Method for connecting an electrical conductor to a printed circuit board

Abstract

The invention relates to a method for connecting an electrical conductor (5) to a printed circuit board (2), the method comprising the following steps: providing an electrical conductor (5), providing a printed circuit board (2) with at least one through-hole (3, 3'), wherein the through-hole (3, 3') has a lining (32) of electrically conductive material on its inside, providing at least one hollow body (4) with a lateral surface (41) and two opposing end faces (42, 43), wherein the hollow body (4) is closed at one of its end faces (42) and open at the other end face (43), inserting the hollow body (4) into the through-hole (3, 3') of the printed circuit board (2), wherein the hollow body (4) is mechanically connected to the printed circuit board (2) and the lateral surface (41) of the hollow body (4) is in electrically conductive contact with the lining (32) of the through-hole (3, 3') of the printed circuit board (2). occursand positioning the printed circuit board (2) on the electrical conductor (5), wherein the orientation of the hollow body (4) in the printed circuit board (2) is such that, after positioning the printed circuit board (2) on the electrical conductor (5), material of the hollow body (4) is in contact with the electrical conductor (5) at the closed end face (42) of the hollow body (4), forming a contact surface (6), welding the hollow body (4) to the electrical conductor (5) at the contact surface (6), wherein the energy required for the welding process is supplied from the direction of the side of the printed circuit board (2) facing away from the electrical conductor (5) through the hollow body (4) to the contact surface (6).

Description

[0001] The invention relates to methods for the combined mechanical and electrical connection of an electrical conductor, in particular a resistor arrangement, with a printed circuit board.

[0002] In many applications, it is necessary to establish a mechanically and simultaneously electrically conductive connection between an electrical conductor and a printed circuit board. One example is current measurement in electronic circuits. For this purpose, measuring resistors are often used, connected in series with the component being monitored. The current is then determined according to Ohm's law from the voltage drop across the measuring resistor, also known as the shunt resistor. The resistance value is assumed to be known. Accurate and reliable current measurement is particularly important, for example, in the battery management system of an electric or hybrid vehicle.

[0003] A resistor assembly used as a shunt resistor for measuring current comprises at least one resistive element and two terminals for connecting the resistor assembly to a circuit. The voltage drop across a resistive element can be measured, for example, via contact pins, wires, or similar elements, which are usually arranged on both sides of the resistive element on the terminals. Such contact pins or wires can be soldered, pressed in, or welded onto the terminals of the resistor assembly. A resistor assembly with pressed-in contact pins is known, for example, from US 10,163,553 B2. The voltage is detected and processed by measuring and evaluation electronics. Electronic components, which may be mounted on a printed circuit board, are provided for this purpose.The circuit board can be located in close proximity to the resistor array. Handling pin- or ferrite-shaped contact elements requires special equipment.

[0004] A resistor arrangement with a low-resistance current-measuring resistor is known from German patent application DE 10 2009 031 408 A1. This resistor arrangement has connection contacts for tapping the voltage. These contacts are formed by projections and threads in the plate-shaped sections that connect the resistor arrangement to the external circuit. The measuring leads for voltage measurement are connected to the connection contacts using cable lugs and fastening screws.

[0005] A current measuring device and an associated manufacturing process are known from German patent application DE 10 2022 109 709 A1. To create an electrical and mechanical connection between the current-sensing resistor and a conductive track, a conductive track, which is either applied to the underside of the printed circuit board (PCB) or embedded in the insulating material of the PCB, is exposed by drilling a blind hole into the insulating material of the PCB on the side facing away from the current-sensing resistor and, if necessary, also on the other side. The blind hole extends precisely to the conductive track. The conductive track is then welded to the current-sensing resistor in the exposed area. Care must be taken when drilling the blind hole to avoid damaging the conductive track. This is difficult because, for example, the generally tapered contour of a drill bit means that the bottom of the blind hole is not flat but funnel-shaped.The remaining thickness of the conductor track is therefore inhomogeneous and exhibits a point-like weak spot. Furthermore, there is a risk that chips and other particles will remain in the blind hole. The cleanliness requirements cannot be reliably met.

[0006] Publication JP 2013-128142 A discloses a method for electrically connecting the front and back sides of a printed circuit board (PCB) by means of a hollow body inserted into a through-hole in the PCB. The through-hole has no lining of electrically conductive material with which the outer surface of the hollow body could come into electrically conductive contact.

