Stopping TO-220 isolation

Question

I have a problem which is keeping me working over the holiday -the only thing keeping my board from fab. I've "tried everything" and read every Googled forum, but can't find the problem addressed (everyone wants to insulate their TO-220, not the other way around).

I have a 7805 in a TO-220 and I want the bolt hole connected directly to the ground plane ("GND") on the bottom (and the top). Eagle insists on isolating it. It seems Eagle has lots of ways to keep traces apart, but no ways to insist "I WANT COPPER HERE NO MATTER WHAT". I've edited the part, but to no avail; packages only have holes, not vias. I've even tried illegal ways, such as putting a hole on a via (didn't work). I've messed with all the DRC's (usually with bad consequences), but even that didn't fix it. If I can't solve this, I can always edit the Gerbers... p.s. NEVER had this problem with Bishop Graphics and Datak...

autodeskguest · Accepted Answer

Steve Ins pisze:

I have a problem which is keeping me working over the holiday -the only
thing keeping my board from fab. I've "tried everything" and read
every Googled forum, but can't find the problem addressed (everyone
wants to insulate their TO-220, not the other way around).

I have a 7805 in a TO-220 and I want the bolt hole connected directly to
the ground plane ("GND") on the bottom (and the top). Eagle insists on
isolating it. It seems Eagle has lots of ways to keep traces apart, but
no ways to insist "I WANT COPPER HERE NO MATTER WHAT". I've edited the
part, but to no avail; packages only have holes, not vias. I've even
tried illegal ways, such as putting a hole on a via (didn't work). I've
messed with all the DRC's (usually with bad consequences), but even that
didn't fix it. If I can't solve this, I can always edit the Gerbers...
p.s. NEVER had this problem with Bishop Graphics and Datak...

The easiest way is to put manually few GND wires over the mounting hole.

And accept few DRC errors.

Eagle avoids any copper around holes and other elements with lines in

dimension layer - the program sets a "gap" with "clearance" width.

This is very known feature (IMHO a bug) Eagle uses dimension as a

conductive element until you set distance copper-dimension to zero. But

in this case you have to set proper isolate of the polygon.

HTH

--

Grzegorz Zalot

complex ltd.

office tel/fax : +48 32 2505840

mobil : +48 501 301515

Former Member · Answer

Grzegorz: It worked! When I tried this before, it didn't. Now I know why: The wire MUST start at or end at a GND via, not just cross over, not just connect to the GND plane, not go to a non-GND via. ALSO it must NOT start or end at the bolt center or you will get the dreaded "Can't backannotate this operation. Please do this in the schematic!" This doesn't require messing with design rules or packages. As far as a few DRC violations, Damn the torpedos!