Introduction to Thin-Film Keyboards

　　 Thin-film keypad It is a PET sheet with contact points (including metal shrapnel, also known as domes), used as switches on circuit boards such as PCBs and FPCs, enabling the interaction between users and devices. This component plays a crucial role in providing tactile switching functionality. Compared to traditional silicone keypads, film-based keypads offer superior手感 (hand feel), longer lifespan, and can indirectly enhance the production efficiency of various types of switches that utilize conductive films. The contact points on the film keypad are positioned directly above the conductive areas of the PCB (typically located above the gold fingers on the circuit board). When the button is pressed by external force, the central point of the contact deforms into a concave shape, making physical contact with the circuitry on the PCB and completing an electrical circuit. As a result, current flows through the system, allowing the product to function properly.

　　I. Introduction to Thin-Film Keyboards

　　Thin-film keys feature a basic "key + film" structure, so the tactile feel and performance of the key largely depend on the design of the thin-film key. To ensure reliable separation and rebound of the switch contacts, a film thickness of 0.125–0.2 mm is typically chosen. If the film is too thick, it may lead to slower response times and increased actuation force. For larger key bodies—such as square keys with diagonal lengths exceeding 12 mm or circular keys with diameters greater than 12 mm—it is recommended to use films with a thickness of either 0.15 mm or 0.2 mm. Slightly thicker films provide stronger rebound force. After repeated key presses, the film exhibits minimal relaxation tendencies, ensuring consistent contact functionality over time. When the isolation layer is relatively thin, the circuit board film should be correspondingly thicker; otherwise, excessively thin films are prone to unintended contact bridging. For flat keys, slightly thicker film materials can be employed. However, for films used in circuits prone to contact bubbling, a standard thickness of 0.125 mm is generally sufficient—unless the bubble diameter is large and the chord height at the bubble's apex is particularly low, in which case a thicker film is advised. Thin-film keys are an essential structural component in electronic key products. They serve as the conductive film embedded within both metal spring sheet-based key products and conductive adhesive key products. The primary function of the thin-film key is to act as a switching element, enabling electrical conduction within the key product and connecting to the conductive foil on the circuit board. Structurally, the thin-film key is remarkably simple: after removing the contact cover and keycap, one can directly observe the underlying film circuit and its connection to the circuit board.

　　The working principle of membrane switches

　　II. Thin-film keypad How it works

　　Thin-film buttons are more distinctive. Unlike traditional silicone keypads, they operate on a different principle. These buttons consist of a conductive film coated with metal dots, which are electrically connected. When the button is pressed downward, the conductive adhesive or metal spring beneath it aligns perfectly with the corresponding metal dot, completing the circuit and activating the device. This mechanism enables thin-film buttons to send various command signals.

　　III. Characteristics of Thin-Film Keyboards

　　 Thin-film keypad Its service life is approximately over 1 million cycles, significantly higher than the average lifespan of 200,000 cycles for conventional silicone buttons. This is primarily because membrane switches rely mainly on circuit contact operation, and their longevity is closely tied to the condition of these circuit contacts. Typically, applying a protective layer—such as carbon-based material—onto the circuit contacts can enhance wear resistance without compromising conductivity, thereby extending the overall service life of the switch.

　　The contact resistance of film buttons is a critical factor affecting operational stability. Contact resistance refers to the electrical resistance value between the circuit of the film button switch and the subsequent circuitry. With advancements in technology, film buttons now utilize flexible circuits instead of traditional silver paste for their circuitry, significantly enhancing the stability of these switches.

　　 Thin-film keypad It occupies the majority of the market due to its low cost, simple manufacturing process, and excellent tactile feel. Most keyboards used in everyday life are essentially membrane switches. These switches are also known as thin keys or soft keys, offering superior protection performance. Moreover, the production cost of membrane switches is comparable to that of traditional silicone keypads.