CH717789B1 - Process for the galvanic gold-plating of contact elements for connectors and contact elements gold-plated with the help of this process. - Google Patents

Abstract

The present disclosure relates to a method for galvanically gold-plating a contact element for connectors. The method includes degreasing the contact element and activating the degreased contact element. The method also includes nickel-plating the activated contact element by means of galvanic nickel-plating using a galvanic nickel-plating bath and/or by means of chemical nickel-plating using a chemical nickel-plating bath. The method further includes electroplating the nickel-plated contact element using a gold-plating bath to form the gold-plated contact element, the gold-plating bath containing gold ions in the form of a cyanide complex, preferably [Au(CN) 2 ] - , for example in the form of K[Au(CN) 2 ], includes. The disclosure further relates to gold-plated contact elements manufactured using this method.

Description

TECHNICAL AREA

The present invention relates to a method for the galvanic gold-plating of contact elements for connectors and gold-plated connectors using this method.

STATE OF THE ART

Various methods for galvanizing mass-produced goods, in particular connectors, are known. A major area of application for the gold plating of mass-produced goods is in particular the gold plating of contact elements for connectors. A drum electrode is often used as the cathode in such processes. In addition to the cathode, an anode and an electrolytic solution containing a gold salt, various additives are often used for different purposes: there are, for example, additives for accelerating gold deposition, additives for regulating metal deposition and layer structure, additives for regulating the luster properties of the gold-plated product, additives for regulating the conductivity of the electrolytic solution and additives for regulating the pH of the electrolytic solution. Depending on their function, the additives can be of an inorganic or organic nature, for example. Buffer salts, for example, are known as additives for regulating the pH of the electrolyte solution.

It is also known to add one or more other metal salts to the electrolyte solution in addition to a gold salt. The admixture of salts containing cobalt, iron and/or nickel is known, for example, to form hard gold (e.g. AuCo, AuFe, AuNi). Various alloys can be formed by adding other metals or salts of other metals.

The choice of the exact method and the process parameters used for the galvanic gold-plating of contact elements and the exact composition of the electrolyte solution have a significant influence on the quality, the properties and the nature of the gold-plated contact elements obtained. However, the methods known from the prior art for electroplating contact elements with gold have numerous disadvantages. Some of these disadvantages relate to the process itself and some disadvantages relate to the gold-plated contact elements obtained.

The gold-plated contact elements that can be produced using methods known from the prior art have the following disadvantages in particular: the gold coating is often distributed irregularly over the surface of the contact elements and, in particular, has an irregular thickness. In addition, many previously known methods are not able to gold-plate the contact elements continuously, so that the gold-plated contact elements still have uncoated surface sections in some cases. Furthermore, the gold coating is often not chemically stable, cannot be bonded, cannot be soldered, is not abrasion-resistant and/or susceptible to wear.

[0006] In addition, the course of the deposition rate and the deposition speed is often inhomogeneous. A possible reason for the inhomogeneous development of the deposition rate is that it depends in part on the current density.

[0007] Many previously known methods for electroplating contact elements for connectors with gold lead to an inhomogeneous distribution of the layer thickness. The layer thickness can, for example, sometimes differ considerably between different contact elements of the same batch. The previously known methods also have the disadvantage that the individual gold-plated contact elements also have layer thicknesses that are distributed considerably inhomogeneously over their surface. In some processes, the inhomogeneous distribution of the layer thickness is at least partly due to the fact that the exact geometry of the object to be gilded has an influence on the distribution of the galvanic gold coating ("bone effect"). The inhomogeneous distribution of the layer thickness, in combination with the required minimum layer thickness of the gold coating, leads to an increased consumption of gold.

PRESENTATION OF THE INVENTION

It is therefore an object of the invention to provide a method for the galvanic gold-plating of contact elements for connectors, which avoids some of the disadvantages of the prior art. It is in particular the object of the invention to create a method for the electroplating of gold on contact elements for plug connectors, which allows the production of particularly thin gold coatings.

[0009] This object is achieved by the method according to the invention for electroplating with gold, as defined in the independent claim, and by the gold-plated contact elements produced using this method. Some preferred embodiments follow from the dependent claims and the entire disclosure.

