Pulse reverse electrolysis of acidic copper electroplating solutions

Abstract

Pulse reverse electrolysis of acid copper solutions is used for applying copper to decorative articles, such as aluminium alloy automotive wheels and plastic parts for automotive use. 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.

What is claimed is:  
     
         1 . A method of plating decorative articles in an acidic copper electroplating bath comprising the steps of: 
 (a) suspending said decorative article in an plating bath comprising copper ions, counter ions, and chloride ions; and    (b) plating said decorative article for a period of time with pulse-reverse current to produce a desired thickness of copper on at least one surface of said decorative article.    
     
     
         2 . The method according to  claim 1 , wherein the counter ion is sulfate.  
     
     
         3 . The method according to  claim 1 , wherein the electroplating bath contains copper ions at a concentration of about 10-50 g/l.  
     
     
         4 . The method according to  claim 1 , wherein the electroplating bath comprises sulphuric acid at a concentration of about 50-250 ml/l.  
     
     
         5 . The method according to  claim 4 , wherein the electroplating bath comprises sulphuric acid at a concentration of about 100-150 ml/l.  
     
     
         6 . The method according to  claim 1 , wherein the electroplating bath comprises chloride ions at a concentration of about 10-500 mg/l.  
     
     
         7 . The method according to  claim 6 , wherein the electroplating bath comprises chloride ions at a concentration of about 50-150 mg/l.  
     
     
         8 . The method according to  claim 1 , wherein the plating bath further comprises a polyether and a divalent sulphur compound.  
     
     
         9 . The method according to  claim 8 , wherein the polyether is present at a concentration of about 50-5000 mg/l.  
     
     
         10 . The method according to  claim 9 , wherein the polyether is present at a concentration of about 300 mg/l.  
     
     
         11 . The method according to  claim 8 , wherein the polyether has a molecular weight between 500 and 100,000.  
     
     
         12 . The method according to  claim 11 , wherein the polyether is polyethyleneglycol.  
     
     
         13 . The method according to  claim 11 , wherein the polyether is an ethylene oxide/propylene oxide co-polymer.  
     
     
         14 . The method according to  claim 8 , wherein the divalent sulphur compound is present in the plating bath at a concentration of about 1-150 mg/l.  
     
     
         15 . The method according to  claim 14 , wherein the divalent sulphur compound is present in the plating bath at a concentration of about 30-50 mg/l.  
     
     
         16 . The method according to  claim 8 , wherein the divalent sulphur compound is mercaptopropanesulphonic acid or an alkali metal salt thereof.  
     
     
         17 . The method according to  claim 8 , wherein the divalent sulphur compound is bis-(propane-3-sulphonic acid)disulphide or an alkali metal salt thereof.  
     
     
         18 . The method according to  claim 8 , wherein the divalent sulphur compound is bis-(ethane-2-sulphuric acid)disulphide or an alkali metal salt thereof.  
     
     
         19 . The method according to  claim 1 , wherein the plating bath further comprises an element selected from the group consisting of brighteners and levellers.  
     
     
         20 . The method according to  claim 8 , wherein the plating bath further comprises an element selected from the group consisting of brighteners and levellers.  
     
     
         21 . The method according to  claim 1 , wherein the pulse plating regime consists of alternating cathodic and anodic pulses.  
     
     
         22 . The method according to  claim 21 , wherein the cathodic pulse time is 5-100 ms.  
     
     
         23 . The method according to  claim 21  wherein the anodic pulse time is 0.1-10 ms.  
     
     
         24 . The method according to  claim 21 , wherein the pulse plating regime further comprises a final cathodic period of extended time.  
     
     
         25 . The method according to  claim 24 , wherein the final cathodic pulse is up to 1 hour.  
     
     
         26 . The method according to  claim 1 , wherein the average applied current density is 0.5-5.0 A/dm 2 .  
     
     
         27 . 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.  
     
     
         28 . The method according to  claim 1 , wherein the thickness ratio of the copper deposited is less than 2.5:1.  
     
     
         29 . A decorative substrate produced in accordance with the process of  claim 1 .  
     
     
         30 . The decorative substrate of  claim 29 , wherein a subsequent coating is applied over the copper layer.  
     
     
         31  An aluminium alloy wheel produced in accordance with the process of  claim 1 .  
     
     
         32 . The aluminium alloy wheel of  claim 31 , wherein a subsequent coating is applied over the copper layer.  
     
     
         33 . A plastic substrate produced in accordance with the process of  claim 1 .  
     
     
         34 . The plastic substrate of  claim 33 , wherein a subsequent coating is applied over the copper layer.