Slim, flexible, and extremely customizable, membrane switches are the product designer’s perfect partner when crafting human-machine interfaces.
Functionally, membrane switches work much like a mechanical switch. However, by being printed on either flat PET (a plastic) or ITO (a transparent conducting film), membrane switches offer significantly more compact designs and take up less space than other input devices. That gives product engineers and designers improved opportunities to design effective and user-friendly products.
You can learn more about membrane switches – including specific benefits and how they compare to mechanical switches – in our post, “What is a membrane switch?” In this article, we’re going to look inside the membrane switch to better understand its construction. Since membrane switches come in a series of flat layers, we’ll discuss each layer.
View an animation of the composition of membrane switches here.
1: A graphic overlay and laminating adhesive
The topmost layer is a graphic overlay that serves as the primary point of interface between the membrane switch and the human user. Usually made from polyester (thanks to its durability and lifespan), the graphic overlay displays the specific input options (buttons) available to the user.
Many other construction options are available. Some are cosmetic – such as incorporating colors and branding elements – while others can have a profound impact on the overlay’s lifespan and suitability to different applications. For example, instead of polyester, you might choose polycarbonate material, thanks to its superior temperature resistance, if the application requires it.
A laminating adhesive (usually acrylic) then binds the graphic overlay to the circuitry.
2: Circuitry layers
These layers involve two layers of circuits printed with conductive ink and separated by a spacer. The spacer prevents continuous contact between the circuits, so they remain open until pressure from a finger or actuator is applied. When pressure is removed, the circuit opens again, and the switch returns to its resting state. The lower printed circuit usually includes a tail that will connect the membrane switch to the machinery via controller PCB or some other electronic component.
3: Final layer of laminating adhesive
The final adhesive layer binds the entire membrane switch assembly to the enclosure or other rigid backing material. It bears noting that this layer must be durable and enduring. The needed bond strength will affect the specific materials used and will depend on the specific application.
4: Optional layers
Some membrane switches will involve additional layers as well.
For example, if you want to improve tactile feedback, you might add a dome retainer layer. Raised keys allow the user to feel where the key is located and receive greater tactile feedback when it is pressed/released. The material used will make a significant difference in user experience and equipment lifespan. For example, Hoffmann + Krippner’s GT material automatically resumes its original shape even after damage or distortion, enhancing lifespan and usability. Another optional layer might involve back lighting options. For example, Hoffmann + Krippner can combine side-LED and light diffusing panels to offer a virtually unlimited choice of colors.
Membrane switches can meet almost any need.
In short, membrane switches can be designed and engineered to meet almost any application and environment. In fact, versatility is one of the membrane switch’s major advantages compared to HMI options. The only question is, what do you need from your membrane switch? There’s almost certainly a way to construct it to fit your exact use-case scenario.
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