In a first aspect, the general object is achieved by a method for electroplating a contact element for connectors, which comprises degreasing the contact element and activating the degreased contact element. The method also includes nickel-plating the activated contact element by means of galvanic nickel-plating using a galvanic nickel-plating bath and/or by means of chemical nickel-plating using a chemical nickel-plating bath. The method also includes galvanic gold plating of the nickel-plated contact element using a gold-plating bath to form the gold-plated contact element. The gilding bath comprises gold ions in the form of a cyanide complex, preferably [Au(CN)2]<->, for example in the form of K[Au(CN)2].

An advantage of some embodiments of the method according to the invention is that it allows the reliable production of thin gold layers, in particular in the range of up to 3 μm thick, for example 0.1 μm-0.3 μm thick. A further advantage of some embodiments is the high reproducibility of the method for different mass-produced goods, in particular for different contact elements for connectors, which can have different geometries and/or can consist of different materials, for example.

In one embodiment, the method according to the invention also enables the formation of continuous and homogeneous surface coatings, even for contact elements with complex three-dimensional structures, which include, for example, cavities and/or overhangs.

The gold-plated contact elements formed by the method according to the invention can also be soldered and/or are abrasion-resistant. They are also resistant to wear and offer excellent protection against corrosion. In particular for currents in the low-load range, the gold layers, which are preferably homogeneous and non-porous, do not lead to current or voltage differences.

[0014] Due to their inert and non-porous gold surface, the gold-plated contact elements formed by the method according to the invention also have a long-term shelf life.

In some embodiments, the disclosed method for electroplating a contact element for connectors using vibratory conveyors, such as vibratory conveyor units, is carried out.

The disclosed method for galvanic gold plating of a contact element for connectors is preferably carried out by means of barrel plating. In this embodiment, the disclosed method is suitable for the simultaneous gold plating of a large number of contact elements for connectors, for example up to 50,000 contact elements. As those skilled in the art know, barrel plating refers to a process for plating bulk goods using a barrel plating apparatus. Bulk goods include in particular small parts with a volume of up to 20 cm 3 , in particular up to 10 cm 3 , and/or a weight of up to 300 g, in particular up to 20 g. Bulk goods and also small parts include, for example, screws, rivets, nuts and contact elements for connectors.

[0017] A barrel electroplating apparatus comprises a barrel which is filled with the bulk goods to be electroplated. The drum preferably comprises a drum body and a drum cover for closing the drum. The drum body and optionally also the drum cover define holes that are smaller than the mass-produced goods. The holes allow liquids to flow freely into and out of the drum. The barrel is typically rotated about an axis of rotation during barrel plating. The drum preferably has a polygonal cross-section, but can also be cylindrical.

[0018] The drum further comprises at least one contacting member for making contact with the bulk goods to be electroplated. The at least one contacting element can be integrated into an inner wall of the drum, for example, and can include contacting surfaces. The at least one contacting element can additionally or alternatively comprise, for example, a contacting rod arranged inside the drum and/or a contacting clapper arranged inside the drum. The contacting rod can, for example, correspond to the axis of rotation of the drum. The contacting member is electrically conductive and preferably consists of a contacting pad.

In some embodiments, the gold electroplating step is performed by barrel plating.

The disclosed method for electroplating gold is carried out using an electroplating system. The electroplating system comprises an electroplating bath, a first electrode arranged within the electroplating bath, and a second electrode arranged within the electroplating bath, which is conductively connected to the first electrode via a power source. The contact element to be gold-plated can be connected, for example, as a second electrode, in particular as a cathode. In the galvanic gilding of mass-produced goods, for example several contact elements, the mass-produced goods, for example the contact elements, are connected together as a second electrode, in particular as a cathode. When using barrel plating equipment, the bulk goods are typically in contact with each other and in contact with the contactor during gold plating, thus acting as a cathode.

The first electrode is typically an anode. The first electrode typically includes titanium and/or platinum.

[0022] In one embodiment, the electroplating system comprises further electroplating baths and further electrodes, for example for additional electrolytic coating with other metals. The plating equipment may include a diaphragm disposed within the plating bath and separating it into a cathode compartment and an anode compartment.

