EP3797183A2

EP3797183A2 - Silver electrolyte for depositing dispersion silver layers and contact surfaces with dispersion silver layers

Info

Publication number: EP3797183A2
Application number: EP19745553.8A
Authority: EP
Inventors: Andreas Stadler; Robert SOTTOR; Reinhard Wagner; Christian Dandl; Sebastian Heitmüller
Original assignee: Dr Ing Max Schloetter GmbH and Co KG; Rosenberger Hochfrequenztechnik GmbH and Co KG
Current assignee: Dr Ing Max Schloetter GmbH and Co KG; Rosenberger Hochfrequenztechnik GmbH and Co KG
Priority date: 2018-07-05
Filing date: 2019-06-26
Publication date: 2021-03-31
Also published as: DE102018005352A1; CN112368422A; KR20210025599A; WO2020007407A2; US20210254230A1; WO2020007407A3; US12110606B2

Abstract

The invention relates to a silver electrolyte for depositing silver layers on substrates, comprising potassium silver cyanide, potassium cyanide having a content of at least 10 g/l, at least one grain refiner having a content of 0.2 to 10 g/l, at least one dispersing agent having a content of 1 to 10 g/l and at least one solid component having a content of 1 to 150 g/l, wherein the particles of the solid component have an average particle size (d₅₀) of 10 nm to 100 μm. The invention also relates to contact surfaces and methods for depositing such contact surfaces.

Description

Silver electrolyte for the deposition of dispersion silver layers and contact surfaces with dispersion silver layers

The invention relates to a silver electrolyte for the deposition of silver layers on substrates, a method for the deposition of a dispersion silver layer on a substrate and contact surfaces, an electrochemically deposited dispersion silver layer being arranged on a substrate. In addition, the invention relates to the use of the contact surfaces for electrical contacts in plug connections and the use of a silver electrolyte for coating a substrate by means of rack and / or drum plating.

Silver is an extremely versatile material. Because of its elasticity and softness, it can be processed in many different ways. Silver conducts heat and electricity best of all metals. This makes silver an interesting material for the electrical and electronics industry, among other things for the coating of surfaces, especially contact surfaces. Connectors and plug contacts that have the lowest possible electrical contact resistance are used as interfaces for the transmission of high electrical currents, which is why silver coatings are often used for contact elements that are installed in such a connector and that are responsible for the electrical contact when plugged in.

Silver electrolytes are used for the silver coating of substrates and for the production of contact surfaces. Various silver-containing solutions and dispersions are referred to as silver electrolytes which are used for electrochemical, in particular galvanic silvering of surfaces. Silver electrolyte solutions can contain a wide variety of other additives such as grain refiners, dispersants, brighteners or solid components.

The conductivity, contact resistance and coefficient of friction are particularly relevant for applications in the electrical and electronics sector, particularly for plugs and plug contacts. Especially with regard to the Increasing electromobility is expected to result in an increased demand for silver layers, in particular galvanically deposited silver layers.

If two silver-coated surfaces are moved over one another, a high level of force is required for this, since insertion and pulling forces act. This shows the disadvantage of contacts with silver surfaces, since these have a relatively high coefficient of friction, which leads to high insertion and removal forces, particularly in the case of plug contacts. The high coefficient of friction causes wear on silver surfaces, which severely limits the number of possible mating cycles. In addition, there is the problem that silver surfaces tend to cold weld. However, the contact resistance of a system of two silver-coated surfaces is advantageous.

DE 10346206 A1 describes a contact surface for electrical contacts. Finely dispersed graphite particles are embedded in the silver layer shown, which was produced by means of galvanic processes. The incorporation of graphite in the silver layer reduces the friction, which results in lower insertion forces, improved corrosion protection and a longer service life due to the increased wear protection of the contacts. At the same time, good electrical contacting is guaranteed.

DE 10 2008 030 988 B4 describes the electrochemical coating of a component, the layer having a metallic structure and carbon nanotubes and a dry lubricant being incorporated in this layer. The installation of carbon nanotubes increases the electrical conductivity and the heat dissipation of the layer, and by mixing it with other dry lubricants, the layer's wear behavior can be optimized for different applications.

DE 2543082 A1 discloses a silver electrolyte for the production of silver coatings, which also contains graphite, gloss additives and wetting agents. The graphite must be kept in suspension by pumping around the electrolyte-containing bath during the deposition.

The prior art describes silver electrolytes which additionally contain brighteners or other substances which improve deposition, such as xanthates, carbamates or Turkish red oil. Likewise

Electrolyte solutions shown that need mechanical intervention to the Keep solids suspended. Likewise, the prior art describes electrolytes which contain various solid constituents in order to obtain properties of deposited surfaces which are lost due to complex additive systems.

