Overview of epoxy fiberglass cloth clad copper sheets

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In complete electronic products, copper-clad laminates serve three functions: supporting components, enabling circuit interconnection, and providing insulation between circuits. Depending on the substrate used, copper-clad laminates are mainly classified into several categories, including paper-based copper-clad laminates, fiberglass cloth copper-clad laminates, composite substrate copper-clad laminates, and flexible copper-clad laminates. Epoxy fiberglass copper-clad laminates feature high strength, good heat resistance, and excellent dielectric properties. The vias in these substrates can be metalized (commonly known as via metallization), enabling electrical connection between the layers of double-sided or multi-layer printed circuits. As a result, epoxy fiberglass copper-clad laminates are the most widely used and largest in volume among all types of copper-clad laminates. It is widely used in products such as communications, mobile communications, computers, instruments, digital TVs, CNC audio systems, satellites, and radars. In the production of various types of copper-clad laminates worldwide, paper-based copper-clad laminates and epoxy fiberglass cloth copper-clad laminates account for approximately 92% of the total. In terms of area, the output of epoxy fiberglass cloth copper-clad laminates is slightly greater than that of paper-based copper-clad laminates; in terms of weight or value, however, they **exceed** paper-based copper-clad laminates. Paper-based copper-clad laminates are mostly used in household appliances. Currently, paper-based copper-clad laminates are rarely produced and used in Europe and the United States, while their production and use remain relatively high in Asia. As electronic products evolve toward being lighter, thinner, shorter, smaller, and more digital, printed circuit boards are developing towards finer patterns as well as higher density and more layers. Electronic products that originally used paper-based copper-clad laminates gradually switched to fiber glass cloth copper-clad laminates, which slowed down the development of paper-based copper-clad laminates. In contrast, fiber glass cloth copper-clad laminates, especially those used in multi-layer PCBs, saw more rapid development. Copper-clad laminates are mainly composed of three components: copper foil, substrate, and adhesive. Common adhesives used for copper-clad laminates include phenolic resin, epoxy resin, modified epoxy resin, polyimide resin, cyanate ester resin, PPO resin, BT resin, etc. Copper-clad laminates made from epoxy resin are widely used in single-sided, double-sided, and general multi-layer printed circuit boards due to their low cost, favorable manufacturing process, as well as excellent dielectric and mechanical processing properties. Copper-clad laminates made with epoxy resin or modified epoxy resin as adhesives are the most produced and widely used type of copper-clad laminate currently. Under the NAME standard (the standard set by the American Electrical Manufacturers Association), epoxy fiberglass cloth-covered copper clads come in four types: G-10 (non-flammable), FR-4 (flame-retardant), G-11 (retains heat resistance, non-flammable), and FR-5 (retains heat resistance, flame-retardant). Since safety and fire prevention requirements were imposed on electrical products, electrical products entering the United States must undergo safety certification by the Underwriters Laboratories (commonly referred to as UL certification). In copper-clad plate products, the use of non-flame-retardant products is gradually decreasing. In epoxy glass fiber cloth copper-clad laminates, over 90% of the products are of the FR-4 type. Current FR-4 products have evolved into a broad category of epoxy glass fiber cloth-covered copper-clad laminates that can be used for various purposes. The FR-4 type copper-clad plate products that are designated in the IP-4101 standard include Product No. 24; its resin system is based on modified or unmodified epoxy resins, with a flame-retardant Tg of 150~200℃ ； Product No. 25 uses an epoxy/PPO resin system, with a flame-retardant Tg of 150–200°C. Product No. 26 uses an epoxy resin system (for the addition process), and also has flame-retardant properties. Many overseas copper-clad plate manufacturers also develop FR-4 as a series of products to meet the various performance requirements for PCB manufacturing, and this approach is worth emulating by domestic copper-clad plate producers. Among FR-4 products, there is another type that is not a copper-clad plate, but still has very high sales volumes – pre-pregs. Semi-cured sheets are used to bond the various inner layers together in the production of multi-layer printed circuits, and they are also products with high performance requirements. The production processes for copper-clad laminates made from different types of epoxy fiberglass cloth are essentially the same; the main difference between them lies in the resin formula. The production process for epoxy fiberglass cloth-covered copper clads is generally carried out in stages, and it consists of four main phases: the first phase is resin preparation ； The second step is applying glue to the substrate ； The third section is lamination (referred to as bookbinding abroad) and layering ； The fourth paragraph covers trimming, inspection, and packaging. The production process flow is shown in the figure