> -----Original Message----- > From: Dom Bragge [mailto:[EMAIL PROTECTED] > Sent: Thursday, January 29, 2004 5:23 AM > To: protel > Subject: [PEDA] TO-220 4th pin? > > I just would like to ask a question about how you handle > TO-220 footprints (& the like)... > > I have the three (electrical) pin device, that's fine. > I'm placing the T)-220's flat on the board. > > What if I want to (selectively) put copper on the top layer > under the TO-220 & have a suitable soldermask antipad? This > could aid in cooling without resorting to an actual heatsink. > How should I best do that? > > Do I place on the board a free pad, rectangle, with a hole > the same size as the hole for the TO-220 tab? Seems a bit > ugly, two holes etc etc but it should probably give me the > SMask opening. > > Do I make a 4pin lib part, have a 4th pin on the footprint > being the large hole & add a polygon connected to that net? I > suppose I'll have to add an opening for the SMask on the > TO-220 footprint as well.
Dom I usually keep 2 footprints available and one SCH symbol. The SCH symbol is always the same, 3 pins plus Tab (pin4), the footprint can then have several choices, normally I have a manufacturer prefix, and then TO220H or TO220V. If I intend to use this symbol with a vertical TO220 footprint I just add the No ERC marker to the 4th pin. PCB update just ignores pin 4 then, as does the DRC. I never add the fill or copper to the horiz version in the library, I do it manually afterwards as it is too much hassle when doing updates to have to update free primitives from... All the time. Easiest thing is to see it, so I uploaded a TO220 example from my user library to http://www.proteluser.com/download/to220/Export.zip Ignore the paste definitions layer, that is for something else ;) Best Regards John A. Ross RSD Communications ltd Email [EMAIL PROTECTED] WWW http://www.rsd.tv ========================= * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * To post a message: mailto:[EMAIL PROTECTED] * * To leave this list visit: * http://www.techservinc.com/protelusers/leave.html * * Contact the list manager: * mailto:[EMAIL PROTECTED] * * Forum Guidelines Rules: * http://www.techservinc.com/protelusers/forumrules.html * * Browse or Search previous postings: * http://www.mail-archive.com/[EMAIL PROTECTED] * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
