Related Knowledge About FPCs
Blaze Display Technology Co., Ltd. | Updated: Nov 27, 2018
FPCs: Flexible Printed Circuits
Flexible Printed Circuits (FPCs) are a type of flexible cable that allows circuits to be printed onto a flexible substrate. These flexible printed circuit cables can bend and fold, allowing for complex electronic connections in confined spaces. FPCs perform the same functions as traditional Printed Circuit Boards (PCBs) but on a flexible surface.
Printed atop an FPC is a highly customizable circuit, so each FPC is typically designed to be used for a specific application. Their flexible and lightweight build makes them best for projects that require a more complex connection within a limited space.
Parts of an FPC:
l Pins: Individual conductive contact points at each end of an FPC that connect to corresponding pins on another device.
l Pin out: The arrangement of pins on an FPC. The pin out ensures correct alignment for transferring signals.
l Pitch: The distance between the centers of two adjacent pins. The pitch determines the cable's compatibility with connectors.
l Through-hole: Plated holes that allow electrical connections between different layers of the FPC.
l Electrical traces: Pathways that carry electrical signals across the FPC. FPCs can consist of one layer or multiple layers of conductive traces.
l Electrical components: Various devices mounted onto an FPC, including resistors, capacitors, integrated circuits, and transistors.
l Stiffener: Rigid pieces added to certain areas of the FPC to provide additional support, especially at connection points.
l Substrate: The base material of the FPC, which provides the flexibility and support for the conductive traces.
What FPCs are Made of
FPCs are built starting with a flexible base layer made from polyimide or polyester. Atop this base, one or more layers of conductive traces made from copper are bonded down using an acrylic or epoxy-based adhesive above each layer. Multi-layered FPCs have through-hole vias coated with copper along the inside and ends of the hole to allow the layers to interact.
Throughout the FPC, thin polyimide-based stiffeners or thicker stiffeners made of fiberglass-reinforced epoxy may be used in certain areas to provide varying levels of additional support.
Overtop all, a polyimide coverlay provides an insulating and protective layer. FPCs may also come with a shielding layer made of aluminum or copper foil over parts of the cable to prevent EMI. Tin or gold-plated pins lay at each end of the cable for easy solderability.
How FPCs Work
Similar to an FFC, each end of an FPC has an array of pins that connect to a different device on each side. When connected to a power source, this allows the two devices to communicate with each other by sending electrical signals from one device through the FPC to reach the other device.
Unlike an FFC, the electrical signals travel through the FPC on more complex paths, following the traces etched onto the FPC. Some signals will also travel directly to certain mounted components, rather than passing straight through to reach the device at the other end. In multi-layered FPCs, each layer of traces is separated, so a signal can reach other layers by traveling through the conductive exterior of the through-hole.
Advantages of FPCs:
l High complexity: FPCs are able to support complex circuit designs, including multi-layer and surface-mount components.
l High customization: With the capacity to incorporate countless versions of circuit designs in multiple layers and attach additional components, FPCs can be highly customized to serve specific functions for niche applications.
l High flexibility: The flexible material that acts as the base for the cable allows FPCs to perform well in applications that require frequent movement.
l Strong durability: FPCs are typically more resistant than FFCs to harsh conditions, like high temperatures and exposure to chemicals.
Disadvantages of FPCs:
l Higher cost: Due to their complex designs, FPCs require more materials and time to produce, making them typically more expensive than FFCs.
l Limited reusability: The circuits within each FPC are designed for specific purposes, so they can only be reused in projects that require the same functionality out of it.
l High design complexity: Compiling FPCs with advanced circuit patterns may take an extended time to complete.
Common Uses of FPCs:
l Smart watches: Due to their flexible build and advanced capabilities, FPCs are used in smart watches for functions like processing live health statistics collected from a sensor.
l Satellite solar panels: Inside satellites deployed to outer space, FPCs are used to connect the solar panels to the satellite's power management system. Light in weight, it helps to avoid excess fuel usage caused by additional weight.
l Consumer electronics: FPCs can be found in smartphones, tablets, laptops, and cameras, where space constraints and flexibility are crucial.
l Automotive: FPCs are used within complex automotive parts and systems like dashboard controls, infotainment systems, and advanced driver-assistance systems (ADAS).
l Medical devices: In the medical field, FPCs are found in diagnostic equipment, wearable health monitors, and imaging systems.
l Aerospace and defense: Due to their lightweight build, FPCs are incorporated within aerospace navigation systems, communication devices, and control panels.
l Industrial equipment: FPCs are commonly used within advanced equipment in areas like robotics, automation systems, and complex machinery.