Patent Publication Number: US-2013244511-A1

Title: Terminal assembly and method for connecting an electric wire to a terminal element

Description:
The present invention relates to a method for mechanically and electrically connecting an electric wire to a terminal element. The present invention further relates to a terminal assembly comprising a terminal element, and at least one electric wire that is mechanically and electrically connected to the terminal element. 
     The present invention further relates to a method for producing an electrical device comprising the method for mechanically and electrically connecting an electric wire to a terminal element according to the present invention, as well as an electrical device comprising a terminal assembly according to the present invention. 
     In electric components and electrical devices, such as connectors, USB cables and the like, an electric wire or cable is mechanically and electrically connected to a terminal element or connector. One way for mechanically and electrically connecting the wire to the terminal element that is used in consumer assemblies and is common for printed circuit board terminals is to solder the wire to the terminal element. 
     However, soldering technology is difficult to automate. Further, stacking different wires to one terminal, such as a connector of a PCB, is limited due to the pitch required for keeping the adjacent soldering positions apart from each other. A soldering connection may also be problematic in respect of the connection&#39;s mechanical stability and reliability, in particular when the terminal assembly is subjected to rough environmental conditions, e.g. in consumer devices such as USB charger cables. 
     Reliable types of connection for the terminal assembly are crimped connectors. Crimped connectors are commonly provided with corresponding piercing tines that are used as penetration connectors for contacting the electric conductors, such as flexible flat cables or flexible printed circuit boards. 
     However, a crimp connector has to be specifically designed with piercing tines or other specific protrusions that are plastically deformed during the crimping process for mechanically fixing the wire to the connector. Further, the electric connection may be troublesome to achieve in crimped connectors. This makes automation of crimp connectors difficult, and the specific design of said connectors raises their costs. 
     In view of the above, the object of the present invention is to provide an improved terminal assembly and an improved method for mechanically and electrically connecting an electric wire to the terminal element, that is cheap and simple, is easy to automate, and at the same time, provides a stable and reliable connection. 
     The initially mentioned method solves the above problem by comprising the steps of arranging a connecting portion of the electric wire substantially parallel to an entrance surface of a contact opening; and contacting the joining section of the connecting portion with the contact opening by plastically deforming the lateral cut of the joining section. 
     A terminal element in the sense of the present invention refers to the part which forms the portion to which a wire is to be contacted. Preferred examples of a terminal element are a terminal contact, a printed circuit board, a conductive foil and similar devices to which a wire can be contacted. A terminal element can therefore be any device which can be connected with a wire in the sense of the present invention. 
     The method step of contacting the joining section of the connecting portion with the contact opening is preferably achieved by a pressing step, i.e. by pressing the wire into the contact opening. However, any deforming step suitable to achieve the plastic deformation may be used according to the claimed invention. 
     The terminal assembly, as initially mentioned, solves the above defined problem in that the terminal assembly comprises a terminal element having at least one contact opening, and at least one electric wire that is mechanically and electrically connected to the contact opening, wherein a connecting portion of the electric wire that is located outside the contact opening runs substantially parallel to an entrance surface of the contact opening, and wherein a joining section of the connecting portion is plastically deformed into and thereby non-positively connected to the contact opening. 
     By arranging the electric wire parallel with the contact opening and then connecting a portion of the wire, namely the joining section with the contact opening, e.g. by pressing the joining section into the contact opening, a mechanically and electrically secure connection can be provided between the electric wire and the terminal element, namely between the joining section of the wire and the contact opening of the terminal element. This way of providing a secure connection is easy to automate and good to control. The plastic deformation of the joining section provides for a reliable non-positive connection with the contact opening. No specific design of the terminal element is required for the connection since the joining section of the wire is plastically deformed. Hence, a simple terminal element can be provided at low cost because no special connecting elements are necessary. Finally, stacking various electrical wires at a low pitch on one terminal element is possible, because the pitch is only limited by the distance at which adjacent contact openings can be produced in the terminal element. 
     The solution according to the invention may be combined in any way with the following advantageous embodiments of the present invention respectively and further improved. 
     In a first embodiment of the terminal assembly, the contact opening can be elongated in the direction of the electrical wire. In the method for mechanically and electrically connecting the wire to the terminal element, the connecting portion of the electric wire can be arranged substantially parallel to the entrance surface of the contact opening and also parallel to the longitudinal direction of the contact opening prior to contacting. Upon contacting, the joining section of the connection portion, that is the part of the connection portion that is in alignment with the elongated contact opening is increased. Thereby the contact area between the joining section and the contact opening can be increased. This improves the non-positive connection between the wire and the terminal element. 
