Cooling device and method for manufacturing the same

Abstract

The present invention relates to a cooling device and a method for manufacturing the same. The cooling device (1) for cooling electronic components (8) mounted on a circuit board (6) comprises a hollow body (3, 4) defining a coolant delivery circuit for circulating a coolant fluid therethrough. The hollow body (3, 4) comprises a plurality of flat areas (4) linked by a duct area (3), wherein the flat areas (4) and the duct area (3) are formed as a continuous area of ​​the body (3, 4). When the body (3, 4) is fixed to the circuit board (6), each flat area (4) is configured to align with one or more electronic components (8) to transfer heat away.

Description

Technical Field

[0001] The present disclosure relates to a cooling device for cooling a plurality of electronic components mounted on a circuit board and a method of manufacturing the same. The present disclosure relates particularly to a cold plate for cooling an electronic control unit for automotive applications, and most particularly to a multi-domain controller (MDC). Background Art

[0002] Some electronic components heat up during use, which may subsequently impair their function or cause damage to the components. Therefore, cooling devices are usually fitted to electronic circuit systems to maintain their operating temperature within acceptable tolerances. For particularly high-demand applications, liquid cooling systems are often used due to their high cooling efficiency. Conventional liquid cooling systems usually have a cold plate, which is a device that usually has a flat metal body with an internal circuit of cooling channels or cooling tubes through which a coolant fluid can circulate. In use, the cold plate is fitted against the electronic components, and as the components heat up, the heat is transferred to the coolant through the body and the cooling tubes, and the heat is transported away from the coolant circuit.

[0003] Although some electronic components on a printed circuit board (PCB) can get very hot during use, other components do not. For example, a system on a chip (SoC) can be considered an active component because it typically generates a lot of waste heat when operating and requires active cooling. In contrast, components such as diodes or capacitors can be considered passive components because they will typically remain relatively cool. At the same time, active components are typically geometrically lower (i.e., flatter) than the surrounding cooler passive components. Therefore, when a flat cold plate is assembled on a PCB, the plate typically abuts the top of the taller passive component, but a gap is left between the plate and the top of the lower active component. Since these air gaps would otherwise provide a barrier to heat transfer from the component that the cold plate is intended to cool, so-called "pedestals" need to be assembled in these gaps. These pedestals are typically formed of the same metal as the body of the cold plate, and columns of thermally conductive material are provided to establish a thermal path from the active component to the cold plate.

[0004] The problem with the above conventional arrangement is that, regardless of the thermal conductivity of the susceptor material, the length of the thermal path means that the susceptor still presents a significant thermal resistance. The susceptor thus provides a suboptimal thermal connection between the active components and the coolant.

[0005] The above problems are further exacerbated by the challenge of ensuring good thermal contact between the base and the active components. In particular, air gaps between the opposing faces of the components and the base can significantly reduce thermal conduction. These gaps can be anything from very small holes formed due to surface roughness to larger gaps caused by production variations that compromise the dimensional stability of the assembly. For example, a PCB may not be completely flat, resulting in some components being mounted farther away from the cold plate than others. To mitigate this, a layer of thermal interface material (TIM) is typically applied to fill these gaps, thereby improving the fit of the joints between the components. However, due to the large gaps that may occur, a relatively thick layer of TIM is typically applied to ensure that there is enough material to completely fill the gaps. Unfortunately, this compromises overall thermal conductivity because, although TIM is a better thermal conductor than air, it is not as effective as providing a very tight connection between the hot active components and the cooling structure.

[0006] US20050128705 discloses a cooling assembly that attempts to solve some of the above problems. In particular, US20050128705 teaches a modular device in which, instead of providing the cold plate as a single body, a plurality of smaller cold plate units are provided, each of which can be independently attached to a separate electronic module. The cold plate units are then connected to each other by flexible pipes to establish a cooling fluid circuit. Although this device allows a tighter fit between each electronic module and its corresponding cold plate unit, it causes new problems. For example, manufacturing and assembly costs are greatly increased because each cold plate unit must be manufactured separately and fixed to its corresponding electronic module. In addition, the large number of fluid connections between the cold plate units and the pipes also increases the risk of leakage. This makes this device particularly unsuitable for automotive applications, in which harsh vibration conditions require very high leak resistance.

