Abstract:
The invention relates to a contact element ( 10 ) with a plug side ( 14 ) and a solder side ( 16 ) to be contacted with a circuit board or a carrier substrate. The contact element ( 10 ) is produced from an Al/Cu material composite ( 36 ), the Cu portion ( 42 ) of which forms the plug side ( 14 ) and the Al portion ( 44 ) of which forms the solder side ( 16 ) of the contact element ( 10 ).

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The German patent application DE 10 2004 030 388 A1 relates to an article with a coating of electrically conductive polymer and a method for the production thereof. According to this solution, circuit boards are provided with a copper layer in which electrical conductors are produced by means of structuring. A layer of electrically conductive polymer is applied to the copper layer in order to maintain the solderability thereof and to protect the same from oxidation. The copper or copper alloy layer is located between an electrically conductive basis layer and a layer containing the conductive polymer. 
         [0002]    The German patent application DE 10 2009 001 461 A1 relates to a method for producing an electronic assembly. The assembly is formed by two microelectronic components which are connected to one another. The connection is established by means of a plurality of dielectric components which comprise respectively at least one conductor track. The conductor track is produced by introducing a continuous cavity into the dielectric component and by subsequently filling said cavity with an electrically conductive material. The filling material can relate to an electrically conductive polymer. 
         [0003]    A THT manufacturing process (through-hole technology) is used for the purpose of electrical contacting. According to this manufacturing process, the connecting wires of wired components as well as male multipoint connecters are inserted through openings in the circuit board. The components to be contacted can relate to capacitors, transistors, resistors, integrated circuits (ICs) and the like. The listed components require different preparations in which the connecting wires, which are also denoted as connecting pins, are bent and cut so that said connecting wires fit into a bore pattern or opening pattern predefined by the circuit board. After preparing the components and equipping the circuit board with the same, said components are soldered. The soldered connection occurs as a rule on the bottom side of the circuit board. To this end, the wave soldering method or the flow soldering method can be used. In the case of wave soldering, the circuit board is passed with the bottom side thereof over a solder wave which, when making contact with the bottom side of the component, produces the soldered connection. A special way of carrying out said method is known as selective soldering. In this case, the entire assembly is not soldered but only a small portion thereof—partially only a single component—by means of a miniature wave. The selective soldering method is frequently the only possible soldering method if wired components have to be soldered. 
         [0004]    In particular in applications in the automotive field, the soldered joints produced by means of the THT manufacturing method have to be able to withstand a large number of temperature changes without the function of the soldered joint being significantly affected on the one hand with regard to the electrical conductivity thereof and on the other hand with regard to the mechanical stability thereof. Thermomechanically induced stresses occur however in the soldered joints due to the temperature changes, which stresses can lead to damage to the soldered joints. Said stresses are determined by geometrical factors with respect to all components and furthermore are dependent on transient thermal conditions (temperature/time profiles). 
         [0005]    As a result of the development trend towards intramodular design of control devices, individual modules and not only individual components are connected by THT soldering technology to the actual circuit board. In particular for applications in the automotive sector, THT soldered joints have to withstand many temperature changes without the function of the soldered joint being significantly compromised with regard to the conductivity thereof and to the mechanical stability thereof. Due to the temperature changes, thermomechanically induced stresses result in the soldered joints, which can lead to premature damage to the soldered joints. The stresses are determined by geometrical factors of all components and are dependent on transient thermal stresses. A majority of components that are soldered by means of applications of the THT method relates to connector strips that are soldered on one side and are preferably used in electronic control devices. Contact pins being used, which are also denoted simply as pins, are manufactured from bronze and for the most part punched out of bands. In so doing, it is however absolutely necessary for the material on the plug side to correspond to the material classes of the automobile manufacturer required to date. In contrast, the materials on the solder side can be freely defined, i.e. metals or aluminum-based metal alloys can, for example, be used here which can either be directly soldered or can be made solderable by means of a corresponding coating, for example a NiSn coating. 
       SUMMARY OF THE INVENTION 
       [0006]    According to the invention, it is proposed to use an aluminum-copper composite in order to improve the thermal shock resistance of the contact pins to be soldered. Said aluminum-copper composite relates, for example, to an extruded aluminum profile which comprises a Cu portion and an Al portion in a common plane. The Cu portion and the Al portion can on the one hand lie in a common plane that runs horizontally. Said portions can however also be disposed in planes which are different from one another and extend horizontally. Both embodiment options of the extruded aluminum profile have in common that the Cu portion and the Al portion are connected to one another within a transition region, for example by an arrow-shaped end of one of the two portions protruding into a complementarily configured receptacle of the respective other of the two portions. The portions are joined to one another in a materially bonded manner within the transition region. In accordance with the solution proposed according to the invention, the contact element is manufactured from an Al/Cu material composite, wherein the Cu portion of which forms the plug side of the contact element and the Al portion of the Al/Cu material composite forms the solder side of said contact element. 
