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I am currently designing a product that needs to be waterproof (IP67.) The product also requires some user interaction - basically at least one push-button and one LED.

For the LED I am using these IP68 light guides.

There seems to be no easy solution for the push buttons. I would like to avoid using push buttons that have to be screwed into the front panel, like these because they would increase product cost significantly as they are expensive and complicate the assembly process a lot (because they need to be soldered after they are screwed in.)

I think the optimal solution would be one with a flexible membrane in the middle and a plastic outer ring that provides a similar snap mechanism as the light guides do so I can mount the switch on the PCB and only need to mount the seal to the case.

What are the best practices to cost-effectively add buttons to IP67 designs?

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Brief comments. More can be added depending on other answers. Of these the membrane with included tactile domes is relatively cheap and can give reasonable results. Light can be fed from the rear as desired and a top layer screen print allows reasonable cosmetics.

  • Multilayer membrane keyboards are easily IP6X compatible but usually offer poor tactile response without added tactile units.(I had a requirement for a super-low-touch-pressure keyboard where mechanical tactile feedback was not essential (this machine talks) and a 3 layer keyboard with a grid of conductive stripes on the 2 outer layers plus spacer "dots" and a 3rd layer with holes at key locations produced excellent results.

  • Snapover / click domes added to membrane keyboards offer a reasonable sense of feel but may lack the switch action may not give the quality impression of a top keyboard.

  • I have seen excellent results achieved using "tact" switches panel mounted behind a membrane front sheet. I believe that switch & membrane travel is critical and that for best results the ability to change switch "height" slightly is useful. The creators of this arrangement may (or may not) to provide advice on what is involved to do this well).

I have achieved IP69K+ using a reed switch plus a magnet in an injection moulded slider outside the housing, but this is unlikely to meet low cost objectives in most cases. (It did in mine but volumes were high*).
IP69K information here - high pressure multidirection hot water cleaning - usually for vehicle cleaning use.


After comment from Andrew Morten re IP69K (steam cleaning) being the max IP rating I changed my hyperbolic IP99 to IP69K+. I said:

"My switches would have a fair chance of standing up against the gates of hell, as long as it was below ABS transition temperature :-) (or magnet curie temperature).
Steam cleaning? - no problemo (for sensible steam application periods).
Magnet on outside and reed switch inside of an ABS case. The magnet retainer plate is ultrasonic welded in place. As a bonus the reed can move very slightly under vast impact. As a consequence the reed survivability exceeds the apparent G rating of the bare reed. I'd expected them to fail under stupid impacts but none ever did. eg 15 feet dropped onto concrete or kicked down a flight of concrete stairs :-)

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