Contact surfaces with dispersion silver layers

Abstract

contact surface, wherein an electrochemically deposited dispersion silver layer is arranged on a substrate, wherein the dispersion silver layer contains particles of at least one finely dispersed solid component with a mean particle size (d 50 ) from 10nm - 100µm; wherein the dispersion silver layer contains at least one finely dispersed solid component in a quantity range of 0.5 wt.% to 10 wt.% based on the total weight of the dispersion silver layer; and wherein the contact surface has a microroughness, described by the mean roughness Ra, in the range of 0.05 µm to 20 µm.

Description

[0001] The invention relates to contact surfaces, wherein an electrochemically deposited dispersion silver layer is arranged on a substrate. The invention further relates to the use of these contact surfaces for electrical contacts in connectors.

[0002] Silver is an extremely versatile material. Its malleability and softness allow it to be processed in a wide variety of ways. Of all metals, silver is the best conductor of heat and electricity. This makes silver an attractive material for the electrical and electronics industries, particularly for coating surfaces, especially contact surfaces. Plugs and connectors are used as interfaces for transmitting high electrical currents and therefore require the lowest possible electrical contact resistance. For this reason, silver coatings are frequently used on contact elements that are integrated into such connectors and are responsible for the electrical contact when plugged in.

[0003] Silver electrolytes are used for silver coating of substrates and for the production of contact surfaces. The term "silver electrolyte" refers to various silver-containing solutions and dispersions used for the electrochemical, and especially galvanic, silvering of surfaces. Silver electrolyte solutions can contain a wide variety of other additives, such as grain refiners, dispersants, brighteners, or solid components.

[0004] For applications in the electrical and electronics sector, especially for plugs and connectors, conductivity, contact resistance, and coefficient of friction are particularly relevant. Especially with regard to the increasing prevalence of electromobility, a higher demand for silver coatings, particularly electroplated silver coatings, is expected.

[0005] When two silver-coated surfaces are moved across each other, a high force is required due to insertion and withdrawal forces. This highlights the disadvantage of contacts with silver surfaces, as they exhibit a relatively high coefficient of friction, which leads to particularly high insertion and withdrawal forces in plug contacts. This high coefficient of friction causes wear on silver surfaces, severely limiting the number of possible mating cycles. Furthermore, silver surfaces are prone to cold welding. However, the contact resistance of a system consisting of two silver-coated surfaces is advantageous.

[0006] German patent DE 103 46 206 A1 describes a contact surface for electrical contacts. Finely dispersed graphite particles are embedded in the silver layer shown, which was produced using electroplating. The incorporation of graphite into the silver layer reduces friction, resulting in lower insertion forces, improved corrosion protection, and a longer service life for the contacts due to increased wear resistance. At the same time, good electrical contact is ensured.

[0007] German patent DE 10 2008 030 988 A1 describes the electrochemical coating of a component, wherein the coating has a metallic structure and incorporates carbon nanotubes and a dry lubricant. The incorporation of carbon nanotubes increases the electrical conductivity and heat dissipation of the coating, and the addition of other dry lubricants allows the coating to be optimized for different applications with regard to its wear behavior.

[0008] German patent DE 25 43 082 A1 discloses a silver electrolyte for the production of silver coatings, which also contains graphite, brightening agents, and a wetting agent. The graphite must be kept in suspension during deposition by pumping the electrolyte-containing bath.

[0009] EP 2 634 293 A2 relates to composite materials made of carbon black particles and metal. DE 15 21 025 A1 discloses a galvanic cyanide silver bath for depositing bright silver coatings. CN 1 05 297 095 A discloses a functional plating layer made of a pure silver / silver graphite composite layer and a method for its production. DE 10 2015 102 453 A1 discloses a ribbon-shaped substrate made of a film with several substrate units for the production of chip card modules, as well as a chip card module, an electronic device with such a chip card module, and a method for producing a substrate. WO 91 / 14 808 A1 discloses a method for applying silver-graphite dispersion coatings with an electrolyte containing an alkali metal silver cyanide, conducting salt, graphite, a wetting agent, and a brightening additive.DE 41 33 466 A1 relates to a movable electrical sliding contact with a surface in sliding contact with a corresponding mating contact, in which graphite particles are dispersed in a silver matrix. WO 02 / 101 119 A1 relates to a solid mixture containing dithiocarbamoyldithiocarbazate and a xanthate. Prior art describes silver electrolytes that additionally contain brightening agents or other substances that improve deposition, such as xanthates, carbamates, or Turkey red oil. Electrolyte solutions are also described that require mechanical intervention to keep the solid components in suspension. Furthermore, prior art describes electrolytes containing various solid components to preserve properties of deposited surfaces that are lost through complex additive systems.

