Nguyet Trong Phan

US Patent:

52981312, Mar 29, 1994

Filed:

May 28, 1993

Appl. No.:

8/068030

Inventors:

Bruce M. Eliash - Los Angeles CA
Frank A. Ludwig - Rancho Palos Verdes CA
Nguyet H. Phan - Los Angeles CA
Vilambi N. Reddy - Jamaica NY

Assignee:

Hughes Aircraft Company - Los Angeles CA

International Classification:

G01N 2726

US Classification:

2041531

Abstract:

A method of monitoring in-tank and on-line metal ion content within a plating bath. The method involves the steps of applying a pretreatment signal to a sensing electrode positioned within the plating bath, applying a sweep signal to the pretreated sensing electrode, and measuring the voltammetric peak current of the resultant response signal. The voltammetric peak current is proportional to the metal ion content of the plating bath. The method complements and is easily integrated with known voltammetric techniques for analysis of trace and major constituents, and is thus an integral part of an efficient overall plating bath analysis system.

US Patent:

52870600, Feb 15, 1994

Filed:

Nov 17, 1992

Appl. No.:

7/977389

Inventors:

Vilambi N. Reddy - Lakewood CA
Bruce M. Eliash - Los Angeles CA
Frank A. Ludwig - Rancho Palos Verdes CA
Nguyet H. Phan - Los Angeles CA

Assignee:

Hughes Aircraft Company - Los Angeles CA

International Classification:

G01N 3318

US Classification:

324439

Abstract:

A conductivity sensor adapted for use in the conductimetric analysis of liquids includes a pair of conductivity electrodes incorporated into a conductivity cell assembly having a liquid flow control chamber, sensing chamber, and liquid exit chamber. Liquids to be measured are pumped into the liquid flow control chamber, where any turbulence in the liquid is dampened. The non-turbulent liquid is passed from the liquid flow control chamber to the sensing chamber, where the conductivity of the liquid is determined. The sensing chamber is adapted for changing the height of a column of liquid between the pair of conductivity electrodes in order to vary the cell constant of the sensor. The non-turbulent liquid is passed from the sensing chamber to the liquid exit chamber, where it exits the sensor. The sensor is well-suited for use in measuring conductivities of plating bath solutions and monitoring concentrations of major constituents of plating bath solutions.

US Patent:

52961249, Mar 22, 1994

Filed:

Nov 10, 1992

Appl. No.:

7/974650

Inventors:

Bruce M. Eliash - Los Angeles CA
Vilambi N. R. K. Reddy - Lakewood CA
Frank A. Ludwig - Rancho Palos Verdes CA
Nguyet H. Phan - Los Angeles CA

Assignee:

Hughes Aircraft Company - Los Angeles CA

International Classification:

G01N 2726

US Classification:

204402

Abstract:

A method of forming a reference electrode having a continuously stable reference voltage and particularly well-suited for use in an in-tank electrochemical sensor. The method utilizes an inert substrate and a counter electrode, both immersed in electroplating fluid. Current is passed between the inert substrate and the counter electrode to strip and subsequently replate the inert substrate, which then serves as the reference electrode. The steps of stripping and replating the reference electrode are periodically repeated to maintain the stability of the reference electrode voltage.

US Patent:

53207246, Jun 14, 1994

Filed:

Nov 17, 1992

Appl. No.:

7/977344

Inventors:

Frank A. Ludwig - Rancho Palos Verdes CA
Bruce M. Eliash - Los Angeles CA
Nguyet H. Phan - Los Angeles CA
Vilambi N. R. K. Reddy - Lakewood CA

Assignee:

Hughes Aircraft Company - Los Angeles CA

International Classification:

G01N 2726

US Classification:

2041531

Abstract:

A method of monitoring a plating bath which combines ac and dc voltammetry to accurately measure major and trace constituent concentrations. The method involves applying both ac and dc voltammetric signals to a pretreated electrode in contact with the plating bath solution, measuring the ac and dc response current spectra, and comparing the resultant spectra to determine which provides maximum spectral detail for monitoring particular constituents with minimum interference from other constituents. Then, the ac and dc response current spectra are each used to monitor the particular constituents for which each provides the best accuracy. The method complements and is easily integrated with known voltammetric techniques and equipment.

