When flexible circuit boards become the "skin" of circuits, will future electronic devices still need traditional "motherboards"?
Publish Time: 2025-09-02
With today's rapid trend toward lighter, thinner, smaller, and more intelligent electronic products, device weight has become a crucial indicator of portability, user experience, and advanced design. From smartphones, smartwatches, TWS earbuds, drones, and medical wearables, manufacturers are relentlessly striving to shave every gram off the weight. In this process, traditional rigid printed circuit boards (PCBs) are increasingly unable to meet the demand for extreme lightweighting due to their thickness, weight, and wiring limitations. Flexible printed circuit boards (FPCs), with their unique material structure and design flexibility, are becoming a core technology driving weight reduction and upgrades in electronic devices.1. Material Innovation: A Weight Revolution from "Rigid" to "Flexible"The core of flexible circuit boards lies in their substrate—typically using an ultra-thin polyimide (PI) or polyester (PET) film as the insulating layer. The thickness can be as low as 12.5μm, far less than the 0.4mm to 1.6mm of traditional FR-4 rigid boards. This polymer film not only offers excellent high-temperature and chemical resistance, as well as electrical insulation properties, but more importantly, it boasts low density and light weight. For example, a typical two-layer FPC weighs only 10% to 30% of a rigid board with the same functionality. This weight advantage is significantly amplified in applications involving multi-layer stacking or large-area wiring, providing significant potential for overall device weight reduction.2. Simplified Structure: Replacing Wiring Harnesses and Reducing Redundant ComponentsIn traditional electronic devices, different modules are often connected via multiple wires or cables. These harnesses not only take up space but also require additional connectors, mounting brackets, and insulation materials, adding to the overall weight and complexity. Flexible circuit boards, on the other hand, integrate multiple connection paths onto a single ultra-thin film, achieving "all-in-one wiring" and directly replacing traditional wiring harnesses. For example, in a smartphone, an FPC can simultaneously connect the camera, fingerprint module, display, and motherboard, eliminating multiple independent cables and connectors, significantly reducing the number of components and overall weight. Furthermore, the foldable and curly nature of the FPC allows routing along the device's internal contours, eliminating redundant wiring and bundling materials, further contributing to lightweighting.3. Three-Dimensional Routing: Freeing Up Space and Optimizing Structural DesignOne of the greatest advantages of flexible circuit boards is their three-dimensional adaptability, allowing them to bend and twist. They are no longer limited to flat mounting. Instead, they can route circuits along curved, folded, or three-dimensional paths within a device, fully utilizing spaces inaccessible to traditional rigid boards. This "three-dimensional routing" capability enables more compact device designs, eliminating the need for large, flat areas for circuit boards, thereby reducing the size and overall weight of the enclosure. For example, in a smartwatch, an FPC can be arranged in a circular pattern around the inner wall of the case, efficiently connecting the battery, sensors, and main control chip. This significantly improves space utilization and achieves the goal of an extremely thin and lightweight design.4. High Integration: Reducing Assembly Layers and Improving Lightweight EfficiencyModern FPCs support multi-layer routing, blind and buried vias, microvias, and high-density interconnect (HDI) technologies, enabling complex circuit functions to be implemented within a very small area. This high level of integration not only reduces the number of circuit boards required but also reduces the reliance on multi-layer structures and support frames. Furthermore, FPCs can be directly bonded to the surface of batteries, displays, or structural components, eliminating the need for additional mounting brackets or screws. This reduces the use of non-functional components and further reduces the "dead weight" of devices.5. Application Examples: From Consumer Electronics to AerospaceIn TWS earbuds, FPCs integrate a miniature microphone, battery, and Bluetooth chip into a millimeter-scale footprint, keeping the overall weight under a few grams. In foldable phones, FPCs serve as a "dynamic bridge" between the display and motherboard, maintaining signal flow during repeated bending while eliminating the burden of heavy wiring harnesses on the hinge structure. In drones and spacecraft, FPCs' lightweight nature directly impacts battery life and launch costs, making them the preferred interconnect solution for high-end equipment.Flexible circuit boards, through lightweight materials, structural integration, 3D wiring, and high-density design, have radically changed the boundaries between weight and form of traditional circuits. They are not only a carrier for electronic interconnects but also a key enabler for achieving extreme lightweighting in devices. In future electronic products striving for "light as a feather," FPCs will continue to play the role of an "invisible weight reduction engine," making technology lighter and the user experience more flexible.