[0007] German patent application DE 10 2005 062 603 A1 discloses a gas sensor in which a sleeve-shaped contact shoe serves to establish an electrical connection between the conductor track of a sensor element and an electrical conductor. For this purpose, the contact shoe is inserted into the through-hole of a ceramic contact plate and into the through-hole of the sensor element. Neither hole has a lining of electrically conductive material on its inner surface. The closed end face of the contact shoe is welded to the conductor track.

[0008] Furthermore, EP 3 719 506 A1 discloses a current measuring assembly, in particular for measuring the battery current in a vehicle, comprising a shunt resistor, a printed circuit board, a first busbar leading to and fixed on the printed circuit board, wherein the first busbar provides at least one first shunt contact surface, and a second busbar leading to and fixed on the printed circuit board, wherein the second busbar provides at least one second shunt contact surface. A first measuring conductor is located on the printed circuit board in association with the first busbar, and a second measuring conductor is located in association with the second busbar. The shunt resistor is soldered to the first busbar and the first measuring conductor in a first contact area and to the second busbar and the second measuring conductor in a second contact area.

[0009] German patent application DE 10 2022 214 047 A1 discloses a method for connecting an electrical conductor to a printed circuit board (PCB). A fusible joining material, in particular a solder, is positioned between the electrical conductor and the PCB. The solder is melted by means of a laser beam directed through a recess in the PCB. To prevent molten solder from flowing into the recess in the PCB, the recess can be sealed with material that is thinner than the PCB. The described method requires ensuring that the solder is in the correct position. Providing and precisely positioning the solder results in additional process-related effort.

[0010] The invention aims to eliminate the described disadvantages of known devices and manufacturing methods, i.e., to provide a method for connecting an electrical conductor to a printed circuit board that is simpler, more accurate, more robust, and more cost-effective than methods known from the prior art. In particular, the method should exhibit improvements in terms of effort and process reliability.

[0011] The invention is described with respect to a first method by the features of claim 1 and with respect to a second method by the features of claim 5. The further referenced claims relate to advantageous embodiments and further developments of the invention.

[0012] The invention includes a first method comprising the following steps: Provision of an electrical conductor: This preferably has at least one flat surface. Ideally, the electrical conductor is essentially strip- or cuboid-shaped. The electrical conductor can, in particular, be a resistor arrangement that can be used as a shunt resistor. In such a resistor arrangement, at least one resistor element made of a metallic material is located between two terminal elements made of a metallic material with high electrical conductivity. whose electrical conductivity is much lower than that of the connecting elements. The connecting elements serve to connect the resistor assembly to an external circuit. The specific electrical resistance of the resistive element material can be at least 10 times greater than that of the connecting element material. Conversely, the resistance temperature coefficient of the connecting element material is much larger, typically at least 50 times greater than that of the resistive element material. In particular, the magnitude of the resistance temperature coefficient of the material of the resistance element can be less than 5·10 -5 1 / K, while the resistance temperature coefficient of the material of the connection elements is approximately 4·10 -3The resistance can be 1 / K. The connection elements of the resistor arrangement can be made of copper, preferably a low-alloy copper alloy, aluminum, or preferably a low-alloy aluminum alloy, or comprise at least one of these materials. The resistive element can be made, in particular, of a copper alloy or an aluminum alloy commonly used as a resistive alloy. The connecting elements and the resistive element of a resistive arrangement are preferably each designed as plate- or strip-shaped elements and arranged planarly side by side in a row. The resistive element is mechanically and electrically connected on two opposite sides by a joint, in particular by a weld. Each element is electrically conductive and connected to a terminal element. Between the terminal elements, there can be two or more resistance elements, which can either be in direct electrical contact with each other or separated from each other by an intermediate element made of a material with high electrical conductivity.

[0013] Providing a printed circuit board with a thickness D and at least one through-hole (via) with a clear diameter. The cross-sectional area of ​​the through-hole is preferably circular. However, oval or polygonal cross-sectional areas are also conceivable. The through-hole has a lining of electrically conductive material, typically copper, on its inner surface. The printed circuit board preferably has several such through-holes.

[0014] Provide at least one hollow body made of electrically conductive and weldable material: The hollow body has a lateral surface and two opposing end faces. It is closed at one end and open at the other. The hollow body can thus be described as cup-shaped, pot-shaped, beaker-shaped, or as a hollow cylinder closed at one end. The hollow body can resemble a barrel open at one end. The outer dimensions of the hollow body are chosen so that it can be inserted into the through-hole of the printed circuit board.