     To further improve the connection between the wire and the terminal element, in a further embodiment of the terminal assembly, the contact opening can be provided with at least one undercut. The undercut can be designed as at least one protrusion protruding into the contact opening and/or at least one cavity forming a dent widening the contact opening. In providing the contact opening of the terminal element with an undercut, the joining section of the terminal assembly can be plastically deformed into a form fit connection with the undercut. This further improves the mechanical and electrical connection of the wire with the terminal element. The undercut may be arranged in the direction that is parallel to the entrance surface of the contact opening. Thereby a positive joint against displacing the joining section relative to the contact opening in the plane of the surface entrance can be formed. Alternatively and/or additionally, the undercut may be in the direction perpendicular to the entrance surface securing the joining section in the contact opening against moving the joining section out of the contact opening. 
     In a further embodiment, the elongated contact opening can be designed as a channel or groove having a substantially rectangular surface entrance. A channel or groove can be easily aligned with the joining section of the electrical wire. Also, such channel can be easily designed with an undercut, for example a channel having protrusions extending from the side walls of the channel into the channel or a groove having indentations that section-wise widen the channel. An undercut that is formed in the direction perpendicular to the surface entrance can be formed by, e.g. widening the channel in the direction from the entrance opening to the bottom, e.g. in the form of a dovetail. 
     In further embodiment, the contact opening may be formed as a through-hole extending from the entrance surface on one side of the terminal element to an exit surface on another side of the terminal element. For example, an elongated contact opening may thus form an aperture in the form of a slot. Such aperture or through-hole is easy to manufacture, e.g. by punching, because one does not have to take care of the depth of the opening. 
     Furthermore, a through-hole can improve the non-positive or force-fit connection with an additional form-fit or positive joint since the joining section, that is made of a malleable material deformed upon contacting, can be plastically deformed such that the joining section extends through the through-hole and is formed into a stopper overlaying the entrance surface and the exit surface on both sides of the terminal element. The stopper can be arranged outside the surface opening adjacent to the entrance surface and can be designed such that it extends at least section-wise over the entrance surface. Thereby the stopper can be brought into abutment with the portion of the terminal element surrounding the contact opening in the direction perpendicular to the entrance surface and the exit surface. This can be easily achieved when, during contacting, the joining section outside the contact opening is deformed as overlaying the entrance surface. The stopper may be formed for example by widening a portion of the joining section that remains outside the contact opening. The widening may be performed for example by flattening the joining section in the form of a rivet head, forming a flaring, a flange or bulge extending over the circumference of the entrance/exit surface. 
     In another embodiment, the volume of the wire in the joining section is greater than the volume of the contact opening. When contacting, e.g. pressing the joining section into the contact opening, the joining section substantially fills up the contact opening. Thereby, the contact area of the force-fit connection is maximized as the entire part of the joining section that is in parallel with the contact opening can be plastically deformed into the contact opening. 
     In a further embodiment of the method, for contacting, the joining section may be pressed into the contact opening in an insertion direction that runs substantially perpendicular to the entrance surface of the contact opening. Thereby, the strain applied to the terminal element in the area of the contact opening can be reduced and most of the pressure applied during contacting can be transformed into the plastic deformation of the malleable joining section of the wire. For an embodiment having an aperture or through-hole, a deformation tool or unit can be used, such as a tool having a first deformation element, e.g. a die pressing the joining section in the insertion direction into the contact opening and a second deformation element, e.g. a further die or anvil that is arranged at the exit of the through-hole. Thereby the joining section can be plastically deformed by pressing it in the insertion direction into the contact opening, filling up the contact opening and flattening or widening the portion of the joining section swelling out of the exit opening and the portion of the joining section that remained outside the entrance of the contact opening into stoppers overlaying the entrance and the exit surface. In this way a form-fit can be provided at the entrance and at the exit of the through-hole. 
