Method for manufacturing an electronic power circuit

Abstract

Method (200) for manufacturing an electronic power circuit (100), comprising the following steps: a) Placing (210) a first electronic component (115) on a surface of a support material (105); b) Placing (215) a busbar (110) on the same surface of the support material (105) on which the first electronic component (115) is placed; c) Placing (225) a second electronic component (120) on a surface of the busbar (110); and d) Heating (230) the electronic components (115, 120), the busbar (110) and the substrate material (105) in order to solder them together.

Description

[0001] The invention relates to a method for manufacturing an electronic power circuit and thus also to an electronic power circuit manufactured using the aforementioned method.

[0002] An electronic power circuit comprises a circuit board or other substrate and an electronic component that is subjected to currents of such high power that it heats up during operation. The power circuit therefore also includes a sufficiently dimensioned busbar to ensure an electrical connection to the electronic component and to dissipate the heat generated.

[0003] The publication EP 2 043 412 A1 describes an electrical control unit comprising a printed circuit board and a power semiconductor component soldered to the top side of the board. The control unit also includes a busbar soldered to the underside of the board.

[0004] Publication WO 2011 / 113 867 A1 describes a circuit unit comprising a printed circuit board (PCB) and electronic components mounted on a first surface of the PCB. The PCB has busbars on a second surface, opposite the first surface containing the electronic components, which are attached to the second surface of the PCB by means of fasteners.

[0005] There are various proposals for attaching the substrate, the busbar, and the electronic component. In one approach, the busbar is located wholly or partially within the substrate. This requires a recess in the substrate that precisely matches the dimensions of the busbar. Other elements, particularly an electrical connection running within the substrate, cannot be implemented in the area of ​​the recess. Adjacent busbars must maintain a predetermined minimum distance to ensure that any remaining structures of the substrate survive the manufacturing process undamaged. Simultaneously, the busbar must not be too thin, providing sufficient surface area for bonding with the substrate. In some approaches, the busbar must be bonded to the substrate, which can significantly increase manufacturing complexity.Often, excess adhesive residue has to be removed after gluing, which can contribute to further increased manufacturing costs.

[0006] In another variant, the busbar is glued to an upper or lower surface of the substrate material or attached using a pin or rivet. If the busbar is located on the opposite side of the electronic component from the substrate material, an additional element, such as a rivet, must be used for the electrical and thermal connection of the electronic component. If the busbar is located between the substrate material and the electronic component, the additional height of the busbar can complicate automated placement using a surface-mount machine. Furthermore, the vertical elements of this variant can lead to mechanical difficulties during subsequent processing.

[0007] One object of the present invention is therefore to demonstrate an approach that can at least partially reduce the aforementioned disadvantages.

[0008] The items claimed in the claims solve this problem. Therefore, a method for manufacturing an electronic power circuit (and thus an electronic power circuit manufactured using the said method) is disclosed.

[0009] To solve the aforementioned problem, a method for the simplified manufacture of an electronic power circuit with a busbar is disclosed. Furthermore, a busbar suitable for this purpose and a system of such busbars are disclosed.

[0010] A method described here for manufacturing an electronic power circuit comprises steps of placing a first electronic component on the surface of a substrate material, placing a busbar on the surface of the substrate material, placing a second electronic component on the surface of the busbar, and heating this arrangement to solder the electronic components, the busbar, and the substrate material together.

[0011] In this way, the busbar can be treated like an electrical component that is placed on the surface of the substrate during circuit assembly. This can substantially simplify the assembly process, for example, using a pick-and-place machine. The simplified assembly process can increase the positioning accuracy of the busbar on the substrate. In particular, the first electronic component and the busbar can make contact with the substrate surface in the same plane, which can further simplify assembly.

[0012] Furthermore, multiple busbars can be mounted close together on the surface of the substrate. The thickness or vertical height of the busbar can be flexibly selected. The thickness of the substrate can be varied independently or remain constant. A number of critical dimensions of the busbar and the substrate can be reduced. The tolerance chain between the busbar and the first electronic component can be improved, as both components are mounted on the substrate using the same process. The electrical and thermal connection between the second electronic component and the busbar can be improved, since no additional element such as a milled recess, a microvia, a rivet, or a pin is required for the electrical and mechanical connection of the second electronic component to the busbar.

