Circuit board

Abstract

Printed circuit board with an arrangement of busbars (50, 52, 54, 84, 86, 88, 90, 92), wherein the busbars (50, 52, 54, 84, 86, 88, 90, 92) are in electrical contact with the printed circuit board (14, 44), the busbars (50, 52, 54, 84, 86, 88, 90, 92) are arranged such that at least one current path (12, 42) is formed, adjacent busbars (50, 52, 54, 84, 86, 88, 90, 92) are directly connected to each other electrically via a connection in at least one current path (12, 42).

Description

[0001] The invention relates to a printed circuit board with an arrangement of busbars and a method for processing a printed circuit board. State of the art

[0002] A printed circuit board (PCB) is a carrier for electronic components. The board serves both as a mechanical mounting and as an electrical connection for the components. Printed circuit boards typically consist of an electrically insulating material with tracks made of an electrically conductive material in or on them. These tracks serve to electrically connect the components on the board.

[0003] In order to conduct high currents across printed circuit boards without excessive power loss, so-called busbars are often used. Busbars are separate copper rails that are brought into electrical contact with a printed circuit board. This contact can be achieved, for example, via a welded connection, press fit, or soldered connection.

[0004] It should be noted that so-called SMT busbars (SMT: surface mounted technology), which are connected directly to the circuit board in the so-called SMT reflow, are becoming increasingly popular.

[0005] Reflow soldering or reflow soldering is a soft soldering process known in electrical engineering that is used for soldering SMD components (SMD: surface mounted device).

[0006] A critical issue with SMT busbars, however, is the contact resistance between the busbars. With conventional methods, the current between the busbars must always flow via the circuit board. To increase the width of this current path, SMT busbars are placed offset from each other, for example. Nevertheless, each SMT busbar is soldered separately, resulting in a contact resistance of 10 µΩ to 100 µΩ, depending on the spacing and design. Disclosure of the invention

[0007] Against this background, a printed circuit board according to claim 1 and a method for processing a printed circuit board with the features of claim 8 are presented. Embodiments emerge from the dependent claims and from the description.

[0008] In addition to the typically provided components, the printed circuit board presented here features an array of busbars. These busbars are used to conduct particularly high currents.

[0009] The busbars are in electrical contact with the printed circuit board. Furthermore, the busbars are arranged such that at least one current path is formed. These current paths thus form the paths over which, independently of conductor tracks in or on the printed circuit board, in particular high currents can be conducted. It is important that these have the lowest possible ohmic resistance. It has now been recognized that, in order to achieve the lowest possible resistance, particular attention must be paid to the transitions between the busbars in a current path. To date, the transition has been via conductor tracks on the printed circuit board to which the busbars are electrically connected, i.e. there has been direct contact between the busbars and the printed circuit board, but not between the individual busbars, not even between the busbars in a current path.

[0010] It is now proposed that adjacent busbars in at least one current path be directly connected to each other via electrical connections. Thus, there is direct electrical contact between the respective busbars and not just indirect contact via the circuit board.

[0011] The electrical contacts between the busbars and the printed circuit board can be provided by connections selected from a group consisting of: welded connection, press fit, soldered connection.

[0012] The electrical connections between the adjacent busbars may be provided by connections selected from a group consisting of: welded connection, press fit, soldered connection.

[0013] On a printed circuit board, the busbars can be arranged alternately within a current path. Adjacent busbars are typically soldered together along their long sides.

[0014] A method for processing a printed circuit board is also presented, which includes the following steps: - Arranging the busbars on the circuit board so that at least one current path is formed, - electrical contact of the busbars with the circuit board, - direct electrical connection of adjacent busbars in at least one current path.

[0015] After processing, the printed circuit board is a printed circuit board as presented herein and described in claim 1.

[0016] The electrical contacts between the busbars and the printed circuit board and / or the electrical connections between adjacent busbars may be provided by connections selected from a group consisting of: welded connection, press fit, soldered connection.

[0017] Furthermore, the busbars of a current path can be arranged alternately. In this case, adjacent busbars of a current path are typically soldered together along their long sides.

[0018] In one embodiment, the bus bars are mounted on the circuit board using a surface mount technology.

