| 摘要 |
PROBLEM TO BE SOLVED: To provide an inspection method, in which the defect of a through hole plating conductor can be easily inspected without destroying a plastic package. SOLUTION: In the inspection method for the thickness of a through hole plating conductor 14, which is formed on the surface of the wall of a through hole 13 on a resin base material 11, of a plastic package 10 covering the through hole plating conductor 14 with solder resist films 17 and 17a by filling the through hole 13, light is radiated from the rear side of the plastic package 10, in which the relation of an inner diameter A after the formation of the through hole plating conductor 14, thickness B of the solder resist films 17 and 17a between the front and rear sides of the plastic package 10 filling the through hole 13 and a permeability (k) of the solder resist films is B>4×A×(1-k) or B<=4×A×(1-k), it is detected whether light is transmitted onto the surface of the through hole 13 or not, and the thickness of the through hole plating conductor 14 is discriminated.
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