[0010] A disadvantage of known silver electrolytes for depositing silver onto surfaces is that they do not disperse the substances to be dispersed sufficiently uniformly within the electrolyte. This leads, on the one hand, to an inhomogeneous distribution of the solid components in the deposited layers and, on the other hand, to a partial or complete lack of deposition. Similarly, some electrolytes are not suitable for dispersing different types of solid components equally, necessitating pumping or stirring during deposition, which negatively impacts the homogeneity of the resulting surfaces. To overcome these disadvantages, complex additive systems are often employed, which can have a detrimental effect on the deposited surfaces and also lead to increased costs.

[0011] Known electrolytes are not suitable for sufficiently dispersing further particles, especially dry lubricants, resulting in surfaces into which further substances such as additives are incorporated, negatively affecting the generated dispersion layers. This, among other things, causes the inhomogeneity of known surfaces.

[0012] A further disadvantage is that combinations of solid components, such as carbon nanotubes and dry lubricants, often have to be used to achieve the desired surface properties and compensate for the drawbacks of the additive systems. This also leads to the need for additional substances to negatively impact homogeneity and further increase costs. Furthermore, additives intended to improve deposition make process control and monitoring more complex and time-consuming.

[0013] Another disadvantage of known electrolytes is that the deposition temperature must be chosen to be high in order to ensure sufficient deposition.

[0014] It is therefore an object of the invention to provide silver electrolytes that disperse solid components well and simultaneously allow the elimination of complex additive systems to achieve homogeneous deposition. A further object of the invention is to provide surfaces, in particular contact surfaces, that exhibit increased wear resistance and good electrical conductivity. Likewise, it is an object of the invention to provide a deposition process for producing coated surfaces, in particular contact surfaces, with improved durability.

[0015] Durability in this case means a reduction in the required insertion forces accompanied by an increase in the possible insertion cycles, a reduction in cold welding, i.e. the welding of the soft silver layers due to micro-vibrations, as well as maintaining the most favorable possible contact resistance over the longest possible period of time.

[0016] The problem underlying the invention is solved by a contact surface according to claim 1. Preferred embodiments of the contact surface according to the invention are specified in the dependent claims, which can optionally be combined with one another.

[0017] The invention also relates to the use of the contact surfaces according to the invention for electrical contacts in plug connections.

[0018] The silver electrolyte for depositing silver layers on substrates comprises, a) Potassium silver cyanide, b) Potassium cyanide with a content of at least 10 g / L, c) at least one grain refiner with a content of 0.2 to 10 g / L, d) at least one dispersant with a content of 1 to 10 g / L and e) at least one solid component with a content of 1 to 150 g / L, wherein the particles of the solid component have an average particle size (d 50 ) from 10nm - 100µm.

[0019] Surprisingly, it has been shown that various solid components can be homogeneously dispersed using a silver electrolyte with the composition described, resulting in surfaces with a dispersion silver layer exhibiting increased durability and good electrical conductivity. The electrolyte is characterized by its ability to produce a wide variety of dispersion silver layers. Depending on the type and quantity of incorporated solid components, these layers are distinguished by their good contact resistance, improved coefficient of friction, or increased hardness. The durability of these layers, in terms of abrasion resistance, surpasses that of simple silver coatings. Furthermore, the electrolyte is particularly well-suited for using solid components as dispersible materials.Furthermore, the electrolyte forms silver layers with excellent conductivity, eliminating the need for additional substances such as carbon nanotubes. The electrolyte can also be used at both low and high current densities. Therefore, it is suitable for a wide range of applications, including strip plating.

[0020] The solid components are homogeneously dispersed in the electrolyte. This particularly homogeneous dispersion ensures the homogeneous incorporation of the solid components into the deposited silver layers.

[0021] Furthermore, the use of the electrolyte reduces the incorporation of additives, which regularly have a negative impact on homogeneity.

[0022] Furthermore, the electrolyte is suitable for use with various solid components, allowing the surface properties to be adapted to different applications. Another advantage of the electrolyte is that the layer thickness can be varied and adjusted to the specific application.

[0023] “Substituted” within the meaning of the invention means that a hydrogen atom on a hydrocarbon is replaced by another atom or group of atoms.

[0024] For the purposes of the invention, "solid component" means a component that is not in solution but exists as a solid in the electrolyte and, in connection with the present dispersion silver layers, is also referred to as a finely dispersed solid component.

