Plural copper-layer treatment of copper foil and article made thereby

Abstract

Copper foil is subjected to a two-step electrochemical copper treatment to improve its bond strength, the first step of said treatment involving the use of a copper and arsenic-containing electrolyte. A treatment involving the use of the aforementioned two-step electrochemical copper pretreatment prior to the application of an electrochemical copper treatment. Treated copper foil and printed circuit boards resulting therefrom.

We claim: 
     
       1. A process for improving the bond strength of copper foil through the electrochemical treatment of a surface thereof comprising said surface to a two-step electrochemical pretreatment prior to the application of said electrochemical treatment, the first step of said pretreatment comprising subjecting said surface to an arsenic and copper-containing electrolyte under conditions such as to electrolytically deposit thereon a first copper layer which increases the bond strength of the raw foil; the second step of said pretreatment comprising subjecting said surface to a copper-containing electrolyte under conditions such as to electrolytically deposit thereon a second copper layer which substantially conforms to the configuration of the first layer and reduces the powder transfer characteristics of said first layer; and then giving said pretreated foil an electrochemical treatment in which said surface is subjeced to a copper-containing electrolyte under conditions such as to electrolytically deposit thereon a third, copper-containing, microcrystalline layer which further increases the bond strength of said foil. 
     
     
       2. A process as defined in claim 1 wherein said electrochemical treatment involves the use of an arsenic and copper-containing electrolyte. 
     
     
       3. A process as defined in claim 2 wherein the copper and arsenic content in the electrolyte in said first step and in said electrochemical treatment are approximately as follows:   ______________________________________                                    
                        Electrochemical                                   
       1st Step         Treatment                                         
______________________________________                                    
Cu (g/l) 10-40              4-10                                          
As (g/l) .03-5              0-.5.                                         
______________________________________                                    
     
     
     
       4. A process as defined in claim 2 wherein the copper and arsenic content in the electrolyte in said first step and in said electrochemical treatment are approximately as follows:   ______________________________________                                    
                        Electrochemical                                   
       1st Step         Treatment                                         
______________________________________                                    
Cu (g/l) 10-40              4-10                                          
As (g/l)  .3-1.5            0-.5.                                         
______________________________________                                    
     
     
     
       5. A process as defined in claim 2 wherein a sufficient amount of arsenic is present in the electrolyte in said first step of said pretreatment to increase the bond strength resulting from said electrochemical treatment over what it would have been had said electrochemical treatment been applied to foil which had not been pretreated. 
     
     
       6. A process as defined in claim 1 wherein approximately 1-4 grams of electrodeposit per square meter of foil surface is deposited during said electrochemical treatment. 
     
     
       7. A process for improving the bond strength of copper foil comprising subjecting a surface of said foil to three electrochemical treatments such as to electrode-posit thereon three copper layers, said three treatments being carried out approximately under the following conditions:   ______________________________________                                    
             Treatment                                                    
                     Treatment Treatment                                  
             No. 1   No. 2     No. 3                                      
______________________________________                                    
Cu (g/l)       10-40     40-120    4-10                                   
H.sub.2 SO.sub.4 (g/l)                                                    
                30-100   30-100    30-100                                 
As (g/l)       .03-5     --        0-.5                                   
Electrolyte Temp-                                                         
                60-120   90-160    70-100                                 
erature (°F.)                                                      
Deposition time (sec.)                                                    
                5-30     5-30      5-30                                   
Cathode current                                                           
               100-300   100-300   50-200                                 
density (ASF).                                                            
______________________________________                                    
     
     
     
       8. A process as defined in claim 7 wherein the conditions for said three treatments are approximately as follows:   ______________________________________                                    
             Treatment                                                    
                     Treatment Treatment                                  
             No. 1   No. 2     No. 3                                      
______________________________________                                    
Cu (g/l)       20-30     60-80     4.5-5.5                                
H.sub.2 SO.sub.4 (g/l)                                                    
                50-100    50-100   50-65                                  
As (g/l)        .3-1.5   --        .15-.3                                 
Electrolyte Temp-                                                         
                70-100   100-140   75-85                                  
erature (°F.)                                                      
Deposition Time                                                           
               10-14      8-12      8-12                                  
(secs.)                                                                   
Cathode current                                                           
               150-300   150-250    50-150                                
Density (ASF).                                                            
______________________________________                                    
     
