Patent Application
20250137156
The present invention relates generally to a method of depositing a satin nickel layer on a substrate and a nickel electroplating bath for use therein.
Electroplating baths are generally used for depositing metals and metal alloys on various substrates. For example, a nickel electroplating bath can be used to deposit nickel or a nickel alloy onto a substrate for a decorative finish, which can include bright finishes, satin finishes, matte finishes, and other similar finishes. Satin finishes exhibit an even and non-reflective texture that contains minimal or no defects. Satin finishes usually increase the fingerprint sensitivity of a product on which they are applied.
One of the most commonly known and used nickel electroplating baths is the Watts bath, which typically includes nickel sulfate, nickel chloride and boric acid. The Watts bath typically operates at a pH range of 2-5.2, a plating temperature range of 30-70° C. and a current density range of 1-6 A/dm2. Nickel sulfate is included in the baths in comparatively large amounts to provide the desired nickel ion concentrations. In case of satin finishes, the required amount of nickel sulfate is typically more than 50% higher compared to a standard Watts bath. Nickel chloride improves anode corrosion and increases conductivity. Boric acid is typically used as a weak buffer to maintain the pH of the bath.
In order to achieve bright and lustrous deposits, various wetting agents and/or organic and inorganic brightening agents are often added to the baths, which additives can be modified depending on the preferred finish, which can include a bright finish or a satin finish. These wetting agents and/or brighteners help to achieve a desired decorative finish, by creating a brighter, more even, and more lustrous appearance. Most of the wetting agents and/or brightener cause a mirror bright finish. Only some combinations of special satin effect additives with suitable wetting agents and/or brightener are able to roughen the nickel layer structure, reducing the fingerprint sensitivity of the final product.
A common problem with many metal plating baths, is recovery of valuable bath components and disposal of break-down products after use. While some bath components may be readily recovered, although recovery processes may be costly, other components and break-down products may be difficult to recover and are discharged in waste water, potentially leading to environmental contamination. In the case of a typically Watts bath, nickel sulfate and nickel chloride may be readily recovered, but recovery of boric acid is challenging and often ends up in waste water, contaminating the environment.
Many jurisdictions worldwide are passing stricter environmental laws and regulations with respect to how chemical waste is treated and the types of chemicals industries may use in development and manufacturing processes. Accordingly, it is desirable to develop a boric acid-free nickel plating bath that has the desired plating characteristics.
In the case of nickel electroplating baths, attempts have been made to substitute the boric acid with alkyl carboxylic acids. However, alkyl carboxylic acid baths often produce only bright nickel deposits and have a negative impact on satin structures. In addition, some of these alkyl carboxylic acids (e.g., example citric acid) are able to bond nickel ions very strongly in complexes, which causes problems in wastewater treatment. Thus, there remains a need in the art for an improved nickel electroplating bath that is free of boric acid and that overcomes the deficiencies of the prior art.
As deposited, a bright nickel layer has a high degree of shine and is reflective. Compared to a bright finish, a satin finish has less shine and a duller appearance (i.e., is more non-reflective). In some automotive applications, the non-reflective property is required for safety reasons. In addition, the sanitary industry uses satin surfaces as a luxury design for high end market products. A satin finish typically has a gloss value in the range of about 5 to about 500 GU (gloss units), with a coarse satin range of about 5 to about 20 GU and a smooth satin range of about 100 to about 500 GU when measured at 60°.
U.S. Pat. No. 7,361,262 to Dahms et al., the subject matter of which is herein incorporated by reference in its entirety, describes a nickel electroplating bath with a relatively low concentration of nickel. However, the bath requires the use a boric acid pH buffer.
U.S. Pat. Pub. No. 2011/0233065 to Konigshofen et al., the subject matter of which is herein incorporated by reference in its entirety, describes a low nickel concentration electroplating bath with the addition of a high-chain length polyethylene glycol in a stable bath composition. However, this bath also requires the use of a boric acid pH buffer.
U.S. Pat. No. 4,159,926 to Barnes et al., the subject matter of which is herein incorporated by reference in its entirety, describes a nickel electroplating bath with acetate as a complexing agent for the nickel. However, the nickel electroplating bath is used to produce a bright nickel layer, not a satin nickel layer.
