CA1220101A - Electroless nickel plating of aluminum - Google Patents
Electroless nickel plating of aluminumInfo
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- CA1220101A CA1220101A CA000461286A CA461286A CA1220101A CA 1220101 A CA1220101 A CA 1220101A CA 000461286 A CA000461286 A CA 000461286A CA 461286 A CA461286 A CA 461286A CA 1220101 A CA1220101 A CA 1220101A
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- nickel
- bath
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- metal
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C18/00—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating
- C23C18/16—Chemical coating by decomposition of either liquid compounds or solutions of the coating forming compounds, without leaving reaction products of surface material in the coating; Contact plating by reduction or substitution, e.g. electroless plating
- C23C18/1601—Process or apparatus
- C23C18/1633—Process of electroless plating
- C23C18/1646—Characteristics of the product obtained
- C23C18/165—Multilayered product
- C23C18/1651—Two or more layers only obtained by electroless plating
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- General Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Chemically Coating (AREA)
- Other Surface Treatments For Metallic Materials (AREA)
Abstract
ABSTRACT
A process is provided for improving the electroless nickel plating of aluminum which has been pretreated with a barrier coating such as zinc by employing multiple plating baths under controlled operating conditions.
A process is provided for improving the electroless nickel plating of aluminum which has been pretreated with a barrier coating such as zinc by employing multiple plating baths under controlled operating conditions.
Description
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ELECTROLESS NICKEL PLATING OF ALUMINUM
Background of the Invention The invention relates generally to a method for the electroless nickel plating of aluminum and its alloys.
Electroless nickel plating is a process which is very important in the metal finishing industry and which is widely employed for many metal substrates, including steel, copper, nickel, aluminum and alloys thereof. Plating metals such as aluminum, magnesium and their alloys present special problems to electroplaters, how-ever, because, for one, they have surface oxide coatings whichrequire special pre-plating operations to condition the surface for plating. While the present invention is applicable to the electroless plating of such metal substrates with metals such as nickel, coba]t and nickel-cobalt alloys, the description which follows will be primarily directed for convenience to the electro-less nickel plating of aluminum and aluminum alloys which have been conditioned for plating by depositing a zinc coating on its surface.
In general, aluminum parts are first cleaned to remove organic surface contamination, followed by etching to eliminate solid im-purities and alloying constituents from the surface, desmutting to remove the oxide film, and coating with a barrier layer such as zinc or tin to prevent re-oxidation of the cleaned surface. The parts are usually rinsed after each of the above steps and are now ready for electroless nickel plating.
Unfortunately, however, the electroless nickel plating bath used to plate zincated aluminum has relatively short bath life ~;22C)~
when compared to baths used to plate many other metal alloys such as plain steel. Thus, a bath which would normally be useful for, as an example, about ten turnovers for steel, may be useful on barrier coated aluminum for only about five turnovers. After this it must be discarded and replaced because -the nickel deposits on the aluminum start to be blistered. A turnover may be defined as the period during which the quantity of nickel metal that has been plated out is equal to the quantity of nickel in the bath as made up. For example, for a bath initially containing about 6 g/l nickel, the bath would usually be replenished with nickel salts back to 6 g/l as the nickel is consumed during platingO The cumulative replenishment of 6 g/l nickel represents one turnover.
Zincating is a commercially important process to pretreat aluminum surfaces because it is a relatively simple process re-quiring only immersion of the aluminum part in alkaline solution containing zincate ions. The amount of zinc deposited is actually very samll and depends on the time and type of immersion bath used, the aluminum alloy, temperature of the solution and the pretreat-ment process; thicknesses up to about 0.1 microns are usually employed.
An alternative to the zincate process is shown in U.S. Patent No. 3,666,529 to Wright et al. which discloses a method of conditioning aluminum surfaces basically comprising etching the aluminum with an acidic nickel chloride solution to expose the aluminum crystals and deposit a nickel coating, removing the nickel coating with HN03, activating with an alkaline solution contaning hypophosphite ions and then electrolessly plating an ~2'~
alkaline strike coat of nickel at 85 to 90C, followed by electroless nickel deposition to the desired nickel thickness.
