Metal Domes for Membrane Switches

Last updated: 2026-07-28

Selected Engineering Reference

Use the F07280 record below when an OEM drawing leaves the dome open. Naming the source model keeps its component limits separate from the finished membrane-switch specification.

The values above come from the Snaptron F-Series product record. Every line remains scoped to that traceable reference component.

Integration values used with the reference

INOVAN publishes the material, tactile and resistance references in its snap-dome technical brochure. The released project drawing sets the final dome, pad, actuator, tolerance, finish and completed-switch life target.

Published 7 mm Force Comparisons

The F-Series catalog provides lower and higher forces at the same 7 mm diameter. Comparing one diameter first reduces the number of geometry variables during sample evaluation.

These values are published on the Snaptron F-Series page. Select the lowest force that prevents unintended operation while meeting the installed tactile target. Make the final comparison through the real overlay, spacer, circuit and enclosure support.

For automated solder placement, Snaptron’s S-Series white paper lists solderable four-leg domes from 6.3 to 14 mm, 280 to 550 gf, nickel plating and a 1,000,000-cycle component rating.

How a Metal Dome Produces Tactile Feedback

A metal dome begins in a stable convex shape. A centered actuator increases load until the dome reaches its peak force. The dome then snaps through, its center contacts the circuit pad, and the spring geometry recovers when the load is removed.

Use one force vocabulary throughout a test report. INOVAN defines maximum actuation force as F, return/contact force as FR, and the force drop as ΔF = F − FR. Its snap formula is:

Snap ratio = (F − FR) ÷ F × 100%

INOVAN publishes a typical ΔF target of 0.3–0.5 × F. This guide selects 45% as the upper-middle comparison value. Snaptron’s procedure uses Fmax, Fmin, Fc and Fb for a different force-curve notation, so the report keeps INOVAN’s FR and Snaptron’s Fmin as separate definitions.

Travel is the displacement from the relaxed dome to electrical contact. Snaptron lists 0.38 mm as the reference travel for F07280. Its dome-handling guidance states that most domes are depressed to the flat plane and no farther; set production stroke from the selected dome drawing.

Snaptron’s loose-dome procedure defines Fmax, Fmin, Fc, Fb and their corresponding travel points. ASTM F2592-16 covered membrane-switch force-displacement measurement but was withdrawn in 2023 without replacement. ASTM F1578-24 remains active for contact-closure cycling.

Metal Dome Shapes and Supply Formats

Four-leg, round, triangle, oblong, and SMT domes solve different packaging and force problems. The shape changes how the dome is supported, how closely keys can be spaced, and how force is transferred to the circuit.

Use a four-leg dome for the selected 7 mm / 280 gf comparison. An adhesive PET array fixes pitch and orientation for multi-key layouts. Loose domes support prototype comparison or a separate mechanical retainer. Choose SMT domes when the assembly process requires automated placement and reflow.

Snaptron’s DT-Series data documents center-hole backlighting, two electrical contact levels, loose packaging and adhesive arrays.

Actuator, Support, Spacer and Vent Rules

Actuator geometry and support change the measured installed response. Apply these four rules to the 7 mm reference design:

1. Use a flat-bottom, centered production actuator no larger than 1.75 mm in diameter.
2. Use a 1.27 mm flat probe and ±0.254 mm centering for loose-dome force testing.
3. Test the loose dome on a hard, flat, vented fixture.
4. Set production stroke from the selected dome drawing and vent every closed pocket.

Snaptron’s force-test procedure specifies the 1.27 mm probe and ±0.254 mm test centering. Its separate actuator guidance limits a flat, centered production actuator to 25% of dome diameter; for 7 mm, the maximum is 1.75 mm.

The spacer pocket locates the dome and gives it clearance to move. Snaptron lists a 6.35 mm X cavity dimension for F07280; use the selected part drawing for the final cavity and contact pad, and keep adhesive outside the moving surface.

Provide a vent path unless the carrier or circuit already vents the pocket. A spacer channel can connect adjacent pockets, a PET array can vent through the carrier, or a PCB/FPC can use a vent via. Snaptron’s venting guidance states that trapped air causes a significant loss of tactile response.

