Dispersed electrolyte for graphite-containing layer

Abstract

The present invention relates to a dispersion electrolyte for the electrodeposition of tin, nickel or tin-nickel layers containing graphite, to a method for the electrodeposition of a graphite-containing layer of the above-mentioned type, to a metal substrate coated with a graphite-containing layer of the above-mentioned type, and to the use of said dispersion electrolyte. 2+ ions and / or Ni 2+ ions, graphite particles, at least one anionic dispersant, and Sn 2+ ions and Ni 2+ It contains a complexing agent for ions, a conductive salt, and water, and has a pH of 4 to 7.

Description

[Technical Field]

[0001] The present invention relates to a dispersion electrolyte for electrodepositing a tin, nickel, or tin-nickel layer containing graphite, a method for electrodepositing the graphite-containing layer using the above-mentioned electrolyte, a metal substrate coated with the above-mentioned graphite-containing layer, and the use of the dispersion electrolyte. [Background technology]

[0002] As an alternative to hard chromium layers, tin-nickel layers with equivalent physical properties, and particularly higher hardness levels, are described, for example, in WO2016 / 131916A1. For electrodeposition of such tin-nickel layers, electrolytes have been used that are far more advantageous than those used for hard chromium layers, for environmental and health reasons, than electrolytes that use chromium(VI) compounds and, generally, hexafluorosilicic acid, which can release hydrogen fluoride, which is usually toxic at low pH values.

[0003] Similar to hard chromium layers, the tin-nickel layers described in WO2016 / 131916A1 have high hardness levels, for example, HV750 (HV = Vickers hardness) or higher. Furthermore, hard tin-nickel layers are characterized by very good corrosion resistance to acids and bases and can be machined using grinding, turning, milling and similar processes. Because the tin-nickel layers have a certain degree of brittleness, it is also possible to peel off worn layers from components.

[0004] Due to these properties, hard tin-nickel layers, like hard chromium layers, are generally used as the "final layer," or outer layer, of the component, primarily to protect the aforementioned components.

[0005] In principle, there is also a demand for supplying electronic components such as contacts or electrodes with corrosion-resistant protective layers. In all cases, and especially in the context of expanding electrification, the sustainability of such components is more important than ever, as they need to be reliable, long-lasting, and as efficient as possible—that is, with as little loss as possible. In addition, substances and processes that harm health and the environment during their manufacture should be eliminated as much as possible.

[0006] Therefore, there is a need for corrosion-resistant protective layers for electrical contacts, and even for electrodes in batteries or fuel cells, that possess not only good corrosion resistance but also low electrical contact resistance (boundary resistance) and improved tribological properties, particularly wear resistance, compared to conventional hard tin-nickel layers. Consequently, there is a demand for electrolytes capable of electrolytically producing layers with this advantageous combination of properties.

[0007] Furthermore, it is desirable to improve these properties with tin and nickel layers, which can also be used as protective layers against corrosion. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] WO2016 / 131916A1 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] Therefore, one object of the present invention is to provide an electrolyte for electrodepositing a tin layer, nickel layer, or tin-nickel layer having improved tribo-characteristics and low contact resistance, which can be used safely and in an environmentally responsible manner. Another object of the present invention is to provide a method for electrodepositing the above-mentioned tin layer, nickel layer, or tin-nickel layer, a metal substrate coated with the above-mentioned tin layer, nickel layer, or tin-nickel layer, and the use of the electrolyte.

Means for Solving the Problem

[0010] These objects are achieved by a dispersion electrolyte for electrodepositing a graphite-containing tin layer, a graphite-containing nickel layer, or a graphite-containing tin-nickel layer, an electrodeposition method of the graphite-containing layer using the electrolyte, a metal substrate coated with the graphite-containing layer, and the use of the dispersion electrolyte. Preferred configurations are given in the dependent claims and below.

Brief Description of the Drawings

[0011] [Figure 1] Photographs showing the coated substrates of Comparative Example 1 (Fig. 1a) and Comparative Example 2 (Fig. 1b) and Example 2 (Fig. 1c). [Figure 2] Scanning electron micrograph of Comparative Example 1. [Figure 3] Scanning electron micrograph of Example 2.

Embodiments for Carrying Out the Invention

[0012] The present invention provides a dispersion electrolyte for electrodepositing a graphite-containing tin layer, a graphite-containing nickel layer, or a graphite-containing tin-nickel layer. The dispersion electrolyte - Sn ions (tin ions) at a concentration of 2 to 50 g / L and / or Ni 2+ ions (nickel ions) at a concentration of 0.2 to 70 g / L, and 2+ - graphite particles at a concentration of 5 to 200 g / L, and - at least one anionic dispersant at a concentration of 1 to 25 g / L, and - a complexing agent for Sn and Ni 2+ ions, and 2+ - a conductive salt, and - water and contains.

[0013] The pH of the dispersion electrolyte according to the present invention is 4 to 7. The dispersion electrolyte is also abbreviated as "electrolyte" hereinafter.

[0014] The inventors have surprisingly found that the dispersed electrolyte according to the present invention can form a graphite-containing layer by electrodepositing graphite particles together with a metal layer. Furthermore, they have also surprisingly found that incorporating graphite particles into a tin, nickel, or tin-nickel layer improves contact resistance (boundary resistance) and tribological properties, particularly wear resistance, compared to the corresponding layer without graphite particles. The improved tribological properties also result in improved durability of the coating due to reduced brittleness. Therefore, the dispersed electrolyte allows for the formation of a protective layer that extends the operating time, i.e., the practical life, making the entire component more sustainable by reducing electrical energy loss due to the low contact resistance. Moreover, the graphite-containing layer has very good corrosion resistance to acids and bases. Therefore, the electrolyte allows for the production of a reliable protective layer with minimal loss due to corrosion.

[0015] Therefore, it is possible to achieve this advantageous combination of properties in a single layer using a dispersed electrolyte. Until now, it was at best possible to obtain this combination of properties using multiple layers manufactured separately.

