Surface treatment method of electric contact element and contact element

Abstract

The invention relates to a method for surface treatment of an electrically conductive contact element (100, 200) of an electrical connector (300, 400) by means of plasma, wherein a lubricant (106, 206) is applied to at least a partial area of ​​a contact surface (102, 202). In addition, the invention relates to an electrically conductive contact element (100, 200), the surface of which is treated by this method. The surface treatment method of an electrically conductive contact element (100, 200) for an electrical connector (300, 400) relates to an electrically conductive contact element (100, 200), which has a metal contact surface (102, 202), and a lubricant (106, 206) is applied to the contact surface of the electrically conductive contact element (100, 200) at least in a partial area of ​​the contact surface. Furthermore, the contact surface (102, 202) of the electrically conductive contact element (100, 200) is modified by plasma treatment, whereby a coating (120) of a solid lubricant is at least partially produced on at least a partial area of ​​the contact surface (102, 202) of the electrically conductive contact element (100, 200).

Description

Technical Field

[0001] The present invention relates to a method for surface treatment of a conductive contact element for an electrical connector. In addition, the present invention relates to a conductive contact element, the surface of which is treated by such a method. Background Art

[0002] Electrical connectors and their contact elements are known in many designs. Electrical connectors are intended to mate with suitable mating connectors to establish an electrical connection. Electrical connectors are often used for signal transmission or power transmission. To this end, electrical connectors often have conductive contact elements that come into contact with contact elements of the mating connector when the connectors are mated. Usually, the contact elements of one connector element are designed as contact pins, while the contact elements of the mating connector are designed as contact springs. When the connector and the mating connector are mated, the contact springs exert an elastic spring force on the contact pins to ensure a reliable conductive connection.

[0003] Electrical connectors are used in motor vehicles, for example, to transmit power and network electrical and electronic systems. In motor vehicles, connectors are exposed to strong temperature fluctuations, vibrations, moisture and corrosive media. The increase in operating temperature leads to increased wear, especially in the case of the widely used tin-plated copper-based contact elements.

[0004] In particular, base metal contact surfaces, such as those with tin, nickel or their alloys, have a tendency to fretting corrosion ("fretting" or "galvanizing") in the event of small relative movements. Furthermore, in the case of high-polarity connectors, the mating forces are often outside the required forces, especially during initial mating, and in the case of noble contact surfaces, such as those based on noble metals, there is a known problem of a tendency to cold welding.

[0005] Therefore, in addition to high wear resistance, low mating and pulling forces are also required to facilitate assembly and maintenance of the connector. To increase occupational safety, the specified mating force must not exceed a certain limit, especially during initial mating.

[0006] In addition, during the mating process of the connector with the mating connector, local abrasion occurs on the contact surface of the contact element. This wear caused by abrasion limits the mating frequency of the connectors, thereby reducing their working time.

[0007] German patent specification DE102016214693B4 describes an electrical contact element of a connector, in which a cavity filled with an auxiliary material is arranged below the contact surface. The contact surface is textured beforehand by laser irradiation. After the connector has been mated into a mating connector for the first time, the cavity breaks open, causing the auxiliary material to escape and covering the contact surface with a lubricating film. When the connector is mated again, this lubricating film causes the mating force to be reduced. The treatment of a surface with an interference pattern from laser radiation, in which a recessed structure is produced exemplarily, is referred to as a textured surface hereinafter.

[0008] However, the assembly boundary conditions also define criteria for the mating force when the connector is first mated with a mating connector. This initial mating force is particularly important when assembling connectors with a large number of contacts. Since the connectors can also be further processed in warm areas, there are additional requirements for heat resistance on the contact surfaces of the connectors. Applying a lubricating film to the contact surfaces of the connector is therefore not a suitable solution, as the lubricating film would evaporate at warm temperatures. Summary of the invention

[0009] Therefore, there is a need for a cost-effective and reliable method of treating the contact surface of an electrical connector in such a way that the initial mating force can be reduced when mated with a mating connector and the surface treatment does not lose its effect even under adverse environmental conditions.

