Solve Silicone Button Pad Design & Manufacturing Difficulities

As a professional silicone rubber keypad/rubber button pad manufacturer,Xiamen Better Silicone Rubber Co.,ltd always encounter some complex silicone button design.

Recently one of our customer requires a special silicone rubber button pad.Here are his requirements.

We are working on a new project we require assistance with.  Our customer wants to light the right hand key from the edge.  They plan on lighting this key by driving light through the very thin .010” base web rubber into the side of the actuator (see our side view img420 attached with arrow indicating the hypothetical light flow) to light the power key symbol.  We have tried to get our Customer to reconsider and use LEDs located below the key but they will not change.  As you can see it is designed so that the light enters the rubber where it sits beside the side fire green LED (that is why there can’t be any paint on that surface) it then travels into the side of the key actuator stem thru the “ramp” feature.  The light then will illuminate the rubber and light the translucent white key symbol.  The opaque white paint on the rear of the part is there to prevent the light from leaking out of the bottom of the part.

§  Flow molded in opaque red and clear silicone rubber durometer around 50 shore hardness

§  The clear rubber should be the clearest possible rubber available

§  The red should be opaque

§  Mask the face of the flow molded red section

§  Spray the right side (face of part) in the power key area with bright translucent white paint

§  Spray the face of part with opaque black paint

§  Mask the rear of the part in the area of (5) clear LEDs (center of part)

§  Spray the rear of the part with (opaque) white paint specifically in the power key and LED area

§  Laser etch on face of part to expose the translucent white symbol on face of power key and laser etch thru to clear rubber on the (5) discreet LEDs

§  Print text on left hand key

§  Spray the face of part with PU coating

§  Apply epoxy cap dotting process to two (2) keys

§  Die-cut or laser cut thru the rectangular window for the side fire LED.  This will ensure that the there is absolutely zero paint in this cutout as this is where the LED light enters the part

According to description,we know that this silicone rubber button pad design is not easy to produce,this button design integrates all the silicone rubber button pad production processes:

1. High clear silicone rubber pad

2. Spraying white color,spraying black color

3. Double color shot,also called as double colors setting key

4. Laser etching / laser engraved of the power key

5. Silk screen printing of characters

6. Silicone button keycaps

7. PU polyurethane protective coating 

8. Epoxy coat / Epoxy coating protection

From the drawing,we need to confirm one issue first:

If the side of keys are translucent, there are two different ways to achieve:

1.Laser etching process: Silk screen printing first and then laser engrave the symbols. 

2.Hollowing Out Silk Screen Printing. 

After confirmation with customer,they want the sides to be opaque.To process by laser etching to achieve backlight effect.

Silicone Rubber Button Pad Prototype:

In orde to make sure the light will not slip through the cracks,we also do the white painting under the power key.

The most thorny problem is about the overpaint of the LED window. According to customer’s requirements,the light will go through the thin wall of LED window and then illuminate the power keys.So they don’t want the LED window with any paint.

Feedbacks by customer:

To solve this problem, we tried many solutions.

Firstly,we tried silicone button keycaps to mask the LED window. But failed.Beacuse the button keycaps are too thin to mask well when spray color.

Then we tried to use die-cut tool to remove the flash of LED window. But the window is too

small to cut which will overcut the surround area.

Lastly, our engineer suggested making a change on the mould. Change the die-cutting for trimming from bottom to top:

There is no more spray paint on the edge of LED window. 

Rubber Button Pad with too many color spraying layers, PU polyurethane protective coating on the surface ,it becomes too thick to trim the burr/flash.

So we make the die-cutting tool to remove the burr.

Finally, apply 3M adhesive layer to fix the rubber keypad on the PC board.