[0019] In addition, the busbars can be connected directly to the circuit board using reflow soldering. In electrical engineering, reflow soldering is a soft soldering process for soldering SMD components.

[0020] In this process, the soft solder is typically applied to the circuit board in the form of solder paste before assembly. The components are then assembled in the next step. The assembled circuit board is then heated to such an intense level that the solder contained in the solder paste melts. At the same time, the increased temperature activates the flux in the solder paste gel. The surface tension of the molten solder attracts the components to the center of the landing pads.

[0021] The invention thus relates to a special arrangement of SMT busbars in which the busbars are soldered not only to the circuit board but also to each other during the reflow process. Soldering the busbars together in this way greatly increases the area of ​​the transition and significantly reduces the distance between the busbars. This results in contact resistances of less than 3 µΩ.

[0022] Furthermore, it should be taken into account that, since busbars pull towards each other during soldering, long busbar sections in particular are shortened.

[0023] This can be avoided, for example, by soldering the busbars alternately and along their long side.

[0024] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

[0025] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention. Short description of the drawings Fig. 1 shows in four representations and partly schematically an embodiment of the presented circuit board in different manufacturing states. Fig. 2 shows in three representations and partly schematically another embodiment of the presented circuit board in different manufacturing states. Fig. 3 shows a flowchart of a possible embodiment of the described method. Fig. 4 shows a block diagram of the assembly of a printed circuit board. Embodiments of the invention

[0026] The invention is illustrated schematically in the drawings using embodiments and is described in detail below with reference to the drawings.

[0027] Fig. 1 shows, in a first illustration 10, a plan view of a current path 12 on a circuit board 14 before soldering. A second illustration 20 shows the current path 12 in a plan view after soldering. A third illustration 30 shows the current path 12 with the circuit board 14 in a side view after soldering. Another illustration 40 shows a corresponding test sample of a current path 42 on a circuit board 44 in a plan view after soldering.

[0028] In the first illustration 10, it can be seen that the current path 12 comprises three busbars 50, 52, and 54. The illustration 10 shows areas provided with solder paste 60, areas provided with copper 62, and the three busbars 50, 52, and 54. The second illustration 20 further shows soldering points 70, the areas provided with copper 62, and areas with resist 80. The third illustration 30 particularly shows the structure of the circuit board 14 with resist 80 and areas with copper 62. It is also made clear that a soldering point 70 is provided between each adjacent busbar 50, 52, and 54, which represents a direct electrical connection. Thus, the adjacent busbars 50 and 52, as well as the adjacent busbars 52 and 54, are directly connected to one another.

[0029] The illustration 40 shows the current path 42 on the printed circuit board 44. It is illustrated that segments of the current path, the busbars 84, 86, 88, 90 and 92, are connected to one another via solder joints 94 in such a way that two adjacent busbars 84 and 86, 86 and 88, 88 and 90 and 90 and 92 are each in direct contact via a solder joint 94.

[0030] Fig. Figure 2 shows three views of another embodiment of the presented circuit board prior to soldering. The first view 100 shows a current path 102 arranged on a circuit board 104. It can be seen that the current path 102 comprises four busbars 110, 112, 114, and 116. These are arranged side by side, offset from one another.

[0031] The second representation 120 again shows the current path 102 with the circuit board 104 after soldering. The representations 100, 120 again show areas with solder paste 130, areas with copper 132, solder joints 134, and areas with resist 136.

[0032] The third view 150 again shows a test pattern of a corresponding current path 152 on a circuit board 154.

[0033] The second illustration 120 illustrates that adjacent busbars 110, 112, 114, 116, in this case the busbars 110 and 112, 112 and 114 and 114 and 116, are arranged alternately and are soldered to one another along their long sides.

[0034] Fig. 3 shows a flowchart of a possible embodiment of the presented method.

[0035] In a first step 200, busbars are arranged on a circuit board, forming at least one current path. In a next step 202, the busbars are electrically connected to the circuit board. Then, in a step 204, adjacent busbars are directly electrically connected to one another in at least one current path.

[0036] The last two steps can also be performed in a single process step. After processing, the printed circuit board is a printed circuit board of the type presented here.