[0010] This object is achieved by the subject matter of the independent claims. Advantageous embodiments of the invention are the subject matter of the dependent claims.

[0011] In this case, the invention is based on the idea of ​​achieving improved surface properties of the contact surface of an electrical connector by treating it with plasma. To this end, a lubricant is first applied to the contact surface, thereby generating a solid lubricant coating on the contact surface by plasma treatment.

[0012] In particular, the present invention includes a surface treatment method for an electrically conductive contact element of an electrical connector, wherein the electrically conductive contact element has a metal contact surface. In addition, a lubricant is applied to at least a partial area of ​​the contact surface of the electrically conductive contact element. In addition, the contact surface of the electrically conductive contact element is changed by plasma treatment, thereby at least partially producing a solid lubricant coating on at least a partial area of ​​the contact surface of the electrically conductive contact element.

[0013] The solid lubricant coating can be, for example, carbon, carbon-containing or sulfide-based. A carbon layer is understood to be a thin layer consisting primarily of the chemical element carbon. This includes, for example, a graphite layer or a diamond-like carbon layer. The applied lubricant layer used as the initial lubricant layer can be, for example, an oil, a grease, a paste or another solid lubricant, such as graphite, carbon nanotubes, MoS2 or a mixture thereof, which is modified by a plasma treatment.

[0014] Surface treatment can reduce the roughness of the contact surface of the electrical connector and obtain higher uniformity. In addition, the hardness of the contact surface can be increased, for example by selectively generating an intermetallic phase IMP or a nanocrystalline microstructure. Each of these improved properties (independent of other properties) reduces the initial mating force when the connector is mated with a mating connector. In addition, the variation of the coefficient of friction over the entire contact surface can be reduced.

[0015] According to an advantageous further development of the invention, the contact surface of the electrically conductive contact element has a surface texture consisting of elevations and depressions, so that a lubricant applied to the contact surface adheres particularly well.

[0016] The plasma is ignited in a pressure range of 1 mbar to 8 bar, which means that, advantageously, the plasma treatment does not require a vacuum chamber, but can be performed using an atmospheric pressure plasma. This has the advantage that liquid chemicals can be completely omitted. For this purpose, harmless gases such as nitrogen or compressed air can be used for plasma generation. Alternatively, the plasma can be ignited in a low vacuum or a slight overpressure.

[0017] In the following, plasma is understood to be a partially or completely ionized gas. Cold or hot plasma is generated and diffused by a plasma nozzle directed toward the material. Inside the nozzle, the plasma is generated by a high voltage between the stator and the rotor. By means of a high-voltage discharge similar to an arc, the ionized gas is directed onto the surface to be treated. For example, hydrogen, argon, nitrogen or compressed air can be used as the gas to be ionized.

[0018] Advantageously, the power of the plasma is in the range of 50 W to 5 kW in order to produce the aforementioned solid lubricant coating from the applied lubricant layer.

[0019] According to an advantageous further development of the invention, cavities filled with auxiliary material are enclosed below the contact surface of the electrically conductive contact element. During the first mating of the connector with the mating connector, these filled cavities break open, allowing the auxiliary material to escape and exert its effect. This allows the mating forces to be reduced during the first mating process and even more so for all subsequent mating processes.

[0020] Auxiliary materials, also called additives, are substances that are added in relatively small amounts to achieve or improve certain properties.

[0021] A cavity is considered to be an artificially formed cavity below the surface. The arrangement of the cavity below the contact surface means that the cavity has no outlet at the contact surface, or at most an outlet of such narrow dimensions that the auxiliary material filled into the cavity cannot be reached without causing a breakthrough from the contact surface into the cavity.

[0022] According to another advantageous embodiment of the invention, the auxiliary material is selected from an antioxidant, a corrosion inhibitor, a lubricant, another solid lubricant and an acid. This group of substances, after leaking to the contact surface of the connector, facilitates the mating of the connector with a mating connector.

