Patent Publication Number: US-2023163504-A1

Title: Electrically Conductive Contact Element for a Connector

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of European Patent Application No. 21306644.2 filed on Nov. 25, 2021, the whole disclosure of which is incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present disclosure relates to a an electrically conductive contact element for a connector. 
     BACKGROUND 
     Electrical connectors are generally used for signal or power transmission and to link electrical and electronic systems. Electrical connectors are provided with electrically conductive contact elements, which come into contact with a contact element of a mating electrical connector when the electrical connector is plugged to the mating electrical connector. The contact elements of the connector element are commonly formed as contact pins and those of the mating connector are commonly formed as contact springs. When the connector and mating connector are coupled, the contact springs exert elastic spring forces on the contact pins and thereby provide an electrical connection between the contact elements. The quality of the electrical connection may be affected by mechanical and/or chemical degradations occurring at the contact surfaces of the contact elements. The respective contact surface of the electrically conductive contact elements may be coated with a layer of tin, nickel or alloys thereof. 
     As in motor vehicles, electrical connectors may be exposed to broad temperature variations, vibrations and corrosive environment, it can cause damages to the layer coating the contact surface. Fretting corrosion is known as a degradation resulting from the combination of a mechanical motion and a chemical reaction. The combination of the relative motion of mated contact surfaces, causing fretting wear, with corrosion (like oxidation) may lead to fretting corrosion. Fretting corrosion leads to the formation of insulating oxide layers in contact areas and can cause an increase of the electrical contact resistance. Moreover, wear damages (e.g., abrasion) at the contact surfaces of the contact elements may also lead to an increase of the electrical constriction resistance. As the performance of the electrical connector is related to the reliability of the electrical contacts, there is a need for preventing wear damage at the contact surfaces so as to avoid malfunction due to the increase in electrical resistance. 
     Along with improving wear and corrosion resistance, low plugging and pulling forces are required in order to facilitate the mounting and maintenance of electrical connectors. In order to reduce the plugging force, the surface wear or fretting corrosion, the contact surfaces of the connectors from the prior art are oiled or greased. However, greased or oiled contact surfaces lose the applied grease or oil when in operation. For addressing this drawback related to the use of grease or oil in the contact surfaces, it is known to provide an electrically conductive contact element for an electrical connector comprising a contact surface having a plurality of caverns arranged under the contact surface in a microstructure and having a lubricant filled and enclosed in the plurality of caverns. The spatial dimensions in the caverns are in the range of 0.1-50 micrometers. The arrangement of the caverns is such that an outlet of the cavern is tight enough so that the lubricant filled into the caverns cannot be accessed without establishing an opening from the contact surfaces into the cavern. Manufacturing the microstructure requires the use of a laser, an electron beam or surface treatment like masking and etching. 
     The object of the present invention is to provide an improved and cost-effective contact element for a connector which can better withstand wear so as to reduce the contact resistance while reducing the mating force to ease the assembly and the maintenance of the connector, in particular without the need of using lubricant. 
     SUMMARY 
     According to an embodiment of the present disclosure, an electrically conductive contact element for an electrical connector comprises a body and a layer of electrically conductive material provided on the body. The body includes a first face having at least one depression forming a reservoir defined therein. The layer of electrically conductive material is provided on the first face of the body and fills the at least one depression. The layer defines a contact surface adapted to be brought into contact with a surface of a connecting part of a mating electrical connector mated with the electrical connector. The contact surface is formed by a surface of the layer of electrically conductive material facing away from the body. 
    
    
     
       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 partial cross-sectional view of an electrically conductive contact element according to a first embodiment of the present invention at an initial stage. 
         FIG.  2    illustrates a body of the electrically conductive contact element shown in  FIG.  1   . 
         FIG.  3    illustrates a partial cross-sectional view of an electrically conductive contact element according to a second embodiment of the present invention at an initial stage. 
         FIG.  4 A  illustrates a top view of the electrically conductive contact element according to the second embodiment of the present invention at a later stage than the initial stage. 
         FIG.  4 B  illustrates a cross-sectional view of the electrically conductive contact element shown in  FIG.  4 A . 
         FIG.  5    illustrates an enlarged view of a body of an electrically conductive contact element according to a third embodiment of the present invention. 
         FIGS.  6 A,  6 B and  6 C  illustrate successive steps of a method of manufacturing a contact surface of the electrically conductive contact element according to the third embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Exemplary embodiments of the present disclosure will be described hereinafter in detail with reference to the attached drawings, wherein the like reference numerals refer to the like elements. The present disclosure may, however, be embodied in many different forms and should not be construed as being limited to the embodiment 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. 
     In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. It will be apparent, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are schematically shown in order to simplify the drawing. 
