Do you know what ultra-thin fiberglass cloth is?
The key technologies in the manufacturing of ultra-thin fiberglass cloth include ultrafine fiber spinning, ultrafine fiber weaving, and high-fiber-opening processing.
A cross-sectional photograph of the copper-clad laminate (using D fiber diameter as an example) taken along its thickness after coating and drying reveals that the warp yarns are composed of 3-4 layers of medium-5μm monofilaments, and the weft yarns are composed of 2-3 layers of medium-5μm monofilaments, each interwoven. This results in a total of 5-7 layers of interwoven monofilaments, and the theoretical thickness of the fiberglass cloth is estimated to be 25-35μm. This indicates that the actual thickness of the copper-clad laminate produced from this fiberglass cloth is smaller than the theoretical thickness estimated from the number of monofilament layers in the warp and weft yarns. This is due to the deformation of the fiberglass monofilaments during the lamination process.
The use of ultra-thin fiberglass cloth in copper-clad laminate manufacturing presents a challenge. Because ultra-thin fiberglass cloth is constructed from very small diameter filaments, the resulting surface is smoother when laminated with copper foil, resulting in greater "surface contact" between the cloth and the copper foil. This is speculated to be one reason why the insulation properties of the interlayer circuit patterns in PCBs made with thinner fiberglass cloth decrease.
Therefore, the development of ultra-thin fiberglass cloth must address the aforementioned issue of reduced insulation resistance due to its smooth surface. To overcome this issue, key research areas include selecting the diameter of the filaments, the number of filaments in a single bundle, and controlling the total twist count of the warp and weft yarns. Furthermore, in this development, only by mastering the necessary processes for opening, dispersing, and recombining the filaments required for high-fiber-spreading technology can the total number of filament layers in the fiberglass cloth be effectively controlled.
Nitto Textile's ultra-thin fiberglass cloth, developed by developing and applying new fiberglass yarns, has advanced the field. Specifically, there are three types:
One uses C1200 yarn, composed of 4.5μm diameter monofilaments, to weave into Type 1037 fiberglass cloth, achieving a thickness of 25μm.
Another newly developed ultra-thin fiberglass cloth is woven from BC1500 yarn, composed of 4.0μm diameter monofilaments, resulting in a 20μm thick cloth.
Nitto Textile's latest development, responding to market demands for copper-clad laminates and printed circuit boards (PCBs), has resulted in a 16μm-thick fiberglass cloth using BC3000 yarn.
Fiber Spreading Technology
Ultra-thin fiberglass cloth's high fiber-spreading technology utilizes fiber-spreading technology to achieve better resin impregnation and higher prepreg production, thereby improving the performance of copper-clad laminates and PCBs.
Further developments in fiber-spreading technology led to the second phase. Maintaining the achievements of the first phase, fiber-spreading addressed the need for improved processability of copper-clad laminates and printed circuit boards (PCBs) during C02 laser drilling and micro-hole machining. At the time, Nitto Textile Co., Ltd. developed this fiber-spreading fabric, exemplified by its 1078 glass fiber fabric (equivalent to 50μm thick). This fabric achieved high flattening of the glass yarns and horizontally spread the monofilaments. This second phase of fiber-spreading addressed the problem of large gaps between the warp and weft yarns in existing fiber-spreading fabrics. This problem resulted in uneven resin content at the intersections and gaps between the warp and weft yarns. Consequently, during C02 laser drilling, the fiber-spreading process resulted in inconsistent hole diameters and other dimensions due to the different absorption of laser light energy at the intersections and gaps. The improved fiber-spreading process enhances the uniformity of glass fiber cloth.
The manufacturing technology for ultra-thin fiberglass cloth inherits the fiber-spreading technology from two development stages, achieving a more uniform and dispersed interweaving of warp and weft yarns in the plane. Furthermore, this high-spreading technology not only achieves high flatness of the glass fiber yarn, but also improves the horizontal flatness and dispersion of the individual filaments. It also includes techniques for recombining individual filaments and reducing the number of overlapping layers.
The cross-sectional morphology of 16μm thick fiberglass cloth after high-spreading treatment is compared with that of non-high-spreading treatment.
The yarn composed of non-high-opening fiberglass cloth has a total of 8 layers of overlapping monofilaments (Max: 5+3=8 layers). After the fiber-opening treatment, the glass fiber yarn becomes highly flat, and the monofilaments move, and new combinations and arrangements appear, which reduces the number of overlapping monofilament layers to 1~2 layers, and the total number of overlapping monofilament layers of warp and weft yarns is 4 layers. Therefore, although both of the two differently processed fiberglass cloths use BC3000 yarn, the thickness of the copper clad laminate made of the non-opening fiberglass cloth is 32μm, while the glass fiber cloth with high fiber-opening treatment has a thickness of only 16μm due to the recombination of monofilaments.
