Printed wiring board and method for manufacturing printed wiring board

A method for manufacturing a printed wiring board, comprising:

• laminating a first core substrate having a through-hole conductor formed through the first core substrate and a second core substrate having a through-hole conductor formed through the second core substrate;
• forming a first upper buildup layer on a surface of the first core substrate;
• forming a second upper buildup layer on a surface of the second core substrate;
• separating the first core substrate and the second core substrate from each other;
• laminating the first upper buildup layer formed on the first core substrate and the second upper buildup layer formed on the second core substrate;
• forming a first lower buildup layer on an opposite surface of the first core substrate;
• forming a second lower buildup layer on an opposite surface of the second core substrate;
• and
• separating the first upper buildup layer and the second upper buildup layer,
• wherein the first upper buildup layer has an outermost resin insulation layer comprising a material different from a material of an outermost resin insulation layer of the first lower buildup layer, the second upper buildup layer has an outermost resin insulation layer comprising a material different from a material of an outermost resin insulation layer of the second lower buildup layer, the outermost resin insulation layer of the first upper buildup layer has a thermal expansion coefficient which is lower than a thermal expansion coefficient of the first core substrate, the outermost resin insulation layer of the first lower buildup layer has a thermal expansion coefficient which is higher than a thermal expansion coefficient of the first core substrate, the outermost resin insulation layer of the second upper buildup layer has a thermal expansion coefficient which is lower than a thermal expansion coefficient of the second core substrate, the outermost resin insulation layer of the second lower buildup layer has a thermal expansion coefficient which is higher than a thermal expansion coefficient of the second core substrate, the outermost resin insulation layer of the first lower buildup layer does not have a reinforcing material, and the outermost resin insulation layer of the second lower buildup layer does not have a reinforcing material.

A method for manufacturing a printed wiring board,

• laminating a first core substrate having a through-hole conductor formed through the first core substrate and a second core substrate having a through-hole conductor formed through the second core substrate;
• forming a first upper buildup layer on a surface of the first core substrate;
• forming a second upper buildup layer on a surface of the second core substrate;
• separating the first core substrate and the second core substrate from each other;
• laminating the first upper buildup layer formed on the first core substrate and the second upper buildup layer formed on the second core substrate;
• forming a first lower buildup layer on an opposite surface of the first core substrate;
• forming a second lower buildup layer on an opposite surface of the second core substrate;
• and
• separating the first upper buildup layer and the second upper buildup layer,
• wherein the laminating of the first core substrate and the second core substrate comprises positioning a first metal foil over a surface of the first core substrate such that a peripheral portion of the surface of the first core substrate is exposed from the first metal foil, a second metal foil over a surface of the second core substrate such that a peripheral portion of the surface of the second core substrate is exposed from the second metal foil, and a prepreg between the first metal foil and the second metal foil, and applying heat-pressing to the prepreg such that the first core substrate and the second core substrate are adhered through the prepreg on the peripheral portion of the surface of the first core substrate and the peripheral portion of the surface of the second core substrate, the outermost resin insulation layer of the first upper buildup layer has a thermal expansion coefficient which is lower than a thermal expansion coefficient of the first core substrate, the outermost resin insulation layer of the first lower buildup layer has a thermal expansion coefficient which is higher than a thermal expansion coefficient of the first core substrate, the outermost resin insulation layer of the second upper buildup layer has a thermal expansion coefficient which is lower than a thermal expansion coefficient of the second core substrate, the outermost resin insulation layer of the second lower buildup layer has a thermal expansion coefficient which is higher than a thermal expansion coefficient of the second core substrate, the outermost resin insulation layer of the first lower buildup layer does not have a reinforcing material, and the outermost resin insulation layer of the second lower buildup layer does not have a reinforcing material.