EEVblog Electronics Community Forum
EEVblog => EEVblog Specific => Topic started by: EEVblog on December 30, 2020, 10:17:14 pm
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By popular demand, Dave tears down the dodgy tactile switch from his aircon, and compared with a couple of others.
https://www.youtube.com/watch?v=sdLm08zfE4g (https://www.youtube.com/watch?v=sdLm08zfE4g)
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Some might describe me as a plating expert. Those dark patches on either side of the snap dome looked like they lined up with the two contacts on either side of the post in the center. I believe those contacts and their respective legs leading out of the body are a single piece and, speculating further, I believe those legs are tin-plated which would mean the two contacts on the inside are also. The black stuff is probably tin oxide as a result of fretting corrosion (its the result of repeated, low amplitude motion between the snap dome and the contacts). I don't think I would say it's bad plating, its just a very cheap way of doing it, both because tin is relatively cheap and because it enables the leg/contact piece to be stamped and plated as a single piece.
Of course I'd have to throw it under the XRF to make sure but the shipping costs....
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use more power microscope, looks like arcing spots
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Of course these pushbutton switches cannot take a pcb wash, you have to use no clean solder. But that mistake I have seen noobs make.
I'm suspicious the switch didn't get a drop of water inside, as the disc is oxidized black above the contacts only, so electrolysis occurring at those two gaps.
Omron (https://components.omron.com/product-category?nodeId=20&nodeParentId=20#Tactile-Switches) I find the best, I have zero hassles with them but they are expensive. Gold is optional.
E-switch (https://www.e-switch.com/product-catalog/tact) I did not like, just too cheap, they melt easy and plastic cover.