Circuit carrier and power electronic circuit arrangement with a circuit carrier

Abstract

Circuit carrier (ST) for a power electronic circuit arrangement (SA), comprising: - a low-voltage area (NB) in which at least one first, in particular internal, conductor track (LB1) is arranged for the establishment of a first electrical connection of a low-voltage circuit of the circuit arrangement (SA); - a high-voltage area (HB) in which at least a second, in particular internal, conductor track (LB2) is arranged for the production of a second electrical connection of a high-voltage circuit of the circuit arrangement (SA); - a conductor-free boundary area (AB) between the low-voltage area (NB) and the high-voltage area (HB), which spatially isolates the low-voltage area (NB) from the high-voltage area (HB); and - a thermally conductive, in particular internal, heat transfer rail (WS) for heat transfer between the low-voltage area (NB) and the high-voltage area (HB), which is arranged in the boundary area (AB) and extends into the low-voltage area (NB) and / or the high-voltage area (HB), characterized in that - the second conductor track (LB2) has a second conductor track section (LA2); - the heat transfer rail (WS) has a second rail section (WA2); and - the second conductor track section (LA2) and the second rail section (WA2) overlap in the vertical direction (VR).

Description

Technical field:

[0001] The present invention relates to a circuit carrier, in particular a printed circuit board, and a power electronic circuit arrangement with said circuit carrier, in particular for a hybrid electric / electric vehicle. State of the art and object of the invention:

[0002] Circuit carriers, especially multilayer circuit carriers, are known and are used, among other things, as carriers for a low-voltage circuit and a high-voltage circuit in a power electronic circuit arrangement. Such circuit carriers have both conductor tracks for the low-voltage circuit, intended for establishing electrical connections at a low voltage (protective extra-low voltage), and conductor tracks for the high-voltage circuit, intended for establishing electrical connections at a high voltage. To electrically isolate the conductor tracks of the low-voltage circuit from those of the high-voltage circuit, the circuit carriers are provided with conductor-free areas that extend vertically through the circuit carriers, dividing each circuit carrier into a low-voltage section and a high-voltage section.Neither the traces of the low-voltage circuit nor the traces of the high-voltage circuit run through the trace-free areas. These trace-free areas thus electrically isolate the traces of the low-voltage circuit from those of the high-voltage circuit and consequently serve as electrical isolation between the low-voltage and high-voltage circuits, which are implemented on the same circuit board.

[0003] German patent application DE 10 2013 226 513 A1 describes a printed circuit board (PCB) with a control section and a driver section, as well as a connecting section that links the control section and the driver section. In the connecting section, the PCB has one or more copper layers for electromagnetic shielding.

[0004] German publication DE 43 35 946 A1 describes a power component whose operating heat is to be dissipated. The component is mounted on a printed circuit board (PCB) using a solder pad. For heat dissipation, vias are provided through an insulating gap and outside the solder pad area. These vias ensure good thermal contact between the PCB and the heat sink.

[0005] The publication DE 10 2011 076 273 A1 describes a printed circuit board with a conductor which is designed as a molded part and an electrical component which is attached to the conductor.

[0006] German patent application DE 10 2014 216 194 B3 describes a circuit carrier with an electrically insulating layer and an electrically conductive layer. The circuit carrier has a thermally conductive element embedded in the electrically insulating layer. The thermal element is designed to transport heat loss transversely to a flat extent of the circuit carrier.

[0007] The conductor-free areas, which are usually made of the same electrically insulating material as the carrier plates of the circuit carriers, have a high thermal resistance and are therefore detrimental to efficient cooling of the circuit carriers or the high-voltage circuits built on the circuit carriers, which have high power losses and thus high heat dissipation.

[0008] The purpose of the present application is therefore to provide a means by which a circuit carrier, and thus a power electronic circuit arrangement with a low-voltage and a high-voltage circuit on the said circuit carrier, can be efficiently cooled. Description of the invention:

[0009] This problem is solved by the subject matter of the independent claims. Advantageous embodiments are the subject matter of the dependent claims.

[0010] According to a first aspect of the invention, a circuit carrier for a power electronic circuit arrangement is provided.

[0011] The circuit carrier has a low-voltage area in which at least one first, in particular internal, conductor track is arranged to establish a first electrical connection of a low-voltage circuit of the circuit arrangement.

[0012] The circuit carrier also has a high-voltage area in which at least a second, in particular internal, conductor track is arranged to establish a second electrical connection of a high-voltage circuit of the circuit arrangement.

