ELECTRICAL SWITCHING DEVICE

Description

[0001] The invention relates to an electrical switching device, particularly designed for a motor vehicle and comprising a printed circuit board with a top side and a bottom side, wherein the printed circuit board extends in a longitudinal direction and in a transverse direction, comprising at least one electronic circuit breaker which is mounted on the top side of the printed circuit board, and comprising a first busbar which extends in the longitudinal direction and is electrically conductively connected to the at least one circuit breaker.

[0002] US 6,833,997 B1 discloses a printed circuit board assembly in which current-carrying circuit board traces between MOSFETs or the like and edge terminals are replaced by metal frame structures that also serve to perform a heat dissipation function. Each of the lead frames comprises a first planar portion bonded to the top surface of a MOSFET by a thermally conductive epoxy, and a second raised planar portion extending parallel to, but above, the circuit board surface in contact with a terminal head mounted on the edge. The lead frames may be provided with support legs as well as additional heat-dissipating fins.

[0003] WO 2018 / 111001 A1 discloses a power relay assembly comprising a support plate having at least one electrical element mounted on a surface thereof and containing a plastic material with heat dissipation and insulation properties; and at least one busbar electrically connected to the electrical element and partially embedded in the support plate. Because of these features, heat generated by the busbar and the electrical element is dissipated to the outside through the support plate, it is possible to prevent performance degradation due to heat and breakage of electronic components.

[0004] WO 2009 / 081769 A1 discloses a printed circuit board having a metal core and a terminal block comprising an insulating block body and a plurality of terminals for efficient heating and heat dissipation processes.

[0005] US 6,587,346 B1 discloses an electronic system and a housing comprising a base and a cover. A printed circuit board is installed on the base of the housing. At least one solder pad is arranged on the printed circuit board for receiving an electronic component. The solder pad provides both an electrical connection and mechanical support for the electronic component. The electronic system is also provided with a device capable of distributing power to the electronic component while simultaneously dissipating heat from the electronic component. The device is also mounted on the solder pad and positioned adjacent to the electronic component.

[0006] A motor vehicle's electrical system typically includes a number of devices for controlling the supply of electrical energy to various consumers and, in particular, for distributing electrical power within the vehicle's electrical system. Various designations are commonly used for such devices, some of which also represent specific embodiments. Common designations include control device, control unit, control device, power distributor, power distributor, switching device, switching unit, fuse box, fuse unit, etc.

[0007] Control or distribution is typically achieved using semiconductor switches, which generate waste heat or heat loss when current flows through them. This heat loss leads to self-heating of the semiconductor switches, which can reduce their service life and / or lead to damage to the semiconductor switches or surrounding components. For this reason, measures are typically taken to dissipate the generated heat loss.

[0008] This applies particularly to semiconductor switches designed to switch high currents. For example, EP 2 043 412 B1 describes an electrical control unit for a motor vehicle that uses several semiconductor switches designed as so-called SMD components. The heat loss from these semiconductor switches is dissipated by means of a heat sink with cooling fins, which is thermally conductively connected to the SMD components.

[0009] Based on this, the invention is based on the object of specifying an advantageously designed electrical switching device.

[0010] This object is achieved according to the invention by an electrical switching device having the features of claim 1. Preferred developments are contained in the dependent claims.

[0011] The electrical switching device according to the invention is preferably designed for a motor vehicle and intended for implementing an on-board electrical system in a motor vehicle. The electrical switching device, which is also referred to below as the switching device for short, is typically configured to control the supply of electrical energy to various consumers and, in particular, to distribute electrical power in an on-board electrical system of a motor vehicle.

[0012] The electrical switching device comprises a printed circuit board or circuit board. Furthermore, the switching device comprises at least one electronic power switch, which is mounted on a top side of the printed circuit board and thus essentially forms at least part of the circuit board's components.

[0013] The power switch is typically designed as a so-called SMD component (SMD: surface-mounted device). Independently of this, the power switch usually has a semiconductor switch, for example a so-called MOSFET (metal oxide semiconductor field-effect transistor), or is formed by such a semiconductor switch.

