ELECTRICAL CONTACT ELEMENT

Abstract

An electrical contact element formed of sheet metal having a first region and a second region. Each one of the first and second regions is coated with a coating including a first layer containing a first material having a lower standard electrode potential than the sheet metal material. The coating includes a second layer in the first region which is absent in the second region. The second layer is arranged underneath the first layer and contains a second material that has a lower standard electrode potential than the first material.

Claims

1. An electrical contact element formed of sheet metal, comprising: a first region; and a second region, wherein each one of the first and second regions is coated with a first coating including a first layer containing a first material having a lower standard electrode potential than the sheet metal material, wherein the first coating includes a second layer in the first region which is absent in the second region and wherein the second layer is arranged underneath the first layer and contains a second material having a lower standard electrode potential than the first material.

2. The electrical contact element according to claim 1, wherein the first coating includes an additional third layer made of an alloy of a third material and the second layer is arranged between the first layer and the third layer.

3. The electrical contact element according to claim 2, wherein the alloy of the third layer is a copper zinc alloy containing zinc in an amount of 30% to 40% by weight.

4. The electrical contact element according to claim 1, further comprising a third region separated from the first region by the second region, wherein the third region is coated with a second coating comprising a first layer containing the first material, and a second layer arranged underneath the first layer and containing the second material, a third layer made of an alloy of the third material being absent in the third region.

5. The electrical contact element according to claim 4, wherein the second region defines a distance between the first region and the third region, the distance having a value between 1 mm and 8 mm.

6. The electrical contact element according to claim 1, further comprising a third region separated from the first region by the second region, wherein the third region is coated with a second coating comprising a first layer containing the first material, a second layer containing the second material and a third layer made of an alloy of the third material, wherein the second layer is arranged between the first and third layers.

7. The electrical contact element according to claim 6, wherein the second region defines a distance between the first region and the third region, the distance having a value between 1 mm and 8 mm.

8. The electrical contact element according to claim 1, wherein the first region forms at least a part of a fastening section of the electrical contact element for mechanically fastening the electrical contact element to a wire electrical cable and the second region forms at least a part of a connecting section of the electrical contact element for electrically connecting the electrical contact element to the wire electrical cable.

9. The electrical contact element according to claim 1, wherein the sheet metal is made of copper or an alloy thereof, the first layer is made of a material having a standard electrode potential ranking between a standard electrode potential of the sheet metal material and a standard electrode potential of the wire electrical cable material, and/or the first layer is made of tin.

10. The electrical contact element according to claim 1, wherein the second layer forms a galvanic anode and, in particular, is made of zinc.

11. The electrical contact element according to claim 1, wherein a hot dip tin layer is provided between the sheet metal and the first coating.

12. An electrical contact element formed of sheet metal, comprising: a first region; and a second region, wherein each one of the first and second regions is coated with a first coating including a first layer containing a first material having a lower standard electrode potential than the sheet metal material, wherein the first coating in the first and second regions includes a second layer which contains a second material having a lower standard electrode potential than the first material and which is arranged underneath the first layer and wherein the first coating further includes a third layer in the second region which is made of an alloy of a third material and arranged between the first and second layers.

13. The electrical contact element according to claim 12, wherein the third layer arranged between the first and second layers is also present in the first region.

14. The electrical contact element according to claim 13, further comprising a third region separated from the first region by the second region, wherein the third region is coated with a second coating comprising a first layer containing the first material, a second layer arranged between the sheet metal and the first layer and containing the second material, and optionally a third layer made of the alloy of the third material and arranged between the first and second layers.

15. An electrical contact element according to claim 14, wherein the second region defines a distance between the first region and the third region, the distance having a value between 1 mm and 8 mm.

16. The electrical contact element according to claim 12, wherein the first region forms at least a part of a fastening section of the electrical contact element for mechanically fastening the electrical contact element to a wire electrical cable and the second region forms at least a part of a connecting section of the electrical contact element for electrically connecting the electrical contact element to the wire electrical cable.

17. The electrical contact element according to claim 12, wherein the sheet metal is made of copper or a copper alloy, the first layer is made of a material having a standard electrode potential ranking between a standard electrode potential of the sheet metal material and a standard electrode potential of the wire electrical cable material, and/or the first layer is made of tin.

18. The electrical contact element according to claim 12, wherein the second layer forms a galvanic anode and, in particular, is made of zinc.

19. The electrical contact element according to claim 12, wherein the alloy of the third layer contains copper and zinc.

20. The electrical contact element according to claim 12, wherein the alloy of the third layer is a copper zinc alloy containing zinc in an amount of 30% to 40% by weight.