[0013] The circuit carrier also has a conductor-free boundary area located between the low-voltage area and the high-voltage area, spatially isolating the low-voltage area from the high-voltage area.

[0014] The circuit carrier also features a thermally conductive, specifically internal, heat transfer rail designed for heat transfer between the low-voltage and high-voltage sections. This heat transfer rail is located within the boundary area and extends into the low-voltage and / or high-voltage sections.

[0015] The second conductor track has a second conductor track section. Similarly, the heat transfer rail has a second rail section. The second conductor track section and the second rail section overlap vertically. In other words, the heat transfer rail partially overlaps the second conductor track vertically.

[0016] The partial overlaps of the heat transfer rail with the conductor track of the high-voltage circuit in the vertical direction create a short heat transfer path from the high-voltage circuit to the heat transfer rail.

[0017] The power electronic circuit arrangement described above is a circuit arrangement with both a low-voltage and a high-voltage circuit. An example of such a circuit arrangement is an inverter, which has both a driver or bridge circuit as a high-voltage circuit and a control circuit for controlling the driver or bridge circuit as a low-voltage circuit.

[0018] A circuit carrier is a substrate for (power) electronic components and serves for the mechanical mounting and electrical connection of these components. An example of such a circuit carrier is a printed circuit board (PCB). A circuit carrier typically comprises a substrate made of an electrically insulating material and conductive traces arranged on or embedded in the substrate. A substrate is a plate made of an electrically insulating material, such as a fiber-reinforced plastic or ceramic, which is arranged and bonded together, for example, in the form of prepreg layers or ceramic layers.If a circuit carrier with a substrate has conductor tracks that are embedded in several layers between layers of the electrically insulating material of the substrate, then the circuit carrier is a multilayer circuit carrier.

[0019] The term "internal conductor track" means that the first and second conductor tracks are embedded in the substrate, in particular embedded between two prepreg layers of the substrate.

[0020] The heat transfer rail is thermally conductive (i.e., with a high thermal conductivity of, for example, over 10 W / (m·K), over 20 W / (m·K), or even over 40 W / (m·K), W / (m·K): Watt / (Meter·Kelvin), but preferably electrically insulating (i.e., with a high specific resistance of, for example, over 10 8The heat transfer rail can be configured with a resistance of Ω·cm (Ω·cm: ohm·centimeter). Alternatively, the heat transfer rail can be both thermally and electrically conductive. In this case, the heat transfer rail is preferably electrically insulated from the first and second conductors, as well as any other conductors on and within the circuit carrier. In particular, the heat transfer rail can be configured as a conductor that is electrically insulated from the first and second conductors, as well as any other conductors on and within the circuit carrier.

[0021] The heat transfer rail can be a single layer, meaning it consists of a single, flat layer extending into both the low-voltage and high-voltage areas. Alternatively, it can be a multi-layered heat transfer rail, meaning it consists of several flat layers that are thermally connected and extend partly into the low-voltage area and partly into the high-voltage area. In this case, the layer(s) of the heat transfer rail extend beyond the boundary zone (deeply) into the low-voltage and high-voltage areas, thus thermally connecting them. This thermally bridges the boundary zone, which has a high heat transfer coefficient.The heat transfer rail thus forms a thermal bridge from the high-voltage circuit to the low-voltage area, via which the waste heat from the high-voltage circuit can be efficiently dissipated to the low-voltage area and from there to a heat sink.

[0022] This provides a way to efficiently cool a circuit carrier and thus a power electronic circuit arrangement with a low-voltage and a high-voltage circuit on the aforementioned circuit carrier.

[0023] For example, the first conductor track has a first conductor track section. Similarly, the heat transfer rail has a first rail section. The first conductor track section and the first rail section overlap vertically. In other words, the heat transfer rail partially overlaps the first conductor track vertically.

[0024] The partial overlaps of the heat transfer rail with the conductor track of the low-voltage circuit and the conductor track of the high-voltage circuit in the vertical direction create a short heat transfer path from the high-voltage circuit to the heat transfer rail and from the heat transfer rail to the low-voltage area.

[0025] For example, the heat transfer rail is also electrically conductive. In particular, the heat transfer rail is designed as a potential-free conductor track.

