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Everything you need to know about membrane switches

Membrane switches are generally simple momentary push-button switches. My first encounter with membrane switches was with a kit computer, the Sinclair ZX81. The keyboard was a pretty awful membrane keypad.

You had to press it fairly hard to register a keypress and there was hardly any movement However, it must have been cheap to produce and it enabled the computer to be made at a price that was groundbreaking.

My next encounter with a membrane keyboard was the Sinclair Spectrum. This had plastic buttons over the top which made it much easier to use than the ZX81. There was also move physical movement so there was more tactile feedback.

What is a membrane switch?

A traditional switch usually has metal contacts and moving parts. The metal contact is sometimes coated to improve its lifespan. There are a huge number of different types but the process is similar in that metal parts complete an electrical circuit.

Membrane switches usually don’t have metal parts for the contact. They are normally made up of layers of conductive material. When you apply pressure, two parts of the conductive material touch. This completes an electrical circuit in the same way that a mechanical switch does.

What are the advantages of a membrane switch?

A membrane switch has many advantages over a mechanical switch. One of the major ones is price. You can specifically manufacture an array of them at a much cheaper price than it would take to assemble and produce from mechanical key switches.

This is one of the reasons they were able to produce the ZX81. The kit came out at not much more than it would have cost to produce just a mechanical computer keyboard in those days. Another advantage was size. You could produce a custom membrane keyboard in a miniature size, as small as you could practically operate with your fingers.

This was a lot smaller size than you could produce an equivalent mechanical keyboard. This was one of the reasons why the ZX81 was able to be produced in the miniature size that it was.

Life span

Depending on the materials that are used to manufacture the membrane switches they can have a very long life. It does depend on what the materials are as the term membrane encompasses a type of switch and not specific switches.

Because of the way switches are made in layers they are a lot more resistant to water dirt and dust than the typical mechanical switch. They can be easily designed so the bottom layer is a printed circuit board making the whole construction process easier with no wiring and the top layer can have graphic overlays printed making that part easy to integrate with the case.

What are the disadvantages of a membrane switch?

The early ones were basically a few layers that were no thicker than a piece of cardboard. There wasn’t much physical movement and they required a fair bit of pressure to use. The lack of movement meant they weren’t very tactile and it wasn’t always apparent if they had registered that you had pressed them or not, so you usually needed some form of feedback.

With the ZX81 there was the screen so you could see what you’d typed. If a membrane switch becomes faulty or damaged you can’t very easily repair or replace it. You usually have to replace the whole array. With keypads or keyboards that are made up of mechanical switches, you can replace a single switch.

Where are membrane switches used?

In a word everywhere, ok that doesn’t help you much if you looking for specifics. In the home, looking around a typical kitchen and you have the microwave that has membrane switches on the front to operate it. Likewise, the air fryer that has them on a keypad on the top that incorporates blue LEDs. The fridge freezer has them and the dishwasher.

I also know from taking them apart that most tv remote controls have membrane switches. They are also heavily used in the medical, defence and aerospace industries in keypads, keyboards and control panels.

Membrane keypads

With traditional switches, to have ten switches on a panel would cost ten times as much.

With how a membrane switch is made it doesn’t cost much more to make a single membrane switch or a row of them. So a whole keypad doesn’t cost much more by having multiple membrane switches.

Everything you need to know about membrane switches – conclusion

Membrane switches started to be used in the nineteen eighties. They were quite basic but over the years they have evolved so much that in some cases it’s difficult for the user to know if the switch is membrane or mechanical. Most laptop keyboards are made up of membrane switches and a large number of computer keyboards are made up of membrane switches.

In more recent times metal domes have been integrated into the design which has made quite tactile membrane switches. This still hasn’t convinced everyone though. There are quite a few computer users who actively use mechanical keyboards, particularly gamers.

You can get more details about membrane switches here.