[0007] Therefore, there remains a need for an improved cooling device for cooling components mounted to a circuit board. Summary of the invention

[0008] The present disclosure relates to a cooling device and a method for manufacturing the cooling device, the cooling device being used to cool a plurality of electronic components mounted on a circuit board. The cooling device can be used with an electronic control unit or a multi-domain controller mounted to a printed circuit board.

[0009] According to a first aspect, there is provided a cooling device for cooling electronic components mounted on a circuit board, the device comprising: a hollow body defining a coolant delivery circuit for circulating a coolant fluid therethrough, the hollow body comprising a plurality of flat regions linked by duct regions, wherein the flat regions and duct regions form a continuous region of the body, and wherein each flat region is configured to align with one or more electronic components when the body is secured adjacent to the circuit board for transferring heat away from the corresponding one or more electronic components.

[0010] In this way, the flat region of the body provides a large heat absorbing surface which can be positioned directly adjacent to the active electronic components dissipating the heat. This brings the coolant into close proximity with those electronic components which become hot during operation, thereby providing an increased heat flux into the coolant and, therefore, improved cooling performance. At the same time, since the flat region of the body and the duct region are formed continuously with one another, there are no joints or seals between the sections, unlike modular arrangements. This not only avoids the production and assembly costs associated with having separate components, but also arranging the hollow body as a single cooling tube avoids the risk of leaky connections between different functional components.

[0011] In an embodiment, the cooling device further comprises one or more couplings for securing the body to the circuit board. In this way, the cooling device can be secured directly to the circuit board to provide a compact assembly. In an embodiment, the coupling comprises a fixture aperture for receiving a fixture for attaching the flat region to the circuit board.

[0012] In an embodiment, the coupling includes a biasing element for biasing the flat region toward the electronic component. In this way, the volume of thermal interface material required to maintain effective thermal contact is minimized. In addition, the fit between the flat region and the active component can be maintained throughout different operating conditions, thereby providing improved cooling consistency.

[0013] In an embodiment, the coupling comprises a fixture, and the biasing element is a spring coupled to the fixture for applying a biasing force to the flat region so as to bias the flat region toward the corresponding one or more electronic components to be cooled. In this way, the spring allows a consistent compressive pressure to be applied and maintained at a plurality of couplings.

[0014] In an embodiment, at least one coupling is associated with each flat region for securing the flat region to a corresponding one or more electronic components to be cooled. In this way, the coupling can provide a localized securing force to hold the flat region against its corresponding electronic component. For example, localized compressive pressure can cluster around a particular component to ensure that mating contact achieved by the flat region is maintained.

[0015] In an embodiment, each coupling comprises an aperture for receiving a fixing means. In this way, the fixing means can be received through a hole simply machined into a lug provided on the exterior of the body.

[0016] In an embodiment, one or more of the flat regions have substantially the same cross-sectional area as one or more of the tube regions. In this way, a consistent fluid flow velocity may be maintained, thereby mitigating the risk of forming stagnant areas of coolant that would otherwise reduce heat transfer efficiency.

[0017] In an embodiment, one or more of the flat regions have a smaller cross-sectional area than one or more of the duct regions. In this way, regions of locally higher flow velocity or turbulence may be formed within the hollow body for increasing heat exchange in these regions.

[0018] In an embodiment, the body is formed by hydroforming. Preferably, the body is formed by tube hydroforming. In this way, the body can be formed as a thin-walled hollow structure, which not only reduces weight and material costs, but also allows for enhanced cooling efficiency by reducing the distance of the thermal path between the active components and the coolant. In an alternative embodiment, the body can be formed by 3D printing.

[0019] In an embodiment, the body is formed of metal. This provides a highly thermally conductive material for enhanced cooling efficiency, as well as sufficient rigidity to allow easy connection to a circuit board.

