PRINTED BOARD AND ITS PRODUCTION

PURPOSE:To obtain a highly reliable multilayer wiring board by making thin the interlayer insulation layer at the blind via hole part thereby making shallow the hole and decreasing the contact area between the plating film on the side wall in the hole and the insulating layer. CONSTITUTION:When unit printed wiring boards 1a, 1b are laminated through an insulating layer 6, the thickness of the insulating layer 6 is differentiated between a region 6 where a main wiring pattern 3, e.g. a signal line, is formed and a a region 6a where a blind via hole 9 is formed. In the region 6 where the wiring pattern is formed, the thickness of the insulating layer 6 is set at an optimal value for ensuring the circuit characteristics (characteristic impedance, dielectric strength, interlayer crosstalk, etc.) and the interlayer insulating film 6a between a surface land 7 and an inner layer land 2 is set thinner than the optimal value. This structure reduces crack in a plating layer 5b on the inner wall of blind via hole caused by the difference in the coefficient of thermal expansion as compared with the insulating layer 6a.