Contact pin for connecting electrical conductors made of copper and aluminum

A contact pin for connecting a first electrical conductor made of copper or a copper alloy and a second electrical conductor made of aluminum or an aluminum alloy comprises a plug-in section, a connecting section, and a coating disposed at least on the connecting section. The plug-in section is adapted to couple to the first electrical conductor. The connecting section is adapted to connect to the second electrical conductor. The coating is corrosion-resistant and compatible with aluminum and copper.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of the filing date under 35 U.S.C. § 119(a)-(d) of German Patent Application No. 102018203800.7, filed on Mar. 13, 2018.

FIELD OF THE INVENTION

The present invention relates to a contact pin and, more particularly, to a contact pin for connecting an electrical conductor made of copper or a copper alloy and an electrical conductor made of aluminum or an aluminum alloy.

BACKGROUND

A contact pin is used to connect current conductors, such as a circuit board and a busbar for car batteries. The contact pin can be produced from wires which can be affixed to the circuit board by soldering or have a spring with which the contact pin can be pressed into the circuit board.

Contact pins made of a copper alloy have an appropriate solidity, deformability, and electrical conductivity. It is desirable to use current conductors made of a cheaper material with a lighter weight, such as aluminum or an aluminum alloy. Copper, however, has a much higher electrochemical potential than aluminum and, consequently, contact corrosion occurs when the copper and aluminum come into contact if an electrolyte such as condensed water is present. There is a need for an inexpensive, viable, and corrosion resistant connection between a copper-based current conductor and an aluminum-based current conductor.

SUMMARY

A contact pin for connecting a first electrical conductor made of copper or a copper alloy and a second electrical conductor made of aluminum or an aluminum alloy comprises a plug-in section, a connecting section, and a coating disposed at least on the connecting section. The plug-in section is adapted to couple to the first electrical conductor. The connecting section is adapted to connect to the second electrical conductor. The coating is corrosion-resistant and compatible with aluminum and copper.

DETAILED DESCRIPTION OF THE EMBODIMENT(S)

Embodiments of the present invention will be described hereinafter in detail with reference to the attached drawings, wherein like reference numerals refer to the like elements. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein; rather, these embodiments are provided so that the disclosure will convey the concept of the invention to those skilled in the art.

A contact pin1according to an embodiment is shown inFIG. 1. The contact pin1extends along a longitudinal axis L and comprises a plug-in section2for coupling to a first electrical conductor made of copper or a copper alloy and a connecting section4for connecting to a second electrical conductor made of aluminum or an aluminum alloy. The connecting section4is disposed at a first free end5of the contact pin1and the plug-in section2is disposed at a second free end5′ of the contact pin1opposite the first free end5along the longitudinal axis L.

The plug-in section2, as shown inFIG. 1, is formed by a radially elastic resilient section6which enables elastic pressing into a receptacle of the first electrical conductor made of copper or a copper alloy. The resilient section6is broadened outwards substantially perpendicular to the longitudinal axis L and is elastically deformable inwards substantially perpendicular to the longitudinal axis L.

The connecting section4, as shown inFIG. 1, is configured to be peg-shaped and is adapted to couple to an aluminum-based electrical conductor. The connecting section4extends along the longitudinal axis L up to the plug-in section2and has a constant outer shape7along the longitudinal axis L.

The contact pin1is formed from copper and/or a copper alloy. The elastic resilient section6in particular is made of a copper alloy, in order to enable elastic deformability for the pressing-in into the first electrical conductor made of copper or a copper alloy. In an embodiment, the resilient section6has a different material composition than a material composition of the rest of the contact pin1.

As shown inFIG. 1, at least the connecting section4is coated with a coating8that is corrosion-resistant for aluminum and copper. The coating8prevents contact corrosion between the aluminum of the electrical conductor and the copper of the contact pin. Since the copper has a much higher electrochemical potential than aluminum, contact corrosion occurs when the two substances come into contact, if an electrolyte such as condensed water is present. The electrochemical potential of the coating8lies between the electrochemical potential of copper and of aluminum.

In an embodiment, the coating8is single-layered and consists of a tin-zinc alloy, with the percentage by weight of zinc being between approximately 5% and approximately 75%, and in an embodiment, is 20%. The coating8is galvanically deposited onto the connecting section4and is between approximately 0.5 and approximately 5 μm thick. In the embodiment shown inFIG. 1, the coating8that is corrosion-resistant for aluminum and copper is applied only on the connecting section4. In another embodiment, the contact pin1can be completely coated with the corrosion-resistant coating8. In an embodiment, the plug-in section2can be coated with a coating that is different from the coating8. The plug-in section2can be tin-coated, for example, in order to guarantee a corrosion-resistant connection to the copper-based electrical conductor.

