| 摘要 |
PROBLEM TO BE SOLVED: To allow an invasion of a plating solution into an interior of a via conductor to be prevented even when a dense cover conductor is not printed on a surface of the via conductor of a front layer of the ceramic board. SOLUTION: A surface of the via conductor 13a of the front layer of a low- temperature baked ceramic board is densified by mechanical working such as blasting or the like to form a dense layer 16. Thus, a hermetical sealability of the surface of the conductor 13a is assured. A surface of the layer 16 of the conductor 13a is Ni/Au plated 19 to form a pad 18. At least one of the conductors 13a of the front layer of the board is linearly connected to the via conductor of its lower layer. In this case, even when the conductor 13a of the front layer of the board and the via conductor of its lower layer are not deviated and disposed in a lateral direction like a prior art, since the sealability of the conductor 13a of the front layer of the board can be assured, the invasion of a moisture from the conductor 13a of the front layer into the board can be prevented. |
