Circuit board and method of manufacturing circuit board

A method of manufacturing a circuit board, the method comprising:

• preparing a fluororesin laminate including a fluororesin layer having a first main surface and a second main surface opposite to the first main surface, and a second metal layer disposed on the second main surface;
• preparing a first resin laminate including a first resin layer having a third main surface and a fourth main surface opposite to the third main surface, and a first metal layer disposed on the third main surface;
• preparing an adhesion layer;
• forming a first laminate by stacking the fluororesin laminate, the adhesion layer, and the first resin laminate in this order such that the first main surface is in contact with the adhesion layer and holding the adhesion layer at a temperature of 180° C. or lower to soften the adhesion layer, thereby bonding the fluororesin laminate and the first resin laminate together;
• removing at least a part of the fluororesin layer and at least a part of the adhesion layer to form a through-hole extending through the fluororesin layer and the adhesion layer;
• and
• forming a connecting portion on an inner wall surface of the fluororesin layer defining a part of the through-hole and an inner wall surface of the adhesion layer defining a part of the through-hole,
• wherein the fluororesin layer contains polytetrafluoroethylene and a first inorganic filler,
• a content of the first inorganic filler in the fluororesin layer is 50% by volume to 66% by volume,
• the adhesion layer contains a resin and a second inorganic filler,
• a content of a fluororesin in the resin is 5% by mass or less, and
• a content of the second inorganic filler in the adhesion layer is 29% by volume to 47% by volume.