EP3,642,396 B1 to Wachter et al. describes a low nickel concentration electroplating bath that does not contain boric acid. However, the bath is used for depositing a bright nickel layer, not a satin nickel layer.
DE102014118614 to Meyerovich et al. also describes a low nickel concentration electroplating bath without the use of boric acid. However, this electroplating bath does not describe a method of electrodeposition of a nickel layer on a substrate that exhibits a satin finish.
JP54245813 to Aikawa Hiroki et al describes the use of aminoalkane sulfonic acids as replacement for boric acid in a pH range of 4.0 to 6.0. However, the bath is used for depositing a bright nickel layer, not a satin nickel layer.
Thus, it would be desirable to provide an improved nickel deposition bath that is capable of producing a satin nickel finish on a substrate without the use of a boric acid pH buffer.
It is an object of the present invention to provide a nickel electroplating bath that is at least substantially free of boric acid or a salt or a derivative thereof.
It is yet another object of the present invention to provide a nickel electroplating bath that contains a relatively low concentration of nickel.
It is another object of the present invention to provide a nickel electroplating bath that is capable of electrodepositing a satin nickel layer on an underlying substrate.
It is another object of the present invention to provide a nickel electroplating bath that is capable of producing a satin nickel layer that does not exhibit any pinholes or other defects.
It is still another object of the invention to provide a nickel electroplating bath that is capable of producing a satin nickel layer on a substrate with low fingerprint sensitivity.
To that end, in one embodiment, the present invention relates generally to an aqueous nickel electroplating bath comprising:
In another embodiment, the present invention relates generally to a method of electrodepositing a satin nickel layer on a substrate, the method comprising the steps of:
The present invention relates generally to an improved nickel electroplating bath that is boric acid-free and that uses a relatively low concentration of nickel sulfate in combination with an alkylsulfonic zwitterion and nickel chloride to deposit a satin nickel layer on a substrate.
As used herein, “a,” “an,” and “the” refer to both singular and plural referents unless the context clearly dictates otherwise.
As used herein, the term “about” refers to a measurable value such as a parameter, an amount, a temporal duration, and the like and is meant to include variations of +/−15% or less, preferably variations of +/−10% or less, more preferably variations of +/−5% or less, even more preferably variations of +/−1% or less, and still more preferably variations of +/−0.1% or less of and from the particularly recited value, in so far as such variations are appropriate to perform in the invention described herein. Furthermore, it is also to be understood that the value to which the modifier “about” refers is itself specifically disclosed herein.
As used herein, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper,” and the like, are used for ease of descriptions to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It is further understood that the terms “front” and “back” are not intended to be limiting and are intended to be interchangeable where appropriate.
As used herein, the terms “comprises” and/or “comprising” specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
As used herein, the term “substantially-free” or “essentially-free,” if not otherwise defined herein for a particular element or compound, means that a given element or compound is not detectable by ordinary analytical means that are well known to those skilled in the art of metal plating for bath analysis. Such methods typically include atomic absorption spectrometry, titration, UV-Vis analysis, secondary ion mass spectrometry, and other commonly available analytical methods.
In one embodiment, the present invention relates generally to a nickel electroplating bath for depositing a nickel layer that exhibits a satin finish.
In one embodiment, the nickel electroplating bath comprises:
The at least one source of nickel ions may be selected from the group consisting of nickel sulfate, nickel carbonate, nickel chloride, nickel acetate. and combinations of one or more of the foregoing. In one embodiment, the at least one source of nickel ions comprises a combination of nickel sulfate and nickel chloride. In another embodiment, the source of nickel ions comprises a combination of nickel sulfate, nickel acetate, and nickel chloride. In one embodiment, nickel chloride is the only source of chloride ions present in the electroplating bath.
The total nickel concentration in the electroplating bath is in the range of about 40 to about 110 g/L, more preferably in the range of about 60 to about 90 g/L, and most preferably in the range of about 70 to about 80 g/L.
When present, either alone or in combination with other sources of nickel ions, the total sulfate concentration is preferably in the range of about 50 to about 130 g/L, more preferably in the range of about 70 to about 110 g/L, and most preferably in the range of about 80 to about 100 g/L.
