| 摘要 |
PROBLEM TO BE SOLVED: To improve resolution of a photo bias hole and moisture resistance and hardness of insulating layers, by temporarily drying, exposing and developing the insulating layers on inner layer circuit patterns, forming the photo bias hole, exposing again, roughing the insulating layers after thermal hardening, and forming an outer layer circuit pattern. SOLUTION: Insulating layers 3, 3 are spread on an upper surface 1a and a lower surface 1b of an insulating board 1 in which inner layer circuit patterns 2a, 2a are formed, temporarily curved (80 deg.C, 10-30 minutes), temporarily dried, exposed and developed, and a photo bias hole 4 is formed. After that, ultraviolet ray is applied thereto again, and thermal hardening is performed. Then thermal hardening by heat is performed at 130-180 deg.C for 15-60 minutes, and the final insulating layers 3 are formed. A through hole 5 is formed in a specified part of the board, and the inside surface of the through hole 5 and the surfaces of the insulating layers 3, 3 are roughed. The outer layer conductors 6, 6 are formed on the upper and the lower surfaces of the insulating layers 3, 3, photosensitive resist is spread, dried, exposed and developed, and outer layer circuit patterns 6a, 6a are formed. |
