FPC membrane circuit with metal dome

Electrical performance: 

How to choose a suitable FPC flexible circuit board with metal dome?

Different scenarios have vastly different requirements for the 'conduction stability, environmental resistance, and mechanical life' of the circuit board. Therefore, it is necessary to first clarify the core needs to avoid blind selection.

High-frequency operation scenarios: The core concerns are the pressing life of the metal dome (required to be ≥ 1 million times, stainless steel domes are preferred with a rebound rate ≥ 85%) and the conduction response speed (contact delay ≤ 10ms to avoid key 'stuttering'); the FPC substrate should be a material with good bending resistance (such as PI substrate, with a bending resistance of ≥ 50,000 times to prevent circuit breakage caused by long-term pressing).

Low-frequency operation scenarios: The requirement for the dome's life can be appropriately reduced (≥ 500,000 times is acceptable), with a focus on cost control and basic conduction stability (contact resistance ≤ 0.1Ω to avoid signal transmission errors).

Harsh environments: The FPC needs to be strengthened with protective treatments, and the metal domes need anti-oxidation / anti-rust treatments. Nickel-plated or gold-plated domes are preferred to avoid poor contact caused by dome oxidation.

Normal environments: Basic protection is sufficient (FPC with ordinary protective film, nickel-plated domes), with a focus on balancing 'performance and cost'.

Small devices: Pay attention to the thickness and flexibility of the FPC (the substrate thickness is preferably 0.05~0.1mm, the overall thickness ≤ 0.3mm, and the bendable radius ≤ 5mm to avoid circuit damage during assembly); the metal domes should be 'thin models' (thickness 0.1~0.2mm, such as stainless steel domes) to ensure they do not exceed the internal space limit of the device.

Metal dome: Determines the pressing feel and conduction stability. Nickel-plated domes are preferred, with a pressing life of more than 1 million times and a contact resistance of less than 0.1 ohms.

FPC substrate selection: PI substrate is preferred. For low-cost scenarios without bending requirements, PET substrate can be selected.