PET, FPC and PCB Integration

Metal domes work with printed PET circuits, copper FPCs, and rigid PCBs when the pad, support, retention, and vent path are designed as one interface.

For rigid or flex copper pads, choose the finish by cycle target. Snaptron’s plating guide recommends 5.0–12.5 µm of bright hard nickel or 0.76–1.27 µm of hard gold when the target exceeds one million cycles. ENIG is listed for lower-cycle applications. These thicknesses apply to the circuit contact surface; specify the dome finish separately.

Use nickel as the selected comparison finish. INOVAN publishes assembly-dependent standard values of <1 Ω for nickel and <100 mΩ for gold. Select the dome and pad finishes together from the contact-resistance and cycle requirements.

The contact pad should come from the selected dome series rather than a generic copied footprint. Provide the circuit artwork, dome center coordinates, keep-out zones, tail or connector route, and local support thickness in the released drawing.

Electrical, Environmental and Life Limits

The F07280 record specifies 0.1–50 VDC, 0.05–100 mA DC and 1 W maximum, positioning it as a signal contact. Set firmware or hardware debounce from the published <0.3 ms make and <0.6 ms break values, then verify the installed stack.

Use −40°C to +85°C as this guide’s design window. It matches INOVAN’s published general operating range and stays inside the −45°C to +100°C F07280 rating. Qualify the complete switch across the project temperature range because the overlay, adhesive, circuit, enclosure and dome form one stack.

F07280 is published at up to 5,000,000 component actuations. Define the completed-switch cycle count in the project specification and test the assembled key to that number. ASTM F1578-24 supplies the cycling method; the project specification supplies the pass count.

Verification Plan for Samples and Production

The release specification needs an exact component record and a repeatable test setup. Use this sequence:

1. Measure the loose dome. Use a calibrated force-displacement gauge, a 1.27 mm flat probe, a hard vented fixture, and 1.27 mm/s test speed.
2. Precondition consistently. Cycle the dome ten times and record the force-displacement curve on the eleventh actuation, following Snaptron’s published test procedure.
3. Measure the assembled key. Repeat the curve through the actual overlay, actuator, spacer, circuit, and enclosure support.
4. Run contact-closure cycling. Use ASTM F1578-24 or the project-defined equivalent; set the cycle count and optional electrical monitoring in the project specification.
5. Release the drawing. Record dome model, geometry, nominal force and tolerance, travel, tactile target, pad finish, actuator, pocket, vent, test method, life target, and change-control triggers.

For the loose F07280 reference, record 280 gf ±30 gf typical trip force and 0.38 mm reference travel. For the completed key, define force, travel, tactile ratio, contact resistance and life limits after measuring the approved overlay, spacer, circuit and enclosure stack.

Incoming and in-process inspection should verify dome orientation, carrier registration, pocket alignment, contamination, adhesive intrusion, vent continuity, pad finish, and visible dome damage. Electrical inspection should confirm closure, open-circuit recovery, resistance, and bounce against the released control plan.

Common Failure Modes and Corrections

Before changing dome force, inspect the actuator, support, vent, pad and retainer.

JASPER Metal Dome Samples

The following JASPER photographs show four-leg and oblong metal-dome forms used during material and geometry review.

The numerical baseline on this page comes from the cited technical records; the photographs document the physical forms shown.

Related Products and Engineering Guides

• Custom metal dome membrane switches for quotation, stack design and production.
• Tactile membrane switches for metal dome, polyester dome and embossed-overlay options.
• PCB and FPC membrane switches for copper circuit and board-backed assemblies.
• Metal dome force selection guide for operator scenarios and force bands.
• Membrane switch design guide for drawings, tolerances and layer-stack inputs.
• Materials Center for overlays, adhesives, circuits, backlighting, silicone, rigid panels and sealing materials.

Send the key layout, circuit artwork, available height, use conditions, force preference, life target and enclosure section to request a dome-stack review. Use the 7 mm / 280 gf reference as the first comparison point.

Frequently Asked Questions

Data Source and Project Release

The published F07280 and INOVAN values above are industry reference data. The released project drawing controls the JASPER production configuration and completed-switch acceptance limits.