[0023] According to an advantageous further development of the invention, the plasma treatment of the electrically conductive contact element is part of a continuous process. This has the advantage that the edges of the contact surface are also treated uniformly. As a result, a uniform thin layer of solid lubricant can advantageously be obtained, as a result of which the contact surface has a high degree of uniformity.

[0024] According to an advantageous further development of the invention, the plasma treatment comprises irradiation with a plasma flame, wherein the residence time of the conductive contact element in the plasma flame is between 5 ms and 500 ms. After this short residence time, the above-mentioned positive effects already occur, whereby a large number of pieces can be processed in a short time.

[0025] According to an advantageous further development of the invention, the plasma flame leaves the plasma nozzle at a distance of 5 mm to 100 mm from the contact surface to the plasma nozzle. Such targeted plasma treatment allows easy integration into existing manufacturing equipment and complies with safety regulations without the need for additional shielding precautions.

[0026] According to an advantageous further development of the invention, the solid lubricant coating produced by the plasma treatment has a thickness of 1 nm to 300 nm. Such a thin coating allows the plasma treatment to be used for a variety of connector types, which can be mated with matching mating connectors without having to adjust the dimensions.

[0027] According to an advantageous further development of the invention, the lubricant is applied to the contact surface of the electrically conductive contact element with a thickness of between 0.1 μm and 5 μm. Thinly applied layers adhere particularly well to rough metallic contact surfaces.

[0028] The invention also relates to a related electrically conductive contact element for an electrical connector, which has a metal contact surface. In addition, the contact surface has at least partially a solid lubricant coating made from a lubricant layer by plasma treatment. Such an electrically conductive contact element has the advantage of having a lower first mating force than conventional contact elements from the outset. In addition, the standard deviation of the friction coefficient is reduced, which is particularly important for connectors with a large number of contacts.

[0029] It is also advantageous that the cavities filled with auxiliary material are enclosed below the contact surface of the electrically conductive contact element. When the contact element makes contact with the mating contact for the first time, these break apart, the auxiliary material escapes, and the mating force is reduced during the first mating process and even more so for all subsequent mating processes. Since the filled cavities are located below the contact surface, negative effects such as gluing can be avoided. Furthermore, undesirable losses of auxiliary material due to solid embedding are excluded.

[0030] According to another advantageous embodiment of the electrically conductive contact element, the auxiliary material is selected from the group consisting of an antioxidant, a corrosion inhibitor, a lubricant, another solid lubricant and an acid. These substances reduce wear caused by abrasion, which increases the mating frequency of the connector.

[0031] According to another advantageous embodiment of the conductive contact element, the metal contact surface comprises tin, and / or nickel, and / or silver, and / or copper and / or an alloy of tin, nickel, silver, and copper. These materials are rust-proof and heat-resistant, thereby ensuring the life of the connector.

[0032] According to an advantageous further development of the invention, the square roughness of the surface in the mating direction is less than 0.3 μm. This value is lower than the measured value of the surface which has not been modified by the plasma treatment according to the invention. Thus, advantageously, a lower roughness can be achieved, resulting in a more uniform surface, thereby improving the mating of the connector with the mating connector.

[0033] Surface roughness is the degree of unevenness of a solid surface, which is lower than its shape or waviness, but higher than the irregularities of the lattice structure. Roughness affects material properties, such as friction. One of the roughness characteristics is square roughness. This can be detected by optical measurement methods. The measurement evaluation is based on the DIN EN ISO4287 and DIN EN ISO 11562 series of standards. In order to mate a connector with a mating connector, the roughness in the mating direction is particularly important. Therefore, in the present case, the measurement is aligned with the mating direction. In one embodiment, this alignment can be performed along the surface texture. If the surface texture has protrusions and depressions, as in the above embodiment, the alignment of the measurement is performed along the protrusions and depressions. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] For a better understanding of the invention, the invention will be explained in more detail with reference to the examples of embodiments shown in the following drawings. In this document, identical components have the same reference numerals and the same component names. In addition, some features or combinations of features from the different embodiments shown and described may also represent independent, creative solutions or solutions according to the invention. In the drawings:

[0035] Figure 1is a schematic cross-sectional view of a contact surface in a first embodiment in a process step of a method according to the present invention, including an enlarged cross section of the contact surface;