[0013] Furthermore, the described method has the advantage that the surface of the substrate material can be flat before component placement, thus facilitating substrate preparation, for example, by applying soft solder to planned contact points between the substrate material and the busbar or between the substrate material and the first electronic component. Soldering the busbar to the substrate material automatically creates an electrical (and mechanical) connection between the two elements. No additional connecting element, such as a rivet or vertical pin, is required. Manual steps can be largely eliminated, making the method particularly suitable for automated industrial mass production.

[0014] In a preferred embodiment, soft solder in the form of solder paste is applied to the substrate before the first electronic component or busbar is placed on it. In particular, the solder paste can be printed onto the flat surface of the substrate in a single operation, for example using screen printing.

[0015] To connect the second electronic component to the surface of the busbar, a molded part made of soft solder can be attached to the busbar before the second electronic component is placed on it. In one embodiment, the molded part is attached to the busbar before the busbar is placed on the substrate.

[0016] In another embodiment, an adhesive is applied between the busbar and the substrate before heating. The adhesive can be applied, in particular, to the busbar or the substrate before the busbar itself is placed on the substrate. The adhesive, for example in the form of one or two adhesive dots, can serve to fix the busbar in place until the busbar is soldered to the substrate.

[0017] A busbar described here for connecting an electronic component to a substrate material comprises a lower surface with a flat section for surface mounting the busbar to the substrate material and an upper surface with a flat section for surface mounting an electronic component to the busbar. In particular, the lower and upper surfaces are located on opposite sides of the busbar.

[0018] Preferably, the dimensions of the busbar are sufficiently small to allow for placement of components on the substrate using a pick-and-place machine for surface-mount devices. For automated placement, a large number of busbars can be provided on a suitable tray.

[0019] In a particularly preferred embodiment, a recess for receiving a deposit of soft solder is arranged in the upper surface of the busbar. In a further embodiment, the busbar encompasses the deposit of soft solder arranged in the recess. The deposit can be provided by a preformed piece of soft solder. This facilitates the assembly of the second electronic component as the final step before soldering the electronic power circuit.

[0020] Furthermore, a system of multiple busbars for connecting an electronic component to a substrate material is described, comprising a first and a second busbar as described above, wherein the first busbar has a lateral projection and the second busbar has a corresponding lateral recess, so that the busbars can be arranged directly adjacent to one another with the projection engaging in the recess. The recess and the projection are, in particular, complementary to each other.

[0021] By placing several first and second busbars side by side, different busbar configurations can be created. This can reduce the number of different components in the electronic power circuit, potentially resulting in cost advantages in manufacturing.

[0022] The first and second busbars, for example, have cross-sections derived from a common basic shape. This basic shape can be, in particular, a rectangle or a square. The first and second busbars can thus be connected to each other like puzzle pieces, either on one or more sides, especially to ensure a seamless connection.

[0023] Electronic components are defined as components used to implement an electronic circuit. The components themselves are electrical or electronic circuit components, for example, semiconductor devices, capacitors, inductors, conductors, or terminal contacts. Preferably, at least one of the components, particularly of the method, busbar, or system, is a power component, especially a power semiconductor device. Power components are preferably placed on the busbar. In particular, the second component is a power component, preferably a semiconductor device. At least one of the components, at least one of which has its own housing, and in particular the at least one power component, is preferably a surface-mountable component.an SMT component. The power component is designed to carry or switch a current of preferably at least 1 A, 5 A, 10 A, or 20 A.

[0024] According to another aspect, at least one of the components is a switch, in particular an electronic switch. Furthermore, at least one of the components, and in particular the second component, can be a MOSFET, an IGBT, a thyristor, a TRIAC, a transistor, or a diode, or comprise at least one of these semiconductor devices. It can also be provided that a power component is connected via a busbar to a conductor or to a terminal designed for power applications and, in particular, designed to carry currents of at least 1 A, 5 A, 10 A, or 20 A.

