Masakazu Ohkita

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/spl deg/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/spl deg/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. >

Reliability of the laminate from advanced COPNA-resin/E-glass fabrics system

Reliability of the advanced COPNA-resin laminate which exhibited high glass transition temperature (Tg) at 255/spl deg/C, low coefficient of thermal expansion (CTE) at 5-7 ppm (xy-axis) and at 29 ppm (x-axis) was evaluated by temperature-humidity-bias (THB) test, pressure-cooker (PC) test, heat-shock test, heat-cycle test, and conductive anodic filaments (CAF) test. The laminate exhibited higher reliability than the FR-4 graded epoxy-resin laminate in every test, and exhibited higher reliability than the bismaleimide-triazine resin laminate in the THB test, heat-shock test, and heat-cycle test. The high reliability of the advanced COPNA-resin system is considered to be due to its high Tg and small CTE. In this paper, low CTEs of the advanced COPNA-resin laminate are also theoretically studied by using a model for uni-axially reinforced composites.

A new small CTE system from COPNA resin/E‐glass fabrics

Based on the superior properties of the COPNA resin laminate exhibiting Tg at 255∞C, small CTE at 5‐7 ppm (xy‐axis) and at 29 ppm (z‐axis), reliability of both two‐layered and six‐layered printed wiring boards using COPNA resin as a matrix were evaluated. In the case of the two‐layered system, it exhibited higher reliability than the FR‐4 graded epoxy‐resin laminate in the entire tests, and exhibited higher reliability than the BT resin laminate in the THB test, heat‐shock test, and heat‐cycle test. In the case of the six‐layered system, it also exhibited higher reliability than the BT system in both heat‐shock test and PC test.