A disadvantage of known silver electrolytes for the deposition of silver on surfaces is that they do not disperse the substances to be dispersed sufficiently uniformly in the electrolyte, which on the one hand leads to an inhomogeneous distribution of the solid components in the deposited layers and on the other hand leads to the fact that no deposition takes place at all. Likewise, some electrolytes are not at all suitable for dispersing different types of solid constituents equally, so that pumping or stirring is necessary during the deposition, which has a negative effect on the flomogeneity of the surfaces obtained. In order to overcome these disadvantages, complex additive systems are often used, which can have a disadvantageous effect on the deposited surfaces and also lead to increased costs.

Known electrolytes are not suitable for adequately dispersing further particles, in particular dry lubricants, so that surfaces are obtained into which other substances such as additives are incorporated which have a negative influence on the dispersion layers produced. Among other things, the inhomogeneity of known surfaces is caused.

It is also disadvantageous that combinations of solid components, such as carbon nanotubes and dry lubricants, have often had to be used to achieve the appropriate surface properties and to compensate for the disadvantages of the additive systems. This also means that other substances have a negative impact on flomogenicity and also further increase costs. In addition, additives that are supposed to improve the separation make the process management and the process monitoring more complex and complex.

Another disadvantage of known electrolytes is that the deposition temperature must be chosen high in order to ensure adequate deposition. It is therefore the object of the invention to provide silver electrolytes which disperse solid constituents well and which at the same time make it possible to dispense with complex additive systems in order to achieve homogeneous deposition. Another object of the invention is to provide surfaces, in particular contact surfaces, which have increased wear resistance and good electrical conductivity. It is also an object of the invention to provide a deposition method for producing coated surfaces, in particular contact surfaces, with improved durability.

In the present case, durability means a reduction in the mating forces required, along with an increase in the possible mating cycles, a reduction in the cold welding, that is to say the welding of the soft silver layers due to microvibrations, and the maintenance of the most favorable contact resistance over the longest possible period.

The object on which the invention is based is achieved by a silver electrolyte according to claim 1. Preferred embodiments of the silver electrolyte according to the invention are specified in the subclaims, which can optionally be combined with one another.

The invention further relates to a method for depositing a dispersion silver layer on a substrate according to claim 8. Preferred embodiments of the method according to the invention are specified in the subclaims, which can optionally be combined with one another.

The invention further comprises a contact surface according to claim 12 below. Preferred embodiments of the contact surface according to the invention are specified in the subclaims, which can optionally be combined with one another.

The invention also relates to the use of the contact surfaces according to the invention for electrical contacts in plug connections and the use of the dispersion silver electrolyte according to the invention for coating a substrate by means of rack and / or drum application. According to the invention, the silver electrolyte for the deposition of 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 (dso) of 10nm - 100pm.

Surprisingly, it has been shown that various solid components can be homogeneously dispersed with a silver electrolyte in the composition shown, in order to obtain surfaces which have a dispersion silver layer with increased durability and good electrical conductivity. The electrolyte according to the invention is distinguished by the fact that it can be used to produce a wide variety of dispersion silver layers. Depending on the type and amount of the built-in solid components, these layers are characterized by their good contact resistance with an improved coefficient of friction or increased hardness. The durability, based on the abrasion or abrasion of these layers, exceeds that of simple silver layers. The electrolyte according to the invention is also particularly well suited for the use of solid components as substances to be dispersed. In addition, the electrolyte according to the invention gives silver layers which have good conductivity, so that the addition of further substances such as carbon nanotubes can be dispensed with. Furthermore, the electrolyte according to the invention can be used both at low and at high current densities. Thus, the electrolyte can be used for a wide variety of applications and can be used, for example, for drum and rack electroplating. The electrolyte is suitable for many types of electrochemical deposition. The solid constituents are dispersed homogeneously in the electrolyte according to the invention. The particularly homogeneous dispersion ensures the homogeneous incorporation of the solid components in the deposited silver layers. In addition, the use of the electrolyte according to the invention reduces the incorporation of additives, which regularly negatively influences the flomogenicity.

The electrolyte is also suitable for use with various solid components, so that the surface properties can be adapted to different applications. Another advantage of the electrolyte according to the invention is that the layer thickness varies and can be adapted to the respective application.

“Substituted” in the sense of the invention means that a hydrogen atom on a hydrocarbon is replaced by another atom or group of atoms.

In the sense of the invention, “solid component” means a component that is not in solution but is present in the electrolyte as a solid and is also referred to in connection with the present dispersion silver layers as a finely dispersed solid component.

In the sense of the invention, the average particle size (dso) indicates that 50% of the particles of a solid component have a smaller diameter than the specified value. The dsio value indicates that 90% of the particles of a solid component have a smaller diameter than the specified value.

“Grain refiners” in the sense of the invention are substances that shift the grain size of the silver deposition to smaller grain sizes.

“Dry lubricants” in the sense of the invention are substances that improve the sliding properties of a surface.

“Flart substances” in the sense of the invention are substances which are distinguished by their particularly high hardness. The silver electrolyte is a solution, preferably an aqueous solution. There may also be other solvents in the electrolyte.