[0016] Therefore, using the dispersed electrolyte according to the present invention, it is possible to achieve electrodeposition (i.e., electrolytic deposition) of a graphite-containing tin layer, a graphite-containing nickel layer, or a graphite-containing tin-nickel layer having advantageous properties onto a metal substrate. In this context, "graphite-containing" means that spectroscopically detectable graphite is present in the form of graphite particles. Therefore, the graphite-containing layer refers to a graphite particle-containing layer and is a composite layer.

[0017] Regarding the "tin layer," substantially only tin atoms (for example, at least 95% by mass, specifically at least 98% by mass) are deposited as metal. In this case, the underlying electrolyte is Sn 2+ It contains ions, Ni 2+It contains substantially zero ions or no ions. Similarly, the "nickel layer" represents a layer in which only nickel atoms (for example, at least 95% by mass, specifically at least 98% by mass) are deposited as a metal. In this case, the underlying electrolyte is Ni 2+ ion-containing, but Sn 2+ contains substantially zero ions or no ions. Regarding the "tin-nickel layer", substantially only tin and nickel atoms (for example, at least 95% by mass, specifically at least 98% by mass) are deposited as a metal. Therefore, the electrolyte must contain Sn 2+ and Ni 2+ ions.

[0018] The above dispersion electrolyte can be handled very flexibly, enabling the selection of electrodeposition conditions from a wide range. Since the pH of the dispersion electrolyte is from 4 to 7, that is, slightly acidic, it can be safely used without generating dangerous hydrofluoric acid (hydrogen fluoride, HF). At a low pH value, that is, less than 3.5, if the electrolyte contains fluoride ions, the amount of hydrogen fluoride generated may increase.

[0019] The above dispersion electrolyte contains Sn 2+ and / or Ni 2+ ions, that is, dissolved tin and / or nickel salts. In principle, all suitable tin and / or nickel salts can be used. Chloride salts, that is, SnCl2·nH2O and NiCl2·nH2O, are preferably used because they are inexpensive, easy to handle, and chloride ions (Cl - ) increase the conductivity of the electrolyte. Anhydrous salts, or salts containing crystal water indicated by additionally specified "nH2O" (where n is usually from 0 to 6), can be used. SnCl2·2H2O and / or NiCl2·6H2O are preferably used in the electrolyte because these salts are storable and inexpensive.

[0020] Regardless of whether the dispersed electrolyte is used for precipitation of a graphite-containing tin layer or a graphite-containing tin-nickel layer, the electrolyte specifically contains Sn at a concentration of 5 to 45 g / L, preferably 20 to 30 g / L, and more preferably 23 to 27 g / L. 2+ Contains ions. Regarding the graphite-containing nickel layer and the graphite-containing tin-nickel layer, Ni 2+ The ion concentration is specifically 10 to 65 g / L, preferably 50 to 65 g / L, and more preferably 50 to 60 g / L.

[0021] According to a preferred embodiment, the graphite-containing tin-nickel layer is precipitated at a molar ratio of tin to nickel of 1:1 such that the nickel content relative to metallic tin and metallic nickel is approximately 35% by mass. As described below, the nickel content can be modified by process conditions so that the graphite-containing tin-nickel layer may contain 30 to 40% by mass, preferably 30 to 38% by mass, more preferably 32 to 37% by mass, and even more preferably 35% by mass, nickel relative to metallic tin and metallic nickel. With respect to the above graphite-containing tin-nickel layer, the electrolyte is preferably Sn at a concentration of 20 to 30 g / L, more preferably 23 to 27 g / L. 2+ Ni ions, preferably at a concentration of 50 to 65 g / L, more preferably at a concentration of 50 to 60 g / L. 2+ It contains ions. The nickel content in the electrolyte is usually higher than the tin content because nickel is less noble than tin and therefore does not precipitate as easily. In this embodiment, Sn 2+ Ion: Ni 2+ The mass ratio of the ions is preferably 1:1 to 1:4, more preferably 1:2 to 1:3.

[0022] Surprisingly, it was found that the nickel content in the graphite-containing tin-nickel layer could also be significantly reduced compared to the conventional 1:1 ratio described above. According to this embodiment, the nickel content is 10 to 20% by mass, preferably 13 to 18% by mass, and more preferably 14 to 17% by mass, relative to metallic tin and metallic nickel. To achieve a significantly lower nickel content, the mass ratio of tin to nickel in the electrolyte should be 8:1 or higher, specifically 10:1 or higher.

[0023] The dispersed electrolyte according to the present invention contains graphite particles dispersed in an amount of 5 to 200 g / L, which brings about the above-mentioned effects. The content of graphite particles in the above electrolyte is preferably 20 to 150 g / L, more preferably 40 to 100 g / L.

[0024] Generally, the Sn of the dispersed electrolyte 2+ Ions and / or Ni 2+ Even when the ion content is low, materials with a low graphite particle content are used. Similarly, Sn 2+ Ions and / or Ni 2+ When the ion content is high, a large amount of graphite particles is preferably used. In the above dispersed electrolyte, the mass ratio of Ni:graphite is preferably 1:0.5 to 1:2, more preferably 1:0.5 to 1:1, and / or the mass ratio of Sn:graphite is preferably 1:0.5 to 1:5, more preferably 1:1.5 to 1:2.5. The graphite content of the graphite-containing layer can also be changed by the concentration of graphite in the electrolyte.

[0025] Since the type of graphite used is not limited in principle, natural or synthetic graphite can be used. The median (d50) particle size of the graphite particles is usually in the range of 20 nm to 20 μm, preferably 1 to 10 μm, and more preferably 1.5 to 8 μm. The above particle size can be measured, for example, using a HELOS (Helium-Neon Laser Optical System) spectrometer with laser diffraction in accordance with ISO 13320:2020. Generally, the above particle size should be less than or equal to the desired thickness of the graphite-containing layer. The above particle size can be adjusted by a screening process using conventional milling and / or a method that can separate excessively large or small particles. Suitable graphite particles are also commercially available.

[0026] Smaller graphite particles, specifically those with a median particle size of 20 nm to 0.5 μm, tend to moderately improve tribological properties and even lower contact resistance in relatively hard layers. Graphite particles with a median particle size of 1.5 to 8 μm tend to exhibit very good tribological properties and significantly reduce contact resistance, despite having a somewhat lower hardness level than equivalent nickel or tin-nickel layers without graphite particles.