[0036] Figure 2 is a schematic cross-sectional view of a contact surface in another embodiment of a process step of the method according to the present invention;

[0037] Figure 3 is a schematic diagram of a first embodiment of surface treatment of a contact surface by plasma in a further process step;

[0038] Figure 4 is a schematic cross-sectional view of the contact surface of a first embodiment of the contact surface after plasma treatment in a further process step. DETAILED DESCRIPTION

[0039] Figure 1 The first process step of the method according to the invention is shown in a sectional view through a first exemplary embodiment of a contact surface of an electrically conductive contact element.

[0040] The method is used to surface treat a conductive contact element 100. The contact element 100 for the electrical connector 300 is conductive and includes a base material 104. The base material 104 may include, for example, tin, nickel, silver, copper, or an alloy of tin, nickel, silver, copper, and / or other elements. A metal contact surface 102 is formed on one side of the contact element 100. When the connector 300 is mated with a mating connector, the contact surface 102 contacts a contact surface of the mating connector (not shown).

[0041] At least a portion of the contact surface 102 is coated with a lubricant 106. For example, the lubricant 106 may include oil, grease, paste, acid or another solid lubricant, such as graphite, carbon nanotubes, MoS2 or a mixture thereof. The thickness of the applied lubricant may have a value between 0.1 μm and 5 μm.

[0042] In an advantageous embodiment, the contact surface 102 of the contact element 100 can have a surface texture 112 of protrusions 124 and depressions 122. These protrusions 124 and depressions 122 can be formed at least partially in a periodic alternation. In this regard, the depressions 122 form grooves, and the protrusions 124 form walls between them. For example, the protrusions can be in the order of 0.1 μm to 2 μm. However, it is by no means necessary for the method according to the present invention that the surface texture 112 includes protrusions 124 and depressions 122. It should be understood that the contact surface 102 can have any surface texture 112, such as smooth or with other roughness.

[0043] Figure 2A further embodiment of a contact surface 102 of an electrically conductive contact element 200 is shown in a first process step of the method according to the invention.

[0044] The contact element 200 for the electrical connector 400 is conductive and includes a base material 204. The base material 204 may include, for example, tin, nickel, silver, copper, or an alloy of tin, nickel, silver, copper, and / or other elements. One side of the contact element 200 forms a metal contact surface 202, and when the connector 400 is mated with a mating connector, the contact surface 202 contacts the contact surface of the mating connector.

[0045] In the illustrated embodiment, the cavities 208 are enclosed below the contact surface 202 and are filled with auxiliary material 210. In the illustrated embodiment, the cavities 208 are spaced apart from each other at regular intervals below the contact surface 202. In this embodiment, the surface texture 212 has exemplary protrusions 224 and depressions 222. These protrusions 224 and depressions 222 can be formed alternately and periodically at least in part. In this regard, the depressions 222 form grooves and the protrusions 224 form walls between them. For example, the protrusions can be on the order of 0.1 μm to 2 μm.

[0046] It should be understood that the cavities 208 may also be irregularly spaced apart from each other and located at different depths below the contact surface 202. In addition, if the contact surface 202 does not have the protrusions 224 and the depressions 222, the cavities 208 may also be enclosed below the contact surface 202. For the method according to the present invention, the surface texture 212 does not have to include the protrusions 224 and the depressions 222. It should be understood that the contact surface 202 may have any surface texture 212, such as smooth or having other roughness.

[0047] The auxiliary material 210 enclosed in the cavity 208 may include, for example, oil, grease, paste or another solid lubricant, such as graphite, carbon nanotubes, MoS2 or a mixture thereof. The contact surface 202 is coated with a lubricant 206 on at least a portion of its area. For example, the lubricant 206 may include oil, grease, paste, acid or another solid lubricant, such as graphite, carbon nanotubes, MoS2 or a mixture thereof. The thickness of the applied lubricant may have a value between 0.1 μm and 5 μm.

[0048] Figure 3 The contact element 100 according to the first exemplary embodiment is shown in a further process step of the method according to the invention.

