Characteristics, Applications, and Classification of Membrane Switches

1. Characteristics

As is well known, switches play a role in transmitting command information in electronic products. There are many types of switches, and their development is constantly updated with the progress of electronic products. In the 1950s, toggle switches, toggle switches, and toggle switches dominated with the use of power components; In the 1960s, combination switches represented by piano key switches emerged to complete simple functional conversions; With the expansion of application fields and the increase of overall functions, conductive rubber keyboard switches emerged in the 1970s, and membrane switches were a new type of electronic device researched and developed in the late 1970s and early 1980s. It is a product that meets the needs of miniaturization, digitization, intelligence, and multifunctionality of electronic products.

Thin film switch is a type of contact switch made by printing contact circuits with conductive paste on flexible polycarbonate or polyester film.

The membrane switch is a planar, multi-layer combination, sealed structure that integrates key switches, panel function markings, transparent reading display windows, indicator light windows, and circuits into an electronic control system assembly.

It has the following characteristics:

(1) Durability

The lifespan of membrane switches can generally reach over one million times, and the reason for such a long lifespan is that the action of the switch is only achieved by the vertical movement of the elastic membrane. Although the elastic film undergoes millions of creep cycles, the amplitude of creep is very small, only 0.1~0.3mm (i.e. switch stroke), and the rationality of material selection has not yet reached the yield limit of the film. Therefore, the film material can withstand more than one million cycles without deformation. On the other hand, the contacts of the switch are in vertical contact, with minimal wear and tear; The contacts of screen printing can form sufficient thickness, and an additional layer of conductive carbon is printed on the silver paste contacts to achieve high wear resistance and self-lubricating properties. Therefore, the lifespan of thin film switches is tens of times longer than that of mechanical contact switches.

(2) Good sealing performance

Due to the integral sealing structure of the membrane switch, the contacts of the switch are not corroded by harmful gases and are not easily oxidized; It has the characteristics of waterproof and dustproof, making it more suitable for use in various harsh environments.

(3) Small size, light weight, and reliable structure

The membrane switch can be arranged and combined into a membrane keyboard in design, with a high density of settings. It is a sealed thin sheet structure composed of multiple layers of membranes. All the connecting wires and lead out wires between the switches are completed by screen printing at once, with a total thickness of 1-3mm. Therefore, it reduces the volume, reduces the weight, and improves reliability.

(4) Rich colors and beautiful appearance

Thin film switches can reflect personalization in the design of color patterns according to the user's design concept, and showcase the comprehensive characteristics of material beauty, decorative beauty, and craftsmanship beauty in decorative effects.

(5) Reduce the supporting costs of electromechanical products

Traditional mechanical switches require welding and even matching with fixed brackets during installation. The installation of the membrane switch is adhesive type. As long as the adhesive paper is removed, it can be firmly attached to the surface of the whole machine. Its lead outlet is inserted into the socket of the rear circuit of the whole machine, and the circuit can be instantly connected. Save labor, save materials, and reduce the supporting costs of the entire machine.

2. Application

Membrane switch is a non self locking switch. Suitable for working environments with switch power less than 1W, maximum operating voltage: 42V (DC) or 25V (DC), and maximum operating current less than 100 mA. It can be widely applied to all microcomputers and numerical control. Intelligent instruments, instruments, and electronic circuits with discrimination and memory functions in various fields.

3. Classification of membrane switches

Thin film switches can be classified according to two main characteristics: usage environment or circuit substrate. According to environmental classification, it can be divided into two categories: decorative membrane switches and military membrane switches; According to the circuit substrate, that is, according to the formation method of the circuit, it can be divided into two categories: conductive printed circuit and copper-clad etched circuit.

(1) Commercial membrane switch

The assessment criteria for high and low temperatures, constant humidity and heat, and temperature changes of membrane switches in the Chinese machinery industry standard JB5045-91 "Technical Conditions for Membrane Keyboards", which was released on July 1, 1991 and implemented in 1992, are:

High temperature: (55+/-2) degrees (72 hours)

Low temperature: (-40+/-3) degrees Celsius (16h)

Constant humidity and heat: (40+/-2) degrees {relative humidity of 96%+/- (2-3)%, duration of 96 hours}

Temperature change: -40~50 degrees (after 5 cycles of testing, recover for 2 hours under normal atmospheric conditions)

Any membrane switch that meets these assessment criteria and has the general function of a membrane switch can usually be referred to as a commercial membrane switch. It is the most common and distinctive product among membrane switches.