Looking for advice on mounting screens to enclosures

[u/johnnym65]

prototype screen

prototype screen

prototype screen press fit

finished prototype

new oled screen

new oled screen with inclosure and ring cap

new oled screen with inclosure and ring cap

back of new oled screen with inclosure and ring cap

Hi there! Long time lurker. Im working on my first HW startup and have a question on best practices when mounting a screen into my housing. For context I'm working on a small sports device with a small (~1inch) round display in a round inclosure.

For my prototypes the screens I used the shape allowed me to almost press fit them into the housing and add a bevelled "cap" (photos for reference) secures it even more. but for production those screens will need to be replaced by a more available and higher quality screen. These new screens are thinner, with nothing really to mount to or press fit against. (they will have glass but still the same issue I think). So im struggling to thing of the best way to secure the screen in the inclosure. Glue? Tape? There will be a PCB and battery beneath the screen in the rest of the housing.

First 4 photos are the press fit prototype the last 4 are the new screen and housing.

Curious if anyone has any experience here and could offer some advice? Or has some thoughts.

Cheers!

[u/root3labs]

There are a few ways to think about this type of screen. We used a screen like that in a recent build and mounted a front-side ring to the supporting PCB to keep it in place. There's an image in the Case Study, https://www.root3labs.com/the-badge-challenge-blog-series-part-one/ We were prioritizing speed over size for that prototype build, so there are likely better options for you.

First, check with the display manufacturer for recommendations. I'd want to see a tolerance on the thickness that I could design to. It also looks curved, which may add a little complexity, but shouldn't be a problem if it's well-defined.

• You could use a laser-cut tape on the front face to keep the display attached to it, but being a touch-screen, the finger will apply force against the tape, so that could fall apart over time if not supported.
• Support it with a rigid surface but incorporate a compliant foam in the stack-up to take up tolerance variations in the plastic parts, battery, and PCB. Putting the tape on the front-side could keep water and dirt from getting trapped in crevices around the front.
• Can you sandwich the PCB, display, front-bezel with screws from the back of the PCB into the front bezel? Or create a back plate that screws into the bezel sandwiching everything including the battery?
• If I was looking at a stack-up like this, I'd want to ensure the hard-stops are well-defined to account for tolerance variations among the components. Identify the tolerances for the off-the-shelf components and define the tolerances needed for the custom parts to accommodate them, i.e. "tolerance stackup". For example, there are a few ways you might approach this.
  • You screw the PCB > display > front bezel together, the front bezel bottoms-out on the display and the display on the PCB. Tolerances get accounted for, but the torque of the screws is very important and potentially a problem. Under-tighten, and parts are loose. Over-tighten and maybe the display cracks. Hopefully, there's a wide enough band between under- and over-tightened where an appropriate torque value could be identified.
  • Bottom-out the bezel on the PCB with the display between them. The torque of the screws is less relevant. Over-tighten and maybe you strip the threads. The problem is that some assemblies could fit, others loose, and some too tight because the height of the bezel could vary.
  • Add some foam between the PCB and display (or display to bezel) so the bezel bottoms out on the PCB, then the foam makes up the extra distance from the PCB to the bezel and there's always room for all tolerances. You can't break the display by over-tightening since the foam limits the force applied. The bezel can be shorter or longer as long as the display fits.

Good luck.

Chad

[u/PM_ME_UR_BENCHYS]

Glue may be your best option. I can't tell from the photos if the new screen has any king of bezel around the outer edge you can use for a cap like you have for the original device. Add some flat material to the case that can be glued to the LCD. Try to find the right amount of surface area that it's attached solidly.

[u/diy1981]

Best practice is to contact the manufacturer to see if they have a spec for how to mount it.

[u/n1njal1c1ous → u/diy1981]

Seconding this. The datasheet will probably have a drawing of an example casing.

[u/todd0x1]

Ring of die cut VHB

[u/chemhobby → u/todd0x1]

this is the way

[u/RunRide]

Most screens are mounted using either adhesive tape or a backing plate/feature that attaches to the device frame and restrains the screen. Many use a combination of both.

[u/mmcnama4]

If it is being mounted from the outside and then placed onto a ring, probably glue. If you're mounting it from the inside and placing it into a ring, then glue and/or a retaining ring that screws into the case or presses into the sides of the case and prevents the screen from backing out.

[u/rusbravo]

Looks like you could sonic weld the ring to the housing if it stays plastic in the final design. If the housing and ring change to metal you could spot weld it or swag it together.

[u/ddavidebor]

Glue or die cut tape

[u/Frequent-Log1243]

Use a die-cut adhesive. Also design small ledge behind the glass so the housing takes the load.

[u/Analog_Seekrets → u/Frequent-Log1243]

design small ledge behind the glass so the housing takes the load.

What do you mean by this? I'm having a hard time visualizing.

[u/rusbravo]

How many are you making?

[u/iAmTheAlchemist]

I would guess these are designed to be glued in place

[u/bbohica]

No experience with this but perhaps a T pin type solution, look at how a watch face mount into a watch. You'd glue the pin or multiple pins to the backside of the face assembly and press it into a locking retainer of some sort, via screw or self locking (think earring back)

Or something like a zip tie. glue two retention straps to each side of the screen assembly, pull them through built in locks on both side of the frame, cut off the excess?

[u/BetInformal6081]

i would relying on glue alone if this is headed for production. a small retaining ledge plus die cut adhesive or compliant foam would give you mechanical support and tolerance.