Patent Publication Number: US-10777912-B2

Title: Electrical contact element and method for altering mechanical and/or electrical properties of at least one area of such

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of PCT International Application No. PCT/EP2016/062889, filed on Jun. 7, 2016, which claims priority under 35 U.S.C. § 119 to German Patent Application No. 102015210460.5, filed on Jun. 8, 2015. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to an electrical contact and, more particularly, to an electrical contact having an area with different mechanical and/or electrical properties. 
     BACKGROUND 
     For known electrical contacts such as contact pins, female connectors, crimp connectors, or cable shoes, it is frequently necessary for particular areas of the contact to have properties different from those of the contact material from which the contact is manufactured. For example, it can be necessary for a contact surface of the contact, which makes a connection to a further contact, to have increased conductivity, improved resistance to corrosion, or a greater mechanical hardness in order to improve an electrical connection to another contact. It is also frequently necessary to increase the durability or lifespan of the contact for frequent connections. 
     Expensive and complex methods are generally used in order to produce such areas of the contact. For example, at least one further material is deposited onto the contact material by electroplating or chemical vapor deposition. Such methods lead to desired results but are generally costly and require several working steps, high expenditure on material, and generally have a low degree of selectivity. 
     SUMMARY 
     An electrical contact according to the invention comprises an electrically conductive contact material and a plurality of particles adhered to an area of the contact material. At least some of the particles have a portion penetrating into the contact material. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described by way of example with reference to the accompanying figures, of which: 
         FIG. 1  is a plan view of a contact according to the invention; 
         FIG. 2  is a sectional view through a contact surface of the contact having a single-layer particle coating; 
         FIG. 3  is a sectional view through the contact surface having a partial multilayer particle coating; 
         FIG. 4  is a sectional view through the contact surface of  FIG. 2  having a coating formed from the single-layer particle coating; 
         FIG. 5  is a sectional view through the contact surface of  FIG. 3  having a coating formed from the partial multilayer particle coating; 
         FIG. 6  is a sectional view through a crimp section of the contact having a particle coating; and 
         FIG. 7  is a sectional view through the crimp section of  FIG. 7  having a coating formed from the particle coating. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Exemplary embodiments of the present invention will be described hereinafter in detail with reference to the attached drawings, wherein like reference numerals refer to 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 present disclosure will be thorough and complete and will fully convey the concept of the disclosure to those skilled in the art. 
     An electrical contact  1  according to an embodiment is shown in  FIG. 1 . The contact  1  is made from an electrically conductive contact material  3  and has at least one contact surface  5  for connection to another contact. In an embodiment, the electrical contact  1  is formed by stamping and bending from the contact material  3 . In other embodiments, the electrical contact  1  is formed as a solid part. 
     As shown in  FIG. 1 , the contact  1  has a crimp section  7  with a pair of crimp flanks  9 . The crimp section  7  has a surface structure  11  which can improve the electrical and mechanical connection to an electrical conductor which is retained in the crimp section  7 ;  FIG. 1  shows the contact  1  with folded back crimp flanks  9  without an electrical conductor being retained in the crimp section  7 . In the shown embodiment, the surface structure  11  has a plurality of grooves  13  impressed in the contact material, the grooves  13  are longitudinal recesses in the contact material  3 . In other embodiments, the surface structure can have other forms, such as ribs, knobs, or folding edges, and other areas of the contact  1  can have surface structures  11 . 
     In the shown embodiment, the electrical contact  1  has two areas  15  in which particles  17  are deposited on the contact material  3 . A material of the particles  17  can be selected for the desired application; to improve the electrical and/or mechanical properties of an area  15 , the particles  17  may be gold, silver, tin, brass, bronze, zinc, or alloys of such metals. In order to increase only the mechanical friction in the area  15  of the contact material  3 , for example, particles  17  of non-conductive materials may also be used. 
