Abstract:
A method of etching and a method of regenerating a spent etching solution comprising adding metal particles to a spent etching solution to precipitate the residue metal or metals in the spent etching solution in the form of metal powders, removing the metal powders from the spent etching solution and recovering the metals in the metal powders for future use. The remaining portion of the spent etching solution can then be regenerated to produce a fresh batch of etching solution.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates generally to etching and more specifically to the recover of metals from a spent etching solution.  
       CROSS REFERENCE TO RELATED APPLICATIONS  
       [0002]     None  
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0003]     None  
       REFERENCE TO A MICROFICHE APPENDIX  
       [0004]     None  
       BACKGROUND OF THE INVENTION  
       [0005]     The concept of etching or photochemical machining is well known in the art. Typically an etching solution is selectively applied to an article to remove unwanted material through a process of chemical interaction with the metal. One of the common etching solutions comprises a ferric chloride solution (FeCl 3 ). The ferric chloride etching solution is used to etch a variety of materials including metals that contain iron, copper and nickel. The etching is caused by the oxidative power of iron III ions. As a result of the etching process, the concentration of the nickel II and or the copper II ion increases in the etching solutions while the concentrations of the iron III decreases and the concentrations of the iron II increases. Thus, as the etching process proceeds, the ferric chloride solution (FeCl 3 ) reduces to a ferrous chloride (FeCl 2 ) solution which contains metal ions through the interaction of the ferric chloride with the article being etched. The ferrous chloride solution can be converted back to a ferric chloride (FeCl 3 ) solution through a process of regeneration which leaves a sludge of waste material. Although the ferrous chloride can be converted back into ferric chloride the etching process produces large amounts of waste or spent etching solutions which can contain large amounts of nickel and or copper. Generally, the sludge that remains from the regeneration must be carefully disposed of so as to avoid any adverse environmental impact. It would be preferable if the spent etching solutions could be refined to recover the metals in the spent etching solution. More specifically, If the spent etching solutions contains nickel and copper it would be preferable to recover the nickel and copper from the spent etching solution rather than having to dispose of the spent etching solution with nickel and copper.  
         [0006]     The present invention comprises a process where the metals in the spent etching solution are separated and recovered from the spent etching solution by converting a residue metal, such as copper or nickel, to a metal powder. The metal powder can then be removed from the spent etching solution thereby decreasing the amount of sludge that needs to disposed of as well as allowing one to recover the metals for reuse.  
       SUMMARY OF THE INVENTION  
       [0007]     A method of etching and a method of regenerating a spent etching solution comprising adding metal particles to a spent etching solution to precipitate the residue metal or metals in the spent etching solution in the form of metal powders, removing the metal powders from the spent etching solution and recovering the metals in the metal powder for future use. The remaining portion of the spent etching solution can then be regenerated to produce a fresh batch of etching solution.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]     The FIGURE is a schematic representation of an etching system having an etchant regeneration system that includes apparatus for separating etched metal from a spent etching solution and for regeneration of the spent etching solution to create a fresh batch of etching solution. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0009]     The FIGURE shows an etchant regeneration system  10  comprising a first etching stage wherein an article  11  is subjected to a spray of etching solution  9  from a set of spray nozzles  12  and  13 . The fresh etching solution, which is contained in a container  8 , is directed onto the article  11  though a set of spray nozzles  12  that direct etchant on one side of article  11  and a second set of spray nozzles  13  direct etchant on the other side of article  11 . Although spray etching is shown, other etching techniques such as immersion of the article in the etching solution  9  can be used. The etching solution  9  removes unwanted material from the article, which is then carried away by the spent etching solution  14 . The spent etching solution  14  and the unwanted material is then collected in a container  15 .  
         [0010]     In the etching of metals, a common etchant such as ferric chloride (FeCl 3 ) is used as the etching solution. The removal of the metal from the article leaves a spent etching solution  14  comprising a ferrous chloride solution (FeCl 2 ) containing a reside of metal and metal ions from the etched material. For example, if the article  11  contains copper the spent etching solution  14  contains copper and if the article  11  contains nickel the spent etching solution  14  contains nickel . The metals, which are normally included as part of the sludge, remain therein when the ferrous chloride solution is regenerated to produce a fresh batch of ferric chloride solution.  
         [0011]     The regeneration of the ferrous chloride solution to produce a fresh batch of ferric chloride solution is known in the art. Etchant regeneration methods include the use of sodium chlorate and hydrochloric acid, ozone and hydrochloric acid, electrolysis with hydrochloric acid and use of chlorine gas. A method and system for regeneration of ferric chloride enchant is shown and described more fully in U.S. Pat. No. 5,277,010.  
         [0012]     In the present process the spent etchant solution  14 , which contains metal and or metal ions is transferred, via a conduit to a second container  17 . A pivotally mounted bucket carrier  18  which is suspend by a support  19  carries a number of metal particles  20  which are shown be dumped into the spent etching solution  14  that is located in container  17 . The metal particles comprise iron particles of various shapes and sizes. The particles can be in the form of sheets or wires. In general, it is preferred to have at least one dimension of the particle in the range of a millimeter to a centimeter. The process can be performed at room temperature or can be performed at higher or lower temperatures with the temperature the primary factor in determining the rate of precipitation. The length of time to precipitate out the metal can range from a few minutes to hours depending on the amount of solution as well as the amount of residue metal in the spent etching solution.  
         [0013]     In the present process iron particles  20  are submerged in the spent etching solution. As the iron particles contact the etching solution the metal is precipitated from the spent etching solution in the form of metal powder. For example, with a spent etching solution that contains iron and residue metals such as nickel and copper it has been found that the addition of iron metal particles to the spent etching solution causes the nickel and copper in the etching solution to precipitate out of the spent etching solution in the form of metal powders.  
         [0014]     Once the spent etching solution  14  is subjected to the iron particles the spent etching solution  14  with the precipitate therein is directed to a separator  26  though a conduit  25 . The metal powder can now be removed or separated from the solution with a separator through a process of sedimentation, centrifugation, filtration or similar process.  
         [0015]     In the preferred process the nickel powder is directed from separator  26  to a container  28  thorough a conduit  27  and the copper powder is directed from the separator  26  to a container  30  through a conduit  29 . The copper powder and nickel powder can then be reused in the formation of copper and nickel metals. The spent etching solution, which now has the copper and nickel removed, flows into a container  32  through a conduit  31 .  
         [0016]     The spent etching solution in container  32  can now be regenerated to form a fresh batch of etching solution. For example, with the spent etching solution comprising a ferrous chloride solution a source of chlorine  35  can direct chlorine into the ferrous chloride solution through a conduit  36  to convert the ferrous chloride solution to a ferric chloride etching solution. A conduit  38  and a pump  40  pump the batch of regenerated etching solution to the fresh etching solution  9  contained in container  8 .  
         [0017]     Thus in the present invention the metal iron precipitates nickel and copper from used or spent etching solutions in the form of a metal powder that separates from the iron without forming adhering layers or large inter grown metal deposits. The process is based on the reducing power of metallic iron and it is believed the reactions for nickel and copper can be summarized as follows: Ni 2+ +Fe metal →Ni metal +Fe 2+  and Cu 2+ +Fe metal →Cu metal +Fe 2+  while the residual ferric chloride etching solutions is reduced according to the equation Fe 3+ +Fe metal Δ3Fe 2+ . Thus the reduced solution contains Fe 2+ ions and chloride ions. The solution can be oxidized by chorine to produce a fresh Ferric chloride etching solution for further use.