Review of DC Barrel Jack PCB footprint - Things don't add up!


#1

This is my second footprint and I am struggling to get it to match the datasheet perfectly.

The datasheet is here : https://www.mouser.co.uk/datasheet/2/445/6941xx301002-469315.pdf
The footprint is here : 3_Pin_DC_Jack.kicad_mod (924 Bytes)

Issue 1:
Pad 1, should be 13.6 to the very back of the jack.
On my footprint, it is 13.25
This doesn’t seem right.

Issue 2:
Pad 3 should be 10.6 to the very back of the jack.
On my footprint, it is 10.6
This is good.

Where is the missing 0.35!

Can any experts spot any other mistakes I may have made!?
36


#2

The sizes given in the datasheets are for the cutout not for the copper size.
You have two options. One is to use oval drills

  • diameter 0.8, length 3+0.8
  • copper size larger in both directions by at least your minimum annular ring requirements

Or you use a normal drill size of 3+0.8 (Again copper should be larger than that)


#3

Hi Rene,

I am not sure why your suggestion fixes my problem.

My pads are already 3 x 0.8 but are rectangular, because the datasheet shows rectangular pads?


#4

The yellow area on your footprint is the copper. Your jack has three lugs which need holes or slots to pass through the board. At present you have small holes in rectangular copper pads. Have a look at the 3d view (alt + 3) to see what this FP will look like.


#5

You can see the feet of the component in the datasheet. In this case, especially if you solder it manually, the footprint can be almost anything if three requirements are met:

  1. The feet go into the holes (i.e. the holes must be large enough).
  2. It must be easy to solder (i.e. the holes must be small enough).
  3. The manufacturer is happy with it.

Most probably normal circular pads would be OK, the hole diameter should be about 3mm and the copper ring width around it about something like between 0.2mm and 1mm. (EDIT: ring width must be much more than 0.2mm for solderability and durability.)


#6

Look at the foto or drawing of the part again. It does not have round pins. The cross section of the pins is what has the measurement 3x0.8mm.

This means you either need a slot for every pin that can fit 3x0.8mm or you need a round hole of size 3mm (plus a bit more)
Right now you have a round hole with diameter 0.762mm (Where does this drill size even come from?)


If you want to go with plated slots you might check with your manufacturer if they can produce them. (Or if it will cost extra to get plated slots)

If they can then there are a few options available how you can define them in kicad.
One option is to use the oval drill feature of kicad (set the drill shape to oval hole and set the two drill size parameters to the required size)
Another option is by using the edge cuts layer do define a slot. (For manufacturers whose software does not understand the oval hole definition made by kicad)


#7

Ok this is what I have updated it to – annular ring according to my manufacturer (https://docs.oshpark.com/submitting-orders/drill-specs/) isa 0.127mm – are we good here? I think we are?

3_Pin_DC_Jack.kicad_mod (939 Bytes)

I appreciate the explanation over the drill bit size being oval rather than circle, makes perfect sense. 0.762 seems to be the default for me.

I still don’t see why #issue1 is being caused?


#8

I suggest you ditch the suggested footprint and think about how you would create a footprint if you had only the physical component at hand.

This isn’t a general comment about creating footprints, just for this case. You could learn more by taking into consideration the actual physical characteristics of the component rather than trying to duplicate the existing footprint.


#9

I am not sure why I would do this?

I have created this footprint myself, from scratch…


#10

Hi @renegadeandy
supposing you are looking for this component
694108301002
https://www.google.com/search?q=694108301002
you can get the footprint for kicad directly a this site:
http://componentsearchengine.com/ placing the code 694108301002
in the searcher.
http://componentsearchengine.com/search.html?searchString=694108301002
You will get the ECAD model for many sw with kicad included.
And then you will have a fp to modify as you would decide.
Unfortunately you need to register to get it, but the license for the footprint is really kicad like.
The footprint will be in the old ‘.mod’ format, but it can be imported/loaded by KiCAD footprint editor.

PS: I’m NOT in any way affiliated to RS nor SamacSys companies, I simply found they are offering a nice service (for the moment free and with an usable license plan) :smiley:


#11

Because you seem to have a 2.8mm pin and a 0.762mm hole. It doesn’t fit. I meant you are trying to copy the footprint from the datasheet footprint specifications. I was suggesting you forget that example footprint and think only the physical characteristics of the component. That way you would have noticed what is actually wrong with your footprint.


#12

I am sorry that doesn’t help me. The datasheet has the dimensions of the physical component and that is exactly what I have done.


#13

the datasheet shows only the DRILLS for the pads… this is a bit unusual, but some manufacturer does it in this way…


#14

Then there must be something you didn’t understand in KiCad.

The pad shape and size is for the copper area. The hole is different. You have to have ~3mm hole or a slot or cutout where the foot fits.


#15

eelik, did you check my latest footprint - I am still confused by what you are saying :

As you can see - I actually have 3mm x 0.8mm – which will allow the slots of the jack to fit into the board…?

@maui I have got to the pick category part but don’t know what category to choose? The site doesn’t make it easy to download this model?

Which category should I choose?


#16

Drill bit size is always circle, there are no oval drill bits. Oval holes (slots) are usually made by moving a round bit, not just by drilling.

What do you mean by that? Do you mean that KiCad made it by default? Again, it’s the size of the actual physical hole in the board and the component foot doesn’t fit there.


#17

Ahh, okay, now it seems better, there are actual slots there. Sorry I didn’t load and view the footprint file.

It looks like you still don’t have enough “annular ring”, the copper area around the slot.


#18

@eelik you may be derailing this thread.

I have updated this - please understand that :slight_smile:

See my post above also.


#19

Yes, I apologise for looking only at the first version.


#20

if you register (as I mentioned), then the result will be different