In one embodiment, the at least one source of nickel ions comprises nickel chloride, wherein the nickel chloride is present both as a source of the at least one source of nickel ions and as the at least one source of chloride ions. In one embodiment, the nickel plating bath is at least substantially free of any other source of chloride ions.
The at least one source of chloride ions acts to increase the conductivity of the electroplating bath and reduce anode corrosion. In addition, to nickel chloride, other suitable examples of sources of chloride ions include, but are not limited to, ammonium chloride, aluminum chloride, hydrochloric acid, lithium chloride, sodium chloride, potassium chloride, rubidium chloride, cesium chloride, francium chloride, and combinations of one or more of the foregoing.
The total concentration of chloride ions in the electroplating bath (whether from nickel chloride or another suitable source of chloride ions) is preferably in the range of about 3 to about 50 g/L, more preferably in the range of about 10 to about 30 g/L, and most preferably in the range of about 15 to about 25 g/L.
The at least one source of alkylsulfonic zwitterions in the nickel electroplating bath acts as a buffering agent to the nickel. Examples of suitable sources of alkylsulfonic zwitterions include, but are not limited to, 2-aminoethane sulfonic acid (also known as taurine), 2-aminopropane sulfonic acid, N-cylcohexyl-2-aminoetane sulfonic acid (also known as CHES), N-[tri(hydroxymethyl)methyl]-3-aminopropane sulfonic acid (also known as TAPS), and combinations of one or more of the foregoing.
The concentration of alkylsulfonic zwitterions in the electroplating bath is preferably in the range of about 5 to about 50 g/L, more preferably in the range of about 10 to about 30 g/L, and most preferably in the range of about 15 to about 25 g/L.
As described herein, the nickel electroplating bath is at least substantially free of boric acid or a salt or a derivative thereof. In other words, boric acid or salts or derivatives thereof are not used in the electroplating baths of the present invention and are specifically excluded from the compositions and processes described herein.
It has been found that the replacement of boric acid with suitable alkylsulfonic zwitterions provides a technical benefit as compared to boric acid-containing nickel solutions. Alkylsulfonic zwitterions buffer the high current density area better than boric acid and avoid high current density burnings. Subsequently, the applied maximum current density for such applications is up to 50% higher compared to boric acid buffered nickel solutions.
The primary brightener creates smoother layers when the nickel is electrodeposited on the substrate, which also increases the brightness of each layer. In one embodiment, the primary brightener comprises saccharine or a salt thereof. Examples of the primary brightener include, but are not limited to, saccharine, sodium saccharine, calcium saccharine, silver saccharine, ammonium saccharine, cupric saccharine, lithium saccharine, magnesium saccharine, zinc saccharine, potassium saccharine, and combinations of one or more of the foregoing. In one embodiment, the primary brightener comprises sodium saccharine.
The concentration of the primary brightener is preferably in the range of about 1 to about 10 g/L, more preferably in the range of about 3 to about 8 g/L, and most preferably in the range of about 4 to about 6 g/L. When the concentration is either above or below the ranges, the quality of the satin nickel layer decreases.
The nickel electroplating solution also preferably includes at least one additional sulfonic acid which is included to reduce the stress of the satin nickel layer. Examples of sulfonic acids include, but are not limited to, methane sulfonic acid, vinyl sulfonic acid, allyl sulfonic acid, ethane sulfonic acid, propane sulfonic acid, propyne sulfonic acid, sulfonamides, sulfimides, N-sulfonylcarboxamides, sulfinates, and combinations of one or more of the foregoing. Further suitable sulfonic acid compounds are, for example, trisodium 1,3,6-naphthalene trisulfonate, sodium salts of allyl sulfonic acids, p-toluene sulfonic acid, p-toluene sulfonamide, sodium propargyl sulfonate, and 1,3,6-naphthalenetrisulfonic acid. In one embodiment, the at least one sulfonic acid comprises allyl sulfonic acid.
It has also been found that certain sulfonic acids are not suitable for use in a nickel electroplating bath in accordance with the present invention. Examples of these sulfonic acids include alkylsulfonic acids that are greater than 6 carbons in length. Therefore, in one embodiment, the composition described herein is at least substantially free of alkylsulfonic acids that are greater than 6 carbons in length.