A connector as disclosed herein is used to disconnect and connect wires, preferably electrical wires. Connectors are typically designed in pairs to be complementary to one another, with a male connector being able to be connected to a complementary female connector, for example in a form-fitting and/or force-fitting manner. Connectors include a contact element. The contact element of a connector comes into conductive contact with the contact element of another connector, in particular a complementary connector, in order to produce the conductive connection. The contact element can be designed, for example, as a contact pin, which is preferably included in a male connector. The contact element can also be designed as a contact socket, which is preferably included in a female connector. The contact pin is complementary to the contact socket and can preferably be connected to it in a positive and/or non-positive manner. A connector can also include a housing, which can be designed differently or identically for male and female connectors. A connector may further include a cable gland for glanding an incoming cable. The incoming cable is conductively connected to the contact element.

[0024] Contact elements are typically electrically conductive. Electrically conductive means that the electrical conductivity at 20° C. is more than 10 2 S/m, in particular more than 10 4 S/m, preferably more than 10 6 S/m. A contact element preferably consists of copper or an alloy comprising copper.

Degreasing, as used in the present disclosure, refers to a treatment of a workpiece, for example a mass-produced item, in particular a contact element, by which lipophilic compounds, in particular oils and fats, are at least partially, preferably completely, removed from the surface of the workpiece. In the technical context of the present disclosure, lipophilic compounds include in particular deep-drawing greases, deep-drawing oils, anti-corrosion oils, fluxes, release agents, which often include silicones, drill grinding oils, vibratory grinding oils, oils for the temporary application of corrosion protection and oils for machining, for example for turning.

The degreasing contributes to a homogeneous galvanic surface coating. Without degreasing, oils and greases remaining on the surface of a workpiece could result in the surface areas covered with grease and oil not being electroplated as well or even not at all. Since lipophilic compounds are typically little or not at all dissolved by aqueous solutions, but electroplating baths often comprise aqueous solutions, the lipophilic compounds are typically not dissolved from the surface of the workpiece to be electroplated during electroplating.

[0027] Degreasing is typically performed using a surfactant. The surfactant is able to bind the lipophilic compounds and bring them into solution. Degreasing may include one or more of the following degreasing methods: electrolytic degreasing, boiling degreasing, alkaline degreasing, e.g. strong alkaline or weak alkaline degreasing. Electrolytic degreasing includes cathodic degreasing and/or anodic degreasing.

In electrolytic degreasing, an alkaline electrolytic solution is used, preferably an aqueous solution of NaOH or KOH. With cathodic degreasing, the contact element to be degreased is connected as a cathode and with anodic degreasing, the contact element to be degreased is connected as an anode. During cathodic or anodic degreasing, hydrogen or oxygen is produced at the contact element connected as a cathode or anode. Without wanting to be limited to a theory, it is a hypothesis that the hydrogen or oxygen formed literally mechanically blasts off the lipophilic compounds adhering to the surface.

Decoction degreasing comprises heating the contact element at at least 60°C, preferably 70°C - 90°C. An aqueous solution is preferably used for degreasing by boiling, it being possible for the aqueous solution to comprise sodium gluconate, for example. In some embodiments, the aqueous solution is basic.

The activation of the degreased contact element has the effect that any metal oxides on the surface of the contact element are at least partially, preferably completely, removed. Metal oxides are deposited on the surface of many metals over time, particularly through oxidation of the metal by atmospheric oxygen. Depending on the metal, a metal oxide layer can even form covering the entire surface. The deposition of metal oxides is called passivation.

The activation causes the subsequently formed galvanic coating to adhere better to the surface of the contact element. Activation also contributes to the formation of a homogeneous galvanic coating. The galvanic coating formed is in particular distributed evenly over the surface of the contact element.

The activation of the contact element includes a treatment of the degreased contact element with an activating solution. The activation solution preferably comprises an acidic aqueous solution with a pH below 5, preferably below 4.

[0033] The disclosed method for galvanically gold-plating a contact element can also include one or more rinsing steps. A rinsing step includes rinsing the contact element with a rinsing liquid. The rinsing liquid typically includes water, in particular demineralized water. A rinsing step can, for example, comprise a cascade rinsing, a circulating water rinsing or a standing rinsing. A cascade purge involves a two or three step purge in which the process flow is from contaminated to clean, but the post dosing of the purges is cascaded from clean to contaminated. A recirculating water rinse contains recirculated and treated water with low contamination levels. After treatment, treated water preferably has a conductivity of less than 20 microsiemens. A standing rinse takes place in a statically filled rinsing tub, the contamination of which accumulates over the course of use and which is discarded and prepared again at the end of the bath's service life.