[0014] Such circuit breakers typically have electronics housed in a housing made of insulating material, from which contact pads protrude, designed to connect the electronics to the circuit board. These contact pads, also called contact pins, are also referred to below as connecting arms. The housing, for example, is a molded housing.

[0015] The printed circuit board has an extension in a longitudinal direction and a transverse direction, wherein the longitudinal direction and the transverse direction are typically oriented perpendicular to each other. Furthermore, the circuit breaker is mounted on the printed circuit board such that a front side of the circuit breaker faces the top side of the printed circuit board and a rear side of the circuit breaker faces away from the top side of the printed circuit board.

[0016] Furthermore, a first busbar is part of the electrical switching device, which extends in the longitudinal direction. The first busbar is electrically connected to the at least one circuit breaker. Depending on the design variant, the connection is implemented as a direct connection, i.e., as contacting, for example, via a solder joint, or as an indirect connection, for example, via a conductor track or conductor structure on the circuit board. The circuit breaker typically has contact feet via which it is connected to the circuit board and via which it is electrically contacted.

[0017] The first busbar is arranged on the top side or in the region of the top side of the printed circuit board. It has a central region which forms a covering section and which – viewed in the direction of a surface normal to the top side of the printed circuit board – runs above the at least one electronic circuit breaker. This section then essentially covers or roofs over the at least one electronic circuit breaker. When multiple circuit breakers are used, the central region covers all circuit breakers, for example in a strip-like manner. As a result, the central region and the rear side of the at least one circuit breaker ultimately lie opposite one another and / or touch one another. The circuit breaker is therefore arranged between the printed circuit board and the first busbar.

[0018] For improved heat dissipation, the first busbar is thermally conductively connected to the at least one circuit breaker, in particular such that at least a portion of the waste heat or heat loss from the circuit breaker can be dissipated via the rear of the circuit breaker to the first busbar and is also dissipated during operation. This thermally conductive connection is an additional connection in addition to the electrical connection between the first busbar and the at least one circuit breaker. The dissipation or removal of the waste heat occurs at least primarily through thermal conduction.

[0019] This provides additional heat dissipation via the rear side of the circuit breaker. This contrasts with the prior art arrangement, in which heat dissipation occurs via the front side facing the circuit board and via a separate cooling structure. The heat dissipation via the rear side described here preferably supplements heat dissipation via the front side of the circuit breaker facing the circuit board. Overall, this achieves improved heat dissipation, keeping the thermal load on the circuit breaker low during operation.

[0020] The first busbar is preferably made of a metal, such as aluminum or copper, or of a metal alloy. The busbar is preferably formed as a single piece, i.e., virtually monolithic. It is formed, for example, from a stamped and bent sheet. The first busbar typically has a minimum cross-section of at least 10 mm². A minimum cross-section of 20 mm² and, in particular, a minimum cross-section of at least 30 mm² is also preferred. Irrespective of this, the current-carrying capacity of the first busbar in most applications is at least 50 A, preferably at least 100 A, and more preferably at least 150 A.

[0021] The at least one circuit breaker, in turn, is typically designed for conducting or switching currents with a current intensity of at least 5 A and preferably at least 10 A. Furthermore, in most embodiments of the switching device, multiple circuit breakers, typically more than 5 circuit breakers, and in particular multiple circuit breakers of the same type, are provided, which are then preferably mounted on the top side of the printed circuit board. These circuit breakers are typically interconnected in parallel, so that by synchronously controlling the circuit breakers, total currents of typically greater than or equal to 50 A, preferably greater than or equal to 100 A, and in particular greater than or equal to 150 A can be switched through.

[0022] For the thermally conductive connection between the first busbar and the at least one circuit breaker, a heat-conducting element is preferably provided, which is designed as a physical body. The heat-conducting element serves as a type of thermal bridge, via which waste heat or heat loss generated in the circuit breaker is transferred from the circuit breaker to the first busbar. The heat-conducting element lies flat against the circuit breaker, in particular flat against its insulating housing, on the one hand, and flat against the first busbar, on the other hand. The heat-conducting element ensures advantageous thermal connection. It is typically formed from a solid material, which in particular at least partially and preferably completely fills an intermediate space. The intermediate space is formed between the circuit board and / or the circuit breaker and the first busbar.Specifically, the term "gap" refers to a vertical free space in the direction of a surface normal of the circuit board or circuit breaker. This means that the gap between, in particular, the central region of the first busbar and the rear side of the at least one electronic circuit breaker is at least partially, and preferably completely, filled by the solid. As an alternative to a solid, a pasty substance can also be used.

