What is a Dome Switch Keypad?

When it comes to membrane switches, you basically have two options: a flat panel membrane switch or a dome switch membrane keypad. Dome switch keypads uses two circuit board traces under a flexible keypad using a metal dome. Metal domes (metal snap domes, or tactile metal domes), made of stainless steel, are momentary switch contacts that, when used in conjunction with a PCB, flex circuit, or membrane, become normally-open tactile switches.

The main advantage of dome switch keyboards is the strong, crisp tactile snap or feedback. Because they are typically made of metal, they produce a crisp snap when pressed or actuated. In addition to giving tactile feedback (the user realizing they have pressed the key), the dome also assists in reducing typing errors and subsequently improving accuracy.

Another major benefit of the dome switches are the the long lifespan when compared to other styles of keyboards. Standard dome switch keyboards are rated up to one million to even five million cycles.

Furthermore, dome-switch keyboards can be plated in a variety of metals, including nickel, silver or gold. There are many different shapes and sizes of the domes. Additionally, there are different actuation forces from low force to high force. CSI can work closely with you in choosing the right dome to ensure best performance and tactile response for your application.

Typical Dome Shapes:

Four legged
Triangle
Round
Oblong
Custom

Understanding Dome Actuation Forces:

Actuation force is the amount of force that is necessary for the dome to snap, changing the dome from the open position to the closed position. Typical actuation forces range from 40 grams, to 2,250 grams or higher depending on the size. Dome actuation force is typically measured in grams. The release force is the amount of force the dome exerts on itself to return to its relaxed state.The combination of actuation force and release force gives you the tactile ratio for a dome. The higher the tactile ratio, the “crisper” a dome feels when actuated.

Internal Venting for Dome Switches:

When the dome is depressed, air is trapped underneath the dome. To avoid compressing the air under the dome when actuated, it is recommended that a vent channel is incorporated in the design. The venting of the dome can be achieved a number of different ways. Not properly venting the dome will result in significant loss of tactile response and potential issues with air entrapment under the membrane surface.

How Do I Choose the Right Dome for my Membrane Switch?

The CSI engineers will work very closely with you in deciding which dome is best for your application. Typically the decision is based on the force of the dome (how soft or hard of a press it takes to actuate the dome). CSI can also mock up different sample keypads with different dome options so the customer can decide through a more “hands-on” approach.

To recap, dome-switch keyboards are a hybrid of flat-panel membrane and mechanical-switch keyboards. They offer strong tactile feedback, a long lifespan, and they can be plated in a variety of different metals. A variation of dome-switch is the scissor-switch, which is often used in laptops and similar electronic devices. Hopefully, this gives you a better understanding of dome-switch keyboards.