[0027] To efficiently disperse graphite particles in the electrolyte and uniformly incorporate them into the graphite-containing layer, the dispersed electrolyte according to the present invention contains an anionic dispersant. The above anionic dispersant typically has a sulfate group (-OSO3-), a sulfonic acid group (-SO3-), a carboxylate group (-CO2-), or a carboxyl group (-CO2H) that can subsequently exist as anions in aqueous solution. Alkali metal ions, preferably Na + , and ammonium anion (NH4 + These are usually used as counterions because they provide good water solubility, increase conductivity, and do not adversely affect electrodeposition. The sulfate and sulfonic acid groups are in a dissociated form at the pH of the dispersion electrolyte; that is, they are not in a protonated form. In contrast, the carboxyl and carboxylate groups can be in equilibrium with each other.

[0028] The above-mentioned anionic dispersant is preferably at least one selected from the group consisting of a sulfate compound having an alkyl group, aralkyl group, or aromatic group having 6 to 24 carbon atoms; a sulfonate compound having an alkyl group, aralkyl group, or aromatic group having 6 to 24 carbon atoms; and a polymer containing a carboxylate group or a carboxyl group. Different combinations of anionic dispersants can be used. "Sulfate compound" in this specification refers to an organic sulfate group-containing compound. Similarly, "sulfonate compound" is understood to mean an organic sulfonic acid group-containing compound.

[0029] The above-mentioned anionic dispersant is preferably at least one selected from the group consisting of a sulfate compound having an alkyl group having 6 to 24 carbon atoms; an aromatic sulfonate compound whose underlying aromatic group each has 6 to 14 carbon atoms; and a polymer containing poly(meth)acrylic acid and salts thereof.

[0030] More preferably, the dispersant is a sulfate compound having an alkyl group having 6 to 24 carbon atoms, selected from the group consisting of aliphatic alcohol sulfate, aliphatic alcohol polyether sulfate, aliphatic alcohol aryl polyether sulfate, and combinations thereof, and / or a polymer having an aromatic sulfonic acid group, wherein the underlying aromatic group each has 6 to 14 carbon atoms, and the aromatic sulfonic acid group is preferably derived from phenylsulfonic acid, phenolsulfonic acid, or naphthylsulfonic acid. In this case, the alkyl group having 6 to 24 carbon atoms originates from an aliphatic alcohol. The polyether group is specifically a polyethylene glycol group. The polymer having an aromatic sulfonic acid group is, for example, a condensate of an aromatic sulfonate compound, such as phenylsulfonic acid, phenolsulfonic acid, or naphthylsulfonic acid, with formaldehyde. Aliphatic alcohol sulfates and aliphatic alcohol polyglycol ether sulfates containing alkyl groups having 6 to 20 carbon atoms, specifically 8 to 18 carbon atoms, are more preferably present as sulfate compounds.

[0031] Furthermore, a combination of at least one preferred sulfate compound and at least one preferred sulfonate compound is particularly preferred as an anionic dispersant. These are preferably used in a mass ratio of 1:10 to 10:1, specifically 1:8 to 3:1.

[0032] Examples of anionic dispersants include Sokalan® (BASF SE, poly(meth)acrylate-containing polymers or salts thereof), e.g., Sokalan® SR, sodium-phenolsulfonic acid condensate, sodium-phenylsulfonic acid condensate, sodium-naphthalenesulfonic acid condensate, Disponil® APE (BASF SE, alkyl polyglycol ether sulfate), and aliphatic alcohol sulfates having 6 to 20 carbon atoms, e.g., 2-ethylhexyl sulfate (e.g., sodium methsulfate), lauryl sulfate, oleyl sulfate, stearyl sulfate, and sulfates of mixed aliphatic alcohols, specifically their corresponding sodium salts.

[0033] The above-mentioned anionic dispersant is used in the dispersed electrolyte at a concentration of 1 to 25 g / L. Preferably, it is present in the electrolyte at a concentration of 2 to 20 g / L, more preferably 4 to 10 g / L. Typically, a small amount of the anionic dispersant is used for low concentrations of graphite particles, and similarly, a large amount is used for high concentrations of graphite particles.

[0034] As described above, the anionic dispersant effectively disperses graphite particles in the electrolyte and enables the uniform introduction of graphite particles into the graphite-containing layer. Advantageously, it is not always necessary to disperse the graphite particles beforehand; rather, they can usually be introduced into the electrolyte in powder form. Advantageously, since it is not necessary to homogenize the electrolyte in an ultrasonic bath to achieve this goal, the labor required for preparation is reduced, and it becomes possible to use the dispersed electrolyte economically and in large volumes. Furthermore, it is also possible to disperse phosphate and pyrophosphate together in the dispersed electrolyte according to the present invention, thereby improving the solubility of tin and / or nickel salts.

[0035] Further components of the dispersed electrolyte include Ni in the solution, so that the graphite-containing layer is formed uniformly and at a good deposition rate. 2+ and / or Sn 2+The complexing agent has the effect of stably maintaining salts and moving them. In principle, any known complexing agent used in tin and nickel electrolytes can be used as the complexing agent. Preferably, the complexing agent is a chelating, water-soluble organic compound having at least three functional groups selected from amino groups, carboxyl groups, and carboxylate groups. Preferably, at least two of the functional groups are amino groups. The amino groups are selected from primary, secondary, and tertiary amino groups. More preferably, the complexing agent contains one or more secondary and / or tertiary amino groups. The functional groups used for coordination are usually spaced apart by two or three carbon atoms so that they can form a stable chelate complex.

[0036] Particularly preferred is that the complexing agent is at least one selected from the group consisting of EDTA, DETA, DOTA, and DOTATOC. EDTA means ethylenediaminetetraacetic acid. DETA represents diethylenetriamine. DOTA means 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid. DOTATOC represents a DOTA-derived complexing agent (specifically Phe-Cys-Tyr-Lys-Thr-Cys-Thr) in which the DOTA molecule is bound to the N-terminus of the octapeptide via an amine bond.

