A customer in Shenzhen came to us last year with a keypad that felt mushy. They had specified a 12 mm round metal dome with a 250g actuation force, and the numbers on the drawing looked fine. But when they assembled it under a 1.5 mm silicone overlay, the keys felt dead. The problem was not the dome force. It was the dome height: they had ordered a 0.25 mm tall dome, but the overlay stack needed a 0.35 mm tall dome to pre-load correctly. Once we swapped the height, the click came back.
Dome height is one of the most overlooked parameters in keypad design. Engineers usually pick diameter and actuation force first, and treat height as a fixed spec. But height determines how much travel the dome provides, how much pre-load the overlay applies, and whether the key feels crisp or mushy.
Measuring dome height against the PCB pad before overlay assembly.
What dome height actually controls
The height of a snap dome is the distance from the PCB pad to the crown of the dome at rest. It is not the same as travel. Travel is how far the crown moves before the dome snaps through, which is typically 60 to 70 percent of the height. So a 0.35 mm tall dome gives about 0.22 to 0.25 mm of travel.
Height controls three things:
Overlay pre-load. The silicone or PET overlay sits on top of the dome crown. If the dome is too tall, the overlay is permanently pressed down, which pre-activates the dome and kills the click. If the dome is too short, there is a gap between overlay and dome, and the key feels loose or rattles.
Total travel. Taller domes give more travel, which feels more premium. Shorter domes feel tight and precise, which is better for compact devices.
Actuation force consistency. The same diameter and force dome can feel different depending on height, because the leverage ratio changes with the dome profile.
Standard dome heights we offer
| Dome diameter | Typical height | Best for |
|---|---|---|
| 3 mm | 0.15 - 0.20 mm | Ultra-thin wearables, hearables |
| 4 mm | 0.20 - 0.25 mm | TWS charging cases, compact remote controls |
| 5 mm | 0.25 - 0.30 mm | TV remotes, small appliance panels |
| 6 mm | 0.30 - 0.35 mm | Industrial HMI, medical devices |
| 8 mm | 0.35 - 0.45 mm | Automotive steering wheel modules |
| 12 mm | 0.45 - 0.60 mm | Heavy-duty industrial keypads |
Four-legged domes in different heights - the leg geometry is matched to the dome profile.
How to calculate the right height for your overlay
The rule of thumb is simple: the dome crown should sit 0.05 to 0.10 mm above the overlay at rest, so the overlay lightly touches the dome without pre-loading it. Measure your overlay stack-up thickness, then work backwards.
For example, if your overlay is 1.0 mm silicone, the dome crown should be about 0.95 to 1.00 mm above the PCB surface. But the dome itself only contributes 0.25 to 0.35 mm of that. The rest comes from the PET carrier thickness and the spacer layer between the dome and the PCB.
If you are using a dome sheet array on an FPC, the FPC polyimide thickness adds another 0.1 to 0.2 mm. Account for that before you pick the dome height.
Common mistakes we see
Using a tall dome under a thin overlay. A 0.45 mm dome under a 0.5 mm PET overlay pre-loads the dome so hard that it snaps on its own. The customer thinks the dome is defective, but the overlay is just too thin for the height.
Using a short dome under a thick silicone overlay. The gap between overlay and dome means the user has to press down twice: once to close the gap, once to snap the dome. The key feels mushy and vague.
Ignoring spacer thickness. The spacer layer between the dome and the PCB sets the overall stand-off. If the spacer is 0.5 mm and the dome is 0.35 mm, the total crown height is 0.85 mm. Do not forget to add the spacer.
What to specify on your drawing
When you send us a drawing for consumer electronics domes, automotive domes, or custom die-cut dome modules, specify:
- Dome diameter (mm)
- Actuation force (g, tolerance +/- 10g)
- Dome height (mm, measured from PCB pad to crown)
- Overlay material and thickness
- Total travel required (mm)
If you are unsure, send us your overlay stack-up and we will recommend the right height. We also send free samples so you can feel the difference before committing to a production run. Contact Shanyo engineering to request a height sample kit for your next keypad project.