[0025] In the context of the invention, the mean particle size (d) 50) indicates that 50% of the particles of a solid component have a smaller diameter than the specified value.

[0026] “Grain refiners” within the meaning of the invention are substances that shift the grain size of the silver deposition to smaller grain sizes.

[0027] “Dry lubricants” within the meaning of the invention are substances that improve the sliding properties of a surface.

[0028] “Hard materials” within the meaning of the invention are materials that are characterized by their particularly high hardness.

[0029] The silver electrolyte is a solution, preferably an aqueous solution. Other solvents may also be present in the electrolyte.

[0030] Unless otherwise stated, all concentration values ​​in g / L refer to the total volume of electrolyte.

[0031] In an advantageous embodiment, the potassium silver cyanide content in the electrolyte is at least 10 g / L, preferably at least 25 g / L, more preferably at least 40 g / L and even more preferably at least 50 g / L.

[0032] Advantageously, the silver content in the electrolyte is at least 15 g / L, preferably at least 20 g / L, more preferably at least 25 g / L and even more preferably at least 27 g / L.

[0033] Preferably, the silver content in the electrolyte is between 1 and 100 g / L, more preferably between 5 and 50 g / L and even more preferably between 10 and 30 g / L.

[0034] Preferably, the potassium silver cyanide content in the electrolyte is at most 150 g / L, more preferably at most 125 g / L, more preferably at most 100 g / L and even more preferably at most 75 g / L.

[0035] Preferably the potassium cyanide content is at least 20 g / L, more preferably at least 50 g / L, more preferably at least 80 g / L, even more preferably at least 100 g / L, still more preferably at least 120 g / L and most preferably at least 140 g / L.

[0036] In an advantageous embodiment, the at least one grain refiner is selected from naphthalenesulfonic acid, naphthalenesulfonic acid derivatives or mixtures thereof.

[0037] The grain refiner content is advantageously between 0.2 and 8 g / L, preferably between 0.3 and 6 g / L, more preferably between 0.4 and 5 g / L and even more preferably between 0.5 and 3 g / L.

[0038] The dispersant preferably contains alkyl sulfates with C1-C 25 -Alkyl groups and preferably alkyl sulfates with C1-C 20 -Alkyl groups, which may be unsubstituted or optionally substituted. Preferably, the dispersant contains an alkyl sulfate with C1-C 20-Alkyl groups, which may be unsubstituted or optionally substituted, and preferably a sodium alkyl sulfate with C1-C 20 -Alkyl groups, which can be unsubstituted or optionally substituted. The alkyl groups can be linear and / or branched.

[0039] Preferably, the content of the at least one dispersing agent is between 0.2 and 9 g / L, more preferably between 0.3 and 8 g / L, more preferably between 0.4 and 7 g / L and even more preferably between 0.5 and 6 g / L.

[0040] Preferably, the content of the at least one solid component is between 5 and 125 g / L, more preferably between 10 and 100 g / L, more preferably between 15 and 90 g / L and even more preferably between 20 and 80 g / L.

[0041] Preferably, the content of the at least one solid component is at least 5 g / L, more preferably at least 10 g / L, more preferably at least 15 g / L, even more preferably at least 20 g / L, even more preferably at least 30 g / L and most preferably at least 40 g / L.

[0042] In an advantageous embodiment, the particles of the at least one solid component have an average particle size (d 50 ) from 50 nm to 75 µm, preferably 100 nm to 50 µm, more preferably 500 nm to 35 µm, and even more preferably from 1 µm to 20 µm. The diameters, and thus also the mean particle size (d), 50 The composition of the solid components is determined using laser diffraction.

[0043] All types of organic or inorganic particles are suitable as solid components.

[0044] Preferably, the at least one solid component is a dry lubricant, a hard material or mixtures thereof, preferably a dry lubricant.

[0045] In an advantageous embodiment, the at least one solid component is selected from silicates, sulfides, carbides, nitrides, oxides, selenides, tellurides, organic and inorganic polymers, and carbon modifications. For the purposes of this invention, carbon modifications include not only diamond, lonsdaleite, fullerenes, and graphite, but also graphene, carbon nanotubes, carbon black, activated carbon, graphite fluoride, graphite oxide, Al₂O₃-coated graphite, non-graphitic carbon, and other forms of carbon.

