ExpressPCB footprint mistake?

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I think there is a standard for the pin numbers of the SOT-89. Am I wrong?

Every datasheet I've looked at with SOT-89 packages number the pins in the same way.

The SOT-89 footprint that came with the ExpressPCB package seems to have them numbered the wrong way. Do you agree?

If that's the case, it makes me wonder what else is wrong with the ExpressPCB footprints. Now I wonder what the chances are of making a printed circuit board that works.

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With any package it's advisable to check all parts and footprints carefully before you use them; don't assume that they are correct!

Leon

Leon Heller G1HSM

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Yeah, I hear ya. I don't see how someone could lay out the pads for a chip and then number the pins ass backwards. I take that as a warning shot across the bow. I'd better check the pads too.

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Ass backwards??

I don't think it's as straightforward as that.

I've seen all sorts of numbering conventions from manufacturers for SMD parts on datasheets... unless you're showing the absolute official "SOT-89" specification from the actual standard document from whatever standards body drafted the SOT series, I'd say you can have no idea what the numbers are MEANT to be. I sure don't.

The bottom line is the first time you put a new component on schematic, then into a PCB (especially for small SMD packages) ALWAYS check that the datasheet for the part matches the nets on the pads for the footprint on the board.

I don't know what ExpressPCB is like, but I know in protel that another really important thing to work out is the pin numbers in the schematics - no point having the footprint with the "right" numbers on them, if the schematic component has the numbers in an order that doesn't match the layout!

I do know I'm not the only one here who's done a board where a sot-23 part had to be soldered on upside down and rotated..... though I can happily say I never repeated that mistake.