[SI-LIST] ROOKIE: Anti-Pad Size Effect On Signal Integrity
- From: "Clarke, Paul" <PaulClarke@xxxxxxxxxxxxx>
- To: "'si-list@xxxxxxxxxxxxx'" <si-list@xxxxxxxxxxxxx>
- Date: Mon, 11 Dec 2006 16:24:53 -0500
Hello,
Before you read the question please keep in mind that I am just a lowly
Mechanical guy that has better odds of selecting the right bolt than I do
designing an LED circuit.
I have a question about how the size of an anti-pad can effect signal
integrity. The example application could be a backplane @ 5, 10, 20, 40, or
80 [G] (I am asking for this range because I anticipate the answer may
depend on the speed).
If you have a BP via for a signal pair of .025" with a pad of .044", how
much impact can an antipad have on the impendance through a range of sizes
of let's say .054-.060"? Center-Center distance could be 2.1 [mm].
In the case described above, would the antipad size range really have any
effects or is it negligible?
Is an anti-pad just to keep solder off the pad if you flood the plane? Or is
there an actual SI reason for those things?
How sensitive is the SI to changes in antipad size?
Any concerns regarding manufacturing tolerances on antipads?
Thank you for any information and your patience explaining any of the above
questions to a mechanical guy.
Paul Clarke
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