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I am having troubles with some push buttons, such that some of them work, some of them sometimes works, and some of them just do not work.

In an attempt to find the cause of the issue, I took one of the faulty buttons apart to see if anything had broken internally. I found nothing to be broken, but was surprised at the mechanism used to make the contact when pressed and it did not strike me as the best way to make to contact so wondered what other mechanisms were about. Alas, my searching on the interweb has not prevailed with an answer, probably because of my incorrect terminology.

The type I currently have, looks like this button and mechanism:

enter image description hereenter image description here

So, as the button is depressed, it bends the 'dome' of metal to make contact between the two pins. So, to me, this doesn't seem the most reliable method, what are the other options for the internal mechanism of a push to make button?

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  • \$\begingroup\$ What are your reasons for thinking this kind of mechanism is not the most reliable ? What is most reliable ? Maybe it is reliable enough ? Your bad experience with push buttons might have more to do with the quality of those particular push buttons or the environment you use them in. I expect that in a dusty environment, these buttons are not a good choice unless you protect them from the dust. The most reliable button is "no button". What is not there cannot break. \$\endgroup\$ – Bimpelrekkie Jun 13 '17 at 10:16
  • \$\begingroup\$ @Bimpelrekkie I suppose it just was not what I was expecting to find when I opened it up! I guess I was expecting to see a simple metal 'bar' bridging the gap. But I do not know what alternatives there are, hence the question. Alas, no button is not an option! \$\endgroup\$ – MrPhooky Jun 13 '17 at 10:28
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That's probably the only mechanism you'll find in small pushbuttons like that.

However, the mechanism is really not relevant. You shouldn't be looking at that level of detail, especially since you apparently know little about pushbutton design tradeoffs. What you should be looking at are specs like on-resistance, bounce time, maximum lifetime activations, etc. How the manufacturer achieves those doesn't matter.

This type of switch mechanism has been used in many places quite successfully. If a reputable manufacturer guarantees 100k operations, then I'd take that at face value. You are starting with incorrect assumptions, then over-thinking this. Stick to your requirements and how those are met as described in the datasheet.

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  • \$\begingroup\$ With that in mind then, what could be an explanation for their failure (i.e. not making contact when pressed) - upon opening there are not any obvious mechanical issues. I don't see any reason why they should be failing - is an assembly process likely to cause issue (shock, heat, etc.). If it makes any difference the part is DTSM62NV from APEM. Naturally, I am not expecting you, or anyone, to scour the information for a reason, just wondered if there were more common failure modes or processes which are more likely to cause damage. Thanks anyways. \$\endgroup\$ – MrPhooky Jun 13 '17 at 12:19
  • \$\begingroup\$ @MrP: I don't design switches, so I don't really know. I have seen these kind of dome switches where the metal of the dome eventually fatigued and cracked. It no longer sprung up after pressure was released. \$\endgroup\$ – Olin Lathrop Jun 13 '17 at 12:25

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