Electroless nickel plating process for copper or copper alloy components
Patent Information
- Application Number
- PCT/IB2025/052053
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2025-02-26
- Publication Date
- 2026-09-03
Abstract
Description
"ELECTROLESS NICKEL PLATING PROCESS FOR COPPER OR COPPER ALLOY COMPONENTS"DESCRIPTIONField of application
[0001] The present invention relates to an electroless nickel plating process for copper or copper alloy components .
[0002] In particular, the process according to the present invention is optimal for applications on copper alloy components that subsequently require joining operations with fusion or partial fusion of the interfaces .
[0003] The process according to the invention improves the reliability of the coating process and offers increased adhesion to the copper base, proving more economical than conventional methods . The process in actual fact allows for reliable, high-productivity deposition without the use of expensive materials .
[0004] In particular, the process according to the present invention may be used to obtain a surface with excellent weldability properties upon copper or copper alloy components .Prior art
[0005] The main metal alloys used in precision mechanics are iron, aluminum and copper alloys, by virtue of their mechanical features, availability, cost-effectiveness andeasy workability. Market and technology developments have inevitably led to research and demand for ever-improving features, including surface features .
[0006] The three classes of alloys mentioned above often have insufficient surface characteristics, such as, for example, corrosion resistance or wear resistance . It is therefore very often necessary to increase some surface features by applying coatings that may meet various technical and / or aesthetic requirements .
[0007] Electroless nickel plating is the coating that lends itself most to being applied to precision mechanical pieces insofar as it combines multiple features, such as, for example : thickness uniformity, increased hardness, wear resistance and excellent corrosion resistance .
[0008] The electroless nickel plating process is carried out by immersion in a nickel solution by means of a chemical self-catalytic reaction process, without the use of an electric current . A nickel phosphorus alloy is deposited upon the surface of the workpiece by means of the oxidation-reduction reaction between the Ni++ cation given by a source of nickel (in the form of nickel salts, such as nickel sulfate, nickel chloride, nickel acetate) and the H2PO2 anion originating from the sodium hypophosphite (reducing agent) .
[0009] This process makes it possible to have a coating withuniform and calibrated thicknesses on all surfaces, including the inner surfaces and with complex geometries . This allows strict tolerances to be met without requiring isolation or reworking of tolerance critical surfaces . The complete coating of the workpiece also allows all inner surfaces such as cylinders, channels, connectors and the distributors of air, water, steam or medical gases to be protected from corrosion and wear .
[0010] In galvanic processes (also called electrolytic processes) , such as chromium plating or electrolytic nickel plating, on the other hand, an electric current is used for the deposition of the metal coating, which inevitably leads to greater thicknesses at the edges and difficulties in coating the inner areas .
[0011] As is known, however, copper and the alloys thereof do not have catalytic characteristics for electroless nickel plating.
[0012] In order to overcome such limitation and thus be able to perform electroless nickel plating on copper alloys, and especially pure copper, a plurality of techniques are adopted that render the copper catalytic :
[0013] - Contact with catalytic metals (iron, etc . ) : this is a technique that is not particularly repeatable or reliable and that involves the risk of resulting in a low-adhesion coating;
[0014] - Pre-electroless nickel strike plating on an electrolytic nickel coating: this is a technique that involves the deposition, by means of an electric current, of a layer of nickel from an additional electrolytic solution before the electroless nickel plating; in the presence of complex holes or geometries it does not allow for the complete and uniform coating of the component; it reduces productivity thereby increasing costs .
[0015] - Triggering of the reaction by means of an electric current : this is a technique that provides for initially triggering the electroless nickel plating by means of the application of an electric current; in the presence of complex holes or geometries it does not allow for the complete and uniform activation of the reaction upon the surface of the component; it reduces productivity and therefore increases costs;
[0016] - Activation using noble metals such as palladium: this is an expensive technique and nonetheless involves the risk of obtaining a low-adhesion coating;
[0017] - Electroless nickel strike plating using formulations containing strong reducing agents based on boron or hydrazine : this is a technique that uses boron or hydrazine based reducing agents which are respectively problematic for the environment (wastewater treatment) and carcinogenic;
[0018] - Chloride-based electroless nickel strike plating: this is a technique that involves the use of nickel chloride with the formation of hydrochloric acid at an acidic pH, for bath operations; the presence of volatile acid poses safety problems for the operator; the management of the process is difficult due to the variation of the quality of the treatment due to the fact that the solution is eventually depleted.
