The Good Bad and the Ugly of the Membrane Switch - Page 1
Forum section: electronics / general

author: jonovid
author_rank: Super Contributor
timestamp: November 18, 2019, 01:29:14 pm
content: curious to know! whats the story with membrane switches.seen a lot of them used in microwave ovens & garden timershow do you tell a good one? from a poor one?I prefer a good click or tactile.after seeing the EEVblog video about designing a flexible PCBare not membrane switches just flexible PCB samwidges with tactile caps set on them?

author: Berni
author_rank: Super Contributor
timestamp: November 18, 2019, 02:04:55 pm
content: Id say its easy to tell them apart. If its a membrane keypad then its a bad one.Im not really a fan of these things, i think membrane keys feel like crap to use. But they are a very good way of having buttons on a product that must survive being exposed to water or dirt.In general these things are metal domes placed on a PCB and then covered with a film that has the printed graphics on it. There are a lot of companies that manufacture these things in reasonably small volumes. You just give them the graphical design and spec and you get the finished membrane that you stick onto your PCB. Or you can also have them also produce a foil circuit behind it that you just plug into a FPC connector.

author: Ian.M
author_rank: Super Contributor
timestamp: November 18, 2019, 02:40:40 pm
content: Metal tactile dome switches aren't that common. The classic membrane switch consists of two flex-circuits, usually single sided and cheaply screen-printed on a fairly crappy substrate, to provide the switch contacts and their interconnection matrix, facing each other and a separator layer with a button sized hole at each switch location. They may or may not be bonded together, and may or may not have a self-adhesive base layer for mounting and a printed and possibly embossed top layer to define and label the buttons.Most PC keyboards use membrane switches, and the only thing that makes them feel half-way decent is the quality of the actuator mechanism in each key that presses on the actual membrane switch.

author: Berni
author_rank: Super Contributor
timestamp: November 18, 2019, 03:43:49 pm
content: Quote from: Ian.M on November 18, 2019, 02:40:40 pmThe two layers of flexible circuit with separator as is used in PC keyboards is instead called a rubber dome switch not a membrane key. The circuit layers only form the switch contacts while the buckling rubber dome on top provides all the mechanical action and feedback. Its much like switches on TV remotes except that those don't have a plastic key on top and use a conductive rubber pad to bridge two PCB pads for the actual switching.I like these types of switches quite a bit more.But whenever you have a <1mm thick keypad with buttons that click there is almost guaranteed to be a metal dome under there for giving that clicking tactile feedback. They are just as cheep as rubber domes but can be made in much lower volumes due to no tooling cost.

author: Ian.M
author_rank: Super Contributor
timestamp: November 18, 2019, 04:13:28 pm
content: I think we are at odds over a matter of terminology - I contend that if at least one of the switch contacts isn't part of a flexible membrane, its *NOT* a membrane switch even if it has a similar form factor and application.

author: BIN.JRPANEL
author_rank: Newbie
timestamp: December 12, 2019, 08:56:16 am
content: For membrane switch , It is often used on household appliances or some medical and testing equipment. There are many buttons on it that can be used to control the use of the equipment.There are 2 ways to press the key, one is metal dome, and the other is Die embossing.Metal buttons, when pressed, there will be a ticking sound. For the die embossing key, it may not have a sound.Both of the 2 kinds are tactile key. Just press the key to connect the line to achieve the corresponding function.