Electrochemical etching and polishing of conductive substrates

Abstract

A method for electrochemically etching a metal layer through an etch-resist layer pattern using a non-active electrolyte solution is described. The method is particularly useful in fabrication of advanced fuel delivery systems for land-based power generation turbines and aerospace turbine engines; of components for advanced thermal management in aerospace electronic devices and in cooling channels; of stents used in medicine; and of microchannels for sensors, chemical reactors, and dialysis and the like. In one embodiment of the invention the metal layer is copper and the non-active electrolyte solution is a mixture of sodium nitrate and sodium chloride and a pulse electric current is employed to accomplish the electrochemical etching.

1 . A method for etching a conductive substrate, comprising:
 (a) providing a conductive substrate with an etch-resist layer pattern deposited on said conductive substrate resulting in spaces defining an exposed part of the conductive substrate;   (b) providing a counterelectrode;   (c) interposing a non-active electrolyte solution between and in contact with said conductive substrate and said counterelectrode;   (d) applying an electric current between said conductive substrate and said counterelectrode and maintaining said conductive substrate predominantly anodic with respect to said counterelectrode; and   (e) etching said exposed part of the conductive substrate electrochemically thereby forming an etched pattern from said etch-resist layer pattern.   
     
     
         2 . The method of  claim 1  wherein said conductive substrate is copper, titanium, 440C stainless steel, gold, silver, or nickel. 
     
     
         3 . The method of  claim 1  wherein said non-active electrolyte solution is an electrolyte solution selected from the group consisting of sodium nitrate, sodium chloride, and a mixture of sodium nitrate and sodium chloride. 
     
     
         4 . The method of  claim 1  wherein said electric current is a pulse/pulse reverse electric current comprising an anodic on-time and a cathodic on-time. 
     
     
         5 . The method of  claim 4  wherein said pulse/pulse reverse electric current further comprises an off-time interspersed after said anodic on-time and before said cathodic on-time. 
     
     
         6 . The method of  claim 4  wherein said pulse/pulse reverse electric current further comprises an off-time interspersed after said cathodic on-time and before said anodic off-time. 
     
     
         7 . The method of  claim 4  wherein said pulse/pulse reverse electric current further comprises a first off-time interspersed after said anodic on-time and an second off-time interspersed before said cathodic on-time. 
     
     
         8 . The method of  claim 1  wherein said electric current is a pulsed electric current consisting of an anodic on-time and an off-time. 
     
     
         9 . The method of  claim 8  wherein said anodic on-time ranges from about 10 microseconds to about 100 milliseconds. 
     
     
         10 . The method of  claim 8  wherein said anodic on-time ranges from about 50 microseconds to about 50 milliseconds. 
     
     
         11 . The method of  claim 8  wherein said anodic on-time ranges from about 100 microseconds to about 10 milliseconds. 
     
     
         12 . The method of  claim 8  wherein said off-time ranges from about 100 milliseconds to about 10 microseconds. 
     
     
         13 . The method of  claim 8  wherein said off-time ranges from about 50 milliseconds to about 50 microseconds. 
     
     
         14 . The method of  claim 8  wherein said off-time ranges from about 10 milliseconds to about 100 microseconds. 
     
     
         15 . The method of  claim 8  wherein said pulsed electric current has an anodic voltage amplitude wherein said anodic voltage amplitude ranges from about 1 to about 20 volts. 
     
     
         16 . The method of  claim 8  wherein said pulsed electric current has an anodic voltage amplitude wherein said anodic voltage amplitude ranges from about 2.5 to about 10 volts. 
     
     
         17 . The method of  claims 4  wherein an electrodynamic boundary layer conformal to said spaces in said etch-resist layer pattern is formed. 
     
     
         18 . The method of  claim 8  wherein an electrodynamic boundary layer conformal to said spaces in said etch-resist layer pattern is formed. 
     
     
         19 . A process for removing metal from a metal substrate comprising:
 (a) providing a metal substrate;   (b) providing a counterelectrode;   (c) interposing a non-active electrolyte solution between and in contact with said substrate and said counterelectrode; and   (d) applying a pulse/pulse reverse electric current comprising an anodic on-time and a cathodic on-time electric current between said substrate and said counterelectrode and maintaining said substrate predominantly anodic with respect to said counterelectrode thereby removing metal from metal clad substrate and forming an etched pattern.   
     
     
         20 . The method of  claim 19  wherein said metal is selected from the group consisting of copper, gold, silver, nickel and combinations thereof. 
     
     
         21 . The method of  claim 20  wherein said electrolyte solution is selected from the group consisting of sodium nitrate, sodium chloride, and mixtures of sodium nitrate and sodium chloride. 
     
     
         22 . The method of  claim 20  further comprising providing an etch-resist material wherein said etch-resist material covers a portion of the metal substrate thereby forming exposed portions and covered portions of said metal and said exposed portions of said metal are removed. 
     
     
         23 . The method of  claim 22  wherein said covered portions of said metal are retained and form a pattern on said substrate. 
     
     
         24 . A process for forming etch patterns on a metal substrate comprising:
 (a) providing a metal substrate having a predetermined pattern of covered metal portions and exposed metal portions;   (b) providing a counterelectrode;   (c) interposing a non-active electrolyte solution between and in contact with said substrate and said counterelectrode; and   (d) applying an electric current between said substrate and said counterelectrode and maintaining said substrate predominantly anodic with respect to said counterelectrode thereby removing the exposed metal portions from the metal substrate to form an etch pattern.   
     
     
         25 . The method of  claim 24  wherein said metal is selected from the group consisting of copper, gold, silver, nickel and combinations thereof. 
     
     
         26 . The method of  claim 25  wherein said electrolyte solution is selected from the group consisting of sodium nitrate, sodium chloride, and mixtures of sodium nitrate and sodium chloride. 
     
     
         27 . The method of  claim 25  wherein said electric current is a pulse/pulse reverse electric current comprising an anodic on-time and a cathodic on-time. 
     
     
         28 . The method of  claim 1  wherein the electric voltage and current are such that the dissolution of the metal from the surface of the substrate is diffusion limited.