High density multilayer printed circuit board for HITAC M-880

Investigations were performed on ways to raise signal transmission velocity of printed circuit boards (PCBs). A low dielectric laminate (dielectric constant=3.7) for the PCBs, which has almost the same thermal stability and flame retardancy as a polyimide one, was produced by a maleimide-styryl (MS) resin synthesis based on a molecular design technique in combination with optimum reinforcement. A high aspect ratio fine pattern formation process was established by pattern copper plating. Signal linewidth was 70 μm and its thickness was 65 μm. A high aspect ratio fine through-hole formation process was derived by optimization of the drilling conditions. Using all these technologies, a high density, multilayer printed circuit board (MPB) with 46 layers and 730 mm by 534 mm in size was developed. This high-performance MPB was applied to the HITAC M-880, the newest and largest mainframe computer manufactured by Hitachi