A novel type of low dielectric and heat-resistant resin for printed wiring boards

We developed a novel type of low dielectric and heat-resistant resin. The resin was synthesized from dehydrating reaction between fused aromatics and 1,4-benzenedimethanol, therefore, it was called advanced polyCOndensed fused PolyNuclear Aromatic Resin (advanced COPNA-Resin). The advanced COPNA-Resin exhibited characteristic properties for an electrical insulator: e.g., high Tg (250°C), low dielectric constant (3.1 for 1 MHz), and low water absorption (0.37 wt.%). We studied fabrication and properties of prepregs, double-sided copper-clad laminates, printed wiring boards with copper-plated through-holes using advanced COPNA-Resin as an insulating material. Prepregs were fabricated by the dipping process of E-glass or T-glass fiber woven fabrics into the resin solution. Copper-clad laminates were obtained by hot-press fabrication of advanced COPNA-Resin prepregs. The laminates reinforced by E-glass fiber woven fabric exhibited characteristic properties for multilaying printed wiring boards. Tg was 255°C. The dielectric constant was 4.2. Advanced COPNA-Resin laminates exhibited higher Tg and lower dielectric constant than polyimide laminates known as heat-resistant and low dielectric materials. The linear thermal expansion coefficient of advanced COPNA-Resin laminates for xy-axis was 4-5 ppm, and that for z-axis was 29 ppm. Advanced COPNA-Resin printed wiring board exhibited outstanding reliability of electrical connection of copper-plated through-holes in comparison with the epoxy or the polyimide system. From those analysis for Tg, dielectric constant, linear thermal expansion coefficients, and through-hole reliability, the advanced COPNA-Resin was regarded as novel type of advanced material for high-density interconnects such as fine-pitch surface mount and multichip modules