[0015] The hollow body is inserted into the through-hole of the printed circuit board. A suitable device, such as a press-fit tool with a hold-down plate, can be used for this purpose. During insertion, the hollow body is mechanically connected to the printed circuit board by being fixed in the through-hole. Furthermore, the outer surface of the hollow body comes into electrically conductive contact with the lining of the through-hole of the printed circuit board as the hollow body is plastically deformed. This contact is preferably achieved by an interference fit.

[0016] The printed circuit board (PCB) is positioned on the electrical conductor, with one side of the PCB facing the ideally flat surface of the conductor. The opposite side of the PCB faces away from the conductor. The PCB is positioned so that the conductor is located within the projection of the through-hole in the PCB. The orientation of the hollow core within the PCB is such that, after the PCB is positioned on the conductor, the closed end of the core is in contact with the conductor, forming a contact surface. The open end of the core faces away from the conductor.

[0017] The hollow body is welded to the electrical conductor at the contact surface. The energy required for the welding process is supplied from the side of the circuit board facing away from the electrical conductor, through the hollow body and thus also through the through-hole to the contact surface. Laser welding and electron beam welding are suitable welding processes for this purpose. After welding, the hollow body forms a mechanical and electrically conductive connection between the electrical conductor and the conductive elements, especially conductor tracks, arranged on or in the circuit board.

[0018] The preceding description does not specify the order of the steps. The sequence can be chosen as appropriate. For example, the hollow core can be inserted into the printed circuit board (PCB) before the PCB is positioned on the electrical conductor. This sequence is advantageous when the same type of PCB is to be connected to different types of electrical conductors. Alternatively, it is also possible to position the PCB on the electrical conductor before inserting the hollow core. This sequence better ensures that the hollow core makes contact with the electrical conductor during insertion. The hollow core is preferably inserted from the side of the PCB facing away from the electrical conductor, towards the conductor.

[0019] The particular advantage of the proposed method lies in its speed and energy efficiency. These advantages stem directly from the elimination of soldering. Furthermore, the thermal stress on components associated with soldering is avoided. The method requires no solder and therefore no unnecessary additional element. This results in cost reduction and process acceleration. Welding processes also exhibit greater process stability than soldering, thus reducing the error rate. Welding ensures a permanent and reliable connection between the printed circuit board and the electrical conductor. Because the hollow body serving as the connecting element is inserted into the through-hole of the printed circuit board, its position relative to the board is fixed. Therefore, the proposed methods achieve high positional accuracy of the contact points.

[0020] The contact between the outer surface of the hollow body and the lining of the through-hole in the circuit board is achieved through plastic deformation of the hollow body. This allows a gas-tight connection to be achieved, even though only a force-fit connection exists.

[0021] Another advantage is the availability of a variety of materials for the hollow body. Factors such as thermal conductivity, mechanical strength, weldability, and corrosion resistance can be considered when selecting the material. This makes the process highly flexible.

[0022] If the electrical conductor is a resistor arrangement with terminal elements and at least one resistor element, the resistor arrangement can be contacted according to the described procedure either at the terminal elements, at the resistor element or both at the terminal elements and at the resistor element.

[0023] In one embodiment, the length of the hollow body, measured from its open end to its closed end, can be greater than the thickness of the printed circuit board. This allows the hollow body to extend beyond the printed circuit board, ensuring reliable mechanical contact with the electrical conductor, i.e., making contact with the conductor at a contact surface. The conditions for a secure weld are then particularly favorable. Furthermore, by appropriately selecting the length of the hollow body, a distance between the printed circuit board and the electrical conductor can be adjusted. This optimizes heat dissipation.

[0024] In a particular embodiment of this design, the surface of the electrical conductor can have at least one recess to serve as a positioning aid. The recess is preferably formed by embossing. The hollow body can engage with its protrusion in the recess, thereby defining the position of the circuit board relative to the electrical conductor. This further improves positioning accuracy and enables optimal adaptation to different circuit boards and component geometries.

[0025] Preferably, in this particular embodiment of the invention, the hollow body can have a tapered, particularly cylindrical or conical, shape at its closed end face, i.e., a reduction in its outer dimensions. This tapering ensures centering of the hollow body. This guarantees precise alignment of the components during the welding process and results in a homogeneous joint between them.