[0023] Typically, several, for example, similar electronic circuit breakers are arranged longitudinally next to one another on the top side of the printed circuit board. Each of these circuit breakers is thermally connected to the first busbar, preferably via a heat-conducting element and in particular via a common heat-conducting element.

[0024] For a particularly good heat connection, the first busbar is embedded in the heat-conducting element in a preferred embodiment at least in the area of ​​the at least one circuit breaker and in particular in the area of ​​all circuit breakers.

[0025] Whenever reference is made to a heat-conducting element, this refers in particular to an element made of an electrically insulating material. Therefore, no electrically conductive connection is established via the heat-conducting element.

[0026] Preferably, the heat-conducting element is formed by a cured casting compound, for example a plastic or an epoxy resin.

[0027] As an alternative to the potting compound, the heat-conducting element is formed, for example, by a paste, an adhesive or a film, in particular an adhesive film.

[0028] The heat-conducting element preferably extends up to, and in particular only up to, the top side of the printed circuit board. Specifically, all components arranged above the top side of the printed circuit board are embedded in the heat-conducting element. This particularly applies to the circuit breakers and the first busbar, at least its central region. The printed circuit board therefore delimits the heat-conducting element, which is specifically designed as a cast compound, on one side. The opposite underside of the printed circuit board, and with it, in particular, a second busbar arranged there, is not embedded in the heat-conducting element.

[0029] The heat-conducting element expediently has a thermal conductivity greater than 0.15 W / mK. A preferred embodiment is one in which the thermal conductivity is greater than or equal to 0.3 W / mK or in which the thermal conductivity is greater than or equal to 0.8 W / mK. Typically, the thermal conductivity is in a range between 0.2 W / mK and 0.5 W / mK or in a range of 1-10 W / mK.

[0030] Preferably, a flank region with at least one connecting arm, which is particularly designed in the manner of a contact pin or contact pin, adjoins the middle region of the first busbar on at least one side as viewed in the transverse direction. The electrical contact between the circuit breaker and the printed circuit board is made via this flank region. As viewed in the transverse direction, the connecting arm is guided laterally past the circuit breaker next to the at least one circuit breaker. As a result, the circuit breaker is enclosed on at least two sides via the busbar for good heat dissipation. The distance in the transverse direction between the at least one connecting arm and the at least one circuit breaker is preferably smaller than the extension of the circuit breaker in the transverse direction, in particular smaller than 0.5 times the extension.

[0031] Preferably, connecting arms are arranged on both sides of the central region, so that the first busbar forms a U-shaped structure—at least when viewed longitudinally on an image plane when projected longitudinally. The at least one and preferably several circuit breakers arranged consecutively in the longitudinal direction are arranged within this U-shaped structure. Preferably, several connecting arms are arranged on each side, for example, in a row. These connecting arms each form a flank region, which is configured, for example, in the shape of a comb.

[0032] The connecting arms and in particular the two flank areas are preferably arranged offset from one another in the longitudinal direction. In this case in particular, the first busbar then has a number of connecting arms or contact pins on each of two opposite edges. The circuit breakers are then further preferably arranged in two groups, with the circuit breakers in one group usually rotated by 180° relative to the circuit breakers in the other group. This serves, for example, to distribute the current load across the entire width of the first busbar. Depending on the length of the circuit breakers, which are preferably arranged in series, this 180° arrangement serves to compensate for tolerances and thermal expansion, to distribute stress, and to geometrically stabilize the assembly before soldering. An opposite arrangement is also expedient, for example, depending on the installation space requirements with the same surface area.The arrangement also depends on common part concepts with assembly variants, so it can mean a reduced number of equipped circuit breakers even with the same busbar. The temporal behavior under load can then be adapted to the requirements.

