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 . A method of manufacturing a printing cylinder 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; and    (b) plating said printing cylinder for a period of time with alternating cathodic and anodic current to produce a desired thickness of copper on a surface of the printing cylinder.    
     
     
         2 . The method according to  claim 1 , wherein the counter ion is sulfate.  
     
     
         3 . The method according to  claim 2 , wherein the counter ion comprises sulfuric acid at a concentration of about 50-250 g/l.  
     
     
         4 . The method according to  claim 3 , wherein the concentration of sulfuric acid is about 80-140 g/l.  
     
     
         5 . The method according to  claim 1 , wherein the plating bath contains copper ions at a concentration of about 30-70 g/l.  
     
     
         6 . The method according to  claim 1 , wherein the source of copper ions comprises copper sulfate pentahydrate.  
     
     
         7 . The method according to  claim 6 , wherein the copper sulfate pentahydrate is present in the plating bath at a concentration of about 120-180 g/l.  
     
     
         8 . The method according to  claim 1 , wherein the concentration of chloride ions in the plating bath is about 10-500 mg/l.  
     
     
         9 . The method according to  claim 8 , wherein the concentration of chloride ions in the plating bath is about 75-150 mg/l.  
     
     
         10 . The method according to  claim 1 , wherein the concentration of the polyalkyleneglycol in the plating bath is about 50-10,000 mg/l.  
     
     
         11 . The method according to  claim 8 , wherein the concentration of the polyalkyleneglycol in the plating bath is about 500 mg/l.  
     
     
         12 . The method according to  claim 1 , wherein the polyalkyleneglycol has a molecular weight between about 500 and 100,000.  
     
     
         13 . The method according to  claim 10 , wherein the polyalkyleneglycol is polyethyleneglycol.  
     
     
         14 . The method according to  claim 10 , wherein the polyalkyleneglycol is an ethylene oxide/propylene oxide co-polymer.  
     
     
         15 . The method according to  claim 1 , wherein the concentration of the bath-soluble divalent sulfur compound in the plating bath is about 1-150 mg/l.  
     
     
         16 . The method according to  claim 15 , wherein the concentration of the bath-soluble divalent sulfur compound in the plating bath is about 30-50 mg/l.  
     
     
         17 . The method according to  claim 1 , 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.  
     
     
         18 . The method according to  claim 1 , wherein the plating bath further comprises an element selected from the group consisting of wetting agents, brighteners and levellers, other known copper deposit modifiers, and one or more of the foregoing.  
     
     
         19 . The method according to  claim 1 , wherein the cathodic pulse time is about 5-100 milliseconds and the anodic pulse time is about 0.1 to 10 milliseconds.  
     
     
         20 . The method according to  claim 19 , wherein the pulse plating regime further comprises a cathodic period of extended time.  
     
     
         21 . The method according to  claim 20 , wherein the final cathodic pulse is up to about 1 hour.  
     
     
         22 . The method according to  claim 1 , wherein the average applied current density for cathodic and anodic pulses is about 10.0-35.0 A/dm 2 .  
     
     
         23 . The method according to  claim 1 , wherein the current density during the anodic pulse is between 1 and 5 times the current density during the cathodic pulse.  
     
     
         24 . A gravure printing cylinder produced in accordance with the process of  claim 1 .  
     
     
         25 . The method according to  claim 1  wherein a period of time of substantially no current exists between the alternating periods of cathodic and anodic current.