Pulse Reverse Electrolysis of Acidic Copper Electroplating Solutions

Abstract

Pulse reverse electrolysis of acid copper solutions is used for applying copper to printing cylinders, especially gravure printing cylinders. The plating composition generally comprising copper ions, counter ions, chloride ions, a polyalkylene glycol, and a bath-soluble divalent sulfur compound. The benefits include an improved thickness distribution of the copper electrodeposited on the plated article, reduced metal waste, reduced plating times and increased production capacity.

1 .- 25 . (canceled) 
     
     
         26 . A method of manufacturing a printing cylinder comprising a surface in an acidic copper electroplating bath, the method comprising:
 (a) suspending the printing cylinder in a plating bath comprising copper ions, counter ions, chloride ions, a polyalkyleneglycol and a bath-soluble divalent sulfur compound;   (b) rotating the printing cylinder in the plating bath; and   (c) plating said printing cylinder for a period of time with alternating cathodic and anodic pulses to produce a desired thickness of copper on a surface of the printing cylinder,   wherein the cathodic pulse time is about 5 to 100 milliseconds and the anodic pulse time is about 0.1 to 10 milliseconds, and   wherein copper is plated on the surface of the printing cylinder such that the thickness of the copper plate on the surface on the printing cylinder does not vary more than +/−2 microns across said surface without machining.   
     
     
         27 . The method according to  claim 26 , wherein the counter ion is sulfate. 
     
     
         28 . The method according to  claim 27 , wherein the counter ion comprises sulfuric acid at a concentration of about 50-250 g/l. 
     
     
         29 . The method according to  claim 28 , wherein the concentration of sulfuric acid is about 80-140 g/l. 
     
     
         30 . The method according to  claim 26 , wherein the plating bath contains copper ions at a concentration of about 30-70 g/l. 
     
     
         31 . The method according to  claim 26 , wherein the source of copper ions comprises copper sulfate pentahydrate. 
     
     
         32 . The method according to  claim 31 , wherein the copper sulfate pentahydrate is present in the plating bath at a concentration of about 120-180 g/l. 
     
     
         33 . The method according to  claim 26 , wherein the concentration of chloride ions in the plating bath is about 10-500 mg/l. 
     
     
         34 . The method according to  claim 33 , wherein the concentration of chloride ions in the plating bath is about 75-150 mg/l. 
     
     
         35 . The method according to  claim 26 , wherein the concentration of the polyalkyleneglycol in the plating bath is about 50-10,000 mg/l. 
     
     
         36 . The method according to  claim 33 , wherein the concentration of the polyalkyleneglycol in the plating bath is about 500 mg/l. 
     
     
         37 . The method according to  claim 26 , wherein the polyalkyleneglycol has a molecular weight between about 500 and 100,000. 
     
     
         38 . The method according to  claim 35 , wherein the polyalkyleneglycol is polyethyleneglycol. 
     
     
         39 . The method according to  claim 35 , wherein the polyalkyleneglycol is an ethylene oxide/propylene oxide co-polymer. 
     
     
         40 . The method according to  claim 26 , wherein the concentration of the bath-soluble divalent sulfur compound in the plating bath is about 1-150 mg/l. 
     
     
         41 . The method according to  claim 40 , wherein the concentration of the bath-soluble divalent sulfur compound in the plating bath is about 30-50 mg/l. 
     
     
         42 . The method according to  claim 26 , wherein the divalent sulfur compound is selected from the group consisting of mercaptopropanesulfonic acid, bis-(propane-3-sulfonic acid) disulfide, bis-(ethane-2-sulfuric acid) disulfide, and alkali salts thereof. 
     
     
         43 . The method according to  claim 26 , wherein the plating bath further comprises an element selected from the group consisting of wetting agents, brighteners and levellers and one or more of the foregoing. 
     
     
         44 . The method according to  claim 26 , wherein the pulse plating regime further comprises a cathodic period of extended time. 
     
     
         45 . The method according to  claim 44 , wherein the final cathodic pulse is up to about 1 hour. 
     
     
         46 . The method according to  claim 26 , wherein the average applied current density for cathodic and anodic pulses is about 10.0-35.0 A/dm 2 . 
     
     
         47 . The method according to  claim 26 , wherein the current density during the anodic pulse is between 1 and 5 times the current density during the cathodic pulse. 
     
     
         48 . The method according to  claim 26 , wherein a period of time of substantially no current exists between the alternating periods of cathodic and anodic current. 
     
     
         49 . The method according to  claim 26 , wherein the hardness is controlled to within +/−5 HV(50) across the length of the printing cylinder.