[0026] The invention further includes a second method comprising the following steps: Providing an electrical conductor: This preferably has at least one flat surface. Ideally, the electrical conductor is essentially strip- or cuboid-shaped. The electrical conductor can, in particular, be a resistor arrangement that can be used as a shunt resistor and which is described in more detail above in connection with the first method.

[0027] Providing a printed circuit board with a thickness D and at least one through-hole (via) with a clear diameter. The cross-sectional area of ​​the through-hole is preferably circular. However, oval or polygonal cross-sectional areas are also conceivable. The through-hole has a lining of electrically conductive material, typically copper, on its inner surface. The printed circuit board preferably has several such through-holes.

[0028] Provide at least one hollow body made of electrically conductive and weldable material: The hollow body has a lateral surface and two opposing end faces. It is closed at one end and open at the other. The hollow body can thus be described as cup-shaped, pot-shaped, beaker-shaped, or as a hollow cylinder closed at one end. The hollow body can resemble a barrel open at one end. The outer dimensions of the hollow body are chosen so that it can be inserted into the through-hole of the printed circuit board. The hollow body tapers at its closed end face. The length of the hollow body, measured from its open end face to its closed end face, is greater than the thickness of the printed circuit board.

[0029] The hollow body is inserted into the through-hole of the printed circuit board, as described above in connection with the first method.

[0030] The printed circuit board (PCB) is positioned on the electrical conductor, with one side of the PCB facing the ideally flat surface of the conductor. The opposite side of the PCB faces away from the conductor. The PCB is positioned so that the conductor is located in the projection of the through-hole in the PCB. The orientation of the hollow core within the PCB is such that, after the PCB is positioned on the conductor, material from the hollow core is in contact with the conductor at its closed end face, forming a contact surface. The surface of the conductor has at least one depression to aid positioning, and the hollow core engages with this depression at its tapered end.In this way, the position of the circuit board relative to the electrical conductor is determined by centering the hollow body. The open end face of the hollow body faces away from the electrical conductor.

[0031] The hollow body is welded to the electrical conductor at the contact surface, as described above in connection with the first method.

[0032] Regarding further technical features and advantages of the second method, explicit reference is made hereto to the explanations in connection with the first method.

[0033] In a further embodiment of both the first and second methods, the hollow body can have a plastically deformable projection at its open end face, the lateral extent of which is greater than the clear diameter of the through-hole in the printed circuit board. The hollow body is inserted by applying force to the projection. In this embodiment, the hollow body resembles a hat whose brim is larger than the opening diameter of the through-hole. When the hollow body is inserted into the through-hole, the projection comes into contact with the side of the printed circuit board facing away from the electrical conductor. The plastic deformability of the projection allows the hollow body to be pressed further into the through-hole until reliable contact with the electrical conductor is achieved.The plastically deformable overhang thus serves to compensate for dimensional tolerances of the individual components without placing excessive stress on the circuit board.

[0034] In a further embodiment of both the first and second methods, the hollow body can have an elastic, in particular resilient, projection at its open end face, the lateral extent of which is greater than the clear diameter of the through-hole in the printed circuit board. The hollow body is inserted by applying force to the projection. As in the embodiment described above, in this embodiment the hollow body resembles a hat whose brim is larger than the opening diameter of the through-hole. After the hollow body is inserted into the through-hole, the projection rests on the side of the printed circuit board facing away from the electrical conductor. Due to its elasticity, the projection exerts a spring force on the printed circuit board or on the hollow body. This holding force is advantageous for the welding process.The elasticity of the cantilever also offers advantages during operation: it can compensate for differing thermal expansion of the individual components and dampen vibrations occurring during operation. It proves particularly advantageous if the cantilever is deformable both plastically and elastically.

[0035] When using a hollow body with a plastically deformable or elastic projection as described above, it can be advantageous to establish a connection between the hollow body and the printed circuit board (PCB) after the hollow body has been inserted into the PCB. This connection is made by soldering the projection of the hollow body to suitable contact surfaces on the PCB surface, for example, to a conductor track. This is preferably done using a reflow soldering process. Such a connection provides an additional electrical and mechanical connection. This additional step is particularly advantageous if the sequence of steps in the process is chosen such that the hollow body is inserted into the PCB before the PCB is positioned on the electrical conductor.

[0036] In a further embodiment of both the first and second methods, the hollow body can have a greater wall thickness at its closed end face than at its outer surface. This provides more material for the weld connection with the electrical conductor.