As shown inFIG. 2, an arrangement10using the contact pin1further comprises a first electrical conductor14made of copper or a copper alloy and a second electrical conductor20made of aluminum or an aluminum alloy. In an embodiment, the first electrical conductor14is a circuit board and the second electrical conductor20is a busbar. In an embodiment, the second electrical conductor20is produced by deep-drawing, extrusion, or stamping.

The contact pin1, as shown inFIG. 2, is plugged with the plug-in section2into a receptacle12of the first electrical conductor14. The receptacle12penetrates the first electrical conductor14along the longitudinal axis L. A width of the resilient section6, in a non-plugged-in state, is larger than a width of the receptacle12. When pressed-in, the resilient section6is radially deformed inwards perpendicular to the longitudinal axis L, so that high driving forces arise between the resilient section6and the receptacle12. As a result, there arises a gas-tight zone and a low-impedance electrical connection between the contact pin1and the first electrical conductor14.

The peg-shaped connecting section4, as shown inFIG. 2, is introduced in a coupling section16, which has the form of a socket18, of the second electrical conductor20. The connecting section4and the coupling section16are configured to be complementary so that a good fit and a good hold can be achieved between the two. The connecting section4has a constant outer shape7along the longitudinal axis L, while the socket18has an aperture22which extends along the longitudinal axis and which has a constant inner width24along the longitudinal axis. In an embodiment, the connecting section4and the coupling section16each have a cross-section that is constant along a plug-in direction E. In an embodiment, an inner cross-section of the coupling section16and an outer shape of the connecting section4are rotationally symmetrical. As a result, the plugging-together of the contact pin1and the second electrical conductor20is facilitated.

By virtue of the coating8, a corrosion of the aluminum of the second electrical conductor20and of the copper of the contact pin1is prevented. As a result, a simple connection of the first electrical conductor14made of copper or a copper alloy and the second electrical conductor20made of aluminum or an aluminum alloy is possible with the contact pin1. The coating8is optimized for a connection to the aluminum and to the copper.

As shown inFIG. 2, the connecting section4is introduced in a plug-in direction E, which runs parallel to the longitudinal axis L, into the aperture22of the second electrical conductor20. This can be carried out by the application of force so that the contact pin1and the second electrical conductor20are pressed together. In order to further strengthen the cohesion, the coupling section16can be welded, soldered and/or crimped to the connecting section4.

In various embodiments, the second electrical conductor20can connect to a current conductor, such as a busbar or an accumulator, for example. Depending on the application, the length of the second electrical conductor20can be adapted. The second electrical conductor20can, for example, have a closed pin-shaped free end which faces away from the coupling section16and which can be connected to the current conductor by pressing, soldering, or by some other method. Furthermore, the second electrical conductor20can be outwardly insulated by an electrically non-conductive casing in order to avoid short-circuiting.

As shown inFIG. 2, the second electrical conductor20has at its outer surface26a clamping zone28which is formed by an indentation30. Through an action of mechanical force onto this clamping zone28, the contact pin1and the second electrical20are squeezed together.

The electrical conductors14,20, as shown inFIG. 2, are spaced apart from one another in plug-in direction E. In order to avoid contact between the electrical conductors14,20, the arrangement10has a polymer-containing sealing body31between the two electrical conductors14,20. The sealing body31can be formed by capillary casting. The sealing body31prevents dirt and condensed water from ending up between the electrical conductors14,20. In an embodiment, the sealing body31is a sealing ring or a potting between the electrical conductors14,20and is made of an insulating polymer.

In another embodiment of an arrangement10shown inFIG. 3, the connecting section4of the contact pin1has at least one shoulder32that protrudes laterally relative to the longitudinal axis L. As a result, when the second electrical conductor20and the contact pin1are squeezed together, at least one undercut34is formed in order to strengthen the connection between the contact pin1and the second electrical conductor20in a form-fitting manner.

