Method for plating printed circuit board and printed circuit board using the same

Abstract

A method for plating a printed circuit board, includes placing a substrate, including a through hole, in contact with a plating solution and disposing the substrate to face an electrode; and applying a pulsed current to each surface of the substrate, including applying pulsed currents of opposite polarity to both surfaces of the substrate at least once and applying pulsed forward currents to both surfaces of the substrate at least once, to plate from a middle to an end of the through hole.

What is claimed is: 
     
         1 . A method for plating a printed circuit board, the method comprising:
 placing a substrate, comprising a through hole, in contact with a plating solution and disposing the substrate to face an electrode; and   applying a pulsed current to each surface of the substrate, comprising applying pulsed currents of opposite polarity to both surfaces of the substrate at least once and applying pulsed forward currents to both surfaces of the substrate at least once, to plate from a middle to an end of the through hole.   
     
     
         2 . The method of  claim 1 , wherein a first pulsed current, applied to one surface of the substrate, has a first cycle comprising a period for applying a reverse current, and
 a second pulsed current, applied to the other surface of the substrate, has a second cycle comprising a period of temporal overlap with the period for applying the reverse current of the first pulsed current and a period for applying a forward current.   
     
     
         3 . The method of  claim 2 , wherein a 1-1 period for applying a reverse current and a 1-2 period for applying a forward current occur during the first cycle, and
 a 2-1 period for applying a forward current having a high current density and a 2-2 period for applying a forward current having a current density lower than the 2-1 period occur during the second cycle,   wherein the 1-1 period of the first cycle and the 2-1 period of the second cycle temporally overlap.   
     
     
         4 . The method of  claim 3 , wherein a 1-3 period for applying a forward current having a high current density higher than a current density of the 1-2 period and a 1-4 period for applying a forward current having a current density lower than a current density of the 1-3 period further occur in the first cycle, and
 a 2-3 period for applying a reverse current and a 2-4 period for applying a forward current, each having a current density lower than a current density of the 2-1 period further occur during the second cycle,   wherein the 1-3 period of the first cycle and the 2-3 period of the second cycle temporally overlap.   
     
     
         5 . The method of  claim 1 , wherein the plating solution comprises a plating accelerator and a plating suppressor and the plating suppressor has a molecular weight larger than the plating accelerator,
 the plating accelerator and the plating suppressor are separated from the inner wall of the through hole and the surface of the substrate to which the reverse current is applied when the pulsed currents of opposite polarity are applied to both surfaces of the substrate, and   a density of the plating accelerator is concentrated at a center part of the through hole when the pulsed forward currents are applied to both surfaces of the substrate.