In a preferred embodiment, the disclosed method for galvanic gold-plating of a contact element comprises at least one rinsing step before activation, before nickel-plating and before galvanic gold-plating. The effect of this is that the surface of the contact element is freed from foreign substances, which can originate, for example, from a previous treatment step, before activation, nickel plating and galvanic gold plating. Rinsing after activation causes, for example, the activation solution to be flushed off the surface of the contact element.

Galvanic gold plating refers to the galvanic coating of at least part of the surface, preferably the entire surface, of the nickel-plated contact element with a layer of gold. The gold layer comprises at least 90% by weight, preferably at least 95% by weight gold.

In some embodiments, the gilding bath has a gold content of 1 g/L - 12 g/L, preferably 2 g/L - 5 g/L. The gold content describes the mass of gold contained in the bath solution. Gold is typically present in the bath solution in the form of a cyanide complex, preferably [Au(CN)2]<->, for example in the form of K[Au(CN)2]. The ranges mentioned relate to the gold content of the gilding bath at the beginning of the galvanic gilding step, i.e. before voltage is applied or before the circuit is closed. Unless otherwise indicated, the same applies to all parameters relating to the composition of the gilding bath or any other galvanic bath.

The gold content mentioned enables an advantageous balance because on the one hand it is sufficiently low to enable a homogeneous layer thickness distribution, but at the same time it is not so low that the target layer thickness would not be achieved or the process would be limited, for example by a too long cycle time .

In a preferred embodiment, the density of the gilding bath is 0.9 g/cm 3 -1.5 g/cm 3 , in particular 1.1 g/cm 3 .

In some embodiments, the gilding bath includes a dissolved cobalt salt, such as cobalt hydroxide. The amount of cobalt salt, for example cobalt hydroxide, is preferably 20 g/L. The cobalt salt is preferably used in the form of a supplement or correction solution. The gilding bath preferably has a cobalt content of 0.3 g/l - 0.6 g/l, in particular 0.5 g/l. The cobalt content designates the maximum mass of elemental cobalt that can theoretically, i.e. with quantitative reduction and separation, be deposited. The ranges mentioned relate to the cobalt content of the gold-plating bath at the beginning of the galvanic gold-plating step, i.e. before voltage is applied or before the circuit is closed.

In some embodiments the pH of the gilding bath is 3.8 - 4.6, preferably 4 - 4.4, in particular 4.2. This pH value results in an optimal deposition rate and composition of the AuCo layer. The gilding bath can optionally comprise a buffer which buffers the pH in a range of 3.8 - 4.6, preferably 4 - 4.4, in particular 4.2.

In some embodiments, the galvanic gold plating is performed at 0.1 A/dm 2 -0.2 A/dm 2 . In some embodiments, the gold plating is performed for up to 2 hours. This duration is particularly suitable for large layer thicknesses. In further embodiments, the galvanic gold-plating is carried out for 4 minutes-8 minutes, in particular 6 minutes. This duration is particularly suitable for gilding by barrel galvanizing. In some embodiments, the galvanic nickel-plating is carried out for 0.5 h-3 h, preferably 1 h, at 0.1 A/dm 2 -0.7 A/dm 2 , preferably 0.2 A/dm 2 .

[0042] Nickel plating refers to the coating of at least part of the surface, preferably the entire surface, of the contact element with a layer of nickel. The nickel layer consists of at least 95% by weight nickel, preferably 100% by weight. In one embodiment, the nickel layer has a nickel layer thickness of 1 μm-10 μm, preferably 2 μm-6 μm. On the one hand, this layer thickness is relatively thin and thus leads to low material consumption and a low overall weight, and on the other hand it is sufficient to enable a homogeneous and full-area subsequent coating with a gold layer. The nickel layer also separates the contact element body from the gold coating and increases abrasion resistance. The nickel layer serves as a barrier layer. It prevents components of the material of the contact element base body, such as copper, from getting into the gold layer, for example through diffusion, since this would impair the properties of the gold coating. In addition, the nickel layer has a high degree of hardness, which is associated with advantageous wear-through behavior, for example in the case of contact elements. In particular, nickel coatings, which include nickel-phosphorus alloys, have a high level of hardness.

The application of a layer of gold on a layer of nickel results in high corrosion resistance and good conductivity. The surface formed is also typically bondable and suitable for multiple soldering processes.

