library help

Leroi,

I found this picture of a PCB footprint for a similar switch:

Unfortunately, a lot of the detail is obscured by the switch.  The concept seems somewhat simple.  One leg has a plated through hole to make contact with the switch (the site says not to solder the leg in the hole, just bend it over loosely to hold it in place - apparently soldering will change the click and possibly cause earlier failure).  The center metal pad is the other contact.  When the switch is pressed, the through hole and the center pad are connected.

The print quality of your attached diagram is difficult to read, but with parts in hand, you might be able to figure out the location to the two holes and the center pad location.  As far as I can tell, you could do a plated through hole on both legs (I would make these a little tight, i.e. not too large, to keep things in place.

Hopefully this helps.

Gene

hi thanks for the reply.

This will be of course helpful. So basically the second leg is just for stability and plays no role.

I also found this library(dome-key.lib)  but am not sure if this would be help.   I though of using the inner circle as one contact the outer as the second.so the legs will just be there for mechanical stability on the pcb. I am not sure if this can as well work.

Leroi,

The library component that you are showing is very close.  The outer ring (with what look like unplated holes) has contact points (non-masked pads, near the holes) that the smaller domes will make contact to.  So in this model, the electrical contacts are all on the surface of the dome (outside and inside) and the legs are only for stability.  The leg positions and the pads will have to be adjusted (holes are not on center-line) and there are three non-masked areas to make contact to the outer edge of the disk.

Gene

Gene,

thanks for the help and i appreciate. I came up with something and i hope it works. Even though from the datasheet, the inner diameter of the ring is not given. I am still an amateur though in creating a library and is actually my first time doing it. I simply inserted smd pads around and in the middle.

I am actually not yet done and just wanted to know if i am on the right track.

Thanks

Leroi,

I am not sure if multiple pads will work.  Later on, during the Design Rules Check (DRC) there may be some complaints.  Each of the overlapping pads will violate the distance rules.

Let me look at a couple of options to see if I can find a better approach.

Gene

Hi,

is also possible to use just the inner and the outer rings as contacts?then using the two legs just for stability on the pcb?

Leroi,

I tried something like that last night and I could not get it to work.  The problem lies with not being able to 'name' anything other than a pad.  The one thought that I had was to place 3 plated-through holes (pads). Two of them would be used for the legs and the third would be the center contact. Something like this:

During the layout phase, you could create polygons (on the proper surface, without the mask applied to provide more contact area.

There may be ways to do the 'named' polygons in the library creation process, but I still have not had this work for me.

Good luck,

Gene

Hi Gene,

thanks for getting back. could you please send me the library you made?thanks

Leroi,

I did this example without knowing any of the dimensions of the switch, so it is only an example.  I am not sure how to attach the file.  Please send me an email with your email address and I will send the library to you.

Gene