Membrane switches are amazing tools for product designers looking for a cost-effective yet highly functional means of interaction between user and device. We discussed how membrane switches are constructed here. In brief, membrane switches work much like mechanical switches, but rather than using mechanical parts with a separate switch for each key, the electric circuit is printed on a single, continuous, thin membrane (hence the name). But how exactly do these membrane switches work?
The basics: How membrane switches work.
The top layer of a membrane switch is an overlay with the keys that the user sees and touches. Beneath that top layer are two circuit layers, which are printed in conductive ink (like copper, silver, or graphite) onto the membrane (usually polyethylene terephthalate, or PET) to create circuits that correspond to the buttons. A spacer prevents continuous contact between the circuits, so they remain open until pressure from a finger or actuator is applied.
Thus, when the user does press a button, it completes a printed circuit specific to that key. By identifying the specific circuit that was activated, the processing unit knows which button was pressed; it then generates an appropriate corresponding output signal.
In other words, when the user pressed the “1” key, the pressure completes a circuit printed onto the membrane just below that button. That circuit transmits a signal to the processing unit, which understands that the “1” key was pressed and in turn populates the display with a “1”.
What about added functionality?
When they were originally developed decades ago, membrane switches were not very reliable. The materials and construction technologies were prone to problems that made them vulnerable to maintenance issues and shortened their lifespan. However, modern production methods have improved dramatically on what membrane switches can do and how they operate.
For example, tactile layers can be integrated into the design, and domed (raised) keys can also offer a better tactile response when operating, reducing input errors and improving user experience. When the user presses a domed key, the material in the button flattens out and presses the circuit layers together, then springs back into its original shape when the user lifts their finger.
Modern technology can have a real and pronounced impact on the utility of membrane switches, e.g. measurably increasing lifespan. For example, Hoffmann + Krippner’s domed keys with GT technology provide a raised key feature that incorporates self-healing features to provide unparalleled durability and longevity. The GT material creates elastic domes that can reform their original shape, with no scratch or deformation, even after being damaged.
Membrane switches can meet almost any need.
So, that’s our quick overview of how membrane switches work. We should note, however, that some variation in operation is possible from what is described here. Versatility is one of the membrane switch’s major advantages compared to other interface options. With so many possibilities, not all membrane switches will work exactly alike. The only question is, what do you need from your membrane switch? There’s almost certainly a way to make it work in your exact use-case scenario.
Technical wordsmith and guest blogger for Hoffmann + Krippner.