[0026] For example, the first conductor track section and the first rail section are arranged vertically spaced apart from each other. The circuit carrier between the first conductor track section and the first rail section has an insulating material for electrical isolation of the heat transfer rail from the first conductor track.

[0027] For example, the second conductor track section and the second rail section are arranged vertically spaced apart from each other. The circuit carrier between the second conductor track section and the second rail section has a further (or the same) insulating material for electrically isolating the heat transfer rail from the second conductor track.

[0028] The insulating material for electrical insulation can be the base material of the circuit carrier, such as a fiber-reinforced plastic or a ceramic, which is electrically well insulated and, for example, bonded together in the form of prepreg or ceramic layers. The two conductor tracks and the heat transfer strip can then be embedded between these prepreg or ceramic layers.

[0029] Because the heat transfer rail or its rail sections are arranged spatially spaced apart in the vertical direction from the conductor tracks or their conductor track sections in the vertical direction and are also electrically isolated from them by means of the insulating means, the low-voltage and high-voltage circuits are sufficiently electrically isolated from each other despite the electrically conductive heat transfer rail.

[0030] For example, the first conductor track has a first electrical connection for insulation measurement between the first conductor track and the heat transfer rail. Similarly, the heat transfer rail has a third electrical connection for insulation measurement between the first conductor track and the heat transfer rail. The first and third electrical connections for insulation measurement are permanently electrically connected to each other via a first high-resistance resistor with a resistance value of over 1 kilohm, over 10 kilohms, over 100 kilohms, over 1 megahm, or over 10 megahms. Alternatively or additionally to the resistor, the first and third electrical connections can also be electrically connected via a first controllable switch.

[0031] For example, the second conductor track has a second electrical connection for insulation measurement between the second conductor track and the heat transfer rail. Similarly, the heat transfer rail has a fourth electrical connection for insulation measurement between the second conductor track and the heat transfer rail. The second and fourth electrical connections for insulation measurement are permanently electrically connected to each other via a second high-resistance resistor with a resistance value of over 1 kilohm, over 10 kilohms, over 100 kilohms, over 1 megahm, or over 10 megahms. Alternatively, the second and fourth electrical connections can be switched electrically via a second controllable switch.

[0032] Due to the high-resistance connections to the first and second conductor tracks, the thermal interface material (TIM) can be used to verify the electrical insulation between these two tracks, and thus between the low-voltage and high-voltage circuits. The TIM enables verification of the electrical insulation between the low-voltage and high-voltage circuits, for example, immediately after the circuit carrier is manufactured or even during operation of the circuit assembly or carrier. The TIM can therefore replace a visual inspection of the electrical insulation, which would require additional components and is thus very complex.

[0033] The heat transfer rail can be used for insulation measurement against both the low-voltage potential of the low-voltage circuit and the high-voltage potential of the high-voltage circuit in order to detect a latent fault in one of the two insulation paths, i.e., a first insulation path between the heat transfer rail and the low-voltage circuit and a second insulation path between the heat transfer rail and the high-voltage circuit.

[0034] For example, the first conductor trace forms a ground connection (GND layer, current connection to ground) for the low-voltage circuit. Similarly, the second conductor trace forms a ground connection (GND layer, current connection to ground) for the high-voltage circuit.

[0035] For example, the circuit carrier also has a through-hole for inserting a (highly thermally conductive) fastening element, which serves to attach the circuit carrier to a housing or a heat sink of the circuit assembly and to transfer heat from the circuit carrier to the housing or the heat sink. The heat transfer element is at least partially formed around the through-hole.

[0036] For example, the heat transfer rail also has a vertical section that extends vertically along the circuit carrier and spatially isolates the low-voltage area from the high-voltage area. If the heat transfer rail has multiple layers, the vertical section physically connects these layers, thus also thermally and, if applicable, electrically. The vertical section can extend straight along the circuit carrier, but it can also be angled, curved, or extend in a stepped, wave-like, or zigzag pattern.

[0037] For example, the vertical section is formed in the form of a via in the circuit carrier.

[0038] The heat transfer rail, together with its conductor-like (busbar) layers and vertical section (especially in the form of a via), forms a continuous, non-potentially conductive network structure that extends holistically between the low-voltage and high-voltage circuits, spatially and thus electrically isolating the two circuits from each other, while thermally connecting them. Efficient heat transfer can be achieved through appropriate staggering of the heat transfer rail's network structure.

[0039] According to a second aspect of the invention, a power electronic circuit arrangement, in particular for a hybrid electric / electric vehicle, is provided.

