Wiring board and method for manufacturing wiring board

A wiring board comprising:

• an external connection terminal of which bottom surface is visible;
• an insulating layer around the external connection terminal, the insulating layer consisting of a single layer;
• and
• a wiring layer that is layered on the insulating layer and is electrically connected with the external connection terminal through a via provided in the insulating layer;
• wherein the bottom surface of the external connection terminal and a bottom surface of the insulating layer are in a same plane, and
• the external connection terminal has a bottom conductive layer that constitutes the bottom surface of the external connection terminal, the external connection terminal including a plurality of columnar protrusions formed to protrude upward into the insulating layer on a top surface of the bottom conductive layer.

A method for manufacturing a wiring board including an external connection terminal of which bottom surface is visible, an insulating layer around the external connection terminal, and a wiring layer that is layered on the insulating layer and is electrically connected with the external connection terminal through a via provided in the insulating layer, the method comprising:

• an external connection terminal forming step of forming the external connection terminal on a supporting board;
• an insulating layer forming step of forming the insulating layer around the external connection terminal, the insulating layer having a bottom surface in a same plane as the bottom surface of the external connection terminal and consisting of a single layer;
• a via forming step of forming the via that electrically connects the external connection terminal with the wiring layer;
• and
• a wiring layer forming step of forming the wiring layer on top of the insulating layer;
• wherein the method further comprises, after forming a bottom conductive layer that constitutes the bottom surface of the external connection terminal, a step of forming a plurality of columnar protrusions that protrude upward into the insulating layer from a top surface of the bottom conductive layer.