     The wire to be mechanically and electrically connected to the terminal element can be a solid wire, a stranded wire or a magnet wire. As far as the volume of the joining section is greater than the volume of the contact opening, an arbitrary wire can be used. Hence, even flat wires with the necessary volume may be used. Excluded are only flat wires whose cross sectional diameter is too small, that is, wires that do not provide sufficient material to allow plastic deformation to fix the wire into the contact opening. When using a magnet wire or a wire having an insulation coating surrounding the lead or conductor of the wire, the insulation coating of the wire can be removed in the joining section during contacting the joining section with the contact opening in a further embodiment. The removal of the insulation coating may be achieved, e.g. by designing the entrance opening such that the insulation coating is scraped off the lead upon the plastic deformation. Such scraping off is for example automatically achieved when the width of the lead or the conductor of the wire in the joining section is smaller than the width of the entrance surface. 
     The above described terminal assembly can be used in a method for producing an electric device and can be a component of an electric device, such as a USB cable, of the present invention. The above described method of the invention can be part of a method for producing an electric device according to the present invention. For example, the method for producing the electric device can comprise method of forming the terminal assembly of the present invention first. Thereafter, at least one terminal assembly can be placed in or can be arranged at the housing of the device. Optionally, the wires of the the terminal assembly can be twisted, bundled, foiled and/or braided. 
    
    
     
       The invention is described hereafter by means of example referring to exemplary embodiments with reference to the drawings. The various features of the described embodiments can be combined or omitted independently of one another, as already described above. 
       In the drawings: 
         FIG. 1 : is a schematic perspective view of the terminal assembly according to a first embodiment in the pre-assembled state; 
         FIG. 2 : is a schematic perspective view of the terminal assembly of  FIG. 1  in the assembled state; 
         FIG. 3 : is a schematic perspective view of section A of  FIG. 2  showing the cross-sectional representation at the sectional line A′-A′; 
         FIGS. 4A and 4B : are schematic perspective views of a terminal assembly according to a second embodiment in the pre-assembled sate ( FIG. 4A ) and in the assembled state ( FIG. 4B ); 
         FIGS. 5A and 5B : are schematic perspective views of a terminal assembly according to a third embodiment in the pre-assembled sate ( FIG. 5A ) and in the assembled state ( FIG. 5B ); 
         FIGS. 6A and 6B : are schematic perspective views of a terminal assembly according to a fourth embodiment in the pre-assembled sate ( FIG. 6A ) and in the assembled state ( FIG. 6B ); 
         FIGS. 7A and 7B : are schematic perspective views of a terminal assembly according to a fifth embodiment in the pre-assembled state ( FIG. 7A ) and in the assembled state ( FIG. 7B ); 
         FIG. 8 : is a schematic planar view of a valve of a sixth embodiment of the terminal assembly taken along a cross-sectional line corresponding to a cross-sectional line A′-A′ of  FIG. 2 ; 
         FIG. 9 : is a terminal assembly in a seventh embodiment in the pre-assembled state; and 
         FIGS. 10A and 10B : are schematic perspective views of the terminal assembly of  FIG. 9  in the assembled state, wherein in  FIG. 10B  a part of this terminal assembly is cut off for showing a lateral cut of the terminal assembly corresponding to the cut A′-A′ of  FIG. 2 . 
     
    
    
     Hereafter preferred embodiments of the terminal assembly  1  and methods for electrically and mechanically connecting an electric wire  2  to the terminal element  3  of said terminal assembly  1  are described with reference to the drawings. 
     The terminal element  3  of the embodiment shown in  FIG. 1  has generally a plate-like structure having a connecting part  4  and a wire attachment or contact portion  5 . Hence, the terminal element according to this embodiment refers to what is generally known as a terminal connector  3 . In the following embodiment, the terminal element  3  will be referred to as a terminal  3 . The terminal  3  of the embodiment has the form of a T-shaped plate, whereby the rectangularly formed contact portion  5  passes into the middle of the connecting part  4  so that the contact portion  5  forms the base and the connecting part  4  forms the cross bar of the T-shaped terminal plate  3  according to the embodiment of  FIG. 1 . 
     The connecting part  4  is provided with two attachment holes  6 . The attachment holes  6  are designed as through-holes for inserting a bolt or a screw as fastening means for fastening the terminal  3  to an electric apparatus (not shown). The terminal  3  of the embodiment shown in  FIG. 1  is made of a material that conducts electricity so that once the electric wire  2  is joined with the contact portion  5  of the terminal  3 , the connecting part  4  is electrically connected to the wire  2 . 
