The overlay is an important part of a membrane switch. All membrane switches, of course, feature multiple layers. Like other switches, they circuit-controlling devices. You can press the buttons on a membrane switch to control a circuit. Membrane switches are distinguished from other types of switches by their laminated construction. They feature multiple layers that are laminated together, one of which is the overlay.

The Basics of a Membrane Switch Overlay

The overlay is the uppermost layer in a membrane switch’s construction. Also known as the membrane overlay, it features the graphics for the buttons while simultaneously protecting the underlying layers.

While their design may vary, membrane switches typically feature a few common layers. They feature an overlay layer, followed by a spacer layer, a rear adhesive layer and a tail filler layer. The overlay layer is simply the outermost layer. It’s the top layer that you can see and interact with when using a membrane switch.

What Is the Overlay Layer Made Of?

Different types of membrane switches use different materials for their respective overlay layer. One of the most common materials for overlay layers, though, is polyester. Polyester overlay layers are flexible, resistant to many chemicals and offer excellent optical clarity. All of these properties make polyester a popular material for overlay layers.

In addition to polyester, you can find overlay layers made of polycarbonate. Polycarbonate is a synthetic material. While it provides excellent optical clarity, however, it’s not as flexible as polyester, nor does it offer the same high level of chemical resistance.

Finally, some overlay layers are made of both polyester and polycarbonate. These “blended” overlay layers offer the best of both words. The disadvantage to choosing a membrane switch with a blended overlay layer, on the other hand, is the cost. They tend to cost more than overlay layers made exclusively or polyester or polycarbonate. But if price isn’t a concern, you may want to choose a blended overlay layer for your membrane switch.

Overlays and Embossing: What You Should Know

The overlay layer supports embossing as well. What is embossing exactly? It’s a finishing process that’s designed to create texture. By default, overlay layers are flat. They can be embossed, however, to achieve a textured surface.

Embossing options for overlays include pad, dome and rim. Each embossing option creates a textured surface. Rather than pressing a completely flat button, you can press a textured button in the shape of a pad, dome or rim.