[0037] The amount of complexing agent used, in particular, is Sn in the dispersed electrolyte. 2+ and / or Ni 2+ This is based on the ion concentration. Typically, the above complexing agent is present in the electrolyte at a concentration of 5 to 70 g / L, preferably 10 to 65 g / L, and more preferably 40 to 60 g / L.

[0038] The above-mentioned dispersed electrolyte further contains a conductive salt. A conductive salt is understood to mean a water-soluble salt that increases the conductivity of the electrolyte. Preferably, the conductive salt is at least one selected from the group consisting of sodium chloride, potassium chloride, ammonium chloride, sodium acetate, potassium acetate, ammonium acetate, ammonium fluoride, ammonium difluoride, sodium fluoride, and potassium fluoride. The above-mentioned electrolyte preferably contains at least one conductive salt selected from ammonium fluoride, ammonium difluoride, and ammonium acetate. Advantageously, the conductive salt also increases the solubility of tin and / or nickel salts.

[0039] Preferably, the dispersion electrolyte for electrodepositing the graphite-containing tin-nickel layer contains at least one fluoride (F) when the nickel content is 32 to 37% by mass, for example 35% by mass. - It contains conductive salts. It may be combined with other conductive salts, but is not required. It is hypothesized that the fluoride ions stabilize the tin-nickel dinuclear complex, thereby supporting the formation of a very constant alloy ratio of the tin-nickel layer with a 1:1 molar ratio.

[0040] The conductive salts mentioned above are typically present in the electrolyte at a concentration of 5 to 70 g / L, preferably 10 to 65 g / L, and more preferably 40 to 60 g / L.

[0041] According to a preferred embodiment, the dispersed electrolyte is - Sn concentrations of 5 to 45 g / L, especially 20 to 30 g / L 2+ Ions, and / or Ni at concentrations of 10 to 65 g / L, particularly 50 to 65 g / L. 2+ Ions and, - Graphite particles with an average particle size of 1 to 10 μm, particularly 1.5 to 8 μm, at concentrations of 20 to 150 g / L, especially 40 to 100 g / L, - At least one anionic dispersant in a concentration of 2 to 20 g / L, particularly 4 to 10 g / L, - A complexing agent selected from EDTA, DETA, DOTA, and DOTATOC in a concentration of 10 to 65 g / L, - Conductive salts with concentrations of 10 to 65 g / L, - Water and Includes.

[0042] In this case, the anionic dispersant is at least one selected from the group consisting of a sulfate compound having an alkyl group having 6 to 24 carbon atoms; an aromatic sulfonate compound, wherein the underlying aromatic group is an aromatic sulfonate compound having 6 to 14 carbon atoms; and a polymer containing poly(meth)acrylic acid and salts thereof, preferably a combination of at least one sulfate compound and at least one sulfonate compound in the ratio described above.

[0043] According to a particularly preferred embodiment, the dispersed electrolyte is - Sn concentrations of 20 to 30 g / L, especially 23 to 27 g / L 2+ Ions and / or Ni at concentrations of 50 to 65 g / L 2+ Ions and, - Graphite particles with an average particle size of 1.5 to 8 μm at concentrations of 40 to 100 g / L, - At least one anionic dispersant in a concentration of 4 to 10 g / L, - A complexing agent selected from EDTA, DETA, and DOTA at concentrations of 10 to 65 g / L, particularly 40 to 60 g / L, - A complexing agent containing or comprising a fluoride-containing conductive salt at a concentration of 10 to 65 g / L, particularly 40 to 60 g / L, - Water and Includes.

[0044] In this case, the anionic dispersant is preferably at least one selected from the group consisting of aliphatic alcohol sulfates and aliphatic alcohol polyether sulfates, wherein the alkyl group of the aliphatic alcohol portion has 6 to 24 carbon atoms, specifically 6 to 20 carbon atoms, preferably 8 to 18 carbon atoms, and polymers having aromatic sulfonic acid groups, wherein the underlying aromatic group each has 6 to 14 carbon atoms, and the aromatic sulfonic acid group is preferably derived from phenylsulfonic acid, phenolsulfonic acid, or naphthylsulfonic acid. Particularly preferred, in this case, the at least one anionic dispersant is a combination of an aliphatic alcohol sulfate or aliphatic alcohol polyglycol ether sulfate containing an alkyl group with 6 to 20 carbon atoms, specifically 8 to 18 carbon atoms, and a phenyl sulfonic acid polymer (phenyl sulfonic acid condensate), a phenol sulfonic acid polymer (phenol sulfonic acid condensate), or a naphthyl sulfonic acid polymer (naphthyl sulfonic acid condensate), for example, in the ratio described above.

[0045] Furthermore, the above-mentioned dispersed electrolyte may contain conventional additives, such as those known from conventional electrolytes for the electrodeposition of tin, nickel, and tin-nickel layers. In addition to the above-mentioned anionic dispersant, other dispersants may also be added to the electrolyte. However, preferably only the anionic dispersant is used.

[0046] The above-described dispersed electrolyte can be formed by mixing or dissolving tin and / or nickel salts and other components, i.e., conductive salts, complexing agents, anionic dispersants, graphite powder, and water. The graphite powder can be added as a solid without prior dispersion or ultrasonic treatment of the mixture for dispersion. When forming the electrolyte, stirring is preferably carried out, and if required, gentle heating is carried out to accelerate the dissolution of the components. The pH can be adjusted, for example, by adding hydrochloric acid or sodium hydroxide, ammonia, potassium hydroxide, or aqueous solutions thereof. The dispersed electrolyte according to the present invention is advantageous because it can be manufactured in large quantities, making it suitable for industrial applications. The above-described electrolyte can be stored, and any graphite particles that may have settled can be redispersed by stirring.

[0047] Furthermore, the present invention provides a method for electrodepositing a graphite-containing tin layer, a graphite-containing nickel layer, or a graphite-containing tin-nickel layer. The method comprises electrodepositing a graphite-containing layer onto a metal substrate using a dispersed electrolyte according to at least one embodiment described herein. The method is carried out at a temperature in the range of 50 to 85°C, preferably 55 to 70°C. The dispersed electrolyte is heated to this temperature.