In the unsqueezed state36, shown inFIG. 3, the socket18has an aperture22with an unvarying inner width24. The outer shape7of the connecting section4has, at its side facing away from the first electrical conductor14, the shoulder32which protrudes laterally perpendicular to the longitudinal axis L and which can have a blade-shaped surface structure in order to support an ingress into the socket18. The breadth of the shoulder32is designed to be complementary to the aperture22so that the connecting section4can be easily introduced into the socket18. During the squeezing-together, the aperture22narrows until the inner surface of the aperture22lies against the outer shape7of the connecting section4. A friction-locking connection arises and a form-fitting connection arises due to the shoulder32located in the formed undercut34. The squeezed state38is shown with a solid line inFIG. 3and the unsqueezed state36is depicted with a dashed line.

In an arrangement10according to another embodiment, as shown inFIG. 4, the contact pin1has a second radially elastic resilient section40which forms the connecting section4. The coating8is applied in three layers42,44,46. The first layer42consists of nickel and is applied on the outer surface of the connecting section4. The second layer44consists of zinc and the third layer46consists of tin.

The nickel from the first layer42connects to the copper of the contact pin1and serves as a diffusion-blocking layer. The first layer42prevents an interdiffusion between the copper atoms and the atoms of the coating8or aluminum of the second electrical conductor20. The formation of intermetallic Cu—Al compounds with high electrical resistances is inhibited by the diffusion-blocking layer. The tin from the third layer46contacts the aluminum of the second electrical conductor20. As a result, there occurs at least a partial interdiffusion between the atoms of the two materials, and the connection between the second electrical conductor20and the contact pin1is strengthened.

The second resilient section40is plugged into the aperture22of the second electrical conductor20, as shown inFIG. 4. Due to the press-connection between the contact pin1and the second electrical conductor20, a clamping zone28, as shown inFIG. 2, is not required. The second electrical conductor20therefore has a constant breadth.

An arrangement10according to another embodiment is shown inFIG. 5. The first free end5of the connecting section4is substantially bent back by 180° and forms an aperture22between the free end5of the connecting section4and an end of the connecting section4adjacent the plug-in section2. The connecting section4is deformed in a hook-shaped manner in a non-clamped state48. A peg-shaped coupling section16of the second electrical conductor20can be plugged through into the aperture22so that the coupling section16is arranged substantially parallel to the first electrical conductor14. In order to strengthen the connection between the connecting section4and the coupling section16, the free end5, in a clamped state50, is bent inwards to that end of the connecting section4which is adjacent the plug-in section2. In the clamped state50, the aluminum-based second electrical conductor20is connected to the contact pin1in a friction-locking manner. The embodiment ofFIG. 5makes it possible to contact a current conductor parallel to the plane of the first electrical conductor14and is advantageous when there is limited space.

An arrangement10according to another embodiment is shown inFIG. 6. The contact pin1, as shown in the embodiment ofFIG. 4, has a first radially elastic resilient section6for elastically pressing into the receptacle12of the first electrical conductor14and a second radially elastic resilient section40for elastically pressing into an aperture22of the second electrical conductor20. The electrical conductors14,20are configured here as flat conductors or busbars. The receptacle12penetrates the copper-based first electrical conductor14along the longitudinal axis L of the contact pin1. The contact pin1is plugged into the receptacle12against the plug-in direction E by its plug-in section2. The second radially elastic resilient section40forms the connecting section4and is plugged into the aperture22which penetrates the second electrical conductor20along the plug-in direction E.

The connecting section4, as shown inFIG. 6, has a three-layered coating8. The first layer42consists of nickel and is applied directly onto the connecting section4. The second layer44consists of zinc and the third layer46consists of tin. The third layer46of the contact pin1points outwards and thus contacts the aluminum of the second electrical conductor20.

A width of the resilient sections40,6, in the non-plugged-in state, is larger than a width of the aperture22or receptacle12. When plugged into the aperture22or receptacle12, the resilient sections40,6deform radially inwards perpendicular to the longitudinal axis L, so that high driving forces come into being between the resilient sections6,40and the receptacle12or aperture22. This leads to a gas-tight zone and a low-impedance electrical connection between the contact pin1and the electrical conductors14,20.

In an embodiment, the coating8can be up to 5 μm thick, and the individual layers42,44,46can have different thickness. In another embodiment, the individual layers42,44,46can have a same thickness. As a result, the coating8, depending on the use, can be optimized for the connection between the first electrical conductor14and the second electrical conductor20. With the coating8, contact corrosion can be prevented from occurring between the copper of the contact pin1and the aluminum of the second electrical conductor aluminum alloy20. With the arrangement10shown inFIG. 6, it is possible to create a simple connection between two flat conductors or busbars, with one flat conductor consisting of copper or a copper alloy and the other flat conductor consisting of aluminum or an aluminum alloy.