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I am creating a PCB in KiCad and I am trying to create a footprint for my mic, the ADMP401. When creating the footprint and running the design rules checker, it says I have a clearance issue with the pads on the footprint I created for the ADMP401 and it needs to be at least .2 mm. Im, not sure how to fix this. I have attached the datasheet. https://www.sparkfun.com/datasheets/Components/General/ADMP401.pdf

ADMP401

Footprint

Sparkfun module

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  • \$\begingroup\$ I inserted a picture of the ADMP401 I am using. As you can see, this ADMP401 does not have the middle or two corner pins, only the 3 on the end. I am unsure how to figure out what size I need to make the holes and the pads on the footprint to not violate these rules. \$\endgroup\$ Feb 19 at 20:23
  • \$\begingroup\$ Can you also post a picture of the footprint as displayed in the footprint editor? IIRC there are also clearance settings in the pad menu (select pad, press E, one or two tabs to the right) \$\endgroup\$
    – Sim Son
    Feb 19 at 20:41
  • \$\begingroup\$ yep, just checked. there are clearance settings for pad-to-pad clearance, solder mask clearance and paste mask clearance. Your problem is likely the pad-to-pad clearance. The DRC error should mention the layer where the problem is... \$\endgroup\$
    – Sim Son
    Feb 19 at 20:48
  • \$\begingroup\$ Be careful you are not mixing measurements in inches (in) and millimeters (mm). Also, are you actually using the 0.5500 in x 0.400 in module (PCB) as you show, or do you want to use the much smaller component as described in the datasheet you have linked to? \$\endgroup\$
    – Nedd
    Feb 19 at 22:11
  • \$\begingroup\$ Im not sure at this point, what I am using is pictured above, the ADMP401. \$\endgroup\$ Feb 19 at 22:47

2 Answers 2

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It appears that you are using a module using the ADMP401 and some supporting circuitry, not a bare ADMP401. That module just needs a 3 pin 0.1 inch header, not the fancy footprint shown on the ADMP401 datasheet.

You should be able to find a suitable footprint in KiCad's connector library.

If I had to make the footprint, I would use three .060 pads with .040 hole, spaced 0.1 inch apart.

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  • \$\begingroup\$ How can I make them 1 inch apart if the entire board is 4.72mm long and 3.76mm wide? \$\endgroup\$ Feb 19 at 20:58
  • \$\begingroup\$ The pin spacing is 0.1” (2.54 mm). \$\endgroup\$
    – Kartman
    Feb 19 at 21:02
  • \$\begingroup\$ The pin spacing is the same as for GPIO headers on an Arduino, Raspberry Pi, or similar boards \$\endgroup\$ Feb 19 at 21:12
  • \$\begingroup\$ So the first and third pin should be .1 in apart? \$\endgroup\$ Feb 19 at 21:23
  • \$\begingroup\$ No - there is 0.1 inch between first and second pin, and 0.1 inch between the second and third pin. When you get the actual module, the pin spacing should be obvious. \$\endgroup\$ Feb 19 at 21:32
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The footprint as shown in the datasheet does not require clearances closer than 0.3mm (0.306 and 0.300 are the tightest) so I think you've got something wrong elsewhere. Maybe try recreating it from scratch.


Your updated post shows a module, not the chip in the datasheet. You only have to make pads for a 2.5mm pitch 3-pin connector and leave room for the PCB clearances your fab wants to see.

Use 0.9mm holes (1.0mm is a bit loose I think) and make the pads big enough to get enough spacing. Since it has some mechanical purpose you can go with something like 2.0mm or even 2.2mm for the pads. You can even make them non-round to get more copper, but that's more important when you have a board without plated-through holes.

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  • \$\begingroup\$ Please see updated post. \$\endgroup\$ Feb 19 at 20:24
  • \$\begingroup\$ @user23342283 Show the footprint you created with critical dimensions. Figure 4 in the data sheet shows the recommended footprint. \$\endgroup\$
    – qrk
    Feb 19 at 20:40
  • \$\begingroup\$ The body of the chip is 4.72mmx3.76mm so the holes would be too big wouldn't they? \$\endgroup\$ Feb 19 at 21:46
  • \$\begingroup\$ @user23342283: The 4.72 x 3.76 mm is the size of the microphone device itself. The SparkFun module is 0.4. x 0.55 inch (10.16 x 13.97 mm). From the SparkFun picture, it appears the holes are 0.05 inch from the edge of the board - you seem to have them 0.1 inch from the edge. Your pads look very small to me. Please verify if you are working with the bare microphone IC or with the SparkFun module. That makes a BIG difference when discussing the required footprint. \$\endgroup\$ Feb 19 at 22:47
  • \$\begingroup\$ The sparkfun module. \$\endgroup\$ Feb 19 at 22:48

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