The concentration of the at least one sulfonic acid in the electroplating bath is preferably in the range of about 0.5 to about 5 g/L, more preferably about 1 to about 3 g/L, and most preferably in the range of about 1.5 to about 2 g/L. When the concentration of the sulfonic acid is above this range, the quality of the satin nickel layer decreases. When the concentration is below this range, the satin nickel layer is less durable and is more susceptible to cracks and other defects.
The at least one source of polymer acts as the primary satin effect generator in the nickel solution. Depending on other bath parameters, including, for example specific gravity, temperature, nickel concentration, and pH, the polymers agglomerate forming distinct emulsion droplets. The average size of those droplets directly correlates with the satin structure of the deposit. The size of those droplets and satin structures depends on bath solution parameters as well as on chemical character and chain length of the polymers.
The at least one polymer includes, but is not limited to, high-chain length polyethylene glycols (hereinafter “PEG”), low-chain length PEG derivatives, high-chain length polypropylene glycols (hereinafter “PPG”), low-chain length PPG derivatives, and copolymer combinations of one or more of the foregoing. The high-chain length polymers have a molecular weight in the range of about 10,000 to about 100,000 g/mol, while the low-chain length polymers have a molecular weight in the range of about 75 to about 10,000 g/mol. Copolymer combinations of PEGs and PPGs and/or their derivatives have a molecular weight in the range of about 1,000 to about 10,000 g/mol. Specific examples of these polymers include PEG 400, PEG 10,000, PEG 20,000, PEG 35,000, PPG, 750, PPG 2,000, copolymer with molar weight of 8000 (20% PPG), or copolymer 1200 (80% PPG).
It has also been found that PEG and/or PPG derivatives with quaternary benzyl or alkyl amine end groups are not suitable in a nickel electroplating bath in accordance with the present invention. Therefore, in one embodiment, the composition is at least substantially free of PEG and/or PPG derivatives with quaternary benzyl or alkyl amine end groups.
The concentration of the at least one polymer is in the range of about 0.001 to about 1 g/L, more preferably in the range of about 0.005 to about 0.2 g/L, and most preferably in the range of about 0.01 to about 0.075 g/L.
In a preferred embodiment of the present invention, the nickel electroplating bath is at least substantially free and is preferably completely free of any other metal ion other than the nickel ion source(s) that are always contained in the electroplating bath described herein, which can be electrolytically deposited together with the nickel ion source as nickel alloy layer.
The nickel electroplating bath described herein also optionally, but preferably, contains at least one wetting agent. If present, the at least one wetting agent helps to create a more desirable satin finish. The at least one wetting agent can be used alone or in combination with at least one additional brightener. Examples of suitable wetting agents include, but are not limited to, linear alkylsulfates with less than 18 carbons, branched alkylsulfates with less than 18 carbons, carboxylic sulfonic acid acids where the ester group is below the 12th carbon, fatty alcohol sulfated ethoxylates, naphthalene sulfonates, 2-ethylhexysulfate, di-alkylsulfosuccinate, polymerized naphthalenesulfonate, lauryl sulfate, lauryl ether sulfate, and combinations of one or more of the foregoing.
On the other hand, certain wetting agents such as fluorinated wetting agents and alkylphenol ethoxylates are not suitable in a nickel electroplating bath in accordance with the invention. Therefore, in one embodiment, the nickel electroplating composition described herein is at least substantially free of any fluorinated wetting agents and/or alkylphenol ethoxylates.
When present, the concentration of the at least one wetting agent is preferably in the range of about 0.01 to about 1 g/L, more preferably about 0.05 to about 0.5 g/L, and most preferably in the range of about 0.1 to about 0.3 g/L.
The electroplating bath also optionally, but preferably, contains at least one additional brightener. Examples of suitable brighteners include, but are not limited to, sulfobetaines such as pyridinium propyl sulfobetaine, propargyl alcohols and derivatives (including ethoxylate, propoxylate, and amine derivatives), butynedioles and derivatives (including ethoxylate, propoxylate, and amine derivatives), hexynediols, dioles, and combinations of one or more of the foregoing.
When present, the concentration of the at least one additional brightener is preferably in the range of about 0.01 to about 1 g/L, more preferably in the range of about 0.05 to about 0.5 g/L, and most preferably in the range of about 0.1 to about 0.3 g/L.
