Patent Publication Number: US-9837741-B2

Title: Electrical contact element with a finely structured contact surface

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of the filing date under 35 U.S.C. §119(a)-(d) of German Patent Application No. 102015209855.9, filed May 28, 2015. 
     FIELD OF THE INVENTION 
     The invention relates to an electrical contact element, and more particularly, to a contact surface of an electrical contact element. 
     BACKGROUND 
     Electrical contacts formed of conductive materials and used to establish a direct electrical connection to another conductive element are known in the art. Known electrical contacts, for example, are used in the contact section of a plug contact, cable shoe, ferrule, crimp section, or other known forms of electrical connectors to connect to a known conductive element such as a cable, wire, bundle of strands, plug element, or bushing. 
     The characteristics of the contact surface of the electrical contact are particularly important to the reliability of the electrical connection to the other conductive element. Particularly good electrical conductivity is required at the contact surface. Furthermore, since the contact surface is additionally frequently used to enter into a frictionally engaged, force-fitting, and/or materially engaged connection to the other conductive element, the mechanical characteristics of the contact surface are also important to the electrical connection. 
     SUMMARY 
     An object of the invention, among others, is to provide an electrical contact element with improved electrical conductivity and improved mechanical characteristics. The contact element of the invention is also able to be manufactured in large quantities in a cost-efficient manner. The disclosed electrical contact element includes a contact surface of an electrically conductive contact body having a plurality of coated regions with a first coating and a plurality of uncoated regions without the first coating, the coated regions and uncoated regions arranged in an alternating manner in a variation direction along the contact surface. 
    
    
     
       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 top view of a contact element according to the invention; 
         FIG. 2  is an enlarged view of a contact surface of the contact element shown in  FIG. 1 ; 
         FIG. 3A  is sectional view taken along line A-A of the contact surface of  FIG. 2 ; 
         FIG. 3B  is a sectional view of other embodiments of coated regions of the contact surface shown in  FIG. 3A ; 
         FIG. 4  is a top view of a second embodiment of a contact surface; 
         FIG. 5  is a top view of a third embodiment of a contact surface; 
         FIG. 6  is a top view of a fourth embodiment of a contact surface; and 
         FIG. 7  is a top view of a fifth embodiment of a contact surface. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENT(S) 
     The invention is explained in greater detail below with reference to embodiments of an electrical contact element. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete and still fully convey the scope of the invention to those skilled in the art. 
     A contact element  3  according to the invention is shown generally in  FIG. 1 . In the shown exemplary embodiment, the contact element  3  is a stamped bending part  1 . One with ordinary skill in the art, however, would understand that the solution according to the invention can be employed for a wide range of contact elements  3 , including those forming a crimp connection, plug contact, cable shoe, ferrule, or other electrical connectors known in the art. 
     The contact element  3  includes a contact body  5  and a contact surface  7 . Contact body  5  is formed of an electrically conductive material, and may be a sheet metal. 
     Contact surface  7  can have any suitable form. In the shown embodiment, contact surface  7  forms a bending crimp section, but could also form a crimp clip, crimp wing, or other known electrical contact section. Contact surface  7  includes at least one recess  10 , at least one coated region  13 , and at least one uncoated region  17 . 
     The at least one recess  10 , as shown in  FIG. 2 , may be configured as an elongated furrow  9 . The furrow  9  may be impressed, stamped, chased or deep-drawn into contact body  5 . A longitudinal direction  11  of the furrow  9  runs perpendicular to a longitudinal direction of the contact element  3 . Three furrows  9  are shown in the embodiment of  FIGS. 1-7 , but one with ordinary skill in the art would understand that the number of furrows  9  could vary. As shown in  FIG. 3A , furrows  9  form surface offsets  25  between, in each case, a base surface  21  of the furrow  9  and a top surface  23  of the contact surface  7 . Surface offsets  25  represent flanks or shoulders of the furrows  9  in cross-section. 
     In other embodiments, contact surface  7  can have recesses  10  formed differently than the shown furrows  9 . Instead of a furrow  9 , the recess  10  can also have the form of a groove or a corrugation. Alternatively, the recess  10  can also have a large-area rectangular form. Furthermore, the furrows  9  may not be continuous. Likewise, alternatively or additionally, contact surface  7  can have elevations instead of recesses. 
     The at least one coated region  13 , shown in  FIGS. 2 and 3A , has a first coating  15 . The first coating  15  can be selected, for example, such that it has increased electrical conductivity compared to the contact body  5 . The first coating  15  may also be harder than the contact body  5 . The first coating  15  may be formed from tin, zinc, silver, bismuth, or other materials known to those with ordinary skill in the art. 
