Material Specification
Woven fiberglass reinforcement used in thin multilayer printed circuit board laminates provides mechanical stability and controls dielectric consistency. Fabricators specify 3313 glass when a board requires a thinner dielectric layer than standard 7628 glass can provide but needs more structural rigidity than ultra-thin styles allow. This style sits between the fine and heavy weave categories, controlling the finished thickness of individual cores or prepreg sheets.
It dictates the base height of the dielectric and determines the amount of resin required to fill the gaps between yarns during lamination.
Dielectric Influence
Signal propagation velocity depends on the ratio of resin to reinforcement within the dielectric layer. Because 3313 glass has a relatively open weave compared to denser weaves, it permits a higher resin content when fully impregnated. This higher resin concentration lowers the overall dielectric constant of the cured laminate, which stabilizes signal speed in high-speed digital designs.
Fabrication Behavior
Laser drilling through glass bundles can cause drill deflection or poor hole wall quality if the weave density varies too much. Laminates made with 3313 glass offer a more uniform distribution of glass filaments than coarser styles, which reduces microvia fabrication errors. This consistency during laser ablation prevents board rejection during automated optical inspection.