The nickel electroplating bath is typically maintained at a slightly elevated temperature, such as a temperature within the range of about 30 to about 70° C., more preferably in the range of about 40 to about 60° C., and most preferably in the range of about 45 to about 55° C. while the substrate is immersed in or otherwise contacted with the nickel electroplating bath. When the temperature exceeds the upper limit, the electroplating bath becomes ineffective in plating the satin nickel layer. When the temperature is below the lower limit, the deposition rate slows to an ineffective pace.
The pH of the nickel electroplating bath of the present invention is preferably maintained in the range of about 2.5 to about 5.5, more preferably in the range of about 3.0 to about 4.5, and most preferably in the range of about 3.5 to about 4.0. In one embodiment, the pH is maintained at the desired level with the addition of sulfuric or hydrochloric acid.
The nickel electroplating bath also typically has a specific gravity value within the range of about 1.05 to about 1.35 g/cm3, more preferably within the range of about 1.1 to about 1.3 g/cm3, and most preferably in the range of about 1.15 to about 1.25 g/cm3.
In particular, it is preferred that the nickel electroplating bath is at least substantially-free, and is preferably completely free of any gold, copper, bismuth, tin, zinc, silver, lead, and aluminum ion source.
By “at least substantially free” what is meant is that the concentration of any other metal ions is less than 1 g/L, preferably less than 0.1 g/L, and more preferably less than 0.01 g/L.
It has been found that iron and cobalt do not disturb the satin plating effect in the invented nickel bath solution. However, greater than 30% of these elements in the deposits do reduce the corrosion resistance of the deposited layers significantly.
The nickel electroplating bath may be periodically or continuously monitored to maintain the concentrations of the bath constituents within the desired range.
In one embodiment, the present invention relates generally to an aqueous nickel electroplating bath comprising:
In another embodiment, the present invention relates generally to an aqueous nickel electroplating bath consisting essentially of:
In another embodiment, the present invention relates generally to an aqueous nickel electroplating bath consisting essentially of:
By “consisting essentially of,” what is meant is that the nickel electroplating bath is free of any additives that would prevent the bath from producing the desired satin finish and/or destroy or materially alter the satin finish. These additives include, for example, alkylsulfonic acids that are greater than 6 carbons in length, include fluorinated wetting agents, alkylphenol ethoxylates, PEG and/or PPG derivatives with quaternary benzyl or alkyl amine end groups, and boric acid.
In yet another embodiment, the present invention relates generally to an aqueous nickel electroplating bath consisting of:
In another embodiment, the present invention also relates generally to a method of electroplating a nickel layer exhibiting a satin finish onto a substrate, the method comprising the steps of:
The nickel electroplating bath is configured to electrodeposit a satin nickel layer on a variety of substrates, including both conductive and semiconductive substrates. Examples of the substrate include, but are not limited to, magnesium, aluminum, copper, zinc, brass, bronze, steel, vanadium, chromium, manganese, iron, cobalt, nickel, rubidium, rhodium, palladium, silver, indium, tin, antimony, tellurium, rhenium, platinum, gold, thallium, bismuth, various plastics, and combinations of one or more of the foregoing. In one embodiment, the substrate is a copper or a copper alloy substrate such as brass or bronze.
Prior to the electrodeposition step, the substrate can be pre-treated. In one embodiment, the pre-treatment steps include degreasing and acid cleaning with one or more rinse steps performed therebetween. After pre-treatment, the substrate is immersed in or otherwise contacted with the nickel electroplating bath. In one embodiment, the substrate is arranged in an electrolytic cell where the substrate acts as the cathode. The at least one anode may comprise a nickel anode.
The pH of the electroplating bath is maintained in the range of about 2.5 to about 5.5, more preferably in the range of about 3.0 to about 4.5, and most preferably in the range of about 3.5 to about 4.0. The pH is maintained by the addition of sulfuric acid, hydrochloric acid, and combinations of one or more of the foregoing.
The current density is preferably maintained within the range of about 0.1 to about 25 A/dm2, more preferably within the range of about 1 to about 15 A/dm2, and most preferably in the range of about 3 to about 10 A/dm2.