Unless otherwise stated, all contents in g / L are based on the total volume of electrolyte below.

In an advantageous embodiment, the content of potassium silver cyanide 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.

The silver content in the electrolyte is advantageously 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.

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

The content of potassium silver cyanide in the electrolyte is preferably at most 150 g / L, preferably at most 125 g / L, more preferably at most 100 g / L and even more preferably at most 75 g / L.

The potassium cyanide content is preferably at least 20 g / L, preferably at least 50 g / L, more preferably at least 80 g / L, more preferably at least 100 g / L, even more preferably at least 120 g / L and most preferably at least 140 g / L ,

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

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.

The dispersant preferably contains alkyl sulfates with Ci-C25-alkyl radicals and preferably alkyl sulfates with Ci-C2o-alkyl radicals, which can be unsubstituted or optionally substituted. Preferably, the dispersant contains an alkyl sulfate having C 1 -C 2o alkyl groups which may be unsubstituted or optionally substituted, and more preferably a sodium alkyl sulfate having C 1 -C 2o alkyl groups which may be unsubstituted or can optionally be substituted. The alkyl radicals can be linear and / or branched.

The content of the at least one dispersant is preferably between 0.2 and 9 g / L, 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 L.

The content of the at least one solid component is preferably between 5 and 125 g / L, 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.

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

In an advantageous embodiment, the particles of the at least one solid component have an average particle size (dso) of 50 nm to 75 miti, preferably 100 nm to 50 miti, more preferably 500 nm to 35 gm and even more preferably from 1 gm to 20 gm. The diameter and thus also the average particle size (dso) of the solid components are determined by means of laser diffraction.

All types of organic or inorganic particles can be considered as solid constituents.

The at least one solid constituent is preferably a dry lubricant, a hard material or mixtures thereof, preferably a rock lubricant.

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. In the context of the invention, carbon modifications are understood to mean, in addition to diamond, Londsdaleit, fullerenes and graphite, also graphene, carbon nanotubes, carbon black, activated carbon, graphite fluoride, graphite oxide, Al2O3-coated graphite, non-graphitic and other forms of carbon.

According to an advantageous embodiment, the at least one solid component is selected from the group consisting of M0S2, WS2, SnS2, NbS2, TaS2, graphite, graphite fluoride, graphite oxide, hexagonal boron nitride, silver niobium selenide, TiN, SbN ₄ , T1B2, WC, TaC, B ₄ C, AI2O3, ZrÜ2, cubic BN, diamond, MoSe2, WSe2, TaSe2, NbSe2, SiC , AI2O3 coated graphite, AI2O3 coated M0S2 and AI2O3 coated WS2 or mixtures thereof, preferably made of M0S2, WS2, graphite, graphite oxide, hexagonal boron nitride or mixtures thereof, more preferably made of graphite, graphite oxide, M0S2, WS2 or mixtures thereof and even more preferred graphite.

Al203-coated solid particles are coated by coating the solid particles by means of controlled flydrolysis of AI (N03) 3 9 FI2O according to Fluang & Xiong (2008) (Fluang, Z .; Xiong, D. (2008): M0S2 coated with AI2O3 for N1-M0S2 / AI2O3 composite coatings by pulse electrodeposition, Surface & Coatings & Technology 202 (2008) 3208-3214).

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. The at least one solid component is preferably selected from the group consisting of M0S2, WS2, SnS2, NbS2, TaS2, hexagonal boron nitride, silver niobium selenide, TiN, SbN ₄ , T1B2, WC, TaC, B ₄ C, Al2O3, ZrÜ2, cubic BN , MoSe2, WSe2, TaSe2, NbSe2, SiC, AI2O3 coated M0S2 and AI2O3 coated WS2 or mixtures thereof, preferably made of M0S2, WS2, hexagonal boron nitride or mixtures thereof and more preferably made of M0S2, WS2 or mixtures thereof.

According to a further advantageous embodiment, the at least one solid component is selected from carbon modifications. The at least one solid constituent is preferably selected from the group consisting of graphite, graphite fluoride, graphite oxide, diamond, AI2O3-coated graphite or mixtures thereof, preferably of graphite, graphite fluoride, graphite oxide, AI2O3-coated graphite or mixtures thereof, more preferably of graphite, graphite oxide or mixtures thereof and more preferred graphite.

The electrolyte preferably contains at least one further solid component. This at least one further solid component can also be selected from the above-mentioned solid components.

The electrolyte can advantageously also contain a brightener. For this, an amount of 1 to 1000 mg / L, preferably less than 50 mg / L, is usually used, used. Examples of brighteners are phenylpropionic acid, phenylpropionic acid amide, triaminotriphenylmethane, 1 - (p-aminophenyl) -3-methylpyrazole, stearamidopropyldimethyl- (ß-hydroxyethyl) ammonium dihydrogen phosphate, 1, 5-diphenylcarbazide and chloral hydrate.