     In the contact portion  5 , the contact opening  7  is provided. The contact opening  7  is elongated in the longitudinal direction L of the terminal  3 . The wire  2  is principally aligned with the longitudinal direction L of the terminal  3 , in which longitudinal direction L the contact opening  7  is also elongated. For mechanically and electrically connecting the electric wire  2  to the terminal  3 , at least the connecting portion  8  of the wire  2  is aligned parallel to the entrance surface  9  of the contact opening  7 , which entrance surface  9  is arranged at the upper side  10  of the terminal  3 . Furthermore, the connecting portion  8  of the wire  2 , namely the longitudinal axis  1  of the wire  2  is aligned with the longitudinal direction L of the terminal  3  and the elongated contact opening  7 . 
     In the first embodiment of  FIGS. 1 to 3 , the contact opening  7  is designed as the through-hole  7 ′, extending from the entrance surface  9  at the upper side  10  of the contact portion  5  up to the exit surface  11  at the lower side  12  of the contact portion  5 . Due to the elongated shape of the contact opening  7 , the through-hole  7 ′ is designed as a slot  7 ″ extending along the longitudinal direction L. The lateral sides  13  of the slot  7 ″ are provided with an undercut  14 . In the shown embodiment, the undercut  14  is formed as a cavity  15  forming a dent, in which the width w taken along the width direction W of the contact opening  7  and the terminal  3  is widened. 
     Alternatively, the undercut  14  could be designed by protrusions (not shown) extending from the lateral sides  13  of the slot  7 ″ into the contact opening  7  thereby reducing the width w of the slot  7 ″ at the position of the undercuts  14 . 
     The wire  2  of the embodiment of  FIG. 1  comprises a solid conductor or lead  16  that is covered on the outside with an insulating coating  17  insulating the conductor  16  against the outside. 
     The connecting portion  8  of the wire  2  is located at one end of the wire  2 . In the connecting portion  8 , the insulating coating  17  of the wire  2  is removed in the embodiment shown in  FIG. 1  so that the blank conductor  16  is exposed and can be mechanically and electrically connected to the contact opening  7 , as described in the following by example with reference to the first embodiment of the terminal assembly according to  FIGS. 1 to 3 . 
     For mechanically and electrically connecting the wire  2  to the terminal  3 , the joining section  18  of the connecting portion  8  is contacted with the contact opening  7 . During the contacting step, the joining section  18  is plastically deformed by pressing it into the contact opening  7 , in an insertion or press direction I that is substantially perpendicular to the entrance surface  9  and the upper side  10  of the contact portion  5  as well as perpendicular to the longitudinal axis  1  of the aligned wire  2 . By pressing in the insertion direction I, the joining section  18  enters through the entrance surface  9  into the contact opening  7 . Thereby the lateral cut  19  of the joining section  18  is plastically deformed since the width w of the contact opening  7  of the entrance surface  9  is smaller than the width w the diameter d of the conductor  16 . Since the conductor  16  is made from a malleable material, the joining section  18  is force-fitted into the contact opening  7  by contacting the joining section  18  with the contact opening  7 . For ensuring a secure non-positive connection between the wire  2  and the contact opening  7 , the lead  16  in the joining section  18  has to be provided with sufficient material to allow plastic deformation achieving a non-positive connection due to plastic deformation of the wire  2 . 
     The terminal assembly  1  of the first embodiment in the assembled state is shown in  FIGS. 2 and 3 . As can be seen in  FIG. 2 , the joining section  18 , that is that part of the connecting portion  8  of the wire  2  that is aligned with the contact opening  17  and is plastically deformed forming the connection between the wire  2  and the terminal  3 , substantially fills up the complete slot  7 ″ that forms a contact opening  7  in the first embodiment. By filling up the complete contact opening  7 , the contact area between the deformed joining section  18  and the contact opening  7  is maximized thereby maximizing the force-fit connection between the wire  2  and the contact opening  7 . 
