Flexible Circuit Board (FPC) Industry Development Trends
Flexible Circuit Board (FPC) Industry Development Trends
Flexible Circuit Board Structure CU (Copper Foil): E.D. and R.A. Copper Foil Cu is the copper layer. Copper foil is divided into RA (Rolled Annealed Copper) and ED (Electrodeposited). Due to different manufacturing principles, they have different properties. ED copper has low manufacturing cost but is brittle and easily breaks during bending or drilling. RA copper has high manufacturing cost but better flexibility, so FPC copper foil is mainly RA copper. A (Adhesive): Acrylic and Epoxy Thermosetting Adhesive The adhesive layer is mainly composed of acrylic resin and epoxy resin. PI (Kapton): Polyimide Film PI is an abbreviation for Polyimide, called Kapton at DuPont. The thickness unit is 1/1000 inch 1mil. Features include thinness, high temperature resistance, strong chemical resistance, and excellent electrical insulation. Currently, FPC insulation layers require soldering. Flexible Circuit Board Characteristics: Reduces product size, saves space, significantly reduces weight, increases functionality, and lowers costs. Highly flexible, allowing for three-dimensional wiring and shape adjustment to fit space constraints. Foldable without affecting signal transmission, resistant to electrostatic interference. Resistant to high and low temperatures, flame retardant. Chemically stable, with high stability and reliability. Provides more solutions for related products, reducing assembly time and errors, and extending product lifespan. Functions of Flexible Circuit Boards: The functions of flexible circuit boards can be categorized into four types: leads, printed circuits, connectors, and multi-functional integrated systems. Leads: Connections between rigid printed circuit boards, three-dimensional circuits, movable circuits, and high-density circuits. Printed Circuit Boards: High-density, thin, three-dimensional circuits Connectors: Low-cost connections between rigid boards Multi-functional Integrated Systems: Integration of rigid board leads and connectors Flexible circuitry is the circuitry for switches. It can be used as a circuit layer for switches or as a standalone conductive layer. It can be made with silver paste or FPC (Flexible Printed Circuit) technology. The manufacturing process can be determined according to customer requirements. Our engineering team recommends using FPC technology if the circuit has many LEDs or components, as this ensures better quality in all aspects. Flexible circuitry is available in three pitches: 2.54mm, 1.0mm, and 1.25mm. If pins are required, 2.54mm is recommended. If pins are not required and terminal connections are used, the routing should be based on the terminal requirements. Applications of Flexible Circuit Boards (PCBs) Flexible circuit boards are widely used in various electronic products and devices, including commercial electronic equipment, automotive dashboards, printers, hard drives, floppy disk drives, fax machines, car phones, telephones, laptops, cameras, camcorders, CD-ROMs, hard drives, watches, and medical instruments. Trends in Flexible Circuit Board Development Flexible Circuit Board Trends: Lightweight, Thin, and High-Density Technology 1. Liquid Crystal Polymer (LCP) Insulating Substrate Besides the development of new substrates, adhesive-free flexible circuit boards, and thin copper plating, other methods exist for achieving thinner flexible circuit boards. Regarding substrate materials, PI film has been used since the 1960s due to its excellent electrical, chemical, mechanical, and heat-resistant properties required for circuit boards and structures. However, with the increasing demands for higher circuit density and higher frequency/speed, PI film is no longer sufficient. The development of new substrates with thinness, high flexibility, and high density (high dimensional stability) has become a trend. Among these, the development of Liquid Crystal Polymer (LCP) has attracted the most attention. Compared to traditional PI film, it has a relative advantage in high-frequency/high-speed signal transmission and features a low dielectric constant and low hygroscopicity (1/10 that of PI). Low water absorption allows for thinner substrates and higher reliability in substrate structures. Furthermore, LCP's excellent thermoplasticity facilitates environmental recycling, making it considered the most likely potential replacement for traditional PI substrates. However, LCP currently remains expensive and still faces challenges such as compatibility with existing processes, adhesion to copper foil, high-temperature processing, and material anisotropy. Therefore, it is unlikely to threaten the stable mainstream position of PI substrates in the short term. But it is foreseeable that thinner and smaller designs will be the trend in future electronic products. Consequently, the thickness of insulating materials for flexible circuit boards has drastically decreased from the typical 25µm FCCL to 12.5µm, and even towards below 10µm. Reducing the thickness of flexible circuit boards to 10µm not only allows for a lighter and thinner appearance but also improves flexibility by more than 40%. However, the low manufacturing yield below 10µm inevitably leads to higher costs, indirectly affecting whether the thickness of PI film substrates can continue to decrease below 10µm. 2. Adhesive-Free Flexible Circuit Boards Gradually Replacing Adhesive-Based Flexible Circuit Boards Traditional flexible circuit board substrates generally use adhesives, but adhesive materials have poor thermal properties and reliability. Adhesive-free flexible circuit boards (2L-FCCL) can improve their electrical and thermal properties. Adhesive-free flexible circuit boards (2L-FCCL) have a thinner advantage than traditional adhesive-based flexible circuit boards (3L-FCCL). In recent years, due to increased manufacturing yield and improved production technology, the production volume of adhesive-free (2L-FCCL) flexible circuit boards has increased significantly, causing their price to approach that of adhesive-based (3L-FCCL) flexible circuit boards. This has led to a narrowing of the market share between the two, and market predictions suggest that adhesive-free (2L-FCCL) flexible circuit boards are poised to squeeze out and replace adhesive-based (3L-FCCL) flexible circuit boards. 3. Thinner Copper: Flexible Circuit Boards Have Higher Density Furthermore, thinner copper is also one of the methods for substrate thinning. Rolled copper foil (RA Foil) is mainly the conductive material for flexible circuit boards. The commonly used thicknesses of rolled copper foil in the market can be divided into mainstream specifications such as 1oz and 1/2oz. At present, the mainstream copper foil for flexible circuit boards has gradually shifted to the thinner 1/3oz specification. After the copper foil is thinner, it has a higher density feature.
