Process for Electroless Deposition of Metals Using Highly Alkaline Plating Bath

Abstract

A plating process using an electroless plating bath formed from two separate prepared component solutions. The component solutions mixed within 120 hours prior to plating operations, to provide a highly alkaline plating bath solution. One component solution of the two-part plating bath, is provided with a metal salt or source of plating ions, and which is initially kept in a separate solution from the second other prepared component solution. The second component solution contains formaldehyde, and preferably paraformaldehyde, used to reduce the metal salts into the metal to be deposited on a substrate. Each component solution further includes sodium hydroxide in concentrations selected so that when the two solutions are preferably mixed the final plating bath solution has a pH greater than 11.5.

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         22 . A process for electroless plating nickel or a nickel alloy plating metal on a magnesium metal substrate comprising:
 preparing a first bath solution comprising:
 25 to 60 g/L nickel chloride hexahydrate, 
   preparing a second bath solution physically separated from the first bath solution comprising:
 40 to 75 ml/L ethylenediamine, 
 30 to 50 g/L sodium hydroxide, and 
 3 to 8 g/L sodium borohydride, 
 mixing the first and second bath solutions to form a mixed plating bath solution having a pH of at least 12, and
 immersing a substrate in the mixed solution. 
 
   
     
     
         23 . The process of  claim 22 , wherein the plating metal is a Nickel-Boron alloy. 
     
     
         24 . The process of  claim 22 , wherein the mixed solution has a pH of at least 13 and the metal substrate is immersed in the mixed solution for a period of between about 1 and 60 minutes. 
     
     
         25 . The process of  claim 22 , wherein the mixed solution is maintained at a temperature selected at between about 80 and 95° C. during immersion of the substrate therein. 
     
     
         26 . The process of  claim 22 , wherein the first and second bath solutions are mixed in a continuous batch process, wherein the first and second bath solutions are mixed in an approximately 1:1 volumetric ratio. 
     
     
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         37 . A process for electroless plating Nickel-boron plating metal on a magnesium substrate comprising:
 preparing a first bath solution comprising:
 25 to 50 g/L nickel chloride hexahydrate, 
   preparing a second bath solution component physically separate from the first bath solution component comprising:
 50 to 75 ml/L ethylenediamine, 
 30 to 50 g/L sodium hydroxide, and 
 3 to 8 g/L sodium borohydride, 
 mixing the first and second bath solution components in a ratio selected to form a mixed plating bath solution having a pH of at least 13,
 immersing the magnesium substrate in the mixed solution. 
 
   
     
     
         38 . The process of  claim 37 , wherein during immersion of the magnesium substrate, the mixed plating bath is maintained at an operating temperature selected at between about 80° C. and 95° C. 
     
     
         39 . The process of  claim 37 , wherein the magnesium substrate is immersed in the mixed solution for a period of between about 1 and 60 minutes. 
     
     
         40 . The process of  claim 37 , wherein the first bath solution component is physically separated from the second bath solution component for a period of at least 5 hours. 
     
     
         41 . The process as claimed in  claim 40 , wherein the first bath solution component is physically separated from the second bath solution component for a period of at least 72 hours. 
     
     
         42 . The process of  claim 23 , wherein the mixed solution has a pH of at least 13 and the metal substrate is immersed in the mixed solution for a period of between about 1 and 60 minutes. 
     
     
         43 . The process of  claim 24 , wherein the metal substrate is immersed for a period of between about 10 to 30 minutes. 
     
     
         44 . The process of  claim 37 , wherein the ratio is selected to form said plating bath solution having a pH of about 14. 
     
     
         45 . The process of  claim 39 , wherein the magnesium substrate is immersed in the mixed solution for a period of between about 10 to 30 minutes. 
     
     
         46 . The process of  claim 22 , wherein the nickel or nickel alloy plating metal comprises a Nickel-boron plating metal, and said magnesium metal substrate comprises a magnesium substrate comprising:
 the first bath solution comprising:
 25 to 50 g/L of said nickel chloride hexahydrate, 
   the second bath solution comprising:
 50 to 75 ml/L of said ethylenediamine, wherein 
 said step of mixing comprises mixing the first and second bath solution components to form a mixed plating bath solution having a pH of at least 13.