Fiber Pattern
Structural configurations of woven fiberglass sheets embedded in circuit board laminates provide mechanical strength and dimensional stability to the substrate. The woven glass weave consists of intersecting warp and fill yarns that create a mesh-like support structure for the epoxy resin. This reinforcement is essential for preventing board shrinkage and warpage during thermal lamination and soldering.
Electrical Variation
High-speed signals are highly sensitive to the patterns of the fiberglass reinforcement due to the difference in dielectric constant between the glass and the resin. The woven glass weave creates a non-uniform electrical environment where signals experience a higher dielectric constant when running directly over glass bundles compared to resin-rich gaps. This variation is known as the glass-weave effect, which causes phase skew and impedance fluctuations in high-speed differential pairs.
To mitigate this effect, designers often route traces at an angle to the weave or select tighter, flatter weave styles that offer a more homogeneous dielectric environment. This layout strategy is verified during signal integrity testing on prototype boards.
Material Selection
Different weave styles, such as 1080, 2116, or 7628, are selected based on the required board thickness and dielectric properties. These style designations define the yarn count and thread density of the woven glass weave, allowing fabricators to optimize the resin-to-glass ratio for each design. This choice is critical for achieving a balance between mechanical durability, thickness precision, and signal performance.
