| 摘要 |
PURPOSE:To prevent the outermost face of a copper foil from being rumpled and the copper foil from being cut, and to reduce its warp and change in size by a method wherein a coefficient of linear expansion of a specular sheet as a backing sheet to be used at a heating operation and a pressurization operation and a coefficient of linear expansion of the copper foil to be used are specified. CONSTITUTION:A coefficient of linear expansion in a range of 0.8 to 1.5 of a specular sheet against a coefficient of linear expansion at 1 of a copper foil to be used is selected and used as the specular sheet. When a ratio of the coefficient of linear expansion at 0.8 or lower of the specular sheet is used, a strain at a heating operation of the copper foil remains at a recessed part produced when a circuit is formed on an inside-layer circuit board and a rumple is caused in a resin flowing region of a prepreg during a heating operation and a pressurization operation because the coefficient of linear expansion of the copper foil is larger than that of the specular sheet. When a ratio of the coefficient of linear expansion at 1.5 or higher of the specular sheet is used, the copper sheet is pulled by the specular sheet in the resin flowing region of the prepreg during the heating operation and the pressurization operation because the coefficient of linear expansion of the copper foil is smaller than that of the specular sheet; the copper foil is easily cut by a generated tensile stress. |
