Unique Features of Different Types of Domes Used In A Tactile Membrane Keypad

 A membrane keypad may be made up of tactile and non-tactile switches. The tactile switches are fitted with metal domes and provide the users with tactile feedback after pressing a key. The non-tactile switches may not provide the users with tactile feedback. However, the entire keypad or each non-tactile membrane key is backlit using LED, LGF, EL or a combination of fiber-optic films and LED. The backlit keys become illuminated after being pressed. Thus, tactile and non-tactile membrane keypads can both provide the users with feedback.

It is possible to add the metal domes of varying sizes and shapes when manufacturing a tactile membrane keypad. The metal domes are fitted to the underside of the graphic interface. They are open contacts that complete the circuit once a membrane key has been pressed. The metal domes can provide the users with consistent tactile response alongside enabling the manufacturing companies to create durable switches that can be used in any type of environment. The metal domes are made of stainless steel. The performance of a tactile keypad depends largely upon the venting of metal domes. In tactile keypads, the air moves in and out from under a metal dome and the phenomenon is known as venting.

A tactile membrane keypad has to be adequately vented in order to perform properly. The absence of venting or inadequate venting may have adverse effects on the function and feel of a tactile switch. The metal domes fitted to a membrane keypad may be four-legged, round, triangular, oval or square in shape. Their size varies depending upon the size of the user-interface. A manufacturing company may customize the shape of metal domes based upon the specifications of different clients alongside customizing their size. The four-legged metal domes are also known as cross metal domes. They are integrated to silver-flex membrane switches, single-sided or double-sided PCB switches and FPC circuits.

The four-legged metal domes last longer than the triangular domes and produce better ‘snap feel’ than a circular or oblong dome. The lifecycle of this type of metal dome is usually higher than one-million. The circuit boards of some of the membrane keypads are made up of two or more layers. The circular/round metal domes are integrated into this type of circuit board. It is also possible to fit this type of metal dome to a precision switch. The circular metal domes are smaller than the four-legged domes and are ideal for a smaller user-interface.

The triangular metal domes are used on a single-sided or double-sided PCB, silver-flex membrane keypad or FPC circuits. The triangular domes can be used with small user-interfaces, such as user-interface of small handheld devices. They can generate a click feel once a switch has been pressed. The triangular metal domes have two legs and can handle up to 6,000 gram-force. For more information visit here: CSI Keyboards, Inc.