U.S. Patent No. 3,672,964 to Bellis et al. discloses pretreating the aluminum surfaces with an aqueous solution of hydrofluoric acid and a material which is displaced by the aluminum and which is active to the electroless plating nickel, thereafter plating the treated aluminum surface wi-th an electro-less nickel bath which is at a pH of 6-7 and contains an amine borane and a monovalent or divalent sulfur compound. These patents however, do not address themselves to the problems encountered in the electroless nickel plating of zincated aluminum and only provide alternative processes which may be more costly and time consuming.
_mmary of the Invention It has now been discovered that the electroless nickel plating of aluminum which has been pretreated with zinc or other barrier coating, may be improved by employing multiple plating baths under controlled operating conditions In a preferred embodiment, the process comprises applying a thin second barrier coating of nickel on the zincated surface from a nickel bath, e.g., electroless, followed by the use of another nickel bath to plate the surface to the desired thick-ness and physical characteristics. The process thus employs at least two nickel plating baths, the first of which is used to apply a thin second barrier coating of nickel on the zincated surface, with the second bath or baths, being used to plate the final nickel coating. The process has resulted in an almost doubled turnover life in the second bath as .~.
,~ -3 ~z~
compared to the prior art process of using a single bath to plate the zincated aluminum to the desired thickness.
Surprisingly, the first bath will last extensively before reaching its normal turnover limit even though it is being used to apply a second barrier coating directly onto a zinc surface, a process decidedly different from the prior art of plating to the desired thickness where the zincated surface is only in contact with the plating solution for a relatively short time. The result using the process of the invention is that the amount of work able to be processed through, e.g., two baths, in sequence, is substantially greater (approximately double) than if the two baths were used separately.
Thus, in accordance with the present invention there is provided in a process for plating zinc or tin coated aluminum substrates with an adherent, non-blistered electroless metal coating by metal plating from a first electroless plating bath to the desired thickness, the bath being replenished as needed to maintain the desired metal concentration, and with the bath being used until the electroless metal coatings pro-duced on the substrates are non-adherent and blistered after which the bath is discarded, the improvement whereby the life of the bath is increased comprising: plating a thin coating of a metal on the substrates from a second electroless metal plating bath prior to plating to the desired thickness with the first bath, both electroless metal plating baths containing a source of metal ions and a reducing agen-t to reduce the metal ions.
Description of the Preferred Embodiments The aluminum part to be electrolessly nickel plated is, ~.2~
as discussed hereinabove, pretreated and provided with a barrier coating such as zinc, or other metals such as tin, using known techniques and procedures. Small amounts oE metals, usually less than 10%, may be co-deposited with the barrier coating metal for purposes such as to modify the deposit prop-erties of coatings thereon, among others. Many metals may be used such as cobalt, nickel, copper and iron.
Electroless nickel plating compositions for applying the nickel coatings are well known in the art and plating pro-cesses and compositions are described in numerous publications.For example, compositions for depositing electroless nickel are described in U.S. Patent Nos. 2,690,401; 2,690,402; 2,762,723;
ELECTROLESS NICKEL PLATING OF ALUMINUM
Background of the Invention The invention relates generally to a method for the electroless nickel plating of aluminum and its alloys.
Electroless nickel plating is a process which is very important in the metal finishing industry and which is widely employed for many metal substrates, including steel, copper, nickel, aluminum and alloys thereof. Plating metals such as aluminum, magnesium and their alloys present special problems to electroplaters, how-ever, because, for one, they have surface oxide coatings whichrequire special pre-plating operations to condition the surface for plating. While the present invention is applicable to the electroless plating of such metal substrates with metals such as nickel, coba]t and nickel-cobalt alloys, the description which follows will be primarily directed for convenience to the electro-less nickel plating of aluminum and aluminum alloys which have been conditioned for plating by depositing a zinc coating on its surface.
In general, aluminum parts are first cleaned to remove organic surface contamination, followed by etching to eliminate solid im-purities and alloying constituents from the surface, desmutting to remove the oxide film, and coating with a barrier layer such as zinc or tin to prevent re-oxidation of the cleaned surface. The parts are usually rinsed after each of the above steps and are now ready for electroless nickel plating.
Unfortunately, however, the electroless nickel plating bath used to plate zincated aluminum has relatively short bath life ~;22C)~
when compared to baths used to plate many other metal alloys such as plain steel. Thus, a bath which would normally be useful for, as an example, about ten turnovers for steel, may be useful on barrier coated aluminum for only about five turnovers. After this it must be discarded and replaced because -the nickel deposits on the aluminum start to be blistered. A turnover may be defined as the period during which the quantity of nickel metal that has been plated out is equal to the quantity of nickel in the bath as made up. For example, for a bath initially containing about 6 g/l nickel, the bath would usually be replenished with nickel salts back to 6 g/l as the nickel is consumed during platingO The cumulative replenishment of 6 g/l nickel represents one turnover.