[0046] According to an advantageous embodiment, the at least one solid component is selected from the group consisting of MoS2, WS2, SnS2, NbS2, TaS2, graphite, graphite fluoride, graphite oxide, hexagonal boron nitride, silver niobium selenide, TiN, Si3N4, TiB2, WC, TaC, B4C, Al2O3, ZrO2, cubic BN, diamond, MoSe2, WSe2, TaSe2, NbSe2, SiC, Al2O3-coated graphite, Al2O3-coated MoS2 and Al2O3-coated WS2 or mixtures thereof, preferably MoS2, WS2, graphite, graphite oxide, hexagonal boron nitride or mixtures thereof, more preferably graphite, graphite oxide, MoS2, WS2 or mixtures thereof and even more preferably graphite.

[0047] Al2O3-coated solid particles are produced by coating the solid particles using controlled hydrolysis of Al(NO3)3 · 9 H2O according to Huang & Xiong (2008) (Huang, Z.; Xiong, D. (2008): MoS2 coated with Al2O3 for Ni-MoS21A12O3 composite coatings by pulse electrodeposition. Surface & Coatings & Technology 202 (2008) 3208-3214).

[0048] According to an advantageous embodiment, the at least one solid component is selected from silicates, sulfides, carbides, nitrides, oxides, selenides, tellurides, organic and inorganic polymers. Preferably, the at least one solid component is selected from the group consisting of MoS₂, WS₂, SnS₂, NbS₂, TaS₂, hexagonal boron nitride, silver niobium selenide, TiN, Si₃N₄, TiB₂, WC, TaC, B₄C, Al₂O₃, ZrO₂, cubic BN, MoSe₂, WS₂, TaSe₂, NbSe₂, SiC, Al₂O₃-coated MoS₂ and Al₂O₃-coated WS₂ or mixtures thereof, preferably from MoS₂, WS₂, hexagonal boron nitride or mixtures thereof, and more preferably from MoS₂, WS₂ or mixtures thereof.

[0049] According to a further advantageous embodiment, the at least one solid component is selected from carbon modifications. Preferably, the at least one solid component is selected from the group consisting of graphite, graphite fluoride, graphite oxide, diamond, Al₂O₃-coated graphite or mixtures thereof, more preferably from graphite, graphite fluoride, graphite oxide, Al₂O₃-coated graphite or mixtures thereof, more preferably from graphite, graphite oxide or mixtures thereof, and even more preferably graphite.

[0050] Preferably, the electrolyte contains at least one further solid component. This at least one further solid component can also be selected from the solid components mentioned above.

[0051] Advantageously, the electrolyte can also contain a glazing agent. Typically, an amount of 1 to 1000 mg / L, preferably less than 50 mg / L, is used. Examples of glazing agents are phenylpropionic acid, phenylpropionamide, triaminotriphenylmethane, 1-(p-aminophenyl)-3-methylpyrazole, stearamidopropyldimethyl-(β-hydroxyethyl)ammonium dihydrogen phosphate, 1,5-diphenylcarbazide, and chloral hydrate.

[0052] The silver electrolyte may optionally contain further additives such as stabilizers, dispersants and / or grain refiners to further improve the performance of the electrolyte and enhance the properties of the deposited dispersion silver layer.

[0053] The aforementioned embodiments can also be combined.

[0054] Another subject is a process for depositing a dispersion silver layer on a substrate, comprising the steps of a) Presentation of a silver electrolyte, b) Introducing a substrate into the silver electrolyte, and c) Performing the separation.

[0055] The process comprises the deposition of a dispersed silver layer onto a substrate consisting of a silver electrolyte according to one of the embodiments described above. The information given above regarding the electrolyte also applies accordingly to the process.

[0056] This process can utilize all common substrates used for the deposition of silver layers and dispersed silver layers. The substrate preferably comprises a metal or metal alloy. The dispersed silver layer is then deposited onto the metal or metal alloy. The metal or metal alloy can, for example, contain or consist of copper and / or iron. Additional intermediate layers of other metals, such as nickel or silver, may also be present. These layers serve various functions, such as increasing the adhesion of the dispersed silver layer to the substrate, providing protection against corrosion, preventing diffusion, or improving other physical properties.

[0057] Electroplating or electroless processes can be used as deposition methods. Examples of electroplating processes include barrel, rack, or strip plating.

[0058] The substrate is preferably cleaned, and preferably degreased, before coating. The substrate can undergo various pretreatment steps. These steps can include the deposition of copper layers, nickel layers, and / or additional silver layers.

[0059] Preferably, the substrate is pre-silvered before step a). Preferably, the substrate is nickel-plated before pre-silvering.