         [0007]    The contact elements, whether said elements comprise a common plane in relation to solder side and plug side or whether the solder side and the plug side are designed so as to lie in different planes, are preferably punched out of the Al/Cu material composite. This offers the advantage of a very efficient large-scale manufacturability and a very high utilization of the Al/Cu material composite with regard to accruing residual material. 
         [0008]    The contact element proposed according to the invention and punched out of the Al/Cu material composite has a plug-side geometry in the form of plug pins on the plug side. The plug pins form a material composite and can be connected to one another by individual webs. On the solder side, i.e. of the aluminum portion of the extruded aluminum profile, a solder-side geometry can be formed which, for example, can be configured in the form of a contact composite comprising individual contact wires. In so doing, the individual contact wires of the contact composite can have the same length or also lengths which in each case are different from one another. 
         [0009]    In an advantageous manner, it is possible by means of the contact element proposed according to the invention that on the one hand the plug side of the contact element continues to be formed from a copper alloy; whereas an aluminum alloy is used on the solder side, said alloy having less rigidity with regard to the modulus of elasticity and a greater coefficient of thermal expansion. In the case of a thermally induced stress on the plug pin in the form of bending, twisting or tensile load, a portion of this mechanical stress, which can result in damage to the contact element, is absorbed by the more flexible aluminum material which is located on the circuit board side or on the carrier substrate. The contact element, taken as a whole, has a longer damage-free time and thus a longer service life. 
         [0010]    If the contact element is made from an Al/Cu material composite, the Cu portion of which and the Al portion of which run in a common horizontal plane, a particularly efficient production in terms of manufacturing technology is possible for the large-scale production of the contact element proposed according to the invention. On the other hand, the prefabrication of the extruded material of the Al/Cu material composite also offers the possibility of accommodating different installation geometries of the contact element. Thus, the Cu portion and the Al portion can, for example, not only be designed to lie in a common plane; but in fact the option exists for the two said portions to also run in horizontal planes that are different from one another. 
         [0011]    The two portions, i.e. the Cu portion and the Al portion, of the Al/Cu material composite of the extruded profile are connected to one another within a transition region, i.e. merge into one another. The transition region is provided with regard to the mechanical stability thereof in such a way that said region can withstand the mechanical stresses which impact the extruded profile during a punching process or the like. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The invention is described below in more detail with the aid of the drawings. 
           [0013]    In the drawings: 
           [0014]      FIG. 1  shows a Al/Cu material composite, the Cu portion of which and the Al portion of which lie in a common horizontal plane, 
           [0015]      FIG. 2  shows a contact element having a plug-side and a solder-side geometry; 
           [0016]      FIG. 3  shows a cross section through a Al/Cu material composite in which the Al portion and the Cu portion lie in horizontal planes that are different from one another. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    An Al/Cu material composite can be seen in the depiction pursuant to  FIG. 1  in a perspective top view, the Cu portion of which and the Al portion of which run in a common horizontal plane. 
         [0018]    From the depiction pursuant to  FIG. 1 , it follows that an extruded profile  40  of an Al/Cu material composite  36  comprises a Cu portion  42  and an Al portion. Said portions  42  or  44  constitute aluminum alloys or Cu alloys which are connected to one another within a transition region  38 . From the depiction pursuant to  FIG. 1 , it can be seen that an arrow-shaped end  42  of the Cu portion  42  protrudes into a complementarily configured receptacle  54  of the Al portion  44  in a horizontal plane in the transition region  38  between the Cu portion  42  and the Al portion  44 . Within the transition region  38 , the two portions, i.e. the Cu portion  42  and the Al-portion  44 , are connected to one another in a materially bonded and force-fit manner; thus enabling a Al/Cu material composite  36  consisting of said sections  42 ,  44  to result which can even withstand mechanical stresses which impact the Al/Cu material composite  35  during a punching process of the contact element  10  proposed according to the invention. 
         [0019]    It is shown in the depiction pursuant to  FIG. 1  that the Cu portion  42  constitutes a plug side  14  of a contact element  10  while a solder side  16  of the contact element  10  is formed by the Al portion  44  of the Al/Cu material composite  36 . Instead of the geometry depicted in  FIG. 1  with regard to the transition region  30  comprising an arrow-shaped end  52  and a complementarily configured receptacle  54 , other transition geometries can also be formed in the transition region  38  between the Cu portion  42  and the Al portion  44  of the Al/Cu material composite  36 . 
         [0020]    A top view of a contact element proposed according to the invention from the Al/Cu material composite pursuant to  FIG. 1  can be seen in the depiction pursuant to  FIG. 2 . 
