Analysis method

Abstract

Analytical methods are disclosed for determining the quantity of organic components in a bath. The analytical methods work over a broad concentration range of organic components and are sensitive in measuring organic bath components at low concentrations.

1 . A method of determining a quantity of organic component in a bath comprising: 
 a) obtaining a plurality of bath samples each containing a known and different quantity of an organic component;    b) passing a working electrode in the bath sample through a sequence comprising galvanostatic steps, voltammetric steps by cycles or pulses, or open circuit steps or combinations thereof and the sequence comprises a surface optimization step;    c) preparing a calibration curve by plotting the charge passed during a metal plating or metal stripping step of the sequence versus the concentration of the organic component being sought;    d) obtaining a bath sample comprising an unknown quantity of the organic component and passing the working electrode through the bath using the aforesaid predetermined sequence of steps;    e) measuring the charge passed during the metal plating or the metal stripping step for the bath sample comprising the unknown quantity of the organic component; and    f) comparing the result obtained in e) to the results obtained in c) to determine the amount of the organic component present in the bath sample containing the unknown quantity of the organic component.    
   
   
       2 . The method of  claim 1 , wherein the surface optimization step includes an applied potential sufficient to remove residual halide from the working electrode.  
   
   
       3 . The method of  claim 2 , wherein the applied potential for the surface optimization step ranges from 2 volts to 0 volts.  
   
   
       4 . The method of  claim 1 , wherein the surface optimization step is applied to the working electrode as a rate of from 50 mV/sec to 150 mV/sec.  
   
   
       5 . The method of  claim 1 , wherein the surface optimization step is applied to the working electrode for less than 20 seconds.  
   
   
       6 . The method of  claim 1 , wherein the working electrode comprises a noble metal.  
   
   
       7 . The method of  claim 1 , wherein the working electrode comprises a non-noble metal.  
   
   
       8 . The method of  claim 1 , wherein the bath is an electroplating bath for depositing copper, nickel, chromium, zinc, tin, lead, gold, silver, or cadmium on a substrate.  
   
   
       9 . A method for determining an amount of brightener in a bath comprising: 
 a) obtaining a plurality of baths each bath comprising a known and different quantity of the brightener and where the quantity of the brightener in each bath differs from the quantity in the other baths;    b) for each bath, providing a counter electrode, a cleaned working electrode and a reference electrode immersed in the bath, and carrying out a predetermined sequence of steps by sweeping the working electrode at a predetermined rate through a plurality of sequences comprising galvanostatic, voltammetric, or open circuit steps or combinations thereof until a steady state is obtained, the steps comprise: 
 1. optimizing the surface of the working electrode;  
 2. plating metal ions on the working electrode for a time sufficient to measure plating current;  
 3. stripping at a potential and for a period of time sufficient to remove the metal ions plated in step 2 and measuring the stripping current; and  
   c) for each bath, preparing a calibration curve of amount of charge passed in step 2 or 3 above vs. organic component concentration;    d) obtaining a plating bath sample having an unknown quantity of organic component, placing the electrodes in the bath and performing the aforesaid predetermined sequence of steps; and    e) comparing the results in step d) to those obtained in c) to determine the amount of the organic component present in the unknown sample.    
   
   
       10 . A method for determining an amount of brightener in a bath comprising: 
 a) obtaining a plurality of bath samples, where each bath sample has a known and different quantity of the brightener and where the quantity of the brightener in each bath sample differs from the quantity in the other bath samples;    b) pulsing in each of the bath samples an inert, working electrode at a predetermined rate through a sequence comprising galvanostatic, voltammetric, or open circuit steps, or combinations thereof, each of the sequences comprise a surface optimization range, a metal plating range, a metal stripping range, a cleaning range, and an equlibration range for each of the bath samples of the plurality of bath samples;    c) measuring the charge passed during the metal plating range or the metal stripping range of the cycle for each of the bath samples to obtain a correlation between a quantity of brightener and the charge passed during the metal plating range or the metal stripping range, and preparing a calibration curve of charge passed vs. organic component concentration;    d) obtaining a bath samples comprising an unknown quantity of organic component;    e) pulsing for the unknown bath samples an inert, working electrode at the predetermined rate through sequences comprising galvanostatic, voltammetric, or open circuit steps or combinations thereof until a condition of steady state is obtained, each sequence comprises a surface optimization range, a metal plating range, a metal stripping range, a cleaning range and an equilibration range for the bath samples comprising an unknown quantity of brightener;    f) measuring the charge passed during the metal plating range or the metal stripping range for the bath samples comprising the unknown quantity of organic component; and    g) choosing from the correlation a quantity of brightener which corresponds to the charge passed for the bath samples comprising the unknown quantity of the organic component.