[0033] Preferably, the heat-conducting element completely fills an intermediate space between the at least one circuit breaker, in particular between the plurality of circuit breakers, and the first busbar. In this embodiment, the intermediate space is delimited on one side by the central region of the first busbar and on another side by at least one of the previously described connecting arms. The intermediate space is thus composed of the previously described vertical free space and, in addition, a lateral free space. Therefore, the heat-conducting element preferably fills the intermediate space, which—viewed in longitudinal projection—is delimited by the opposing connecting arms and the central region.

[0034] The switching device further comprises a second busbar arranged on an underside or in the region of the underside of the printed circuit board. The second busbar preferably lies directly against the underside of the printed circuit board. The second busbar is also electrically connected to the at least one electronic circuit breaker. Analogous to the first busbar, the electrical connection is implemented as a direct or indirect connection, depending on the application. Electrical contact is made with a power input via one of the busbars, and contact is made with a power output of the respective circuit breaker via the other busbar.

[0035] The second busbar, like the first busbar, is designed for high currents of, for example, at least 50 A and more preferably at least 100 A. It is made in particular of metal and is designed, for example, as a stamped and bent sheet. Overall, therefore, a type of sandwich construction is implemented in the electrical switching device, in which the at least one circuit breaker mounted on the printed circuit board or the plurality of circuit breakers typically arranged in one plane is / are positioned in an area between the first busbar and the second busbar and in which waste heat or heat loss can be dissipated in two opposite directions, namely once towards the first busbar and once towards the second busbar, and is also dissipated during operation.

[0036] In particular, the switching device has only a single printed circuit board, on the opposite sides of which the two busbars run with the circuit breakers in between.

[0037] The second busbar is also thermally conductively connected to the at least one circuit breaker. The heat from the circuit breaker is therefore dissipated via both busbars. For this purpose, the second busbar is preferably thermally conductively connected to a front side of the component, which is oriented toward the printed circuit board, in particular independently of the electrically conductive connection. For the thermally conductive connection, the second busbar either directly contacts the circuit breaker, i.e., in particular, its housing. Alternatively, a heat-conducting element is provided for thermal coupling with the circuit breaker.

[0038] To form the particularly direct thermally conductive connection between the second busbar and the at least one circuit breaker, the printed circuit board preferably has an opening in the region of the at least one circuit breaker. The second busbar additionally has a pin, which is produced, for example, by bending, and which dips into the opening or passes through it. The pin lies on the circuit breaker, in particular directly, or alternatively via an additional heat-conducting element, such as a heat-conducting paste. The heat-conducting element is in turn preferably an element made of an electrically insulating material. The thermally conductive connection is thus formed via this pin with the front side of the at least one circuit breaker oriented towards the printed circuit board. It is preferably merely a thermally conductive connection, without an electrically conductive connection being made. D.i.e. the pin preferably only provides a thermally conductive connection to an insulating housing of the respective circuit breaker.

[0039] Preferably, the pin is pressed into the opening and thus mechanically attached to the circuit board. The pin is preferably held exclusively by a press fit. Alternatively or additionally, the pin can be glued or soldered to the circuit board, for example.

[0040] Preferably, the printed circuit board has such an opening in the area of ​​each circuit breaker and the second busbar has a corresponding pin for each circuit breaker.

[0041] A heat sink, particularly a finned one, can also be arranged on the second busbar. However, in this case, a heat sink is preferably omitted. Heat dissipation occurs exclusively via the two busbars.

[0042] The second busbar is preferably designed as a power input for connection to a power source or for connection to a power source. When the electrical switching device is installed in a motor vehicle's on-board power supply system, the second busbar therefore forms such a power input. The power source is formed, for example, by a motor vehicle battery or by an electric generator. In addition, the first busbar is typically designed as a power output and, when the switching device is installed, forms a corresponding power output. When installed, one or more load current paths, each with at least one electrical consumer, are connected to a corresponding power output.

[0043] The electrical switching device is, in particular, a so-called pre-fuse box for a motor vehicle. The printed circuit board, including its components, in particular the circuit breakers mounted on it, the two busbars (i.e., the first busbar and the second busbar), and the heat-conducting element form an electronic fuse unit, which is, in particular, designed as an eFuse, i.e., as an electronic fuse. The electronic fuse unit is thus preferably configured or designed as a type of circuit breaker.

