The invention relates to an electrical contact coating for an electrically conductiv e substrate, preferably a substrate made of copper, a copper-based alloy or a copper-plated substrate, in particular for a high-temperature application in an electric or hybrid motor vehicle. Further, the invention relates to an electrical or electromechanical contact element for a high-temperature application, in particular for the high-voltage or automotive sector. Furthermore, the invention relates to an electrical, electronic and or electro-optical connector, in particular a plug-in connector or a connection means for high-temperature applications, in particular in the high-voltage and/or high-current sector. Furthermore, the invention relates to the use of copper or a layer comprising copper for a coating, in particular an electrical contact coating, preferably for high-temperature applications.

In electrical engineering and electronics, a large number of electrical socket and or pin connectors - referred to below as electrical (plug-in) connectors, mating (plug-in) connectors or (mating) connection means - are known which serve to transmit electric currents, voltages and or signals with a max imum possible range of currents, voltages, frequencies and or data rates. In particular in the automotive sector and in the high-voltage or high-current sector, such connectors have to guarantee, for a short time and/or permanently, perfectly satisfactory transmission of electric power, signals and/or data in warm, possibly hot, polluted, moist and/or chemically aggressive environments. Owing to the wide range of applications for such connectors, a large number of specially configured socket connectors and/or pin connectors are known. Such electrical connectors or their housings may be provided on an electric line, a cable, a cable harness or an electrical means, such as on/in a housing or on a printed circuit board of an electrical or electronic apparatus; in the latter case, usually the term "(mating) connection means" is used. If a connector is located on a line or a cable, usually the term "flying (plug-in) connector" or "plug" or "coupling" is used; if it is located on/in an electrical electronic means, usually the term "integrated plug" or "(integrated) bush" is used. Further, a mating connector is often also referred to as a plug receptacle, especially when the mating connector has a supporting collar which is intended to ensure a more robust connection between the plug- in connector and the mating connector, i.e. the plug receptacle. In the field of high-v oltage and high-current technology, in the field of the relevant connections, usually the terms "cable fittings" and "male cable connectors" are used.

Thus, connectors or couplings which supply batteries with electric current are required e.g. for an electric charging station and/or onward electrical power contacting in an electric or hybrid vehicle. Thus for example electrical connectors for supply units, such as a wall box in a garage, on a carport or a wall region, or charging points for electric and hybrid vehicles are required, by means of which the batteries of the motor vehicle can be topped- iip with electricity. For this, the electrical connector, which may possibly be mechanically stressed in the region of its contact elements, again has to be able to be connected permanently and securely, and at elevated temperatures has to ensure perfectly satisfactory transmission of the electric charging current and other electrical or electronic signals for controlling the charging operation of the battery or batteries. Transmission of data is further becoming increasingly important, with high demands in terms of data transmission being a crucial component of virtually every branch of industry, such as the computer industry or the automobile industry. Here, in addition to electrical connectors, w ide product ranges of electro-optical connectors are required which have to ensure high data transfer rates even at relatively high and high temperatures. Thus, for example, in a motor vehicle entertainment and infotainment information is exchanged electrically and possibly also via an optical bus. For these and also other electrical and/or optical data-transmission technologies, connectors or connection means are required which permanently and securely couple or connect the electrical and/or optoelectronic components together electrically and/or optically.

High endurance at elevated temperatures is also required for cable accessories for electrical voltages above 1 kV. Thus, in the case of cable connections or cable fittings which in particular are not SF ₆ -gas-insulated, care has to be taken that the electrical properties of the electrical contacting regions thereof do not change, or change only slightly, over time, w ith effective electrical connections which arc permanently secure over the years having to be set up between the connection means involved. Electric cable fittings for medium-voltage and high-voltage applications, such as for example shielded (right-angle) plugs and adapter (plug-in) connectors, have, within a fitting body, usually one electrical contact means formed as a threaded pin or a contact pin. which means is in electrical and mechanical contact with a conductor connection of a high-voltage cable.

