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US4125642A
Expired / Lapsed
US
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Method for conducting electroless metal-plating processes
Assignee: United States Department of Energy
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Filing: 1977-08-25
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Granted: 1978-11-14
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Expires: 1997-08-25
Abstract
Abstract This invention is an improved method for conducting electroless metal-plating processes in a metal tank which is exposed to the plating bath. The invention solves a problem commonly encountered in such processes: how to determine when it is advisable to shutdown the process in order to clean and/or re-passivate the tank. The new method comprises contacting the bath with a current-conducting, non-catalytic probe and, during plating operations, monitoring the gradually changing difference in electropotential between the probe and tank. It has been found that the value of this voltage is indicative of the extent to which nickel-bearing decomposition products accumulate on the tank. By utilizing the voltage to determine when shutdown for cleaning is advisable, the operator can avoid premature shutdown and at the same time avoid prolonging operations to the point that spontaneous decomposition occurs.
Inventors
- 👤 George S. Petit
- 👤 Ralph R. Wright
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 13:16
CPC Classifications
C; C23; C23C; C23C18/00; C23C18/16; C23C18/1601; C23C18/1633; C23C18/1675
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
127 words
In an electroless plating process for depositing a selected metal on a catalytic surface selected from metals of the group consisting of iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, and platinum, and utilizing a plating bath including an aqueous solution containing a water-soluble salt of said metal and a hypophosphite reducing agent for said salt, said process being conducted in a nitric-acid-passivated stainless-steel tank in contact with said bath, the improvement comprising: inserting in said bath an electrically conductive probe having a surface of chrome, which is non-catalytic and nonreactive with respect to the plating bath; monitoring the difference in electropotential between said probe and said tank in the course of the plating process; and terminating the plating process when said difference reaches a preselected value.
Claim 2
Dependent Claim
127 words
In an electroless plating process for depositing a selected metal on a catalytic surface selected from metals of the group consisting of iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, and platinum, and utilizing a plating bath including an aqueous solution containing a water-soluble salt of said metal and a hypophosphite reducing agent for said salt, said process being conducted in a nitric-acid-passivated stainless-steel tank in contact with said bath, the improvement comprising: inserting in said bath an electrically conductive probe having a surface of chrome, which is non-catalytic and nonreactive with respect to the plating bath; monitoring the difference in electropotential between said probe and said tank in the course of the plating process; and terminating the plating process when said difference reaches a preselected value.
Claim 3
Dependent Claim
20 words
The method of claim 1 wherein said preselected value is in the range of from aproximately -0.35 to -0.5 volt.
Claim 4
Dependent Claim
149 words
In an electroless plating process for depositing a metal on a catalytic surface selected from metals of the group consisting of iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, and platinum, and utilizing a plating bath including an aqueous solution containing a water-soluble salt of said metal and a hypophosphite reducing agent for said salt, said process being conducted in a stainless steel tank whose interior has been passivated by pre-treatment with nitric acid, the improvement comprising: inserting in said bath an electrically conductive probe having a chrome surface; monitoring the difference in electropotential between said probe and said tank in the course of the plating process; terminating the plating process when said difference reaches a preselected value indicating that buildup of said metal on decomposition-product deposits has reached a selected limit; draining said tank; and treating said tank with dilute nitric acid solution to remove decomposition products therefrom.
Claim 5
Dependent Claim
149 words
In an electroless plating process for depositing a metal on a catalytic surface selected from metals of the group consisting of iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, and platinum, and utilizing a plating bath including an aqueous solution containing a water-soluble salt of said metal and a hypophosphite reducing agent for said salt, said process being conducted in a stainless steel tank whose interior has been passivated by pre-treatment with nitric acid, the improvement comprising: inserting in said bath an electrically conductive probe having a chrome surface; monitoring the difference in electropotential between said probe and said tank in the course of the plating process; terminating the plating process when said difference reaches a preselected value indicating that buildup of said metal on decomposition-product deposits has reached a selected limit; draining said tank; and treating said tank with dilute nitric acid solution to remove decomposition products therefrom.
Claim 6
Dependent Claim
130 words
In an electroless plating process for depositing nickel on a catalytic surface selected from metals of the group consisting of iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium and platinum, and utilizing a plating bath including an aqueous solution containing a water-soluble salt of nickel and a hypophosphite reducing agent for said salt, said process being conducted in a stainless steel tank in contact with said bath, the improvement comprising: inserting in said bath an electrically conductive probe having a chrome surface; monitoring the difference in electropotential between said probe and said tank in the course of the plating process; and terminating the plating process when said difference in electropotential has successively (a) decreased to zero (b) reversed polarity, and (c) increased to a preselected value having said reversed polarity.
Claim 7
Dependent Claim
130 words
In an electroless plating process for depositing nickel on a catalytic surface selected from metals of the group consisting of iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium and platinum, and utilizing a plating bath including an aqueous solution containing a water-soluble salt of nickel and a hypophosphite reducing agent for said salt, said process being conducted in a stainless steel tank in contact with said bath, the improvement comprising: inserting in said bath an electrically conductive probe having a chrome surface; monitoring the difference in electropotential between said probe and said tank in the course of the plating process; and terminating the plating process when said difference in electropotential has successively (a) decreased to zero (b) reversed polarity, and (c) increased to a preselected value having said reversed polarity.
Claim 8
Dependent Claim
19 words
The method of claim 4 wherein said preselected value is in the range of approximately -0.35 to -0.5 volt.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1981-11-13 | 1982-05-15 | 1982-11-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-11-13 | 1986-05-15 | 1986-11-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-11-13 | 1990-05-15 | 1990-11-14 | $7700.00 | Window Closed / Lapsed |