The substrate is contacted with the nickel electroplating bath for a period of time to plate a desired thickness of the satin nickel layer on the substrate. In one embodiment, the desired thickness is in the range of about 2 to about 30 μm, more preferably in the range of about 5 to about 20 μm, and most preferably in the range of about 10 to about 15 μm.
The plating time is the time required to achieve the desired thickness. In one embodiment, the sufficient plating time of the nickel layer is preferably in the range of about 2 to about 30 minutes, more preferably about 5 to about 20 minutes, and most preferably about 10 to about 15 minutes.
In order to determine if a desirable satin finish was obtained, the product, consisting of the substrate with the electrodeposited nickel layer thereon, is evaluated to measure gloss units when measured at a 60° angle. The gloss value is measured by using a glossmeter, such as a Novo-Gloss 60 Glossmeter, to evaluate the amount of reflected light sent by a beam of light from the glossmeter at a 60° angle. In one embodiment, the gloss units of the satin finish are in the range of about 5 to about 500 GU and more preferably in the range of about 20 to about 100 GU.
It is highly desirable for the satin finish to not have any pinholes or defects in the plated nickel layer, as this can cause appearance and structural deficiencies. Therefore, in one embodiment, the satin finish is at least substantially free of any pinholes or other defects.
The surface roughness average Ra can be calculated and is an indication of the fingerprint sensitivity of the satin finish. The surface roughness average Ra is calculated by observing the substrate under a 400× magnification, using a profilometer, such as a Surface Roughness Tester, and evaluating the difference in height between the peaks and valleys of the surface profile. Alternatively, the surface roughness average Ra can be measured according to ASTM D4417-21 (2021), which is a standard test method for surface roughness average Ra using a Surface Roughness Tester. To achieve low-fingerprint sensitivity in a satin nickel layer, the surface roughness average Ra is less than about 10 μm, more preferably in the range of about 0.3 to about 5.0 μm, and most preferably in the range of about 1.0 to about 2.5 μm.
The present invention will now be illustrated with reference to the following non-limiting examples:
A substrate was immersed in the following nickel electroplating bath:
The temperature of the bath was maintained at 52° C. and the pH of the solution was maintained at about 3.8. The nickel layer was deposited in 10 minutes with a current density of 5 A/dm2 to achieve a desired thickness of 10 μm.
Under the above described parameters a screening test of concentration from 0.5 mg/l to 10.0 mg/l and two different chain lengths of PEGs was made. The resulting nickel layer was observed to have no defects and a satin finish that was characterized by a gloss measurement at 60° angle with Konica Minolta Multigloss 246 plus and an average surface roughness Ra measurement at 400× magnification under a 3D laser microscope from Keyence.
The satin finishes were uniform and in the desired limits of 60° GU between 5 to 500 and average roughness Ra between 0.3 to 5.0 μm, if PEG concentration was ≥1 mg/l, shown in
A substrate was immersed in the following nickel electroplating bath:
The temperature of the bath was maintained at 52° C. and the pH of the solution was maintained at about 3.8. The nickel layer was deposited in 10 minutes with a current density of 5 A/dm2 to achieve a desired thickness of 10 μm.
The resulting nickel layer was observed to have no defects and a satin finish that was calculated to have both a gloss value of 22 GU when observed at a 60° angle and a surface roughness average Ra of 1.1 μm. A microscope image depicting the satin finish is shown in
25 mg/L 2-ethylhexylsulfate was added as the wetting agent to the nickel electroplating bath of Example 2. In addition, 25 mg/L pyridinium propyl sulfobetaine and 125 mg/L ethoxylated butynediole were added as brighteners. A brass panel was plated under same parameter settings as in Example 2.