[0060] According to an advantageous embodiment, the temperature during the deposition process in step c) is 1°C to 50°C, preferably 5°C to 40°C, more preferably 5°C to 35°C, more preferably 10°C to 30°C, more preferably 15°C to 25°C, more preferably 17°C to 22°C and most preferably 20°C.

[0061] In an advantageous embodiment, the current density in step c) is 1.2 A / dm². 2 up to 35.0 A / dm 2 preferably of 1.5 A / dm² 2 up to 30.0 A / dm 2, preferred from 2.0 A / dm 2 up to 25.0 A / dm 2 , even more preferred than 2.5 A / dm 2 up to 25.0 A / dm 2 and even more preferably from 2.5 A / dm 2 up to 20.0 A / dm 2 .

[0062] According to an advantageous embodiment, the method is strip electroplating.

[0063] The deposition time should be selected according to the desired layer thickness and the application (e.g., strip plating). In principle, there is no limit to the deposition time.

[0064] Preferably the duration of the deposition in step c) is from 0.1 min to 20 min, preferably from 0.15 min to 15 min and more preferably from 0.3 min to 10 min.

[0065] Preferably, step a) is performed before step b), and further preferably, step b) is followed by step c).

[0066] One object of the invention relates to a contact surface, wherein, according to the invention, an electrochemically deposited dispersion silver layer is arranged on a substrate, and wherein the dispersion silver layer contains particles of at least one finely dispersed solid component with a mean particle size (d 50 ) from 10nm - 100µm.

[0067] The above-mentioned information regarding the electrolyte and the process also applies accordingly to the contact surface. The finely dispersed solid component can therefore be selected from the solid components mentioned above. All of the aforementioned substrates can be used as substrates for the contact surfaces according to the invention.

[0068] The contact surfaces according to the invention allow only one contact partner to be equipped with a dispersion silver surface when a dry lubricant is used as the solid component. The other contact partner can consist of a conventional metal surface without any solid component, in particular without any dry lubricant component. This can reduce costs. However, both contact partners can also be equipped with a dispersion silver surface.

[0069] The contact surfaces according to the invention are characterized by their advantageous wear resistance. In particular, their resistance to wear caused by micro-movements, so-called fretting, during mating operations is significantly improved. Such micro-movements occur, for example, in automotive connectors due to vibrations during vehicle operation. Temperature fluctuations can also lead to wear caused by micro-movements.

[0070] Preferably, the contact surface contains at least one further solid component. Preferably, this at least one further solid component is a dry lubricant or a hard material. More preferably, the at least one further solid component is selected from the solid components mentioned above for the electrolyte, which also apply accordingly to the contact surface.

[0071] In an advantageous embodiment, the particles of the at least one finely dispersed solid component have a mean particle size (d 50 ) from 50 nm to 75 µm, preferably 100 nm to 50 µm, more preferably 500 nm to 35 µm and even more preferably from 1 µm to 20 µm. The same applies to particles of other solid components.

[0072] The content of at least one finely dispersed solid component in the dispersion silver layer can be varied by changing the deposition conditions. This allows the surface properties to be adjusted with regard to contact resistance and wear resistance.

[0073] The dispersion silver layer contains at least one finely dispersed solid component in a quantity range of 0.5 to 10 wt.% and, even more preferably, of 3.1 wt.% to 10 wt.% based on the total weight of the dispersion silver layer.

[0074] Preferably, the dispersion silver layer contains at least one finely dispersed solid component in an amount of at least 3.0 wt.%, preferably at least 3.1 wt.%, more preferably at least 3.2 wt.%, even more preferably at least 3.3 wt.% and even more preferably at least 3.5 wt.% based on the total weight of the dispersion silver layer.

[0075] Preferably, the at least one finely dispersed solid component is selected from silicates, sulfides, carbides, nitrides, oxides, selenides, tellurides, organic and inorganic polymers and carbon modifications.

[0076] According to an advantageous embodiment of the contact surface, the at least one finely dispersed solid component is selected from silicates, sulfides, carbides, nitrides, oxides, selenides, tellurides, organic and inorganic polymers. Preferably, the at least one finely dispersed solid component is selected from the group consisting of MoS₂, WS₂, SnS₂, NbS₂, TaS₂, hexagonal boron nitride, silver niobium selenide, TiN, Si₃N₄, TiB₂, WC, TaC, B₄C, Al₂O₃, ZrO₂, cubic BN, MoSe₂, WS₂, TaSe₂, NbSe₂, SiC, Al₂O₃-coated MoS₂ and Al₂O₃-coated WS₂ or mixtures thereof, preferably from MoS₂, WS₂, hexagonal boron nitride or mixtures thereof, and more preferably from MoS₂, WS₂ or mixtures thereof.