The silver electrolyte according to the invention can optionally contain further additives such as stabilizers, dispersants and / or grain refiners in order to further improve the performance of the electrolyte and to improve the properties of the deposited dispersion silver layer.

The aforementioned embodiments can also be combined.

Another object of the invention is a method for depositing a dispersion silver layer on a substrate according to the invention comprising the steps

a) presenting a silver electrolyte according to the invention,

b) introducing a substrate into the silver electrolyte, and

c) performing the deposition.

The method according to the invention comprises the deposition of a dispersion silver layer on a substrate from a silver electrolyte according to the invention according to one of the embodiments described above. The information given above on the electrolyte according to the invention also applies accordingly to the method.

In the method according to the invention, all of the usual substrates used for the deposition of silver layers and dispersion silver layers can be used. In the method according to the invention, the substrate preferably comprises a metal or a metal alloy. The dispersion silver layer is then deposited on the metal or the metal alloy. The metal or the metal alloy can, for example, contain or consist of copper and / or iron. Other intermediate layers made of other metals such as nickel or silver can also be present. Have such layers various functions such as increasing the adhesion of the dispersion silver layer to the substrate, protection against corrosion, protection against diffusion or improvement of other physical properties.

Galvanic or external currentless processes can be used as the deposition process. Examples of galvanic processes are drum, frame or strip galvanization.

The substrate is preferably cleaned before coating, preferably degreased. The substrate can be subjected to various pretreatment steps. Here, copper layers, nickel layers and / or further silver layers can be deposited.

The substrate is preferably pre-silvered before step a). The substrate is preferably nickel-plated before the pre-silvering.

According to an advantageous embodiment, the temperature when carrying out the deposition in step c) is 1 ° C. to 50 ° C., preferably 5 ° C. to 40 ° C., more preferably 5 ° C. to 35 ° C., even 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.

In an advantageous embodiment, the current density in step c) is from 0.03 A / dm ² to 1.2 A / dm ² , preferably from 0.05 A / dm ² to 1.0 A / dm ² , more preferably from 0.075 A / dm ² to 1.0 A / dm ² , more preferably from 0.1 A / dm ² to 0.95 A / dm ² and even more preferably from 0.15 A / dm ² to 0.90 A / dm ² ,

According to an advantageous embodiment, the method is drum and / or rack electroplating.

The duration of the deposition is to be selected according to the desired layer thickness to be achieved and the application, drum and / or rack electroplating. Due to the lower current densities for drum and rack electroplating compared to other processes, the duration of the deposition is longer. Basically, the duration of the deposition is not limited.

The duration of the deposition in step c) is preferably at least 5 min, preferably at least 7 min, more preferably at least 9 min and even more preferably at least 11 min. The duration of the deposition in step c) is preferably from 5 minutes to 100 minutes, preferably from 7 minutes to 75 minutes and more preferably from 10 minutes to 50 minutes.

Step a) is preferably carried out before step b), more preferably step b) is followed by step c).

Another 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 an average particle size (dso) of 10 nm - 100 pm.

The information given above regarding the electrolyte according to the invention and the method according to the invention also apply accordingly to the contact surface. The finely dispersed solid constituent can thus be selected from the solid constituents mentioned above. All of the aforementioned substrates can be used as substrates for the contact surfaces according to the invention.

The contact surfaces according to the invention allow only one contact partner to be equipped with a dispersion silver surface if a dry lubricant is used as the solid component. The other contact partner can consist of a conventional metal surface without a solid component, in particular a dry lubricant component. In this way, costs can be reduced. However, both contact partners can also be equipped with a dispersion silver surface.

The contact surfaces according to the invention are distinguished by their advantageous wear resistance. In particular, the durability of mating processes with regard to wear due to micro movements, so-called fretting, has been significantly improved. Such micro movements occur, for example, in plugs in the automobile due to the vibrations during operation of the vehicle. Temperature fluctuations can also lead to wear caused by micro movements. The contact surface preferably also contains at least one further solid component. The at least one further solid component is preferably a dry lubricant or a hard material. The at least one further solid component is preferably selected from the solid components mentioned above for the electrolyte according to the invention, which correspondingly also apply to the contact surface.

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

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

According to an advantageous embodiment of the contact surface, the dispersion silver layer contains the at least one finely dispersed solid component in an amount of at least 3.0% by weight, preferably at least 3.1% by weight, more preferably at least 3.2% by weight, even more preferably at least 3.3% by weight and even more preferably at least 3.5% by weight based on the total weight of the dispersion silver layer.

