Semiconductor assembly and heat sink obtained by casting associated

Abstract

An electronic device comprising, on the one hand, an assembly of semiconductor components (2) and, on the other hand, a heat sink (6) having cooling fins (14) with at least one ejector (16). The ejectors (16) have an elongated shape along a longitudinal axis. At least two semiconductor components (2) are arranged on each longitudinal axis of an ejector (16). (See abstract figure: Figure 2)

Description

Title of the invention: Semiconductor assembly and associated foundry heat sink

[0001] The present disclosure relates to an electronic device and its heat sink obtained by casting, for example by die casting. Technical field

[0002] The technical field of the present disclosure is the production of devices implementing semiconductors for the management of power electronics equipment. For the proper functioning of the semiconductors and / or other components used in these devices, it is appropriate to provide a cooling system to dissipate the heat released, in particular at the level of the semiconductors. These semiconductors are, for example, diodes or transistors, for example of the IGBT or MOSFET type.

[0003] The present disclosure relates more particularly but not exclusively to on-board applications, for the automotive industry for example. In this field, a permanent problem is to produce compact devices, if possible lightweight, without however sacrificing performance, quite the contrary. Prior art

[0004] To dissipate the heat released by an electronic device, it is known to use a heat sink comprising a base in thermal contact with the electronic device and from which a large number of fins extend. For relatively simple shapes of heat sink, the latter can be produced by extrusion. It then has a profiled shape. For more complex shapes, adapted to the shape of the electronic device, it is known to use foundry processes, most often by die-casting, to produce heat sinks. With this production method, the heat sink obtained comprises substantially cylindrical ejectors arranged at the level of fins, each ejector projecting on either side of a fin into the free space between the fins intended for the circulation of the cooling air.These ejectors thus create pressure losses for the cooling air flow circulating between the fins of the heat sink and generally reduce the performance of the heat sink (compared to a heat sink of similar shape, without ejectors).

[0005] Cooling of components in an electronic assembly is usually done by a heat sink arranged like a sole below a support on which the components are mounted. This support is most often a printed electronic circuit board, called in English Printed Circuit Board PCB. The The heat released then passes through the support and thermal bridges, for example vias, are then advantageously provided in the support. Such cooling is called bottom cooling (or "bottom cooled" in English). It is also known to cool components in an electronic assembly from the upper side of the device, i.e. the side opposite the support on which the components are mounted. In this configuration, the components are between their support and a heat sink. This configuration makes it possible to avoid transferring the heat to be dissipated through the support.

[0006] The present disclosure aims to provide an electronic device with semiconductor type components to be cooled associated with a heat sink obtained by casting having improved cooling characteristics. Summary

[0007] The original idea underlying the present disclosure is to align the components to be cooled with the ejectors coming from the casting in the heat sink. It has been found that this original configuration makes it possible to improve the efficiency of heat transfer to the sink.

[0008] The present disclosure thus relates to an electronic device comprising, on the one hand, an assembly of semiconductor type components and, on the other hand, a heat sink having cooling fins with at least one ejector.

[0009] According to the present disclosure, the ejectors have an elongated shape along a longitudinal axis, and at least two semiconductor-type components are arranged each time on a longitudinal axis of an ejector.

[0010] In a device as presented above, the characteristics set out in the following paragraphs may, optionally, be implemented, independently of one another or in combination with one another:

[0011] In such an electronic device, it is preferred that the majority of the semiconductor type components are arranged on a longitudinal axis of an ejector; more preferably, the majority of the semiconductor type components are substantially centered on a longitudinal axis of an ejector.

[0012] According to a first embodiment, the fins are substantially flat and parallel, and two ejectors corresponding to two neighboring fins are offset, that is to say are not opposite each other relative to the plane of the fins considered; an advantageous variant here provides that near an ejector, a fin adjacent to the fin associated with said ejector has a corrugation with a concave zone arranged opposite said ejector.

[0013] According to a second embodiment, it is provided that near an ejector, a fin adjacent to the fin associated with said ejector has an opening opposite screw of said ejector over its entire height. According to a variant, the opening of the neighboring fin can be made at the end of the fin, that is to say that the fin can be shortened.

[0014] In an electronic device as described above, the semiconductor components may be mounted on a support, and said components may be located between said support and the heat sink. Other variants are however conceivable. The device may have bottom cooling, in which the heat flow must pass through the support to reach the heat sink and / or the components to be cooled may be integrated into a module which is then itself mounted on a support.

[0015] According to another aspect, there is provided a method of producing an electronic device comprising the following steps: - provision, on the one hand, of an assembly of semiconductor type components and, on the other hand, of a heat sink having cooling fins with at least one ejector having an elongated shape along a longitudinal axis, characterized in that the semiconductor components are assembled in such a way that at least two semiconductor components are arranged each time on a longitudinal axis of an ejector and / or the heat sink is shaped in such a way that at least two longitudinal axes of ejectors pass through a semiconductor component.

