Translucent section in moulded plastic panel

Hi all,

A product I am designing will have status indicator light on one of the panels, indicating on/off etc.
This will be achieved using a small PCB with LEDs mounted on the underside of the panel.

However, I am wondering if anyone has any experience of how a semi-transparent section could be achieved in the panel which would allow the light to be viewed? I don’t want an open hole in the panel, as it needs to resist water ingress.

The type of finish I’m talking about is commonly seem on PC power buttons (see attached) as well on laptop charger cable (Apple Magsafe),

I know one option would be to mould the panel with a hole, and then fill it with silicone or some other resin after moulding. However this seems like a messy solution.

Anyone have any idea how this effect is usually achieved?

Many thanks in advance.

Here are some approaches:

Close fit of two parts to appear seamless.
Dual injection of two plastics, seamless.
Printed film that is pressure formed and then injected behind with a thermoplastic. Cell phone keypads.
A thinner section of plastic from the backside to create translucency.
Laser piercing, as Apple does with aluminum case power lights.

The most seamless light on tech I currently have is on my Razer Taipan mouse.

That’s great. Thanks for your suggestions nxakt.
Another related question - do you have any suggestions for a type of plastic that is good for diffusing LED light?
Thanks again.

Regarding diffusing lighting, the best bet is to take apart a few computer mice and see what they use for the light pipes inside. I would imagine most transparent plastic will be the same for the task, polished internal surfaces reflecting light from the source to the outside and some kind of coating or finish to allow the light to exit.

That button you originally posted looks like it was most likely a translucent base plastic with a black paint applied, then the power icon was created by laser etching the paint to reveal the translucent plastic below.

Sabic makes the Lexan FX series of Polycarbonate which has a range of material added to add light diffusing properties. You get a plastic that is milkier and slightly less transparent but diffuses light better.

Generally, just adding texture to the outside surface will help diffuse the light enough, but there are lots of ways to go about good optical properties that will depend on your design - you’ll want to avoid hot spots.

I bought one of those Razer mouses to yank apart once, IIRC those are done using a combination of paint and masking off the graphic area. The entire part is shot in clear with soft touch paint on top.

Cool, when I look closely at the Razer it is possible to make out the etch raster through the soft touch paint cut by the laser. That has been a mystery, thanks for the one-two puzzle solve guys.

Laser etching is also the most common way of doing keypads now for laptops and things like that that are backlit.

Thanks for all your responses guys. Very informative and helpful.