21. The electrical contact element according to claim 12, wherein a hot dip tin layer is provided between the sheet metal and the first coating.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0032] The present invention will now be described, by way of example with reference to the accompanying drawings, in which:

[0033] FIG. 1 is a schematic perspective view of an electrical contact element according to the invention;

[0034] FIG. 2 is a schematic perspective view of the electrical contact element of FIG. 1 connected to a wire electrical cable;

[0035] FIG. 3a is a schematic side view of the electrical contact element of FIG. 1;

[0036] FIG. 3b is a schematic partial cross-sectional view of a coating of an electrical contact element according to a first embodiment;

[0037] FIG. 3c is a schematic partial cross-sectional view of a coating of an electrical contact element according to a second embodiment;

[0038] FIG. 3d is a schematic partial cross-sectional view of a coating of an electrical contact element according to a third embodiment;

[0039] FIG. 4a is a schematic side view of the electrical contact element of FIG. 1;

[0040] FIG. 4b is a schematic partial cross-sectional view of a coating of an electrical contact element according to a fourth embodiment; and

[0041] FIG. 5 is a schematic partial cross-sectional view of a coating of an electrical contact element according to a fifth embodiment.

DETAILED DESCRIPTION OF THE INVENTION

[0042] FIG. 1 shows a non-limiting example of an electrical contact element 10 according to the invention. The electrical contact element 10 has a terminal portion 12 and a connection portion 14. The terminal portion 12 is for connecting the electrical contact element 10 to at least one mating electrical contact element (not shown), whereas the connection portion 14 comprises a fastening section 16 and a connecting section 18 and is for connecting the electrical contact element 10 to a wire electrical cable 20 (FIG. 2).

[0043] The wire electrical cable 20 comprises an insulation 22 surrounding a plurality of aluminum wires 24. Although shown as multiple stranded aluminum wires 24 in the present case, the wire electrical cable 20 could comprise only a single aluminum wires 24.

[0044] The fastening section 16 of the electrical contact element 10 has a pair of first crimp wings 26 and the connecting section 18 has a pair of second crimp wings 28. An electrical connection between the wire electrical cable 20 and the electrical contact element 10 is obtained by removing the insulation 22 from an end portion of the wire electrical cable 20, inserting the wire electrical cable 20 longitudinally in between the first and second crimp wings 26, 28, so that an insulated portion of the wire electrical cable 20 is located between the first crimp wings 26 and the bare aluminum wires 24 are located between the second crimp wings 28, and crimping the first and second crimp wings 26, 28 by means of a crimp tool (not shown), so that the first crimp wings 26 engage with the insulation 22 thereby mechanically securing the electrical contact element 10 to the wire electrical cable 20 and the second crimp wings 28 engage with the aluminum wires 24 thereby electrically contacting the aluminum wires 24.

[0045] It is to be understood that the number of fastening sections 16, connecting sections 18, first crimp wings 26 and/or second crimp wings 28 may depart from the number shown in the drawings. Furthermore, the terminal portion 12, the connection portion 14, the fastening section 16 including the first crimp wings 26, and/or the connecting section 18 including the second crimp wings 28 may have different sizes and shapes.

[0046] FIG. 3a shows a schematic side view of the electrical contact element 10. The connection portion 14 of the electrical contact element 10 comprises a first region 30 which includes the first crimp wings 26, a second region 32 which includes the second crimp wings 28, and a third region 34. The first region 30 and the third region 34 are separated by a distance D by the second region 32 in a longitudinal direction of the electrical contact element 10, and the third region 34 abuts the terminal portion 12 which defines a fourth region 36. The distance D may have a value between 1 mm and 8 mm, more preferably between 2 mm and 6 mm and most preferably between 2.5 mm and 4.5 mm.

[0047] In the present case, the first region 30 coincides with the fastening section 16 and the second region 32 coincides with the connecting section 18 as is illustrated by vertical dashed lines in FIGS. 3a to 3c and FIGS. 4a to 5. However, it is to be understood that the first region 30 may extend into a part of the connecting section 18 and/or that the second region 32 may extend into a part of the fastening section 16.

[0048] As shown in FIGS. 3b to 3d, 4b and 5, the electrical contact element 10 comprises a sheet metal 38 which is made of copper and which is provided with a thin layer 40 of hot dip tin. In addition, the connection portion 14 of the electrical contact element 10 is coated with a selective metal coating that will be described in more detail below.

[0049] According to a first embodiment illustrated in FIG. 3b, the coating in the first region 30 contains a first layer 42, a second layer 44 and a third layer 46, wherein the first layer 42 forms an outer layer and the second layer 44 is arranged underneath the first layer 42. More specifically, the second layer 44 is provided between the first layer 42 and the third layer 46, wherein the third layer 46 is arranged on top of the layer 40 of hot dip tin.