[0016] According to another aspect, there is provided a motor vehicle comprising an electric motor, characterized in that it comprises an electronic device as described above. Brief description of the drawing

[0017] Other characteristics, details and advantages will appear on reading the detailed description below, and on analyzing the attached drawing, in which: Fig.l

[0018] [Fig.l] is an illustrative diagram of a first assembly of a semiconductor type component with a heat sink; Fig. 2

[0019] [Fig.2] illustrates a second assembly of a semiconductor type component with a heat sink according to the present disclosure; Fig. 3

[0020] [Fig.3] is a schematic top view of a heat sink which can be implemented in this disclosure; Fig. 4

[0021] [Fig.4] is a schematic perspective view of a heat sink of the type illustrated in [Fig.3]; Fig. 5

[0022] [Fig.5] is a schematic top view of an alternative embodiment of the heat sinks of Figures 3 and 4. Fig. 6

[0023] [Fig.6] is an example in top view of a heat sink and semiconductor components in a preferred configuration according to the present disclosure. Description of the embodiments

[0024] The present description relates to an electronic device called a power device and more particularly such a device intended to be mounted on board a vehicle, automobile or other such as for example a car, a motorcycle, an agricultural tool, etc., said vehicle being equipped with an electric motor to move it: here it may be a so-called "electric" vehicle, that is to say comprising only one or more electric motor(s) to drive it or a hybrid vehicle and then comprising at least one electric motor and an internal combustion engine to drive it. Such an electronic device may be for example (non-exhaustive) a battery management device, a DC-DC converter, an on-board charger, an inverter, etc.

[0025] To produce such an electrical device, electronic components 2 of the semiconductor type (diode, transistor, IGBT, MOSFET, etc.) are mounted on a support subsequently called PCB and referenced 4 in the figures. A heat sink 6 is provided for cooling the component 2 when it is operating. Figures 1 and 2 are schematic diagrams and, to simplify these figures, only illustrate a single component 2. It should be noted that these figures are not at all to scale and the relative sizes of the elements shown are not respected.

[0026] In the embodiment of [Fig. 1], component 2 is cooled “from below”. Indeed, it is assumed that component 2 is on PCB 4. Note that heat sink 6 is on the opposite side to component 2 with respect to PCB 4 and is therefore located under PCB 4 and thus below component 2. The assembly of [Fig. 1] corresponds to an assembly with bottom cooling (“bottom cooled” in English).

[0027] In the embodiment of [Fig. 2], considering the same orientation given by the relative position of component 2 with respect to PCB 4, that is to say that component 2 is above PCB 4, it is noted that heat sink 6 is located above component 2 (despite the orientation of the figure). The assembly of [Fig. 2] corresponds to an assembly with top cooling.

[0028] In these two types of assembly, the heat sink 6 is not directly in contact with the part to be cooled (the PCB 4 in [Fig. 1] and the component 2 in [Fig. 2]). In both embodiments illustrated, a thermal interface material 8 is arranged between the part to be cooled and the heat sink 6. The purpose of this material is to facilitate the transfer of heat to the heat sink, in particular by avoiding the presence of air between the part to be cooled and the heat sink 6. This thermal interface material 8 also has a mechanical function and participates in the connection between the component 2 or the PCB 4 with the heat sink 6. It may be a glue, a paste or a thermal connection pad (or other embodiment).

[0029] Furthermore, since the heat sink 6 is most often made of a metal, in particular aluminum or an aluminum-based alloy, it is often necessary to provide electrical insulation between the part to be cooled and the heat sink 6. In the assemblies of FIGS. 1 and 2, an electrical insulation layer 10 has thus been provided which is made of a material which is both electrically insulating and thermally conductive. The electrical insulation layer 10 can be applied to the heat sink 6 by projection, or spraying, or by chemical etching (or by other methods), or by an insert of a ceramic layer.

[0030] Figures 3 to 6 illustrate a heat sink 6 that can be used in the assemblies illustrated in Figures 1 and 2. [Fig. 4] relates to an embodiment of such a heat sink 6 and is a perspective view which shows the general structure of a heat sink. [Fig. 4] shows a base 12 from which fins 14 and ejectors 16 extend.

[0031] The base 12 has a shape adapted to the electronic device with which the heat sink 6 is associated. Most often, to achieve regular diffusion of heat, the base has a substantially constant thickness. In the embodiment of [Fig.4], the base 12 is parallelepipedal in shape: it has a rectangular base shape and a constant thickness.

[0032] The fins 14 extend from the base 12 and form a single piece with it. They are substantially flat and extend perpendicular to the base 12. Conventionally, the fins 14 are parallel and define between them a circulation corridor for a fluid, most often air but possibly a liquid such as water.