     
     
       9. A process as defined in claim 7 wherein the conditions for said three treatments are approximately as follows:   ______________________________________                                    
             Treatment                                                    
                     Treatment Treatment                                  
             No. 1   No. 2     No. 3                                      
______________________________________                                    
Cu (g/l)       30        70        5                                      
H.sub.2 SO.sub.4 (g/l)                                                    
               60        60        60                                     
As (g/l)       1.25      --        .25                                    
Electrolyte Temp-                                                         
               75°                                                 
                         120       80                                     
erature (°F.)                                                      
Deposition Time                                                           
               12        12        12                                     
(secs.)                                                                   
Cathode Current                                                           
               160       200       60                                     
Density (ASF).                                                            
______________________________________                                    
     
     
     
       10. A process for improving the bond strength of copper foil through the electrochemical treatment of a surface thereof comprising subjecting said surface to a two-step electrochemical treatment, the first step of said treatment comprising subjecting said surface to an arsenic and copper-containing electrolyte under conditions such as to electrolytically deposit thereon a first copper layer which increases the bond strength of the raw foil; the second step of said treatment comprising subjecting said surface to a copper-containing electrolyte under conditions such as to electrolytically deposit thereon a second copper layer which substantially conforms to the configuration of the first layer and reduces the powder transfer characteristics of said first layer. 
     
     
       11. The product of the process of claim 1. 
     
     
       12. The product of the process of claim 6. 
     
     
       13. The product of the process of claim 2. 
     
     
       14. The product of the process of claim 3. 
     
     
       15. The product of the process of claim 4. 
     
     
       16. The product of the process of claim 5. 
     
     
       17. The product of the process of claim 7. 
     
     
       18. The product of the process of claim 8. 
     
     
       19. The product of the process of claim 9. 
     
     
       20. The product of the process of claim 10. 
     
     
       21. Copper foil having on a face thereof three electrodeposited superposed layers, the layer closest to said face containing arsenic and copper, the intermediate layer being a copper electrodeposit which substantially conforms to the configuration of said closest layer and serves to reduce the powder transfer characteristics of said closest layer; the third outermost layer being copper-containing and microcrystalline, said third layer increasing the bond strength of said foil over and above the bond strength provided by said closest and intermediate layers. 
     
     
       22. Copper foil as defined in claim 21 wherein said third outermost layer is copper-arsenic. 
     
     
       23. A printed circuit board comprised of a dielectric substrate bonded to which is the copper foil of claim 21, the portion of said foil being closest to said substrate being said third layer. 
     
