Almost square hole in footprint


#1

how is this supposed to be done ?

http://www.switchcraft.com/Drawings/pjras4x2u__x_series_cd.pdf


#2

its not 100 square it has a radius so all answers that it cannot be done can be avoided

goes perfectly well to do in cadence and mentor.


#3

It is probably an error in the cad drawing. For the more rectangular holes on either side there is a callout for an 8mil radius with “TYP (8)”. It should probably be “TYP (12)”, or another radius call out on the 3mmx3.5mm hole you are interested in also for 8mils. I think I know why they forgot to call out those radiuses… I zoomed in closely on the PDF and the radiuses aren’t drawn.

Remember, datasheets are written by humans who are not infallible.

Now, It would probably be wise to check the minimum milling radius of your fab house. 8mil radius (16mil routing width) seems awfully small. For example, OSHPark says “Typically, cutouts are cut with a 0.068” milling bit, for a 0.034” corner radius.” (The quote is a link to the page.)


#4

You could probably replace those rectangular hole with circular and still get those snap locks to grip.
There is no need for sharply radiused cut outs here.


#5

If we try to stay on topic.

No way other than a bunch of smaller holes?

Other workarounds?

Put an edge cut into the pcb afterwards once footprint is in place?
Awkward, but…


#6

My two cents:

  • The largest side of the cutout is smaller than the minimum milling size of the fab -> use a round hole (drills could be smaller than the minimum milling size as they do not encounter that much side forces.)
  • The smallest side of the cutout is much larger than the minimum milling size -> choose a milling size and draw a rectangle on edge cuts increased by milling drill radius (on both sides in one direction). Note the desired mill size somewhere and communicate that with your fab.
  • oval slots (or drills) are best used if the slot width is near one of the standard milling drill sizes.

Everything between the cases above is either an oval slot, round drill or a rectangle on the edge cuts layer depending on your personal preference and the exact needs for the project.

If your cutout is some polygon different to a rectangle you will need to go down the route of drawing it (probably size increased) on the edge cuts layer.

You can include edge cut drawings in the footprint (you just need to use a text editor to do it.)


#7

ok

thanks, i will hand-edit a edge-cut then.

kicad needs to fix this, be able to include edge-cuts in footprints, via regular editor.

all discussions of limitations are irrelevant as they equally apply to your outer edge and nothing keeps you from making a square indent into you pcb edge.


#8

Will be added early in the v6 development cycle: https://bugs.launchpad.net/kicad/+bug/1251393

Related: https://bugs.launchpad.net/kicad/+bug/1746279


#9

voted for the one i had missed, the other one I already had a comment on

thanks


#10

worked like a charm

footprint attached.

PJRAS4X2U.kicad_mod (5.0 KB)


#11

Not a workaround, a better solution :slight_smile:

Kicad supports slots, which will have flat sides and radius ends.
So in this case, you look carefully at the footprint, and decide where the flat is actually needed.

To me, the end supports have long-edge grips, but the centre one does not.
Just make all 3 slots. Done.
( Looks like the terminal also have friction grips too)

You do need to pause to think how the PCB fab will actually make a small 1.7x3.0mm square hole.
They will call you, and ask what radius you actually need, and they will charge more for the fiddly stuff.

Much easier to drop in a 1.7x3.0mm oval slot, which they do all the time.


#12

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