Method of monitoring constituents in electroless plating baths
First Claim
1. A method for monitoring the concentrations of constituents present in a solution used in an electroless plating process wherein said 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 annealing and anodic pretreatment and is positioned within said solution containing said constituents, said working electrode being a non-catalytic electrode which comprises a low or moderate hydrogen overvoltage material which is alloyed or mixed with a high overvoltage material;
(b) superimposing a constant ac voltage on said dc potential applied to said working electrode, said ac voltage having a root mean square 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) measure said dc and/or said ac current or a harmonic thereof at one or more reference phase angles with respect to said constant ac voltage between said working electrode and a reference electrode positioned within said solution as said dc potential is varied over said range, said measurement of dc and/or ac current in relation to varying dc potential being expressed as dc and/or ac current spectra which are used to determine and monitor said constituents in said solution.
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Abstract
A method for monitoring the constituents present in an electroless plating bath solution. The method involves measuring ac spectra using a working electrode which has a high hydrogen overvoltage. First, a selected dc potential is applied to a working electrode which has been subjected to pretreatment and which is present in the electroless bath being analyzed. The electrode must have a high hydrogen overvoltage and is preferably an alloy of a low hydrogen overvoltage noble metal and a high overvoltage metal. A constant ac signal is superimposed on the dc potential. The dc potential is then swept over a chosen range at a selected sweep rate. The various constituents in the bath are then monitored by measuring the ac current at one or more reference phase angles with respect to the constant ac signal between the working electrode and a reference electrode as the dc potential is varied. The resulting ac spectra provides a useful measurement of the make-up of the constituents in the electroless plating solution. Regulation of solution temperature to optimize the ac spectra is also disclosed.
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Citations
14 Claims
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1. A method for monitoring the concentrations of constituents present in a solution used in an electroless plating process wherein said constituents affect plating deposit properties, said method comprising the steps of:
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(a) applying a selected dc potential to a working electrode which has been subjected to annealing and anodic pretreatment and is positioned within said solution containing said constituents, said working electrode being a non-catalytic electrode which comprises a low or moderate hydrogen overvoltage material which is alloyed or mixed with a high overvoltage material; (b) superimposing a constant ac voltage on said dc potential applied to said working electrode, said ac voltage having a root mean square 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) measure said dc and/or said ac current or a harmonic thereof at one or more reference phase angles with respect to said constant ac voltage between said working electrode and a reference electrode positioned within said solution as said dc potential is varied over said range, said measurement of dc and/or ac current in relation to varying dc potential being expressed as dc and/or ac current spectra which are used to determine and monitor said constituents in said solution. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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Specification
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- Resources
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Current AssigneeTechnic, Inc.
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Original AssigneeTechnic, Inc.
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InventorsManger, Cheryl, Ludwig, Frank A., Wikiel, Kazimierz
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Primary Examiner(s)Bell, Bruce F.
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Application NumberUS08/587,496Time in Patent Office860 DaysField of Search205/794, 427/304, 427/305, 427/306US Class Current205/794CPC Class CodesG01N 27/48 using polarography, i.e. me...G01N 27/49 Systems involving the deter...