     The contacting step of plastically deforming the joining section  18 , in the shown embodiment, the step of pressing the conductor  16  into the contact opening  7  to form the joining section  18  can, for example, be conducted by using a deformation or pressing tool (not shown). The pressing tool may comprise a deformation unit (not shown) with a substantially flat surface that presses the connecting portion  8  in the insertion direction I against the contact portion  5  of the terminal  3  having the contact opening  7 . The joining section  18  of the wire  2  that is aligned with a contact opening  7  is deformed such that the malleable lead  16  is pressed into the contact opening  7 , and through the complete contact opening  7  from its entrance surface  9  to its exit surface  11 . After the joining section  18  swells out of the exit surface  11 , a counter-deformation unit (not shown) is pressed against the insertion direction I from the lower side  12  of the contact portion  5  against the part of the joining section  18  that swells out of the exit surface  11 . By compressing the joining section  18  from the upper side  11  and from the lower side  12 , the lateral cut  19  of the joining section  18  is deformed thereby contacting the joining section  18  with the contact opening  7 . The part  18   a  of the joining section  18  that is situated in the contact opening  7  after the contacting step forms the non-positive connection of the wire  2  with the terminal  3  that ensures the mechanical and electrical assembling of the terminal assembly  1 . Since the volume of the joining section  18  is greater than the volume of the contact opening  7 , a part of the joining section  18  remains outside the contact opening  7  at the upper side  10 , which part did not enter the contact opening  7 . Another part of the joining section  18  that swelled out of the exit surface  11  is also located outside the contact opening  7  on the lower side  12 . 
     Due to the flat surface of the deformation unit (not shown), pressing the joining section  18  in the insertion direction I from the upper side  10 , the portion at the upper side  10  forms a stopper  20  that seals and overlays the entrance surface  9  of the contact opening  7 . The stopper  20  on the upper side  10  has the shape of a flat plate and extends, in the width direction W and against the width direction W over the lateral sides  13  of the slot  7 ′, thereby forming a form-fit connection of the joining section  18 , securing the wire  2  in the insertion direction I in the contact opening  7 . 
     A similar stopper  20   a  is formed at the lower side  12  of the contact portion  5 . This stopper  20   a  overlays the exit surface  11  in a similar manner as the stopper  20  overlayers the entrance surface  9  of the upper side  10 . Thus, the stopper  20   a  secures the joining section  18  in a form-fit manner in the contact opening  7  against in the direction opposite to the insertion direction I. 
     The only difference between the stopper  20  at the upper side  10  and the stopper  20   a  at the lower side  12  is that the lower stopper  20   a  has not a substantially planar shape but is rather formed with two bulges  21  and  21 ′. One of each bulge  21 ,  21 ′ extends over one of the lateral sides  13  at the exit surface  11  of the contact opening  7 . The two bulges  21 ,  21 ′ meet approximately in the middle of the exit surface  11 , so that the stopper  20   a  at the lower side  12  is provided with a central groove  22 . By forming the stopper  20   a  with two bulges  20 ,  20 ′ and a middle channel or groove  22 , the secure form-fit can be formed even with a minimum amount of material of the joining section  18  swelling out of the exit surface  11  because less material is required in the channel  22  and nearly all the swelling out material can be deformed and pressed in and against the width direction W forming the two bulges  21  and  21 ′. 
     As can be seen in  FIG. 2 , the remainder of the connecting portion  18  that is not aligned with the contact opening  7  and therefore does not form the joining section  18 , is pressed against the upper side  10  of the contact portion  5  of the terminal  3  forming a transition section  23  that is located between the joining section  18  and the remaining wire  2  outside the connecting portion. Since the transitions section  23  is not pressed into the contact opening  7 , the transition section  23  is flattened, however, remains higher than the stopper  20  of the joining section  18 . 
     In the following, further embodiments of the terminal assembly  1  are presented. For elements having a similar or identical structure/function as elements of the first embodiment, the same reference signs are used. In the following, only the differences between the further embodiments of the terminal assembly  1  with respect to the first embodiment shown in  FIGS. 1 to 3  are described. 
     The second embodiment of the terminal assembly  1  is shown in  FIGS. 4A and 4B .  FIG. 4A  illustrates the terminal assembly  1  comprising the wire  2  and the terminal element  3  in the pre-assembled state. The assembled state, wherein the wire  2  is contacted to the contact portion  5  of the terminal element  3  can be seen in  FIG. 4B . 
     The terminal assembly  1  of the second embodiment principally corresponds to the terminal assembly  1  of the first embodiment shown in  FIGS. 1 to 3 . 
