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Method of monitoring trace constituents in plating baths

  • US 4,631,116 A
  • Filed: 06/05/1985
  • Issued: 12/23/1986
  • Est. Priority Date: 06/05/1985
  • Status: Expired due to Term
First Claim
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1. A method for monitoring the minor constituents present in a solution used in a plating process wherein said minor constituents affect plating deposit properties, said method comprising the steps of:

  • (a) applying a selected dc potential to a working electrode which has been subjected to pretreatment and is positioned with said solution containing said minor constituents;

    (b) superimposing a constant ac signal on said dc potential applied to said working electrode, said ac signal having a peak to peak potential and a frequency and producing an ac current;

    (c) varying said dc potential at a chosen sweep rate over a chosen range; and

    (d) measuring said ac current at one or more phase angles with respect to said constant ac signal between said working electrode and a counter electrode positioned within said solution as said dc potential is varied over said range, said measurement of ac current in relation to varying dc potential being expressed as an ac current spectra wherein the improvement comprises varying in combination each parameter comprising said peak to peak potential of said ac signal, said frequency of said ac signal, said sweep rate of said dc potential, said range of dc potential, said one or more phase angles, and said pretreatment of said working electrode, to determine the specific value of each said parameter which, when taken in combination with the remaining said parameters, provides maximum spectra detail in said ac current spectra to determine and monitor said minor constituents in said solution which affect said plating deposit properties.

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