes, connecting signals or power / gnd to chips while using the underside as a bus, etc.
So far I've had no issues with singal integrety, power issues,soldering components, or any other issues. Watching today's dave video about PCB layout practices made me wonder why he didn't recommend this method? Is there something wrong with them? It saves a ton of space when routing, especially on 4 layer boards where it basically eliminates all the power and ground routing.
--- End quote ---
Dave, contrary to popular belief sometimes, is not the end-all-be-all expert in this kind of stuff. (nor is anyone else here, and I'm definitely not an expert- I just wanted to point out that you will always find differing opinions and practices depending on who you ask)
One problem you can get with via-in-pad, esp if you don't have plugged vias, is that on very small components, the amount of solder that wicks into the via can be significant and make the joint poor, or increase the likelyhood of tomb-stoning.
In my experience via-in-pad can be useful for high-density, but I've only used it a few times on bigger pads mostly for cooling. I've also done it with screw-mounting, but I don't really consider that via-in-pad, because it's not a true pad I'm soldering a component to.
One of the issues we do have on our high-density flip-chip components is that the presence of a via will actually influence the surface of the plated material, which can reduce our yield.
paul8f:
If that pad ever gets reworked, maybe there's a risk of the via going open cct?
(Just my own opinion, I've no evidence of this happening!)
I also agree with the other posters suggesting the wicking issue.
soFPG:
What does Via-In-Pad mean? Just an un-tented via right where the BGA-ball is?
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