Arrangement for dissipating electrical heat losses from an electrical power component

Abstract

An arrangement for dissipating electrical heat losses from an electrical power component, having an electrical power component which is provided with an insulating housing and is thermally coupled via the latter to a cooling channel, is characterized according to the invention in that the thermal coupling is effected by means of a heat spreading element which on the one hand lies flat against a main surface of the housing and on the other hand is fastened directly to the cooling channel.

Description

[0001] Arrangement for dissipating electrical waste heat from an electrical power component

[0002] The invention relates to an arrangement for dissipating electrical waste heat from an electrical power component, comprising an electrical power component which is provided with an insulating housing and is thermally coupled to a cooling channel via this housing.

[0003] In power electronics and in the design of electric cars, there is a trend away from the "converted combustion engine" where the conventional powertrain was simply replaced by an electric powertrain with a battery pack, towards so-called purpose design, where the electric car is developed around the electric powertrain and the battery pack.

[0004] This new package also creates new synergies that didn't exist before. A few years ago, all devices that had to dissipate significant heat were equipped with their own water cooling systems. Now, there are efforts to centralize the cooling to reduce pumping losses and, above all, expensive interfaces. The battery pack installed in the underbody has proven to be a suitable location for this cooling. The battery cells need to be pre-tempered at low ambient temperatures and cooled down during operation, at high ambient temperatures, or during charging. Typically, the battery cells are located in the vehicle underbody, with the cooling channel directed towards the passenger compartment. This provides a large-area cooling channel that can also be fitted with power electronics from above.

[0005] Using this single cooling channel for the power electronic components as well offers the advantage of reduced pressure loss in the cooling system (requiring less pump power and improving the overall efficiency of the vehicle), as well as potential savings on hoses and expensive waterproof connectors. It also reduces the risk of leaks. However, this is offset by the challenge of dissipating the sometimes significant power losses via an additional thermal interface to the cooling channel. Each thermal interface is like a resistor in a series circuit, and depending on the amount of power that needs to be dissipated and the surface area, an additional thermal interface can lead to thermal overload and thus system failure.

[0006] Therefore, housing concepts must be completely rethought to meet these requirements in order to ensure optimal cooling of the power electronic components even under these limited cooling options.

[0007] The thermal resistance of the transmission path between the electrical component generating electrical waste heat and the associated cooling device is significantly influenced by several factors.

[0008] A key influencing factor is the cooling surface of the electrical component. While all materials exhibit some degree of heat spreading, where heat is distributed not only across the thickness of the thermal interface but also horizontally, the goal is to minimize thermal paths and material usage. This often results in thin layers or flat structures like sheets, which are barely capable of distributing heat effectively across the surface.

[0009] Another factor is the path of the heat to the heat sink, particularly the thermal interfaces that must be overcome. The need for tolerance compensation and minimum dimensions of the individual components in the thermal resistance chain limits optimization in this area. If the cooling layer is moved further away from the heat source, as in the concept of centralized cooling, additional thermal resistances arise.

[0010] Last but not least, the thermal conductivities of the individual materials used also play a role. Filler materials, such as gap fillers, are used for thermal bonding. These typically have thermal conductivities of 1 to 5 W / (m*K). Above this value, the materials become prohibitively expensive according to the current state of the art, so their use is only economical in specific individual cases. In the thermal path, these tolerance-compensating interface fillers typically represent the greatest thermal resistances. Their thermal conductivity can be further reduced by air inclusions within the materials or between adjacent materials.

[0011] Insulation materials, if required at the interface, also represent a significant thermal resistance.

[0012] Gappads, which are essentially pre-crosslinked gap fillers on a carrier material, can also be used for thermal bonding. Since these materials are guaranteed to be free of voids, they are also suitable for insulation purposes. However, their ability to compensate for tolerances is severely limited, so their use is primarily practical in tolerance-free applications.

[0013] In conventional die-cast aluminum housings, the thermal conductivity is significantly reduced compared to pure aluminum due to the silicon content and porosity within the aluminum structure. Therefore, it is virtually impossible to connect a conventional die-cast aluminum housing with directly coupled power semiconductors to a cooling duct via a thermal interface, as the sum of the thermal resistances would become unacceptably high.

[0014] The arrangement according to the invention provides a very effective and cost-efficient way to dissipate the waste heat generated during the operation of a power electronic component under the described boundary conditions and thus avoid overheating of the power electronics.

[0015] According to the invention, this is achieved by thermal coupling using a heat spreading element which, on the one hand, lies flat against a surface of the housing and, on the other hand, is attached directly to the cooling channel.

[0016] An embodiment of the invention is illustrated and explained in more detail below with reference to the drawing. The drawings show...

[0017] Fig. 1: An arrangement according to the invention in a first embodiment. Fig. 2: A detailed view of the arrangement in Fig. 1.

[0018] Fig. 3: An arrangement according to the invention in a second embodiment. Fig. 4: A detailed view of the arrangement in Fig. 3.

[0019] Figures 1 and 2 show an electrical circuit with several electrical components. A power component is enclosed in an insulating housing 1, which contains an entire electronic circuit that generates heat during operation. The main surface of the power component's housing 1, visible in the drawing, rests against a printed circuit board (PCB), which is not shown. The housing's terminals 1' are electrically connected to corresponding contacts on the PCB. To effectively dissipate the generated heat, the housing 1 must be thermally coupled to a cooling channel 2 through which a coolant flows.

