[SOLVED] SMT-switch, what's it called? (it's like a bubble)

[TriggerHappy]

SMT switch, what's it called? (it's like a bubble)

I'd like to know what a certain type of switch is called. I don't need specific model id.
Here's a close up photo of it:
https://imageshack.us/photo/my-images/213/switchhv.jpg/

It's only about 4 mm (about 0.16 inches) wide.
It's like a bubble. It switches distinctly between being convex and concave when the key which normally sits on top of it, is depressed and released.


Also, I wonder what it looks like inside. I would like to switch this switch electronically instead of with my finger. But the details of the surface mounted board are too small for me to solder on. Could I cut open this "bubble" and find something which is more easy for me to work with in this respect?

I've googled all I can without finding anything like it, although I know it is a cheap common type of switch. Google doesn't help when words are missing... And image search mostly turns up fried eggs! :lol:

 

[sky_123]

Re: SMT switch, what's it called? (it's like a bubble)

It is called a 'tact switch', see the bottom of this page for some examples:
**broken link removed**

No need to open up the switch, you could just solder to the edges (there is no electrical contact in the center of the
entire switch.
You can see where you need to solder in your photo, to the bottom left solder point, and the bottom right point.
The contacts at the top are alternatives you could use (and you could check with an ohmmeter with the power switched off to
confirm).

Agreed it is quite small, but it is possible to solder. Use fine solder, fine soldering iron, and fine wire (e.g. something like 30awg
kynar or tefzel which you can google for; the wire is single-core, after you've soldered it to the point, use some epoxy to secure it
and provide a bit of mechanical strength to the insulation, not just the stripped wire portion.


To electronically activate it, you could either use a relay, or you need a voltmeter (or scope) to see if it is switching a contact to
ground, or some other voltage. Then you could use a BJT or FET.

 

[demetal]

Hi,
Its generally used in mobile keypads.... Its just like membrane keypad switches and work by the same principle of membrane switches... Use fine end soldering iron to get soldered... And if you open it you will find the nodes more closer than its terminals.. Which will make you more difficult to solder...

Good luck.

 

[tpetar]

Clasic SMD Tact switch

 

[TriggerHappy]

What a great answer, sky_123! I'm happy that people are so kind and helpful to an anonymous stranger.
I really hate working with tiny stuff. I have no talent for it. But looking at it, there's quite a distance between the soldering points I need. And in a magnifying glass things look even better :-D So I bought a "helping hand" on a tripod to hold stuff in the right place. Tinned the tip of the wire, applied it on the soldering point and slided the hot iron along the wire to get close. Found no fine wire, only had a chunky single conductor (which helped me keep stuff stable), but it worked great anyway. I was so happy when the first one stuck immediately. Only to fall off a few seconds later when I touched it slightly... The glue was a very good idea.

I can tell you how clumsy I am. When i soldered the second wire, the first one popped off (again) because I happened to hold the iron against it and melted its tin. And somehow I managed to put a black spot on a finger nail. And afterwards, I came to think that it'd be a good idea to test it before gluing, because I imagine that it's difficult to solder anything by then. But I was lucky.

About the switch. Tact switch is a very general term for many different types. It stands for any tactile switch, it seems. Is there no more specific word for that bubble membrane type? I don't like them, because once a key on my mobile phone stopped working, and when I opened it I found one of those things, but cracked and flattened. Could only call people who didn't have a 9 in their number.