| 摘要 |
PROBLEM TO BE SOLVED: To provide a technique which allow for formation of a small diameter via hole having good via shape, in an insulating layer containing an inorganic filler, when manufacturing a circuit board.SOLUTION: In a circuit board including an insulating layer, where a via hole having an opening size of 15 μm or less is formed, the arithmetic average roughness (Ra) of the surface of the insulating layer is 150 nm or less, and the insulating layer contains an inorganic filler 12. In the cross section of the insulating layer in a direction perpendicular to the surface thereof, when the average value of the maximum diameter of the inorganic filler 12 included in a region of a predetermined width is n(μm), the value (n) of n×1.27 is 0.2 μm or less.SELECTED DRAWING: Figure 1 |
