Backlit 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been replaced by EL lamp backlighting and LGF backlighting
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
|Item||LED Backlighting||EL Lamp Backlighting||LGF Backlighting|
|Manufacturing Ddifficulty Level||Easy||Easy||Difficulty|
|Backlighting Uniformity||Bad||Much Better||Better|