- John Smith, Senior Application Engineer, Shanyo
A customer in Shenzhen came to us last year with a keypad that felt mushy. They had specified a 12 mm round metal dome with a 250g actuation force, and the numbers on the drawing looked fine. But when they assembled it under a 1.5 mm silicone overlay, the keys felt dead. The problem was not the dome force. It was the dome height: they had ordered a 0.25 mm tall dome, but the overlay stack needed a 0.35 mm tall dome to pre-load correctly. Once we swapped the height, the click came back.
Dome height is one of the most overlooked parameters in keypad design. Engineers usually pick diameter and actuation force first, and treat height as a fixed spec. But height determines how much travel the dome provides, how much pre-load the overlay applies, and whether the key feels crisp or mushy.
Measuring dome height against the PCB pad before overlay assembly.
What dome height actually controls
The height of a snap dome is the distance from the PCB pad to the crown of the dome at rest. It is not the same as travel. Travel is how far the crown moves before the dome snaps through, which is typically 60 to 70 percent of the height. So a 0.35 mm tall dome gives about 0.22 to 0.25 mm of travel.
Height controls three things:
Overlay pre-load. The silicone or PET overlay sits on top of the dome crown. If the dome is too tall, the overlay is permanently pressed down, which pre-activates the dome and kills the click. If the dome is too short, there is a gap between overlay and dome, and the key feels loose or rattles.
Total travel. Taller domes give more travel, which feels more premium. Shorter domes feel tight and precise, which is better for compact devices.
Actuation force consistency. The same diameter and force dome can feel different depending on height, because the leverage ratio changes with the dome profile.
Standard dome heights we offer
| Dome diameter | Typical height | Best for |
|---|---|---|
| 3 mm | 0.15 - 0.20 mm | Ultra-thin wearables, hearables |
| 4 mm | 0.20 - 0.25 mm | TWS charging cases, compact remote controls |
| 5 mm | 0.25 - 0.30 mm | TV remotes, small appliance panels |
| 6 mm | 0.30 - 0.35 mm | Industrial HMI, medical devices |
| 8 mm | 0.35 - 0.45 mm | Automotive steering wheel modules |
| 12 mm | 0.45 - 0.60 mm | Heavy-duty industrial keypads |
Four-legged domes in different heights - the leg geometry is matched to the dome profile.
How to calculate the right height for your overlay
The rule of thumb is simple: the dome crown should sit 0.05 to 0.10 mm above the overlay at rest, so the overlay lightly touches the dome without pre-loading it. Measure your overlay stack-up thickness, then work backwards.
For example, if your overlay is 1.0 mm silicone, the dome crown should be about 0.95 to 1.00 mm above the PCB surface. But the dome itself only contributes 0.25 to 0.35 mm of that. The rest comes from the PET carrier thickness and the spacer layer between the dome and the PCB.
If you are using a dome sheet array on an FPC, the FPC polyimide thickness adds another 0.1 to 0.2 mm. Account for that before you pick the dome height.
Common mistakes we see
Using a tall dome under a thin overlay. A 0.45 mm dome under a 0.5 mm PET overlay pre-loads the dome so hard that it snaps on its own. The customer thinks the dome is defective, but the overlay is just too thin for the height.
Using a short dome under a thick silicone overlay. The gap between overlay and dome means the user has to press down twice: once to close the gap, once to snap the dome. The key feels mushy and vague.
Ignoring spacer thickness. The spacer layer between the dome and the PCB sets the overall stand-off. If the spacer is 0.5 mm and the dome is 0.35 mm, the total crown height is 0.85 mm. Do not forget to add the spacer.
What to specify on your drawing
When you send us a drawing for consumer electronics domes, automotive domes, or custom die-cut dome modules, specify:
- Dome diameter (mm)
- Actuation force (g, tolerance +/- 10g)
- Dome height (mm, measured from PCB pad to crown)
- Overlay material and thickness
- Total travel required (mm)
If you are unsure, send us your overlay stack-up and we will recommend the right height. We also send free samples so you can feel the difference before committing to a production run. Contact Shanyo engineering to request a height sample kit for your next keypad project.
- John Smith, Senior Application Engineer, Shanyo