The wetting agent and the brighteners were able to reduce the fingerprint sensitivity of the satin finish due to the increased average roughness. The satin finish now has a gloss value of 53 GU when observed at a 60° angle and a surface roughness average Ra of 2.2 μm. A microscope image depicting the satin finish is shown in
A substrate was immersed in the following basic nickel electroplating bath:
The temperature of the bath was maintained at 48° C. and the pH of the solution was maintained at about 3.8. The nickel layer was deposited in 8 minutes with a current density of 6 A/dm2 to achieve a desired thickness of 10 μm. In each solution, two identical brass panels were plated exactly 1 hour after the make-up of the solution and 4 hours after the make-up without adding further chemicals. The gloss unit data, average roughness data, and observation of appearance are listed in Table 1 below:
1hcd = high current density
As seen in Table 1, only taurine and N-[tri(hydroxymethyl)methyl]-3-aminopropane sulfonic acid (TAPS) performed in a desired manner. The natural change of the satin finish over the time is illustrated in
A substrate was immersed in the following nickel electroplating bath:
The temperature of the bath was maintained at 52° C.′ and the pH of the solution was maintained at about 3.8. The nickel layer was deposited in 10 minutes with a current density of 5 A/dm2 to achieve a desired thickness of 10 μm.
This electroplating bath uses a polymer wither quaternary amine ends groups and it is demonstrated that the resulting nickel layer was unsuitable for a desirable satin effect. This was shown by a bright finish a lot of large defects, with a calculated gloss value of 890 GU when observed at a 60° angle and a surface roughness average Ra of 0.12 μm. The satin finish described in this example is illustrated by
A substrate was immersed in the following nickel electroplating bath:
The temperature of the bath was maintained at 52° C. and the pH of the solution was maintained at about 3.8. The nickel layer was deposited in 10 minutes with a current density of 5 A/dm2 to achieve a desired thickness of 10 μm.
This electroplating bath uses a fluorinated wetting agent and it is demonstrated that the resulting nickel layer was unsuitable for a desirable satin effect. This was shown by a bright finish a lot of large defects, with a calculated gloss value of 1080 GU when observed at a 60° angle and a surface roughness average Ra of 0.05 μm. The satin finish described in this example is illustrated by
As shown by the Examples, nickel electroplating baths utilizing a low concentration of nickel, the buffering agents, and additives described herein are capable for depositing a satin nickel layer without using boric acid. The electroplating baths described herein also reduce the fingerprint sensitivity of the finished product.
Comparative Examples 5 and 6 demonstrate that certain additives, including polymers with quaternary amine end groups and fluorinated wetting agents have a negative effect on the properties of the nickel deposit and are not capable of producing the desired satin effect.
The nickel electroplating method described herein can be used for electrodepositing a nickel layer on various metal or plastic substrates that exhibits a satin finish.
Embodiment 1: An aqueous nickel electroplating bath comprising:
Embodiment 2: The nickel electroplating bath according to Embodiment 1 wherein the bath is at least substantially free of boric acid or a salt or a derivative thereof.
Embodiment 3: The nickel electroplating bath according to Embodiment 1 or Embodiment 2, wherein the at least one source of alkylsulfonic zwitterions is selected from the group consisting of 2-aminoethane sulfonic acid, 2-aminopropane sulfonic acid, N-cylcohexyl-2-aminoetane sulfonic acid, N-[tri(hydroxymethyl)methyl]-3-aminopropane sulfonic acid, and combinations of one or more of the foregoing.
Embodiment 4: The nickel electroplating bath according to any of the preceding Embodiments, wherein the bath is maintained at a pH in the range of about 2.5 to about 5.5, optionally wherein the pH is maintained with sulfuric acid, hydrochloric acid, or combinations thereof.
Embodiment 5: The nickel electroplating bath according to any of the preceding Embodiments, wherein the bath is maintained at a temperature in the range of about 30 to about 70° C.
Embodiment 6: The nickel electroplating bath according to any of the preceding Embodiments, wherein the at least one source of nickel ions is selected from the group consisting of nickel sulfate, nickel chloride, and combinations of the foregoing, optionally wherein the at least one source of nickel ions comprises nickel chloride, wherein the nickel chloride provides a source of the at least one source of nickel ions and a source of the at least one source of chloride ions.
Embodiment 7: The nickel electroplating bath according to Embodiment 6, wherein the bath is at least substantially free of any other source of chloride ions.
Embodiment 8: The nickel electroplating bath according to any of the preceding Embodiments, wherein the primary brightener is selected from the group consisting of saccharine, sodium saccharine, calcium saccharine, silver saccharine, ammonium saccharine, cupric saccharine, lithium saccharine, magnesium saccharine, zinc saccharine, potassium saccharine, and combinations of one or more of the foregoing, optionally wherein the primary brightener comprises sodium saccharine.
