Question

Could somebody explain to me what an Antipad is on a circuit board? I don't quite understand nor see in a diagram *what* an antipad is, exactly.

Answer 1

have you done a search for "antipad"?

Answer 2

Yes, I have, that isn't helping me get an adequate explanation.

Answer 3

Look up via PCB. Here is a link:
http://en.wikipedia.org/wiki/Via_%28electronics%29

Answer 4

I guess should put it this way: I've been doing lots of searches and reading on it, and I still don't understand, overwhelmingly due to what I think is poor phrasing on part of authors, what an antipad physically is. Is it just vacuum/dielectric in between the copper via and the circuit board, or is it made of something? Some diagrams show it as if it might be a physical thing, others show it like it might just be a sort of air buffer zone in between the circuit board and the via.

Is an antipad a physical object, or is it used to describe the air gap in between the via tube and the circuit board? Is that what a "clearance hole" (have bones to pick with that, too) is?

This is my current understanding: http://i.imgur.com/tP7C2jD.png

Answer 5

This link is to a PDF document which, I think, gives a lucid description of what an antipad can be. I believe you have already formed a pretty good idea of what it is and what it can do. (impedance matching-trimming etc.).. You are already aware of what physical dimensions can do when dealing with a high or very high frequency.
http://www.basebandhub.com/pdfs/antipads.pdf

Answer 6

Thanks so much! This is probably the best description I've seen so far of antipads.

Answer 7

You're welcome. I must admit, I have spent hours at Pace soldering station working on PCB for an AN/FYQ-49, and never knew about anti-pads. However, I now can see how with high frequencies and low signal levels they play a role in getting the signal there where it is needed.