Circuit arrangement with power transistor, vehicle comprising the circuit arrangement and method for mounting a power transistor

Abstract

Circuit arrangement (100) comprising: - a printed circuit board (102) with conductor tracks (103); - a ceramic plate (104); - at least one transistor (101) arranged between the printed circuit board (102) and the ceramic plate (104) and electrically connected to conductor tracks (103) on a side of the printed circuit board (102) facing the transistor (101); - at least one buffer layer (105) arranged laterally next to the transistor (101) between the printed circuit board (102) and the ceramic plate (104); wherein the circuit board (102), the ceramic plate (104), the transistor (101) and the buffer layer (105) form a partial assembly (102, 101, 105, 104); a heat conductor (109) arranged on a side of the ceramic plate (104) facing away from the transistor (101); and at least one screw (107) that fixes the partial assembly (102, 101, 105, 104) to the heat conductor (109); wherein the screw (107) is a plastic screw;and / or- the heat conductor (109) has a plastic bushing (108) into which the screw (107) is screwed.;

Description

[0001] The invention relates to a method for mounting a power transistor on a printed circuit board. Furthermore, the invention relates to a circuit arrangement comprising a printed circuit board and a power transistor.

[0002] Power transistors are used in electrically powered vehicles, for example, to provide an inverter for controlling the vehicle's electric motor and / or a DC / DC converter for charging the vehicle's battery. Power transistors are typically arranged in pairs on a circuit board to form a half-bridge. The power transistors are then controlled via control lines on the circuit board. Furthermore, the switched currents of the power transistors are carried via power lines on the circuit board.

[0003] Operating a power transistor generates heat, which must be reliably dissipated. Furthermore, for rapid current switching, a low-inductance connection between the power transistor and the power lines of a printed circuit board is required.

[0004] This document addresses the technical challenge of providing a cost-effective mounting of a power transistor on a printed circuit board, enabling reliable heat dissipation, high electrical safety, and low-inductance connection.

[0005] The problem is solved by the independent claims. Advantageous embodiments are described, among other things, in the dependent claims.

[0006] According to one aspect, a circuit arrangement is described that comprises a printed circuit board (PCB) with conductive traces and a ceramic plate. The PCB can have conductive traces on both a top and a bottom surface. The circuit arrangement includes at least one transistor (in particular a power transistor, e.g., a gallium nitride transistor) that is positioned between the PCB and the ceramic plate and is electrically connected to it via conductive traces on the side of the PCB facing the transistor (e.g., on the underside of the PCB). The transistor can be fixed to the PCB, particularly using surface-mount technology (SMD), e.g., soldered. Furthermore, the transistor can be fixed to the ceramic plate, particularly by soldering or gluing.

[0007] The circuit arrangement further includes at least one buffer layer, which is positioned laterally next to the transistor between the printed circuit board and the ceramic plate. The buffer layer can, for example, comprise an underfill material and / or an elastic material (especially a plastic material). The buffer layer can (optionally completely) surround the transistor. Alternatively or additionally, the circuit arrangement can have several locally isolated (e.g., circular) buffer layers. The buffer layer can act as a buffer between the printed circuit board and the ceramic plate to reduce pressure on the transistor during assembly.

[0008] The printed circuit board, the ceramic plate, the transistor, and the buffer layer form a partial assembly. This partial assembly can form a coherent structure that can be handled as a whole. In particular, the ceramic plate and the printed circuit board can be held together by the transistor and / or the buffer layer.

[0009] The circuit arrangement further comprises a heat conductor (e.g., a cast aluminum part) located on the side of the ceramic plate facing away from the transistor. The circuit arrangement also includes at least one screw (in particular, a plastic screw) that secures the circuit assembly to the heat conductor. The circuit board and the ceramic plate typically have an opening (in particular, a hole) through which the screw passes. The one or more buffer layers are preferably arranged in the immediate vicinity of this opening.

[0010] The circuit arrangement enables cost-effective, gentle, and low-inductance operation of high-frequency power transistors. Furthermore, the design of the circuit arrangement (especially the ceramic plate and the mechanics of the circuit arrangement) can be configured to maintain specific clearance and creepage distances. This ensures a certain level of electrical safety.

[0011] The heat conductor can have a plastic bushing into which the screw is screwed. Providing a plastic bushing allows for increased air and creepage distances and further enhances the electrical safety of the circuit arrangement.

[0012] The circuit arrangement, and in particular the partial arrangement, can include two or more transistors (e.g., to provide a half-bridge or a full bridge).

[0013] According to another aspect, a method for mounting a transistor is described. This method involves positioning the transistor between a printed circuit board (PCB) and a ceramic plate. First, the transistor can be fixed to the ceramic plate (in particular, soldered to it). Then, the transistor, along with the ceramic plate, can be fixed to the PCB (in particular, soldered to it). Particularly efficient is the ability to perform both the fixing of the transistor to the ceramic plate and the fixing of the transistor to the PCB in a single fixing process (in particular, in a single soldering operation). This enables a particularly efficient manufacturing of a circuit device.