US Patent:

53244001, Jun 28, 1994

Filed:

Dec 4, 1992

Appl. No.:

7/986846

Inventors:

Bruce M. Eliash - Los Angeles CA
Nguyet H. Phan - Los Angeles CA
Frank A. Ludwig - Rancho Palos Verdes CA
Vilambi N. Reddy - Lakewood CA

Assignee:

Hughes Aircraft Company - Los Angeles CA

International Classification:

G01N 2726

US Classification:

2041531

Abstract:

A method of preconditioning an electrode for use in a plating bath monitoring process. The method involves applying at least one anodic signal to an electrode in contact with the plating bath solution in order to yield a reproducibly clean and stabilized electrode surface, and then applying a plating signal to deposit a layer of metal on the anodically treated electrode. The resultant preconditioned electrode improves the accuracy and precision of subsequent voltammetric monitoring measurements for a variety of different plating baths. The method is easily integrated with and thereby enhances the capabilities of known voltammetric plating bath monitoring processes.

US Patent:

52981320, Mar 29, 1994

Filed:

Mar 25, 1993

Appl. No.:

8/037159

Inventors:

Vilambi N. R. K. Reddy - Lakewood CA
Bruce M. Eliash - Los Angeles CA
Frank A. Ludwig - Rancho Palos Verdes CA
Nguyet H. Phan - Los Angeles CA

Assignee:

Hughes Aircraft Company - Los Angeles CA

International Classification:

G01N 2726

US Classification:

2041531

Abstract:

A method for monitoring the status of a plating bath purification treatment cycle. The method involves applying a swept dc measurement signal to a pretreated electrode which is in contact with the plating solution, and monitoring the resultant response current signal. The electrode potential corresponding to the peak current density in the cathodic sweep of the response current signal provides an accurate indication of the status of the purification treatment cycle. The method tracks the progress of the purification process thereby ensuring the optimal termination points for the treatment process. The method can be used in conjunction with voltammetric plating bath analysis methods and equipment, as part of an overall plating bath monitoring and control system.

US Patent:

53363809, Aug 9, 1994

Filed:

Mar 25, 1993

Appl. No.:

8/037158

Inventors:

Nguyet H. Phan - Los Angeles CA
Vilambi N. R. K. Reddy - Lakewood CA
Frank A. Ludwig - Rancho Palos Verdes CA
Bruce M. Eliash - Los Angeles CA

Assignee:

Hughes Aircraft Company - Los Angeles CA

International Classification:

G01N 2726

US Classification:

2041531

Abstract:

A method of monitoring major constituents within a plating bath. The method involves applying an electrical signal to a working electrode positioned within the plating bath solution, varying signal parameters, and measuring the resultant response signal. The characteristics of the response signal indicate major constituent concentration levels. The method complements and is easily integrated with known voltammetric techniques for analysis of trace constituents, thus forming an integral part of an efficient overall plating bath analysis system. By adjusting major constituent concentration levels in accordance with measurements made using the method of the present invention, a high quality plating bath can be easily and inexpensively maintained.

US Patent:

52961230, Mar 22, 1994

Filed:

Sep 16, 1992

Appl. No.:

7/945751

Inventors:

Vilambi N. R. K. Reddy - Lakewood CA
Frank A. Ludwig - Rancho Palos Verdes CA
Bruce M. Eliash - Los Angeles CA
Nguyet H. Phan - Los Angeles CA

Assignee:

Hughes Aircraft Company - Los Angeles CA

International Classification:

G01N 2726

US Classification:

2041531

Abstract:

An electrochemical sensor adapted for use in the electrochemical analysis of liquids. The sensor includes a cell assembly having a liquid flow control chamber, sensing chamber and liquid exit chamber. Liquids to be measured are pumped into the liquid flow control chamber where any turbulence in the liquid is dampened. The non-turbulent liquid is passed from the liquid flow control chamber to the sensing chamber. The sensing chamber includes a working electrode and a counter-electrode. The non-turbulent liquid is passed from the sensing chamber to the liquid exit chamber where it is contacted with a reference electrode. The liquid then exits the sensor. The sensor is well-suited for use in the electrochemical analysis of plating bath solutions where sub-milliampere type AC and DC voltammetric measurements are required in order to generate electrochemical spectra which are indicative of constituents present in the solution.