[0019] There is therefore a still completely unsatisfied need to have a process for the electroless nickel plating of copper or copper alloy components that is at the same time repeatable, ensures high productivity, does not use expensive metals and allows for the implementation of a coating with high adhesion to the base material .
[0020] Another requirement is to obtain a surface having weldability and chemical resistance properties on copper or copper alloy components by means of an electroless nickel plating process . In particular, the surface has to be weldable and / or braze weldable and must have chemical resistance in order to maintain oxidation resistance and ensure resistance from corrosion originating at the base layer .Disclosure of the invention
[0021] The main obj ect of the present invention is therefore to eliminate or at least mitigate the drawbacks of theaforementioned prior art by providing an electroless nickel plating process for copper or copper alloy components that is at the same time repeatable, ensures high productivity, does not use expensive metals and allows for the implementation of a coating with high adhesion to the base material .
[0022] A further obj ect of the present invention is to provide an electroless nickel plating process for copper or copper alloy components that allows a surface having weldability and chemical resistance properties to be obtained .
[0023] The technical features of the invention, according to the aforesaid obj ects, may be clearly seen from the content of the claims below, and the advantages thereof will become more apparent in the detailed description that follows . Detailed description
[0024] The present invention relates to an electroless nickel plating process for copper or copper alloy components .
[0025] According to a general embodiment of the invention, the electroless nickel plating process for copper or copper alloy components comprises the following operating steps :
[0026] a) providing a copper or copper alloy component;
[0027] b) cleaning the surface of said component by performing at least one treatment for the removal of anyoxides ;
[0028] c) depositing the nickel alloy upon the surface subj ect to cleaning of said component .
[0029] Said cleaning step b) preferably comprises acid pickling in order to remove any inorganic contaminants, oxides, and the passivation layer from the surface of the component . The acid pickling is followed by rinsing.
[0030] Advantageously, said cleaning step b) may comprise one or more of the following treatments to be performed before the acid picking:
[0031] - washing using an organic solvent in order to remove any oils, fats, organic contaminants, dust and / or particles from the surface;
[0032] - washing using an aqueous solution containing surfactants and / or alkali components in order to remove any oils, fats, organic contaminants, dust and / or particles from the surface;
[0033] - alkaline pickling in order to remove any organic or inorganic contaminants which are soluble in alkaline solutions from the surface .
[0034] Said treatments are preferably followed by a surface rinse .
[0035] Advantageously, said cleaning step b) may comprise further alkaline pickling followed by rinsing to be performed after the acid pickling and the subsequentrinsing .
[0036] The aforesaid step c) involves immersing said component as a whole, or at least in part, in a bath containing a first solution of nickel sulfate (Ni SO4 ) and hypophosphite ions (H2Po2-) .
[0037] According to the invention, said first solution comprises :
[0038] - nickel sulfate (Ni SO4 ) with a concentration of Ni2+ ions of between 20 and 300 mmol / 1, preferably of between 30 and 130 mmol / 1;
[0039] - hypophosphite ions (H2Po2-) with a concentration of between 100 and 1000 mmol / 1, preferably of between 300 and 700 mmo 1 / 1 ;
[0040] - complexing agents and pH buffers with a concentration of between 50 and 1000 mmol / 1, preferably of between 200 and 600 mmol / 1;
[0041] - one or more organic sulfur compounds, with a concentration of between 0.005 and 0. 100 mmol / 1 ; and
[0042] - one or more betaine-based surfactants, with a concentration of between 0.050 and 0.500 mmol / 1.
[0043] According to the invention, said first solution is maintained at a temperature of between 70°C and 105°C with a pH of between 3 and 6.
[0044] Such step c) leads to the formation upon said copper or copper alloy component of a base layer of nickelphosphorus directly on the surface of said component that is exposed to said bath.
