Landless multilayer circuit board and manufacturing method thereof

A manufacturing method of a landless multilayer circuit board, comprising steps of:

• providing a first substrate;
• wherein a first plating layer is mounted on the first substrate and a first photoresist layer is mounted on the first plating layer;
• patterning the first photoresist layer to form a groove of a first circuit pattern in the first photoresist layer, wherein the first plating layer is exposed in the groove of the first circuit pattern;
• forming a first circuit in the groove of the first circuit pattern on the first plating layer by plating the first plating layer to fill the groove of the first circuit pattern;
• removing the first photoresist layer to expose the first plating layer, and maintaining the first circuit;
• wherein a portion of the first plating layer is uncovered by the first circuit;
• removing a portion of the first plating layer that is uncovered by the first circuit, and maintaining the first circuit and a portion of the first plating layer that is covered by the first circuit;
• wherein a portion of the first substrate is uncovered by the first circuit and the first plating layer;
• forming a second photoresist layer on the first substrate to cover the first circuit and the portion of the first plating layer that is covered by the first circuit;
• patterning the second photoresist layer to form at least one via to expose a top surface of the first circuit;
• forming a second plating layer on a surface of the second photoresist layer and in the at least one via;
• wherein the second plating layer is electrically connected to the first circuit;
• forming at least one connecting pillar that fills the at least one via by plating the second plating layer in the at least one via;
• forming a third photoresist layer on the at least one connecting pillar and the plated second plating layer;
• patterning the third photoresist layer to cover at least one top of the at least one connecting pillar and to expose the plated second plating layer;
• removing a portion of the second plating layer that is uncovered by the third photoresist layer;
• removing the third photoresist layer;
• removing the second photoresist layer;
• forming a second substrate on the first substrate to cover the first circuit and the at least one connecting pillar;
• drilling the second substrate by laser to expose the at least one top of the at least one connecting pillar out of a surface of the second substrate;
• forming a third plating layer on the surface of the second substrate;
• wherein the third plating layer is electronically connected to the at least one connecting pillar;
• forming a fourth photoresist layer on a surface of the third plating layer;
• patterning the fourth photoresist layer to form a groove of a second circuit pattern in the second photoresist layer, wherein the third plating layer is exposed in the groove of the second circuit pattern;
• forming a second circuit in the groove of the second circuit pattern on the third plating layer by plating the third plating layer;
• removing the fourth photoresist layer to expose the third plating layer, and maintaining the second circuit;
• wherein a portion of the third plating layer is uncovered by the second circuit;
• removing a portion of the exposed third plating layer that is uncovered by the second circuit, the second circuit and a portion of the third plating layer that is covered by the second circuit are maintained;
• wherein a portion of the second substrate is uncovered by the second circuit and the third plating layer.