Starting out Creating simple FPC from existing cable

[radiokid]

Hi. Just after a bit of help. I am trying to recreate a small and simple FPC cable. It’s just a simple cable but a specific shape. It has 18 contacts at each end, one end if 0.5mm pitch and the other is 1mm. I have recreated the cable shape exactly in Photoshop and imported it into KiCad using the Import Bitmap tool. But now I am struggling with the following.

• Imported it into KiCad as a footprint, however in KiCad I’m not sure it is showing correctly (see attached pic)

• I have tried to add the ends of the cable, but the only elements I can find are the correct pitched connectors, these are the sockets not the cable ends I think.

• I’m not clear on how to connect the tracks of the cable up.

Essentially this is all new to me, but I am wanting to have a set of files that I can send off for manufacture. Any help would be really appreciated.

[Joan_Sparky]

You will need to create the footprints for the ‘edge connectors’…
Then you will need to create symbols that match those footprints pin count wise and draw up a schematic that copies the tracks from pin_x on con_a to pin_y on con_b.
Then you need to recreate the outline of the connector in PCBnew and create a layout that resembles the cable.
I have no idea on which layer the pcb company will want the info about thickening the cables with thin PCB material for the connectors, but you will have to draw that too.

Have you tried a search for FPC on the forums yet?
I remember a 1.5 years ago someone did make a mutli layer fpc cable with KiCAD… but it’s been a while.

Ah, here you go (6 topics actually, so quite a lot to go through).

https://forum.kicad.info/search?q=flex

So again, process:

1. you need to create symbols (symbol editor)
2. you need to create a schematic (eeschema)
3. you need to create footprints (footprint editor)
4. you need to create a layout (pcbnew) with the outline of the cable you got on edge.cuts layer (best drawn in a CAD tool and imported as a DXF file)
5. plot the gerbers and talk with your board/fpc manaufacturer of choice what else they need as info for making this

[radiokid]

That’s great, thanks for the help.

The cable is only single layer, as far as I can tell. It’s just a connection cable with no components on it. Pin 1 goes to Pin 1 etc etc.

With regard to the symbols, I assume this is simply creating the pins? I have found Conn_01x18_Male in the library, it looks correct to me. Creating footprints for the edge connectors should be simple I hope, they are really small pitch at one end 0.5mm. I already created the exact physical version of the cable outline and imported this using the bitmap conversion tool. The second picture in my post was that imported as an Eco2.user layer, is this not correct?

[SembazuruCDE]

@radiokid

I have found Conn_01x18_Male in the library, it looks correct to me.

Unless you really need a special symbol for the edge connect fingers (I suspect you don’t), the generic connector symbol should be fine.

[SembazuruCDE]

@radiokid

I already created the exact physical version of the cable outline and imported this using the bitmap conversion tool. The second picture in my post was that imported as an Eco2.user layer, is this not correct?

You will eventually want the outline of the board as connected lines in the Edge.Cuts layer. You can use what you have in the ECO layer as a guide for drawing your lines in Edge.Cuts. FWIW, the ECO layers are intended as documentation only. See this FAQ for a primer on what the different layers are intended for:

What is the meaning of the layers in pcb_new and in the footprint editor?

A pcb is a 3-dimensional object with different materials stacked on top of each other. If a designer talks about designing a 2 layer board then they typically mean that this board has two copper layers. A 4 layer board has 4 copper layers and so on. In addition to these copper layers there are other technical and documentation layers available. A good introductory read is this post by @dchisholm : https://forum.kicad.info/t/any-way-to-make-the-screen-more-understandable/13295/6 In KiCad the f…

[radiokid]

Just created the first edge connector in Footprint editor. Essentially its just 18 pads at 0.5mm pitch and 4mm long. That is all they are, the rest of the cable is just the copper traces that connect this edge connector to the other one. Is there anything else I should be adding to this edge connector footprint?

[Joan_Sparky]

@radiokid

Is there anything else I should be adding to this edge connector footprint?

You can add a F.CrtYd rectangle around it to make it complete.
Maybe a pin 1 marker on F.Silk and F.Fab.
Might also help to add the position of the edge to Cmts.User or Dwgs.User so that it matches what the connector needs and is easier to place and check in the layout later on (as this reference line then can’t be lost).
Depends on you entirely.

Example (for castellated pins on the edge of a board):

Also make sure where the origin of the footprint is relative to the pads.
It depends on your liking, but there are certain standards for it (pin headers for example have it in the center of pin #1 and pretty much all SMD devices have it in their ‘center’).
That’s where it rotates around in pcbnew when you hit [R].
For this use case I would put it between pin #9 and #10 vertically and either horizontally in the middle or where the edge is supposed to be.