[0049] The figure shows a schematic diagram of surface treatment of a contact element 100 using plasma. In a possible embodiment, a plasma generator 118 for controlling and monitoring a plasma system is schematically shown, wherein a plasma nozzle 114 is directed toward the material to be treated. The directional plasma nozzle 114 is used to generate and propagate plasma. Various nozzle systems such as a single nozzle or a rotating nozzle can be used as a plasma source. From the plasma nozzle 114, a plasma flame 116 is used to treat a contact surface 102. The distance d from the plasma nozzle 114 to the contact surface 102 is in the range of 5 mm to 100 mm.

[0050] In the process, the plasma flame 116 can be generated in a pressure range of 1 mbar to 8 bar, so that, for example, the surface treatment can also be carried out at atmospheric pressure. The power of the plasma flame 116 is in the range of 50 W to 5 kW. In this case, the treatment of the contact surface 102 is part of a continuous process, wherein the contact element 100 passes through the plasma flame 116 at a speed of, for example, 100 mm / s or 200 mm / s. The residence time of the contact surface 102 under the plasma flame 116 is then between 5 ms and 500 ms.

[0051] However, it is clear that the values ​​given are given only as examples and are intended to aid understanding, but in no way limit the invention to these values. The passing speed, distance and residence time can all be adjusted as required and can accommodate different power values ​​of the plasma flame.

[0052] Figure 4 An exemplary first embodiment of a contact surface 102 of an electrically conductive contact element 100 after surface treatment with plasma is shown. The plasma treatment has produced a coating 120 of a solid lubricant, preferably carbon, on at least partial areas of the contact surface 102. The solid lubricant coating 120 can have a thickness of 1 nm to 300 nm and can be transparent. Thus, at least partially applied lubricant from a previous process step has been at least partially converted into a solid lubricant coating, preferably consisting of carbon.

[0053] In a second embodiment (not shown), if, as in the aforementioned second embodiment in the previous process step, a cavity filled with auxiliary material is enclosed below the contact surface 102, it is also possible to produce a solid lubricant coating 120 on the contact surface 202. By the plasma treatment, the cavity remains unchanged.

[0054] Advantageously, in addition to the preferred carbon or carbon-containing coating, the surface properties of the contact element can be improved by a plasma treatment. Thus, the treatment reduces the inhomogeneities of the contact surface, thereby achieving a lower square roughness.

[0055] Experimental studies have shown that the square roughness of the surface treated with plasma is less than 0.3 μm. This value is 0.1 μm lower than the square roughness value of the surface not treated by the process according to the invention.

[0056] Advantageously, a higher hardness of the coated surface can additionally be achieved. The hardness of the connector surface can be determined by nano characterization. An indenter with known geometry is pressed into the surface to be tested, forming a defined force curve. When a specified maximum force is reached, the indenter is released again in a controlled manner. The indentation depth is recorded both during loading and unloading. Various parameters can be calculated from the applied force, the shape of the indenter and the indentation depth. In order to measure the surface hardness, at least two measuring points are approached at a predetermined distance. The average value of all measuring points on the surface can be used as a comparable measure of the surface hardness. A measurement is first carried out on the untreated surface and then a second measurement is carried out after the plasma treatment. In an exemplary measurement with 51 measuring points at a distance of 100 μm, 450 N / mm could be determined for the untreated surface. 2 However, for textured and plasma treated surfaces, 750 N / mm 2 An exemplary average value of .

[0057] Therefore, the surfaces exhibited a higher hardness after the plasma treatment. When comparing the average values, it can be observed that the hardness increased by 40% to 80% compared to the untreated surfaces, especially for the contact surfaces textured before the plasma treatment.

[0058] Finally, spatially resolved characterization of plasma treated surfaces in terms of roughness, hardness and chemical composition can advantageously reveal a significantly more homogeneous image than, for example, stamped or plated contacts.

[0059] These advantageous properties occur independently of one another and independently of one another lead to smaller variations in the coefficient of friction. Within a surface, a narrower distribution of the standard deviation of the coefficient of friction can therefore be demonstrated by the method according to the invention.