[0014] The method further includes placing a buffer layer laterally next to the transistor between the printed circuit board and the ceramic plate, creating a partial assembly consisting of the printed circuit board, ceramic plate, transistor, and buffer layer. The method also includes fixing the partial assembly to a heat conductor with a screw, so that the ceramic plate is positioned between the printed circuit board and the heat conductor.

[0015] The process makes it possible to integrate a transistor into a circuit on a printed circuit board in a cost-effective manner and with stable quality.

[0016] According to another aspect, a vehicle (especially a road vehicle, e.g., a passenger car, a truck, or a motorcycle) is described that includes the circuit arrangement described in this document.

[0017] It should be noted that the methods, devices, and systems described in this document can be used both alone and in combination with other methods, devices, and systems described in this document. Furthermore, any aspect of the methods, devices, and systems described in this document can be combined with one another in a variety of ways. In particular, the features of the claims can be combined with one another in a variety of ways.

[0018] The invention will now be described in more detail using exemplary embodiments. Fig. 1 a side view of an exemplary circuit arrangement with a power transistor; Fig. 2 a top view of an exemplary ceramic plate with two power transistors; and Fig. 3. A flowchart of an exemplary procedure for assembling a power transistor.

[0019] As stated at the outset, this document deals with the cost-effective, gentle, and low-inductance mounting of a power transistor on a printed circuit board. In this context, it shows Fig. 1. A side view of an example circuit arrangement 100 with a circuit board 102 and one on the circuit board 102 mounted power transistor 101 (in particular a gallium nitride transistor). The circuit board 102 It typically includes a conductor layer on both surfaces. 103 (e.g., made of copper). The transistor 101 is directly connected to the conductors of the conductor layer 103 connected to circuit board 102, which is connected to the transistor 101 is facing towards, so that a low-inductance connection of the transistor is achieved. 101 is made possible. In particular, the transistor can 101 using SMD (surface mount device) technology on the circuit board 102 to be installed.

[0020] The transistor 101 one of the circuit boards 102 facing side and one of the circuit board 102 far side. The far side of the transistor 101 is on a ceramic plate 104 mounted, which in turn is located between transistor 101 and a heat conductor 109 (e.g., made of aluminum) is arranged. The use of a ceramic plate 104 On the one hand, it enables good heat dissipation to the heat conductor. 109 on the one hand and on the other hand good electrical insulation to the heat conductor 109 (to ensure certain air and crawl spaces).

[0021] Between circuit board 102 and ceramic plate 104 is to the side of the transistor 101 a buffer layer 105The components are arranged from an underfill material or an elastic, plastic-based material. This results in a sandwich-like partial arrangement of printed circuit boards. 102 and ceramic plate 104 with a transistor placed in between 101 or an intermediate buffer layer 105 This arrangement can be secured with one or more screws. 107 on the heat conductor 109 to be fixed. This can be done in the heat conductor. 109 for each screw 107 A socket (e.g. a plastic socket) is provided into which a screw can be inserted. 107 (especially a plastic screw) can be screwed in.

[0022] On the transistor 101 far side of the circuit board 102 (e.g. the top side of the circuit board) 102 ) can include one or more additional components 106 (e.g., one or more capacitors) can be arranged.

[0023] Fig. Figure 2 shows a top view of an example ceramic plate. 104 with two transistors 101 , which, for example, is on the ceramic plate 104 were soldered on. Furthermore, the ceramic plate has 104 two drill holes 110 for the screws 107 on. Furthermore, there are on the ceramic plate 104 four circular buffer layers 105 to compensate for the pressure on the transistors 101 during assembly on the heat conductor 109 arranged.

[0024] In the Fig. 1 and Fig. 2 will therefore be a structure 100 two fast-switching power transistors 101 Described as having relatively high thermal conductivity. The structure 100 exhibits, in particular, one or more buffer layers. 105 a relatively low mechanical stress on the transistors 101through the assembly. Furthermore, a low-inductance connection of the transistors to the circuit board is used. 102 as well as sufficiently long clearance and crawl space.

[0025] On the ceramic plate 104 one or more (for example, gallium nitride) transistors are used. 101 soldered on and the circuit board placed over it 102 placed. The resulting gap at the ends of the circuit board 102 and the ceramic plate 104 It is filled with liquid or solid underfill material to create a buffer layer. 105 to provide. The underfill material can be used, for example, during the soldering process between the printed circuit board. 104 and the transistors 101 harden. The entire circuit board or partial assembly (i.e., the printed circuit board) can then be... 102 and the ceramic plate 104 with the one or more transistors in between 101 ) with plastic screws107 on a heat conductor 109 (for example, an aluminum die-casting).

[0026] For optimal thermal integration of the power transistors 101 to the heat conductor 109 On the one hand, and to minimize stress on the electrical connections, it should be ensured that the screws 109 There should be no overloading or underloading at the fixing points. This can be achieved, for example, on the outer sides of the screws. 107 Underfill material (i.e., a buffer layer) 105 ) between the circuit board 104 and the ceramic plate 104 to be introduced, which ensures an even distribution of load and pressure between the circuit board 102 , the transistors 101 and the ceramic plate 104 provides.