[0025] Furthermore, at least one of the components can be an integrated circuit, in particular a microcontroller, a control circuit, a processor, or a driver circuit, configured to output control signals to a power component. Such control signals are provided with currents preferably less than 1 A, less than 100 mA, or less than 10 mA. The components are adapted to the current to be supplied, switched, or controlled, in particular by means of conductor cross-sections. The first component is preferably an integrated circuit, in particular a microcontroller, a control circuit, a processor, or a driver circuit, or a discrete or passive or active component configured for currents not exceeding 1 A, 100 mA, or 10 mA.

[0026] The components comprise at least one passive and / or at least one active circuit component. The components comprise at least one discrete and / or at least one integrated circuit component.

[0027] The invention will now be described in more detail with reference to the attached figures. These show: Fig. 1 an electronic power circuit; Fig. 2 a method for manufacturing the electronic power circuit from Fig. 1; Fig. 3 a modular busbar for the power circuit Fig. 1; and Fig. 4 a system of different busbars according to the Fig. 3.

[0028] The Fig. Figure 1 shows a power circuit 100. The upper part of the illustration shows a top view, the lower part a longitudinal section through the power circuit 100.

[0029] The power circuit 100 comprises a carrier material 105, a busbar 110, a first electronic component 115, and a second electronic component 120. The lower illustration also shows a cooling element 122, which, however, is not necessarily part of the power circuit 100.

[0030] The carrier material 105 preferably comprises a core 125 on the upper surface of which a conductive track 130 is arranged. A further conductive track 130 may extend along the lower surface of the core 125, with opposing conductive tracks 130 being vertically connected to one another. The busbar 110 and the first electronic component 115 can be soldered to the conductive track 130 of the carrier material 105 by applying a soft solder to the upper surface of the carrier material 105, with which the lower surfaces of the first electronic component 115 and the busbar 110, respectively, are in contact, and by temporarily heating the soft solder. In a preferred embodiment, the soft solder, in the form of solder paste 135, is applied to the upper surface of the carrier material 105 by means of a printing process before the busbar 110 or the first electronic component 115 is placed on it.

[0031] To fix the busbar 110 to the carrier material 105, an adhesive 132 can be used, which is applied to the busbar 110 or the carrier material 105 before the busbar 110 is placed. The adhesive 132 can be used, for example, to form one or more adhesive points.

[0032] To solder the second electronic component 120 to the busbar 110, a soft solder in the form of solder paste 135, as described above, can again be applied between the second electronic component 120 and the busbar 110. Alternatively, a molded part 140 made of soft solder can be attached to the surface of the busbar 110 or the lower surface of the second electronic component 120 before the second electronic component 120 is attached to the busbar 110.

[0033] In the exemplary embodiment shown, the second electronic component 120 is connected to two adjacent busbars 110. Furthermore, the second electronic component 120 includes a vertical connection for direct contact with a conductor track 130 of the carrier material 105. In the illustrated variant, the carrier material 105 includes a recess 145 to allow the cooling element 122 to contact the lower surface of the busbar 110. The cooling element 122 is typically located at a point of use within the power circuit 100 and, for example, in automotive engineering, can consist of or be connected to a body panel.

[0034] The Fig. Figure 2 symbolically shows the steps of a process 200 for manufacturing the electronic power circuit 100. Fig. 1. In a first step 205, a soft solder, preferably in the form of solder paste 135, is applied to the surface of the substrate material 105. Subsequently, in a step 210, the first electronic component 115 is placed on the surface of the substrate material 105. This step is preferably carried out using an SMD placement machine. More preferably, after all of a plurality of first electronic components 115 have been placed on the substrate material 105, the busbar 110 is also placed on the substrate material 105 in a step 215. This step can also be carried out by the placement machine. In one embodiment, an adhesive 132 is also applied to the substrate material 105 or the busbar 110 before the busbar 110 is placed.

[0035] Although the busbar 110 can also be placed in front of one or more of the first electronic components 115 on the carrier material 105, it may be advantageous to mount the busbar 110 later in order not to impair the accessibility of the carrier material 105 by the relatively large busbar 110.

[0036] In a subsequent step 220, soft solder in the form of the molded part 140 is applied to the upper surface of the busbar 110 or the lower surface of the second electronic component 120. Instead of the molded part 140, soft solder in a different form, preferably as printable solder paste 135, can also be used. Then, in a step 225, the second electronic component 120 is placed on the surface of the busbar 110.