     First coating  15  is directly deposited on contact body  5  without any intervening layers. The coated regions  13  may be formed by methods in which the first coating  15  is selectively directly deposited on the contact surface  7  and then hardened, surface-fused and/or sintered using energy-rich radiation. The first coating  15  can alternatively be deposited in the desired form and dimensions onto the contact surface  7 , for example, by printing methods. The first coating  15  can be fixed and connected to the contact surface  7  by the energy-rich radiation which may be electron radiation, ion radiation or laser radiation. 
     Each coated region  13  has a surface  16 . As shown in  FIG. 2 , each coated region  13  may be formed as a stripe  27 , with a longitudinal direction of the stripe  27  running parallel to the longitudinal direction  11  of the furrows  9 . Each stripe  27  has edge regions  31  and a width  33 . In the shown embodiment, the stripe width  33  measured perpendicular to the longitudinal direction of the stripe is less than 500 μm, and is another embodiment, is less than 300 μm. 
     The at least one uncoated region  17  is located between coated regions  13  with first coating  15 . The uncoated regions  17  have no coating. The coated regions  13  with first coating  15  and the uncoated regions  17  without first coating  15 , as shown in the embodiment of  FIG. 2 , alternate along the first direction of variation  19 . First direction of variation  19  may run perpendicular to longitudinal direction  11  of furrows  9 . The uncoated regions  17  without first coating  15  can be situated inside furrows  9 . 
     As shown in  FIG. 3A , the stripes  27  are arranged on the top surface  23  of contact surface  7  between uncoated regions  17 , and extend toward base surface  21  of furrows  9 ; as a result, surface offsets  25  of furrows  9  are covered with first coating  15 . Edge regions  31  of each stripe  27  extend in two adjacent furrows  9 . 
     The contact element  3  is used to form an electrical connection with a conductive element (not shown). The contact surface  7  contacts the conductive element to form the electrical connection. If the contact surface  7  according to the invention is pressed against the conductive element, for example by contact surface  7  being arranged in a crimp region which is squeezed onto the conductive element, surface offsets  25  exert a particularly large force onto the conductive element and partially penetrate into the conductive element. Particularly good electrical conductivity and mechanical hardness in the region of surface offsets  25  is of great significance for a good connection between contact surface  7  and the conductive element. Since the surface offsets  25  are covered by coated regions  13  with first coating  15 , a reliable connection between the contact surface  7  and the conductive element is formed. 
       FIG. 3B  shows two additional embodiments of the coated region  13  configuration. The configurations shown are merely exemplary, and the two configurations do not necessarily have to be arranged on the same contact element  3 . 
     The left side of  FIG. 3B  shows a coated region  13  with a smooth surface  16 . In this embodiment, first coating  15  is divided into two different phases  18   a  and  18   b . In the different phases, the material of first coating  15  can have different characteristics. For example, the composition of the material can be different in the two phases, even if they have been generated from the same starting material of first coating  15 . The phases  18   a  and  18   b  can be generated through the selection of a suitable material for first coating  15  and/or a suitable after-treatment, for example, via the energy-rich radiation. Alternatively or in addition, two different materials, for example first coating  15  and a second coating  41 , can be used instead of two different phases  18   a  and  18   b.    
     The right side of  FIG. 3B  shows a coated region  13  with first coating  15 , wherein the surface  16  of the first coating  15  is structured. Surface  16  is structured such that a thickness  20  of first coating  15  varies in cross-section. Surface  16  can have burls, ribs or teeth, for example, such that a structure is formed with varying thickness  20 . 
       FIG. 4  shows a second embodiment of a contact surface  7  according to the invention. For the sake of brevity, only the differences from the contact surface  7  described with reference to  FIGS. 2 and 3  are explored hereafter. 
     The second embodiment of contact surface  7  according to the invention has a second direction of variation  35  which runs parallel to longitudinal direction  11  of furrows  9 . The coated regions  13  therefore also alternate with uncoated regions  17  in the direction of variation  35 . Through the alternating arrangement of coated regions  13  and uncoated regions  17  along two directions of variation  19  and  35  which are perpendicular to one another, an at least partial coating can be achieved with a very low amount of coating material  15 . In order to obtain as uniform a distribution of regions  13  and  17  over contact surface  7  as possible, coated regions  13  have, at least in direction of variation  35 , a length  37 , which substantially corresponds to the length  39  of a uncoated region  17  in direction of variation  35 . Length  39  of uncoated region  17  is the distance between two adjacent regions  13  in direction of variation  35 . 
