Re: Min Via Size
The size of a via is driven by several different engineering concerns. There is no such thing as "standard size vias".
For very high frequency circuits, you want to keep the inductance of your vias as small as possible. This translates into small diameter vias. On the other end of the spectrum is a via used for power - it may have to be large diameter to provide enough copper to carry high current without excessive heating.
How small the via can be is determined by how thick the circuit board will be when you are done. Board fabricators call this the "aspect ratio". How large a via can be is determined by the drill and route capabilities of your PCB fabricator.
The size of the annulus of copper you need to use is determined by your drill size. When a via is drilled by the fabricator, he has to use a bit that is 2-3mils larger than the final plated size of the hole - this is to make room for the copper plate inside the hole. He also needs a large enough annulus on both the top and bottom of the board to allow the plating process to proceed properly. Normally this is at least 4mils greater radius than the drill size. For example, you choose a finished hole size of 15mils. That will make the drill size about 18mils and the copper annulus will have to be at least 18mils+8mils=26mils.
One of the largest board manufacturers in the world is Merix. They have a manual available on their website that discusses the physical limitations for manufacturing a board. It is called their "Design for Manufacturabiltiy (DFM) Manual", and you can get it at: **broken link removed**