[0048] The above method can be carried out using all conventional equipment for electrodeposition of the tin-nickel layer. If the electrolyte contains a fluoride salt, a plastic container is preferable to a glass container. Typically, the electrolyte is completely mixed during deposition, for example, by stirring.

[0049] The above-mentioned metal substrate is connected as a cathode. This may be, for example, a metal component, a connecting component, a switch, or an electrode. Preferably, the graphite-containing layer is formed on the metal substrate as a final layer, i.e., an outer layer. "Metal substrate" is also understood to mean a metal layer that can be coated by electrolysis, i.e., a pre-metallated plastic. Examples of metals include precious metals such as copper, nickel, palladium, or platinum, steel, stainless steel, brass, and bronze. The surface to be coated may be cleaned in advance using conventional methods, for example, degreased.

[0050] A nickel anode may be used as the anode, for example. This allows for easy control of the nickel ion content in the electrolyte. Multiple anodes can also be used.

[0051] Furthermore, the above method greatly improves the degree of freedom in implementing the method. Preferably, the precipitation is 0.1 to 10 A / dm 2 Preferably 0.5 to 5 A / dm 2 This is carried out at the following current density. The above current density can be used to affect, for example, the graphite content, and in the case of a graphite-containing tin-nickel layer, the nickel content. In principle, the higher the current density, the higher the graphite content in the graphite-containing layer. 5A / dm 2 The above current densities make it possible to increase the nickel content in the graphite-containing tin-nickel layer.

[0052] Furthermore, it was found that the higher the tin concentration in the electrolyte, the lower the nickel content in the graphite-containing tin-nickel layer tends to be. Similarly, the lower the nickel concentration in the electrolyte, the somewhat lower the nickel content in the graphite-containing tin-nickel layer may be. For example, a tin / nickel ratio of 8:1 or higher, specifically 10:1 or higher, makes it possible to set the nickel content in the graphite-containing tin-nickel layer to 10 to 20% by mass.

[0053] In some cases, the pH of the electrolyte can also affect the nickel content of the graphite-containing tin-nickel layer. Higher pH tends to result in a somewhat higher nickel content.

[0054] In principle, the above method can be used to produce graphite-containing layers of any desired thickness. Typically, the graphite-containing layers precipitate with a thickness of 4 to 30 μm, preferably 5 to 20 μm, and more preferably 5 to 12 μm. The layer thickness is measured, for example, by X-ray fluorescence spectroscopy according to DIN EN ISO 3497 (2001-12) using a Fischerscope XDAL X-ray fluorescence spectrometer.

[0055] Furthermore, the present invention provides a coated metal substrate that can be obtained by the method described herein using the dispersed electrolyte described herein. Accordingly, the metal substrate is coated with a graphite-containing tin layer, a graphite-containing nickel layer, or a graphite-containing tin-nickel layer. The graphite-containing layer contains 0.1 to 8% by mass of graphite relative to the total mass of the graphite-containing layer.

[0056] Preferably, the graphite-containing layer contains 0.5 to 3% by mass, more preferably 0.8 to 2.3% by mass, of the total mass of the graphite-containing layer.

[0057] As described above, compared to the corresponding layer that does not contain graphite particles, the graphite-containing layer has lower contact resistance and improved tribological properties.

[0058] According to one embodiment, the graphite-containing layer is a graphite-containing tin layer. The tin layer is inherently very flexible and ductile. Surprisingly, it has been found that even such a layer can exhibit a significant increase in tribological properties, particularly abrasion resistance. Similarly, it has been found that contact resistance can be significantly reduced. The graphite-containing tin layer is particularly suitable for plug-in and sliding contact applications.

[0059] In another embodiment, the graphite-containing layer is a graphite-containing nickel layer. Again, it was found that incorporating graphite particles into the nickel layer significantly improved tribological properties and contact resistance compared to the corresponding nickel layer without added graphite. As a result, the brittleness of the nickel layer was also reduced, providing extended durability. Simultaneously, it was possible to achieve good hardness in the graphite-containing nickel layer even without a subsequent hardening process.

[0060] According to a preferred embodiment, the average coefficient of friction of the graphite-containing nickel layer is 0.4 or less, preferably 0.3 or less, more preferably 0.2 or less, and / or the hardness is at least HV300 (Vickers hardness), preferably at least HV350, more preferably at least HV400. The average coefficient of friction and hardness are measured using the method described below. In particular, these properties can be adjusted through the graphite content in the layer and, furthermore, through the size of the graphite particles.

[0061] The graphite-containing nickel layer described above is particularly suitable as a protective layer and for electrode coatings, plug-in connections, and contact surfaces. The graphite-containing nickel layer can be a less expensive alternative to tin-nickel layers when corrosion resistance requirements are not particularly high. The high-density, well-adhering oxide layer forms on the freshly deposited nickel layer and provides good protection against corrosion by dilution acids and bases. While conventional nickel layers have high contact resistance due to the oxide layer, this property is improved in the nickel layer according to the present invention through the introduction of graphite.

[0062] According to another embodiment, the graphite-containing layer is a graphite-containing tin-nickel layer. The graphite-containing tin-nickel layer typically has a nickel content of 10 to 40% by mass. In this case, it is preferable that the nickel content is in the range of 13 to 18% by mass or 30 to 38% by mass relative to metallic tin and metallic nickel.

[0063] Surprisingly, it was found that electroanalysis could produce graphite-containing tin-nickel layers with a nickel ratio much lower than the conventional molar ratio of 1:1 (approximately 35% by mass). When the nickel content relative to metallic tin and metallic nickel is 13 to 18% by mass, specifically 14 to 17% by mass, the graphite-containing tin-nickel layer exhibits very good tribological properties and low contact resistance. Increasing the amount of tin introduced into the layer again significantly reduces the contact resistance. The graphite-containing tin-nickel layer according to this embodiment is particularly suitable as a substitute for plug-in connections, switching contacts, and silver layers.