     In an embodiment, the particles  17  are deposited on the contact material  3  by gas dynamic cold spraying. In an embodiment, the particles  17  are deposited at supersonic speed in a particle beam, for example, at speeds of more than 400 meters per second. In other embodiments, the particles  17  have a speed between 500 and 1000 meters per second. The speed dictates how deep the particles  17  in the area  15  penetrate into the contact material  3  and how well they adhere thereto. At higher speed, the particles  17  can penetrate more deeply into the contact material  3  but are themselves also more strongly deformed by the forces which arise when they impact on the contact  1 . The speed can be selected depending on the desired field of use, the selected material and the desired form of a coating formed by the particles  17 . 
     Solid or dry particles  17  can be used, as a result of which it is possible to dispense with wet-chemical methods of deposition. It is likewise possible to dispense with firstly placing materials which are intended to be deposited onto the contact material  3  into a liquid or gaseous aggregate state. 
     In order to achieve a high spatial resolution when depositing particles  17  onto the contact material  3 , a mask can be used which allows a particle beam to only reach sections which are not covered by the mask. The mask is then located between a particle source, for example a nozzle of a gas dynamic cold spraying device and the contact  1 . 
     If required for certain properties, the contact  1  can also be additionally coated, for example galvanically, through printing techniques or through chemical vapor deposition. 
     A first area  15  having particles  17  overlaps the contact surface  5  and a second area  15  having particles  17  overlaps the crimp section  7 . Exemplary configurations of the first area  15  which overlaps the contact surface  5  are described in greater detail below with reference to  FIGS. 2-5 . Configurations of the second area  15  which overlaps the crimp section  7  are described in greater detail below with reference to  FIGS. 6-7 . 
     A first area  15  with particles  17  overlapping the contact surface  5  is shown in  FIG. 2 . The particles  17  are arranged in an adherent manner on a surface  19  of the contact material  3 . The depicted arrangement and shape of the particles  17  is merely exemplary; in principle, any form which allows the particles  17  to be deposited sufficiently quickly onto the contact material  3  is possible. For example, the particles  17  can be spherical, drop-shaped, or can take the form of non-uniform fragments. If it is crystal-forming material, a particle  17  can also have a cubic or other angularly shaped form. In an embodiment, the particles  17  have diameters between 1 and 50 □m. 
     At least some of the particles  17  have a portion penetrating into the contact material  3 , as shown in  FIGS. 2 and 3 , and are mechanically anchored therein as a result of the particles  17  hitting the contact  1  at a high speed. At these locations, the contact material  3  is displaced at least partially by the particles  17 . It can likewise be possible that undulations or elevations in the surface  19  are formed by particles  17  bouncing off of the contact material  3 ; for example, crater-like structures can be formed in the surface  19 . The partial deformation of the contact material  3  can serve to improve the adhesion of the particles  17  to the surface  19  by surface-fusing. In addition, a reshaping of the surface  19  can increase a surface roughness. 
     Some of the particles  17  form particle conglomerates  21 , as shown in  FIG. 2 , at which several particles  17  adhere to one another. The particles  17  of the conglomerates  21  can partially penetrate into one another. Particles  17  can also form a network-like structure on the surface  19  in the area  15 . Between some of the individual particles  17  and particle conglomerates  21 , there can also be free locations  23  through which the contact material  3  is accessible from the outside. As a result of this structure, the contact  1  can have a high degree of roughness in the area  15 . Such a structure can arise, for example, if only a thin or simple layer of particles  17  is intended to be formed. In this case, particles are deposited onto the contact material  3  either at lower speed or with a smaller particle density, which means that the contact material  3  is not entirely coated. 
     As shown in  FIG. 3 , in an embodiment, the particles  17  in the area  15  may be arranged at least partially in multilayers on the contact material  3 . In this case, adjacent particles  17  penetrate at least partially into one another. As a result, not only is the layer of particles  17  which are directly connected to the contact material  3  securely retained, but so too are successive layers of particles  17 . 
       FIG. 4  shows an area  15  as shown in  FIG. 2  but following heating of the area  15 , for example, selectively by electron beams. Alternatively, other energy-rich types of radiation such as, for example, lasers, X-rays or matter jets made from parts other than electrons, can also be used. The particles  17  are fused into one layer  25  by heating. The layer  25  can be continuous and uniformly cover the surface  19  in the area  15 . However, if sufficient particles  17  were not available to fully cover the surface  19  or if a layer of particles  17  had many free locations  23 , the layer  25  can also be formed such that it is not uniform. 
