Circuit board, method of manufacturing circuit board, and electronic device

A method of manufacturing a circuit board, comprising

• stacking a first substrate and a second substrate,
• the first substrate including a first through hole, a metal layer formed over an inner wall of the first through hole, and a first conductive composite resin provided on an inner side of the metal layer of the first through hole,
• the second substrate including a second through hole and a second conductive composite resin provided in the second through hole,
• wherein the second through hole is formed to face the first through hole and have an open end on a side of the first through hole, the open end being located on an inner side of the metal layer,
• the first conductive composite resin is coupled to the second conductive composite resin, and
• wherein a diameter of the inner side of the first metal layer formed on an inner side of the first through hole has a greater value than a diameter of a first open end-side end of the second conductive composite resin,
• the first open end-side end of the second conductive composite resin is not directly connected to the first metal layer but is directly connected to only the first conductive composite resin provided on the inner side of the first metal layer,
• wherein the second through hole has a second open end on the opposite side from the first open end, and the second open end has a greater inner diameter than the first open end,
• further comprising:
• stacking, over the second substrate on the opposite side from the first substrate, a third substrate including a third through hole that faces the second through hole, a third metal layer provided over an inner wall of the third through hole, and a third conductive composite resin provided on an inner side of the third metal layer of the third through hole,
• wherein an outer edge of the second conductive composite resin is located outside an inner edge of the third metal layer.

An electronic device comprising:

• a circuit board;
• and
• an electronic component mounted on the circuit board,
• wherein the circuit board includes:
• a first substrate including a first through hole, a first metal layer formed over an inner wall of the first through hole, and a first conductive composite resin provided on an inner side of the first metal layer of the first through hole;
• and
• a second substrate stacked together with the first substrate and including a second through hole that faces the first through hole and has a first open end which is provided on a side of the first through hole and is located on the inner side of the first metal layer, and a second conductive composite resin that is provided in the second through hole and is coupled to the first conductive composite resin, and
• wherein a diameter of the inner side of the first metal layer formed on an inner side of the first through hole has a greater value than a diameter of a first open end-side end of the second conductive composite resin,
• the first open end-side end of the second conductive composite resin is not directly connected to the first metal layer but is directly connected to only the first conductive composite resin provided on the inner side of the first metal layer,
• wherein the second through hole has a second open end on the opposite side from the first open end, and the second open end has a greater inner diameter than the first open end,
• wherein the circuit board includes:
• a third substrate that is stacked over the second substrate on the opposite side from the first substrate, and includes a third through hole that faces the second through hole, a third metal layer provided over an inner wall of the third through hole, and a third conductive composite resin provided on an inner side of the third metal layer of the third through hole,
• wherein an outer edge of the second conductive composite resin is located outside an inner edge of the third metal layer.