[0077] According to a further advantageous embodiment of the contact surface, the at least one finely dispersed solid component is selected from carbon modifications. Preferably, the at least one finely dispersed solid component is selected from the group consisting of graphite, graphite fluoride, graphite oxide, diamond, Al₂O₃-coated graphite or mixtures thereof, more preferably graphite, graphite fluoride, graphite oxide, Al₂O₃-coated graphite or mixtures thereof, more preferably graphite, graphite oxide or mixtures thereof, and even more preferably graphite.

[0078] According to a further advantageous embodiment, the at least one finely dispersed solid component is selected from the group consisting of MoS2, WS2, SnS2, graphite, graphite oxide, graphite fluoride, hexagonal boron nitride, silver niobium selenide, SiC, Al2O3 coated graphite, Al2O3 coated MoS2 and Al2O3 coated WS2 or mixtures thereof, preferably MoS2, WS2, graphite and hexagonal boron nitride or mixtures thereof.

[0079] In a further embodiment of the contact surface, the at least one finely dispersed solid component is selected from graphite, MoS2, WS2 or mixtures thereof, preferably graphite, and the dispersion silver layer contains the at least one finely dispersed solid component in an amount of at least 3.0 wt.%, preferably at least 3.1 wt.%, more preferably at least 3.2 wt.%, more preferably at least 3.3 wt.% and even more preferably at least 3.5 wt.% based on the total weight of the dispersion silver layer.

[0080] Preferably, the dispersion silver layer has a coefficient of friction µ at 0.3 N after 100 cycles of less than 1.4, preferably less than 1.2, more preferably less than 1.0, even more preferably less than 0.8, even more preferably less than 0.6 and even more preferably less than 0.4.

[0081] Preferably, the electrical contact resistance at 1.0 N after 100 cycles is less than 1.0 mΩ, more preferably less than 0.8 mΩ, more preferably less than 0.75 mΩ, more preferably less than 0.7 mΩ and even more preferably less than 0.65 mΩ.

[0082] Preferably, the dispersion silver layer has a coefficient of friction µ at 1.0 N after 100 cycles of less than 1.0, preferably less than 0.8, more preferably less than 0.6, even more preferably less than 0.5 and even more preferably less than 0.45.

[0083] Preferably the thickness of the deposited dispersion silver layer is between 0.5 µm and 200 µm, preferably 1 µm and 100 µm, and particularly preferably 1.1 µm and 25 µm.

[0084] The contact surface is advantageously micro-rough. This micro-roughness has a beneficial effect on the tribological and electrical properties.

[0085] The contact surface has a micro-roughness, hereinafter described by the mean roughness value Ra, of at least 0.05 µm, preferably at least 0.1 µm, more preferably at least 0.2 µm and even more preferably at least 0.3 µm.

[0086] The contact surface has a micro-roughness, described below by the mean roughness value Ra, in the range of 0.05 µm to 20 µm, preferably from 0.1 µm to 10 µm, more preferably from 0.2 µm to 6 µm and even more preferably from 0.3 µm to 5 µm.

[0087] Preferably, the contact surfaces have a fretting lifetime according to Song at 1.0 N of more than 7500 cycles, preferably of more than 10,000 cycles, more preferably of more than 15,000 cycles, even more preferably of more than 20,000 cycles and even more preferably of more than 25,000 cycles.

[0088] The aforementioned contact surfaces can be produced using the method described above. Thus, the invention also includes a contact surface obtainable by the method, wherein an electrochemically deposited dispersion silver layer is arranged on a substrate, and wherein the dispersion silver layer contains particles of at least one finely dispersed solid component with a mean particle size (d 50 ) from 10 nm - 100 µm.

[0089] The aforementioned information regarding the electrolyte, the process, and the contact surfaces according to the invention also applies accordingly to the contact surfaces obtainable by means of the process. The finely dispersed solid component can thus be selected from the solid components mentioned above. All of the aforementioned substrates can be used as substrates for the contact surfaces according to the invention.

[0090] Another aspect of the invention relates to the use of the contact surface according to the invention for electrical contacts in plug connections.

[0091] Another aspect of the invention relates to the use of the dispersion silver electrolyte for coating a substrate by means of ribbon application.

