Good afternoon, everyone,
I'm working with a library part (a dual DB15 connector) and I'm trying
to understand how the DRC restring (isn't the English term for this
"annulus"?) parameters work.
but Eagle 6.6.0 doesn't appear to be using the parameters in the way
that that article suggests.
My DRC restring settings are as follows:
Pads (Diameter is checked):
Top: Min 0mil, 25%, Max 20mil
Inner: Min 0mil, 25%, Max 10mil
Bottom: Min 0mil, 25%, Max 20mil
The text in the DRC window box says "Restrings for pads and vias are
defined in percent of the drill diameter (limited by Min and Max). If
the diameter of an actual pad or via would result in a larger restring,
that value will be used in the outer layers. If the Diameter option is
checked the actual pad or via diameter will be taken into account in
the inner layers, too."
My library component has mounting pads that have both a defined drill
(118mil) and diameter (137mil). To re-iterate: my pad diameter is not
set to "auto".
According to the link at the start of my posting, I should take the
drill diameter (118mil), multiply by the %age (25%) to find out what
the "auto" diameter would be. 25% of 118 is 29.5mil. This is larger
than the maximum specifed for the top and bottom restring parameters.
If the diameter were set to "auto" then I expect that Eagle would
automatically reduce up the pad restring/annulus to be 20mil, but since
my pad diameter is explicitly set in the library footprint, Eagle
should be leaving it alone, shouldn't it?
What I am seeing is that Eagle is making the ring around the drill
bigger than the one specified in the library part. I have specified
137mil, for a ring width of (137 - 118)/2 or 9.5mil.
The only way I can get Eagle to stop making the diameter bigger is by
reducing the maximum, which seems odd because it's the minimum that
should be defining the smallest pad ring size, not the maximum. My
minimum is already 0, so why is Eagle messing with my rings?
Clearly I'm misunderstanding something. Any help in understanding this
would be greatly appreciated.