The dispersion silver layer preferably also contains the at least one finely dispersed solid constituent in a quantity range from 3.0 to 30.0% by weight, preferably from 3.1 to 25% by weight, more preferably from 3.1 to 20% by weight more preferably from 3.1 to 15% by weight, even more preferably from 3.2% by weight to 10% by weight and even more preferably from 3.5% by weight to 10% by weight, based on the total weight of the dispersion silver layer ,

The at least one finely disperse solid component is preferably selected from silicates, sulfides, carbides, nitrides, oxides, selenides, tellurides, organic and inorganic polymers and carbon modifications. 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. The at least one finely disperse solid component is preferably selected from the group consisting of M0S2, WS2, SnS2, NbS2, TaS2, hexagonal boron nitride, silver niobium selenide, TiN, SbN ₄ , PB2, WC, TaC, B ₄ C, Al2O3, ZrÜ2 , cubic BN, MoSe2, WSe2, TaSe2, NbSe2, SiC, AI2O3 coated M0S2 and AI2O3 coated WS2 or mixtures thereof, preferably made of M0S2, WS2, hexagonal boron nitride or mixtures thereof and more preferably made of M0S2, WS2 or mixtures thereof.

According to a further advantageous embodiment of the contact surface, the at least one finely dispersed solid component is selected from carbon modifications. The at least one finely disperse solid component is preferably selected from the group consisting of graphite, graphite fluoride, graphite oxide, diamond, Al 2 O 3 -coated graphite or mixtures thereof, preferably graphite, graphite fluoride, graphite oxide, Al 2 O 3 -coated graphite or mixtures thereof, more preferably made of graphite, graphite oxide or Mixtures thereof, and more preferably graphite.

According to an advantageous embodiment, the at least one finely dispersed solid component is selected from the group consisting of M0S2, WS2, SnS2, graphite, graphite oxide, graphite fluoride, hexagonal boron nitride, silver niobium selenide, SiC, AI2O3 coated graphite, AI2O3 coated M0S2 and AI2O3 or coated WS2 Mixtures thereof, preferably of M0S2, WS2, graphite and hexagonal boron nitride or mixtures thereof.

In a further advantageous embodiment of the contact surface, the at least one finely dispersed solid component is selected from the group consisting of graphite, M0S2, WS2 or the mixtures thereof, preferably made of graphite, and the dispersion silver layer contains the at least one finely dispersed solid component in an amount of at least 3.0% by weight, preferably at least 3.1% by weight, more preferably at least 3.2% by weight, more preferably at least 3.3% by weight and even more preferably at least 3.5% by weight, based on the Total weight of the dispersion silver layer. In a further advantageous embodiment of the contact surface, the dispersion silver layer has a coefficient of friction m at 0.3 N after 100 cycles of less than 1.4, preferably less than 1.2, more preferably less than 1.0, more preferably less than 0, 8, more preferably less than 0.6, and more preferably from 0.4.

According to a further advantageous embodiment of the contact surface, the electrical contact resistance at 1.0 N after 100 cycles is less than 1.0 itiW, preferably less than 0.8 itiW, more preferably less than 0.75 itiW, even more preferably less than 0.7 itiW and even more preferably less than 0.65 itiW.

In a further advantageous embodiment of the contact surface, the dispersion silver layer has a coefficient of friction m at 1.0 N after 100 cycles of less than 1.0, preferably less than 0.8, more preferably less than 0.6, more preferably less than 0, 5 and even more preferably less than 0.45.

The layer thickness of the deposited dispersion silver layer is preferably between 0.5 miti to 200 miti, preferably 1 miti to 100 miti, particularly preferably 1.1 to 25 miti.

The contact surface is advantageously a micro-rough surface. The micro roughness has an advantageous effect on the tribological and electrical properties.

The contact surface preferably has a micro-roughness, described below by the average roughness Ra, of at least 0.05 miti, preferably of at least 0.1 miti, more preferably of at least 0.2 miti and even more preferably of at least 0.3 miti.

The contact surface preferably has a micro-roughness, described below by the mean roughness Ra, in the range from 0.05 miti to 5 miti, preferably from 0.1 miti to 4 miti, more preferably from 0.2 miti to 3 miti and even more preferably from 0 , 3 miti to 2.5 miti.

In an advantageous embodiment, the contact surfaces have a song fretting life 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. The aforementioned contact surfaces can be produced by means of the method according to the invention described above. The invention thus also comprises a contact surface obtainable by the method according to the invention, an electrochemically deposited dispersion silver layer being arranged on a substrate, and the dispersion silver layer comprising particles of at least one finely dispersed solid constituent having an average particle size (dso) of 10 nm - 100 pm contains.

The above-described information on the electrolyte according to the invention, the method according to the invention and the contact surfaces according to the invention accordingly also apply to the contact surfaces obtainable by means of the method according to the invention. The finely dispersed solid constituent can thus be selected from the solid constituents mentioned above. All of the aforementioned substrates can be used as substrates for the contact surfaces according to the invention.

Another object of the invention relates to the use of the contact surface according to the invention for electrical contacts in plug connections.

Another object of the invention relates to the use of the dispersion silver electrolyte according to the invention for coating a substrate by means of rack and / or drum application.

