Designing an Edge Card PCB

Question

Hello, I am very new to Eagle. Can someone tell me if there is a step-by-step guide on creating a schematic / design for an edge card (w/ gold fingers) to be used with an IDC connector? Thanks very much in advance!

shabaz · Answer

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).

rachaelp · Answer

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

rachaelp · Answer

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

phased · Answer

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.

rachaelp · Answer

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

rachaelp · Answer

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