       FIG.  1    and  FIG.  2    illustrate a partial cross-sectional view of a body of an electrically conductive contact element  10  according to a first embodiment of the present invention. In  FIG.  1   , a contact surface is represented, while in  FIG.  2    the contact surface is omitted in order to better highlight the structure of the body of the electrically conductive contact element  10 . The electrically conductive contact element  10  for an electrical connector comprises a body  12 , in particular a metallic body. The body  12  is delimited by a plurality of faces. According to the present disclosure, at least one face  14  of the body  12  is provided with a depression  16 . The face  14  extends in a plane (XY) in the example of  FIGS.  1  and  2   . The depression  16  extends from an opening  18  in the face  14  partially into the body  12  along a direction parallel to the axis Z. In the first embodiment, the depression  16  has a substantially half-spherical shape. The diameter L1 of the corresponding circular opening  18  can be greater than 0.05 mm, in particular can be comprised between 0.05 mm and 0.06 mm. The maximum depth L2 of the depression  16  is greater than 0.01 mm. Namely, the maximum depth L2 of the depression  16  can be greater than 0.03 mm, in particular greater than 0.04 mm, more in particular greater than 0.05 mm. It is noted that wording “greater” is to be read as “equal or greater”, and not “strictly greater”. 
     In one embodiment, the depression  16  can have a groove shape, in particular a rounded groove shape. However, the opening  18  of the depression  16  can have a square shape, a rectangular shape, an oval shape, triangular shape, etc. without departing from the scope of the present disclosure. The depression  16  forms a reservoir  20 .  FIG.  2    illustrates an empty reservoir  20  in order to better highlight the structure of the depression  16 . As mentioned above and emphasized in  FIG.  2   , the depression  16  has one open-end  18 . 
     As shown in  FIG.  1   , a layer  22  of an electrically conductive material M of thickness L3 is provided on the face  14  of the body  12 . The electrically conductive material M is a plating material that can be made of tin, nickel, silver, gold, a tin-nickel alloy, an alloy of tin or nickel-silver alloy. In the first embodiment, the layer  22  of the electrically conductive material M is directly provided on the face  14 . A surface  24  of the layer  22  facing away from the body  12  of the electrically conductive contact element  10  forms a contact surface  24 . The contact surface  24  extends substantially in the plane (XY). The contact surface  24  is configured to be brought into contact with a surface of a connecting part of a mating electrical connector. 
     As shown at the initial stage represented in  FIG.  1   , in the first embodiment, a thickness T1 of electrically conductive material M is provided above a deepest point A of the reservoir  20 , wherein T1=L2+L3. The initial stage relates to a stage wherein the electrically conductive contact element  10  has not yet being brought in contact with an electrically conductive contact element of a mating connector. Hence, at the initial stage mechanical wear, corrosion, abrasion or any damages that may result from the mating surfaces have not yet occurred. That is why in the initial stage, as shown in  FIG.  1   , the contact surface  24  is substantially flat in the plane (XY). 
     In the following, elements with the same reference numeral already described and illustrated with respect to  FIGS.  1  and  2    will not necessarily be described in detail again, but reference is made to the previous description of the same reference numeral. 
       FIG.  3    illustrates a partial cross-sectional view of a body of an electrically conductive contact element  30  according to a second embodiment of the present invention. In comparison to the first embodiment, in the second embodiment an adhesion layer  32  is directly provided on the face  14  of the body  12  and sandwiched between the face  14  of the body  12  and the layer  22  of the electrically conductive material M. The adhesion layer  32  is provided with a substantially uniform thickness L4 on the face  14 , including on the face  14  in the depression  16 , as shown in  FIG.  3   . In the second embodiment, the layer  22  has a thickness L3′, wherein L3′&lt;L3. As shown in the initial stage represented in  FIG.  3   , in the second embodiment, a thickness T2 of electrically conductive material M is provided above the deepest point A of the reservoir  20 , wherein T2=L3′+(L2−L4). In a variant (not represented), further layers may be sandwiched between the face  14  of the body  12  and the layer  22  of the electrically conductive material M. 
       FIG.  4 A  illustrates a top view of the electrically conductive contact element  30  according to the second embodiment of the present invention at a later stage than the initial stage, wherein mechanical and/or chemical wear has occurred.  FIG.  4 B  illustrates a cross-sectional view of the electrically conductive contact element  30  shown in  FIG.  4 A .  FIG.  4 A  and  FIG.  4 B  are described together in the following. 
     In the following, elements with the same reference numeral already described and illustrated with respect to  FIGS.  1  to  3    will not necessarily be described in detail again, but reference is made to the previous description of the same reference numeral. In the stage of wear shown in  FIGS.  4 A,  4 B , the mechanical and/chemical wear has caused a disruption  40  in the contact surface  24  leading to the exposure of the adhesion layer  32 . At a later stage (not represented), the further removal of the adhesion layer  32  could lead to the exposure of the face  14  of the body  12 . In the example of  FIG.  4 A , the disruption  40  has the shape of a groove  42  extending along the axis X. Such linear groove shape may be caused by a back-and-forth motion of the mating contact surfaces for example. Other shapes (not represented) of disruption  40  in the contact surface  24  may occur, depending on the relative motions of the connector and the mating connector for instance. According to the present invention, the presence of the depression  16  in the body  12  allows providing a reservoir  20  of electrically conductive material M such that at the wear stage of  FIGS.  4 A and  4 B , a contact area  44  of electrically conductive material M still remains at the contact surface  24  despite the disruption  40 . 