[0037] Fig.Figure 4 shows a block diagram of the assembly of a printed circuit board, designated overall by reference numeral 300. The illustration shows a battery 302 and a DC-DC converter 304, which are connected to the circuit board via a current path 306. The circuit board 300 also has three connections for a first channel 310, a second channel 312, and a third channel 314.

[0038] On the circuit board are a logic control unit 320 for a safe state, a microcontroller 322, a system base chip 324, a CAN interface 326 (CAN: Controller Area Network), a first gate driver unit 330 with an associated MOSFET 332 as a switch, a second gate driver unit 340 with an associated MOSFET 342 as a switch, and a third gate driver unit 350 with an associated MOSFET 352. Furthermore, a fourth gate driver unit 360 with an associated MOSFET unit 362 as a switch unit and an associated resistor 364 is provided.

Claims

[1] Printed circuit board with an arrangement of busbars (50, 52, 54, 84, 86, 88, 90, 92, 110, 112, 114, 116), wherein the busbars (50, 52, 54, 84, 86, 88, 90, 92, 110, 112, 114, 116) are in electrical contact with the printed circuit board (14, 44, 104, 154, 300), the busbars (50, 52, 54, 84, 86, 88, 90, 92, 110, 112, 114, 116) are arranged such that at least one current path (12, 42, 102, 152, 306) is formed, adjacent busbars (50, 52, 54, 84, 86, 88, 90, 92, 110, 112, 114, 116) in at least one current path (12, 42, 102, 152, 306) are directly electrically connected to one another via a connection. [2] Printed circuit board according to claim 1, wherein the electrical contacts between the bus bars (50, 52, 54, 84, 86, 88, 90, 92, 110, 112, 114, 116) and the printed circuit board (14, 44, 104, 154, 300) are provided by connections selected from a group consisting of: welded connection, press fit, soldered connection. [3] Printed circuit board according to claim 1 or 2, wherein the electrical connections between the adjacent bus bars (50, 52, 54, 84, 86, 88, 90, 92, 110, 112, 114, 116) are provided by connections selected from a group consisting of: welded connection, press fit, soldered connection. [4] Printed circuit board according to one of claims 1 to 3, in which the busbars (110, 112, 114, 116) are arranged alternately. [5] Method for processing a printed circuit board (14, 44, 104, 154, 300) with the following steps: Arranging busbars (50, 52, 54, 84, 86, 88, 90, 92, 110, 112, 114, 116) on a printed circuit board (14, 44, 104, 154) so ​​that at least one current path (12, 42, 102, 152, 306) is formed, electrical contacting of the busbars (50, 52, 54, 84, 86, 88, 90, 92, 110, 112, 114, 116) with the printed circuit board (14, 44, 104, 154, 300), direct electrical connection of adjacent busbars (50, 52, 54, 84, 86, 88, 90, 92, 110, 112, 114, 116) in at least one current path (12, 42, 102, 152, 306) to one another. [6] Method according to claim 5, wherein the electrical contacts between the bus bars (50, 52, 54, 84, 86, 88, 90, 92, 110, 112, 114, 116) and the printed circuit board (14, 44, 104, 154, 300) are provided by connections selected from a group consisting of: welded connection, press fit, soldered connection. [7] Method according to claim 5 or 6, wherein the electrical connections between the adjacent busbars (50, 52, 54, 84, 86, 88, 90, 92, 110, 112, 114, 116) are provided by connections selected from a group consisting of: welded connection, press fit, soldered connection. [8] Method according to one of claims 5 to 7, in which the busbars (50, 52, 54, 84, 86, 88, 90, 92, 110, 112, 114, 116) are arranged alternately. [9] Method according to one of claims 5 to 8, wherein the busbars (50, 52, 54, 84, 86, 88, 90, 92, 110, 112, 114, 116) are mounted on the printed circuit board (14, 44, 104, 154, 300) by means of a surface mounting technology. [10] Method according to claim 9, wherein the bus bars (50, 52, 54, 84, 86, 88, 90, 92, 110, 112, 114, 116) are connected directly to the printed circuit board (14, 44, 104, 154, 300) by means of reflow soldering.

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