[0045] It has been possible to verify that the electroless nickel plating process for copper or copper alloy components according to the invention makes it possible to produce a nickel phosphorus coating with high adhesion to the base material directly on the surface of the component :
[0046] - without the need to use catalytic metals such as iron;
[0047] - without the need to activate the surface using noble metals such as palladium;
[0048] - without triggering by means of an electric current;
[0049] - without providing pre-electroless nickel plating treatments other than surface cleaning treatments;
[0050] - without the need to use strong reducing agents based on boron or hydrazine;
[0051] - without the need to use nickel chloride .
[0052] Conversely, by virtue of the invention, by using a bath containing said first solution, the nickel-phosphorus coating is deposited directly upon the surface and spontaneously .
[0053] The process according to the invention is at the same time repeatable, ensures high productivity and is less expensive than traditional processes .
[0054] We will now go into detail as regards the functionperformed by the individual components of the first solution .
[0055] Hypophosphite ions are essential for the reduction of nickel metal Ni2+ ions and for the incorporation of phosphorus into the coating that forms the aforesaid base layer .
[0056] Hypophosphite ions act as reducing agents in the redox reaction of the nickel ion reduction to nickel metal, yielding electrons and transforming themselves into orthophosphite ions . During the deposition reaction, a part of the hypophosphite ions is oxidized to elemental phosphorus, which codeposits into the coating thereby creating the Ni-P alloy.
[0057] The complexing agents and pH buffers facilitate pH control and influence the morphology and properties of the coating .
[0058] More specifically, the complexing agents and the pH buffers regulate the availability of metal ions in solution and stabilize the optimal chemical conditions for the reaction. The complexing agents, by forming complexes with Ni++ ions, avoid the formation of insoluble nickel salts and regulate the kinetic availability of Ni++ ions for the reaction by adjusting the deposition rate and ensuring uniform deposition.
[0059] The pH buffers allow the pH to be adjusted whileavoiding strong pH variations that could compromise the quality and uniformity of the coating .
[0060] The complexing agents and pH buffers preferably consist of a combination of weak acid ions, preferably organic .
[0061] Said weak acids are preferably selected from the group consisting of : formic acid, propionic acid, boric acid, citric acid, succinic acid, acetic acid and malic acid.
[0062] Said one or more organic sulfide compounds have the function of both stabilizers and accelerators in the deposition reaction.
[0063] In particular, it was possible to verify that organic sulfur compounds :
[0064] - facilitate the chemical reduction of Ni2+ ions which is necessary for the deposition of nickel; and
[0065] - accelerate the coating process .
[0066] In particular, organic sulfide compounds prevent decomposition of the treatment solution, i . e . , the spontaneous reaction of oxidation and reduction of the nickel ions and hypophosphite ions within the solution itself and not upon the surfaces of the pieces to be treated .
[0067] Said one or more betaine-based surfactants act as complexing agent, thereby optimizing the chemical environment for the formation of the coating. Inparticular, they improve the deposition of nickel upon the surface of the copper by forming stable and soluble complexes with the nickel ions, thus facilitating controlling the nickel deposition rate .
[0068] The process according to the invention is therefore based upon the combined action of organic sulfur compounds and betaine-based surfactants .
[0069] More specifically, the combined action of organic sulfur compounds and betaine-based surfactants allows for direct deposition upon copper alloy surfaces, an outcome that would not be possible without the synergy of such compounds .
[0070] In particular, organic sulfur compounds make it possible to create reactive sites upon the copper alloy, thereby favoring the triggering of the deposition of the nickel . However, by themselves they are not sufficient to create sufficient active sites upon the surface for the triggering of the deposition.
[0071] The betaine-based surfactants, on the other hand, play a fundamental role in complexing and stabilizing the nickel ions in solution, maintaining the correct concentration thereof and favoring a homogeneous and regular deposition. The nature thereof also contributes to reducing surface tension, improving the wettability of the substrate and making the distribution of the coatinguniform. In the absence of betaine-based surfactants, organic sulfide compounds alone would not be capable of generating the active sites necessary for the nickel coating to form spontaneously and adherently.