Zincating is a commercially important process to pretreat aluminum surfaces because it is a relatively simple process re-quiring only immersion of the aluminum part in alkaline solution containing zincate ions. The amount of zinc deposited is actually very samll and depends on the time and type of immersion bath used, the aluminum alloy, temperature of the solution and the pretreat-ment process; thicknesses up to about 0.1 microns are usually employed.
An alternative to the zincate process is shown in U.S. Patent No. 3,666,529 to Wright et al. which discloses a method of conditioning aluminum surfaces basically comprising etching the aluminum with an acidic nickel chloride solution to expose the aluminum crystals and deposit a nickel coating, removing the nickel coating with HN03, activating with an alkaline solution contaning hypophosphite ions and then electrolessly plating an ~2'~
alkaline strike coat of nickel at 85 to 90C, followed by electroless nickel deposition to the desired nickel thickness.
U.S. Patent No. 3,672,964 to Bellis et al. discloses pretreating the aluminum surfaces with an aqueous solution of hydrofluoric acid and a material which is displaced by the aluminum and which is active to the electroless plating nickel, thereafter plating the treated aluminum surface wi-th an electro-less nickel bath which is at a pH of 6-7 and contains an amine borane and a monovalent or divalent sulfur compound. These patents however, do not address themselves to the problems encountered in the electroless nickel plating of zincated aluminum and only provide alternative processes which may be more costly and time consuming.
_mmary of the Invention It has now been discovered that the electroless nickel plating of aluminum which has been pretreated with zinc or other barrier coating, may be improved by employing multiple plating baths under controlled operating conditions In a preferred embodiment, the process comprises applying a thin second barrier coating of nickel on the zincated surface from a nickel bath, e.g., electroless, followed by the use of another nickel bath to plate the surface to the desired thick-ness and physical characteristics. The process thus employs at least two nickel plating baths, the first of which is used to apply a thin second barrier coating of nickel on the zincated surface, with the second bath or baths, being used to plate the final nickel coating. The process has resulted in an almost doubled turnover life in the second bath as .~.
,~ -3 ~z~
compared to the prior art process of using a single bath to plate the zincated aluminum to the desired thickness.
Surprisingly, the first bath will last extensively before reaching its normal turnover limit even though it is being used to apply a second barrier coating directly onto a zinc surface, a process decidedly different from the prior art of plating to the desired thickness where the zincated surface is only in contact with the plating solution for a relatively short time. The result using the process of the invention is that the amount of work able to be processed through, e.g., two baths, in sequence, is substantially greater (approximately double) than if the two baths were used separately.
Thus, in accordance with the present invention there is provided in a process for plating zinc or tin coated aluminum substrates with an adherent, non-blistered electroless metal coating by metal plating from a first electroless plating bath to the desired thickness, the bath being replenished as needed to maintain the desired metal concentration, and with the bath being used until the electroless metal coatings pro-duced on the substrates are non-adherent and blistered after which the bath is discarded, the improvement whereby the life of the bath is increased comprising: plating a thin coating of a metal on the substrates from a second electroless metal plating bath prior to plating to the desired thickness with the first bath, both electroless metal plating baths containing a source of metal ions and a reducing agen-t to reduce the metal ions.
Description of the Preferred Embodiments The aluminum part to be electrolessly nickel plated is, ~.2~
as discussed hereinabove, pretreated and provided with a barrier coating such as zinc, or other metals such as tin, using known techniques and procedures. Small amounts oE metals, usually less than 10%, may be co-deposited with the barrier coating metal for purposes such as to modify the deposit prop-erties of coatings thereon, among others. Many metals may be used such as cobalt, nickel, copper and iron.
Electroless nickel plating compositions for applying the nickel coatings are well known in the art and plating pro-cesses and compositions are described in numerous publications.For example, compositions for depositing electroless nickel are described in U.S. Patent Nos. 2,690,401; 2,690,402; 2,762,723;
2,935,425; 2,929,742; and 3,338,726. Other useful compositions for depositing nickel and its alloys are disclosed in the 35th Annual ~dition of the Metal Finishing Guidebook for 1967, Metal and Plastics Publications, Inc., Westwood, N.J., pages 483-486.
