The mixed dielectric approach combines standard fiberglass reinforced materials for non-critical signal layers such as power and ground planes with a low dielectric constant, low loss prepreg, SPEEDBOARD C prepreg, for critical signal layers. While the use of standard fiberglass laminates provides a cost savings, the SPEEDBOARD C prepreg affords the electrical advantages of faster signals, thinner and lighter printed wiring boards (PWBs), increased signal integrity, and wider traces.
SPEEDBOARD C prepreg is comprised of expanded polytetrafluoroethylene (ePTFE) that has been impregnated with a modified BT resin. The air space inside the ePTFE is replaced with resin and the ePTFE membrane becomes the carrier or delivery system for the resin. Ultimately, the resin flows, fills and bonds during the lamination process in the same manner as a conventional glass-based thermoset prepreg. The comfortable ePTFE toughens the dielectric, improving reliability and enabling excellent surface planarization for high-density fine lines and spaces.
In addition to its use in mixed dielectric constructions, SPEEDBOARD C prepreg performs well in high-speed digital applications. It is also an optimum choice to replace thermoplastic fluoropolymer bondfilms and fusion bonding processes in PTFE microwave PWBs.
This advanced prepreg material features a dielectric constant of 2.6 and a low loss tangent of 0.0036 that is stable over both frequency (1 MHz to 10 GHz) and temperature ( 55 ° C to 200 ° C). It utilizes standard thermoset processing as opposed to fusion bonding and exhibits excellent adhesion to all laminates (FR-4, GETEK®, hydrocarbon, and PTFE). The controlled flow and fill characteristics of this Gore product make it ideal for cavity applications as well.