[0020] The thermal coupling of the housing 1 to the cooling channel 2 is achieved by means of a heat spreading element 3. This heat spreading element 3 is essentially a plate-shaped structure made of a metallic or ceramic material. The main surface of the heat spreading element 3, located at the bottom of the drawing and not visible, rests fully against a similarly flat surface of the cooling channel 2. The upper main surface of the heat spreading element 3 has trapezoidal structures in cross-section, each corresponding to a power component. These trapezoidal structures serve to optimally distribute the heat, distributing the heat flow over the largest possible area on the underside of the heat spreading element 3.

[0021] With its main surface located at the bottom in the drawing, the housing 1 of the respective power component rests against the upper, flat surface of the trapezoidal structure of the heat spreading element 3 assigned to it.

[0022] The housings 1 of the power components are screwed to the heat spreader 3, using only minimal force to avoid damaging the housings 1. To ensure optimal heat transfer, a material such as thermal paste or gap filler can be applied between the housing 1 and the heat spreader 3. The printed circuit board (PCB) is then placed onto the housings 1 of the power components connected to the heat spreader 3, and the terminals T of the housing 1 are soldered to the PCB using a suitable soldering method. The heat spreader 3 has six mounting bosses 3' on its edge, to which the PCB is screwed.

[0023] In this way, an initially stress-free assembly is created. Manufacturing tolerances are accommodated by the position of the through-inserted connecting pins 1' in the circuit board, and only a very small distance needs to be bridged between the underside of the housing 1 and the heat spreading element 3.

[0024] The first embodiment of the arrangement according to the invention shown in Figures 1 and 2 and the second embodiment shown in Figures 3 and 4 are largely identical. They differ only in the manufacturing method of the heat spreading elements 3 and the associated, slightly different design of the trapezoidal structures.

[0025] In the first embodiment shown in Figures 1 and 2, the heat spreading element 3 is realized as a cold-forged or sintered component. These two manufacturing methods allow for shaping in all three spatial dimensions. In particular, manufacturing as a cold-forged component offers excellent thermal conductivity compared to cast materials due to the alloy and the absence of voids. However, in this embodiment, the surface area of ​​the heat spreading elements 3 is limited, so that only a certain number of power components can be accommodated on a single heat spreading element 3. Therefore, several cold-forged or sintered heat spreading elements 3 must generally be used.

[0026] In the second embodiment shown in Figures 3 and 4, the heat spreading element 3 is formed as a section of an extruded aluminum profile 7. Extruded aluminum profiles exhibit good thermal conductivity and allow for very thick sections alongside relatively thin ones, enabling the design of screw connections in a nearly optimal manner. Furthermore, other heat-generating components, such as transformers, can also be easily connected to the cooling system within the same extruded profile 7. Figures 1 and 3 each show a transformer 4. In the embodiment shown in Figure 3, the transformer 4 is arranged on the same extruded profile 7 that also forms the heat spreading elements 3. The extruded profile 7 is closed off by closing plates 5 to form a trough, allowing for further improved thermal integration through the use of potting compound.Figure 4 shows the extruded profile 7 without the transformer 4 and the closing plates 5. The design using aluminum extruded profiles generally allows for more cost-effective manufacturing than the variant with flow-formed components.

[0027] Both variants have in common that the heat spreading elements 3 should be permanently pressed against the cooling channel 2 with the highest possible constant pressure for optimal thermal coupling.

[0028] According to the invention, this problem is solved by a spring clamping plate 6 shown in Figures 1 and 3, which is screwed firmly to the cooling channel 2. The spring clamping plate 6 presses the heat spreading elements 3, under which a gap pad or a corresponding material such as thermal paste or gap filler is located for thermal coupling, permanently and constantly against the external cooling channel 2 across all states of thermal expansion.

[0029] The remaining housing assembly can be attached to this spring clamp plate 6 and preferably consists of sheet metal or plastic parts. Reference numeral

[0030] 1 case

[0031] 1' Connection pin 2 Cooling channel

[0032] 3 Heat spreading element

[0033] 3' screw-on domes

[0034] 4 Transformer

[0035] 5 Strike plate 6 Spring clamp plate

[0036] 7 Extruded profile

Claims

Patent claims 1. Arrangement for dissipating electrical waste heat from an electrical power component, comprising an electrical power component which is provided with an insulating housing (1 ) and is thermally coupled to a cooling channel (2) via this housing, characterized in that the thermal coupling is effected by means of a heat spreading element (3) which on the one hand is in contact with a main surface of the housing (1 ) and on the other hand is attached directly to the cooling channel (2).

2. Arrangement according to claim 1, characterized in that the heat spreading element (3) is a substantially plate-shaped structure made of a metallic and / or ceramic material.

3. Arrangement according to claim 1 or 2, characterized in that the upper main surface of the heat spreading element (3) has trapezoidal structures in cross-section, each of which is assigned to a housing (1 ) of a power component.

4. Arrangement according to one of claims 1 to 3, characterized in that the heat spreading element (3) is attached to the cooling channel (2) by means of at least one spring plate (6).

5. Arrangement according to one of claims 1 to 3, characterized in that the heat spreading element (3) is attached to the cooling channel (2) by means of a material-bonded connection.

6. Arrangement according to one of claims 1 to 5, characterized in that the heat spreading element (3) is designed as a cold-extruded component.

7. Arrangement according to any one of claims 1 to 5, characterized in that the heat spreading element (3) is designed as a sintered component.

8. Arrangement according to any one of claims 1 to 5, characterized in that the heat spreading element (3) is designed as a section of an aluminum extrusion profile (7).

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