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Footprint with shorted pins

Question asked by dmeeks on May 23, 2015
Latest reply on May 24, 2015 by sravankumar.padarthy

A lot of modern packages use large exposed pads which short multiple pins together. For example, package X2-DFN2020-6 from Diodes, Inc (see part DMP2039UFDE4). This part has pins 1, 2, 5, and 6 shorted together to make a single larger pad area.

In Pads, I don't see a way to create these four particular pins, and have them associated with a large copper pad area. The footprint editor lets me associate the copper to one pad, but not the other three.

And if I place an overlapping copper area shorting those pins in the footprint editor, it generates spacing errors and won't even let me route to a pin (because of the spacing errors).

One way to get around this is to define the large copper area as a single pin (use a polygon shape to create the pad and associate with one pin instead of four).

But then this is not in keeping with the package pin numbering conventions or with the manufacturer's specific pin numbering. In the case of this particular part, pins 1,2,5,6 would be pin 1. Looking at the part on a board, pin 1 would occupy the entire top of the part, not the top left corner, as is the convention.

 

Another option is to keep the four pins (1,2,5,6), and add an extra pin for a new pin (call it pin 7), which is a large power pad. That's probably the best option because it preserves the pin numbering of the package, it just adds one more pin. But thermally it is not as good because there are "voids" between the new power pad and the four pins. I admit that will make very little difference, probably not even measurable, but still it's a compromise that I would like to avoid. The best footprint would keep the pad as a continuous copper area connecting all of those four pins (in this case).

 

Is there a way to create this type of footprint, connecting multiple pins to the same large copper pad?

 

Thanks

dan

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