     The layer  25  shown in  FIG. 4  substantially consists of the material of the particles  17 . In other words, no formation of an alloy made up of the material of the particles  17  and the contact material  3  takes place. This can, for example, be achieved through rapid heating by electron beams in which the particles  17  and/or the contact material  3  are generally not heated higher than their melting temperatures. Alternatively, the contact  1  is heated at least in sections such that the material of the particles  17  is mixed with the contact material  3  and alloys form. This can be made to depend on the planned application. As a result of a melting of the particles  17 , the thickness  27  of the layer  25  is generally smaller than a particle diameter  29  shown in  FIG. 2   
     Recesses or undulations in the surface  19  which possibly arise due to the impact of particles  17  can remain in existence so that the material of the fused particles  17  fills them. If, as a result, the layer  25  penetrates partially into recesses in the surface  19 , the layer  25  adheres better to the contact material  3 . As an alternative to the depicted layer formation, particles  17  can also be only partially surface-fused by heating, so that these connect to one another more strongly or the surface of the particles  17  and/or of particle conglomerates  21  is smoothed. 
       FIG. 5  shows an area  15  as shown in  FIG. 3  but with several tiers of particles  17  following heat treatment. As in the embodiment described with reference to  FIG. 4 , a layer  25  consisting of the material of the particles  17  is also formed here. Since an at least partially multilayer arrangement of particles  17  was previously present, as shown in  FIG. 3 , the layer thickness  27  is larger than in the example described with reference to  FIG. 4 . The layer thickness  27  can therefore be adjusted following heating by the number of particles  17 . 
     It is also possible here that the material of the particles  17  or layer  25  in  FIG. 5  fills recesses or undulations generated previously by the impact of particles  17 , such that the material of the layer  25  penetrates at least partially into the contact material  3  and is anchored in the contact material  3  as a result. Likewise, here too only a partial fusing of some particles  17  can be generated instead of a continuous layer  25 . This can be achieved, for example, in that the particles  17  are heated at a lower intensity or for a shorter irradiation period. 
     A second area  15  with particles  17  overlapping the surface structure  11  of the crimp section  7  is shown in  FIG. 6 . The area  15  with the particles  17  can be formed analogously to the embodiment described with reference to  FIGS. 2 and 3 . The particles  17  are deposited on the surface  19  and some of the particles  17  penetrate at least partially into the contact material  3 . Merely by way of example,  FIG. 6  shows a non-continuous coating with particles  17 . 
     The surface structure  11 , as formed by the grooves  13 , provides both stability and conductivity for a connection of the crimp section  7  with an electrical conductor. In the case of the depicted longitudinal grooves  13 , an electrical conductor such as a wire, for example, can be arranged perpendicular to a longitudinal direction of the grooves  13 . When the crimp flanks  9  are closed, the electrical conductor is pressed at least partially into the grooves  13  and the areas  31  protruding from the surface  19  are pressed into the material of the conductor. As a result, an electrical conductor is retained securely in the crimp section  7 . At the same time, the protruding areas  31 , which can in particular have the form of edges, penetrate any oxide layers which may be present on the conductor and improve the electrical connection to the conductor. The particles  17  present on the surface  19 , as shown in  FIG. 6 , penetrate into an inlaid or pressed-in conductor and improve both the mechanical adhesion and the electrical conductivity from the contact material  3  to the electrical conductor. 
       FIG. 7  shows the surface structure  11  from  FIG. 6  after the particles  17  have been heated. As already described with reference to  FIGS. 4 and 5 , heating by irradiation with electron beams, for example, can fuse the particles  17  so that a layer  25  is formed. The layer  25  is arranged on the surface structure  11  and covers the whole surface  19  including the grooves  13 . As in the previously described examples, here too it can be possible to only heat the particles  17  to the extent that these are fused with one another or surface-fused and substantially retain their particle shape.