[0064] In another configuration, the nickel content of the graphite-containing tin-nickel layer is preferably 30 to 38 mass%, more preferably 32 to 37 mass%, for example 35 mass%, relative to metallic tin and metallic nickel. Compared to the corresponding tin-nickel layer without graphite, the tribological properties were improved and the contact resistance was reduced. Surprisingly, these properties were found to be combined with good hardness. Thus, the hardness of the graphite-containing tin-nickel layer is preferably HV200 or higher, more preferably HV300 or higher.

[0065] The graphite-containing tin-nickel layer preferably has an average friction coefficient of 0.4 or less, more preferably 0.2 or less.

[0066] The contact resistance of the gold contact area and the associated graphite-containing tin-nickel layer at 25°C is specifically 50 mΩ (mOhm) or less, preferably 40 mΩ or less, and more preferably 30 mΩ or less. The above contact resistance is measured according to the method described below.

[0067] The hardness, average coefficient of friction, and contact resistance of the tin-nickel layer can be adjusted, in particular, through the graphite content in the layer and even the diameter of the graphite particles.

[0068] As described above, the graphite-containing layer formed by the electrolyte according to the present invention is suitable for various applications, particularly for electronic components having low contact resistance, tribological properties, and good durability due to resistance to corrosion from acids and bases. The present invention also provides the use of the dispersed electrolyte described herein for producing electronic components having a graphite-containing tin layer, a graphite-containing nickel layer, or a graphite-containing tin-nickel layer. Preferably, the dispersed electrolyte is used to produce a graphite-containing tin-nickel layer as a protective layer or final layer on a contact or electrode. The electrode can be used, for example, in a battery, electrolytic device, or fuel cell. Further application areas include electrical connector technology and catalyst layers. [Examples]

[0069] The present invention is described below with reference to examples. It is not limited to these examples.

[0070] Measurement method The following measurement method was used.

[0071] 1) Thickness of the layer The layer thickness was measured using a Fischerscope XDAL X-ray fluorescence spectrometer in accordance with DIN EN ISO 3497 (2001-12). This method is used when the layer thickness is up to 20 μm. If the layer thickness is greater than 20 μm, the layer thickness is measured by microscope on the cross-section of the layer. The average measurement is mentioned.

[0072] 2) Composition Furthermore, the alloy composition (i.e., tin and nickel) was also analyzed by X-ray fluorescence spectroscopy using the aforementioned apparatus in accordance with DIN EN ISO 3497 (2001-12). Measurements were obtained with an accuracy of ±2 mass% or higher. The corresponding content is given for the metal in the precipitated layer.

[0073] The graphite content of the entire cross-section of the graphite-containing layer was measured using glow discharge emission spectroscopy (GDOES) in accordance with DIN ISO 11505 (2018-02). The above content refers to the entire graphite-containing layer.

[0074] 3) Tribology Tribology and average friction coefficient studies were conducted by "Forschungsinstitut Edelmetalle + Metallchemie (fem)", Schwabisch Gmund (Germany) according to test specification SOP 4CP1 as pin-on-disk tribology. A CSEM pin-on-disk tribometer was used as the test apparatus. The counterbody was a 6 mm diameter sphere of alloy 100 Cr6, material number 1.3505. The following parameters were used: Normal load: 5N Speed: 500 minutes -1 Sliding speed: 52.4mm / s Temperature: 23℃±2℃ Relative humidity: 50%±6% Rotation speed: 10,000

[0075] The average coefficient of friction was measured in a long-term test of 10,000 cycles (rotations). The above average coefficient of friction (μ) is dimensionless.

[0076] 4) Contact resistance With a maximum contact pressure of 2N, according to specification MIL-DTL-81706B ("Forschungsinstituts Edelmetalle + Metallchemie (fem)", ContRes-ConCoat-001 of Schwabisch Gmund (Germany)), The contact resistance associated with the gold contact area was measured at 25°C using a four-point measurement system. A Keithley Instruments INC. Model 2410, 4393118, C34 was used as the measuring device.

[0077] 5) Vickers hardness The surface hardness of each precipitated layer was tested after optional polishing (i.e., conditioning) of the surface. Vickers hardness is referred to using the unit "HV". The test load of 0.005 used corresponds to 0.049 N (multiplied by the proportionality constant 0.102). Vickers hardness is dimensionless.

[0078] 6) Amount of hydrogen fluoride released Using a Drager Accuro instrument, the amount of hydrogen fluoride released was measured using a Drager hydrogen fluoride test tube 0.5 / a for concentrations ranging from 0.5 to 15 ppm.

[0079] The MAK value (2001) of hydrogen fluoride is 2 ppm.

[0080] Preparation of metal substrate A 50 x 120 x 1~2 mm steel sheet (DC03) was used as the metal substrate. The following pretreatment was performed.

[0081] [Table 1]

[0082] Slotoclean AK 160 (containing NaOH and disodium metasilicate), Slotoclean EL DCG (containing NaOH, disodium metasilicate and sodium carbonate), and Slotoclean BEF30 (containing buta-2-in-1,4-diol and ethoxylated isotridecanol) are products of Dr. Ing. Max Schlotter.

[0083] reagent In particular, the following reagents were used in the experiment. VP 11 2571: A bath additive from Dr. Ing. Max Schlotter containing ammonium difluoride (15 to 20% by mass) as a conductive salt and polyamine (15 to 20% by mass) as a complexing agent. VP 11 2572: A bath additive from Dr. Ing. Max Schlotter containing 20 to 25% by mass of a sodium salt of an aromatic sulfonic acid polymer as an anionic dispersant. VP 11 2573: A bath additive from Dr. Ing. Max Schlotter containing 15 to 20% by mass of sodium sulfate salts of aliphatic alcohols having 6 to 20 carbon atoms as an anionic dispersant.

[0084] Culmo AN 11-1 Additive: A bath additive from Dr. Ing. Max Schlotter containing ethoxylated, propoxylated 2-propylheptanol (15 to 25% by mass).

