PCB for membrane keypad

Layout
1

Dear all,
This is my first post here and my first pcb design, so please lots of mistakes from my side. :smiley:

I am doing a PCB to replace the acetate PCB like that comes with many low cost keypads. On my case that’s the printed circuit in my calculator.

The PCB design consists only of vertical and horizontal copper tracks. In the intersection of each row and column I have a hand made footprint where each key will touch when pressed.

Something similar to what I am doing.

Problems
1 - DRC Fails saying that the PAD is too close to a track. That is because they are connected. :smiley:
Is this happening because I don’t have a schematic, so the software could match pads to nets ?
2 - I am always changing grid size to perfectly connect tracks. I think this is not good, but will that have an impact on the final product?
3 - I am going to use these guys http://www.allpcb.com. How can I get their rules, so I could configure kiCad according to them ?

Thanks in advance.
Best regards,
Pedro

2

What version are you using?

  1. In version 5 you can make custom pads “DRC friendly” for your footprints. It is not the easier way to start with kicad, though.

If there isn’t a schematic you need to disable DRC in order to be able to make a pcb.

  1. The option magnetic pads allows to route with any grid and get the track connected to the pad.

  2. For the rules of any manufacturer you need to contact them.

3

Hi Pedro,
Thanks for your reply. I am using kiCad 5.

Can you please take a look at my PCB and let me know what you think, specially the footprints that I have made?

Best regards,
Pedro

4

A quick glance on their website leads to the page Standard PCB Manufacturing Capability.

1 Like
5

It seems alright. But it is difficult to evaluate a .png file. Especially without the schematic.
I suppose the footprints for the keys will work fine. It is not possible to make any measure. Look at the website pointed out by @ppelleti to check the design rules.

6

Why don’t you want to start with a schematic, in the end it will save you time and also gives a netlist for the maker to use for electrical test.

1 Like
7

hi,
To do a schematic I would only have pins, labels and not much more. Please remember this takes no component at all, just tracks drawn horizontally and vertically with the footprint for the keys cutting the connection between one side of the track and the other, which will be shorted whenever a key is pressed. So I guess that would be more difficult to do the schematic + layout, than the layout on it’s own.

Best regards,
Pedro

8

I disagree, even with 9 pads and tracks. If you don’t want to create nets you just have to do without DRC. But the time spent with schematic is saved in layout. After you have used the push and shove router you will know why.

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9
  1. You have documented your design. Never assume that someone else won’t want to use it or even you coming back to it a year later.
  2. You get DRC, the router completing connections automatically
  3. You get a netlist fo the PCB maker to use for testing
  4. It is much easier to check the schematic is electrically correct
1 Like
10

Not pins. Buttons :wink: and i would guess also at least one connector as i assume you will want to connect this pcb to something.

11

Hi,
What I mean is that, at this point, I already have the layout done, so what would be the benefit to go back and design the schematic and layout?
The layout I’ve done wasn’t time consuming at all, since I literally drew one line, one column, one via, one pad and one footprint. Then I created an array with the correct number of elements and spacing and with a click the layout was 70% done.
The only advantage I see in starting from scratch is to be able to use DRC.
Thanks,
Pedro

12

i would guess also at least one connector as i assume you will want to connect this pcb to something.

Yes I will connect it to an arduino. :smiley:
So, I will connect five rows and six columns (11 pins) to the arduino. After that will be software development.

13

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