     The only difference is that the connecting portion  5  of the second embodiment is at the free end  24 , facing away from the connecting portion  4 , provided with a crimp barrel  25 . The crimp barrel  25  is designed, in the pre-assembled state shown in  FIG. 4A , by a pair of crimping pieces  26  arranged in a portion having a substantially U-shaped section. The two crimping pieces  26  form a recess  27 , in which the wire  2 , having the insulating coating  17  can be introduced when assembling the terminal assembly  1 . After insertion of the wire  2  in the recess  27 , the crimping pieces  26  are bent with their free ends towards each other embracing and fixing the wire  2  in the recess  27 . 
     By providing the terminal  3  with a crimping barrel  25 , an additional joint can be formed between the wire  2  and the terminal element  3 . Said additional joint will take up the main load if someone pulls at the wire  2 , thereby reducing the tensions at the connection between the joining section  18  and the opening  7 . 
       FIGS. 5A and 5B  illustrate a third embodiment of the terminal assembly  1  having a wire or cable  2  and a terminal element  3 .  FIG. 5A  shows the terminal assembly  1  of the third embodiment in the pre-assembled state.  FIG. 5B  displays the terminal assembly  1  of the third embodiment in the assembled state, where the wire  2  is mechanically and electrically connected to the terminal element  3 . 
     The terminal element  3  of the third embodiment is identical to the terminal element  3  of the first embodiment shown in  FIGS. 1 to 3 . 
     Contrary to the terminal assembly  1  of the first embodiment, the terminal assembly  1  of the third embodiment comprises a magnet wire  2 ′. The magnet wire  2 ′ is a wire conductor  16 , usually of copper or aluminium, that is covered with a thin insulation  17 . The thin insulation  17  of the magnet wire  2 ′ covers the complete lead  16  so that in the pre-assembled state shown in  FIG. 5A , the connecting portion  8  is also provided with an insulating coating  17 , contrary to the wire  2  of the first embodiment. 
     According to the third embodiment of  FIGS. 5A and 5B , the insulating coating  17  of the wire  2 ′ is removed in the joining section  18  during the step of contacting the joining section  18  with the contact opening  7 . Since the diameter d of the magnet wire  2 ′ is larger than the width w of the slot  7 ′ forming the contact opening  7  of the terminal  3 , the insulating coating  17  is removed from the lead  16  in the joining section  18  upon plastically deforming the lateral cut  19  of the joining section  18  when contacting said joining section  18  with the terminal  3 . 
     As can be seen in  FIG. 5B , only in those sections of the wire  2 ′ that are wider than the width w of the slot  7 ′, the insulation coating  17  is scraped off and thereby removed, allowing an electrical connection between the lead  16  and the terminal  3 . At those sections of the magnet wire  2 ′, that are aligned with the contact opening  7 , and do not extend beyond the lateral sides  13  of the slot  7 ′, the insulation  17  remain in place as in these sections, the insulation  17  is not scraped of at the edge  28  of the entrance  9 . Therefore, the joining section  18  is still isolated at the stoppers  20  and  20   a  exposed at the upper side  10  and the lower side  12  of the terminal  3 . 
     Finally, it can be seen in  FIG. 5B  that the joining section  18 , upon filing up the contact opening  7 , also fills up the cavities  15  provided at those lateral sides  13  of the slots  7 ″. Thereby, a further form-fit is provided between the joining section  18  and the undercut  14  in the contact opening  7  which secures the joining section  18  against transition of the joining section  18  in and against the longitudinal direction L in the contact opening  7 . 
     The fourth embodiment of the terminal assembly  1 , that is shown in  FIGS. 6A  (pre-assembled state) and  6 B (assembled state) comprises a terminal element  3  that is principally identical to the terminal element  3  of the first and third embodiment. The wire  2  of the terminal assembly  1  is a solid wire  2  similar to the wire  2  of the first embodiment. However, contrary to the first embodiment, the insulating coating  17  of the wire  2  in the fourth embodiment extends onto the connecting portion  8  and principally covers the complete lead  16 . 
     Similar to an insulation displacement connector, the terminal  3  of the fourth embodiment of  FIGS. 6A and 6B  removes the insulation coating  17  in the joining section  18  of the wire  2  upon connecting said joining section  18  with the contact opening  7  of the contact portion  5  of the terminal  3 . The edge  28  surrounding the entrance surface  9  at the upper side  10  of the contact portion  5  functions, upon pressing the wire  2  in the insertion direction I against the terminal  3 , as a blade that removes the insulation coating  17  in the joining section  18  so that only the lead  16  of the joining section  18  is pressed into the contact opening  7 . 