[0044] The electrical switching device preferably has, in addition to the electronic fuse unit, further load connections, each of which is protected by a fuse element, for example a fuse. In the assembled state, further load paths with consumers are connected to these load connections. At least one or more, in particular two, high-current paths are supplied via the electronic fuse unit. These are used to supply high-performance components such as EKMV (electric coolant supply / electric water pump), eKat (catalytic converter heater) or similar components. These high-current paths are designed for higher currents than the other load paths. For example, a total of over 100A is provided to the high-current paths via the electronic fuse unit, with each high-current path having at least 30A. Each of the other load paths, in contrast, is provided with a lower current value, e.g.protected with 10A or 20A.

[0045] Embodiments of the invention are explained in more detail below with reference to a schematic drawing. In the drawing: FIG 1 shows a perspective view of a backup fuse box, FIG 2 shows a perspective view of a distribution rail and an electronic fuse unit connected thereto, FIG 3 shows a perspective view of the electronic fuse unit comprising a printed circuit board with several circuit breakers, two busbars and a heat-conducting element, FIG 4 shows a perspective view of the electronic fuse unit similar to FIG 3 without the heat conducting element, FIG 5 in a perspective view of the printed circuit board with the circuit breakers, FIG 6 in a side view of the electronic fuse unit without the heat conducting element and FIG 7 in a partial cross-section of the electronic fuse unit.

[0046] Corresponding parts are provided with the same reference numerals in all figures.

[0047] An example described below in FIG 1 The electrical switching device shown is designed as a so-called pre-fuse box 2 for a motor vehicle and is accordingly intended for use in an on-board electrical system of a motor vehicle.

[0048] For a simpler description of the backup fuse box 2, the diagrams in the FIG 1 bis FIG 7 Three orthogonal spatial directions are shown, namely a vertical direction 4, a longitudinal direction 6 and a transverse direction 8.

[0049] The FIG 1 The fuse box 2 shown has a distribution rail 10 (cf. Fig. 2 ), via which an input connection 12 and several output connections 14, 16, 18 for the pre-fuse box 2 are realized. The individual connections 12 to 18 differ in the exemplary embodiment with regard to the current carrying capacity for which the individual connections 12 to 18 are designed. The input connection 12 is designed for the highest current carrying capacity and, for example, for several 100 A. Furthermore, all of these connections 12 to 18, i.e. the input connection 12 and the output connections 14 to 18, are arranged within a housing 20 of the pre-fuse box 2. In the installed state of the pre-fuse box 2, cables 22 connected to the connections 12 to 18 are led out of the housing 20, as shown in FIG 1 is indicated.

[0050] In FIG 2 The pre-fuse box 2 is shown without the housing 20 and without connected cables 22. From this illustration, at least in conjunction with the other illustrations, it can be seen that in the pre-fuse box 2, all connections 12 to 18 are designed as fused connections 12 to 18, with a first output connection 14 and a second output connection 16 being protected by an electronic fuse unit 24, and the other output connections 18 and the input connection 12 each being protected by integrated fuses 26.

[0051] The structure of the electronic security unit 24 or security unit 24 for short is described in connection with the FIG 3 bis FIG 7 explained in more detail. It has a first busbar 32 and a second busbar 28. The second busbar has a power input with an input terminal 30 and, in the exemplary embodiment, two output terminals, namely the first output terminal 14 and the second output terminal 16. The input terminal 30 and the two output terminals 14, 16 are each designed as bent L-shaped tabs that have a screw hole. In the exemplary embodiment, the input terminal 30 of the electronic fuse unit 24 is electrically conductively connected, for example, screwed, to a secondary arm of the distribution bar 10 and thus to the input terminal 12.

[0052] The security unit 24 has a in detail in FIG 5 , which extends in the longitudinal direction 6 on the one hand and in the transverse direction 8 on the other. Mounted on a top side 36 of the printed circuit board 34 are a plurality of electronic power switches 38, which thus form at least part of the components of the printed circuit board 34. The power switches 38 have a front side 40 facing the printed circuit board 34 and an opposite rear side 42 facing away from the printed circuit board 34. Furthermore, the power switches 38 are arranged in a row running in the longitudinal direction 6.