     
       24. A printed circuit board comprised of a dielectric substrate bonded to which is the copper foil of claim 22, the portion of said foil being closest to said substrate being said third layer. .Iadd. 25. A process for improving the bond strength of copper foil through the electrochemical treatment of a surface thereof comprising subjecting said surface to a two-step electrochemical pretreatment prior to the application of said electrochemical treatment, the first step of said pretreatment comprising subjecting said surface to an electrolyte containing (1) copper and (2) arsenic, antimony, bismuth, selenium or tellurium under conditions such as to electrolytically deposit thereon a first copper layer which increases the bond strength of the raw foil; the second step of said pretreatment comprising subjecting said surface to a copper-containing electrolyte under conditions such as to electrolytically deposit thereon a second copper layer which substantially conforms to the configuration of the first layer and reduces the powder transfer characteristics of said first layer; and then giving said pretreated foil an electrochemical treatment in which said surface is subjected to a copper-containing electrolyte under conditions such as to electrolytically deposit thereon a third, copper-containing microcrystalline layer which further increases the bond strength of said foil. .Iaddend..Iadd. 26. A process as defined in claim 25 wherein approximately 1-4 grams of electrodeposit per square meter of foil surface is deposited during said electrochemical treatment. .Iaddend..Iadd. 27. A process as defined in claim 25 wherein said electrochemical treatment involves the use of an electrolyte containing (1) copper and (2) arsenic, antimony, bismuth, selenium or tellurium. .Iaddend..Iadd. 28. A process as defined in claim 27 wherein a sufficient amount of arsenic, antimony, bismuth, selenium or tellurium is present in the electrolyte in said first step of said pretreatment to increase the bond strength resulting from said electrochemical treatment over what it would have been had said electrochemical treatment been applied to foil which had not been pretreated. .Iaddend..Iadd. 29. A process for improving the bond strength of copper foil through the electrochemical treatment of a surface thereof comprising subjecting said surface to a two-step electrochemical treatment, the first step of said treatment comprising subjecting said surface to an electrolyte containing (1) copper and (2) arsenic, antimony, bismuth, selenium or tellurium under conditions such as to electrolytically deposit thereon a first copper layer which increases the bond strength of the raw foil; the second step of said treatment comprising subjecting said surface to a copper-containing electrolyte under conditions such as to electrolytically deposit thereon a second copper layer which substantially conforms to the configuration of the first layer and reduces the powder transfer characteristics of said first layer. .Iaddend..Iadd. 30. The product of the process of claim 25. .Iaddend..Iadd. 31. The product of the process of claim 26. .Iaddend..Iadd. 32. The product of the process of claim 27. .Iaddend..Iadd. 33. The product of the process of claim 28. .Iaddend..Iadd. 34. The product of the process of claim 29. .Iaddend..Iadd. 35. Copper foil having on a face thereof three electrodeposited superposed layers, the layer closest to said face containing (1) copper and (2) arsenic, antimony, bismuth, selenium or tellurium, the intermediate layer being a copper electrodeposit which substantially conforms to the configuration of said closest layer and serves to reduce the powder transfer characteristics of said closest layer; the third outermost layer being copper-containing and microcrystalline, said third layer increasing the bond strength of said foil over and above the bond strength provided by said closest and intermediate layers. .Iaddend..Iadd. 36. Copper foil as defined in claim 35 wherein said third outermost layer also contains arsenic, antimony, bismuth, selenium or tellurium. .Iaddend..Iadd. 37. A printed circuit board comprised of a dielectric substrate bonded to which is the copper foil of claim 35, the portion of said foil being closest to said substrate being said third layer. .Iaddend..Iadd. 38. A printed circuit board comprised of a dielectric substrate bonded to which is the copper foil of claim 36, the portion of said foil being closest to said substrate being said third layer. .Iaddend..Iadd. 39. Copper foil having on a face thereof two electrodeposited superposed layers, the layer closest to said face containing (1) copper and (2) arsenic, antimony, bismuth, selenium or tellurium, the second layer being a copper electrodeposit which substantially conforms to the configuration of said closest layer and serves to reduce the powder transfer characteristics of said closest layer. .Iaddend..Iadd. 40. Copper foil as defined in claim 39 wherein said second layer contains copper and arsenic. .Iaddend..Iadd. 41. A printed circuit board comprised of a dielectric substrate bonded to which is the copper foil of claim 39, the portion of said foil being closest to said substrate being said second layer. .Iaddend. .Iadd. 42. A printed circuit board comprised of a dielectric substrate bonded to which is the copper foil of claim 40, the portion of said foil being closest to said substrate being said second layer. .Iaddend. .Iadd. 43. A process as defined in claim 25 wherein in said first step of said pretreatment the surface is subjected to an electrolyte containing (1) copper and (2) arsenic, antimony or bismuth. .Iaddend..Iadd. 44. A process as defined in claim 27 wherein said electrochemical treatment involves the use of an electrolyte containing (1) copper and (2) arsenic, antimony or bismuth. .Iaddend.