[0033] The ejectors 16 are in a cylindrical or truncated cone shape and are each associated with a fin 14. The ejectors 16 are an outgrowth from a fin 14. They are derived from the process for obtaining the dissipator 6 when the latter is obtained by a foundry process, including die casting or die casting. It is then appropriate to provide in the mold receiving the molten metal a chimney for the evacuation of the gases present in the mold. These chimneys are cylindrical or conical management to facilitate their demolding. As can be seen from Figures 3 to 6, the ejectors 16 form an obstacle to the flow of a fluid between the fins 14 and usually limit the cooling capacities of the heat sink.

[0034] As illustrated in Figures 2 and 6, it is proposed in the present disclosure to make at least some ejectors 16 coincide with at least some components 2 which emit heat. As indicated, the ejectors 16 have a cylindrical or frustoconical shape. More generally, they have an elongated shape along a longitudinal axis. Advantageously, it is provided that at least some components 2 are arranged on a longitudinal axis of an ejector 16. Advantageously, for better cooling, the majority (at least half) of the components 2 are aligned with an ejector 16 (and are therefore crossed by the longitudinal axis of said ejector). Preferably, all the components 2 of the semiconductor type (transistors, diodes, etc.) are aligned with an ejector 16.To improve cooling of the device, it is preferable that when a component 2 is aligned with an ejector, the longitudinal axis of the ejector 16 passes substantially in a central area of ​​the component.

[0035] [Fig. 6] is a schematic top view of a device according to the present disclosure on which are represented four components 2 of the semiconductor type, and releasing heat in operation, and partially a heat sink 6 with in particular its fins and four ejectors 16 corresponding to said components 2. As stated above, it is noted that the four ejectors 16 and the four components 2 are superimposed (the longitudinal axes of the ejectors are perpendicular to the plane of the figure). In [Fig. 6], contours 2' in dotted lines each illustrate an area heated by a component 2 at the base of the fins 14 and the ejectors 16. Given the thickness of the base 12, the heat emitted by the component 2 and transmitted by possibly the PCB 4 and the thermal interface material 8 diffuses through the base by diffusing in a cone.

[0036] In the present disclosure, it is a question of adapting the positioning of the components 2 and / or the shape of the heat sink 6 to improve the cooling of the device and limit the operating temperature of the device. For this improvement, an alignment, or preferably a centering, of the components 2 with the ejectors 16 is provided. It is also advantageously provided that the contours 2' do not intersect. This improvement is achieved during the design of the electronic device by adapting the shape of the heat sink 6 to the layout diagram of the components 2 or on the contrary by designing a heat sink 6 adapted to the layout of the components 2 or by co-developing the layout of the components and the shape of the heat sink to tend towards an optimization of the heat dissipation of the electronic device.

[0037] For the design of the heat sink 6, several advantageous characteristics regarding fins and / or ejectors can be implemented to improve the cooling of the electronic device.

[0038] In Figures 3 and 4, the ejectors 16 are arranged in a staggered pattern. In these figures, the fins 14 are substantially planar. Considering two neighboring fins 14, the two corresponding ejectors 16 are not arranged opposite each other. This means that if we consider a first fin 14, its ejector 16 and a perpendicular to the first fin, the latter does not pass through the ejector of the neighboring fin. This embodiment makes it possible to limit the impact of the intrusion of the ejectors into the fluid circulation corridors between the fins 16.

[0039] [Fig. 5] proposes an advantageous embodiment variant adapted to the present disclosure. This variant promotes the cooling of the ejectors 16. This is favorable in the case of the present disclosure since the components 2 are preferably arranged at the level of ejectors 16. Better cooling of the ejectors therefore contributes to better overall cooling of the device. The idea here is to remove a part of a fin opposite an ejector 16. Let then be a first fin 14 having an ejector 16. An opening is then made in at least one neighboring fin opposite the ejector 16. If, as illustrated in [Fig. 5], the ejectors 16 are arranged near a fin end, this then amounts to shortening the fins whose end is opposite an ejector 16.In the example illustrated, one fin 14 out of two is shortened at its end and the non-shortened fins have at their end an ejector 16 opposite which the neighboring fins do not extend. This embodiment reduces the exchange surface of the heat sink by reducing the exchange surface of the fins. However, the removed fin parts are not normally located at the level of a component to be cooled. This solution makes it possible to have an overall greater flow of air (or other fluid) in the heat sink and this is then favorable for the overall cooling of the electronic device to be considered.

[0040] [Fig.6] proposes another embodiment of a heat sink promoting the cooling of the device, in particular when components to be cooled (transistors, MOSFETs, IGBTs, etc.) are arranged opposite ejectors.

