A primary example of such advanced high-performance materials are Isola’s new thin-glass foils, which are des-tined to replace the establishedtechnique of resin-reinforced glass mats of chopped or cut glass fibers. One advantage of the pure-glass foils is theirlow temperature coefficient of 4ppm/K, compared to glass-fabric-reinforced epoxy laminates showing 10 to 15 ppm/K. Other important improvements would be in the dielectric coefficient and in the loss factor tangens delta – both strongly affecting and improving signal transmission.
In cooperation with Fraun-hofer IZM, Berlin/Germany, Isola has come up with extremely thin glass films that can be integrated into base materials as a reinforcing element. Isola reports to have successfully pressed such glass films between RCC for a copperlaminated base material or,for opto-electronic applications, replacing copper foils by glass foils altogether. These new base materials are used by the Swiss PCB maker PPC Electronic to jointly fabricate circuit boards that allow transmission rates beyond 2.5Gbit/s at the lowest possible loss due to the low tangens delta of glass. This makes it feasible, says PPC board member Peter Weber, to attach chip-scale devices directly to boards, including to BGA substrates, for almost ideal thermal and mechanical stability. All the other FR4 pro-cessing parameters and meth-ods, Weber suggests, would only need minor adaptations to the thin-glass technology. (ws)