For a good electrical transition between a connector and a mating connector which is complementary thereto, the connector and/or the mating connector often have coated contact elements. Such a contact coating is usually made from silver on the outside owing to its excellent electrical conductivity, and has a nickel layer underneath it. At relatively high or high temperatures, which may exceed 1 80 200°C, the contact coatings of such contact elements tend to delaminate after a certain time. This occurs owing to the diffusion of atmospheric oxygen through the silver layer to the nickel layer, w ith the nickel layer being oxidised, which leads to the delamination, i.e. detachment, of the silver layer from the nickel layer. This may be the case with current layer thicknesses for connectors of electric or hybrid motor vehicles e.g. at temperatures of approximately 1 80°C after only 200 hours. US 2009/0017327 Al discloses a ieadframe for electrically contacting an integrated circuit and an electromechanical contact element for point contacts made of copper. In order to av oid corrosion of the copper, the Ieadframe and the contact element in each case have an outer corrosion protection layer of tin, with a barrier layer of nickel being provided to prevent interdiffusion between the copper substrate and the tin layer. In order to prevent whiskering of the tin on the Ieadframe, a layer of silver is provided between the copper substrate and the layer of tin. In order to prevent fretting corrosion in the contact element, a sacrificial layer of copper, and on this an oxide layer, is provided on the nickel barrier layer, which oxide layer may consist of silver oxide. It is an object of the inv ention to devise an improv ed electrical contact coating, an improv ed electrical or electromechanical contact element and hence also an improved electrical, electronic and or electro-optical connector for high-temperature applications, in particular in the high-v oltage and/or high-current sector, inter alia for electric or hybrid motor vehicles. In so doing, deiamination of an electrical contact coating should be effectiv ely prev ented permanently ev en at high or relativ ely high temperatures of at least

150 to over 200°C. In so doing, the contact coating should be able to be provided on the contact element of the connector simply, rapidly and inexpensively. Further, it is an object of the invention to devise a use of copper or a layer comprising copper for a coating, in particular an electrical coating, for high-temperature applications.

The object of the invention is achieved by means of an electrical contact coating for an electrically conductive substrate in particular for a high-temperature application in an electric or hybrid motor vehicle, according to Claim 1 ; by means of an electrical or electromechanical contact element for a high-temperature application, according to Claim 7; by means of an electrical, electronic and/or electro-optical connector, in particular a plug-in connector or a connection means in the high-v oltage and/or high-current sector, according to Claim 9; and by the use of copper or a layer comprising copper for a coating, in particular an electrical contact coating, according to Claim 1 1. Advantageous developments, additional features and or adv antages of the invention will become apparent from the dependent claims and the following description.

The electrical contact coating according to the invention or the composite material according to the invention has a layered arrangement which can be applied to a substrate, which arrangement comprises at least two layers, the one layer being a transition metal and the other layer being a noble metal. Between the tw o layers of the layered arrangement there is provided a third layer, what is called an intermediate layer, which according to the inv ention comprises copper. In such case, one of the two layers is preferably an electrically contactable outer layer which is accessible to a contact element of a mating connector. - The electrical or electromechanical contact element according to the invention comprises an outer layer and an inner layer, the outer layer comprising a noble metal and the inner layer a transition metal. According to the invention, an intermediate layer is prov ided between the outer layer and the inner layer of this layered arrangement, which intermediate layer comprises copper.

The electrical, electronic and/or electro-optical connector according to the inv ention has an electrical contact coating according to the invention provided on a substrate of the connector and/or an electrical or electromechanical contact element according to the invention. The connector may in this case be designed as a socket connector, pin connector or hybrid connector e.g. for plug-in connections in the automotiv e sector, or as a cable fitting or a male cable connector for medium-voltage and/ or high-voltage cables or lines. Further, the connector may be designed as an electrical or electromechanical contact element as a pad, a tab or at least a section of a printed conductor of a printed circuit board. When using copper or a layer comprising copper according to the inv ention, it is used as a direct backing or a direct undeiiayer for a layer, in particular an outer layer, which comprises a noble metal or is a noble-metal layer.

According to the inv ention, the transition-metal layer is designed as a barrier layer, the noble-metal layer as an electrical contacting layer and. or the intermediate layer as an anti- diffusion layer. In such case, the transition-metal layer is an inner layer and the noble- metal layer an outer layer of the electrical contact coating. The transition metal preferably comprises nickel, but may howev er also comprise cobalt, iron, manganese, chromium and or molybdenum or an alloy thereof. The noble metal preferably comprises silver, but may how ever also comprise gold and/or a platinoid. That is to say that according to the invention the inner layer comprises in particular nickel or a nickel-based alloy, and the outer layer comprises in particular silver or a silver-based alloy.

According to the invention, the copper layer hinders the diffusion of atmospheric oxygen as far as the inner layer, which preferably comprises nickel, the intermetallic properties of the electrical contact coating being improved. This, according to the invention, effectively prev ents delamination of the contact coating permanently ev en at high or relativ ely high temperatures of at least 150 to 2()0°C. That also means that when the invention is used in a plug-in connector the extraction forces of the plug-in connector permanently remain substantially constant, since they are not increased by delamination of the contact coating. When a lubricant is used, this means that the plugging traction forces can be set permanently for a particular range. Further, the additional layer of the contact coating can be prov ided simply, rapidly and inexpensiv ely on the inner layer and in terms of time before the outer layer on a contact element of a connector.

