I have a question

[thu96]

For those of you that design PCBs, I have a silly question: why do some PCB manufacturers allow vias to touch / intersect with SMD component pads, while others do not?

I have been using iTead for a while, and I've been under the impression that the shorter the better re: any connection to a ground plane. Hence I have been using two 13 mil vias with every GND pad for a decoupling capacitor for example to connect it to the GND plane on the other side of the pcb.

However, the design rules for OSH PARK consider this a no no. Compliant designs require that GND pads are not intersected / touched by vias.

So why is it that iTead can make a PCB with a via that touches the solder pad while OSH Park objects to this approach? I am sure there is a reason... And should I change my boards to reflect the OSH PARK way?

 

[Geomancer]

It's simply a process thing. Blind/buried vias are more complex to manufacture than a regular via.

You want to minimize everything, not just ground connections. The positive end of a decoupling cap needs to be kept short too.

The difference between a via in a pad, and a via next to a pad isn't going to make a huge difference though in most designs.

OSH Park isn't the be all, end all. They're simply a very easy to use, US based board house that makes good quality boards. Their prices are also reasonable for small boards, but for larger boards not so much. You'll almost always get a better price going to China, but your mileage may very in terms of quality.

I created a board in KiCAD and went through the OSH Park process and was pleasantly surprised how easy it was. They showed images of exactly what the board would look like, including silk screen, which was a nice verification step that my file was read correctly.