In general, electroless nickel deposition solutions comprise at least four ingredients dissolved in a solvent, typically water. They are (1) a source of the nickel ions, (2) a reducing agent such as a hypophosphite or an amine borane, (3) an acid or hydroxide pH adjustor to provide required pH and (4) a complexing agent for metal ions sufficient to prevent their precipitation in solution. A large number of suitable complexing agents for electroless nickel solutions are described in the above noted publications. In some formu-lations, the complexing agents are helpful but not a necessity.
It will be appreciated by those skilled in the art that the nickel, or other metal being applied, is usually in the form ~P2~
of an alloy with the other materials present in the bath. Thus, if hypophosphite is used as ~ne reducing agent, the deposit will contain nickel and phosphorous. Similarly, if an amine borane is employed, the deposit will contain nickel and boron. Thus, use of the term nickel includes the other elements normally deposited therewith.
The nickel ion may be provided by -the use of any soluble salt such as nickel sulfate, nickel chloride, nickel acetate and mixtures thereof. The concentration of the nickel in solution may vary widely and is about .1 to 100 g/l, preferably about 2 to 50 g/l, e.g., 2 to 10 g/l.
The reducing agent is usually the hypophosphite ion sup-plied to the bath by any suitable source such as sodium, potass-ium, ammonium and nickel hypophosphite. Other reducing agents such , _, jf ~ 5a-as amine boranes, borohydrides and hydrazine may also suitably be employed. The concentration of the reducing agent is generally in excess of the amount sufficient to reduce the nickel in the bath.
The baths may be acid, neutral or alkaline and the acid or alkaline pH adjustor may be selected from a wide range of materials such as ammonium hydroxide, sodium hydroxide, hydrochloric acid and the like. The pH of the bath may range from about 2 to 11.5, with a range of 7 to 12, e.g., 9 to ll, being preferred for the bath used to deposit the second barrier coating and a range of 2 to 7, e.g., 4 to 6, being preferred for the bath used to deposit the finaly layer of nickel.
The complexing agent may be selected from a wide variety of materials containing anions such as acetate, citrate, glycollate, pyrophosphate and thelike, with mixtures thereof being suitable.
Ranges for the complexing agent, based on the anion, may vary widely, for example, about 0 to 300 g/l, preferably about 5 to 50 g/l.
The electroless nickel plating baths may also contain other ingredients known in the art such as buffering agents, bath stabilizers, rate promoters, brightners, etc.
A suitable bath may be formed by dissolving the ingredients in water and adjusting the pH to the desired range.
The zinc barrier coated aluminum part may be plated with the second barrier coating by electroless nickel plating, by immersing the part in an electroless nickel bath to a thickness adequate to provide a suitable barrier coating for blister-free deposits on the final nickel plate, e.g., up to about 0.1 mil, or higher, ,~.Z~
with 0.005 to 0.08 mils, e.g., 0.01 to 0.05, being preferred.
An immersion time of 15 seconds to 15 minutes usually provides the desired coating, depending on ba-th parameters. A temperature range of about 25 to boiling, e.g., 100C, may be employed, with a range of about 30 to 95C being preferred.
The next step in the procedure is to complete the nickel plating to the desired thickness and physical characteristics by immersing the nickel part in another electroless nickel plating bath which is maintained over a temperature range of about 30 to 100C, e.g., boiling, preferably 80 to 95C. A thickness up to 5 mils, or higher may be employed, with a range of about 0.1 to 2 mils used for most applications.
It will be appreciated by those skilled in the art that the rate of plating may be influenced by many factors including (1) pH of the plating solution, (2) concentration of reductant, (3) temperature of plating bath, (4) concentration of soluble nickel, (5) ratio of volume of bath cm.3/area plated cm. , (6) presence of soluble fluoride salts (rate promoter) and (7) presence of wetting agent and/or agitation, and that the above parameters are only provided to give general gu:idance for practising the invention;
the invention residing in the use of multiple baths are herein-before described to provide an enhanced plating process.
Examples illustrating various plating baths and conditions under which the process may be carried out follows.
EX~MPLE I
Aluminum Association Number 3003 aluminum panels 2~ X 4 inch were alkaline cleaned, water rinsed, acid etched, water rinsed, desmutted and water rinsed. The panels were then zincated at room temperature for 30 seconds using an aqueous solution containing 100 g/l ZnO, 500 g/l NaOH, 1 g/l FeCl3 and 10 g/l Rochelle salt.
