Reinforcement Geometry
A lightweight woven fiberglass cloth with a spread-yarn configuration provides the structural reinforcement in thin printed circuit board laminates. Specifically, prepreg glass style 1078 features flat, spread yarn bundles that reduce the open window area between the woven fibers compared to older styles. This uniform fiber distribution provides a flat, consistent surface for the outer layers of high-density boards.
Using this style prevents the localized fiber weave effects that degrade high-speed signal propagation.
Dielectric Uniformity
The flattened yarn profile of this material distributes the glass and resin more evenly across the layer. Traditional glass styles have thick, tightly twisted bundles with large resin-rich gaps between them, which creates localized variations in the dielectric constant. In contrast, prepreg glass style 1078 creates a highly uniform dielectric medium, which reduces signal skew on differential trace pairs.
This uniformity is necessary for applications running above twenty-eight gigabits per second, where skew must be minimized to maintain timing budgets.
Resin Content
High resin capacity of the open weave pattern allows it to bond effectively with copper layers and fill internal trace voids during lamination. This high resin content also improves laser-drill performance, as the laser can ablate the uniform fiber-resin mixture without creating uneven via shapes. Consequently, this glass style is favored for high-density interconnect designs.
