Flexible Circuit with Dome Switch

Understanding the Flexible Circuit Dome Switch

From an flexible circuit manufacturer’s point of view, a flexible circuit dome switch is not just another input component—it’s one of the most precise interface structures we build. In simple terms, it is a tactile switch formed by combining a flexible circuit with a metal dome. When pressed, the dome deforms and closes the circuit on the flexible substrate, providing both an electrical signal and a “click” feeling for the user.

Unlike rigid PCB switches, the flexible version can bend, follow curved housings, and maintain reliability even in thin and lightweight designs. That’s why many engineers choose this solution for compact electronics where both functionality and user experience matter.

Structure and Typical Dimensions

When we design and manufacture a flexible circuit dome switch, we always look at the details—thickness, dome size, and actuation force. A typical structure includes: 

Flexible Circuit Layer – Most often made from polyimide film, with thickness ranging from 0.05 mm to 0.2 mm. This layer carries the copper traces and contact pads. 

Metal Dome – Usually stainless steel, with diameters from 3 mm to 12 mm depending on space and tactile requirements. Actuation forces are commonly 160 g, 250 g, or 350 g. 

Adhesive Spacer – Around 0.05–0.15 mm thick, used to hold the dome in position and create a cavity for movement. 

Overlay Layer – A graphic film or coverlay, thickness 0.1–0.2 mm, which also protects the dome and circuit. In total, a finished flexible circuit dome switch assembly can be as thin as 0.3 mm while still delivering hundreds of thousands of reliable clicks.

Why Flexible Circuit Dome Switches Perform So Well

Space Efficiency – Since the flexible substrate is ultra-thin, we can integrate multiple switches into very tight layouts. 

Strong Tactile Response – Metal domes provide sharp feedback, and we can fine-tune the force by selecting different dome sizes. 

Custom Shapes – Because the circuit is flexible, we can match irregular product designs, whether straight, curved, or folded. 

Durability – With proper plating on the contact pads, these switches last well beyond 500,000 cycles. 

Lightweight Construction – A complete flexible circuit dome switch weighs almost nothing compared to mechanical switch assemblies.

Designers use PSA to attach the flexible circuit to the panel behind the dome switch area. For assembly-free flex designs, Flex Plus applies 3M 467 PSA.

Manufacturing Considerations 

Producing a flexible circuit dome switch is not just about printing copper traces and sticking domes. There are technical checkpoints we always pay attention to: 

Dome Placement Accuracy: Our pick-and-place machines align domes with ±0.1 mm tolerance, ensuring perfect contact.

Adhesive Reliability: The adhesive film must survive repeated compression without shifting; otherwise, domes lose accuracy. 

Surface Treatment: For medical or automotive applications, we often recommend ENIG on pads to reduce oxidation. 

Stiffener Use: In some layouts, we add FR4 or polyimide stiffeners behind the dome area to prevent flexing during actuation. 

Testing: Every batch is tested for actuation force, resistance, and cycle life. Customers often request 100% dome response testing to avoid early failures. 

Design Advice for Engineers

Over the years, we’ve seen many designs succeed—and some fail—because of small details. Here’s what we suggest when you design with a flexible circuit dome switch: 

Select the Right Dome Size

Small domes (3–5 mm) save space but give lighter tactile feel; larger domes (8–12 mm) provide stronger feedback. 

Balance Travel and Force

A dome with 250 g actuation and 0.25 mm travel feels different from a 350 g dome with 0.4 mm travel. Both must match the product’s user experience. 

Keep Pad Design Simple

Round or cross-shaped contacts with gold plating reduce wear and ensure clean closure. 

Don’t Forget Assembly Tolerance

Plan for ±0.2 mm tolerance in housing design so the dome sits correctly after final product assembly. 

Ask About Prototyping

We always recommend testing 2–3 versions of domes before locking the final design. 

In most cases, dome switches come with a thin layer of pressure-sensitive adhesive (PSA) on top. During production, they can be directly placed onto the corresponding positions on the flex PCB and secured simply by applying pressure. Additionally, pressing the dome switch generates a small amount of gas. To address this, for simple circuit boards, micro-holes can be designed at the FPC pads to allow gas to escape. Alternatively, a small area at the edge of the dome switch PSA can be left without adhesive, creating a space for the gas to vent.

Conclusion

From our position as an flexible PCB manufacturer, the flexible circuit dome switch is one of the most practical and versatile solutions for tactile input. With careful control over film thickness, dome dimensions, adhesives, and plating, we deliver switches that are not only thin and flexible but also durable and satisfying to use.

If you are designing a device that needs reliable tactile feedback in a limited space, a flexible circuit dome switch is a proven solution. By working closely with your manufacturing partner, you can achieve the exact balance of size, feel, and durability that your application requires.