PURPOSE: To cause a plating layer to be biasedly formed only in the thickness direction of a pattern wiring by giving a specific value to the composition of the plating sulution at the time of performing the wiring reinforcement of the wiring circuit, thereby increasing the plating current density from the beginning of the plating to the ending of the plating.
CONSTITUTION: When an electrolytic plating is performed, a wiring substrate 1 on which etching layers 4 are formed is dipped in a plating both 6 as the cathode, and a copper plate 7 is dipped as the anode. The copper sulfate concentration of a plating solution 9 in the plating bath is made to fall in the range of saturation concentration 100g/l∼, that it, saturation concentration 25g/l∼ as the copper concentration. And the current density for the electrolyte plating is changed stepwise or continuously within the range of 5∼60A/dm2. Particularly, it is increased multistepwise or continuously from the beginning of the plating to the ending of the plating so that the plating current density at the beginning of the plating is 5∼15A/dm2 and the plating current density at the end of the plating is 35∼60A/dm2.
OSAWA KENJI
TOKURA KUNIHIKO