[0037] In a further embodiment of both the first and second methods, the shape of the hollow body can be selected such that its outer surface rests against several separate contact zones on the inside of the through-hole. For example, a hollow body with an oval or polygonal cross-sectional shape can be inserted into a circular hole, so that several defined contact surfaces are provided by the distal areas of the hollow body's outer shape. The smaller the contact surfaces, the greater the locally acting pressure for a given contact force.

[0038] In a further embodiment of both the first and second methods, the outer surface of the hollow body can be additionally bonded to the lining of the through-hole, preferably during welding. This can be achieved by a suitable beam geometry and control of the energy source used in the welding process. The bonded connection improves the mechanical and electrical connection between the hollow body and the lining of the through-hole in the printed circuit board.

[0039] In a further embodiment of both the first and second methods, the outer surface of the hollow body can be coated with a contact-enhancing and / or corrosion-protective layer. A material can be selected for this layer that is compatible with the other components and possesses the desired functional properties. For example, a tin layer facilitates a metallurgical bond between the hollow body and the lining. A nickel layer offers very good corrosion protection.

[0040] Exemplary embodiments of the invention are explained in more detail with reference to the schematic drawings.

[0041] It shows: Fig. 1 a hollow body, Fig. 2 a view of a device produced by the method, Fig. 3 a detailed view of Fig. 2 in cross-section, Fig. 4 a resistor arrangement and a printed circuit board before their connection, Fig. 5. the insertion of hollow bodies into the printed circuit board, Fig. 6 a resistor arrangement and a printed circuit board with inserted hollow bodies, Fig. 7. Welding the hollow bodies to the resistance arrangement, Fig. 8 a resistor arrangement and a circuit board after their connection.

[0042] Corresponding parts are marked with the same reference symbols in all figures.

[0043] Fig. Figure 1 schematically shows a hollow body 4 for use in the method described above. The hollow body 4 comprises a substantially hollow cylindrical base body 40 with an open end face 43 and a closed end face 42. Between the two end faces 42, 43, the hollow cylindrical base body 40 is bounded externally by a lateral surface 41. At the open end face 43, the hollow cylindrical base body 40 transitions into a projection 45, 46, which is plastically and / or elastically deformable. At the closed end face 42, the hollow body 4 has a taper 44, forming a shoulder. The outer diameter of the hollow body 4 is reduced in the region of the taper 44. The length of the hollow body 4 from its open end face 43 to its closed end face 42 is referred to as the length L.

[0044] Fig. Figure 2 shows an oblique view of a device 1 for measuring the magnitude of an electric current. The device 1 comprises an electrical conductor 5, which in the illustrated case is configured as a resistor assembly (shunt). The resistor assembly 5 has two strip- or plate-shaped terminal elements 52, 52', between which a plate-shaped resistor element 51 is arranged. As described above, the terminal elements 52, 52' can be made of a metallic material with high electrical conductivity, for example, copper or aluminum. The resistor element 51 can be made of a metallic material whose electrical conductivity is lower than that of the material of the terminal elements 52, 52'. For example, the resistor element 51 can be made of an alloy whose specific electrical resistance exhibits low temperature dependence, i.e., a small resistance-temperature coefficient.The resistive element 51 is mechanically and electrically connected, preferably by a material bond, and particularly preferably by a weld, to a terminal element 52, 52' on each of its two longitudinal sides. The terminal elements 52, 52' each have a bore 55, 55' at their end furthest from the resistive element 51, by means of which the resistive arrangement 5 can be connected to an external circuit (not shown). The thickness of the resistive element 51 can be less than the thickness of the two terminal elements 52, 52', as in the illustrated case.

[0045] In the area of ​​the resistor element 51, a printed circuit board 2 is positioned above the electrical conductor 5. The surface of the printed circuit board 2 is aligned parallel to the surface of the terminal elements 52, 52' and the resistor element 51, respectively, facing the printed circuit board 2. The printed circuit board 2 extends at both ends over a portion of the terminal elements 52, 52' of the resistor assembly 5, thus forming overlapping areas with the terminal elements 52, 52'. In these overlapping areas, the printed circuit board 2 maintains a distance Z from the electrical conductor 5. Through holes 3, 3' in the printed circuit board 2 are present in these overlapping areas.