[0040] The power electronic circuit arrangement comprises a previously described circuit carrier, a low-voltage circuit formed on and in the circuit carrier and comprising at least one first conductor track of the circuit carrier, and a high-voltage circuit also formed on and in the circuit carrier and comprising at least one second conductor track of the circuit carrier.

[0041] Advantageous embodiments of the circuit carrier described above, insofar as they are otherwise transferable to the power electronic circuit arrangement mentioned above, are also to be regarded as advantageous embodiments of the power electronic circuit arrangement. Brief description of the drawings:

[0042] Exemplary embodiments of the invention are explained in more detail below with reference to the accompanying drawings. These show: Fig. 1 in a first schematic perspective view a section of a first power electronic circuit arrangement with a section of a first circuit carrier according to a first exemplary embodiment of the invention; and Fig. 2 in a second schematic perspective view a section of a second power electronic circuit arrangement with a section of a second circuit carrier according to a second exemplary embodiment of the invention. Detailed description of the drawings:

[0043] Fig. Figure 1 shows in a first schematic perspective view a section of a first power electronic circuit arrangement SA with a section of a first circuit carrier ST according to a first exemplary embodiment of the invention.

[0044] The power electronic circuit arrangement SA is designed, for example, as an inverter and has a circuit carrier ST on which a low-voltage circuit of the circuit arrangement SA, such as a control circuit of the inverter, and a high-voltage circuit, such as a driver or bridge circuit of the inverter, are formed.

[0045] The circuit carrier ST has a carrier plate TP, which in this embodiment is designed as a multilayer printed circuit board with several prepreg layers PS of electrically insulating, flame-retardant, and fire-resistant composite materials consisting of epoxy resin and glass fiber fabric (FR-4). Between the prepreg layers PS, the circuit carrier ST has internal or embedded conductor layers for the low-voltage and high-voltage circuits.

[0046] The circuit carrier ST is roughly divided into three areas: a low-voltage area NB, a high-voltage area HB, and a boundary area AB. The boundary area AB at least partially surrounds the low-voltage area NB. The high-voltage area HB, in turn, at least partially surrounds the boundary area AB and thus the low-voltage area NB.

[0047] The low-voltage circuit is implemented in the low-voltage area NB. Among other things, the low-voltage circuit has at least one first internal conductor track LB1, which is embedded in the low-voltage area NB between two prepreg layers PS and forms part of a ground connection (GND layer, current connection to ground) of the low-voltage circuit.

[0048] Similarly, the high-voltage circuit is configured in the high-voltage area HB. Like the low-voltage circuit, the high-voltage circuit has, among other things, at least one second internal conductor track LB2, which is embedded in the high-voltage area HB between at least two (possibly partially additional) prepreg layers PS and forms part of another ground connection of the high-voltage circuit.

[0049] The boundary area AB is free of conductor traces, meaning it is free of any traces forming part of the low-voltage or high-voltage circuit. Therefore, boundary area AB spatially isolates the low-voltage area NB and the high-voltage area HB from each other, and thus also electrically isolates the low-voltage circuit and its conductor traces, such as the first conductor LB1, from the high-voltage circuit and its conductor traces, such as the second conductor LB2.

