Membrane switch is an operating system that integrates button functions, indicating elements, 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 are deformed downwards and are in contact with the plates of the lower circuit. After the finger is released, the contacts of the upper circuit bounce back, the circuit is disconnected, and the circuit triggers a signal. Membrane switch has rigorous structure, beautiful appearance and good sealing performance. It has the characteristics of moisture resistance and long service life. Widely used in electronic communication, electronic measuring instruments, industrial control, medical equipment, automobile industry, smart toys, household appliances and other fields.
Membrane switches have a wide range of applications, so the structure and process are also different for different users, environments, and terminal equipment. Let's talk about some common membrane switch types.
1. Metal shrapnel (dome) type: use metal shrapnel as the conduction medium.
advantage:
★ The key feels good, the strength is uniform, and the stroke accuracy is high;
★ You can hear crisp sound during operation, you can clearly know the operation situation, and avoid repeated operations due to the buffer time of some equipment;
★ The operating temperature can reach -20 ～ 80 ℃
shortcoming:
When the liner is uneven or pasted on the bending arc is too large, the shrapnel may cause short circuit, malfunction and non-rebound phenomenon.
suggestion:
☆ Use it on a flat backing board that can withstand the force of the keys, or directly use a thicker PCB board as the circuit layer.
2. Hot-pressed convex handle type: After printing the contact surface with film material, the bumps are rolled to form resilience.
advantage:
★ Long service life, can reach more than 500,000 times;
★ Feel good, stroke and strength can be customized according to customer needs;
shortcoming:
☆ The cost of the mold is high, and the convex mold needs to be opened;
☆ Use in a high temperature environment may cause the key force to weaken.
suggestion:
The metal mold of the convex bud mold can ensure the consistency of the key force and stroke.
3. Flat light touch type: the contact point uses a film substrate to print conductors, and does not use secondary processes
advantage:
★ The button has a long service life and can reach one million times;
★ The conduction contact area is large to ensure the conduction rate.
shortcoming:
☆ No operating feel, easy to cause repeated operation or misoperation;
suggestion:
The distance between the keys should be enlarged as much as possible, otherwise the failure rate will be increased and the service life will be shortened.
4. Capacitive sensing type: use conductors to induce conduction.
advantage:
★ Like a capacitive touch screen, it can sense actions within a certain distance;
★ Sensing distance can be designed according to customer's designation.
shortcoming:
☆ The pass rate of finished products is low, sensitive to surrounding electromagnetic interference, and the design requirements are very high;
☆ Relevant electronic components and chip support are required.
5. LED light guide plate type: On the basis of ordinary membrane switches, the built-in light guide plate enables the product to be used in places with insufficient light.
advantage:
★ The product is high-end, atmospheric, and the light-transmitting part can be customized according to customer needs;
★ It can be operated conveniently in places with insufficient light;
★ Colors can be customized according to customer requirements, generally: blue, red, orange, white, green.
shortcoming:
☆ Due to the limitation of the astigmatism of the light guide plate, the thickness of this type of switch is relatively thick. Generally: 2.5mm～3.5mm
6. EL cold light type: EL cold light source is embedded in the conventional membrane switch.
advantage:
★ Compared with the LED light guide plate type, the thickness is greatly reduced. Generally between 1.5mm and 2mm;
★ The cold light source is suitable for the normal open state, without taking into account the heating problem;
★ The luminous area and color can be customized according to customer needs.
shortcoming:
☆ The cold light source needs to be equipped with a driver
7. PCB circuit type: use PCB circuit board instead of thin film circuit layer
advantage:
★ The precision of the PCB circuit is high, the welding LED is more solid and reliable, and the resistance value is lower;
★ The thickened PCB circuit layer can be directly used as a lining board.
shortcoming:
☆ PCB is a rigid material and cannot be bent.
8. FPC circuit type: membrane switch circuit layer adopts FPC (flexible circuit board)
advantage:
★ The FPC circuit has high precision, the welding LED is more solid and reliable, and the resistance value is low;
★ It can resist bending like film printed circuit.
shortcoming:
☆ The cost is high, and the quantity requirements are large.
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