[0085] SAT311 Tin Bath Additive: A bath additive from Dr. Ing. Max Schlotter containing ethoxylated, propoxylated 2-propylheptanol (15 to 25% by mass) and 1,2-dihydroxybenzene (1 to 7% by mass).

[0086] A bath additive from Dr. Ing. Max Schlotter containing C12-14 alkyl ether sulfates, including nickel bath additive SLOTONIK M:EO sodium salt (3 to 5% by mass).

[0087] Synthetic graphite (40nm) and highly conductive synthetic graphite (40nm) from Asbury Carbons, Inc.

[0088] (Examples 1 to 7 and Comparative Examples 1 and 2) For Examples 1 to 7 and Comparative Examples 1 and 2 ("CE1" and "CE2"), a tin-nickel electrolyte having the components shown in Table 1 was placed in a plastic beaker. To achieve this objective, SnCl2·2H2O and NiCl2·6H2O were first dissolved in a mixture of distilled water and bath additives while stirring at 55°C (250 rpm). Then, for Examples 1 to 7 and Comparative Example 2, the corresponding graphite powder was slowly added and dispersed while stirring (250 rpm). The median (d50) particle size of the graphite particles is given in parentheses as particle size in Table 1. The pH was optionally adjusted by adding hydrochloric acid. The volume of the electrolyte was 2 L.

[0089] After pretreatment of the steel sheet described above, it was electroplated under the conditions shown in Table 1. The electrolyte was thoroughly mixed using a 40 mm stirring rod (250 rpm). Each steel rod was connected as a cathode and immersed in the electrolyte to a depth of 10 cm. Two Ni electrodes (50 × 120 × 5 mm), placed parallel to the cathode and 4 cm apart on either side, acted as anodes. The anodes were also immersed to a depth of 10 cm. The two parallel anodes were connected in the order of electrolyte, cathode, and DC power supply.

[0090] Nickel and graphite content were measured, and the thickness of the deposited layer was determined.

[0091] [Table 2]

[0092] In Examples 1 to 7 and Comparative Examples 1 and 2, the tin-nickel layer was electrolytically deposited on the copper substrate with good adhesive strength. In Examples 1 to 7, regardless of the particle size, the metal was uniformly deposited in the layer and the graphite particles were uniformly introduced. In Comparative Example 2, when no anionic dispersant was added, no visible graphite was present in the tin-nickel layer, indicating that the graphite content was significantly less than 0.1% by mass.

[0093] Figure 1 shows photographs of the coated substrates of Comparative Example 1, Comparative Example 2, and Example 2. The introduction of graphite in Comparative Example 2 (Figure 1b) was so low that it was indistinguishable from Comparative Example 1 (Figure 1a), which was manufactured without the use of graphite particles. In contrast, the good introduction of graphite in Example 2 made it possible to observe a black tin-nickel layer (Figure 1c).

[0094] Figure 2 shows a scanning electron microscope image of the tin-nickel layer of Comparative Example 1. A uniform layer was observed at both magnifications of 100x (Figure 2a) and 30,000x (Figure 2b).

[0095] Figure 3a shows the graphite-containing tin-nickel layer of Example 2 at a magnification of 100x. A uniform layer was observed without any notable aggregates of graphite particles. Figure 3b shows the same layer at a magnification of 30,000x. Due to the graphite particles, the surface is rougher than that of the tin-nickel layer of Comparative Example 1. The surfaces of the graphite particles and the graphite-containing tin-nickel layer can be clearly distinguished here.

[0096] The hardness, tribological properties (coefficient of friction), and contact resistance of the tin-nickel layers formed in Examples 1 to 7 and Comparative Examples 1 and 2 were investigated. The above method was used to achieve this objective. The results are summarized in Table 1 above.

[0097] The conventional tin-nickel layer of Comparative Example 1 was characterized by a high hardness level. Furthermore, the contact resistance associated with the gold contact area was measured to be 75.7 mΩ, and the average coefficient of friction was measured to be 0.57. Due to the low or absence of graphite introduction, the physical properties of Comparative Example 1 were similar to those of Comparative Example 2.

[0098] In Examples 1 to 7, it was possible to significantly improve both the tribological properties and contact resistance of the tin-nickel layer compared to Comparative Examples 1 and 2. These examples thus demonstrate that the successful introduction of graphite particles into the electrolytically analyzed tin-nickel layer improved durability and conductivity compared to tin-nickel layers without graphite. Furthermore, it is noteworthy that it was possible to obtain layers with significantly higher hardness levels regardless of whether graphite was introduced.

[0099] Furthermore, it was found that lower average friction coefficients and contact resistances tended to be measured when the graphite particles were larger (Examples 1 to 3). When the graphite particles of the introduced graphite were small and the quantity was small, it tended to result in a somewhat higher average friction coefficient as well as a somewhat higher hardness level (Examples 4 to 6). Example 7, with a nickel content of only 16 mass%, also yielded very good tribo properties, namely a low average friction coefficient and low contact resistance. A high tin content of approximately 84 mass% was accompanied by a low hardness level.

[0100] (Example 8) Example 2 was repeated, with the pH set to 4.0 and the bath temperature to 60°C. The amount of hydrogen fluoride released was measured according to the method described above.

[0101] The amount of hydrogen fluoride released was below the detection limit, specifically less than 0.5 ppm. Therefore, the dispersed electrolyte can be used safely.

[0102] (Examples 9 and 10, and Comparative Examples 3 and 4) The same procedure as in Examples 1 and 7 and Comparative Example 1 was followed. For Examples 9 and Comparative Example 3 (CE3), nickel salts were not used to produce the tin layer. Similarly, for Examples 10 and Comparative Example 4 (CE4), tin salts were not used to produce the nickel layer. The electrolyte composition, electrodeposition conditions, and the composition of the formed layers are summarized in Table 2.

[0103] In Comparative Examples 3 and 4, conventional tin or nickel layers were deposited by electrolysis. As shown in Examples 9 and 10, it was also possible to produce graphite-containing tin or nickel layers without problems using the dispersed electrolyte according to the present invention. Significant improvements to the dispersed electrolyte (excluding nickel or tin salts) were not required to achieve this.