[0027] The underfill material can be either liquid or solid before installation, with liquid material typically requiring an additional spreading and curing step during assembly. The in Fig. 1. Plastic bushing shown 108 It serves to ensure sufficient air and creepage distance between the transistor 101 and heat conductors 109 .

[0028] Fig. Figure 3 shows a flowchart of an example procedure. 300 for mounting a transistor 101 The procedure 300 includes arranging 301 of the transistor 101 between a circuit board 102 and a ceramic plate 104 For example, the transistor can first be 101 on the ceramic plate 104 The transistor must be fixed in place (especially soldered). Then the transistor can be... 101 with the ceramic plate 104 on the circuit board 102be fixed (especially soldered).

[0029] The procedure 300 further includes ordering 302 a buffer layer 105 (especially from an underfill material) to the side of the transistor 101 between the circuit board 102 and the ceramic plate 104 , so that a partial arrangement 102 , 101 , 105 , 104 from circuit board 102 , ceramic plate 104 , Transistor 101 and buffer layer 105 The buffer layer is formed. 105 can be placed, for example, on a ceramic plate 104 be applied before the transistor 101 on the circuit board 102 is fixed. This allows for a buffer layer to be used. 105 material used during the transistor fixing process 101 harden on circuit board 102. Furthermore, this allows the buffer layer to harden. 105 in a simple way from above onto the ceramic plate104 be applied.

[0030] Furthermore, the procedure includes fixing 303 the partial arrangement 102 , 101 , 105, 104 on a heat conductor 109 with a screw 107 , so that the ceramic plate 104 between the circuit board 102 and the heat conductor 109 is arranged. The partial arrangement 102 , 101 , 105 , 104 This can form a coherent structure that, as a whole, attaches to the heat conductor. 109 can be fixed.

[0031] The measures described in this document for mounting a transistor 101 enable relatively good heat dissipation and a low-inductance connection to a printed circuit board. 102 Furthermore, relatively long clearance and creepage distances are provided. In addition, cost-effective and rapid assembly with consistently high quality is enabled.

[0032] The present invention is not limited to the embodiments shown. In particular, it should be noted that the description and the figures are intended only to illustrate the principle of the proposed methods, devices, and systems.

Claims

[1] Circuit arrangement (100) comprising, - a printed circuit board (102) with conductor tracks (103); - a ceramic plate (104); - at least one transistor (101) which is arranged between the circuit board (102) and the ceramic plate (104) and which is electrically connected to conductors (103) on a side of the circuit board (102) facing the transistor (101); - at least one buffer layer (105) arranged laterally next to the transistor (101) between the circuit board (102) and the ceramic plate (104); wherein the circuit board (102), the ceramic plate (104), the transistor (101) and the buffer layer (105) form a partial arrangement (102, 101, 105, 104); - a heat conductor (109) arranged on a side of the ceramic plate (104) facing away from the transistor (101); and - at least one screw (107) that fixes the partial arrangement (102, 101, 105, 104) on the heat conductor (109). [2] Circuit arrangement (100) according to claim 1, wherein the buffer layer (105) comprises an underfill material and / or an elastic plastic material. [3] Circuit arrangement (100) according to one of the preceding claims, wherein the transistor (101) is fixed to the printed circuit board (102) using SMD technology. [4] Circuit arrangement (100) according to one of the preceding claims, wherein the transistor (101) is soldered onto the ceramic plate (104). [5] Circuit arrangement (100) according to one of the preceding claims, wherein - the screw (107) is a plastic screw; and / or - the heat conductor (109) has a plastic bushing (108) into which the screw (107) is screwed. [6] Circuit arrangement (100) according to one of the preceding claims, wherein the printed circuit board (102) and the ceramic plate (104) have an opening (110) through which the screw (107) passes. [7] Circuit arrangement (100) according to one of the preceding claims, wherein the partial arrangement comprises two or more transistors (101). [8] Circuit arrangement (100) according to one of the preceding claims, wherein the transistor (101) - is a transmission transistor; and / or - is a gallium nitride transistor. [9] Method (300) for assembling a transistor (101), the method (300) comprising, - Arranging (301) the transistor (101) between a printed circuit board (102) and a ceramic plate (104); - Arranging (302) a buffer layer (105) laterally next to the transistor (101) between the printed circuit board (102) and the ceramic plate (104), such that a partial arrangement (102, 101, 105, 104) consisting of printed circuit board (102), ceramic plate (104), transistor (101) and buffer layer (105) is formed; and - Fixing (303) the partial arrangement (102, 101, 105, 104) on a heat conductor (109) with a screw (107) so that the ceramic plate (104) is arranged between the circuit board (102) and the heat conductor (109). [10] Method (300) according to claim 9, comprising arranging (301) the transistor (101), - Soldering the transistor (101) onto the ceramic plate (104); and - Soldering the transistor (101) to the ceramic plate (104) onto the circuit board (102).

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