[0020] In an embodiment, the flat region and the duct region are integrally formed.

[0021] In an embodiment, the flat region comprises a planar cooling surface for fitting against a respective one or more electronic components to be cooled.

[0022] In an embodiment, the body includes an internal structure for interrupting coolant fluid circulating through the coolant delivery circuit. In this way, a heat exchange structure can be disposed within the coolant delivery circuit for enhanced heat transfer.

[0023] In an embodiment, the circuit board further comprises passive components, and the body is configured to expose the passive components when fixed adjacent to the circuit board. In this way, the flat area of ​​the cooling device can be placed below the height of the passive components, thereby allowing their cooling surfaces to be positioned closer to the hotter active components. Furthermore, the cooling effect can thereby also be concentrated on the active components.

[0024] According to a second aspect, there is provided a method of forming a cooling device for cooling electronic components mounted on a circuit board, the method comprising: providing a blank; pressing the blank in a mold to form a hollow body having a plurality of flat areas linked by duct areas, wherein the flat areas and duct areas are formed as continuous areas of the body, and wherein the hollow body defines a coolant delivery circuit for circulating a coolant fluid therethrough, and each flat area is configured to align with one or more electronic components when the body is secured adjacent to the circuit board for transferring heat away from the corresponding one or more electronic components.

[0025] In this way, a simple manufacturing method for forming an efficient and lightweight cooling device is provided.

[0026] In an embodiment, the blank is a tube having a wall defining an inner bore, and the step of pressing the blank includes securing the tube within a mold and applying a pressurized liquid to the inner bore for conforming the wall to the shape of the mold. In this way, hydroforming can be used to form the body as a thin-walled hollow structure. This can thereby provide a cooling device having reduced weight and material costs and providing enhanced cooling efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Illustrative embodiments will now be described with reference to the accompanying drawings, in which:

[0028] Figure 1 shows a top view of a cooling device according to a first embodiment;

[0029] Figure 2 Shows Figure 1 An isometric view of the cooling device shown;

[0030] Figure 3 shows an isometric view of a cooling device according to a second embodiment;

[0031] Figure 4 Shows Figure 3 A top view of the cooling device shown;

[0032] Figure 5 Shows Figure 3 An alternative top view of the cooling device shown, wherein the flat area is transparent; and

[0033] Figure 6 shows the coolant path along and through Figure 3 Cross-section through the flat region of the cooling device shown. DETAILED DESCRIPTION

[0034] Figure 1 and Figure 2 A first embodiment of a cooling device 1 is shown, which is arranged as a continuous tubular body 3, 4 having a plurality of flat regions 4 linked by duct regions 3. The hollow interior of the body 3, 4 forms a fluid circuit between the inlet 2 to the outlet 7. In use, a coolant fluid is pumped through the fluid circuit to transfer heat away from adjacent electronic components.

[0035] The duct region 3 has a substantially circular cross section and is configured to spiral over the circuit board 6, avoiding taller passive components (not shown) protruding from its surface.

[0036] At the junction between the duct area 3 and the flat area 4, the circular cross section transitions to a wider flat section with a substantially flat bottom surface. The flat bottom surface of each flat area 4 provides a mating surface for mating with the top surface of the active component 8 that generates heat during its operation. At the same time, as Figure 2 As shown, the flat area 4 within the body 3, 4 is positioned such that when the cooling device is mounted to the circuit board 6, the flat area covers the active electronic components 8 on the circuit board.

[0037] The cooling device 1 also includes a plurality of couplings 5 ​​for securing the device 1 to a circuit board 6. The couplings 5 ​​include fixture lugs extending from the exterior of the body 3,4 and include apertures for receiving biasing fixtures for connecting the body 3,4 to the circuit board 6.

[0038] In this embodiment, the bodies 3, 4 are formed as a single component using a hydroformed tube. A pre-cursor is bent into an approximate shape and pressed within a mold. A high pressure liquid, such as water, is then applied through the bore of the tube to force the walls to conform to the mold. This provides a single integral component that mitigates the risk of coolant leaks and simplifies the connection of the device 1 to the circuit board 6. At the same time, a strong thin-walled structure is provided that is not only resilient to operating conditions, but also allows for efficient heat transfer from the active components 8 to the coolant circulating through the bodies 3, 4.