[0060] It should be noted that it is possible to obtain the same advantageous properties using different plasma generation methods. For example, a plasma flame can be generated in a low-pressure plasma chamber under vacuum.

[0061] Reference numerals list

[0062] 100, 200 contact elements

[0063] 102, 202 contact surface

[0064] 104, 204 base material

[0065] 106, 206 lubricant

[0066] 208 Cavity

[0067] 210 Supplementary Materials

[0068] 112, 212 surface texture

[0069] 114 Plasma Nozzle

[0070] 116 Plasma Flame

[0071] 118 Plasma Generator

[0072] 120 solid lubricant coating

[0073] 122, 222 depression

[0074] 124, 224 bulge

[0075] d Distance from plasma nozzle to contact surface

[0076] 300, 400 connectors

Claims

1. A method for surface treatment of a conductive contact element (100, 200) of an electrical connector (300, 400), in, The conductive contact element (100, 200) comprises a metal contact surface (102, 202), wherein a lubricant (106, 206) is applied to at least a partial area of ​​a contact surface (102, 202) of an electrically conductive contact element (100, 200), and wherein a contact surface (102, 202) of an electrically conductive contact element (100, 200) is modified by plasma treatment, thereby producing a solid lubricant coating (120) at least partially on at least a partial area of ​​the contact surface (102, 202) of the electrically conductive contact element (100, 200), Wherein, the power of the plasma is in the range of 50W to 5kW, wherein the plasma treatment comprises irradiation with a plasma flame (116), and wherein the residence time of the electrically conductive contact element (100, 200) in the plasma flame (116) is between 5 ms and 500 ms.

2. The method according to claim 1, in, The contact surface (102, 202) of the conductive contact element (100, 200) has a surface texture of protrusions (124, 224) and depressions (122, 222).

3. The method according to any one of the preceding claims, in, The plasma is ignited in a pressure range from 1 mbar to 8 bar.

4. The method according to claim 1 or 2, in, A cavity (208) filled with an auxiliary material (210) is enclosed below a contact surface (102, 202) of the electrically conductive contact element (100, 200).

5. The method according to claim 4, in, The auxiliary material (210) is selected from an antioxidant, a corrosion inhibitor, a lubricant, another solid lubricant, and an acid.

6. The method according to claim 1 or 2, in, The plasma treatment of the electrically conductive contact element (100, 200) is part of a continuous process.

7. The method according to claim 1, in, The plasma flame (116) exits from the plasma nozzle (114), and Wherein, the distance from the contact surface to the plasma nozzle (114) is 5 mm to 100 mm.

8. The method according to claim 1 or 2, in, The coating layer (120) of the solid lubricant produced by the plasma treatment has a thickness of 1 nm to 300 nm.

9. The method according to claim 1 or 2, in, The lubricant (106, 206) applied to the contact surface (102, 202) of the conductive contact element (100, 200) has a thickness between 0.1 μm and 5 μm.

10. An electrically conductive contact element (100, 200) for an electrical connector (300, 400) manufactured by the method of any one of claims 1 to 9, It has a metal contact surface (102, 202), in, The contact surface (102, 202) at least partially has a solid lubricant coating (120) produced from the lubricant layer (106, 206) by treatment with plasma.

11. The electrically conductive contact element (100, 200) according to claim 10, in, A cavity (208) filled with a secondary material (210) is enclosed below the contact surface (102, 202).

12. The electrically conductive contact element (100, 200) according to claim 11, in, The auxiliary material (210) is selected from an antioxidant, a corrosion inhibitor, a lubricant, another solid lubricant, and an acid.

13. The electrically conductive contact element (100, 200) according to any one of claims 10 to 12, in, The metal contact surface (102, 202) comprises tin, and / or nickel, and / or silver, and / or copper, and / or an alloy of tin, nickel, silver and copper.

14. The electrically conductive contact element (100, 200) according to any one of claims 10 to 12, in, The square roughness of the surface in the mating direction is less than 0.3 μm.

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