| 摘要 |
PROBLEM TO BE SOLVED: To solve a problem of not being able to increase the density of wiring conductors because of a wide electrical contact area required in a stacked-via structure. SOLUTION: In this wiring substrate, a first insulating resin layer 1a on the upper face of which a first wiring conductor 2a is formed, a second insulating resin layer 1b on the upper face of which a second wiring conductor 2b is formed, and a third insulating layer 1c, are sequentially stacked so that a part of the first and second wiring conductors are vertically overlapped. A first through hole 3a positioned on the first wiring conductor 2a and piercing both the second insulating resin layer 1b and the second wiring conductor 2b, and a second through hole 3b positioned on just the upper part of the through hole 3a piercing the third insulating resin layer 1c and having a cross section larger than that of the first through hole 3a, are formed. A metal thin-film 4 is formed covering from the inner walls of the first and second through holes 3a, 3b to the upper face of the third insulating resin layer, so that the first wiring conductor 2a, the second wiring conductor 2b, and a third wiring conductor 2c which consists of the metal thin-film 4 formed on the upper face of the third insulating resin layer 1c, are mutually connected. |
