Characteristics and applications of membrane switch
As we all know, the switch plays a role of transmitting instruction information in electronic machine products. There are many kinds of switches, and their development is constantly updated with the progress of electronic products. In the 1950s, key switch, toggle switch, change-over switch of discrete components were dominant; in the 1960s, combination switch represented by piano key switch appeared and completed simple function conversion; with the expansion of application field and the increase of whole machine function, conductive rubber keyboard switch appeared in the 1970s, while membrane switch is a new type of electronic device researched and developed in the late 1970s and early 1980s, which conforms to the needs of miniaturization, digitalization, intellectualization and multi-functional development of electronic machine products.
The membrane switch is a kind of contact switch, which is made by contact circuit printed by conductive paste on flexible polycarbonate or polyester membrane.
The membrane switch is a planar type electronic machine control system with multi-layer combination, sealed structure integrating key switch film, panel function mark, transparent reading display window, indicator light window hole and circuit.
The membrane switch has the following characteristics:
(1) durability
The service times of membrane switch can reach more than one million times of creeping generally. The reason why it has such a long service life is that the action of the switch is only realized by the vertical movement of the elastic membrane. Although the elastic membrane undergoes one million times of creeping, the creeping range is only 0.1 ~ 0.3mm (i.e. switch stroke). Furthermore, the material selection is rational, so it is far from reaching the limit of the membrane so that the membrane material can withstand more than one million times of creeping without deformation. On the other hand, the contact of the switch is vertical, and the wear extent is very small; the screen printed contact can form enough thickness, and a layer of conductive carbon is printed on the silver paste contact to achieve the purpose of high wear resistance and self lubrication, so the service life of the membrane switch is more than ten times longer than that of the mechanical contact switch.
(2) good sealing performance
As the membrane switch is an integral sealed structure, the contact of the switch is not subject to the erosion of harmful gases and is not easy to be oxidized; it has the characteristics of waterproof and dustproof, so it is more suitable for various harsh environments.
(3) small volume, light weight and reliable structure
The membrane switch can be arranged and combined into a membrane keyboard in the design. Its setting density is large, and it is a sealed sheet structure composed of multi-layer membranes. The connecting wires and leading-out between all switches are completed by screen printing at one time, with a total thickness of 1 ~ 3mm, which reduces the volume and the weight and improves the reliability.
(4) rich in color and beautiful appearance
Membrane switch can be personalized in the design of color pattern according to the user's design concept, and the comprehensive characteristics of material beauty, decoration beauty and process beauty can be reflected in the decoration effect.
(5) reduce the matching cost of mechanical and electrical products
The traditional mechanical switch needs to be welded when it is installed, even with the fixed bracket. The membrane switch is a paste type one, and as long as the back adhesive paper is removed, it can be firmly pasted on the surface of the whole machine with the adhesive side. Its lead outlet is inserted into the socket of the rear circuit of the whole machine, and the circuit can be connected in an instant. The membrane switch not only save labor and material but also reduce the matching cost of the whole machine.
Application of membrane switch
The membrane switch is a kind of non-self-locking switch. It is applicable to the working occasions with switch power less than 1W, maximum working voltage of 42V (DC) or 25V (DC) and maximum working current less than 100 mA. It can be widely used in all microcomputers, CNC, intelligent instruments, meters and electronic circuits with discrimination and memory functions and other fields.