The panels were water rinsed and a number of the panels plated in an electroless nickel plating bath sold by Enthone, Incorporated under thec~m~ ENPLATE NI-431 by immersion in the bath, which I0 was maintained at about 90C., for about 30 minutes. A coating of about 0.4 mils was obtained on each panel. The nickel and hypophosphite concentra-tion were replenished when the concentration fell to about 4 g/l nickel. A total of about 5 turnovers were obtained before the nickel plating started to blister. It is at this point that the bath normally cannot be further used to plate zincated aluminum and must be discarded.
A zincated panel prepared as above was plated with a thin second barrier coating of nickel (about 0.02 mil) in the following electroless nickel plating bath for 3 minutes at 40C:
Nickel Sulfamate 24 g/l Tetra Potassium Pyrophosphate 60 g/l Sodium Hypophosphite 27 g/l N~40H to a pH of 10 It was then immersed in the plating bath having 5 turnovers and received a blister-free nickel deposit. An immersion time of about 30 minutes produced a nickel thickness of about 0.4 mils.
Upon removing the plated panel, a zincated panel (with no nickel ~ q~
second barrier coating) was ~mmersed in the same bath, and the coating was blistered. The above sequence was repeated a number of times, with the second barrier nickel coated zincated aluminum panel obtaining blister-free deposits as compared with the blis-tered deposits obtained on the zincated aluminum (without the thin second barrier nickel coating), Another 4 turnovers were obtained resulting in a total of about 9 turnovers for the bath. The bath was still useful at this point to plate on the second barrier coated panels but the plating rate was very slow, as is usual when a bath has reached about 9-10 turnovers.
The example demonstrates that the life of an electroless nickel plating bath used to plate zincated aluminum may be in-creased if the zincated aluminum has a thin second barrier nickel coating before immersion in the bath.
EXAMPLE II
A zincated aluminum panel as described above was plated with a thin second barrier coating of nickel (about 0.02 mil) for 5 minutes at 65C in an electroless plating bath containing the following ingredients and adjusted to pH 7.5 with NH40H:
S 4 2 4 g/l CoSO4 7 H2O 28 g/l Na Citrate-2 H2O75 g/l Ammonium Hydroxide 9.4 g/l Na Hypophosphite28 g/l NH4C1 42 g/l When the panel was immersed in the plating bath of Example I
(having 5 turnovers), it received a blister-free nickel deposit.
A zincated panel with no thin nickel coating was immersed in the same bath, and the deposit was blistered.
EXAMPLE III
Example II was repeated using a bath marketed under the trade mark ENPLATE NI-431 by Enthone, Incorporated to electrolessly plate the thin nickel second barrier coating with the same results being obtained, to wit, the second barrier coated panels receiving blister-free deposits and the zinc coated panels receiving blistered deposits.
While there has been described what is at present considered to be the preferred embodiment of the invention, it will be understood that various modifications may be made therein, and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.
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In general, electroless nickel deposition solutions comprise at least four ingredients dissolved in a solvent, typically water. They are (1) a source of the nickel ions, (2) a reducing agent such as a hypophosphite or an amine borane, (3) an acid or hydroxide pH adjustor to provide required pH and (4) a complexing agent for metal ions sufficient to prevent their precipitation in solution. A large number of suitable complexing agents for electroless nickel solutions are described in the above noted publications. In some formu-lations, the complexing agents are helpful but not a necessity.
It will be appreciated by those skilled in the art that the nickel, or other metal being applied, is usually in the form ~P2~
of an alloy with the other materials present in the bath. Thus, if hypophosphite is used as ~ne reducing agent, the deposit will contain nickel and phosphorous. Similarly, if an amine borane is employed, the deposit will contain nickel and boron. Thus, use of the term nickel includes the other elements normally deposited therewith.
The nickel ion may be provided by -the use of any soluble salt such as nickel sulfate, nickel chloride, nickel acetate and mixtures thereof. The concentration of the nickel in solution may vary widely and is about .1 to 100 g/l, preferably about 2 to 50 g/l, e.g., 2 to 10 g/l.