[0050] Within the boundary area AB, a heat transfer rail WS is arranged, which, like the conductor tracks LB1 and LB2, is embedded between the prepreg layers (PS). The heat transfer rail WS is made of the same material as the conductor tracks of the low-voltage circuit and the high-voltage circuit and is therefore designed as additional, potential-free conductor tracks embedded in multiple layers between the prepreg layers (PS). The heat transfer rail WS is not used for current or signal transmission and is therefore not part of the low-voltage or high-voltage circuit. Like the conductor tracks LB1 and LB2 of the low-voltage and high-voltage circuits, the heat transfer rail WS is a good thermal conductor and therefore primarily serves to transfer heat from the high-voltage area, and thus from the high-voltage circuit, to the low-voltage area, or rather, to the low-voltage circuit.For this purpose, the heat transfer rail WS has at least one first rail section WA1, which extends deep into the low-voltage area NB in ​​a horizontal direction HR of the circuit carrier ST (running parallel to the component surface of the circuit carrier ST). Furthermore, the heat transfer rail WS has at least one second rail section WA2, which extends deep into the high-voltage area HB in the horizontal direction HR. The first rail section WA1 overlaps the heat transfer rail WS with a first conductor track section LA1 of the first conductor track LB1 in a vertical direction VR of the circuit carrier ST (running perpendicular to the component surface of the circuit carrier ST). Thus, the heat transfer rail WS and the first conductor track LB1 partially overlap each other in the low-voltage area NB in ​​the vertical direction VR.The second rail section WA2 overlaps the heat transfer rail WS in the vertical direction VR with a second conductor section LA2 of the second conductor LB2. This means that the heat transfer rail WS and the second conductor LB2 partially obscure each other in the high-voltage area HB in the vertical direction VR. The first rail section WA1 and the first conductor section LA1 are spaced apart from each other in the vertical direction VR. At least one prepreg layer PS of the circuit carrier ST lies between the first rail section WA1 and the first conductor section LA1, electrically isolating the first rail section WA1 from the first conductor section LA1. Similarly, the second rail section WA2 and the second conductor section LA2 are spaced apart from each other in the vertical direction VR.Between the second rail section WA2 and the second conductor track section LA2, there is also at least one prepreg layer PS of the circuit carrier ST, which electrically insulates the second rail section WA2 from the second conductor track section LA2. The prepreg layers PS thus electrically insulate the heat transfer rail WS from the first and second conductor tracks LB1, LB2, and from the low-voltage circuit and the high-voltage circuit.

[0051] The heat transfer rail WS further comprises a vertical section VA extending in the vertical direction VR, which integrally connects the various layers or rail sections WA1, WA2. In addition, the vertical section VA, viewed in the horizontal direction HR, is positioned between the first and second conductor sections LA1, LA2, or between the first and second conductors LB1, LB2, thus spatially isolating the two conductors LB1, LB2 from each other in the horizontal direction HR. The vertical section VA therefore ensures electrical isolation between the two conductors LB1, LB2, and thus between the low-voltage and high-voltage circuits in the horizontal direction HR. The vertical section VA is formed as a via in the carrier plate TP and is physically and thus electrically connected to the layers or rail sections WA1, WA2 of the heat transfer rail WS.

[0052] The heat transfer rail WS, together with the rail sections WA1, WA2 and the vertical section VA, forms a continuous, non-potentially connected network structure that extends holistically between the conductor tracks LB1, LB2 of the low-voltage circuit and the high-voltage circuit, spatially and electrically isolating the two conductor tracks LB1, LB2 and thus the two circuits from each other.

[0053] The carrier plate TP, or circuit carrier ST, also has a through-hole DL that extends vertically VR through the entire carrier plate TP. The circuit carrier ST further includes a screw BM made of a metal alloy, such as iron, as a fastening element. This screw is inserted through the through-hole DL and is screwed to a housing GH of the circuit assembly SA, specifically to its wall, thus securing the circuit carrier ST to the housing GH. The through-hole DL is designed similarly to a via and has a copper layer on its wall, which is physically, and therefore electrically and thermally, connected to the second conductor track LB2. The housing GH is made of a metal alloy, such as an aluminum alloy, and serves, among other things, as an electrical ground and as a heat sink for cooling the circuit assembly SA.The first conductor track LB1 is at least partially formed around the through-hole DL. The heat transfer rail WS is in turn the first conductor track LB1 and the through-hole DL is at least partially formed around the entire perimeter.

[0054] The heat transfer rail WS, with its two rail sections WA1 and WA2 extending deep into the low-voltage area NB and the high-voltage area HB respectively, and overlapping with one of the two conductor tracks LB1 and LB2 or their conductor track sections LA1 and LA2, bridges the boundary area AB and thus thermally connects the high-voltage area HB with the low-voltage area NB. The heat transfer rail WS therefore improves heat transfer from the high-voltage circuit or the high-voltage area HB to the low-voltage area NB or to the first conductor track LB1. The waste heat generated during operation of the circuit arrangement SA in the high-voltage circuit is transferred via the second conductor track LB2 to the heat transfer rail WS, and from the heat transfer rail WS further to the second conductor track LB2. From the second conductor track LB2, this heat is dissipated via the screw BM in the through-hole DL to the housing GH.This ensures efficient cooling of the high-voltage circuit or circuit arrangement SA. Efficient heat transfer can be achieved through appropriate fanning of the network structure of the heat transfer rail WS.

[0055] Fig. Figure 2 shows in a second schematic perspective view a section of a second power electronic circuit arrangement SA with a section of a second circuit carrier ST according to a second exemplary embodiment of the invention.