     As shown in  FIG.  4 B , in the wear stage represented in  FIGS.  4 A and  4 B , a thickness T3, wherein T3&lt;T2, of electrically conductive material M above the deepest point A of the depression  16  still remains in the reservoir  20 . Hence, an uneven wear at the contact surface  24  is achieved allowing providing at least one contact area  44  of low electrical contact resistance. It is noted that the same effect of providing a contact area  44  of electrically conductive material M would occur in the electrically conductive contact element  10  according to the first embodiment. In contrast with the second embodiment, a disruption  40  in the contact surface  24  in the contact element  10  according to the first embodiment would lead to expose directly the face  14  of the body  12 , due to the absence of an adhesion layer. 
       FIG.  5    illustrates an enlarged view of an electrically conductive contact element  50  according to a third embodiment of the present invention. In order to show the depressions  16  formed in the electrically conductive contact element  50 , the electrically conductive material M and the optional adhesive layer  52  is not represented in  FIG.  5   . The electrically conductive contact element  50  according to a third embodiment has a metallic body  52  comprising a frame  54  extending in a plane (XY) and defining an aperture  56 . Four contact pins  58  extends within the frame  54  across the aperture  56 . The number of contact pins  58  is not limitative. Each contact pins  58  are bent with respect to the plan (XY) such as to be provided with two slightly curved regions R 1  and R 2 . The number of curved regions is not limitative. 
     The curved regions R 1 , R 2  consist of the regions of the electrically conductive contact element  50  onto which greater elastic spring forces are exerted in comparison with the rest of the contact pins  58 . Elastic spring forces is intended to be exerted on the curved regions R 1 , R 2  by a connecting part of a mating connector applying a pressure on the curved regions R 1 , R 2  in a mating state of the connectors. The curved regions R 1 , R 2  are provided with a plurality of depressions  16  formed in the face  14  of the metallic body  52 , as previously described in reference to  FIGS.  1    and  2 . The depressions  16  of the plurality of depressions  16  are spaced away from each other by a minimal distance d1, wherein d1 is comprised between 0.10 mm and 0.15 mm. In particular, d1=0.125 mm. The location of the plurality of depressions  16  at the curved regions R 1 , R 2  allows improving the wear resistance at the area most subject to mechanical stress, and therefore to wear. The plurality of depressions  16  provide a redundancy of improved contact areas, thereby enhancing the reliability and durability of the electrical contact between the electrical connectors. 
       FIGS.  6 A,  6 B and  6 C  illustrate successive steps of a method of manufacturing a contact surface of the electrically conductive contact element  50  according to the third embodiment of the present invention. At the step represented by  FIG.  6 A , the face  14  of the metallic body  12  at the contact pin  58  is substantially uniform. At the step represented by  FIG.  6 B , a plurality of depressions  16  has been formed by metal punching in the face  14  of the metallic body  12  at the contact pin  58 . In the example of  FIG.  6 A , each depression  16  has a substantially half-spherical shape. In a variant (not represented), the depressions  16  can have a different shape than a substantially half-spherical shape. In another variant (not represented), the plurality of depressions  16  can comprise a combination of depressions  16  of different shapes and/or sizes. At the last step of the manufacturing method represented by  FIG.  6 C , a plating layer  22  of the electrically conductive material M of thickness L5 has been provided on the face  14  of the metallic body  12  thereby coating the face  14  and filling each depression  16  with the electrically conductive material M. The surface  24  of the plating layer  22  facing away from the body  52  forms the contact surface  24  of the electrically conductive contact element  50 . 
     In addition, those areas in which it is believed that those of ordinary skill in the art are familiar, have not been described herein in order not to unnecessarily obscure the invention described. Accordingly, it has to be understood that the invention is not to be limited by the specific illustrative embodiments, but only by the scope of the appended claims. 
     It should be appreciated for those skilled in this art that the above embodiments are intended to be illustrated, and not restrictive. For example, many modifications may be made to the above embodiments by those skilled in this art, and various features described in different embodiments may be freely combined with each other without conflicting in configuration or principle. 
     Although several exemplary embodiments have been shown and described, it would be appreciated by those skilled in the art that various changes or modifications may be made in these embodiments without departing from the principles and spirit of the disclosure, the scope of which is defined in the claims and their equivalents. 
     As used herein, an element recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural of the elements or steps, unless such exclusion is explicitly stated. Furthermore, references to “one embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Moreover, unless explicitly stated to the contrary, embodiments “comprising” or “having” an element or a plurality of elements having a particular property may include additional such elements not having that property.