Why is it that the manufacturers' footprints for SM devices nearly always give the dimensions between the edges of the pads? I thought it was standard engineering practice to give the dimensions between centres, which is what is required by the PCB package I use, so I have to do a few calculations every time I create a new SM footprint.
Leon
Further to the above, I've just seen a footprint which has *one* dimension between the *centre* of a central pad and the edge of another with *all* the others between the edges!!!
Leon
they do that so you can learn how to use a calculator!
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One of my pet peeves as well. So far I haven't screwed up the offset calculations on a board, but it's only a matter of time...
Bob
I always try to print it out 1:1 and lay the part overtop with a new footprint. If there's no samples in hand, that's when problems (this and other kinds) tend to occur.
Best regards, Spehro Pefhany
Using my CAD software, when creating Patterns like this - I will usually also place the Package Outline information on an Assembly Layer - superimposing it onto the Pad Layout. I will also create little square pads on the Assembly Layer - that way... if something looks 'odd' it will usually jump out at me, and I can investigate further, correcting if necessary.
I had a Pattern recently - for a SIM Card - that dimensioned to the plastic edges... and the Pad edges. That was a challenge. I think mechanicers like to pose interesting challenges when it comes to dimensioning parts.
Regards,
James Jackson Oztronics
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Hello, everybody. In my opinion it is worth to visit
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