Kicad edge finger footprints for 500/51X?

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Brian Roth

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Joined
Aug 20, 2005
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Location
Salina Kansas
I've just started down this Rabbit Hole and haven't come up with a solution.

The existing libraries I've found all seem to be oriented towards small-sized footprints as used for computer add-on cards and not the Olde School  0.156" center fingers.  I imagine that I could spend a week trying to doodle a footprint, but perhaps this has already been done.

Thanks!

Bri
 
john12ax7 said:
I don't use kicad,  but do have some drawings can provide if you decide to make your own footprint.

After trying a variety of Google search terms, I ran across this website:

http://kicad.rohrbacher.net/quickmod.php

I've doodled with it, and oddly enough, the SIL footprint seemed to yield better results for this application vs. the various edge connector choices.  Shrug.  At least the previews look valid, but I will need to try the actual footprint in Kicad.

Squarewave, how wide and long are the fingers in your drawings?  Perhaps I could find that same info from the Edac or Sullins websites, but maybe not.

Thanks!

Bri

 
This is my Kicad edac 15 pin module design.


https://drive.google.com/open?id=1rEoktfi90OD5llLIwRlNnDsoAGGVoJ5i

Paolo
 
You can get a lot of info from this thread,  just ignore the extra pins for 500 series instead of 51x.

https://groupdiy.com/index.php?topic=39897.60

What I've realized is there really is no standard, everyone does it slightly different.  .156" pitch is the only consistent part.  Finger widths can range from. 090-.114" and lengths .315-.400"
 
Here's what I ended up with (which included manually hacking the .MOD file with Wordpad).  I had to study the Kicad file format docs to comprehend what all of the various fields represented.

I added through holes to tie the "fingers" on both sides of the PCB together.  One thing I need to tweak...the hole diameters do NOT match any of the standard "number size" drill bits.

I've attached a screen shot from Kicad of the footprint.  After comments/further tweaking, I will post the .MOD file here at GDIY.

Thanks for everyone's help/comments!

Bri



 

Attachments

  • 500edge.pdf
    304.2 KB · Views: 66
Brian,
I know that many 500 series modules have fingers on top and bottom layer of the board BUT api's modules fingers are only on the bottom layer.

Paolo
 
pahstah said:
Brian,
I know that many 500 series modules have fingers on top and bottom layer of the board BUT api's modules fingers are only on the bottom layer.

Paolo

Thanks, Paolo.

Yes, I am guessing that the "classic" API modules had only bottom side fingers (and pads) since they were single-sided cards, which were less expensive to manufacture.

Since modern PC board manufacturers routinely offer two-sided boards as the "low end", I figured it was a good idea to duplicate the fingers on both sides and then tie each pair together to provide contact redundancy.

Bri
 
Usually for production the fingers get plated with hard gold for wear resistance. This adds significant cost to the pcb, so it can make some sense to do single sided only, but there is no firm rule for this.

Generally soldermask is not applied where the fingers are, so it's good to define a keepout area for this.
 
There was at least one cheap Rack with the card edge connectors only connected on the wrong side.
Modules with double sided gold fingers worked, single sided didn't ...
 
[silent:arts] said:
There was at least one cheap Rack with the card edge connectors only connected on the wrong side.
Modules with double sided gold fingers worked, single sided didn't ...

Egads!  <g>  The EDAC and Sullins female connectors I've seen have contacts on both sides.

Point also noted from John12ax7 about costs for plating hard gold on both sides of the connector fingers.

Bri
 
Brian Roth said:
Besides this useful discussion, does anyone have any comments on the footprint design I posted earlier in the thread?

Thanks!

bRI

The size is fine imo.  You want some clearance to the board edge, at least .010" (more if you bevel the edge), either something to remember,  or incorporate it into the footprint directly. And also the previously mentioned soldermask keepout.

Personally I wouldn't put vias on the pads, but I have seen some designs that do.  So will let others decide on that one.
 
Vias tend to be mechanical weak points.  So if used you need to make sure they are a sufficient distance from the point of stress.

Perhaps look at the Great River units and do it similar.
 

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