     In embodiments having a wire  2  that is provided with an insulating coating  17  in the connecting portion  8 , a terminal element  3  having a contact opening that is provided with an undercut  14 , such as the cavities  15  shown in  FIG. 5A , has the additional benefit of keeping the insulation at the upper side  10  of the terminal  3  connoted with the cutted insulation at the lower side  12 . This avoids pollution in the deformation or pressing tool due to release of the cut insulation into the tool. Further, the insulation remains for the wire  2  on both sides  10  and  12  of the terminal element  3  even in the joining section  18 , where the electrical contact is made between the joining section  18  and the contact opening  7 . 
       FIGS. 7A and 7B  show a fifth embodiment of a terminal assembly  1 , wherein the pre-assembled state is shown in  FIG. 7A  and  FIG. 7B  depicts the assembled state. 
     The terminal element  3  of the fifth embodiment is principally identical to the terminal element  3  of the first embodiment. Furthermore, the wire  2 ″ of the fifth embodiment principally corresponds to the wire  2  of the first embodiment, wherein insulating coating  17  is removed in the connecting portion  8  so that a blank lead  16  is exposed to the outside. 
     In contrast to the wire  2  of the first embodiment, the wire  2 ″ of the fifth embodiment is a stranded wire that is composed of a bundle of smaller wires making up the conductor. 
       FIG. 8  is a schematic representation of a cross-sectional view in the width direction w at a position corresponding to the sectional line A′-A′ of  FIG. 2 , through the contact opening  7  of a terminal assembly  1  in the assembled state. As can be seen in  FIG. 8 , the contact opening  7  in the contact portion  5  of the terminal  3  differs from the contact opening  7  of the previous embodiments in that it is not designed as a through-hole  7 ′. Rather, the contact opening  7  of the embodiment shown in  FIG. 8  is designed as a contact groove or a contact channel  7 ′″ that can be only entered via the entrance surface  9 , exposed at the upper side  10  of the contact portion  5 . The shape of the entrance surface  9  may be similar to the shape of the entrance  9  in the previous embodiments and can be designed elongated. 
     Starting from the entrance surface  9 , the width w of the contact channel  7 ′″ from one lateral side  13  to the other lateral side  13 , increases up to the bottom  29  of the channel  7 ′. That is, the channel  7 ′″ principally has a shape of a dovetail, as can be seen in  FIG. 8 . The lateral sides  13  of the contact channel  7 ′″ are inclined with respect to the plane defined by the insertion direction I and the longitudinal direction L. Upon filling up the contact channel  7 ′″ with the joining section  18  of the wire  2 , the undercut  14  formed by the inclined lateral walls  13  forms a form-fit connection with the joining section  18  securing the part of the joining section  18  that is located in the contact channel  7 ′″ against removal out of the channel  7 ′″ against the insertion direction I. 
     Furthermore, the stopper  20  on the upper side  10  of the contact portion  5  that overlayers the entrance surface  9  is formed with a curved surface having, in the cross-sectional view, the form of a rivet head, rather than a flat, plate-like shape as in the embodiment of  FIG. 1 . 
     Finally, in  FIGS. 9 ,  10 A and  10 B, a seventh embodiment of the terminal assembly is shown. The wire  2  of the seventh embodiment is generally the same as the wire  2  used in the first embodiment of  FIGS. 1 to 3 , namely a solid wire  2  having an insulating coating  17  that is removed in the connecting portion  8 , where the conductor  16  is exposed to the outside. 
     The terminal element  3  in the seventh embodiment is a printed circuit board  30  having arranged on contact side  31  thereof, a series of spaced apart contact openings  7 . As can be seen, for example, in  FIG. 10B , the contact opening  7  of the PCB  30  is designed as contact channel  7 ′. Contrary to the contact channel  7 ′″ of the sixth embodiment, however, the contact channels  7  of the seventh embodiment have the constant width w from the surface entrance  9  up to the bottom  28 . 
     Upon contacting the connecting portion  8  of the wire  2  to the contact opening  7  of the PCB  30 , the joining section  18  is pressed into the contact opening  7  forming a force-fit connection with the contact opening  7 . The joining section  18  is filling up the complete channel  7  and the excess portion of the joining section  18  that remains outside the opening  7  is flattened into a stopper  20 , whose shape principally corresponds to the stopper  20  located at the upper side  10  of the first embodiment shown in  FIG. 1 .