The reducing agent is usually the hypophosphite ion sup-plied to the bath by any suitable source such as sodium, potass-ium, ammonium and nickel hypophosphite. Other reducing agents such , _, jf ~ 5a-as amine boranes, borohydrides and hydrazine may also suitably be employed. The concentration of the reducing agent is generally in excess of the amount sufficient to reduce the nickel in the bath.
The baths may be acid, neutral or alkaline and the acid or alkaline pH adjustor may be selected from a wide range of materials such as ammonium hydroxide, sodium hydroxide, hydrochloric acid and the like. The pH of the bath may range from about 2 to 11.5, with a range of 7 to 12, e.g., 9 to ll, being preferred for the bath used to deposit the second barrier coating and a range of 2 to 7, e.g., 4 to 6, being preferred for the bath used to deposit the finaly layer of nickel.
The complexing agent may be selected from a wide variety of materials containing anions such as acetate, citrate, glycollate, pyrophosphate and thelike, with mixtures thereof being suitable.
Ranges for the complexing agent, based on the anion, may vary widely, for example, about 0 to 300 g/l, preferably about 5 to 50 g/l.
The electroless nickel plating baths may also contain other ingredients known in the art such as buffering agents, bath stabilizers, rate promoters, brightners, etc.
A suitable bath may be formed by dissolving the ingredients in water and adjusting the pH to the desired range.
The zinc barrier coated aluminum part may be plated with the second barrier coating by electroless nickel plating, by immersing the part in an electroless nickel bath to a thickness adequate to provide a suitable barrier coating for blister-free deposits on the final nickel plate, e.g., up to about 0.1 mil, or higher, ,~.Z~
with 0.005 to 0.08 mils, e.g., 0.01 to 0.05, being preferred.
An immersion time of 15 seconds to 15 minutes usually provides the desired coating, depending on ba-th parameters. A temperature range of about 25 to boiling, e.g., 100C, may be employed, with a range of about 30 to 95C being preferred.
The next step in the procedure is to complete the nickel plating to the desired thickness and physical characteristics by immersing the nickel part in another electroless nickel plating bath which is maintained over a temperature range of about 30 to 100C, e.g., boiling, preferably 80 to 95C. A thickness up to 5 mils, or higher may be employed, with a range of about 0.1 to 2 mils used for most applications.
It will be appreciated by those skilled in the art that the rate of plating may be influenced by many factors including (1) pH of the plating solution, (2) concentration of reductant, (3) temperature of plating bath, (4) concentration of soluble nickel, (5) ratio of volume of bath cm.3/area plated cm. , (6) presence of soluble fluoride salts (rate promoter) and (7) presence of wetting agent and/or agitation, and that the above parameters are only provided to give general gu:idance for practising the invention;
the invention residing in the use of multiple baths are herein-before described to provide an enhanced plating process.
Examples illustrating various plating baths and conditions under which the process may be carried out follows.
EX~MPLE I
Aluminum Association Number 3003 aluminum panels 2~ X 4 inch were alkaline cleaned, water rinsed, acid etched, water rinsed, desmutted and water rinsed. The panels were then zincated at room temperature for 30 seconds using an aqueous solution containing 100 g/l ZnO, 500 g/l NaOH, 1 g/l FeCl3 and 10 g/l Rochelle salt.
The panels were water rinsed and a number of the panels plated in an electroless nickel plating bath sold by Enthone, Incorporated under thec~m~ ENPLATE NI-431 by immersion in the bath, which I0 was maintained at about 90C., for about 30 minutes. A coating of about 0.4 mils was obtained on each panel. The nickel and hypophosphite concentra-tion were replenished when the concentration fell to about 4 g/l nickel. A total of about 5 turnovers were obtained before the nickel plating started to blister. It is at this point that the bath normally cannot be further used to plate zincated aluminum and must be discarded.
A zincated panel prepared as above was plated with a thin second barrier coating of nickel (about 0.02 mil) in the following electroless nickel plating bath for 3 minutes at 40C:
Nickel Sulfamate 24 g/l Tetra Potassium Pyrophosphate 60 g/l Sodium Hypophosphite 27 g/l N~40H to a pH of 10 It was then immersed in the plating bath having 5 turnovers and received a blister-free nickel deposit. An immersion time of about 30 minutes produced a nickel thickness of about 0.4 mils.
