Question Help with DS lite rubber conductive pads and continuity

[kingderp2]

Hello, so I'm working on my Wii portable which I made a custom PCB for. I was testing everything to see if it worked when I noticed that the rubber conductive pads I have for DS lite face/dpad buttons aren't closing the circuit and triggering a button press. I used my multimeter to check the conductive parts of the rubber pads themselves but didn't get the continuity 'beep' to go off. I did get around a 200 reading though, which I'm guessing is in ohms.

So based on that and a little searching it seems like the pads are too resistive to actually trigger the button press on the GC+.

Has this happened to anyone else? How could I go about solving this issue if this is indeed the issue? Any help is appreciated. Thanks!

 

[Y2K]

Did you order your PCBs in ENIG plating? HASL isn't reliable for button contacts and can have issues.

 

[kingderp2]

Did you order your PCBs in ENIG plating? HASL isn't reliable for button contacts and can have issues.

I had them done in HASL (with lead). If that is the issue is there anything I can do to help it other than re-ordering with ENIG?

 

[Y2K]

I had them done in HASL (with lead). If that is the issue is there anything I can do to help it other than re-ordering with ENIG?

Yeaaah that could be your issue, not much to do other than reorder from my understanding, unless you got a way to gold plate PCBs at home?

 

[kingderp2]

Yeaaah that could be your issue, not much to do other than reorder from my understanding, unless you got a way to gold plate PCBs at home?

Oof haha. So do you think the issue is with the plating on the PCB if the rubber pads themselves already have a high resistance and can't trigger the continuity beep on my multimeter regardless?

 

[Stitches]

Did you order your PCBs in ENIG plating? HASL isn't reliable for button contacts and can have issues.

This is good to know, I had no idea it made a tangible difference. You've saved me one mistake

 

[Y2K]

This is good to know, I had no idea it made a tangible difference. You've saved me one mistake

I think its very much a case-by-case type of deal - plus HASL contacts will probably wear down quicker over time, so its probably not a bad idea to get them done in ENIG regardless. Thankfully OSHPark & DKRed offer free ENIG on 2 layer boards, so that could be an option.

Oof haha. So do you think the issue is with the plating on the PCB if the rubber pads themselves already have a high resistance and can't trigger the continuity beep on my multimeter regardless?

Carbon button contacts are fairly high resistance, however they work because you're sensing the difference between an extremely high resistance (an open circuit) and a comparatively very low resistance (100-200ohm) - theres 2 theories involved with HASL vs ENIG in terms of button contacts, and thats the electrical conductivity of HASL vs ENIG, and the fact that HASL doesn't end up being nearly as flat as ENIG. I think the latter is more relevant, since the gold layer on ENIG is so thin that it probably doesn't make all that much of a difference in conductivity. Just a guess tho largely, i'm not a professional by any means!

 

[kingderp2]

Carbon button contacts are fairly high resistance, however they work because you're sensing the difference between an extremely high resistance (an open circuit) and a comparatively very low resistance (100-200ohm) - theres 2 theories involved with HASL vs ENIG in terms of button contacts, and thats the electrical conductivity of HASL vs ENIG, and the fact that HASL doesn't end up being nearly as flat as ENIG. I think the latter is more relevant, since the gold layer on ENIG is so thin that it probably doesn't make all that much of a difference in conductivity. Just a guess tho largely, i'm not a professional by any means!

Thanks so much for the info! I'm thinking of trying something like this on the rubber pads before ordering new PCB's. Don't suppose anyone has any experience with something like this/recommendations?