[0044] Galvanic nickel-plating comprises the electroplating of the activated contact element in a galvanic nickel-plating bath. The contact element is typically connected as a cathode. Nickel granules or nickel ingots, for example, can serve as the anode. The nickel electroplating bath typically includes an aqueous solution of a nickel salt. Electroless nickel plating involves treating the activated contact element in an electroless nickel plating bath. The electroless nickel-plating bath includes a reducing agent in addition to a nickel salt. The electroless nickel plating bath is typically an aqueous solution. The reducing agent can include, for example, sodium hypophosphite.

In some embodiments, the electroless nickel-plating bath and/or the electroless nickel-plating bath comprises a dissolved nickel salt, preferably nickel sulfamate.

In some embodiments, the method for galvanic gold plating further comprises copper plating of the activated contact element, wherein the copper plating is carried out between step b) of activating the degreased contact element and step c) of nickel plating. In step c), the copper-plated contact element is thus nickel-plated in these embodiments. The copper plating is performed using a copper plating bath to form the copper plated contact member. The copper plating bath preferably comprises a solution of copper cyanide. The copper plating bath may further include potassium cyanide and/or NaOH. A copper anode, for example a copper bar anode or a copper plate anode, is preferably used as the anode in the copper plating. The copper plating bath preferably has a basic pH.

The additional copper plating step brings about an improved connection of the nickel layer to the substrate and serves as an adhesion promoter.

In some embodiments, the gilding bath includes one or more additives. The additive can include, for example, an acceleration additive, which can be an aqueous solution, for example. The acceleration additive is suitable for accelerating the galvanic gold plating, especially for accelerating the deposition process. In one embodiment, the accelerator additive comprises anions of mono and dicarboxylic acid. In a further embodiment, the acceleration additive comprises a thallium salt, in particular a thallium(I) salt, for example thallium(I) sulfate. The amount of accelerator additive added to the electrolyte, e.g /L, is. The acceleration additive can also include fluorides and/or borides.

In one embodiment, the acceleration additive is used in an amount of 10 g-500 g, in particular 30 g-100 g, per liter of gilding bath.

The accelerator additive accelerates the galvanic deposition. Without wishing to be limited to theory, this acceleration could be due to activation of hypophosphite ions.

In further embodiments, the additive comprises a base additive. The basic additive comprises basic components of the gold bath, preferably cyanide salts and/or disodium hydrogen phosphate.

In further embodiments, the additive comprises a gloss additive. The gloss additive increases the gloss of the galvanically generated gold layer. For example, the gloss additive may comprise thiolactic acid. In one embodiment, the pH when using the gloss additive is between 3 and 6.

[0053] In a second aspect, the general object is achieved by a gold-plated contact element which was produced using the disclosed method for galvanic gold-plating. The gold-plated contact element includes a contact element body, which makes up at least 95% of the volume of the gold-plated contact element. The gold-plated contact element also includes a nickel coating arranged on the surface of the contact element base body. The gold-plated contact element also comprises a gold coating with a gold layer thickness arranged on the surface of the nickel coating, the gold coating comprising at least 90% by weight, preferably at least 95% by weight, gold.

The nickel coating has a nickel layer thickness. In one embodiment, the nickel layer thickness is 1 μm-10 μm, preferably 3 μm-6 μm.

As will be understood by those skilled in the art, the exact composition of the nickel coating will depend on the nickel plating method used. The nickel coating can consist of pure nickel, for example, or can include a nickel alloy. Possible nickel alloys that can be included in the nickel layer are nickel-phosphorus alloys, nickel-palladium alloys and nickel-tungsten alloys. A nickel coating consisting of pure nickel can be formed, for example, using galvanic nickel plating methods. For example, a nickel-phosphorus alloy can be formed using electroless nickel plating methods. For example, the nickel-phosphorus alloy may have a high (10%-14%), medium (9%-12%) or low (3%-7%) phosphorus content.

A nickel coating is a coating that includes nickel. The nickel coating preferably comprises at least 80% by weight nickel. In some embodiments, the nickel coating comprises at least 90% by weight nickel, for example at least 95% by weight, in particular at least 98% by weight. In further embodiments, the nickel coating comprises a phosphorus content of less than 15%, for example less than 10%.