[0053] The power switches 38 are typically designed as so-called SMD components (SMD: surface-mounted device). Independently of this, each power switch 38 typically has a semiconductor switch, for example, a so-called MOSFET (metal oxide semiconductor field-effect transistor), or is formed by such a semiconductor switch.

[0054] The first busbar 32 is arranged above the printed circuit board 34 and thus faces the upper side 36 of the printed circuit board 34, as can be seen in particular from the FIG. 4 and 6 The first busbar has a central region 44 extending in the longitudinal direction 6, which covers or roofs the circuit breakers 38. As can be seen from FIG 6 As can be seen, there is a distance between the rear sides 42 of the circuit breakers 38 and the central region 44. The central region 44 thus does not touch the rear sides 42 of the circuit breakers 38 in the exemplary embodiment. Therefore, a vertical clearance or gap is formed between an upper side of the circuit breaker 38 and the first busbar 32.

[0055] Furthermore, the first busbar 32 in the exemplary embodiment has two flank regions 46, 48, namely a first flank region 46 and a second flank region 48, which adjoin the central region 44 on both sides as seen in the transverse direction 8. Each of the two flank regions 46, 48 is designed as a comb-like structure with several pin-like connecting arms 50 that extend along the vertical direction 4 toward the printed circuit board 34. The vertical direction 4 forms a normal to the printed circuit board 34. The two flank regions 46, 48, together with the central region 44, form a U-shaped structure, at least when the first busbar is projected in the longitudinal direction 6 onto an image plane (cf. FIG 6 ).

[0056] In addition, the printed circuit board 34 has a receptacle 52 for each connecting arm 50. In the exemplary embodiment, the receptacles are formed by openings in the printed circuit board 34 into which the connecting arms 50 are inserted. The openings forming the receptacles 52 are penetrated by the connecting arms 52 ( FIG 6 ). Each connecting arm 50 is, for example, pressed and / or soldered into the corresponding receptacle 52, so that the first busbar is fixed to the printed circuit board 34 via the connecting arms 50. Furthermore, in the exemplary embodiment, the connecting arms 50 are electrically connected to the circuit breakers 38, for example, via conductor tracks of the printed circuit board 34 (not shown here).

[0057] Furthermore, the fuse unit 24 has the second busbar. This is arranged on a bottom side 56 of the printed circuit board 34 and thus on a side opposite the first busbar 32. As specifically shown in Fig. 4 or FIG. 6 und FIG 7 As can be seen, the circuit breakers 38 and the printed circuit board 34 are sandwiched between the two busbars 28,32.

[0058] The second busbar also has a central region 54 extending in the longitudinal direction 6, which in the exemplary embodiment rests on the underside 56 of the printed circuit board 34.

[0059] The second busbar is also electrically conductively connected to the power switches 38 in a manner not shown in detail, whereby a current supplied via the input terminal 30 and thus via the second busbar can ultimately be switched through via the power switches 38 to the first busbar 32 and to the two output terminals 14, 16. Each power switch 38 is usually designed to conduct or switch through currents with a current intensity of at least 5 A and preferably at least 10 A. Furthermore, in the exemplary embodiment, the power switches 38 are connected to one another in a parallel circuit, so that by synchronously controlling the power switches 38, a total of currents greater than or equal to 50 A and in particular greater than or equal to 100 A can be switched through.

[0060] To form a thermally conductive connection between the first busbar 32 and the circuit breakers 38, a thermally conductive connection is formed in the exemplary embodiment using an additional heat-conducting element 62. The heat-conducting element 62 serves as a type of thermal bridge, via which waste heat or heat loss generated in the circuit breakers 38 is transferred to the first busbar 32.

[0061] The heat-conducting element 62 is preferably formed by a cured potting compound, for example, a plastic or an epoxy resin. Preferably, the first busbar 32 is embedded in the heat-conducting element 62 at least in the area of ​​the circuit breaker 38. The heat-conducting element 62 formed by the potting compound preferably covers the entire printed circuit board 34. During manufacture, therefore, the Fig. 4 The potting compound is applied to the unit shown. The first busbar 32 is, in particular, completely embedded in the potting compound, except for the angled terminals 14, 16, 30.