Upon removing the plated panel, a zincated panel (with no nickel ~ q~
second barrier coating) was ~mmersed in the same bath, and the coating was blistered. The above sequence was repeated a number of times, with the second barrier nickel coated zincated aluminum panel obtaining blister-free deposits as compared with the blis-tered deposits obtained on the zincated aluminum (without the thin second barrier nickel coating), Another 4 turnovers were obtained resulting in a total of about 9 turnovers for the bath. The bath was still useful at this point to plate on the second barrier coated panels but the plating rate was very slow, as is usual when a bath has reached about 9-10 turnovers.
The example demonstrates that the life of an electroless nickel plating bath used to plate zincated aluminum may be in-creased if the zincated aluminum has a thin second barrier nickel coating before immersion in the bath.
EXAMPLE II
A zincated aluminum panel as described above was plated with a thin second barrier coating of nickel (about 0.02 mil) for 5 minutes at 65C in an electroless plating bath containing the following ingredients and adjusted to pH 7.5 with NH40H:
S 4 2 4 g/l CoSO4 7 H2O 28 g/l Na Citrate-2 H2O75 g/l Ammonium Hydroxide 9.4 g/l Na Hypophosphite28 g/l NH4C1 42 g/l When the panel was immersed in the plating bath of Example I
(having 5 turnovers), it received a blister-free nickel deposit.
A zincated panel with no thin nickel coating was immersed in the same bath, and the deposit was blistered.
EXAMPLE III
Example II was repeated using a bath marketed under the trade mark ENPLATE NI-431 by Enthone, Incorporated to electrolessly plate the thin nickel second barrier coating with the same results being obtained, to wit, the second barrier coated panels receiving blister-free deposits and the zinc coated panels receiving blistered deposits.
While there has been described what is at present considered to be the preferred embodiment of the invention, it will be understood that various modifications may be made therein, and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.
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Claims (14)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In the process for plating a zinc coated aluminum surface with nickel the improvement wherein the turnover life of the primary electroless nickel plating bath is increased, said improvement comprising:
(a) applying a first coating of nickel on the zinc coated aluminum surface from an electroless nickel plating bath separate from said primary electroless nickel plating bath, said bath having a pH of about 2 to 12;
(b) applying a second coating of nickel on the first coating of nickel from said primary electroless nickel plating bath, said primary bath having a pH of about 2 to 7;
(c) said first coating being thinner than said second coating; and (d) both of said electroless nickel plating baths containing a source of nickel ions and a reducing agent to reduce the nickel ions.
(a) applying a first coating of nickel on the zinc coated aluminum surface from an electroless nickel plating bath separate from said primary electroless nickel plating bath, said bath having a pH of about 2 to 12;
(b) applying a second coating of nickel on the first coating of nickel from said primary electroless nickel plating bath, said primary bath having a pH of about 2 to 7;
(c) said first coating being thinner than said second coating; and (d) both of said electroless nickel plating baths containing a source of nickel ions and a reducing agent to reduce the nickel ions.
2. The process of claim 1 wherein the first coating of nickel on the zinc coated surface is up to about 0.1 mil.
3. The process of claim 1 wherein the bath used to coat the first coating of nickel contains a hypophospite reducing agent.
4. The process of claim 1 wherein the primary electroless nickel plating bath contains a hypophosphite reducing agent.
5. The process of claim 1 wherein the primary electroless nickel plating bath contains an amine borane reducing agent.
6. The process of claim 1 wherein the bath used to coat the first coating of nickel has a pH of about 7 to 12.
7. The process of claim 6 wherein the bath used to coat the first coating of nickel contains a hypophosphite reducing agent.
8. The process of claim 7 wherein the primary electroless nickel plating bath contains a hypophosphite reducing agent.
9. The process of claim 7 wherein the primary electroless nickel plating bath contains an amine borane reducing agent.
10. In a process for plating zinc or tin coated aluminum substrates with an adherent, non-blistered electroless metal coating by metal plating from a first electroless plating bath to the desired thickness, the bath being replenished as needed to maintain the desired metal concentration, and with the bath being used until the electroless metal coatings produced on the substrates are non-adherent and blistered after which the bath is discarded, the improvement whereby the life of the bath is increased comprising:
plating a thin coating of a metal on the substrates from a second electroless metal plating bath prior to plating to the desired thickness with the first bath, both electroless metal plating baths containing a source of metal ions and a reducing agent to reduce the metal ions.
plating a thin coating of a metal on the substrates from a second electroless metal plating bath prior to plating to the desired thickness with the first bath, both electroless metal plating baths containing a source of metal ions and a reducing agent to reduce the metal ions.