[0072] The combination of organic sulfide compounds and betaine-based surfactants thus ensures an essential synergy: the former chemically prepare the surface of the copper alloy, generating sites that are suitable for nickel adhesion; the latter stabilize metal ions, regulate the deposition and improve wettability. In this way, it becomes possible to perform the direct deposition of nickel upon copper alloy surfaces without resorting to intermediate treatments or to additional activation agents .
[0073] According to a preferred embodiment of the invention, said first solution comprises thiourea as an organic sulfide compound with a concentration of between 0.005 and 0.100 mmo 1 / 1 .
[0074] As an alternative to thiourea, one or more compounds selected from one or more of the following classes of compounds may be used as an organic sulfide compound with a concentration of between 0.005 and 0.100 mmol / 1 :
[0075] - Mercaptans : preferably Mercaptobenzothiazole;
[0076] - Thiazoline : preferably 2-methylbenzothiazoline;
[0077] - Dithiocarbamates : preferably Diethyldithiocarbamate .
[0078] According to a preferred embodiment of the invention, said first solution comprises cocamidopropyl betaine as a betaine-based surfactant with a concentration of between 0.050 and 0.500 mmol / 1.
[0079] As an alternative to cocamidopropyl betaine, one or more of the following compounds may be used as a betainebased surfactant with a concentration of between 0.050 and 0.500 mmol / 1 : lauryl betaine, lauramidopropyl betaine, N-oleyl betaine .
[0080] The first solution may also contain nickel acetate in addition to nickel sulfate as a source of Ni2+ ions .
[0081] Preferably, said first solution further comprises ammonium (NH4+) with a concentration of NH4+ ions of between 20 and 600 mmol / 1, preferably of between 20 and 400 mmol / 1. The presence of ammonium ions contributes to the ionic balance of the solution thereby acting as a nickel complexing agent .
[0082] In particular, the ammonium ions allow for the creation of soluble stable compounds [Ni (NH3 ) 6 ] ++ . This prevents the formation of insoluble nickel compounds, such as nickel hydroxide . During the nickel plating process, the pH tends to lower due to the deposition reaction residues . It is therefore necessary to provide for pH adjustment by dosing alkaline solutions ( for example, a solution of sodium hydroxide or potassium carbonate) . Atthe dosage point of these solutions the local pH may rise to values greater than 5, which may trigger the formation of nickel hydroxide in the absence of ammonium ions . Said first solution preferably further comprises one or more stabilizing agents selected from the group consisting of :
[0083] - compounds of the elements of the Group VI, Se, S, and Te
[0084] - oxyanions, preferably selected from the group consisting of As02-, IO3-, Mo042-
[0085] - heavy metal ions, preferably selected from the group consisting of Sn2+, Pb2+, Cu2+, Bi3+, Sb3+, T1+ .
[0086] The stabilizers have the function of preventing the decomposition of the solution. Nickel baths are in fact metastable .
[0087] As will be taken up later in the description, it is possible to adjust the phosphorus content within the coating by acting on the concentration and type of stabilizer .
[0088] The first solution may contain only one of the aforesaid stabilizing agents . In such a case, the stabilizing agent is present at the following concentrations :
[0089] - between 0.005 and 0.100 mmol / 1 if the stabilizer is selected from the compounds of the elements of the group VI, Se, S, and Te
[0090] - between 2 and 2000 mmol / 1 if the stabilizer is selected from oxyanions, preferably selected from the group consisting of AsO2-, IO3-, Mo042-
[0091] - between 0.0005 and 0.0500 mmol / 1 if the stabilizer is selected from heavy metal ions, preferably selected from the group consisting of Sn2+, Pb2+, Cu2+, Bi3+, Sb3+, T1+ .
[0092] Alternatively, the first solution may contain a combination of two or more of the aforesaid stabilizing agents . In this case, the concentration of the specific stabilizing agent used in combination may vary with respect to the case of using a single stabilizer and is selected according to criteria known per se to a person skilled in the art .
[0093] Advantageously, the nickel-plating process may further comprise a step d) of depositing the nickel alloy upon the base layer of nickel phosphorus to obtain a top layer of nickel phosphorus .