         [0021]    It follows from the top view pursuant to  FIG. 2  that the contact element  10  comprises a row of plug pins  12  on the plug side  14  thereof that is formed by the Cu portion  42 . The individual plug pins  12  on the plug side  14  are connected to one another by means of webs  26  and form a plug-side geometry  32 . The plug-side geometry  32  is provided by the Cu portion  42  of the extruded profile  40  that is designed as an Al/Cu material composite and was previously mentioned in connection with  FIG. 1 . The webs  26  are provided with individual openings  30 . 
         [0022]    Pursuant to the top view in  FIG. 2 , the contact element  10  furthermore comprises the solder side  16 , which is provided by the Al portion  44  of the Al/Cu material composite  36 . It can be seen from the depiction pursuant to  FIG. 2  that contact elements  10  have individual contact wires  56  in this region, i.e. on the solder side  16 . The individual contact wires  56  comprise a soldering tip  20 , wherein the individual contact wires  56  can be designed having different lengths. It can be seen in the depiction pursuant to  FIG. 2  that the individual contact wires  56  in said depiction pursuant to  FIG. 2  can have either a first length, a second length  22  or a third length  24 . 
         [0023]    Besides the constitution of the contact wires  56  in the different lengths  20 ,  22 , and  24  as depicted in  FIG. 2 , the contact wires  56  could also have a uniform length that is independent of the first length  20 , the second length  22  and the third length  24 . 
         [0024]    The contact wires  56  form a contact composite  18  and constitute a solder-side geometry  34  of the contact element  10 . 
         [0025]    Taking recourse to  FIG. 1 , the contact wires  56  of the solder-side geometry  34  are provided by the Al portion  44  of the Al/Cu material composite  36 , whereas the plug pins  12  according to the plug-side geometry  32  are constituted by the individual plug pins  12 —embodied here in a uniform length. 
         [0026]    It can be seen in the depiction pursuant to  FIG. 2  that the soldering tips  28  of the contact wires  56 , constituting the solder-side geometry, consist of aluminum. The contact wires  56  of the contact composite  18  are namely configured in the Al portion  44  of the Al/Cu material composite  36  and have less rigidity with regard to the modulus of elasticity and furthermore a greater coefficient of thermal expansion. Within the plug side  14 , the plug pins are still made from a Cu alloy which forms the Cu portion of the Al/Cu material composite  36 . When thermally induced stresses on the plug pins  12  occur in the region of the plug side  14  of the contact element  10 , for example as a result of bending, twisting or tensile load and the like, a portion of the harmful stresses are absorbed by aluminum material of the solder side  16  which has substantially more flexible properties and is formed by the Al portion  44  of the Al/Cu material composite. As a result, a longer damage-free time and consequently a longer service life of the contact element  10  proposed according to the invention is to be expected. 
         [0027]    A possible embodiment variant of the Al/Cu material composite  36  pursuant to the depiction in  FIG. 1  can be seen in the depiction pursuant to  FIG. 2 . On the plug side  14  and the solder side  16  of the contact element  10 , other geometries can, of course, also be punched or produced in another manner from the Al/Cu material composite  36  depicted in  FIG. 1 , said geometries deviating from the geometry of the contact element  10  according to the depiction in  FIG. 2 . 
         [0028]      FIG. 3  shows a further possible embodiment variant of the Al/Cu material composite pursuant to the depiction in  FIG. 1 . 
         [0029]    As an alternative to the depiction pursuant to  FIG. 1  in which the Al/Cu material composite  36  runs in a common horizontal plane  46 , the Cu portion  42  of the Al/Cu material composite  36  as well as the Al portion  44  of the Al/Cu material composite  36  can also have the geometry depicted in  FIG. 3 . This geometry differs from the geometry of the Al/Cu material composite  36  depicted in  FIG. 1 , which runs in a common horizontal plane  46 , by virtue of the fact that the Cu portion  42  extends in a first horizontal plane  48  and the Al portion  44  extends in a second horizontal plane  50  that is different from said first horizontal plane. The first horizontal plane  48  and the second horizontal plane  50  of the embodiment variant of the extruded profile  40  according to the depiction in  FIG. 3  show that the Cu portion  42  and the Al portion  44  of the extruded profile  40  can run in different horizontal planes  48  or  50  that are oriented offset to one another. This is dependent on the semi-finished product, i.e. on the extruded profile  40 , in which the contact elements  10  proposed according to the invention are punched out or can otherwise be generated. 
         [0030]    For the sake of completeness, it should be mentioned that, according to the embodiment variant of the extruded profile  40  pursuant to the depiction in  FIG. 3 , the transition region  38  between the Cu portion  42  and the Al-portion lies in the crank plane, i.e. in a vertical plane, in which a transition from the first horizontal plane  48  into the second horizontal plane  50  of the extruded profile  40  of the Al/Cu material composite  36  is present.