According to the inv ention, the intermediate layer can lie directly on the outer layer and or directly on the inner layer of the contact coating, and is, optionally in each case, electrically connected thereto. Further, according to the inv ention the layered arrangement of the electrical contact coating may have a fourth layer which is arranged between the substrate and the inner layer. In such case, the fourth layer is designed in particular as a base layer or adhesion layer which preferably comprises copper or a copper-based alloy. That is to say, further, that the layered arrangement, apart from the base layer which is optionally present, preferably comprises exactly three layers. In such case, according to the inv ention a predominant proportion by weight or by volume of the outer layer is a noble metal. A predominant proportion by weight or by v olume of the inner layer in such case is a transition metal, in particular nickel, and a predominant proportion by weight or by v olume of the base layer and/or the intermediate layer is copper.

In preferred embodiments of the invention, the intermediate layer and/or the base layer is a copper flash or a copper strike. The substrate itself may in such case comprise copper or a copper-based alloy, or be a copper-plated substrate. However, also other materials, in particular electrically conductiv e materials, are suitable for the substrate. The substrate itself may in such case serve for contacting on its own, or ev en may be provided again on a backing, such as a component. According to the invention, the layered arrangement can be applied ov er the surface and/or selectively to the substrate. In particular, the layered arrangement can be provided on/in an electrical contacting region of the electrical contact element or the electrical connector. In such case, the substrate is at least a region of the contact element or of the connector. The inv ention will be explained in greater detail below using examples of embodiment with reference to the appended draw ings. The two highly abstract figures of the draw ings, which are not to scale, show:

Fig. 1 in a sectional side view, a first embodiment of an electrical contact coating according to the invention on an electrically conductiv e substrate of an electrical, electronic and or electro-optical connector; and

Fig. 2 in a view analogous to Fig. 1 a second embodiment of the invention, the substrate being provided with the electrical contact coating according to the invention on an electrical or electronic component. The invention will be explained in greater detail below, initially generally with reference to an electrical, electronic and/or electro-optical connector 1 , the drawing being kept correspondingly diagrammatic. The connector 1 may in such case be designed as a plug-in connector 1 or a connection means 1 preferably for a high-voltage high-current (plug-in) connection. In such case, the connector 1 may be designed as a socket connector 1 , pin connector 1 or hybrid connector 1 for plug-in connections in the automotive sector, in particular for electric or hybrid motor vehicles, in the electrical engineering sector and/or in the field of medium-v oltage or high-voltage cables, or for example as a pad 1 , a tab 1 or a section of a printed conductor 1 of a printed circuit board 50 (see Fig. 2) or as a leadframe 1 .

Such a connector 1 is designed e.g. as a socket connector 1 and. or pin connector 1 , as a (flying) coupling 1 , as an (integrated) plug 1 , as an (integrated) bush 1 , as a socket receptacle 1 and/or plug receptacle 1 , as a header 1, as an interface 1 , as a contact insert 1 , as a contact carrier 1 , as a cable fitting 1 , as a male cable connector 1 , as a base connector plug 1 , as a coupling connector/plug 1 , as a sleeve 1 , as a cable connection plug

1 . as a (shielded) (right-angle) plug 1 , as an adapter (plug-in) connector 1 . as a (cable) sealing end 1 , etc.

In this case, the connector 1 has an electrical or electromechanical contact element 2. The contact element 2 in such case serves for power contacting and. or signal contacting, the contact element 2 possibly being designed e.g.: as a ( h igh-cu rrent/h i gh- vol tage ) contact means 2, as a socket contact means 2, as a pin contact means 2, as a connection 2, as a connecting pin 2, as a pad 2, as a tab 2, as a printed conductor 2, as a grid 2, as a power contact 2, as a signal/data contact 2, as a threaded pin 2, as a contact pin 2, as a crimp contact 2, as a hermaphroditic connector 2, as a knife-blade contact 2, as a forked contact

2, as an insulation-displacement contact 2, as a spring contact 2, as a spring clamping means 2, as a plug- in receptacle 2, as a quick-connect receptacle 2, as an insertion tongue 2. as a plug- in pin 2, as a conductor 2, as a flat conductor 2, as electromagnetic shielding 2 etc.

At least in one electrical contacting region 5 of the contact element 2 or of the connector 1 , the contact element 2 has an electrical contact coating 10 according to the invention on a substrate 20, which in turn can be arranged on a backing 50 (see Fig. 2). The contacting region 5 can be electrically contacted on its outer electrical contact surface 132 by a contact element of a mating connector. In such case, the backing 50 may be an electrical or electronic component 50, a printed circuit board 50, a printed board 50 etc. It is of course possible to use the substrate 20 as the final support for the contact coating 10 (see Fig. 1). This is the case in particular with conventional socket contact means 2 and pin contact means 2. In this case, the substrate 20 itself may in turn hav e a layered structure.