[0039] Figures 3 to 6 A cooling device according to a second embodiment is shown. Although these figures provide a more detailed illustration of the device 1 and circuit board 6, the device 1 functions in substantially the same manner as the first embodiment and therefore a description of common parts is omitted.

[0040] As shown, the device 1 has been mounted to a circuit board 6 for cooling electronic components during operation of the electronic components. The circuit board 6 is a printed circuit board including a plurality of components, some of which can be classified as active components 8 because they generate heat during operation and require cooling, and some of which can be classified as passive components 9 because they do not require cooling during operation or only require passive cooling.

[0041] The body 3, 4 of the device comprises two flat areas 4, wherein the duct area 3 is connected between the two flat areas 4 and forms the inlet 2 and the outlet 7. The flat area 4 has a very thin, flat construction with a wide rectangular cross section. The cross-sectional area of ​​each flat section is substantially the same as the hole area of ​​the circular duct area 3. In this way, the flow rate of the coolant throughout the cooling device is substantially constant. This can thereby reduce the risk of coolant dead zones, in which low flow rates can reduce the cooling efficiency.

[0042] Figure 5 An assembly is shown where the flat area 4 is transparent to show the covered active components 8. This leaves the passive components 9 exposed. Thus, the cooling effect is concentrated on the components that heat up during operation of the circuit.

[0043] Figure 6 A cross-section through one of the flat regions 4 is shown, the section being taken along the coolant path. As shown, the duct region 3 tapers downward into the thin flat region 4, with the bottom outer surface mating with the top surface of the underlying active component 8. The flat region 4 is also positioned below the height of the passive component 9, so that the coolant becomes closer to the heat dissipated by the active component 8.

[0044] Figure 6The fixing means of the coupling 5 are also shown in more detail. In this embodiment, the fixing means are arranged as screws 10, which extend through lugs provided on the bodies 3, 4 and are received in threaded apertures provided on the circuit board 6. Each fixing means has a biasing element in the form of a compression spring 11 arranged coaxially with the screw 10. The spring 11 is supported between the head of the screw at the top and the lug extending from the bodies 3, 4, so as to apply a compressive force for biasing the bodies 3, 4 into contact with the active components 8 covered by the bodies. At the same time, the coupling 5 is gathered around the active components 8. In this way, a consistent compressive force can be applied to maintain good thermal contact between the mating surface of the flat area 4 and the active components 8 below under all different operating conditions. In this way, the working load and thermal expansion coefficient changes of different components can be accommodated. In addition, in automotive applications, contact can be maintained even if vibrations occur during driving. This can thereby compensate for any dimensional changes in the assembly, which otherwise may result in a larger air gap between the contact surfaces. As a result, the need for thermal interface material (TIM) is limited to compensating any residual gaps that may arise due to the surface roughness of the active components 8 and the flat areas 4. Therefore, only a very thin layer of TIM is required.

[0045] In use, a coolant, such as a water / glycol mixture, is pumped through the inlet 2, enters and fills the first flat section 4, flows through the duct section 3 and fills the second flat section 4, and then exits through the outlet pipe 7. In this way, the coolant fills the interior of the flat area 4, extracting heat from the top surface of the active component 8. In automotive applications, the inlet pipe 2 and the outlet pipe 7 may be supplied by the vehicle's cooling system.

[0046] With the above arrangement, the flat region 4 can provide good thermal contact with the active components 8 while allowing the coolant to be positioned closer to those active components 8 than they are in conventional cold plate systems. At the same time, the arrangement requires less material than conventional cold plate systems, thereby saving weight and cost, and provides very high cooling efficiency.

[0047] It should be understood that the above embodiments are only for illustrative purposes. In fact, the embodiments can be applied to many different configurations, and the detailed embodiments are simple for those skilled in the art.