[0041] In this [Fig.6], ejectors 16 are arranged on flat fins 14 or at least on a flat portion of a fin 14. Opposite an ejector 16, a neighboring fin 14 then has a concave zone 18 (and does not carry an ejector). Thus, in the vicinity of an ejector 16, the neighboring fins have an undulation. The shape of the neighboring fins is advantageously made in such a way that the width of the fluid passageway (air, other gas or liquid) has substantially a constant width, or at least does not have any sudden variation in its width. The variations in the width of the fluid circulation corridor are therefore done "smoothly". Furthermore, the shapes of the corrugations are made in such a way that the minimum width of a fluid circulation corridor does not vary, or varies as little as possible, between two neighboring corridors. This embodiment significantly limits pressure losses and thus improves the overall cooling of the heat sink.

[0042] In [Fig. 6], the fins 14 having at least one undulation do not include an ejector. This is due to a simplification of [Fig. 6] which is a partial view: the fins shown without ejectors may include one or more ejectors outside the area illustrated for illustrative and non-limiting purposes. Industrial application

[0043] The present technical solution can be applied in particular in the cooling of electronic devices, and more particularly for on-board devices.

[0044] The proposed solution makes it possible to take advantage of the presence of ejectors resulting from the manufacturing process of a heat sink, usually considered as an obstacle, to improve the performance of a heat sink. By making the heating components coincide with the ejectors, the efficiency of heat transfer from the component to the heat sink is improved.

[0045] The proposed solution relates to electronic devices with a heat sink obtained by a foundry process. By way of non-limiting example, the sink may be a sink made of an aluminum-based alloy and die-cast.

[0046] The proposed device can be cooled by natural convection, or with blown air or even with a liquid. All the cooling methods usually used can be used with this new device.

[0047] By way of illustration and not limitation, the devices described above and illustrated in the drawing allow heat dissipation ranging for example from 30 to 50 W / cm2. To obtain such heat dissipation, it is preferable to use cooling from above as illustrated in [Fig.2]. Thus, the electronic device may be for example a power GAN device.

[0048] Measurements have shown that by arranging a transistor in alignment with an ejector, the rise in the junction temperature of the transistor can be reduced by 7% for large semiconductors, i.e. semiconductors whose characteristic length is greater than half an inter-fin gap. For smaller semiconductors, a reduction of at least 3% can be achieved.

[0049] The present disclosure is not limited to the proposed embodiments and the variants mentioned above, only by way of example, but it encompasses all the variants that a person skilled in the art may consider within the framework of the protection sought.

Claims

Claims

1. Electronic device comprising, on the one hand, an assembly of semiconductor-type components (2) and, on the other hand, a heat sink (6) having cooling fins (14) with at least one ejector (16), characterized in that the ejectors (16) have an elongated shape along a longitudinal axis, and in that at least two semiconductor-type components (2) are arranged each time on a longitudinal axis of an ejector (16).

2. Electronic device according to claim 1, characterized in that the majority of the semiconductor type components (2) are arranged on a longitudinal axis of an ejector (16).

3. Electronic device according to claim 2, characterized in that the majority of the semiconductor type components (2) are substantially centered on a longitudinal axis of an ejector (18).

4. Electronic device according to one of claims 1 to 3, characterized in that the fins (14) are substantially flat and parallel, and in that two ejectors (16) corresponding to two neighboring fins (14) are offset, that is to say are not opposite each other relative to the plane of the fins (14) considered.

5. Electronic device according to claim 4, characterized in that near an ejector (16), a fin (14) adjacent to the fin associated with said ejector (16) has a corrugation with a concave zone (18) arranged opposite said ejector (16).

6. Electronic device according to one of claims 1 to 3, characterized in that near an ejector (16), a fin (14) adjacent to the fin associated with said ejector (16) has an opening opposite said ejector (16) over the entire height thereof.

7. Electronic device according to claim 6, characterized in that the opening of the neighboring fin (14) is made at the end of the fin, that is to say that the fin (14) is shortened.

8. Electronic device according to one of claims 1 to 7, characterized in that the semiconductor type components (2) are mounted on a support (4), and in that said components are located between said support (4) and the heat sink (6).

9. Method for producing an electronic device comprising the following steps: - provision, on the one hand, of an assembly of semiconductor-type components (2) and, on the other hand, of a heat sink (6) having cooling fins (14) with at least one ejector (16) having an elongated shape along a longitudinal axis, characterized in that the semiconductor components (2) are assembled in such a way that at least two semiconductor components (2) are arranged each time on a longitudinal axis of an ejector (16) and / or the heat sink (6) is shaped in such a way that at least two longitudinal axes of ejectors pass through a semiconductor component (2).

10. Motor vehicle comprising an electric motor, characterized in that it comprises an electronic device according to one of claims 1 to 8.

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