[0037] To ensure the relative positioning of the busbar 110 on the carrier material 105, the cooling element 122 or a suitably shaped spacer can be inserted into the recess 145 before a final step 230 is performed, in which the power circuit 100 is heated to solder the electronic components 115, 120, the busbar 110, and the carrier material 105 together. After the power circuit 100 has cooled, the cooling element 122 can be removed. With the completion of the soldering process, the power circuit 122 is finished.

[0038] The Fig. Figure 3 shows a modular busbar 305, which is used as busbar 110 in the power circuit 100. Fig. 1 used and in particular by means of the in Fig. The manufacturing process 200 shown in Figure 2 can be processed. A three-sided view is shown, with a front view at the top left, a side view at the top right, and a top view of the busbar 305 at the bottom.

[0039] The busbar 305 has a cross-section or base area in plan view that is rectangular, in particular square. A recess 310 is provided on one side of the base body and a projection 315 on another side. In the Fig. In Figure 3, the recess 310 and the projection 315 are opposite each other, but they can also be located on adjacent sides of the rectangular base body. The recess 310 and the projection 315 correspond to each other so that the projection 315 of a first busbar 305 can engage as precisely as possible with the recess 310 of a second busbar 305. The busbars 305 preferably rest against each other without a gap. Accordingly, the recess 310 and the projection 315 can also have trapezoidal or rounded shapes, like a puzzle piece, unlike those shown. The recess and the projection are designed to be complementary to each other, preferably such that they can be slid into one another. The recess, or the recess and the projection, do not have an undercut.

[0040] To facilitate the electrical and mechanical connection of the two adjacent busbars 305, a recess 320 is provided in the area of ​​the projection 315 for receiving soft solder in the form of solder paste 135 or a molded part 140. In other embodiments, the recess 320 can also be incorporated into the busbar 305 in the area of ​​a boundary of the recess 320.

[0041] Fig. Figure 4 shows a system of 400 different modular busbars 305 in further embodiments 405 to 440. Each of the busbars 405 to 440 shown has at least one recess 310 or a projection 315. A basic shape of all the busbars 405 to 440 shown is derived from the rectangular or square basic shape described above with reference to Fig. 3 was explained.

[0042] The embodiments 405 and 415 are complementary to each other in that their top views are mirror images of each other. The recess 310 and the projection 315 are located on adjacent sides of the rectangular base body of the conductor rails 405 and 415, respectively. The other two sides do not form a corner, but are curved into each other.

[0043] The busbar 435 also has a vertical recess 445. Furthermore, the rectangular or square base body is shown in the representation of Fig. 4 extended in the vertical direction, so that the recess 320 does not reduce the size of the base body. Reference symbol list 100 power circuit 105 Carrier material 110 busbar 115 first electronic component 120 second electronic component 122 Cooling element 125 core 130 conductor track 132 adhesives 135 Soft solder 140 molded part 145 recess 200 procedures 205 Applying solder paste 210 Place first component 220 Attaching a molded part using soft solder 225 Place second component 225 Heating 305 modular busbar 310 Exclusion 315 lead 320 In-depth 400 System 405-440 modular busbars 445 Exclusion

Claims

[1] Method (200) for manufacturing an electronic power circuit (100) comprising the following steps: a) Placing (210) a first electronic component (115) on a surface of a support material (105); b) Placing (215) a busbar (110) on the same surface of the support material (105) on which the first electronic component (115) is placed; c) Placing (225) a second electronic component (120) on a surface of the busbar (110); and d) Heating (230) the electronic components (115, 120), the busbar (110) and the substrate material (105) in order to solder them together. [2] Method (200) according to claim 1, further comprising applying (205) solder paste (135) to the carrier material (105) before placing the first electronic component (115) or busbar (110) on it (105). [3] Method (200) according to claim 1 or 2, further comprising attaching (220) a molded part (140) made of soft solder to the busbar (110) before placing the second electronic component (120) on it (110). [4] Method (200) according to one of the preceding claims, wherein an adhesive (132) is applied (215) between the busbar (110) and the carrier material (105).

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