PURPOSE: To preserve the reliability on the insulation between parts mounting pads and prevent the drop of reliability on soldering by providing a liquid-form solder resist at the parts mounting pad of an insulating board and in its vicinity, and dry solder resist for masking the other parts.

CONSTITUTION: The parts mounting pad 2 of an insulating board and its vicinity are coated with liquid-form solder resist 4, and after set to touch, it is exposed to UV and developed and thermoset to form cured liquid-form solder resist 6. Next, dry film resists 7 are laminated on both sides of the insulating board 1, and through films 5, both sides are exposed to UV at the same time and are developed to make a hardened dry film solder resist 8 by UV curing and thermocuring.