Method for roll-to-roll electroless plating with low dissolved oxygen content

Abstract

A method of electrolessly plating a web of media, including advancing the web of media from an input roll through a pan of plating solution to a take-up roll, wherein a plating substance in the plating solution is plated onto predetermined locations on a surface of the web of media. The plating solution is circulated from a sump to the pan and back to the sump through enclosed pipes, such that plating solution in the enclosed pipes is not exposed to air. An amount of dissolved oxygen in the plating solution is measured, and an inert gas is injected into the plating solution at a rate that is controlled according to the measured amount of dissolved oxygen.

1 . A method of electrolessly plating a web of media, the method comprising:
 advancing the web of media from an input roll through a pan of plating solution to a take-up roll, wherein a plating substance in the plating solution is plated onto predetermined locations on a surface of the web of media as it is advanced through the plating solution in the pan;   circulating the plating solution from a sump to the pan and back to the sump through enclosed pipes, such that plating solution in the enclosed pipes is not exposed to air;   measuring an amount of dissolved oxygen in the plating solution at a sequence of different measurement times separated by specified time intervals, wherein the time interval between subsequent measurement times at a first time is smaller than interval between subsequent measurement times at a later second time; and   injecting an inert gas into the plating solution at a rate that is controlled according to the measured amount of dissolved oxygen.   
     
     
         2 . The method of  claim 1 , wherein injecting the inert gas includes:
 comparing the measured amount of dissolved oxygen in the plating solution to a target range of dissolved oxygen;   increasing the rate of injecting the inert gas if the measured amount of dissolved oxygen is greater than the target range of dissolved oxygen; and   decreasing the rate of injecting the inert gas if the measured amount of dissolved oxygen is less than the target range of dissolved oxygen.   
     
     
         3 . The method of  claim 2 , wherein increasing the rate of injecting the inert gas includes increasing a flow rate of the inert gas through a valve, and wherein decreasing the rate of injecting the inert gas includes decreasing the flow rate of the inert gas through the valve. 
     
     
         4 - 6 . (canceled) 
     
     
         7 . The method of  claim 1 , wherein the step of measuring the amount of dissolved oxygen includes using a motor to controllably lower an oxygen sensor to dip it into the plating solution and then raise the oxygen sensor to remove it from the plating solution. 
     
     
         8 . The method of  claim 1 , wherein the step of injecting the inert gas into the plating solution includes injecting the inert gas into the plating solution outside the sump and the pan to provide an inert-gas-rich plating solution. 
     
     
         9 . The method of  claim 8 , further including delivering the inert-gas-rich plating solution into the sump. 
     
     
         10 . The method of  claim 8 , further including delivering the inert-gas-rich plating solution into the pan. 
     
     
         11 . The method of  claim 8 , further including delivering the inert-gas-rich plating solution into both the sump and the pan. 
     
     
         12 . The method of  claim 11 , wherein the inert gas injected into the plating solution for delivery into the sump is injected at a first rate, and wherein the inert gas injected into the plating solution for delivery into the pan is injected at a second rate that is different from the first rate. 
     
     
         13 . The method of  claim 8 , further including passing the inert-gas-rich plating solution through a device that produces micro-bubbles of inert-gas within the inert-gas-rich plating solution. 
     
     
         14 . The method of  claim 13 , wherein the device includes a pump having a low-pressure inlet into which the inert gas is injected. 
     
     
         15 . The method of  claim 13 , wherein the device includes a filter. 
     
     
         16 . The method of  claim 8 , wherein the inert gas is injected into the plating solution using an injector including:
 a converging tube segment;   a diverging tube segment downstream of the converging tube segment;   a throat formed at a junction of the converging tube segment and the diverging tube segment; and   an inlet for the injecting the inert gas in proximity to the throat.   
     
     
         17 . A method of electrolessly plating a web of media, the method comprising:
 advancing the web of media from an input roll through a pan of plating solution to a take-up roll, wherein a plating substance in the plating solution is plated onto predetermined locations on a surface of the web of media as it is advanced through the plating solution in the pan;   circulating the plating solution from a sump to the pan and back to the sump through enclosed pipes, such that plating solution in the enclosed pipes is not exposed to air;   measuring an amount of dissolved oxygen in the plating solution; and   injecting an inert gas into the plating solution at a rate that is controlled according to the measured amount of dissolved oxygen;   wherein the step of measuring the amount of dissolved oxygen is initiated when a predefined condition is detected.   
     
     
         18 . The method of  claim 17 , wherein detecting the predefined condition includes detecting that a temperature of the plating solution changes by more than a predetermined threshold, detecting a change in a system operating condition, or detecting that the plating substance is plating onto extraneous surfaces other than the predetermined locations on the surface of the web of media. 
     
     
         19 . A method of electrolessly plating a web of media, the method comprising:
 advancing the web of media from an input roll through a pan of plating solution to a take-up roll, wherein a plating substance in the plating solution is plated onto predetermined locations on a surface of the web of media as it is advanced through the plating solution in the pan;   circulating the plating solution from a sump to the pan and back to the sump through enclosed pipes, such that plating solution in the enclosed pipes is not exposed to air;   measuring an amount of dissolved oxygen in the plating solution at a plurality of different times; and   injecting an inert gas into the plating solution at a rate that is controlled according to the measured amount of dissolved oxygen;   wherein the step of measuring the amount of dissolved oxygen at a particular time includes:
 controlling a motor to lower an oxygen sensor to dip it into the plating solution; 
 using the oxygen sensor to measure the amount of dissolved oxygen in the plating solution; and 
 controlling the motor to raise the oxygen sensor to remove it from the plating solution, thereby reducing an amount of plating substance that is plated onto the oxygen sensor between subsequent measurements. 
   
     
     
         20 . The method of  claim 19 , wherein the pan has a pan cover, and wherein the oxygen sensor is lowered into the plating solution and raised out of the plating solution through an opening in the pan cover.