Electrolysis: processes – compositions used therein – and methods – Electrolytic coating – Involving measuring – analyzing – or testing
Reexamination Certificate
2002-12-06
2004-07-06
Koehler, Robert R. (Department: 1775)
Electrolysis: processes, compositions used therein, and methods
Electrolytic coating
Involving measuring, analyzing, or testing
C205S775000
Reexamination Certificate
active
06758955
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to determination of additives in metal plating baths, and more specifically to Pulsed Cyclic Galvanostatic Analysis (PCGA) of additive concentration in metal plating solutions.
2. Background of the Invention
The PCGA determination of additive concentration in metal plating baths involves the plating of the metal onto a test electrode from a sample metal plating solution.
Typically, the test electrode is cyclically plated and stripped multiple times for each quantity measured. Each plating/measurement cycle comprises the following steps:
Clean—the test electrode surface is thoroughly cleaned electrochemically or chemically using acid bath, followed by flushing with water or acid bath,
Equilibrate—the test electrode and a reference electrode are exposed to the metal plating solution and allowed to reach an equilibrium state,
Plate—metal element is electroplated onto the test electrode either at constant current, and electroplating potential between the test and reference electrodes is monitored and recorded, and
Strip—the metal deposition is removed, e.g., by reversal of the plating current flow and/or exposure to an acid bath.
These four steps must be repeated for each plating/measuring cycle.
The plating is usually conducted after various sample solution preparation steps, in which the sample metal plating solution to be tested is conditioned for optimal measurement results. Such sample solution preparation steps include, for example, dilution of highly concentrated samples, addition of excessive suppressor for amplifying the accelerator responses, and introduction of complexing agent for forming colored complexes with certain additives in the sample solution.
For most PCGA analysis, the solution preparation steps are conducted right after the cleaning step, and before the test electrode is exposed to the conditioned metal plating solution for establishing the equilibrium state, as shown in FIG.
1
A. In some instances, the solution preparation steps are conducted right after the stripping step of a previous plating-measuring cycle, either before or concurrently with the cleaning step, as shown in FIG.
1
B.
During the solution preparation, the stripped or naked test electrode is either (1) exposed to the air, waiting to be cleaned, or (2) if already cleaned, it is usually submerged in a base solution, waiting to be contacted with the conditioned metal plating solution for establishing the equilibrium state.
In the former case, the naked test electrode is vulnerable to contamination while exposed to the air. In the latter case, since the time required for solution preparation varies significantly across different types of sample solutions, the duration when such test electrode is submerged in the base solution varies accordingly, which in effect changes the time required for the test electrode to reach equilibrium state.
It would therefore be a significant advance in the art, and is accordingly an object of the present invention, to minimize the variation of equilibration time between individual plating/stripping cycles and to protect the test electrode against potential contamination during the solution preparation step.
Moreover, conventional PCGA methods utilize calibration measurements for quick determination of the additive concentration in the sample metal plating solutions. The calibration measurements take place immediately after background measurement of the base solution, by adding the calibration solutions into the base solution, while the test electrode is continuously submerged in the base solution, without being exposed to the air at any time.
However, the sample measurement is carried out after previously tested solution (for example, calibration solution) is emptied from the analytical cell, and fresh base solution and sample solution are filled into the analytical cell.. During emptying and filling steps, the test electrode is exposed to the air, which causes the measured additive responses to appear “sluggish,” and the time required for the test electrode to reach the equilibrium state becomes longer.
It is another object of the invention to provide new measurement protocols that minimize the differences between the calibration measurement conditions and the sample measurement conditions and thus increase the measurement accuracy.
Other objects and advantages will be more fully apparent from the ensuing disclosure and appended claims.
SUMMARY OF THE INVENTION
The present invention relates in one aspect to a method for measuring electroplating potentials of metal plating solutions, comprising the steps of:
(a) providing a measuring apparatus comprising a reference electrode, a test electrode, and electrical potential measuring circuitry electrically coupled between such reference electrode and the test electrode for measuring electrical potential therebetween, wherein the test electrode is coated by a metal layer previously deposited thereon;
(b) preparing a metal plating solution for measurement;
(c) stripping the metal layer from the test electrode and cleaning the test electrode;
(d) contacting the test electrode with the prepared metal plating solution, allowing the test electrode to come to an equilibrium state in the prepared metal plating solution;
(e) depositing metal onto the test electrode from the prepared metal plating solution, by electroplating at a constant or known current density; and
(f) measuring and recording electroplating potential between the reference electrode and the test electrode during the electroplating process;
(g) optionally, repeating steps (b)-(f) for each metal plating solution to be measured.
The present invention in another aspect relates to a calibration method for determining concentration of a component of interest in a sample metal plating solution, comprising the steps of:
(a) preparing a base metal plating solution that contains all components of the sample metal plating solution, except the component of interest, or optionally to which has been added a known volume of the component of interest;
(b) preparing a plurality of calibration solutions, each of which contains the component of interest in a distinct, known concentration;
(c) performing a first background measurement, by measuring electroplating potential of a first volume of the base metal plating solution;
(d) successively adding the calibration solutions into the first volume of the base metal plating solution to form a base/calibration mixture, while measuring electroplating potentials of the base/calibration mixture after each addition of said calibration solutions;
(e) constructing a calibration curve, by plotting the electroplating potentials measured in steps (c) and (d) as a function of the concentration of the component of interest;
(f) performing a second background measurement, by measuring electroplating potential of a second volume of the base metal plating solution;
(g) adding the sample metal plating solution into the second volume of the base metal plating solution to form a base/sample mixture, and measuring electroplating potential of the base/sample mixture;
(h) determining the concentration of the component of interest in the sample metal plating solution, based on the calibration curve constructed in step (e) and the electroplating potential measured in step (f) and (g).
The present invention in another aspect relates to a calibration method for determining concentration of a component of interest in a sample metal plating solution, comprising the steps of:
(a) preparing a base metal plating solution that contains all components of the sample metal plating solution, except the component of interest, or optionally to which has been added a known volume of the component of interest;
(b) preparing a single calibration solution, containing the component of interest in a distinct, known concentration, wherein the amount of concentration of component in the calibration solution is equal to a theoretical concentration of the component of interest in th
Advanced Technology & Materials Inc.
Chappuis Margaret
Hultquist Steven J.
Koehler Robert R.
LandOfFree
Methods for determination of additive concentration in metal... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Methods for determination of additive concentration in metal..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Methods for determination of additive concentration in metal... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3213746