Metal domes have grown ever more popular over the past few years. They have become the go-to choice for custom silicone keypad assemblies that require a tactile response. Metal domes are typically made from stainless steel, have a switching capacity of 1 watt, switching voltage of .1 to 50 VDC, 0.005 – 100 ma DC switching current, and come in various types of coating options including Nickle, Silver and Gold. The typical life cycle of metal domes is 5 million actuations and they operate from temperature ranges of -45° C – +100° C. There are four main types of metal domes, which include triangle or three-leg, circular, four-leg and oblong.
Triangle domes or three-leg domes, are typically used in applications that require a strong tactile response. These domes can reach ranges of up to 6,000 grams force. Triangle domes typically also come with legs, which allow them to be mounted to the circuit board without the use of adhesive. This allows the domes to be used in high-temperature applications, where the adhesive would otherwise cause a unit to fail. Triangle domes typically have a 5mm-13mm range of size.
Circular metal domes look just like the sound. These domes are also called round domes by some companies. Circular domes have longer life cycles than triangular domes, and work great in applications that require a low profile switch under a membrane overlay. Typically, the size of a circular dome is from 3mm to 20mm in diameter and the range of force is usually 100-600 grams of force.
The next type of dome is the four-leg metal dome or cross metal dome. These domes were designed specifically for use where traces of positive and negatives can be designed under the dome on the same side of the circuit. Four-leg domes have a better clicking feel than circle and oblong domes. Four-leg domes are the tallest of the domes and are not to be used in low-profile applications. Generally Four-leg domes come in a 5mm-20mm range of size, and a typical force range of 125-500 grams of force.
The last main type of dome is the Oblong metal dome, sometimes called oval or rectangle metal dome. The main application for oblong domes, is a low profile switch on a circuit board with little to no room that can allow for a long and narrow metal dome. These domes can also be used in applications with longer or larger keys, for example a space bar on a keyboard. This ensures that the metal dome is hit when the key is depressed. The dome size can vary between 3mm X 4mm up to 51 mm X 13.70mm with the force range between 100-500 grams force.
Metal domes are becoming the new standard for keypad assemblies and membrane switch designs. New dome styles are coming out every year. If needed, custom built metal domes are even available for applications. Here at SiTech we have experience using all types of metal domes, and dome custom dome arrays. If you are interested in having your custom silicone keypad quoted or simply wish to learn more about metal domes, give us a call at: 757-887-8488, or submit a quote.
