| 摘要 |
PROBLEM TO BE SOLVED: To provide an electronic device in which the linear expansion coefficient of a wiring board can be reduced, curvature deformation of the wiring board can be suppressed and eventually warp of the whole device can be suppressed by reducing the linear expansion coefficient of an area where an inner layer conductor is buried in a built-up layer.SOLUTION: In a plate-shaped built-up layer 30 as a prepreg obtained by sealing glass clothes 1, 2 with insulating resin 3, the first glass cloth 1 is located in a first area R1 which is nearer to an outer surface 30b than an inner layer conductor 51 in the thickness direction of the built-up layer 30 in the resin 3, the second glass cloth 2 is located in a second area R2 corresponding to the thickness d of the inner layer conductor 51 from the inner surface 30a in the thickness direction of the built-up layer 30 in the resin 3, the second glass cloth 2 is provided with a through-hole 2a, and the inner layer conductor 51 is disposed in the through-hole 2a. Therefore, the arrangement is planar such that the second glass cloth 2 is interposed at the interval of the inner layer conductor 51 in the resin 3. |