[0050] In the second region 32, the coating contains the first layer 42 and the third layer 46. Again, the first layer 42 forms an outer layer and the third layer 46 is arranged on top of the layer 40 of hot dip tin. In contrast to the coating in the first region 30, the second layer 44 is absent in the coating in the second region 32.

[0051] In the third region 34, the coating contains the first layer 42 and the second layer 44, whereas the third layer 46 absent. In other words, the first layer 42 forms an outer layer and the second layer 44 is arranged between and is in contact with the layer 40 of hot dip tin and the first layer 42.

[0052] FIG. 3c shows a coating of the connection portion 14 according to a second embodiment. This coating differs from the coating shown in FIG. 3b in that a layer structure in the third region 34 corresponds to the layer structure in the first region 30, i.e. the third region 34 comprises not only the first and second layers 42, 44 but also the third layer 46 wherein the first layer 42 forms an outer layer and the second layer 44 is arranged between the first layer 42 and the third layer 46.

[0053] In FIG. 3d a coating of the connection portion 14 according to a third embodiment is depicted. This coating differs from the coating shown in FIG. 3c in that the third layer 46 is absent in the first, second and third regions 30, 32, 34.

[0054] In either case, the terminal portion 12 of the electrical contact element 10 does not comprise any coating of the sort described above, i.e. the layer 40 of hot dip tin forms an outer layer in the fourth region 36.

[0055] In all embodiments shown in FIGS. 3b to 3d, 4b and 5, the first layer 42 is made of matte tin. The second layer 44 is made of zinc. The third layer 46 is made of an alloy of copper and zinc, with the copper zinc alloy preferably containing zinc in an amount of 30% to 40% by weight.

[0056] As can be seen in FIGS. 3b to 3d, the first region 30 and the third region 34 comprise a coating containing the second layer 44, whereas the second layer 44 is absent in the second region 32. Compared to the standard electrode potentials of copper contained in the sheet metal 38, tin contained in the first layer 42 and aluminum contained in the aluminum wires 24, zinc contained in the second layer 44 has the lowest standard electrode potential and, hence, will corrode more easily. More specifically, the zinc will be oxidized to an insulating material such as zinc oxide which will decrease conductivity. Since the second layer 44 is absent in the second region 32, such an insulating layer cannot form there, thus ensuring optimum electrical conductivity in the second region 32.

[0057] A method for manufacturing an electrical contact element 10 according to the first embodiment will now be described. Initially, a sheet metal 38 is covered by a layer 40 of hot dip tin by submerging the sheet metal 38 in molten tin. Alternatively, a commercially available hot dip tin coated sheet metal may be employed. Next, a first region 30 and a second region 32 will be coated with a third layer 46 containing a copper zinc alloy by immersing the first and second regions 30, 32 in an electroplating bath containing a copper zinc electrolyte.

[0058] After deposition of the third layer 46 in the first and second regions 30, 32, a second layer 44 is deposited onto the third layer 46 in the first region 30 by immersing the first region 30 in an electroplating bath containing a zinc electrolyte. Subsequent to depositing the second layer 44 in the first region 30, the electrical contact element 10 is rotated by at least approximately 180° and dipped into the electroplating bath containing the zinc electrolyte up to the second region 32, so that a third region 34 is immersed in the electroplating bath containing the zinc electrolyte, thus depositing the second layer 44 in the third region 34.

[0059] By again rotating the electrical contact element 10 by at least approximately 180° and immersing the first, second and third regions 30, 32, 34 in an electroplating bath containing a tin electrolyte, a first layer 42 is deposited in the first, second and third regions 30, 32, 34, thus creating an outer layer of matte tin on the electrical contact element 10, particularly, in the connection portion 14 of the electrical contact element 10.

[0060] An electrical contact element 10 according to the second embodiment is coated in a similar manner, except that the third layer 46 is deposited in all of the first, second and third regions 30, 32, 34 by immersing the first, second and third regions 30, 32, 34 in the electroplating bath containing the copper zinc electrolyte.

[0061] Alternatively, instead of depositing the second layer 44 separately in the first region 30 and the third region 34 as described above, the second layer 44 may be deposited simultaneously in the first and third regions 30, 34, i.e. in a single step, by masking the second region 32 with a removable masking material, such as an adhesive tape, prior to the deposition of the second layer 44. After deposition of the second layer 44 in all of the first, second and third regions 30, 32, 34 and removal of the masking material and the second layer 44 from the second region 32, the electrical contact element 10 can then be covered with the first layer 42 by immersing all of the first, second region and third regions 30, 32, 34 into the electroplating bath containing the tin electrolyte.

[0062] According to a further alternative method, the second layer 44 may be deposited simultaneously in the first, second and third regions 30, 32, 34. The removable masking material may then be used to protect the deposited second layer 44 in the first and second regions 30, 34 during removal of the second layer 44 in the second region 32, for example, by electro polishing, mechanical abrasion or laser ablation.