11. The process of claim 10 wherein the thin metal coating on the zinc or tin coating is up to about 0.1 mil.
12. The process of claim 11 wherein the thin metal coating on the zinc or tin coating is about 0.005 to 0.08 mils.
13. The process of claim 10 wherein the metal baths are cobalt, copper, nickel or alloys thereof.
14. The process of claim 13 wherein the metal of each bath is nickel.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US52535883A | 1983-08-22 | 1983-08-22 | |
| US525,358 | 1990-05-17 | ||
| HK98105637A HK1006860A1 (en) | 1983-08-22 | 1998-06-18 | Electroless nickel plating of aluminum |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1220101A true CA1220101A (en) | 1987-04-07 |
Family
ID=26316726
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000461286A Expired CA1220101A (en) | 1983-08-22 | 1984-08-17 | Electroless nickel plating of aluminum |
Country Status (9)
| Country | Link |
|---|---|
| EP (1) | EP0153369B1 (en) |
| JP (1) | JPS60502057A (en) |
| AU (1) | AU558946B2 (en) |
| BR (1) | BR8407027A (en) |
| CA (1) | CA1220101A (en) |
| DE (1) | DE3486228T2 (en) |
| HK (1) | HK1006860A1 (en) |
| MX (1) | MX167978B (en) |
| WO (1) | WO1985001070A1 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5476688A (en) * | 1988-08-29 | 1995-12-19 | Ostolski; Marian J. | Process for the preparation of noble metal coated non-noble metal substrates, coated materials produced in accordance therewith and compositions utilizing the coated materials |
| JP6411279B2 (en) * | 2015-05-11 | 2018-10-24 | 東京エレクトロン株式会社 | Plating process and storage medium |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US366529A (en) * | 1887-07-12 | James timms | ||
| JPS5345787A (en) * | 1976-10-08 | 1978-04-24 | Shiguma Ruutein Narodoni Podon | Method of working nonncircular functional hole of drawing die |
| US4169171A (en) * | 1977-11-07 | 1979-09-25 | Harold Narcus | Bright electroless plating process and plated articles produced thereby |
| JPS6015706B2 (en) * | 1977-12-19 | 1985-04-20 | 株式会社東芝 | Surface treatment method of Al and Al alloy for soldering |
| US4346128A (en) * | 1980-03-31 | 1982-08-24 | The Boeing Company | Tank process for plating aluminum substrates including porous aluminum castings |
| US4358923A (en) * | 1980-04-10 | 1982-11-16 | Surface Technology, Inc. | Composite coatings for open-end machinery parts |
| SU926064A1 (en) * | 1980-07-15 | 1982-05-07 | Алтайский Сельскохозяйственный Институт | Aqueous solution for preparing metal surface to chemical nickel plating |
-
1984
- 1984-08-08 BR BR8407027A patent/BR8407027A/en not_active IP Right Cessation
- 1984-08-08 JP JP59503212A patent/JPS60502057A/en active Granted
- 1984-08-08 AU AU32178/84A patent/AU558946B2/en not_active Ceased
- 1984-08-08 DE DE84903142T patent/DE3486228T2/en not_active Expired - Lifetime
- 1984-08-08 EP EP84903142A patent/EP0153369B1/en not_active Expired - Lifetime
- 1984-08-08 WO PCT/US1984/001253 patent/WO1985001070A1/en active IP Right Grant
- 1984-08-17 CA CA000461286A patent/CA1220101A/en not_active Expired
- 1984-08-21 MX MX202448A patent/MX167978B/en unknown
-
1998
- 1998-06-18 HK HK98105637A patent/HK1006860A1/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| EP0153369A4 (en) | 1986-02-13 |
| JPH0319302B2 (en) | 1991-03-14 |
| DE3486228D1 (en) | 1993-11-18 |
| BR8407027A (en) | 1985-07-30 |
| HK1006860A1 (en) | 1999-03-19 |
| JPS60502057A (en) | 1985-11-28 |
| AU558946B2 (en) | 1987-02-12 |
| AU3217884A (en) | 1985-03-29 |
| DE3486228T2 (en) | 1994-04-14 |
| MX167978B (en) | 1993-04-26 |
| EP0153369A1 (en) | 1985-09-04 |
| EP0153369B1 (en) | 1993-10-13 |
| WO1985001070A1 (en) | 1985-03-14 |
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