Further advantages of the invention result from the following description of preferred exemplary 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.

embodiments

materials

Brass sheets (material: CuZn39Pb3) from Metaq GmbFI with the dimensions 75 mm x 17 mm x 1 mm were used for the tests. The used Bronze balls (material: CuSn6) from KUGELPOMPEL HSI-Solutions GmbH had a diameter of 3 mm.

KCN was purchased from Bücherl and K [Ag (CN) 2] was purchased from Umicore.

ELFIT 73, a glossy silver electrolyte based on KCN / potassium silver cyanide, SLOTOSIL BS 1591, a silver electrolyte based on KCN / potassium silver cyanide, SLOTOSIL BS 1592, a gloss additive, and ALTIX, a glossy silver electrolyte based on KCN / potassium silver cyanide for the deposition of hard silver Ing.. Max Schlotter GmbH & Co. KG related. Likewise, CUPRUM 1 1, a gloss additive, CUPRUM 12, a wetting agent, and the anti-tarnish concentrate AG 1 1 1 from Dr.-Ing. Max Schlotter GmbH & Co. KG related.

SLOTOSIL SG 191 1 and SLOTOSIL SG 1912 are additives for silver electrolytes based on KCN / potassium silver cyanide for the dispersion separation by Dr.-Ing. Max Schlotter GmbH & Co. KG. SLOTOSIL SG 191 1 contains a naphthalenesulfonic acid derivative as a grain-refining additive. SLOTOSIL SG 1912 contains an alkyl sulfate as a dispersion stabilizing additive.

The graphites used come from Graphit Kropfmühl AG. The individual graphite powders have different average particle sizes from dso = 3 pm (graphite UF 1) to dso = 1 1.5 pm (graphite EDM - L 98) and also vary in conductivity.

The sulfide particles (M0S2, WS2) used come from Tribotecc GmbH and have an average particle size of dso = 1 1 pm and d9o = 23 pm (M0S2 MOSXF) or dso = 3 pm and dsio = 6 pm (WS2 WS 2).

measurement methods

wear test

Coated bronze balls are rubbed over coated brass sheets on the wear test bench. A weight of 0.3 N or 1.0 N was applied to the ball. This rubs with the selected force over a distance of 3 mm at a frequency of 1 Hz over the coated brass sheet. This is repeated for 100 cycles. During the test, the friction force is measured with a U9C load cell (HBM) and with the normal force to the unitless one Coefficient of friction m offset. In addition, the contact resistance at the contact between the coated brass sheet and the ball is measured after each cycle. The contact resistance is measured using a four-wire method with a digital multimeter 2750 / E (Keithley company).

Determination of fretting life by song

The same test equipment is used for this test as for the regular wear test. The friction path is 50 pm long, the frequency and the normal force remain at 1 Hz and a normal force from 0.3 N to 1.0 N as described in the wear test. The comparison criterion is the service life I according to Song, which is Rinitiai + 5 itiW is defined and based on common test standards (Song, J .; Wang, L .; Koch, C. (2013): Correlation between friction and wear properties and service life of surface protection layers of electrical contacts. In: Song, J. (ed.) : Electrical and optical connection technology 2013. Conference proceedings of the GMM conference. 4th Symposium Connectors). The structure of the testing apparatus is described in Song et al. described. The target size is 50,000 cycles.

Measurement of micro roughness (as mean roughness Ra)

The micro roughness (as mean roughness Ra) was measured by means of an optical measuring method with a gsurf explorer confocal microscope (Fiersteller: nanofocus).

Determination of solids content

The solids content (in% by weight) was determined by means of X-ray diffractometry. For this purpose, X-ray diffractograms of the deposited thin layers were recorded with a D8 Advance DaVinci Design X-ray diffractometer (Bruker company) with Lynxeye solid-state detector using Cu Ka radiation. The corresponding diffractograms were evaluated by means of Rietveld refinement with the DIFFRAC ^plus TOPAS version 4.2 program (Bruker).

Determination of the diameter of the solid components (dso, dw) The diameter of the particles of the solid components, the average particle size dso and the dsio values were determined by means of laser diffraction using a Helos device from Sympatec.

Coating of sheet brass and bronze balls

galvanization

Specimen bodies were coated with dispersion silver layers and pure silver layers in order to obtain contact surfaces. Brass plates and bronze balls were coated for the wear, contact resistance and fretting life tests. The test specimens were first copper-plated and then the parts were coated with a pure silver layer (comparative examples, VB) or a dispersion silver layer (inventive examples, EB).

Between each step was rinsed thoroughly with water.

The galvanization of the brass sheets and bronze balls included the following steps:

1st and 2nd step: degreasing of the substrates by known methods; first alkaline degreasing step at 60 ° C for 1 min with ultrasound support. Second alkaline electrolytic degreasing step at room temperature (25 ° C) over a treatment time of 2 to 3 min.

Step 3: Etching copper with a bath of sulfuric acid, complexing agent-free copper activation. The activation is used at room temperature (25 ° C) for 0.5 min.

