Method and apparatus for improving interfacial chemical reactions in electroless depositions of metals

Abstract

A method and apparatus for improving interfacial chemical reactions in electroless depositions of metals, in which the substrate to be plated is pre-heated prior to its immersion in the various processing solutions that require elevated temperatures, and especially before immersion in the electroless plating solution. The pre-heating is carried out to a temperature that is needed to bring about the desired chemical reaction at the substrate-solution interface, allowing the bath of that process step to operate significantly below the temperature that would have been needed if the panel had not been pre-heated, and below the solution temperature of current practice. According to another aspect of the present invention, the electroless plating apparatus for plating a workpiece operates in a vertical mode and it comprises a heating station, with the panel to be plated returning to the heating station as dictated by the temperature required for a given process step. Alternatively, the heating station is incorporated into the hoist system of such apparatus. In still another aspect of the present invention, the electroless plating apparatus operates in a horizontal mode and comprises at least one heating station.

I claim:  
     
         1 . A method for improving interfacial chemical reactions in electroless depostion of metals on the surface of a workpiece using an electroless plating solution in an electroless plating bath, said method comprising pre-heating the workpiece, prior to immersion thereof in the electroless plating solution, to a temperature approximately equal to or above the operating temperature of the electroless plating bath.  
     
     
         2 . The method of  claim 1 , said method further comprising the step of heating the surface of the workpiece prior to immersion in a processing solution, said heating being such that the workpiece is heated to a temperature approximately equal to or above the temperature of the processing solution.  
     
     
         3 . The method of  claim 1  wherein part of the surface of a workpiece is non-metallic.  
     
     
         4 . The method of  claim 1  wherein the workpiece is flat.  
     
     
         5 . The method of  claim 1  wherein the workpiece is a copper-clad polymer.  
     
     
         6 . The method of  claim 5 , wherein said copper-clad polymer comprises holes.  
     
     
         7 . The method of  claim 5  wherein said polymer is epoxy.  
     
     
         8 . An article produced by the method of  claim 1 .  
     
     
         9 . A PCB produced by the method of  claim 1 .  
     
     
         10 . A hoist-operated vertically operated plating apparatus, wherein a workpiece to be plated is mounted on vertical jigs and is carried by a hoist through a sequence of processing solutions and rinses, said apparatus comprising a heating station wherein the workpiece to be plated is preheated prior to immersion in the processing solutions to a temperature approximately equal to or above the operating temperature of the processing solutions.  
     
     
         11 . The apparatus of  claim 10 , wherein said heating station is incorporated in the hoist.  
     
     
         12 . The apparatus of  claim 10  wherein the preheating temperature for each process solution is controlled by software.  
     
     
         13 . The apparatus of  claim 10  comprising an electroless plating station.  
     
     
         14 . The apparatus of  claim 10  comprising a palladium-bearing activator station.  
     
     
         15 . A horizontally operated plating apparatus wherein a workpiece to be plated is placed on a conveyor that travels and carries the workpiece through a sequence of process modules in which liquid is applied to said workpiece by at least one of spraying and submersion comprising a heating station wherein the workpiece to be plated is heated prior to being conveyed into said process modules to a temperature approximately equal to or above the operating temperature of the process solutions.  
     
     
         16 . The apparatus of  claim 15  wherein the preheating temperature for each process solution is controlled by software.  
     
     
         17 . The apparatus of  claim 15  comprising an electroless plating station.  
     
     
         18 . The apparatus of  claim 12  comprising a palladium-bearing activator station.  
     
     
         19 . The method of  claim 1  wherein the workpiece to be plated is pre-heated in a suitable chemical solution to a predetermined temperature, prior to immersion thereof in the electroless plating bath.  
     
     
         20 . The method of  claim 19  wherein said chemical solution is an alkaline aqueous accelerator.  
     
     
         21 . The method of  claim 19  wherein said predetermined temperature is at least 5° C. above ambient.  
     
     
         22 . The method of  claim 19 , wherein said workpiece is immersed in the electroless plating bath without being exposed to a water rinse.  
     
     
         23 . A method for improving solid/solution interfacial reactions in a surface chemical process, said method comprising pre-heating a workpiece, prior to immersion thereof in a solution, to a temperature approximately equal to or above the operating temperature of that solution.