Track near pad issue


#1

Hi,

I’m having an issue when I use the DFN-14-1EP_3x3mm_P0.4mm_EP1.78x2.35mm footprint in my design. I have my minimum track spacing set to 0.2mm which is fine for assigning tracks to the pads on this device, but I get DRC rules about track near pad. The default is to just inherit the design rules. I set it to 0.15mm (which is the distance I measured between the pads) but I still get this error. I don’t want my traces closer than 0.2mm, but I can’t figure out how to get rid of all of these DRC errors other than creating a custom footprint with the pad width set to 0.2mm instead of the default of 0.25mm.


#2

Ideally, the pad clearance and spacing should override the track clearance within the pad region. I ran into an issue with another footprint for a QFN where I had to change the corner pads to rounded to prevent DRC issues.


#3

This value needs to be less than the distance between the pads for DRC to pass in KiCad.

However, this value should also be such that the board fab house, that one plans to use, can meet that specification.


#4

I may have to set it a bit smaller then. I set it to 0.15mm, which is what I calculated the distance to be. Oshpark’s spec says 6 mil (0.1524mm) but I imagine that 0.15mm works fine). I use 0.2mm for my minimum track width and spacing to be on the safe side. The TSSOP-14_4x5mm_P0.65mm footprint is tighter than this. In the interim, I created a custom footprint with narrower pads in the hope that that will work. Another footprint that gave me grief was the QFN-24-1EP_4x4MM_Pitch0.5mm footprint. I created a variant where the pads on the corners are rounded, i.e. pads 1, 6, 7, 12, 13, 18, 19 and 24.