[0092] Further advantages of the invention will become apparent from the following description of preferred embodiments, which, however, are in no way to be understood as limiting. All embodiments of the invention can be combined with one another within the scope of the invention. Examples of implementation Materials

[0093] For the tests, copper sheets (material: CuFe2P) from Wieland-Werke AG were used. The average roughness Ra of the uncoated sheets is 0.47 µm.

[0094] KCN was sourced from the company Bücherl and K[Ag(CN)2] was sourced from the company Umicore.

[0095] SLOTOSIL SG 1911 and SLOTOSIL SG 1912 are additives for silver electrolytes based on KCN / potassium silver cyanide for dispersion deposition, manufactured by Dr.-Ing. Max Schlötter GmbH & Co. KG. SLOTOSIL SG 1911 contains a naphthalenesulfonic acid derivative as a grain-refining additive. SLOTOSIL SG 1912 contains an alkyl sulfate as a dispersion-stabilizing additive.

[0096] CUPRUM 11, a gloss additive, CUPRUM 12, a wetting agent, and the tarnish protection concentrate AG 111 were sourced from the company Dr.-Ing. Max Schlötter GmbH & Co. KG.

[0097] The graphite particles used are from Graphit Kropfmühl AG. The UF2 grade graphite powder used has an average particle size of d 50 = 4.5 µm. Measurement methods: Determination of solid component content

[0098] The solid content (in wt.%) was determined using energy-dispersive X-ray spectroscopy (EDX). Measurements were performed on the deposited thin films using an X-Flash Detector 410-M (Bruker AXS Microanalysis GmbH) in a JSM-6610 LV electron microscope (manufacturer: JEOL) with an excitation voltage of 25 kV. The measurements were evaluated using the Esprit software (Bruker). Determination of the diameters of the solid components (d 50 )

[0099] The diameters of the particles of the solid components in the form of the mean particle size d 50 was determined using laser diffraction with a Helos device from the company Sympatec. Measurement of microroughness (as mean roughness value Ra)

[0100] The microroughness (as mean roughness value Ra) was determined using an optical measurement method with a confocal 3D laser scanning microscope VK-X100 (manufacturer: Keyence Corporation) and subsequent evaluation with the program Multi file analyzer (Keyence Corporation). Coating of copper sheets, electroplating

[0101] Test specimens were coated with dispersion silver layers to create contact surfaces. The copper sheets were first copper-plated, then pre-silver-plated, and subsequently coated with a dispersion silver layer.

[0102] Thorough rinsing with water was performed between each step.

[0103] The electroplating of the copper sheets comprised the following steps: Steps 1 and 2: Degreasing of the substrates according to known methods; first alkaline degreasing step at 60°C for 1 minute with ultrasound assistance. Second alkaline electrolytic degreasing step at room temperature (25°C) for a treatment time of 2 to 3 minutes. Step 3: Etching of copper with a bath of sulfuric acid, complexing agent-free copper activation solution. The activation process takes place at room temperature (25°C) for 0.5 minutes. Step 4: Treatment with a copper luster bath, which was a cyanide electrolyte for depositing bright surfaces. The electrolyte, consisting of 10 g / l KOH, 115 g / l KCN, 64 g / l CuCN, and 1.5 ml / l brightening additive CUPRUM 11; 2.5 ml / l base additive CUPRUM 12, was operated at 60°C. The electrolyte was treated with 2 A / dm³. 2 used. Step 5: The pre-silvering was carried out in a pre-silvering bath with a cyanide electrolyte with a low silver content (120 g / l KCN; 3.7 g / l K[Ag(CN)₂]). 2]The pre-silver plating was carried out at room temperature (25°C). The cathodic current density was 2 A / dm². 2 chosen. Step 6: Deposition of the dispersion silver layers

[0104] The sheets, pre-treated according to the procedure described above, were mounted on a rotary cell for coating.

[0105] The electrolyte had the following composition: KCN: 154 g / L K[Ag(CN)2]: 56 g / L SLOTOSIL SG 1911: 20 mL / L SLOTOSIL SG 1912: 20 mL / L Graphite UF2: 70 g / L

[0106] The sheets were coated at different rotational speeds to simulate strip speeds of 30 m / min, 60 m / min, and 100 m / min. The coating process took place at a current density of 2.5 A / dm². 2 , 5 A / dm 2 , 10 A / dm 2 , 15 A / dm 2 or 20 A / dm 2 Instead. Detailed information on the individual experiments is listed in Table 1.

[0107] Step 7: Anti-tarnish post-treatment; The anti-tarnish agent, 160 ml / l anti-tarnish concentrate AG 111, was used at 50°C and pH 5.3. The coated specimens were immersed in the anti-tarnish agent for 2 minutes. They were then rinsed with deionized water and dried.

