Multilayer board and fabrication method thereof

A multilayer board comprising:

• a smooth-surfaced double-sided board having:
• a base material provided with a hole penetrating therethrough,
• a first layer wiring pattern provided on both surfaces of said base material and having a surface, and
• conductive material filled in said hole, said filler having ends being substantially flush with said surface of said first layer wiring pattern, thus forming a via hole portion having ends;
• an insulating layer provided on at least one surface of said double-sided board, said insulating layer being formed with an opening having an inner wall;
• and
• a second layer wiring pattern comprising a plating layer provided on said double-sided board through said insulating layer;
• wherein at least a portion of one of said ends of said via hole portion is exposed in said opening, and wherein said inner wall of said opening and exposed portion of said end of said via hole portion are coated with a plating layer connecting to said plating layer of said second layer wiring pattern, thus establishing electrical connection between said second wiring pattern and said via hole portion;
• and
• said first layer wiring pattern having a connecting terminal portion which electrically connects with the via hole portion, wherein said via hole portion and said connecting terminal portion of the first layer wiring pattern which connects with the via hole portion are coated with a continuous plating layer, thus establishing electrical connection between said first layer wiring pattern and said via hole portion.