Backlight Membrane Switches means that there is light source from the backside to light the graphic overlay and provide the indication information to users or when the product used in the night or dark environment it can light the graphic and make the users or workers make buttons press operation correctly and avoid pressing wrong buttons.
There are several types of backlighting ways for the membrane switches. They are:
1) LED backlighting memmbrane switches;
2) EL lamp backlighting membrane switches;
3) LGF(Light Guide Film) backlighitng membrane switches;
4) Fiber backlighting membrane switches (seldom used in nowadays due to its complex manufacturing process and very high cost.It has been replaced by EL lamp backlighting and LGF backlighting technology);
For the LED backlighiting keypads, the graphic overlay lighted by the backside LEDs which assembled on the flex or rigid circuit layer. By this way, it is very simple and also economical. But it couldn't get a even lighting effect on surface. For this backlighting method, the LEDs can be assembled under centered buttons also can be assembled beside of the buttons or other areas. For the products need each button be backlighted, usually design the LEDs under the center of the buttons, then use the center holed metal domes and print transparent color on the graphic overlay. By this way the center button will be much brighter than sides of it. But this way is easy to achieve and also its cost is the lowest. This is suitable for those products no very high requirement for the evenness of the backlighting.
For the EL lamp backlighting membrane keypads, the graphic overlay will be backlighted by the EL lamp layer under the overlay. EL( Electroluminescence)：Electroluminescence means luminescence produced by high energy generated from electrons which are accelerated within phosphors when an alternating current is applied to a luminous layer consisting of phosphor powder. EL lamp's light is very even and the manufacturing process is also simple. But the end users need design an additional connection port for the EL lamp layer. Also this kind of backlighting keypad need another driver to match the EL lamp in the keypad. We can provide the EL driver to match our EL lamp backlighting membrane keypads.
As to the LGF backlighting membrane keypads, it is the current most popular backlighting technology. LGF is light guide film. LGF itself is not a light source. It couldn't produce the light. It still need the LEDs assembled on the circuit layer to produce the light source. But LGF can guide the light from the LEDs to top overlay evenly. For this backlighting keypad, it can save the LEDs quantity and it also can get a even backlighting effect with less LEDs. But by this way the difficulty is adjusting the refraction dots on the LGF layer. Adjust the direction of dots, density, position etc. And its tool fees is higher.
Bellow is their difference and advantages&disadvantages for your reference:
||EL Lamp Backlighting||LGF Backlighting|
|Manufacturing Ddifficulty Level||Easy||Easy||Difficulty|
|Backlighting Uniformity||Bad||Much Better||Better|
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