[0094] Operationally, the deposition of nickel upon the base layer may be conducted according to any suitable methodology for the purpose, there no longer being the constraint of the non-catalytic nature of the copper .
[0095] In particular, said step d) may include submerging all or at least part of said component in a bath containing a second solution of nickel sulfate (Ni SO4 ) andhypophosphite ions (H2Po2-) .
[0096] Preferably, said second solution may be the same as the first solution, with the only difference being that it does not necessarily have to contain one or more organic sulfur compounds and one or more betaine-based surfactants .
[0097] Said second solution preferably comprises :
[0098] - nickel sulfate (Ni SO4 ) with a concentration of Ni2+ ions of between 20 and 300 mmol / 1, preferably of between 30 and 130 mmol / 1;
[0099] - hypophosphite ions (H2Po2-) with a concentration of between 100 and 1000 mmol / 1, preferably of between 300 and 700 mmo 1 / 1 ;
[0100] - complexing agents and pH buffers with a concentration of between 50 and 1000 mmol / 1, preferably of between 200 and 600 mmol / 1, preferably a combination of weak acid ions .
[0101] Similarly to what has been anticipated for the first solution, the second solution is also maintained at a temperature of between 70°C and 105°C with a pH of between 3 and 6.
[0102] The first solution may also contain nickel acetate in addition to nickel sulfate as a source of Ni2+ ions .
[0103] Preferably, said second solution furthercomprises ammonium (NH4+) with a concentration of NH4+ ions between 20 and 600 mmol / 1, preferably between 20 and 400 mmol / 1. The presence of ammonium ions contributes to the ionic balance of the solution thereby acting as a nickel complexing agent .
[0104] Said second solution further preferably comprises one or more stabilizing agents selected from the group consisting of :
[0105] - compounds of the elements of the Group VI, Se, S, and Te
[0106] - oxyanions, preferably selected from the group consisting of AsO2-, IO3-, Mo042-
[0107] - heavy metal ions, preferably selected from the group consisting of Sn2+, Pb2+, Cu2+, Bi3+, Sb3+, T1+ .
[0108] Also in this case, the stabilizers have the function of preventing the decomposition of the solution. Nickel baths are in fact metastable .
[0109] As will be taken up later in the description, it is possible to adjust the phosphorus content within the coating by acting on the concentration and type of stabilizer .
[0110] Similarly to the first solution, the second solution may also contain only one of the aforesaid stabilizing agents . In this case, the stabilizing agent is present at the same concentrations that have already beenindicated for the first solution.
[0111] Alternatively, the second solution may contain a combination of two or more of the aforesaid stabilizing agents . In this case, the concentration of the specific stabilizing agent used in combination may vary with respect to the case of using a single stabilizer and is selected according to criteria known per se to a person skilled in the art .
[0112] Preferably, the process comprises a step of adjusting the concentration of said one or more stabilizers in the first and / or second solution according to the phosphorus content to be obtained within the base layer of nickel phosphorus and within the top layer of nickel phosphorus, respectively.
[0113] In particular, in order to obtain a phosphorus content within the nickel phosphorus coating of between 5 and 10% by weight (medium phosphorus) , in the case of using a single type of stabilizer, in the solution:
[0114] - the concentration of the ions of one or more heavy metals is fixed at between 0, 0005 and 0.005 mmol / 1,
[0115] the concentration of the compounds of the elements of group VI, Se, S, and Te is fixed at between 0.05 and 0.10 mmol / 1;
[0116] - the concentration of the oxyanions is fixed at between 2 and 50 mmol / 1,
[0117] In particular, in order to obtain a phosphorus content within the nickel phosphorus coating of between 10 and 15% by weight (high phosphorus) , in the case of using a single type of stabilizer, in the solution:
[0118] - the concentration of the ions of one or more heavy metals is fixed at between 0.005 and 0.05 mmol / 1,
[0119] the concentration of the compounds of the elements of group VI, Se, S, and Te is set at between 0.005 and 0.05 mmol / 1;
[0120] - the concentration of oxyanions is fixed at between 50 and 2000 mmol / 1,
[0121] Advantageously, it is possible to vary the phosphorus content of the coating - as an alternative or in combination with adjusting the concentration of the stabilizers - by changing the pH and deposition temperature . The pH and temperature values influence the reaction and therefore deposition rate of the coating. As the pH value and temperature increase, the reaction rate increases . Other things being equal, the phosphorus content co-deposited into the coating is correlated to the deposition rate . The higher the deposition rate, the lower the phosphorus content co-deposited into the coating.
