I am trying to make some rubber contact buttons. I am hacking a bit the kicad functionality, because graphic elements are not allowed in the copper plating layers; but I need to get these graphic elements on the layers to get the buttons working. My plan is to get them manufactured on seeed studio osh park, or other similar.
I managed to get these graphic elements by bringing a sparkfun library, intended for eagle, and then duplicating all the F.Mask lines by use of regexps.
It works all perfect until I plot: When seeing it on the http://mayhewlabs.com/webGerber/ viewer, the graphic elements look corrupted, this including the silk layers [this forum didn’t allow me to put a second image]. The curious thing is that some graphic lines of the copper layer will plot ok, like the polar lines in one of the quadrants. It is so frustrating to see the paths correctly rendered on the PCB layout but not getting through the plot; there are signs that it is possible, but some small reason doesn’t allow it.Im sure it is possible, either tweaking something on kikad, using third party software or modifying the copper layer files by text editor, but how?
Can you upload the footprint you used for those rubber contacts?
Does it contain the F.Mask layer modification or did you do that in the .kicad_pcb file later on?
Do you have a image/link to how you want it to look like? Some dimension drawing?
note: these files will be public for a couple of days, because this repository is a massive disorder. Later Will upload a more civilized, public repo.
Now I opened with Kicad’s Gerber viewer, and I can see the graphic elements on the layer. I was doing it wrong at first because I assumed that the copper layers were the first ones, but they were listed below. In this gerber viewer, the graphic tracks do work! Now I am wondering wether this is a bug in the mayhewlabs viewer. Do you think it will go though production if ok in GerbViewer? -just checking a more educated guess-
Hm, are you sure you want the soldermask to disappear just right over the copper tracks?
It’s thickness is not zero… considering the mask position tolerance and just the copper track width exposed I’d say your rubber will have a really difficult time to bridge those contacts.
Also, why does the footprint have 4 buttons defined?
Do they come like that?
And you got 2 times copper circles defined, were just 1 was needed:
hey! lots of thanks for the help. You are right; I thought of that problem, but then it sunk in between all the many other things. The sparkfun one defines a solder paste over it, I think. Do you think that seeedstudio would do solder pasting? or I should rather go by exposing big rings?
And yes, the footprint is a bit strange; but it makes sense from the perspective that they must fit perfect with some moulded rubber buttons.
Depends on the physical design of the molded rubber buttons.
Any manufacturer name + number for us, or a datasheet link?
[edit]
to answer myself: https://www.sparkfun.com/products/7836
The pcb fab houses (and thus the aggregators, like Seedstudio) usually do some tin coating or gold plating.
What does the rubber buton manufacturer specify for those contacts?
The paste definition will only help if you were reflowing it to put some paste there and get the height up above the soldermask thickness… but I wouldn’t want to reliably specify that. It’s probably easier to put solder there with an iron later on and tinker until it’s right. Still, the track-width is too small for that to work IMHO.
I’d even wager a bet that the tracks, fully exposed won’t be thick enough to allow you a reasonable buildup/thickness of tin there manually.
I did put some thick circles onto the F.Mask layer to keep the whole area free.
Didn’t delete the tiny cricles and lines that had been there… too lazy.
That’s how I would do it.
And gold plated, to avoid corrosion down the road and the trouble it brings…
PS: those button circles are not centered on the blue crosses (misaligned 0.25mm to the left)… same goes for the LED drawings (the LED PTH are centered though.
thanks! I was just doing the same thing at the same time. I removed all the duplicates and also removed the solder layer; and added these thick rings to the solder mask. About the type of contact plating required, I couldn’t find specification. But I will have to guess that in general the conductive silicones are suitable for tin plating/ no plating.
Well, if you can afford it and seedstudio offers it, go for gold plating. Should give you less hassle.
And avoid fingerprints before you mount it… clean the pcb with isopropyl alcohol.