[0046] On the surface of the circuit board 2 facing away from the resistor arrangement 5 are conductor tracks 21, 21' and an electronic component 7. The electronic component 7 can include measuring and evaluation units as well as interfaces. The conductor tracks 21, 21' connect the through holes 3, 3' to the electronic component 7.

[0047] In the through holes 3, 3' of the circuit board 2 there is each a hollow body 4 according to Fig. 1. The open end face 43 of each hollow body is located on the side of the circuit board 2 facing away from the resistor assembly 5. Each hollow body 4 has a projection 45, 46 on its open end face 43. The hollow bodies 4 each establish an electrical and mechanical connection between the resistor assembly 5 and the circuit board 2, so that the voltage drop across the resistor element 51 when current flows can be tapped and supplied to measuring and evaluation electronics, which are, for example, housed in the electronic component 7.

[0048] Fig. Figure 3 shows a section of the device according to Fig. 2 in cross-section. Shown is the area in which the circuit board 2 is mounted by means of a hollow body 4 according to Fig. 1 is connected to a terminal element 52 of the resistor arrangement 5. The circuit board 2 has a through-hole 3, on the inside of which a lining 32 made of electrically conductive material is attached. A hollow body 4 is located in the through-hole 3, which is mechanically and electrically connected to the lining 32 in the through-hole 3.

[0049] Near the resistor element 51, a recess 53 is provided in the terminal element 52. The length L of the hollow body 4 is greater than the thickness D of the circuit board 2, which is why the hollow body 4 projects into the recess 53 of the terminal element 52 with its closed end face 42, while the projection 45, 46 attached to the open end face 43 of the hollow body 4 rests on the surface of the circuit board 2. The recess 53 in the terminal element 52 is designed as a negative mold of the closed end face 42 of the hollow body 4. In the illustrated case, the shape and size of the recess 53 are adapted to the taper 44 on the closed end face 42 of the hollow body 4, so that only the reduced-diameter area of ​​the hollow body 4 is accommodated by the recess 53.However, it is also possible that the recess 53 has a step, so that the hollow body 4 can be received by the recess 53 not only in the area of ​​its taper 44, but also partially in the area of ​​its base body 40. The hollow body 4 is welded to the material of the connecting element 52 at a contact surface 6 on its closed end face 42.

[0050] In the Fig. In the case shown in Figure 3, the distance between the circuit board 2 and the connection element 52 is determined solely by the length and shape of the hollow body 4. It can be advantageous to additionally insert a spacer between the circuit board 2 and the resistor assembly 5. The spacer can be an elastic plate. It is also conceivable to design the spacer as an annular element that encloses the hollow body 4 in the area between the circuit board 2 and the resistor assembly 5.

[0051] Based on the characters Fig. 4 to Fig. Section 8 explains how the proposed method establishes the mechanical and electrical connection between the printed circuit board 2 and the electrical conductor 5, designed as a resistor assembly, by means of the hollow bodies 4. For the sake of clarity, the depiction of the previously described tapering 44 on the closed end face 42 of the hollow body 4, the lining 32 in the through-holes 3 of the printed circuit board 2, and the distance between the printed circuit board 2 and the connection elements 52, 52' of the resistor assembly 5 are omitted.

[0052] Fig. Figure 4 shows an electrical conductor 5 in the form of a related element. Fig. The resistor assembly 5 described in Figure 2 comprises two terminal elements 52, 52' and a resistor element 51 arranged between the terminal elements 52, 52'. A printed circuit board 2 is positioned on the resistor assembly 5, resting directly on the terminal elements 52, 52' in the illustrated case, i.e., without any gap. On the side of the resistor assembly 5 facing the printed circuit board 2, a recess 53, 53' is provided in each of the two terminal elements 52, 52' near the resistor element 51. The printed circuit board 2 has through holes 3, 3'. The printed circuit board 2 is positioned on the resistor assembly 5 such that the through holes 3, 3' are aligned with the recesses 53, 53' in the terminal elements 52, 52'. Two hollow bodies 4 are provided on the side of the printed circuit board 2 facing away from the resistor assembly 5. Details of the hollow bodies 4 are given above in connection with Fig. 1 explained. The hollow bodies 4 are oriented such that their closed end face 42 points towards the resistor arrangement 5 and their open end face 43 points away from the resistor arrangement 5.