[0056] The ST circuit carrier in Fig.Figure 2 features an electrically conductive heat transfer rail WS, which is multilayered with several layers (or strata) extending alternately deep into the low-voltage region NB or the high-voltage region HB in the horizontal direction HR. Each layer of the heat transfer rail WS has a first rail section WA1 or a second rail section WA2, which extends deep into the low-voltage region NB or the high-voltage region HB, respectively, and overlaps extensively in the vertical direction VR with a first conductor LB1 of the low-voltage circuit or its first conductor section LA1, or with a second conductor LB2 of the high-voltage circuit or its second conductor section LA2. The individual layers or rail sections WA1, WA2 of the heat transfer rail WS are separated from the respective conductors LB1, LB2, and LA2.The conductor track sections LA1 and LA2 are spatially and electrically separated by prepreg layers PS of the carrier plate TP. These prepreg layers PS are designed to be as thin as possible, providing just sufficient electrical insulation while simultaneously exhibiting the lowest possible thermal resistance. Due to their spatial proximity and vertical overlap VR, the individual layers or rail sections WA1 and WA2 of the heat transfer rail WS are thermally well coupled to the respective conductor tracks LB1 and LB2, or their conductor track sections LA1 and LA2.

[0057] Furthermore, the heat transfer rail WS is designed to be potential-free and also serves to check electrical insulation between the first and second conductor tracks LB1, LB2.

[0058] For this purpose, the first conductor track LB1 has a first electrical connection SA1 for insulation measurement between the first conductor track LB1 and the heat transfer rail WS. Similarly, the second conductor track LB2 has a second electrical connection SA2 for insulation measurement between the second conductor track LB2 and the heat transfer rail WS. The heat transfer rail WS, in turn, has a third electrical connection SA3 for insulation measurement between the first conductor track LB1 and the heat transfer rail WS, as well as a fourth electrical connection SA4 for insulation measurement between the second conductor track LB2 and the heat transfer rail WS. The electrical connections SA1, SA2, SA3, and SA4 can each be located directly on the first, second conductor track LB1, LB2, or directly on the heat transfer rail WS, or on other, in particular,The conductive traces are formed on the component surfaces OF of the carrier board TP, each physically and electrically connected to the respective conductive trace LB1, LB2, or the heat transfer rail WS (e.g., via vias). Furthermore, the circuit arrangement SA includes two resistors with a resistance value exceeding 100 kilohms. The first and third current connections SA1, SA3 are electrically connected to each other via one of the two resistors for insulation measurement between the first conductive trace LB1 and the heat transfer rail WS. Similarly, the second and fourth current connections SA2, SA4 are electrically connected to each other via the other of the two resistors for insulation measurement between the second conductive trace LB2 and the heat transfer rail WS. Due to the high resistances, there is no risk of uncontrolled current flow between the two conductive traces LB1, LB2, and thus between the low-voltage and high-voltage circuits.Optionally, the circuit arrangement SA also includes two controllable switches, each electrically connected in series to one of the two resistors and thus between the first conductor track LB1 and the heat transfer rail WS, or between the second conductor track LB2 and the heat transfer rail WS. These switches temporarily connect the high-resistance connections between the first conductor track LB1 and the heat transfer rail WS, or between the second conductor track LB2 and the heat transfer rail WS, for insulation measurement purposes.

[0059] For insulation testing, voltages are measured between the heat transfer rail WS and the first conductor track LB1, or between the heat transfer rail WS and the second conductor track LB2, and compared with the respective predefined reference voltages. If the measured voltages deviate significantly from the respective reference voltages, insulation faults between the heat transfer rail WS and the first conductor track LB1 or the second conductor track LB2 must be assumed.