     Through the described arrangement of coated regions  13  of the second embodiment, direction of variation  39  follows the course of surface offsets  25 , which run parallel to longitudinal direction  11  of furrows  9 . Two coated regions  13  respectively are situated opposite one another over a furrow  9 . Therefore, coated regions  13  are each situated at the same height along longitudinal direction  11  of furrows  9 . 
       FIG. 5  shows a third embodiment of a contact surface  7  according to the invention. Here too, for the sake of brevity, only the differences from the preceding embodiments are described. Coated regions  13  alternate with uncoated regions  17  in two directions of variation  19  and  35 , which are perpendicular to one another. In contrast to the second embodiment, coated regions  13  are, however, staggered relative to one another in longitudinal direction  11  of furrows  9 . As a result, in longitudinal direction  11  of furrows  9 , a coated region  13  is arranged in each case at a surface offset  25  of a furrow  9  between two opposing coated regions  13 . The coated regions  13  can extend into a middle of base surface  21  of furrows  9 . Through the arrangement of regions  13  and  17  of the third embodiment, a substantial covering of contact surface  7  with coated regions  13  can be achieved with a low quantity of coating material. 
       FIG. 6  shows a fourth embodiment of a contact surface  7  according to the invention. Contact surface  7  has coated regions  13  which correspond to those of the embodiment described with reference to  FIG. 5 . Uncoated regions  17 , at least those which are located between coated regions  13  in direction of variation  35 , can have a second coating  41 . Second coating  41  can consist of a material other than first coating  15 . Alternatively or in addition, second coating  41  can also consist of the same material as coating  15 , but, through a suitable treatment, can have a structure which is different from first coating  15 . For example, at least one of coatings  15  or  41  can have a surface  16  or  42  which is structured such that two different surface structures are formed. 
       FIG. 7  shows a fifth embodiment of a contact surface  7  according to the invention. In this embodiment, purely by way of example, coated regions  13  and uncoated regions  17  in inner region  43  are depicted identically to those of the third embodiment described with reference to  FIG. 5 . Inner region  43 , however, can be formed in accordance with each of the embodiments described previously. Inner region  43  can also be formed in accordance with all other contact surfaces  7  according to the invention. 
     In contrast to the embodiments described above, the fifth embodiment of contact surface  7  according to the invention has boundary regions  47  with a third coating  45 . In this case, boundary regions  47  are arranged in an edge region  49  of contact surface  7 . The boundary regions  47  are formed in the form of stripes and follow edge region  49  of contact surface  7 . Individual boundary regions  47  touch or cover one another, such that a continuous boundary region  47  is formed which fully surrounds inner region  43  of contact surface  7 . 
     Third coating  45  is softer than first coating  15  and, if it is present, second coating  41 . Third coating  45  can serve to seal contact surface  7 , in particular if contact surface  7  is part of a crimp section which is pressed together or against another element. Third coating  45  is formed by a metal which is more base than the material of first coating  15 , second coating  41  and contact body  5 . As a result, third coating  45  can serve as a sacrificial anode  51  for contact element  3 . A surface  53  of third coating  45  can be structured similarly to surface  16  of the first coating and surface  42  of the second coating. 
     According to a further advantageous configuration of the invention, at least one coated region  13  or a combination of coated regions  13  can be formed at least in sections as a data-carrying structure. The data-carrying structure can, for example, have data regarding the type or the characteristics of the contact element  13 . Data such as the name or contact information regarding the manufacturer or its logo can be formed in the at least one coated region  13 . The data-carrying structure may be formed as a two-dimensional code, for example as a barcode. A two-dimensional code can vary greatly over a large surface, permitting the first coating  15  to still cover a substantial area. It is likewise possible that the data-carrying structure is formed as a one-dimensional bar code, for example as digits or as letters. 
     Advantageously, according to the invention, the first coating  15  disposed over the surface offsets  25  provides a more reliable electrical connection to another conductive element. Furthermore, by having uncoated regions  17  located between coated regions  15 , coating material and corresponding manufacturing cost can be saved in comparison to a complete coating of the contact surface while maintaining uniform coverage of the contact surface. The alternating arrangement of coated regions  13  and uncoated regions  17  also improves the mechanical stability of the contact element  3  in the region of the contact surface  7 , because twisting, as can arise in the case of large area coating, can be avoided. Furthermore, since one stripe  27  can cover two adjacent surface offsets  25  of two adjacent furrows  9 , manufacturing is easier.