In some embodiments, the gold-plated contact element further comprises a copper coating with a copper layer thickness arranged on the surface of the contact element main body. In this embodiment, the nickel plating is placed on the surface of the copper plating. The copper coating is therefore located between the contact element base body and the nickel coating.

The copper layer thickness is preferably 0.001 μm-0.8 μm, in particular 0.02 μm-0.3 μm. In some embodiments, the copper coating comprises at least 95% by weight, preferably at least 98% by weight, in particular 100% by weight copper.

The contact element body corresponds to the contact element before this is gold-plated using the method disclosed herein. In one embodiment, the contact element base body is free of gold. Free from gold means that the contact element base body comprises less than 0.5% by weight, preferably less than 0.005% by weight, in particular 0% by weight, of gold.

In one embodiment, the contact element base makes up at least 95%, for example at least 98%, in particular at least 99% of the volume of the gold-plated contact element. In a further embodiment, the contact element base body has a contour which corresponds to a contour of the gold-plated contact element up to ±40 μm. The contour of a body describes the three-dimensional, external shape of the body.

In one embodiment, the contact element base body is conductive. In a preferred embodiment, the contact element base body has a conductivity of at least 0.1 MS/m, preferably at least 3 MS/m.

In some embodiments, the contact element main body has a volume of up to 20 cm 3 , in particular up to 10 cm 3 , and/or a weight of up to 300 g, in particular up to 20 g. In further embodiments, the contact element base body consists of copper or an alloy comprising copper or comprises an alloy containing copper.

In one embodiment, the gold coating comprises a maximum of 5% by weight, preferably 0.1% by weight - 3% by weight, of cobalt. In another embodiment, the gold coating consists of gold and cobalt. In a further embodiment, the gold layer thickness is 0.05 μm-0.5 μm, in particular 0.2 μm-0.3 μm.

In one embodiment, the gold-plated contact element is a gold-plated connector and the connector includes a connector body.

BRIEF EXPLANATION OF THE FIGURES

Embodiments of the invention are explained in more detail using the following figure and the associated description. FIG. 1 shows a flow chart of an embodiment of the disclosed method for gold electroplating.

DETAILED DESCRIPTION OF EMBODIMENTS

The present detailed description, in connection with the accompanying figure, presents embodiments of the invention and is intended to contribute to a better understanding of the invention. The designations used in the detailed description of the embodiments of the invention illustrated in the figure are not intended to limit the invention. The figure is drawn schematically.

FIG. 1 shows a flow chart of an embodiment of the disclosed method for electroplating with gold. In this embodiment, a plurality of, for example more than 50, contact elements for connectors are gold-plated using a barrel plating apparatus.

First, the barrel of a barrel plating apparatus is loaded with the contact elements. The contact elements are degreased in a subsequent chemical boiling degreasing process. Chemical degreasing by boiling includes treatment with alkaline cleaning agents with the addition of surfactants. After a subsequent rinsing step, the contact elements are electrolytically degreased. In this electrolytic degreasing process, the contact elements are first connected via the drum as a cathode and then as an anode in an electrolyte containing NaOH. This is followed by another rinsing step, followed by activation of the degreased contact elements. This activation involves immersion in an acidic solution, for example 3.5-6 vol% H2SO4, at room temperature for 1 minute. After activation, the contact elements are rinsed again.

The contact elements are then galvanically copper-plated. The galvanic copper plating is carried out for 5-10 minutes at 0.15 A/dm 2 using a copper plating bath containing copper cyanide. A copper layer is formed with a layer thickness of approximately 0.02 µm. The copper plating bath has the following composition: copper ions (40 g/L - 65 g/L), (replenished with copper cyanide), potassium cyanide (15 g/L - 50 g/L) and brighteners. Copper granules are used as the anode.

Subsequent rinsing is followed by activation by treatment with an acidic solution, for example H2SO4 (3.5% by volume-6% by volume).

After subsequent rinsing, the contact elements are galvanically nickel-plated. The galvanic nickel-plating is carried out for 1 h at 0.5 A using a nickel-plating bath containing nickel sulfamate, so that a nickel layer with a layer thickness of 2 µm is formed. A nickel sulfamate bath is used for galvanic nickel plating. This nickel plating bath contains the composition: boric acid: 30-70 g/l, chloride content: 2-8 g/l, nickel content: 65-95 g/l. The pH of the nickel plating bath is 2.4-3.5. The temperature of the nickel plating bath is adjusted to 57°C - 63°C. Nickel ingots are used as the anode.