[0053] Fig. Figure 5 shows the insertion of the hollow bodies 4 into the bores 3, 3' of the printed circuit board 2. For this purpose, a press-fit device is used, which includes a hold-down plate 8. The hold-down plate 8 has two through-holes 81, 81', the position of which corresponds to the position of the bores 3, 3' in the printed circuit board 2. By exerting force on the hollow bodies by means of the hold-down plate 8, they are pressed into the bores 3, 3' of the printed circuit board 2 and subsequently also into the recesses 53, 53' of the terminal elements 52, 52' of the resistor assembly 5.

[0054] Fig. Figure 6 shows the resistor assembly 5 and the circuit board 2 with inserted hollow bodies 4. The force exerted by the hold-down plate 8 continues, pressing the closed end face 42 of each hollow body 4 against the respective counter surface in the recess 53, 53'. Different lengths of the hollow bodies 4 and / or different depths of the recesses 53, 53' can be compensated for by the plastically deformable projections 45 on the open end face 43 of the hollow body. Thus, each hollow body 4 is in mechanical contact with one of the connecting elements 52, 52' at a contact surface 6. Due to the force acting on the hollow body 4, it expands in the through-hole 3, 3' perpendicular to the direction of the force.This creates a firm mechanical contact and consequently also an electrical contact between the outer surface 41 of the hollow body 4 and the lining 32 on the inside of the through bore 3, 3' in the form of an interference fit.

[0055] In Fig. Figure 7 shows the welding of the hollow bodies 4 to the connecting elements 52, 52' of the resistor assembly 5. For each hollow body 4, a laser beam 61, symbolized by a dashed arrow, is directed through the through-hole 81 of the hold-down plate 8 and the open end face 43 of the hollow body 4 onto the inside of the closed end face 42 in the area of ​​the contact surface 6. The energy input welds the closed end face 42 of the hollow body 4 to the material of a connecting element 52, 52' at the contact surface 6. Preferably, the laser beam 61 is directed such that the material of the outer surface 41 of the hollow body 4 is also welded to the lining 32 on the inside of the bore 3. The hold-down plate 8 is removed only after the welding process is complete.

[0056] In Fig. Figure 8 shows the resistor assembly 5 and the printed circuit board 2 after removal of the retaining plate 8. The hollow bodies 4 provide a mechanical connection and simultaneously an electrically conductive contact between the resistor assembly 5 and the printed circuit board 2.

[0057] Based on the Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6, Fig. 7 to Fig.Section 8 describes the proposed method for the case where the resistor assembly 5 is contacted at the two terminal elements 52, 52' of the resistor assembly 5. However, it is also possible to use the method to contact the resistor assembly 5 at the resistor element 51. The length of the hollow bodies 4 must then be adjusted to the geometric conditions. In particular, it may be necessary to compensate for an offset between the terminal elements 52, 52' and the resistor element 51 resulting from the different thicknesses of these components.

[0058] The method was explained above using the example of connecting a printed circuit board to a resistor array, which can be used for current measurement, for example, in a motor vehicle. However, the method can also be used in other applications. Reference symbol list 1 Device 2 circuit boards 21 conductor track 3.3' through hole 32 Lining 4 hollow bodies 40 basic shapes 41 Surface area 42 closed front 43 open front 44 Rejuvenation 45 plastic cantilever 46 elastic cantilever 5 electrical conductors, resistor arrangement 51 Resistance element 52, 52' Connection element 53, 53' Deepening 55, 55' bore 6 Contact area 61 Laser beam 7 electronic component 8 Hold-down plate 81 Radiation aperture Thickness Length L Z distance