Claims

[1] Circuit carrier (ST) for a power electronic circuit arrangement (SA), comprising: - a low-voltage area (NB) in which at least one first, in particular internal, conductor track (LB1) is arranged for the establishment of a first electrical connection of a low-voltage circuit of the circuit arrangement (SA); - a high-voltage area (HB) in which at least a second, in particular internal, conductor track (LB2) is arranged for the production of a second electrical connection of a high-voltage circuit of the circuit arrangement (SA); - a conductor-free boundary area (AB) between the low-voltage area (NB) and the high-voltage area (HB), which spatially isolates the low-voltage area (NB) from the high-voltage area (HB); and - a thermally conductive, in particular internal, heat transfer rail (WS) for heat transfer between the low-voltage area (NB) and the high-voltage area (HB), which is arranged in the boundary area (AB) and extends into the low-voltage area (NB) and / or the high-voltage area (HB), characterized by , that - the second conductor track (LB2) has a second conductor track section (LA2); - the heat transfer rail (WS) has a second rail section (WA2); and - the second conductor track section (LA2) and the second rail section (WA2) overlap in the vertical direction (VR). [2] Circuit carrier (ST) according to claim 1, wherein the heat transfer rail (WS) further comprises a vertical section (VA) extending in the vertical direction (VR) of the circuit carrier (ST) and spatially isolating the low-voltage area (NB) from the high-voltage area (HB). [3] Circuit carrier (ST) according to claim 2, wherein the vertical section (VA) is formed in the form of a via in the circuit carrier (ST). [4] Circuit carrier (ST) according to one of the preceding claims, wherein - the first conductor track (LB1) has a first conductor track section (LA1); - the heat transfer rail (WS) has a first rail section (WA1); and - the first conductor track section (LA1) and the first rail section (WA1) overlap in the vertical direction (VR). [5] Circuit carrier (ST) according to one of the preceding claims, wherein the heat transfer rail (WS) is further designed to be electrically conductive. [6] Circuit carrier (ST) according to claims 4 and 5, - wherein the first conductor track section (LA1) and the first rail section (WA1) are spaced apart from each other in the vertical direction (VR); - wherein the circuit carrier (ST) between the first conductor track section (LA1) and the first rail section (WA1) has an insulating medium (PS) for electrical isolation of the heat transfer rail (WS) from the first conductor track (LB1). [7] Circuit carrier (ST) according to one of the preceding claims and claim 5, - wherein the second conductor track section (LA2) and the second rail section (WA2) are spaced apart from each other in the vertical direction (VR); - wherein the circuit carrier (ST) between the second conductor track section (LA2) and the second rail section (WA2) has a further insulating material (PS) for electrical isolation of the heat transfer rail (WS) from the second conductor track (LB2). [8] Circuit carrier (ST) according to one of claims 5 to 7, wherein - the first conductor track (LB1) has a first power connection (SA1) for insulation measurement between the first conductor track (LB1) and the heat transfer rail (WS); - the heat transfer rail (WS) has a third electrical connection (SA3) for insulation measurement between the first conductor track (LB1) and the heat transfer rail (WS); - wherein the first (SA1) and the third (SA3) power connection for insulation measurement are permanently electrically connected to each other via a first high-resistance resistor with a resistance value of over 1 kilo-ohm, over 10 kilo-ohms, over 100 kilo-ohms or over 1 mega-ohm, or are switchably electrically connected via a first controllable switch. [9] Circuit carrier (ST) according to any one of claims 5 to 8, wherein - the second conductor track (LB2) has a second power connection (SA2) for insulation measurement between the second conductor track (LB2) and the heat transfer rail (WS); - the heat transfer rail (WS) has a fourth electrical connection (SA4) for insulation measurement between the second conductor track (LB2) and the heat transfer rail (WS); - wherein the second (SA2) and the fourth (SA4) power connection for insulation measurement are permanently electrically connected to each other via a second high-resistance resistor with a resistance value of over 1 kilo-ohm, over 10 kilo-ohms, over 100 kilo-ohms or over 1 mega-ohm, or are switchably electrically connected via a second controllable switch. [10] Circuit carrier (ST) according to one of the preceding claims, wherein the first conductor track (LB1) forms a ground current connection of the low-voltage circuit and / or the second conductor track (LB1) forms a ground current connection of the high-voltage circuit. [11] Circuit carrier (ST) according to one of the preceding claims, which further comprises a through-hole (DL) for inserting a fastening means (BM) for fastening the circuit carrier (ST) to a housing (GH) or a heat sink of the circuit arrangement (SA) and for heat transfer from the circuit carrier (ST) to the housing (GH) or the heat sink, wherein the heat transfer rail (WS) is formed at least partially circumferentially around the through-hole (DL). [12] Power electronic circuit arrangement (SA), comprising: - a circuit carrier (ST) according to one of the preceding claims; - a low-voltage circuit formed on and in the circuit carrier (ST) and comprising at least one first conductor track (LB1); - a high-voltage circuit formed on and in the circuit carrier (ST) and comprising at least one second conductor track (LB2).

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