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Laser etching keyboard is used for the keyboard that requires backlight effect.
Spraying color of graphics, then color of keyboard surface, set graphics on laser machine, then laser etch graphics, this is the processing of painted laser etching keyboard.
Painted laser etching keyboard is commonly seen from music instruments, aircraft pad, phone pad, such as MIDI, simulated aircraft…
We have met some new problems during our cooperation with our clients, after different modifications and discussions, after tests, we solved these problems together, so we are willing to share with you our experience to improve works.
Let’s start the analysis based on whether painted laser etching keyboard with button webbing design and conduction requirement.
Painted laser engraving keyboard with button webbing design and conductive requirement:
1. Actuation force/pressing force. When the keyboard is designed with button webbing, you need to pay attention to the actuation force/press force first.
What is actuation force of laser engraving keyboard?
Please notice the below picture of button webbing structure, the force that you press down the button and make the conductive pad contact the PCB pad is the actuation force/pressing force.
What influences the actuation force/pressing force?
The button webbing, to be exact, the uniform and thickness of button/key webbing. Generally speaking, when the original keyboard is compression molded, the actuation force is about 100gram±30gram, but painted laser etched keyboard requires painting processes of graphics color and keyboard surface color, after two layers painting processes, the actuation force/pressing force will increase to 150gram±80gram, if the painted laser engraved keyboard requires surface protective coating, such as PU or oil/matte smooth coating, after the final protective coating finish, the actuation force will reach to 250gram±100gram.
The reason why the actuation force of laser engraving keyboard becomes so high is that for painted laser etching keyboard, each painting process can increase the thickness of its button webbing, we mentioned that thickness of button/key webbing can influence the actuation force, after several layers painting, the wall of button/key webbing becomes thicker, then the resistance is getting bigger, so you need to press the button with more strength.
Can the actuation be controlled by engineers?
Unfortunately, because the spraying process is done manually, the spraying uniformity is difficult to control. In addition, actuation force is not a fixed value, which can not be obtained by setting, and there is tolerance, and with the increase of actuation force/pressing force, the tolerance will become larger.
How to choose suitable actuation force for painted laser cutting keyboard?
Actuation force influences the assembly between keyboard and PCB pad, and also influences the tactile feeling. As for assembly, which needs tests to decide whether the electrical response is perfect (actuation force is just one reasons of imperfect electrical response), whether the button is jamming or stacking on the outer case (actuation force is only one reasons of button jamming), based on these two tests, you could solve the actuation force. Besides assembly, you could test by tactile feeling, but different people has different tactile feeling, which is not a fixed result.
For example: our client requires their painted (two layers color and one layer of PU coating) keyboard cannot exist button jamming and bad electrical response problem, meanwhile, the actuation force should be under 180gram, because they don’t want to press down buttons with more strength. After several tests, we found out that only when the actuation force is bigger than 200gram, the button jamming problem can be solved.
2. Spraying painting color layer. For painted laser etched keyboard, the base pad is transparent which allows backlight passing, the graphics can be transparent or other color, if the graphics is white and the keyboard surface is black, painting the white color first, then paint black color. For those buttons are near each other, the spray painting maybe not so even, appear the painting problem as the below picture marks. This problem is difficult to control, which can be improved by spray painting several times. But don’t worry, generally this phenomenon cannot lead to light bleeding.
3. Laser etching process. Advantages: the graphics lifespan of laser etched is longer than silkscreen printing; the graphics/icons border is more uniform than silkscreen printing. Restriction: if the area is very narrow, laser etching cannot achieve perfectly, as below picture marks, it’s difficult to laser out the edge of the narrow area.
4. Painting surface protective coating. Generally PU coating is commonly used for laser etched keyboard, which anti-abrasion lifespan is long.
What need to pay attention to when spray painting PU coating?
Let’s see a case: if the keyboard surface didn’t be cleaned before painting coating, the keyboard surface will be dirty; in addition, different processing way influences the painting effect. As the below right picture marks, the PU coating is white and cracking, then we change the processing way – before spray PU coating, using electric discharge treatment to prevent problem of coating cracking.
5. Uniform conductive base shape. There are conductive rubber carbon pill / ring or and conductive ink printing. In order to improve production efficiency and reduce production cost, it’s better to keep same conductive.
Painted laser engraving keyboard without button webbing design and conductive requirement:
Hardness is very important for painted laser etching keyboard.
If the conductive way is tact switch, aim for getting good tactile feeling of rigid and click, the hardness can be 60-80 Shore A.
But for those keyboard which is pad shape, the hardness cannot be higher than 70 Shore A, otherwise when demoulding, the pad will be brittle and easily broken.