The membrane switch backlighting design for the difference Human Interface Device

hqtJul 13, 2020

The electric industrial revolution begins from around the end of the 19th century. The human interface device is born at the right moment. The original human interface device design request is very simple. They need the goods can be goof for manufacture and the function can be stabilized. Even though the goods are very cumbersome and un-humanization. The membrane Human Interface Device is begun from around the middle of the 20th century. NASA looking for the very thinner and stabilize Human Interface Device. Then make the research and develop such a new device.

With over 170 years of development, the original device now develops very well. Such as very beautiful, very small and light, very humanization, and very easy to use. The current device not only allows the user to get the special tactile feeling but also gives the user a very beautiful appearance. Here I would like to talk about the backlighting design of the different human interface device which used very often around our life.

The backlighting design of the membrane switches

With the standard membrane switches, there may contain the difference tactile metal domes design, contain the indication LEDs design, but such membrane switch without the backlighting design upon the keys. For catching the backlighting problems, we add the Light Guide Film under the text & patterns where need to be light up, we also need to solve the lighting homo problems, solve the keys tactile feeling problems, solve the lighting spread to each other’s and outline problems, solve the series production problems. To improve to get a better result, we make many tests with different techniques and raw material.

Now, we know the technology very well, and the LGF membrane switch still keeps the very thinner thickness and beautiful appearance design, they like the standard membrane switch, just with the side SMT LEDs as the backlighting design.


The other backlighting design is EL-Panel

The Electro Luminescence short for “EL”, the EL-Panel can be as the backlighting design. Actually, some of the membrane switches also can use the EL-Panel as the backlighting (Not the SMT side LEDs as the backlighting).

But there have some points that design use the EL-Panel as the backlighting.

1. There needs a very high power than can lighting the EL-Panel(Also need to design the extra actuator on the end control machine).

The EL-Panel need the at least 50Voltage power can be work, the SMT side LEDs only need 2V power can be work.

2. The life-time of the EL-Panel is around 5000~10000 hours, the SMT side LED’s life-time is around 50000~100000 hours, the SMT LEDs have the much longer life-time.

3. The EL-panel is can be designed very clear around the outline size, as the EL-Panel lighting is from the “self-luminous”, the lighting can be an easy design to be very homo, and the lighting not easy to spread to the outline size, there no need to design the extra lighting-barrier.


The backlighting design for the phones or other’s graphic overlays

The switch can be without the tactile feeling keys, and there can be design the touch feeling keys. Such as a cellphone. They use the capacitive sensing circuits design. Such backlighting design also with the SMT side LEDs and add the LGF plate that helps the lighting diffuse homo. Such technology also used very often at the advertising board. (Though the LGF technology for the advertising board not very high technology).


The backlighting design for the micro-switch

The backlighting design for the micro-switch is much easier because there no need for the LGF plate design. But such design required very much space with the keys. It’s hard to design the backlighting with the very thinner. And also, there needs to design extra transparent plastic pads to help the lighting diffuse and improve keys tactile feeling. There allow design the keys with more space (More thickness) will help the lighting more homo. The tooling cost is very complex and also cost very higher.

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