What is the current smallest via on PCBs ?

Maybe you haven't looked very far -- Advanced PCBs is touting their

3mil (finished) hole size. I'm sure there are many others. Of course, it will cost you more than a 15mil process. You'll have to look at each fabricator to see what kind of annular ring they require.

I got an email from advanced circuits in Colorado:

Advanced Circuits requires that vias with connecting traces have a pad that is 10 mils larger than their drill, and component through holes with electrical connections have a pad that is 14 mils larger than their drill. Tooling holes with no electrical connections may have 0 mil annular ring.

I.e a 0.015 via drill must have at least a 0.025" pad over it

I.e a 0.070 component drill must have at least a 0.084 pad over it if there is a trace attached.

Do other PCB houses have the same requirements ??

They also suggest this web resource:

don

Here's Sunstone's manufacturing requirements:

There's a good non-manufacturer-specific discussion of PCB guidelines at by the same gent who does the

Both are much worth checking out.

--
Rich Webb     Norfolk, VA

I looked at the tutorial and very early in I realized that it is a bit out of date...

"The majority of electronic components were (and still are) manufactured with imperial pin spacing".

Uh, since when? Not only do most of the parts I work with have metric dimensions, some don't even bother to include imperial dimensions on the mechanical drawing in the data sheet.

Otherwise I think this tutorial is a fairly good starting point. I do recommend that no single reference on PCB design and construction be taken as gospel. I see too many differences of opinion and they all can't be right.

Rick