What Is a Metal Dome Array, How Does It Work, and Why Do Global Hardware Engineers Rely on Custom Tactile Sheets for Superior Switch Reliability?

A single-layer metal dome array consists of a clear polyester (Mylar) carrier sheet coated with pressure-sensitive adhesive on its underside, adhering both the perimeter of the metal dome and securing the sheet to the PCB. In contrast, a double-layer dome array incorporates an intermediate spacer layer (often 0.05mm - 0.10mm PET) sandwiched between the top retaining film and the PCB adhesive layer. The spacer layer contains die-cut circular or cross cavities that house each dome. This completely isolates the adhesive from the contact area, preventing glue bleed or adhesive migration onto the PCB gold pads over repeated cycles, while providing enhanced venting paths and superior dust resistance (up to IP67).

When an operator presses a metal dome, the dome snaps downward, displacing the column of air trapped beneath its internal cavity. If the array is hermetically sealed against a rigid PCB without vent channels, this air compresses, dampening the tactile sensation, increasing the required actuation force, and producing a spongy, indistinct feel. Worse, when the key is released, vacuum suction can delay the dome recovery time or cause key stick. Cevra designs engineered micro-vent channels—either cut into the spacer adhesive layer or etched into the PCB solder mask—connecting adjoining dome cavities to equalize atmospheric pressure seamlessly during rapid typing.

The tactile click ratio (expressed as a percentage) defines the crispness of the physical snap perceived by the user. It is mathematically calculated as: Click Ratio (%) = [(Actuation Force - Contact Force) / Actuation Force] × 100. For example, a dome requiring 300g to trip that snaps down to a bottoming contact force of 150g delivers a click ratio of 50%. A click ratio between 45% and 65% is generally considered optimal for consumer and medical keypads, giving unambiguous sensory confirmation without causing finger fatigue. At Dongguan Cevra Electronic Technology Co., Ltd., every production batch is verified using computerized fragment load testers to ensure strict adherence to this force-displacement curve.

All our metal domes are stamped from high-grade SUS301 full-hard stainless steel, offering natural corrosion resistance. Nickel plating (1.0µm - 2.0µm Ni) is the industry standard for general industrial, appliance, and consumer keypads, offering contact resistance below 1.0 Ω and guarding against minor atmospheric tarnishing. Gold plating (0.5µm - 1.5µm Au over a nickel underplate) is recommended for low-current, low-voltage battery-operated devices (such as handheld IoT trackers, military radios, or medical wearables) where contact resistance must remain consistently under 0.1 Ω and operate without fretting corrosion over millions of cycles.

For a standard 4-leg cross dome (e.g., 8.4mm or 10mm), the PCB layout should consist of a central round contact pad surrounded by four outer contact pads or an outer conductive ring. The central pad diameter should measure approximately 1.5mm to 2.5mm, depending on dome size. Solder mask must never overlap onto the contact pads. Furthermore, we strongly advise an ENIG (Electroless Nickel Immersion Gold) or Hard Gold surface finish on the PCB pads rather than HASL (lead-free solder leveling), as solder leveling creates uneven surface topography that causes dome rocking, erratic contact resistance, and premature metal fatigue.

To initiate a custom metal dome array project with Dongguan Cevra Electronic Technology Co., Ltd., please provide: (1) CAD vector drawings in DXF, DWG, PDF, or Gerber format detailing the dome coordinates, outer array contour, alignment holes, and venting routes; (2) Desired dome geometry (4-leg, round, triangular, or oblong), diameter, and trip force (e.g., 180g, 250g, 350g, 500g); (3) Plating specification (bare stainless steel, nickel-plated, or gold-plated); and (4) Operating temperature and environmental sealing requirements. Our engineering team returns a full DFM check and layer stack-up proposal within 24 hours.