[0122] A high-phosphorus nickel coating, by virtue of the amorphous microstructure, provides oxidation resistance, chemical resistance and weldabilityproperties .
[0123] According to a preferred embodiment, the nickel-plating process involves the deposition of nickel phosphorus in two different stages, so as to produce two superimposed layers having different phosphorus contents : a base layer and a top layer .
[0124] The base layer is preferably medium-phosphorus , while the top layer is high-phosphorus so as to provide weldability and chemical resistance properties .
[0125] More specifically, the base layer is medium-phosphorus because sulfur-based compounds naturally create a medium-phosphorus coating. It is, however, possible to obtain high phosphorus by adding high-phosphorus stabilizers (such as heavy metals) and / or by changing the pH and deposition temperature .
[0126] Said depositing step c) and / or, if provided, said depositing step d) is preferably followed by a water rinsing step .APPLICATION EXAMPLE 1
[0127] A copper or copper alloy component was subj ected to the step b) of cleaning the surface .
[0128] The cleaning process included the following sequential treatments :
[0129] - washing using an organic solvent in order to remove any oils, fats, organic contaminants, dust and / orparticles from the surface;
[0130] - washing using an aqueous solution containing surfactants and / or alkali components in order to remove any oils, fats, organic contaminants, dust and / or particles from the surface;
[0131] - first alkaline pickling to remove any organic or inorganic contaminants which are soluble in alkaline solutions from the surface .
[0132] acid pickling to remove any inorganic contaminants, oxides and the passivation layer from the surface of the component;
[0133] - second alkaline pickling.
[0134] Each of said treatments is followed by a surface rinse .
[0135] The component was then immersed in a bath containing a first solution comprising:
[0136] - nickel sulfate (Ni SO4 ) with a concentration of Ni2+ ions equal to 150 mmol / 1;
[0137] - hypophosphite ions (H2Po2-) with a concentration equal to 300 mmol / 1
[0138] - a mixture of boric acid, citric acid, succinic acid and acetic acid, with a concentration equal to 350 mmo 1 / 1 ;
[0139] - thiourea at a concentration of 0, 09 mmol / 1;
[0140] - cocamidopropyl betaine 0.400 mmol / 1.
[0141] ammonium (NH4+) with a concentration of NH4 + ions equal to 350 mmol / 1
[0142] The first solution also contained stabilizers of the oxyanion group (AsO2-, IO3-, Mo042 ) with a concentration equal to 2.5 mmol / 1.
[0143] The first solution was maintained at a temperature of between 85°C and 90°C with a pH of between 4 . 8 and 5.5.
[0144] The time of immersion in the bath lasted 20 minutes leading to the formation of a layer of nickel phosphorus with a phosphorus content equal to about 8% by weight, having an average thickness of 6.2 pm.
[0145] The concentration of Ni2+ ions was maintained around a value of 150 mmol / 1; the concentration of hypophosphite ions was maintained around a value of 300 mmol / 1; the pH was maintained within the range of 4.8 -5.5.
[0146] The nickel phosphorus layer thus obtained showed a complete covering of the copper alloy surface and showed high adhesion to the surface of the component . The adhesion was measured by means of an adhesion test involving bending metal sheet on a mandrel according to ISO 2819. Such test revealed the absence of delamination of the layer from the base material .APPLICATION EXAMPLE 2
[0147] The method used is as in the application example 1 ; after step c) , a further step d) of depositing nickel over the base layer obtained with step c) was performed.
[0148] The copper or copper alloy component provided with a coating, formed from the base layer, was immersed in a bath containing a second solution which differed from the first solution in that it did not contain thiourea and cocamidopropyl betaine .
[0149] As with the first solution, the second solution was also maintained at a temperature of between 85°C and 90°C with a pH of between 4.8 and 5.5.
