On Tue, Feb 11, 2014 at 11:40:29PM +0100, Nick Østergaard wrote: > In addition, I think that the default shape of the pads should be > rectangular, that is "*oval": "False". I have never seen a datasheet > suggesting oval pads for a QFP. I did not add that to the patch since that > was not the problem I wanted to fix and it can be selected by the user > anyway.
There is a (somewhat involved) IPC rule defining if the pad should be rectangular or oval: in short if the pad have to be trimmed to keep side clearance or underfill it has to be rectangular, otherwise it should be oval (rationale: round corners have better mechanical properties, but if you trim you want to keep all the attachment surface available). So, more or less, if pitch is < 1 mm *or* standoff height (the A1 JEDEC dimension) is < 0,15 mm pads should be rectangular. In short every modern component has low standoff so it need to trim for underfill… However when/if IPC7351C become standard and widely applied there will be a resurgence of oval pads :D Even shorter explanation: if you don't do high reliability board, just use rectangular pads; otherwise that would be the SMALLER of your problems:D -- Lorenzo Marcantonio Logos Srl _______________________________________________ Mailing list: https://launchpad.net/~kicad-developers Post to : [email protected] Unsubscribe : https://launchpad.net/~kicad-developers More help : https://help.launchpad.net/ListHelp