4th step: treatment with a bright copper bath, which is a cyanide electrolyte for the deposition of shiny surfaces. The electrolyte, consisting of 10 g / l KOH, 1 15 g / l KCN, 64 g / l CuCN and 1.5 ml / l gloss additive CUPRUM 1 1; 2.5 ml / l basic additive CUPRUM 12 was operated at 60 ° C. The electrolyte was used for the rack goods with 2 A / dm ² . For the drum variant with 1.25 A / dm ² .

5th step: 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]). The pre-silvering was carried out at room temperature (25 ° C). 2 A / dm ^{2 were} chosen as the cathodic current density.

Step: deposit the pure silver layer (comparative examples, VB) or the dispersion silver layers (inventive examples, EB).

The brass sheets were hung on a frame for coating. Only the brackets for the brass sheets were conductive on the frame.

The bronze balls were coated as drums. The balls were placed with silver-plated steel balls as filling material in a sieve basket with a mesh size of 0.8 mm and attached to a galvanizing device. A galvanizing device with a pump was used to deposit the dispersion layers.

The electrolytes used can be found in Table 1. Pure silver layers (VB1, VB2, VB3)

The brass sheets were moved with a stroke movement of 0.7 m / min. The deposition took place at a current density of 0.37 A / dm ² (0.1 A / sheet) for 22 min. The balls were moved in the drum at 12 rpm and the silver layer was deposited at a current density of 0.25 A / dm ² (1.85 A for 70 balls with about 300 g filler material) for 25 minutes.

Coating with dispersion silver layers (EB1 to EB6)

The brass sheets were moved with a stroke movement of 0.7 m / min, the dispersing device (ULTRA-TURRAX T 25, company IKA-Werke GmbH & Co. KG) was set to 5,000 rpm for the deposits of examples EB1 to EB4 and for the deposits of Examples EB5 to EB6 set to 10,000 rpm. The deposition took place at a current density of 0.85 A / dm ² (0.23 A / sheet) for EB1 to EB 4 each for 22 min, for EB5 and EB6 each for 20 min.

The balls were moved in the drum at 2 rpm and the silver layer was deposited at a current density of 0.5 A / dm ² (4.1 A for 70 balls with about 300 g filler material) for 13 minutes.

Step: anti-tarnish post-treatment; The tarnish protection, 160 mL / L tarnish protection concentrate AG 1 1 1, was used at 50 ° C and pH 5.3. The coated test specimens were immersed in the tarnish protection for 2 min. It was then rinsed with deionized water and dried.

Table 1 shows the compositions of pure silver baths and dispersion silver baths.

Table 1: Compositions of pure silver baths and dispersion silver baths

Table 2 shows the results of the wear and fretting tests. In addition, the contact resistances of the surfaces are shown after 100 cycles. The micro-roughness of the surfaces was also determined in the form of the average roughness, Ra. The graphite contents of the graphite-containing dispersion silver layers were also measured. Table 2: Measured values

n.a .: not determined

The dispersion silver layers with graphite, EB1 to EB4, or the disulfides, EB5 and EB6, are a great step forward. In the wear test with 0.3 N and 100 cycles, these layers remain below a coefficient of friction of 0.4, while the pure silver layers according to Examples VB1 to VB3 have at least a significantly higher coefficient of friction. The electrical contact resistance of the dispersion silver layer layers remains below 1.0 mQ while the contact resistance is higher with the pure silver layers, with the VB2 even over 2.5 mQ.

The wear test at 1, 0 N and 100 cycles shows the dispersion silver layers with graphite and the disulfides, even after the 100 cycles, very low coefficients of friction. The conductivity of these dispersion silver layers is even slightly higher than that of the pure silver layers. The fretting tests at 1.0 N show that the graphite silver layers according to examples 1, 3, 4 and 6 (EB1, EB 3, EB4 and EB 6) according to the invention are superior to the pure silver layers of comparative examples 1 to 3 (VB1 to VB3).

It can be seen that the dispersion silver layers in Examples EB1 to EB6 according to the invention consistently have good properties and in particular have the combination of low friction coefficients, low contact resistance and high fretting resistance. None of the comparative examples shows the combination of advantageous properties.

Furthermore, it is shown that contact surfaces with a graphite or metal sulfide particle content, i.e. Solids content of more than 3.0% by weight, based on the total weight of the dispersion silver layer, shows very good results.

Claims

claims

1. Silver electrolyte for the deposition of silver layers on substrates comprising 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 (dso) of 10 nm - 100 gm.

2. Silver electrolyte according to claim 1, wherein the at least one grain refiner is selected from naphthalenesulfonic acid, naphthalenesulfonic acid derivatives or mixtures thereof.

3. Silver electrolyte according to one of the preceding claims, wherein the at least one dispersant contains sodium alkyl sulfates with Ci-C2o-alkyl radicals, which may be unsubstituted or optionally substituted.