[0104] Furthermore, substantial improvements were observed in tribological properties (lower average coefficient of friction) and contact resistance in both the inherently softer tin layer and the harder, more brittle nickel layer (Table 2: Example 9 compared to Comparative Example 3, and Example 10 compared to Comparative Example 4). Thus, it was also possible to improve the durability and conductivity of the electrolytically analyzed tin or nickel layer.

[0105] [Table 3]

Claims

1. A dispersion electrolyte for electrodepositing a graphite-containing tin layer, a graphite-containing nickel layer, or a graphite-containing tin-nickel layer, - Sn at concentrations of 2 to 50 g / L 2+ Ions and / or Ni at concentrations of 0.2 to 70 g / L 2+ Ions and, - Graphite particles at concentrations of 5 to 200 g / L, - At least one anionic dispersant in a concentration of 1 to 25 g / L, - Sn 2+ and Ni 2+ Ion complexing agents, - Conductive salts, - Water and Includes, The pH ranges from 4 to 7. The anionic dispersant is a combination of at least one sulfate compound having an alkyl group, aralkyl group, or aromatic group, each having 6 to 24 carbon atoms, and at least one polymer having an aromatic sulfonic acid group as a sulfonate compound, wherein the underlying aromatic group each has 6 to 14 carbon atoms. Dispersion electrolyte.

2. The electrolyte contains Sn at a concentration of 5 to 45 g / L 2+ Ions and / or Ni at concentrations of 10 to 65 g / L 2+ A dispersed electrolyte according to claim 1, comprising ions.

3. The dispersed electrolyte according to claim 1 or 2, wherein the electrolyte contains graphite particles at a concentration of 20 to 150 g / L.

4. The dispersed electrolyte according to any one of claims 1 to 3, wherein the mass ratio of Ni:graphite in the electrolyte is 1:0.5 to 1:2, and / or the mass ratio of Sn:graphite in the electrolyte is 1:0.5 to 1:

5.

5. The dispersion electrolyte according to any one of claims 1 to 4, wherein the median (d50) particle size of the graphite particles is 20 nm to 20 μm.

6. The dispersion electrolyte according to any one of claims 1 to 5, wherein the sulfate compound having an alkyl group having 6 to 24 carbon atoms is selected from aliphatic alcohol sulfates, aliphatic alcohol polyether sulfates, and combinations thereof.

7. The dispersed electrolyte according to any one of claims 1 to 6, wherein the dispersant is present in the electrolyte at a concentration of 2 to 20 g / L.

8. The dispersion electrolyte according to any one of claims 1 to 7, wherein the complexing agent is an organic compound having at least three functional groups selected from an amino group, a carboxyl group, and a carboxylate group.

9. The dispersion electrolyte according to claim 8, wherein the complexing agent is an organic compound having at least two functional groups selected from primary, secondary, and tertiary amino groups.

10. The dispersion electrolyte according to claim 8 or 9, wherein the complexing agent is at least one selected from EDTA, DETA, DOTA, and DOTATOC.

11. The dispersed electrolyte according to any one of claims 1 to 10, wherein the complexing agent is present in the electrolyte at a concentration of 5 to 70 g / L.

12. The dispersed electrolyte according to any one of claims 1 to 11, wherein the conductive salt is at least one selected from sodium chloride, potassium chloride, ammonium chloride, sodium acetate, potassium acetate, ammonium acetate, ammonium fluoride, ammonium difluoride, sodium fluoride, and potassium fluoride.

13. The dispersed electrolyte according to any one of claims 1 to 12, wherein the conductive salt is present in the electrolyte at a concentration of 5 to 70 g / L.

14. A method for electrodepositing a graphite-containing tin layer, a graphite-containing nickel layer, or a graphite-containing tin-nickel layer, comprising electrodepositing the graphite-containing layer onto a metal substrate using the dispersed electrolyte described in any one of claims 1 to 13 at a temperature of 50 to 85°C.

15. The method according to claim 14, wherein the deposition is carried out at a current density of 0.1 to 10 A / dm2.

16. The method according to claim 14 or 15, wherein the graphite-containing layer is precipitated with a layer thickness of 4 to 30 μm.

17. A method for producing a coated metal substrate, comprising electrodeposition of a graphite-containing layer onto a metal substrate using the dispersed electrolyte solution described in Claim 1, wherein the metal substrate is coated with a graphite-containing tin layer, a graphite-containing nickel layer, or a graphite-containing tin-nickel layer, and the graphite-containing layer contains 0.1 to 8% by mass of graphite relative to the total mass of the graphite-containing layer.

18. The method according to claim 17, wherein the graphite-containing layer contains 0.5 to 3% by mass of graphite relative to the total mass of the graphite-containing layer.

19. The method according to claim 17 or 18, wherein the graphite-containing layer is a graphite-containing nickel layer having an average coefficient of friction of 0.4 or less and a Vickers hardness of at least HV300.

20. The method according to claim 17 or 18, wherein the graphite-containing layer is a graphite-containing tin-nickel layer, and the nickel content is 10 to 40% by mass relative to metallic tin and metallic nickel.

21. The method according to claim 20, wherein the nickel content is 13 to 18% by mass or 30 to 38% by mass relative to metallic tin and metallic nickel.

22. The method according to claim 21, wherein the nickel content of the graphite-containing tin-nickel layer is 32 to 37% by mass relative to metallic tin and metallic nickel, and further, the Vickers hardness is at least HV200.

23. The method according to any one of claims 20 to 22, wherein the average coefficient of friction of the graphite-containing tin-nickel layer is 0.4 or less.

24. The method according to any one of claims 20 to 23, wherein the contact resistance of the graphite-containing tin-nickel layer associated with the gold contact portion at 25°C is 50 mΩ (mOhm) or less.

25. Use of the dispersed electrolyte according to any one of claims 1 to 13 for manufacturing an electronic component having a graphite-containing tin layer, a graphite-containing nickel layer, or a graphite-containing tin-nickel layer.

26. The use according to claim 25, wherein the electrolyte is used to produce a graphite-containing tin-nickel layer as a protective layer on an electrical contact or electrode.

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