[0150] The time of immersion in the bath lasted 20 minutes leading to the formation - above the base layer -of a top layer of nickel phosphorus with a phosphorus content equal to about 13% by weight, having an average thickness of 3.2 pm.
[0151] The concentration of heavy metal ions Bi3+ was maintained at around a value of 0.03 mmol / 1.
[0152] The concentration of Ni2+ ions was maintained at around a value of 150 mmol / 1; the concentration of hypophosphite ions was maintained at around a value of 400 mmol / 1; the pH was maintained within the range of 4.8 -5.5.
[0153] The two deposition steps c) and d) are followedby a water rinsing step .
[0154] The top layer of nickel phosphorus thus obtained exhibited properties of high weldability and chemical resistance .★ ★ ★
[0155] Other tests were performed in varying the concentrations of the various components of the solutions while remaining within the claimed ranges and obtaining comparable results .
[0156] In particular, the following organic sulfur compounds were tested: Mercaptobenzothiazole; 2-me thy Ibenzothi azo line ; Di ethyl di thio carbamate .
[0157] In particular, the following betaine-based surfactants were tested: lauryl betaine, lauramidopropyl betaine, N-oleyl betaine .
[0158] The results obtained are comparable to those in examples 1 and 2 .★ ★ ★
[0159] The invention allows numerous advantages to be obtained, which have already been described in part .
[0160] The electroless nickel plating process for copper or copper alloy components according to the invention is at the same time repeatable, ensures high productivity, does not use noble or (expensive) catalytic metals and allows for the implementation of a coating withhigh adhesion to the base material .
[0161] The electroless nickel plating process for copper or copper alloy components results in a surface with weldability and chemical resistance properties .
[0162] In particular, the electroless nickel plating process according to the invention, when it is intended to provide a high-phosphorus nickel coating, makes it possible to confer to the copper or copper alloy component :
[0163] Weldability (adhesion between coating and welded joint)
[0164] Oxidation resistance (maintaining the oxidation resistance of the surface, avoiding the formation of oxides that could compromise weldability, allowing welding to be performed even after a certain period from production)
[0165] - Chemical resistance (chemical resistance of the nickel coating that also confers corrosion resistance to the component)
[0166] The invention thus conceived therefore achieves its intended obj ectives .
[0167] Obviously, in practice it may also assume different forms and configurations from the one illustrated above, without thereby departing from the present scope of protection.
[0168] Furthermore, all details may be replaced withtechnically equivalent elements, and the dimensions, shapes, and materials used may be any according to the needs .
Claims
CLAIMS1. Electroless nickel plating process for copper or copper alloy components, comprising the following operating steps :a) providing a copper or copper alloy component;b) cleaning the surface of said component by performing at least one treatment for the removal of any oxides;c) depositing the nickel alloy upon the pre-treated surface of said component, wherein said step c) involves immersing said component as a whole, or at least in part, in a bath containing a first solution of nickel sulfate (Ni SO4 ) and hypophosphite ions (H2Po2-) .characterized in that said first solution comprises :- nickel sulfate (Ni SO4 ) with a concentration of Ni2 + ions of between 20 and 300 mmol / 1, preferably of between 30 and 130 mmol / 1;- hypophosphite ions (H2Po2-) with a concentration of between 100 and 1000 mmol / 1, preferably of between 300 and 700 mmo 1 / 1 ;- complexing agents and pH buffers with a concentration of between 50 and 1000 mmol / 1, preferably of between 200 and 600 mmol / 1, preferably a combination of weak acid ions;one or more organic sulfur compounds, with a concentration of between 0.005 and 0. 100 mmol / 1 ; and one or more betaine-based surfactants, with aconcentration of between 0.050 and 0.500 mmol / 1and in that said first solution is maintained at a temperature of between 70°C and 105°C with a pH of between 3 and 6,said step c) leading to the formation on said component of a base layer of nickel phosphorus directly upon the surface of said component exposed to said bath.
2. The process according to claim 1, wherein said one or more organic sulfur compounds are selected from the group consisting of : - thiourea; - Mercaptans; - Thiazolines; -Dithiocarbamates , preferably said first solution comprising thiourea as an organic sulfide compound with a concentration of between 0.005 and 0. 100 mmol / 1.