Embodiment 9: The nickel electroplating bath according to any of the preceding Embodiments, wherein the sulfonic acid is selected from the group consisting of methane sulfonic acid, vinyl sulfonic acid, allyl sulfonic acid, ethane sulfonic acid, propane sulfonic acid, propyne sulfonic acid, sulfonamides, sulfimides, N-sulfonylcarboxamides, sulfinates, and combinations of one more of the foregoing, optionally wherein the sulfonic acid comprises allyl sulfonic acid.
Embodiment 10: The nickel electroplating bath according to any of the preceding Embodiments, wherein the at least one polymer is selected from the group consisting of a high-chain length polyethylene glycol, a low-chain polyethylene glycol derivative, a long-chain length polypropylene glycol, a low-chain length polypropylene glycol derivative, and combinations of one or more of the foregoing.
Embodiment 11: The nickel electroplating bath according to any of the preceding Embodiments, wherein the at least one wetting agent is present in the bath, and is selected from the group consisting of linear alkylsulfates with less than 18 carbons, branched alkylsulfates with less than 18 carbons, carboxylic sulfonic acid acids where the ester group is below the 12th carbon, fatty alcohol sulfated ethoxylates, naphthalene sulfonates, 2-ethylhexysulfate, di-alkylsulfosuccinate, polymerized naphthalenesulfonate, lauryl sulfate, lauryl ether sulfate, and combinations of one or more of the foregoing, and/or wherein the at least one additional brightener is present in the bath and is selected from the group consisting of pyridinium propyl sulfobetaine, sulfobetaines, propargyl alcohols and derivatives thereof, butynedioles and derivatives thereof, hexynedioles, and combinations of one or more of the foregoing.
Embodiment 12: The nickel electroplating bath according to any of the preceding Embodiments, wherein a total concentration of nickel is in the range of about 40 to about 110 g/L, preferably wherein the total concentration of nickel is in the range of about 60 to about 90 g/L.
Embodiment 13: A method of electrodepositing a satin nickel layer onto a substrate, the method comprising the steps of:
Embodiment 14: The method according to Embodiment 13, wherein the substrate is pre-treated prior to step a), optionally wherein the pre-treating step includes degreasing and acid cleaning.
Embodiment 15: The method according to Embodiment 13 or Embodiment 14, wherein the substrate is selected from the group consisting of magnesium, aluminum, copper, zinc, brass, bronze, steel, vanadium, chromium, manganese, iron, cobalt, nickel, rubidium, rhodium, palladium, silver, indium, tin, antimony, tellurium, rhenium, platinum, gold, thallium, bismuth, various plastics, and combinations of one or more of the foregoing.
Embodiment 16: The method according to any of Embodiments 13 to 15, wherein the at least one anode comprises a nickel anode, optionally wherein the current applied to the substrate has a current density in the range of about 0.1 to about 25 A/dm2.
Embodiment 17: The method according to any of Embodiments 13 to 16, wherein the deposited nickel layer has a thickness in the range of about 2 to about 30 μm.
Embodiment 18: A substrate having a satin nickel layer thereon made by the method of any of Embodiments 13 to 17.
Embodiment 19: The substrate according to Embodiment 18, wherein the satin nickel layer exhibits a gloss value in the range of about 5 to about 500 GU when measured at a 60° angle, preferably wherein the gloss value is in the range of about 20 to about 100 GU when measured at a 60° angle.
Embodiment 20: The substrate according to Embodiment 18 or Embodiment 19, wherein the satin nickel layer is at least substantially free of any pinholes and defects.
Embodiment 21: The substrate according to any of Embodiments 18 to 20, wherein the satin nickel layer exhibits a surface roughness average less than 10 μm, preferably wherein the surface roughness average of the satin nickel layer is in the range of about 0.3 to about 5.0 μm, more preferably wherein the surface roughness average of the satin nickel layer is in the range of about 1.0 to about 2.5 μm.
Finally, it should also be understood that while the present invention has been described and illustrated by reference to particular embodiments, the claims are intended to cover all of the generic and specific features of the invention described herein and all statements of the scope of the invention that as a matter of language might fall there between.
