Method of manufacturing multi-layer circuit board including extreme fine via and multi-layer circuit board manufactured by the same

A method for manufacturing a multi-layer circuit board comprising an extreme fine via, the method comprising:

• providing a board comprising:
• one surface on at least a part of which an upper conductive layer is formed;
• and
• an other surface on at least a part of which a lower conductive layer is formed;
• forming a lower metal layer on the other surface of the board;
• forming a first resist layer on the one surface of the board through a photolithography process, and forming a first opening on the first resist layer;
• forming a metal pillar comprising a diameter of 14 μm to 25 μm by plating the first opening by using an electrolytic plating method;
• removing the first resist layer;
• forming an insulating layer on a location from which the first resist layer is removed;
• evenly polishing the metal pillar and the insulating layer;
• forming an upper metal layer on one surface of the metal pillar and one surface of the insulating layer after completion of the evenly polishing the metal pillar and the insulating layer;
• forming a second resist layer on one surface of the upper metal layer through the photolithography process and forming a second opening on the second resist layer;
• forming a plating layer by plating the second opening;
• removing the second resist layer;
• and
• removing the upper metal layer exposed to outside and the lower metal layer exposed to the outside, wherein the metal pillar is one of a plurality of metal pillars arranged such that an interval between centers of each of the plurality of metal pillars is 30 μm to 50 μm.