[0062] At the same time, the printed circuit board 34 defines the heat-conducting element 62, i.e., the heat-conducting element 62 extends only to one side of the printed circuit board 34 without being embedded in the potting compound. In particular, the second busbar 28 arranged on the opposite side of the printed circuit board 34 is exposed and not surrounded by the potting compound.

[0063] Regardless of the precise design of the heat-conducting element, it expediently has a thermal conductivity greater than 0.15 W / mK. A preferred embodiment is one in which the thermal conductivity is greater than or equal to 0.3 W / mK or in which the thermal conductivity is greater than or equal to 0.8 W / mK. Typically, the thermal conductivity is in a range of 1-10 W / mK.

[0064] In the exemplary embodiment, the heat-conducting element 62 fills, among other things, a gap 64 which is bounded on one side by the central region 44, on another side by the first flank region 46, on another side by the second flank region 48 and on another side by the printed circuit board 34 together with its components, which in particular also include the power switches 38 mounted on the printed circuit board 34. The outline of the heat-conducting element 62 is shown in FIG 6 represented by dashed lines.

[0065] For the thermally conductive connection of the second busbar 28 and the circuit breakers 38, the printed circuit board 34 in the exemplary embodiment has an opening 58 in the area of ​​each circuit breaker 38, which is covered by the associated circuit breaker 38 on the top side 36 of the printed circuit board 34. In addition, the second busbar 28 has a pin 60 for each circuit breaker 38, which is produced, for example, by bending, and each pin 60 at least partially penetrates the associated opening 58 in the printed circuit board. The thermally conductive connection is formed between the front sides 40 of the circuit breakers 38 and the pins 60, with each pin 60 resting against the front side 40 of the associated circuit breaker 38. This is FIG 7 can be found. FIG 7shows a partial sectional view of the fuse unit at the level of a circuit breaker. It is also advantageous if the second busbar is also mechanically fastened to the circuit board 34, for example, by pressing the pins 60 into the openings 58, with the pressing being achieved, for example, by means of clinching.

[0066] In particular, only a thermal coupling is achieved via the pin 60, without any electrical contact being established. Electrical connections (not shown in detail here) are provided for the electrical contacting of the circuit breakers 38 with the second busbar 28, e.g., vias in the printed circuit board 34, to which corresponding contact feet of the circuit breakers 38 are then connected.

[0067] The design described here achieves particularly efficient heat dissipation during operation. The first busbar 32 and its thermal connection via the potting compound (heat-conducting element 62) to the rear of the circuit breaker 38 provide heat dissipation, particularly in addition to heat dissipation via the front side and the second busbar 28.

[0068] Studies have shown that this results in lower operating temperatures during operation.

[0069] If the pre-fuse box 2 is installed in a motor vehicle and thus part of the vehicle's electrical system, the input connection 12 is connected, for example, to a belt-driven starter generator (RSG), which typically feeds up to 190 A into the pre-fuse box 2 during operation. The output connection 14 is then connected, for example, to an electrical coolant supply (EKMV), which typically has a current requirement of up to 120 A during operation. The output connection 16 is connected, for example, to a catalytic converter heater (e-Kat), which typically has a current requirement of up to 40 A during operation. Components such as an electrical auxiliary heater (PTC), a battery / accumulator or the like are usually connected to the output connections 18. List of reference symbols

[0070] 2 Electrical switching device 4 Vertical direction 6 Longitudinal direction 8 Transverse direction 10 Distribution bar 12 Input connection 14 First output connection 16 Second output connection 18 Further output connection 20 Housing 22 Cable 24 Electronic fuse unit 26 Fuse 28 Second busbar 30 Input connection 32 First busbar 34 Printed circuit board 36 Top of the printed circuit board 38 Electronic circuit breaker 40 Front of the electronic circuit breaker 42 Rear of the electronic circuit breaker 44 Center area of ​​the first busbar 46 First flank area 48 Second flank area 50 Connecting arm 52 Receptacle 54 Center area of ​​the second busbar 56 Bottom of the printed circuit board 58 Cutout 60 Pin 62 Heat-conducting element 64 Space

