Designing an Edge Card PCB

Hi Troy,

It can be created the same way any component is created in EAGLE, by creating the package, symbol and combining it into a device.

rachaelp has a very useful series of blog posts which explains the procedure, see here: EAGLE Tutorial: Library Part Creation Part 1 - Creating Packages 

For your edge connector, I think I would ensure the origin is at the edge, not the centre, so that when it is placed on the board view, it is easy to align it with your board edge.

If you're looking for an example, see here, the files are downloadable: https://hackaday.io/project/7014-mini-pcie-pic18lf2550-devboard

Ordinarily there is a bevelled edge, and plating, on such edge connectors, you'd need to let the PCB manufacturer know (or sand-paper it manually if this is a prototype PCB).

Hello shabaz,

Thanks for the reply and including the links... I appreciate the help!

Regards,

Troy.

Hello shabaz,

I have gone through the steps necessary to create a package in Eagle for the edge card layout. However, as you say, then creating a symbol and combining it into a device is giving me problems. When you attempt to create a symbol / device, Eagle wants you to add what it calls 'pins' to connect to the pads which were created in the package. The design I am trying to build does not have any actual components. It just has contacts (pads) elsewhere on the board which will connect to each of the fingers on the edge of the board. Would you (or anyone) have any ideas on how to make such a design work so it can be rendered on the schematic and a board manufacturer will understand what to do?

Thanks much!

Hi Troy,

You should still create a component that corresponds to the card edge connector you are trying to fabricate. Ignore the fact that the symbol has "pins" think of them as just connection points for you to wire up the fingers of your edge connector. You can have a single symbol with all your connection point pins or you could have a single connector pin symbol which you replicate many time in the device (see my tutorials on how to create parts with multiple symbols) and then you place these wherever you need in the schematic and connect up to them. If you just want some connection points on the board connected to these, add some SMT pads or plated holes connected to these.

If I have misunderstood what you are trying to achieve or if there is anything that's not clear in what I have said above, let me know and I will try and give you some more pointers.

Best Regards,

Rachael

Hi Rachael,

Thank you very much for your reply! One thing that concerns me, and maybe it shouldn't, is that when creating the symbol there does not appear to be any way to represent connections which take place on a layer other that the top as can be done in the package design. This means that the physical 'footprint' for the symbol will go beyond the intended size of the board in the case of my 16-Finger (8 on Top layer and 8 on Bottom layer) connector. Can I assume that this won't matter since the symbol's purpose is just to define the connections?

Thanks again for your help in advance.

Troy.

Hi Troy,

The symbol itself doesn't care about layers, this is purely for the schematic where you define the connectivity. In the package you will define pads on the top and bottom side, and then when you create the device as a whole you'll map some of the symbol pins to the top side pads and the remainder of the symbol pins to the bottom side pads. Does this make sense?

Best Regards,

Rachael

Hi Rachael,

Yes, that makes complete sense. Thank you very much for your reply!

Troy.

Hello Rachael,

If I could trouble you to answer a couple more questions please...

First, I am wondering if the length and placement of the pins for the symbol will ultimately correspond to how the tracks run on the board. So, for example, if the length of the pin is .2 inches and is oriented to project to the right, is that how the board manufacturer will run the track?

Also, can you tell me how to define that pads should be (gold) plated within Eagle or is that an explicit instruction that the board manufacturer will have to get?

Thank you very much!

Troy.

Hi Troy,

The length and placement of the symbol pins is purely done to allow clear and accurate schematics to be drawn in order to correctly define the netlist for the design, I.e. what parts are in the design and what connects to what. The tracks on the board will follow whatever path you choose when you draw them, or if you use the auto router (I personally don’t use this as I can for it better myself) it will follow an algorithm in order to connect up according to the net list defined by the schematic.

For the card edge finger plating, you will need to specify this explicitly to your PCB manufacturer, let them know it’s for an edge connector and that the fingers need a “hard gold” plating. If you are unsure about the plating ask your manufacturer for advice. Eurocircuits also do a great YouTube video explaining the process.

Best Regards,

Rachael

Hi Troy,

Following on from my earlier post, here are a few links relating to the plating process for edge connector fingers and also a little more about what is meant by "hard gold".

https://www.eurocircuits.com/blog/gold-plating-for-edge-connectors/

https://www.youtube.com/watch?v=e6dH7TvqBVs

https://advancedplatingtech.com/hard-gold-plating-vs-soft-gold-plating/

Best Regards,

Rachael

Hi Troy,

Following on from my earlier post, here are a few links relating to the plating process for edge connector fingers and also a little more about what is meant by "hard gold".

https://www.eurocircuits.com/blog/gold-plating-for-edge-connectors/

https://www.youtube.com/watch?v=e6dH7TvqBVs

https://advancedplatingtech.com/hard-gold-plating-vs-soft-gold-plating/

Best Regards,

Rachael

Hi Rachael,

Thank you very much for staying with me on this! I appreciate the detailed reply and links you sent for reference.

Troy.

Hello Rachael,

I am attempting to work through the board layout after successfully completing the schematic and running the ERC with no errors. When running the DRC, however, it throws many Airwire errors and I am having trouble understanding why. The devices I am using are actually very simple... an array of (4) pads which are connected to each other and then (each) connected to one of the 'fingers' of the edge card connector. I guess my first question is why the schematic's ERC would show no problems but the board layout's DRC does when I have changed nothing regarding those connections. Is there anything you can offer to help me troubleshoot this?

Thank you very much in advance!

Troy.