Claims

[1] Method for connecting an electrical conductor (5) to a printed circuit board (2), the method comprising the following steps: Providing the electrical conductor (5), Providing the printed circuit board (2) with a thickness (D) and with at least one through hole (3, 3') with a clear width, wherein the through hole (3, 3') has on its inside a lining (32) of electrically conductive material, Providing at least one hollow body (4) made of electrically conductive and weldable material, wherein the hollow body (4) has a lateral surface (41) and two opposing end faces (42, 43) and wherein the hollow body (4) is closed at one of its end faces (42) and open at the other end face (43), Inserting the hollow body (4) into the through-hole (3, 3') of the printed circuit board (2), wherein the hollow body (4) is mechanically connected to the printed circuit board (2) and the outer surface (41) of the hollow body (4) comes into electrically conductive contact with the lining (32) of the through-hole (3, 3') of the printed circuit board (2) by plastically deforming the hollow body (4), and positioning the printed circuit board (2) on the electrical conductor (5), whereby one side of the printed circuit board (2) is facing away from the electrical conductor (5), wherein the orientation of the hollow body (4) in the printed circuit board (2) is such that, after positioning the printed circuit board (2) on the electrical conductor (5), material of the hollow body (4) is in contact with the electrical conductor (5) at the closed end face (42) of the hollow body (4), forming a contact surface (6). Welding the hollow body (4) to the electrical conductor (5) at the contact surface (6), wherein the energy required for the welding process is supplied from the direction of the side of the circuit board (2) facing away from the electrical conductor (5) through the hollow body (4) to the contact surface (6). [2] Method according to claim 1, characterized by , that the length (L) of the hollow body (4), measured from its open end face (43) to its closed end face (42), is greater than the thickness (D) of the circuit board (2). [3] Method according to claim 2, characterized by , that the surface of the electrical conductor (5) has at least one recess (53, 53') as a positioning aid and that the hollow body (4) engages in the recess (53, 53') and thus determines the position of the circuit board (2) in relation to the electrical conductor (5). [4] Method according to claim 3, characterized by, that the hollow body (4) has a tapering (44) at its closed end face (42) which causes the hollow body (4) to be centered. [5] Method for connecting an electrical conductor (5) to a printed circuit board (2), the method comprising the following steps: Providing the electrical conductor (5), Providing the printed circuit board (2) with a thickness (D) and with at least one through hole (3, 3') with a clear width, wherein the through hole (3, 3') has on its inside a lining (32) of electrically conductive material, Providing at least one hollow body (4) made of electrically conductive and weldable material, wherein the hollow body (4) has a lateral surface (41) and two opposing end faces (42, 43), wherein the hollow body (4) is closed at one of its end faces (42) and open at the other end face (43) and has a taper (44) at its closed end face (42), wherein the length (L) of the hollow body (4), measured from its open end face (43) to its closed end face (42), is greater than the thickness (D) of the circuit board (2), Inserting the hollow body (4) into the through-hole (3, 3') of the printed circuit board (2), wherein the hollow body (4) is mechanically connected to the printed circuit board (2) and the outer surface (41) of the hollow body (4) comes into electrically conductive contact with the lining (32) of the through-hole (3, 3') of the printed circuit board (2), and positioning the printed circuit board (2) on the electrical conductor (5), whereby one side of the printed circuit board (2) is facing away from the electrical conductor (5), wherein the orientation of the hollow body (4) in the printed circuit board (2) is such that, after positioning the printed circuit board (2) on the electrical conductor (5), material of the hollow body (4) is in contact with the electrical conductor (5) at the closed end face (42) of the hollow body (4), forming a contact surface (6), wherein the surface of the electrical conductor (5) has at least one depression (53,53') as a positioning aid and wherein the hollow body (4) engages with its tapered section (44) in the recess (53, 53') and thus determines the position of the circuit board (2) in relation to the electrical conductor (5) by centering the hollow body (4), Welding the hollow body (4) to the electrical conductor (5) at the contact surface (6), wherein the energy required for the welding process is supplied from the direction of the side of the circuit board (2) facing away from the electrical conductor (5) through the hollow body (4) to the contact surface (6). [6] Method according to any one of claims 1 to 5, characterized by , that the hollow body (4) has a plastically deformable projection (45) at its open end face (43), the lateral extent of which is greater than the clear width of the through-hole (3. 3') of the circuit board (2), and that the insertion of the hollow body (4) takes place under force acting on the projection (45). [7] Method according to any one of claims 1 to 6, characterized by , that the hollow body (4) has an elastic projection (46) at its open end face (43), the lateral extent of which is greater than the clear width of the through-hole (3, 3') of the circuit board (2), and that the insertion of the hollow body (4) takes place under force acting on the projection (46). [8] Method according to any of the foregoing claims, characterized by , that the hollow body (4) has a greater wall thickness at its closed end face (42) than at its lateral surface (41). [9] Method according to any of the foregoing claims, characterized by , that the shape of the hollow body (4) is chosen such that the lateral surface (41) of the hollow body (4) rests on several separate contact zones on the inside of the through-hole (3, 3'). [10] Method according to any of the preceding claims, characterized by, that the outer surface (41) of the hollow body (4) is additionally bonded to the lining (32) of the through-hole (3, 3'). [11] Method according to any of the foregoing claims, characterized by , that the outer surface (41) of the hollow body (4) is coated with a contact-enhancing and / or corrosion-protecting layer.

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