Subsequent rinsing is followed by activation by treatment with an acidic solution. For example, H2SO4, 3.5% by volume - 6% by volume and/or a mixture of sodium hydrogen sulfate and sodium fluoride can be used as the acidic solution. After rinsing again, chemical nickel plating is then carried out. Hypophosphite (H2PO2<->) is typically used as the reducing agent. Nickel sulphate can be used as the electrolyte. The pH is adjusted so that it is not so low that the deposition is too slow, but also not so high that poorly soluble nickel hydroxide would precipitate. The chemical nickel plating leads to a growth of the nickel layer by a further 2 µm, so that the total nickel layer thickness is 4 µm.

The resulting nickel-plated contact elements are then rinsed before they are activated. Activating involves treatment with a solution containing sodium bicarbonate and sodium fluoride and is preferably carried out at about 27°C for 1 minute. After further rinsing, the nickel-plated, activated contact elements are galvanically gold-plated in a gold-plating bath. The gilding bath comprises the following components in the following quantities: Auruna 5400 batch concentrate 90.8 L Auruna accelerator 3 11.35 kg Auruna base additive C 17.5 kg potassium gold cyanide 1.34 g water 70 L

The components Auruna 5400 batch concentration, Auruna accelerator 3 and Auruna base additive C come from Umicore.

After mixing the components listed in the table, the pH of the gilding bath is adjusted to 4.2 and the gilding bath is then heated to 50.degree. The gold and cobalt concentration in the gilding bath is then determined and adjusted by adding potassium gold cyanide and/or a supplement or correction solution comprising 20 g/L cobalt hydroxide so that the gold concentration is 4 g/L and the cobalt concentration is 0.5 g/L amounts to. For example, the gold and cobalt concentration can be determined using absorption spectroscopy.

The galvanic gilding with the aid of the gilding bath is carried out for 8 minutes at 0.2 A/dm 2 , so that a gold layer with a gold layer thickness of 0.2 μm is formed. The gold layer consists of more than 97% by weight gold and less than 3% by weight cobalt. After rinsing the gold-plated contact elements, the barrel of the barrel plating apparatus is discharged.

Claims (9)

1. A method for galvanically gold-plating a contact element for connectors, comprising: a. degreasing the contact element; b. activating the degreased contact element; c. Nickel plating of the activated contact element using - galvanic nickel plating using a galvanic nickel plating bath and/or - chemical nickel plating using a chemical nickel plating bath; and i.e. galvanic gold-plating of the nickel-plated contact element using a gold-plating bath to form the gold-plated contact element, the gold-plating bath comprising gold ions in the form of a cyanide complex, preferably [Au(CN)2]<->, for example in the form of K[Au(CN)2]. . 2. Method according to claim 1, wherein the gilding bath has a gold content of 1 g/l - 1 2 g/l, preferably 2 g/l - 5 g/l. 3. The method according to claim 1 or 2, wherein the gilding bath comprises a dissolved cobalt salt, for example cobalt hydroxide, and has a cobalt content of 0.3 g/L - 0.6 g/L, preferably 0.5 g/L. 4. The method according to any one of the preceding claims, wherein the pH of the gilding bath is 3.8 - 4.6, preferably 4 - 4.4, in particular 4.2. 5. The method according to any one of the preceding claims, wherein the galvanic gold-plating is carried out at 0.1 A/dm 2 - 0.2 A/dm 2 . 6. The method according to any one of the preceding claims, wherein the step of galvanic gold plating is carried out by means of barrel plating. 7. Gold-plated contact element which has been produced using the method for galvanic gold-plating according to one of the preceding claims, the gold-plated contact element comprising: a. a contact element body, which makes up at least 95% of the volume of the gold-plated contact element, b. a nickel coating arranged on the surface of the contact element base body and c. a gold coating with a gold layer thickness arranged on a surface of the nickel coating, wherein the gold coating comprises at least 90% by weight, preferably at least 95% by weight, gold. 8. Gold-plated contact element according to claim 7, wherein the gold coating comprises a maximum of 5% by weight, preferably 0.1% by weight - 3% by weight, of cobalt. 9. Gilded contact element according to claim 7 or 8, wherein the gold layer thickness is 0.05 µm - 0.5 µm, in particular 0.2 µm - 0.3 µm.