On Feb 2, 2008 11:23 AM, Jeffrey Baker <[EMAIL PROTECTED]> wrote: > Nearly every major part I need for my latest project is packaged in a QFN > (or LFCSP as they call it over at Analog Devices). I'm worried because the > parts have round leads and Sunstone, the PCB prototype shop, says they can't > make radiused SMD pads. Has anyone run into trouble with this, or are > square pads OK? > > Generally speaking the .5mm-pitch QFN seems to be on the edge of or beyond > the capabilities of a proto shop like Sunstone, but Sunstone has the best > tolerances I've been able to find. > > -jwb > > > > _______________________________________________ > geda-user mailing list > [email protected] > http://www.seul.org/cgi-bin/mailman/listinfo/geda-user >
I have had one of the Sunstone shops build boards with QFN32 and QFN48 as I recall. Results were pretty good. They had square-ended pads. -Be careful of solder resist "floaters" due to the little pieces between the leads. Best bet is to remove all resist between pads. -You may want to check your gerber files to see how much solder paste will be applied and check with Sunstone to see if it is sufficient (or too much). Does your pad have a large heat sink pad on the back? If so, you must carefully construct this pad in the footprint (possibly out of multiple squares). Again, check the paste layer. Joe T
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