The substrate 20 is preferably made from an electrically conductive material, such as for example copper, in particular OF/OFHC copper (OF: oxygen-free, OFHC: oxygen-free high conductive). Of course, another electrically conductive material, in particular a metal or a metal alloy, can also be used instead of copper; in such a case, preferably a base layer 100 is used. That is to say that in preferred embodiments of the invention a layer 100, preferably formed as an adhesion layer 100 or base layer 100, which comprises in particular copper or a copper-based alloy, is used as the lowermost layer 100 of the contact coating 10. In such case, a copper flash or a copper strike is preferred.

The layered arrangement 10 according to the invention of the electrical contact coating 10 has, apart from the base layer 100, preferably exactly three layers 1 1 0, 1 20, 130, namely an inner layer 1 10. an intermediate layer 120 and an outer layer 1 30. In this case, the inner layer 1 10 is designed as a barrier layer 1 10, an intermediate layer 1 1 0 or a transition-metal layer 1 10. The intermediate layer 120 is an underlayer, formed as an anti-diffusion layer 120 or as a barrier layer 120, for the outer layer 1 30 of the layered arrangement 10. Finally, the outer layer 1 30 is designed as an electrical contacting layer 1 30 or as a noble-metal layer 130. The inner layer 1 10 preferably comprises nickel or a nickel-based alloy, but may also comprise e.g. cobalt, iron, manganese, chromium, molybdenum or an alloy based thereon. The intermediate layer 1 20 comprises copper or a copper-based alloy, and is again designed in particular as a copper flash or a copper strike. The outer layer 130 preferably comprises metallic silver or a metallic silver-based alloy, but may also comprise e.g. metallic gold or a metallic platinoid. Further, the outer layer 130 may be a metallic pa lladiu m/n i c k e 1 go 1 d layer, in particular a palladium/nickel flash/gold coating.

In such case, a metal oxide layer, in particular a noble-metal oxide layer, is to be understood not to be a layer which contains the metal in question; such layer merely contains the metal oxide, which di ffers greatly in its properties. That is to say, for example, that silver ox ide is a distinct substance, as is silver too, hence silver oxide does not comprise any atomic silver. The invention is of course not limited to the above examples of connectors 1 or contact elements 2, but can be used anywhere where coatings, in particular contact coatings, tend to delaminate, which may be the case in particular at elevated temperatures, i.e. at temperatures of over 20 80°C. In such case, then instead of a conventional coating the coating according to the invention can be provided, or the copper layer according to the inv ention can be prov ided between a noble metal nickel layer sequence.

The base layer 100, the inner layer 1 1 0, the intermediate layer 1 20 and/or the outer layer 130 may for example be electrodeposited by means of electroplating. They may further be vapour-deposited, sputtered or provided by epitaxial growth. Preferred methods, in addition to electroplating, are chemical vapour deposition (CVD), physical vapour deposition (PVD), plasma-supported chemical vapour deposition (PECVD: plasma- enhanced chemical vapour deposition, PACVD: plasma-assisted chemical vapour deposition), metallic spray-coating (metal spraying), eiectroless deposition, such as dip- plating, or chemical deposition.

The layer thicknesses of the base layer 100, the inner layer 1 10, the intermediate layer 1 20 and/or the outer layer 1 30 may generally lie in a range from 0.01 μ m to over 200 μηι, depending on the field of application. In this case, it is preferable for the base layer 1 00 and the intermediate layer 120 to be designed as comparatively thin layers 100, 120, these preferably being able to be designed as a copper flash or a copper strike. Here then the layer thicknesses are preferably 0.05 -2 μ ηι, in particular 0.2 1 μηι. It is of course possible optionally to apply in particular the copper layer 1 20 designed as a barrier layer or anti- diffusion layer 120 by means of other methods, the layer thicknesses lying preferably in a range from 3 20 μηι, in particular 2-15 μιη, and preferably 1 1 0 um.

In applying the invention to an electromechanical contact element, such as for example a high-v oltage and/or high-current connector 1 for electric or hybrid v ehicles, the outer layer 130, which preferably consists predominantly of silver, has a layer thickness of 2 1 5 μηι, in particular 1 10 μηι, preferably of 0.5 5 μ m and particularly preferably of 0.8-2.5 μηι. In this case, the silver layer 130 may consist of bright pure silver or of hard silv er. When using gold as the outer layer 130, a layer thickness of 0.7-0.9 μηι ± 0.1 μηι is preferred. The inner layer 1 10, which is designed as a barrier layer 1 10, in such case preferably has a layer thickness of 0.02 5 μηι, in particular 0.05 2 μηι. Other layer thicknesses can of course be used, depending on the demands made on the relevant electrical contacting region(s) 5 of the electrical or electromechanical contact element(s) 2 of the connector 1 .