[0063] An electrical contact element 10 according to the third embodiment is manufactured in a similar manner as is described for the electrical contact element 10 according to the second embodiment, except that the step of providing the third layer 46 by immersing the first, second and third regions 30, 32, 34 in the electroplating bath containing the copper zinc electrolyte is omitted.

[0064] As in FIG. 3a, FIG. 4a shows a schematic side view of an electrical contact element. Again, the electrical contact element 10 has four regions 30, 32, 34, 36 as described above.

[0065] In FIG. 4b a schematic side view of an electrical contact element 10 according to a fourth embodiment is depicted. Here, the sheet metal 38 is coated with a first layer 42 containing tin and a second layer 44 containing zinc in all of the first, second and third regions 30, 32, 34, wherein the first layer 42 forms an outer layer and the second layer 44 is arranged on top of a layer 40 of hot dip tin covering the sheet metal 38. Additionally, in the second region 32, a third layer 46 made of an alloy of copper and zinc is arranged between the first layer 42 and the second layer 44, i.e. the third layer 46 is absent in the first and third regions 30, 32.

[0066] FIG. 5 illustrates a schematic side view of an electrical contact element 10 according to a fifth embodiment which differs from the fourth embodiment in that the third layer 46 is also arranged between the first and second layers 42, 44 in the first and third regions 30, 34. In other words, all of the first, second and third regions 30, 32, 34 are covered with the layer 40 of hot dip tin, on top of which the second layer 44 is arranged, which is coated by the third layer 46, which again is covered by the first layer 42 forming an outer layer.

[0067] Although shown as if the third region 34 is entirely covered by the second layer 44, the third region 34 may also be coated only partially with the second layer 44, depending on the depth of immersion in the electroplating bath containing the zinc electrolyte. By immersing the electrical contact element 10 in the electroplating bath containing the copper and zinc electrolytes to a greater depth, a third layer 46 will form, which not only covers the second layer 44 but also contacts the layer 40 of hot dip tin to a certain extent. The same also applies to the first layer 42.

[0068] The distance between the first and third regions 30, 34, the materials and the deposition methods described in the context of the first, second and third embodiments are also applicable to an electrical contact element 10 according to the fourth and fifth embodiments.

[0069] For all embodiments in which the first layer 42 is deposited onto the second layer 44, a thin layer of a primer material may be deposited onto the second layer 44 in the first and third regions 30, 34 prior to the deposition of the first layer 42, as the zinc of the second layer 44 may partially dissolve in the electroplating bath containing the tin electrolyte and thereby contaminate the electroplating bath containing the tin electrolyte. This will prevent zinc from getting dissolved in the electroplating bath containing the tin electrolyte. The primer material may be deposited by means of electroplating, for example, using a tin electrolyte different from the tin electrolyte used for the first layer 42.

[0070] Typically, the electrical contact element 10 is punched or cut from a metal blank. This punching or cutting process may generally be performed at any step of the above described methods. Preferably, though, the punching or cutting of the electrical contact element 10 is carried out prior to the deposition of the layers 40, 42, 44, 46 so that punching or cutting edges are also coated with the coating, which leads to a better protection against corrosion.

[0071] It should be understood that in FIGS. 3b to 3d, 4b and 5 the thicknesses of the layers 40, 42, 44, 46 are not to scale. In fact, the layers 40, 42, 44, 46 may have different thicknesses in each of the first, second, third and fourth regions 30, 32, 34, 36. Preferably, the thicknesses of each layer 40, 42, 44, 46 may range between 0.5 μm and 20 μm.

[0072] Furthermore, although the layer 40 of hot dip tin and the first, second and third layers 42, 44, 46 are depicted with constant layer thicknesses and sharp interfaces, it is to be understood that the layer thickness of a layer may gradually decrease in the longitudinal direction of the electrical contact element 10 at the end of the layer. Apart from that, atomic diffusion may occur at the interfaces of layers containing different materials.

[0073] For the sake of completeness, it is noted that even though FIGS. 3b to 3d, 4b and 5 show only a top surface of the sheet metal 38 coated with a coating comprising at least two of the first, second and third layers 42, 44, 46, it is to be understood that a bottom surface and/or edge surfaces of the sheet metal 38 may also be provided with such a coating.

[0074] While this invention has been described in terms of the preferred embodiments thereof, it is not intended to be so limited, but rather only to the extent set forth in the claims that follow. Moreover, the use of the terms first, second, primary secondary, etc. does not denote any order of importance, but rather the terms first, second, etc. are used to distinguish one element from another. Furthermore, the use of the terms a, an, etc. do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced items.