Claims

1. Electrical switching device (2), in particular configured for a motor vehicle and comprising - a printed circuit board (34) with a top side (36) and a bottom side (56), wherein the printed circuit board (34) extends in a longitudinal direction (6) and in a transverse direction (8), - at least one electronic power switch (38) which is fitted on the top side (36) of the printed circuit board (34), as well as - a first busbar (32) which extends in the longitudinal direction (6) and is electrically-conductively connected to the at least one power switch (38), wherein - the first busbar (32) is arranged on the top side (36) of the printed circuit board (34) and has a central region (44) which runs above the at least one electronic power switch (38), and - the first busbar (32) is thermally-conductively connected to the at least one power switch (38). characterized in that - a second busbar (28) is arranged on the bottom side (56) of the printed circuit board (34), which is also electrically-conductively connected to the at least one electronic power switch (38), and - the second busbar (28) is also thermally-conductively connected to the at least one power switch (38).

2. Electrical switching device (2) according to claim 1, characterized in that the first busbar (32) is thermally-conductively connected to the at least one power switch (38) via a heat-conducting element (62).

3. Electrical switching device (2) according to claim 2, characterized in that a plurality of electronic power switches (38) are arranged in the longitudinal direction (6) next to one another on the top side (36) of the printed circuit board (34) and that the first busbar (32) is thermally-conductively connected to each electronic power switch (38), in particular via the heat-conducting element (62).

4. Electrical switching device (2) according to any one of claims 2 or 3, characterized in that the first busbar (32) is embedded in the heat-conducting element (62) in the region of the at least one electronic power switch (38).

5. Electrical switching device (2) according to any one of claims 2 to 4, characterized in that the heat-conducting element (62) is formed by a hardened casting compound.

6. Electrical switching device (2) according to any one of claims 2 to 5, characterized in that the heat-conducting element (62) extends only to the top of the printed circuit board (34), such that the latter is not embedded in the heat-conducting element (62).

7. Electrical switching device (2) according to any one of claims 2 to 6, characterized in that the heat-conducting element (62) has a thermal conductivity which is greater than 0.15 W / mK, and in particular greater than 0.8 W / mK.

8. Electrical switching device (2) according to any one of the preceding claims, characterized in that at least one connecting arm (50) laterally adjoins the middle region (44), via which the first busbar (32) is connected to the printed circuit board (34), wherein the at least one connecting arm (50) is laterally guided past the electronic power switch (38) next to the electronic power switch (38), as viewed in the transverse direction (8).

9. Electrical switching device (2) according to claim 8, characterized in that, as viewed in the transverse direction (8), at least one connecting arm (50) adjoins the central region (44) on both sides, such that the central region (44) and the connecting arms (50) - as viewed in a projection of the first busbar (32) in the longitudinal direction (6) - form a U-shaped structure.

10. Electrical switching device (2) according to any one of claims 8 or 9 and according to any one of claims 2 to 7, characterized in that the heat-conducting element (62) completely fills an intermediate space (64), which is delimited on one side by the central region (44) and preferably further on a further side by the at least one connecting arm (50).

11. Electrical switching device (2) according to any one of claims 1 to 10, characterized in that the second busbar (28) is connected to a power input and the first busbar (32) is connected to a power output of the at least one power switch (38).

12. Electrical switching device (2) according to any one of claims 1 to 11, characterized in that the printed circuit board (34) has an opening (58) in the region of the at least one power switch (38) and the second busbar (28) has a pin (60), and that the pin (60) at least partially penetrates the opening (58) such that the second busbar (28) is attached to the printed circuit board (34) in particular by pressing.

13. Electrical switching device (2) according to any one of claims 1 to 12, characterized in that the second busbar (28) is configured as a power input for connection to a power source, in particular a motor vehicle battery, and that the first busbar (32) is configured as a power output for connection to at least one consumer.

14. Electrical switching device (2) according to any one of claims 1 to 13, characterized in that it is configured as a backup fuse box (2) for a motor vehicle, in which the printed circuit board (34) together with the power switches (38) fitted thereon, form an electronic fuse unit (24) with the two busbars (28, 32), and in which a plurality of load current paths (18) are additionally arranged, each of which is secured via a fuse element (26), each of which is configured to connect with an electrical line (22).