Membrane Switch Keyboard

PET Membrane Switches

The membrane switch is an operating system that integrates key functions, indicating components, and instrument panels. It consists of four parts: panel, upper circuit, isolation layer, and lower circuit. When the membrane switch is pressed, the contacts of the upper circuit deform downward and make contact with the plate of the lower circuit. After releasing your finger, the contacts of the upper circuit bounce back, the circuit is disconnected, and the loop triggers a signal. The membrane switch has a rigorous structure, beautiful appearance, and good sealing performance. It has the characteristics of moisture resistance and long service life. It is widely used in electronic communications, electronic measuring instruments, industrial control, medical equipment, the automobile industry, smart toys, household appliances, and other fields.

As a membrane switch has three layers or more. However, most membrane switches include three to four layers, but also different applications, and different layers structure.

PET key membrane switch

The key embossing type includes conveying the key points on the upper line to enhance the feel. The rest includes the isolation layer, lower wiring, and optional panel printing
The principle is the same as the ordinary type. When the panel key point and the raised part of the upper circuit contact the lower circuit, electronic contact (signal) is generated.
Although the operating and storage environment limits PET convex keys, the convex keys can basically be adjusted to different strength requirements.

Introduction to specific types of membrane switches

Flexible membrane switch

A flexible membrane switch is a typical form of membrane switch. This type of membrane switch is called flexible because the mask, isolation, and circuit layers of the membrane switch are all composed of flexible films of various properties.

The circuit layer of the flexible membrane switch uses polyester film (PET) with good electrical properties as the carrier of the switch circuit pattern. This layer is divided into feel elastic pieces and upper and lower circuits. Due to the properties of the polyester film, the membrane switch has good insulation, heat resistance, bending resistance, and high resilience.

The graphics of the switch circuit, including the connection of the switch and its lead wires, are printed with low-resistance, conductive paint cured under low-temperature conditions. Therefore, the entire membrane switch has a certain degree of flexibility and is not only suitable for use on planar bodies but can also be matched with curved bodies. The lead wire of the flexible membrane switch is integrated with the switch body itself. When making the connection of the group switch, it is gathered at a certain point of the membrane and extends outward according to the position specified by the design and the standard line spacing. As a soft, the sealed lead wire that can be bent at will is connected to the rear circuit of the whole machine.

Rigid membrane switch

A rigid membrane switch means that the switch pattern and circuit are made on a common printed circuit copper-clad board. The characteristics of the rigid membrane switch are convenient materials, stable technology, low resistance, and certain components in the circuit that can be directly welded on the back. When the area is not large, the hard lining layer can be omitted. Rigid membrane switches generally use metal guides as conductive labyrinth contacts, so they have a better feel. The disadvantage is that the installation in the whole machine is not as convenient as that of the soft membrane switch, and it often needs to be welded and the leads drawn out through flat cables. In addition to buzz signals and LED indicators, the information feedback of rigid membrane switches can generally use metal feel shrapnel.

Flat membrane switch

The buttons on the membrane switch use different colors to indicate the position, shape, and size of the key body, which is more common in the initial stage of membrane switches. Three-dimensional membrane switch: Usually, the buttons on the membrane switch just use color to express the position, shape, and size of the key body. In this way, the accuracy of the operation can only be identified by the operator’s vision. Since there is no appropriate feedback information to indicate whether the finger is pressed within the effective range of the switch to make the switch operate, this affects the confidence in monitoring the entire machine and the speed of operation. A membrane switch that makes the switch key body slightly convex and slightly higher than the panel to form a three-dimensional shape is called a three-dimensional key switch. Three-dimensional keys can not only accurately determine the range of the key body, improve the recognition speed, and make the operator’s touch more sensitive, but also enhance the decorative effect of the product’s appearance. Production of three-dimensional keys.

Raised membrane switch

Usually, the keys on the membrane switch just use color to express the position, shape, and size of the key body. In this way, the accuracy of the operation can only be identified by the operator’s vision. Since there is no appropriate feedback information, the confidence in machine monitoring and the speed of operation are affected. Therefore, arrangements must be made during the design stage of the panel to provide process holes for precise positioning during mold pressing. The height of the three-dimensional protrusions should generally not exceed twice the thickness of the base material. To improve the appearance of the product, the protrusions of the raised membrane switch can be made in many variations.

Membrane Switch Keyboard Classified by Structure

Long service life but non-tactile;

Has a good tactile feel, but has a relatively short service life;

Beautiful appearance, strong three-dimensional sense, but no touch;

The appearance is beautiful, has a strong three-dimensional sense, and has a tactile feel;

Type (a): When the design is improper, it is easy to have a two-stage phenomenon, but the panel is damaged and the electrical performance is still there;
Type (b): There is no two-stage phenomenon, and there are few structural layers, which is more economical. If the panel is damaged, the electrical performance will not exist;

Type (a): It is the most basic and commonly used structure. The shrapnel plays the role of both touch and line;
Type (b): has a complex structure and is used in situations where there are many and dense shrapnel and no jumpers are required. The shrapnel is placed on the upper line, the conductive surfaces of the upper and lower lines are upward, and the upper line needs to be punched. When this structure is turned on, the four legs of the shrapnel are not in the same plane as the center point, and there are “two sections”. At the same time, the shrapnel is often in an excessively concave state. After a long time, the shrapnel will not rebound, so it is not recommended;
Type (c): The shrapnel is placed on the upper line and only plays a tactile role. The conductive surface of the upper line is downward and the conductive surface of the lower line is upward. If there are “two sections”, it is not recommended;
Type (d): The shrapnel is placed on the lower line, and there are traces on both the upper and lower wires. The shrapnel not only functions as a tactile sensation but also connects the upper and lower lines; it is used when the shrapnel is dense and does not have jumps. In the case of wires, the structure is simpler than type (b). When designing, attention should be paid to routing the circuit to avoid the four legs of the shrapnel to ensure there is no short circuit.

Be sure to open the bottom plastic mold;
(a) The LED circuit and the lower circuit are on the same layer: the structure is simple, but if the height of the selected LED lamp is higher, the LED lamp will lift the panel. At this time, the LED window on the panel should be convex or the surface adhesive layer should be thickened. The thickness makes it thicker than the thickness of the LED lamp;
(b) The LED circuit and the lower circuit are on different layers: The structure is complex, but the LED window does not have to be convex, but the area above the LED light must be hollowed out to prevent light from passing through the LED light hole. Note: When wiring the wiring at this time, you need to avoid wiring around the LED light hole.

This type can avoid jumpers and does not require drilling holes so that the conductive surface can be downward. The disadvantage of this structure is that the lines are easily broken at the fold.

The outer frame is a closed frame with no wiring. It protects the inner frame and prevents moisture from entering the casing from the outlet groove.

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