Substrate containing low-Dk-core glass fibers having low dielectric constant (Dk) cores for use in printed circuit boards (PCBs), and method of making same

A method of making a substrate containing low-Dk-core glass fibers, the method comprising:

• providing a substrate having a plurality of insulator layers and one or more conductive traces, wherein each of the insulator layers comprises a glass fiber substrate impregnated with a varnish coating, wherein a plurality of through-holes each of which extends completely through the substrate from a first surface of the substrate to a second surface of the substrate and passes through the glass fiber substrate of each of the insulator layers, and wherein the glass fiber substrate of one of the insulator layers includes one or more hollow glass fibers extending from a first one of the through-holes to a second one of the through-holes;
• forming a silane polymer barrier layer over a first end of each of the one or more hollow glass fibers in the first one of the through-holes;
• forming a silane polymer barrier layer over a second end of each of the one or more hollow glass fibers in the second one of the through-holes;
• wherein the silane polymer barrier layer formed over the first end of each of the hollow glass fibers and the silane polymer barrier layer formed over the second end of each of the hollow glass fibers seal a low Dk fluid within the hollow glass fibers, thereby forming a low-Dk-core glass fiber.