4. Silver electrolyte according to one of the preceding claims, wherein the particles of the at least one solid component have an average particle size (dso) of 1 gm to 20 gm.

5. Silver electrolyte according to one of the preceding claims, wherein the at least one solid component is selected

a. from the group consisting of graphite, graphite fluoride, graphite oxide, diamond, AI2O3 coated graphite or mixtures thereof, preferably graphite, graphite fluoride, graphite oxide, AI2O3 coated graphite or mixtures thereof, more preferably made of graphite, graphite oxide or mixtures thereof and more preferably made of graphite; or

b. from the group consisting of M0S2, WS2, SnS2, NbS2, TaS2, hexagonal boron nitride, silver niobium selenide, TiN, SbN ₄ , PB2, WC, TaC, B ₄ C, AI2O3, ZrÜ2, cubic BN, MoSe2, WSe2, TaSe2, NbSe2, SiC, AI2O3 coated M0S2 and AI2O3 coated WS2 or mixtures thereof, preferably from M0S2, WS2, hexagonal boron nitride or mixtures thereof and more preferably from M0S2, WS2 or mixtures thereof; or c. from the group consisting of M0S2, WS2, SnS2, NbS2, TaS2, graphite, graphite fluoride, graphite oxide, hexagonal boron nitride, silver niobium selenide, TiN, Si ₃ N, T1B2, WC, TaC, B ₄ C, AI2O3, ZrÜ2, cubic BN , Diamond, MoSe2, WSe2, TaSe2, NbSe2, SiC, AI2O3 coated graphite, AI2O3 coated M0S2 and AI2O3 coated WS2 or mixtures thereof, preferably made of M0S2, WS2, graphite, graphite oxide, hexagonal boron nitride or mixtures thereof, more preferably made of graphite, graphite M0S2, WS2 or mixtures thereof and more preferably made of graphite.

6. A method for depositing a dispersion silver layer on a substrate comprising the steps

a) presenting a silver electrolyte according to claims 1 to 5,

b) introducing a substrate into the silver electrolyte, and

c) performing the deposition.

7. The method according to claim 6, wherein the temperature in step c) is 15 ° C to 25 ° C and / or wherein the current density in step c) of 0.05 A / dm ² to 1.0 A / dm ² and preferably 0.1 A / dm ² to 0.95 A / dm ² .

8. The method according to claims 6 or 7, wherein the method is a drum and / or rack galvanization.

9. contact surface, wherein an electrochemically deposited dispersion silver layer is arranged on a substrate, and

10. Contact surface according to claim 9, wherein the at least one finely dispersed solid component is selected

a. from the group consisting of M0S2, WS2, SnS2, NbS2, TaS2, hexagonal boron nitride, silver niobium selenide, TiN, Si ₃ N ₄ , T1B2, WC, TaC, B ₄ C, AI2O3, ZrÜ2, cubic BN, MoSe2, WSe2, TaSe2, NbSe2, SiC, AI2O3 coated M0S2 and AI2O3 coated WS2 or mixtures thereof, preferably from M0S2, WS2, hexagonal boron nitride or mixtures thereof and more preferably from M0S2, WS2 or mixtures thereof; or b. from the group consisting of graphite, graphite fluoride, graphite oxide, diamond, AI2O3 coated graphite or mixtures thereof, preferably made of graphite, graphite fluoride, graphite oxide, AI2O3 coated graphite or mixtures thereof, more preferably made of graphite, graphite oxide or mixtures thereof and more preferably made of graphite; or

c. from the group consisting of M0S2, WS2, SnS2, graphite, graphite oxide, graphite fluoride, hexagonal boron nitride, silver niobium selenide, SiC, AI2O3 coated graphite, AI2O3 coated M0S2 and AI2O3 coated WS2 or mixtures thereof, preferably made of M0S2, hexagon, graphite Boron nitride or mixtures thereof.

1 1. Contact surface according to claims 9 to 101, wherein the dispersion silver layer contains the at least one finely dispersed solid component in an amount of at least 3.0% by weight based on the total weight of the dispersion silver layer.

12. Contact surface according to claim 9, wherein the at least one finely dispersed solid component is selected from the group consisting of graphite, M0S2, WS2 or mixtures thereof, preferably made of graphite, and the dispersion silver layer contains the at least one finely dispersed solid component in an amount contains at least 3.0% by weight, based on the total weight of the dispersion silver layer.

13. Contact surface according to claims 9 to 12, wherein

the dispersion silver layer has a coefficient of friction m at 0.3 N after 100 cycles of less than 1.4; or

b.the electrical contact resistance at 1.0 N after 100 cycles is less than 1.0 itiW; or

c. the dispersion silver layer has a coefficient of friction m at 1.0 N after 100 cycles of less than 1.0.

14. Use of the contact surface according to one of claims 9 to 13 for electrical contacts in plug connections.

5. Use of a dispersion silver electrolyte according to one of claims 1 to 5 for coating a substrate by means of rack and / or drum application.