Flexible PCBs (Flexible Printed Circuit Boards), also known as flex PCBs, are circuit boards with a thin, bendable substrate—typically made of polyimide, polyester, or liquid crystal polymer (LCP)—designed to conform to tight spaces, fold, or flex during use. Unlike rigid PCBs (which maintain a fixed shape), flex PCBs prioritize flexibility and compactness, making them ideal for devices with irregular form factors or moving parts.

The flexibility of these PCBs stems from their thin, elastic substrates: polyimide, the most common material, is lightweight (thicknesses as low as 25μm), heat-resistant (operating temperatures up to 260°C), and highly durable—able to withstand thousands of bending cycles without damaging conductive traces. Conductive layers are made of thin copper foil (1–3 oz), etched into traces that follow the substrate’s flexibility. For example, a flex PCB in a smartphone connects the display to the main board, bending as the phone is folded (in foldable models) or fitting into the slim gap between the screen and battery.

Flex PCBs are available in single-sided, double-sided, or multi-layer designs, with additional features like stiffeners (small rigid sections to support components like connectors) or coverlays (protective films to shield traces from moisture and abrasion). Key advantages include space efficiency (they can bend around corners or fold, reducing the overall size of electronic assemblies), weight reduction (up to 70% lighter than rigid PCBs with the same functionality), and reliability in moving parts (no loose wires that can break, making them ideal for devices like cameras with zoom lenses or wearable tech).

Common applications include wearable devices (e.g., smartwatch straps, where flex PCBs curve around the wrist), automotive components (e.g., door wiring harnesses, replacing bulky cables), medical devices (e.g., endoscopic cameras, where the PCB bends to navigate the body), and consumer electronics (e.g., foldable phones, laptops, or wireless earbuds). While flex PCBs are more expensive than rigid alternatives, their ability to fit into tight, complex spaces makes them indispensable for modern, miniaturized devices. For manufacturers designing compact or movable electronics, flex PCBs offer unmatched flexibility and integration capabilities.