WIRING BOARD

To improve a connection reliability of a wiring board.SOLUTION: A wiring board of an embodiment, comprises: a first conductive pattern 111 and a second conductive pattern 112 which are opposite each other; a plating conductor 42 that is integrally formed with the second conductive pattern 112 so as to be contacted to the first conductive pattern 111; and an insulation layer 22 that includes a penetration hole 6 filled by the plating conductor 42 is interposed between the first conductive pattern 111 and the second conductive pattern 112. The penetration hole 6 includes an expansion part 6a that expands an open width of the penetration hole 6 on the first conductive pattern 111 side, and the plating conductor 42 contains: a first plating film 4a directly formed in an inner wall of the penetration hole; and a second plating film 4b formed on the first plating film 4a. The minimum thickness of the first plating film 4a in the expansion part 6a is 55% or more and 95% or less of the minimum thickness of the first plating film 4a in the penetration hole 6 in a part 6b other than the expansion part 6a.SELECTED DRAWING: Figure 2 【課題】配線基板の接続信頼性の向上。【解決手段】実施形態の配線基板は、互いに対向する第１導体パターン１１１及び第２導体パターン１１２と、第２導体パターン１１２と一体的に形成されていて第１導体パターン１１１と接しているめっき導体４２と、めっき導体４２で充填されている貫通孔６を有していて第１導体パターン１１１と第２導体パターン１１２との間に介在する絶縁層２２と、を含んでいる。貫通孔６は、第１導体パターン１１１側の貫通孔６の開口幅を広げる拡張部６ａを有し、めっき導体４２は、貫通孔の内壁に直接形成されている第１めっき膜４ａと、第１めっき膜４ａ上に形成されている第２めっき膜４ｂと、を含み、拡張部６ａにおける第１めっき膜４ａの最小の厚さは、拡張部６ａ以外の部分６ｂにおける貫通孔６内の第１めっき膜４ａの最小の厚さの５５％以上、９５％以下である。【選択図】図２