[0108] Table 1 shows the results of the characterization of the deposited dispersion silver layers. The graphite content of the graphite-containing dispersion silver layers was determined by EDX. Table 1: Results of strip electroplating Examples Speed ​​(m / min) Current density (A / dm³) 2 ) Coating duration (min) Electrolyte temperature (°C) Graphite content EDX (wt.%) Average roughness Ra (µm) 1 100 2,5 8 21 1,76 1,38 2 60 2,5 8 21 3,13 2,26 3 30 2,5 8 21 4,98 2,51 4 100 5 4 21 1,69 1,09 5 60 5 4 22 3,73 2,95 6 30 5 4 22 6,39 2,43 7 100 10 2 22 1,33 1,00 8 60 10 2 22 6,45 3,66 9 30 10 2 22 8,32 4,39 10 100 15 1,5 22 2,23 1,08 11 60 15 1,5 22 6,36 4,90 12 30 15 1,5 22 8,69 6,33 13 100 20 1 23 2,05 1,00 14 60 20 1 23 7,54 4,85 15 30 20 1 23 7,63 16,03

[0109] The results shown in Table 1 demonstrate that the electrolyte is suitable for the deposition of dispersed silver layers. Compared to electrolytes known from the prior art for the production of dispersed silver layers, the achievable particle counts are significantly higher, representing a considerable improvement.

[0110] Unlike known electrolytes used for the production of dispersion silver layers, this electrolyte is specifically suitable for the deposition of dispersion silver layers using a reel-to-reel process.

[0111] By incorporating solid components, particularly a dry lubricant, into the dispersion silver layer, dispersion silver layers with significantly better sliding properties are obtained compared to pure silver layers, especially at high concentrations of solid components. A high solid particle concentration in the layer is particularly advantageous for wear caused by micro-vibrations (fretting). At small contact points, high solid particle concentrations increase the likelihood that a sufficient quantity of solid particles is present in the contact area to reduce wear. This property is particularly important for the contact surfaces of connectors and, as the examples show, is achieved with this process.

Claims

[1] Contact surface, wherein an electrochemically deposited dispersion silver layer is arranged on a substrate, wherein the dispersion silver layer contains particles of at least one finely dispersed solid component with a mean particle size (d 50 ) from 10nm - 100µm; wherein the dispersion silver layer contains at least one finely dispersed solid component in a quantity range of 0.5 wt.% to 10 wt.% based on the total weight of the dispersion silver layer; and wherein the contact surface has a microroughness, described by the mean roughness Ra, in the range of 0.05 µm to 20 µm. [2] Contact surface according to claim 1, wherein the at least one finely dispersed solid component is selected from the group consisting of MoS2, WS2, SnS2, NbS2, TaS2, hexagonal boron nitride, silver niobium selenide, TiN, Si3N4, TiB2, WC, TaC, B4C, Al2O3, ZrO2, cubic BN, MoSe2, WSe2, TaSe2, NbSe2, SiC, Al2O3 coated MoS2 and Al2O3 coated WS2 or mixtures thereof, preferably MoS2, WS2, hexagonal boron nitride or mixtures thereof and more preferably MoS2, WS2 or mixtures thereof. [3] Contact surface according to claim 1, wherein the at least one finely dispersed solid component is selected from the group consisting of graphite, graphite fluoride, graphite oxide, diamond, Al2O3 coated graphite or mixtures thereof, preferably graphite, graphite fluoride, graphite oxide, Al2O3 coated graphite or mixtures thereof, more preferably graphite, graphite oxide or mixtures thereof and more preferably graphite. [4] Contact surface according to claim 1, wherein the at least one finely dispersed solid component is selected from the group consisting of MoS2, WS2, SnS2, graphite, graphite oxide, graphite fluoride, hexagonal boron nitride, silver niobium selenide, SiC, Al2O3 coated graphite, Al2O3 coated MoS2 and Al2O3 coated WS2 or mixtures thereof, preferably MoS2, WS2, graphite and hexagonal boron nitride or mixtures thereof. [5] Contact surface according to claims 1 to 4, wherein the dispersion silver layer contains at least one finely dispersed solid component in a quantity range of 1.0 to 10 wt.% and preferably 3.1 wt.% to 10 wt.% based on the total weight of the dispersion silver layer. [6] Use of the contact surface according to any one of claims 1 to 5 for electrical contacts in plug connectors.