Metal domes are used in membrane switches and keypads to facilitate an electrical connection from the keypad to the product itself. Electrical switches are necessary in almost every HMI (human-machine interface) device. Every electrical switch is used in a different way and in a different environment and thus the importance of choosing the correct dome for the spcific application and enviroment. There are a few things to keep in mind when searching for the right dome for a particular application listed below.
Size: Measured in diameter and height of the dome. The size of the keys on the membrane switch will obviously determine the size of the dome required for the application.
Shape: The typical dome shapes are as follows:
Actuation Force: The actuation force is one of the most critical characteristics when choosing a dome. Actuation or trip force is the minimum force needed to depress the dome. The actuation force has a significant effect on the lifecycle of the dome. A higher actuation force results in a lower life expectancy. When choosing a dome that needs to last a long time, it is best to choose a low trip force while finding a balance that gives enough tactile feedback to the user while keeping the lifecycle of the dome in mind. One application may need the trip force to be low and more sensitive to touch while another may need it to be less sensitive and use greater pressure to complete the circuitry. For example, if the users wear gloves, a higher trip force is usually needed in order for them to feel the activation.
Lifecycles: Domes have come a long way since their inception. Originally, domes were only rated for thousands of cycles. The standard for domes is now at least one million cycles, with specialized domes rated for at least five million cycles. No matter the application, there is a dome that can meet your lifecycle requirements.
Dimple or Non-Dimpled: Looking at a variety of domes for different applications, users may notice a little dimple located in the center of the dome. The dimple is a small concave feature located on top of the dome, and can be as deep as 0.2 mm (0.008 in.). The purpose of the dimple is to provide better electrical characteristics and to reduce contact bounce, but this is mostly irrelevant on a membrane switch.