[0048] For example, although the flat region 4 has been shown as having a flat bottom surface for mating to an active component, it will be appreciated that component structures may also be provided on this surface. That is, protrusions and / or depressions may be formed corresponding to the top of the associated active component, thereby improving the mating of the cooling surface to the component.

[0049] Furthermore, although the bodies 3, 4 have been described as having a hollow tubular configuration, albeit with flat regions, the structure may be configured to control flow rate and turbulence within the coolant delivery circuit. For example, to enhance heat exchange, one or more of the flat regions may have a reduced cross-sectional area to increase fluid flow through that region. Furthermore, the internal structure may be configured to generate localized turbulence in the coolant flow for enhanced cooling efficiency.

[0050] Finally, although the above examples describe the structure of the body as a single integral component, it will be understood that the body can be formed by multiple components that are assembled together during manufacturing to form a single unit. For example, the body can be cast as an upper section and a lower section, which are then welded together. However, the flat area and the duct area of ​​the body are formed continuously with each other. That is, even in the case where the body can be formed by component parts, these component parts will also include the flat area and the duct area. In this way, the risk of leakage between different functional components of the body is mitigated.

Claims

1. A cooling device, the cooling device being used to cool electronic components mounted on a circuit board, the cooling device comprising: a hollow body defining a coolant delivery circuit for circulating a coolant fluid therethrough, the hollow body comprising a plurality of flat regions linked by duct regions, wherein the flat regions and duct regions are formed as a continuous region of the body, wherein each flat region is configured to align with one or more electronic components when the body is secured adjacent to the circuit board for transferring heat away from the corresponding one or more electronic components, Therein, one or more of the flat regions have a cross-sectional area that is smaller than or substantially the same as a cross-sectional area of ​​one or more of the pipe regions. 2 . The cooling device of claim 1 , further comprising one or more coupling members for securing the body to the circuit board. 3 .

3. The cooling device according to claim 2, wherein: The coupling includes a biasing element for biasing the flat region toward the electronic component.

4. The cooling device according to claim 3, wherein: The coupling comprises a fixture, and the biasing element is a spring coupled to the fixture for applying a biasing force to the flat region so as to bias the flat region towards the respective one or more electronic components to be cooled.

5. The cooling device according to any one of claims 2 to 4, wherein: At least one coupling is associated with each flat region for securing said flat region to the respective electronic component or components to be cooled.

6. The cooling device according to any one of claims 1 to 4, wherein: The body is formed by hydroforming.

7. The cooling device according to any one of claims 1 to 4, wherein: The body is formed of metal.

8. The cooling device according to any one of claims 1 to 4, wherein: The flat region and the duct region are formed integrally.

9. The cooling device according to any one of claims 1 to 4, wherein: The flat region comprises a planar cooling surface for fitting against a corresponding one or more electronic components to be cooled.

10. The cooling device according to any one of claims 1 to 4, wherein: The body includes internal structure for interrupting coolant fluid circulating through the coolant delivery circuit.

11. The cooling device according to any one of claims 1 to 4, wherein: The circuit board also includes passive components, and the body is configured to expose the passive components when the body is secured adjacent to the circuit board.

12. A method of forming a cooling device for cooling electronic components mounted on a circuit board, the method comprising: Providing blanks; pressing the blank in a die to form a hollow body having a plurality of flat regions linked by duct regions, wherein the flat regions and duct regions are formed as a continuous region of the body, and wherein the hollow body defines a coolant transfer circuit for circulating a coolant fluid therethrough, and each flat region is configured to align with one or more electronic components when the body is secured adjacent the circuit board for transferring heat away from the corresponding one or more electronic components, One or more of the flat regions have a cross-sectional area that is substantially the same as or smaller than a cross-sectional area of ​​one or more of the pipe regions.

13. The method of forming a cooling device according to claim 12, wherein: The blank is a tube having a wall defining an inner bore, and The step of pressing the blank includes securing the tube within the die and applying a pressurized liquid to the inner bore for causing the wall to conform to the shape of the die.

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