3. The process according to claims 1 or 2, wherein said one or more betaine-based surfactants are selected from the group consisting of : cocamidopropyl betaine; lauryl betaine; lauramidopropyl betaine; N-oleyl betaine, preferably said first solution comprising cocamidopropyl betaine as a betaine-based surfactant with a concentration of between 0.050 and 0.100 mmol / 1.
4. The process according to claim 1, 2 or 3, wherein said first solution further comprises ammonium (NH4+) with a concentration of NH4+ ions of between 20 and 600 mmol / 1, preferably of between 20 and 400 mmol / 1.
5. The process according to any one of the precedingclaims, wherein said first solution further comprises one or more stabilizing agents selected from the group consisting of :- compounds of the elements of the Group VI, Se, S, and Te - oxyanions, preferably selected from the group consisting of AsO2-, IO3-, Mo042- - heavy metal ions, preferably selected from the group consisting of Sn2+, Pb2+, Cu2+, Bi3+, Sb3+, T1+ .
6. The process according to any one of the preceding claims, comprising a step d) of depositing nickel alloy upon the base layer of nickel phosphorus to obtain a top layer of nickel phosphorus .
7. The process according to claim 6, wherein said step d) involves immersing said component as a whole, or at least in part, in a bath containing a second solution of nickel sulfate (Ni SO4 ) and hypophosphite ions (H2Po2-) , wherein said second solution comprises :- nickel sulfate (Ni SO4 ) with a concentration of Ni2 + ions of between 20 and 300 mmol / 1, preferably of between 30 and 130 mmol / 1;- hypophosphite ions (H2Po2-) with a concentration of between 100 and 1000 mmol / 1, preferably of between 300 and 700 mmo 1 / 1 ;- complexing agents and pH buffers with a concentration of between 50 and 1000 mmol / 1, preferably of between 200 and600 mmol / 1, preferably a combination of weak acid ions; wherein said second solution is maintained at a temperature of between 70°C and 105°C with a pH of between 3 and 6.
8. The process according to claim 7, wherein said second solution further comprises ammonium (NH4+) with a concentration of between 20 and 600 mmol / 1, preferably of between 20 and 400 mmol / 1.
9. The process according to claim 8, wherein said second solution further comprises one or more stabilizing agents selected from the group consisting of :- compounds of the elements of the Group VI, Se, S, and Te - oxyanions, preferably selected from the group consisting of AsO2-, IO3-, Mo042- - heavy metal ions, preferably selected from the group consisting of Sn2+, Pb2+, Cu2+, Bi3+, Sb3+, T1+ .
10. The process according to any one of the preceding claims, when dependent upon claim 5 or 9, comprising a step of adjusting the concentration of said one or stabilizing agents in the first or second solution as a function of the phosphorus content to be obtained within the base layer of nickel phosphorus and within the top layer of nickel phosphorus, respectively.
11. The process according to any one of the preceding claims, wherein said weak acids are selected from the group consisting of : formic acid, propionic acid, boric acid,citric acid, succinic acid, acetic acid and malic acid.
12. The process according to any one of the preceding claims, wherein said cleaning step b) comprises acid pickling in order to remove any inorganic contaminants, oxides and the passivation layer, followed by rinsing.
13. The process according to claim 14, wherein said cleaning step b) comprises one or more of the following treatments to be performed before the acid picking:- washing using an organic solvent in order to remove any oils, fats, organic contaminants, dust and / or particles from the surface;- washing using an aqueous solution containing surfactants and / or alkali components in order to remove any oils, fats, organic contaminants, dust and / or particles from the surface ;- alkaline pickling to remove any organic or inorganic contaminants which are soluble in alkaline solutions from the surface;and wherein said steps are followed by a surface rinse .
14. The process according to any one of the preceding claims, wherein said cleaning step b) comprises alkaline pickling followed by rinsing to be performed after the acid pickling and the subsequent rinsing.
15. The process according to any one of the preceding claims, wherein said depositing step c) and / or said stepd) is followed by a water rinsing step .