Ok Scott,

This is what I would do.  Be aware that I am not a board supplier, but a designer and
purchaser of boards.

a) Determine the max hole size.  Lets assume these are .010 mil (max) vias.
b) Determine the annular ring requirement.   In this case, Zero.
c) Determine the fabrication allowance your company assumed when the job was bid.  Your
shop is a good shop, lets assume your minimum standard is 10 mil.

d) Calculate the diameter of the "keepout" area associated with the hole is.  This is :
a+2b+c.  (reference 9.1.1 of IPC-2221).  In this example, 10+2*0+10 = 20 mil.  This is
the area in which the actual hole might be drilled.

e) Determine the minimum spacing.  Lets go with 3.5 mil for lack of a better number.
(Table 6-1 of IPC-2222 states .05mm (2 mil))

f) Bring up the design on your DRC.  Change the diameter of all your 10 mil vias to 20
mil.  Set your hole-to-trace spacing to 3.5.  Look at all the DRC Errors.

g) Now that you have the problem documented.  Tell your boss that there is significant
yeild risk in building this board, and that you suggest a review of the cost and
delivery risks the design holds for both you and your customer.

f) If you are "the Boss", be prepared to a) spend a lot of time and yeild loss building
the boards, shipping late, pissing off the customer, and losing money, or b) spend a
lot of time educating your customer about design rules, drill tolerances,
non-functional pads, etc, likely pissing them off, or c) reject the design outright and
piss off the customer outright, and then maybe offer option b) if and when they are
ready to hear it.

George Franck

PS. If this was one of my board designs, I would apologize to you for wasting your
time, put the order on hold for redesign, and go educate (beat up on) my own designer /
DRC people.

"Scott A. Bowles" wrote:

> Phil,
> Thanks, but I have perused those specifications and did not come up with a
> concrete answer.  I was hoping some designers would know if there was a
> section that specifically covered my question and/or give me their personal
> design criteria.  I am surprised I did not receive more feedback from all the
> designers that usually comment on the TechNet.
> Scott
>
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