Correlating Glass Bundle Pitch Variation with High Frequency Phase Skew
Matching glass bundle pitch to trace geometry and using spread glass weaves eliminates local permittivity variations, bounding differential phase skew within tolerance.
1078 Weave Style
Fabric Architecture
Spread-glass fabric reinforcements use flattened yarns to create a more uniform dielectric environment than traditional weaves. The 1078 weave style is a specific fabric grade where the glass fibers are mechanically spread to cover more of the surface area, reducing the size of the resin-rich gaps.
Signal Quality
Signal quality is enhanced because the more uniform distribution of glass reduces the variations in the dielectric constant along a signal trace. Utilizing the 1078 weave style is a standard practice for boards that carry high-speed data where phase skew must be kept to a minimum.
Mechanical Stability
Mechanical stability of the laminate is also improved because the denser glass coverage provides better support for small vias and reduces the risk of resin cracking. Fabricators often choose this weave for thin-core applications where the total thickness of the dielectric is very small. During the lamination process, the 1078 weave style requires specific resin contents to ensure that the fabric is fully saturated and that no air is trapped between the spread fibers.
Microscopic inspection of the cross-sections confirms that the glass is properly distributed and that the layer thickness meets the requirements of the design. This weave choice is a requirement for high-reliability military and telecommunications hardware.