Dual power connection power electronics module for reduced contact resistance

Abstract

This power electronics module (25) comprises a housing (33), a substrate (29), at least one electronic component (27) mounted on the substrate (29), a gel (31) encapsulating said electronic component (27) within the housing (33), and a first power connection (35) mounted on the substrate (29) and having one end extending outside the housing (33) along an external surface (37) of the housing (33) so as to be connected to an external connection bar (39). The module (25) further comprises a second, foldable power connection (41) mounted on the substrate (29) and configured to be connected to the same external connection bar (39) as the first power connection (35) when folded. (See Figure 2 for abbreviations.)

Description

Title of the invention: Dual-connection power electronics module for reducing contact resistance. Technical field

[0001] The present invention relates to the field of power electronics modules.

[0002] In particular, the present invention relates to the reduction of losses in the power connections of a power electronics module by reducing the contact resistance. Previous techniques

[0003] Power electronics modules are subsets of power electronics that allow several power electronic components to be integrated within the same package to perform more or less complex functions, such as energy conversion.

[0004] A schematic cross-sectional view of an assembly 1 comprising a power electronics module 3 and a heat sink 5 according to the prior art has been shown in [Fig.1].

[0005] A power electronics module 3 generally comprises electronic components 7 assembled on an electrically insulating and thermally conductive substrate 9. These electronic components 7 are attached in most cases to said substrate 9 by brazed or sintered joints. The electrical connections between the electronic components 7 are made through the substrate 9 and / or by wires, and / or by ribbons, and / or by clips.

[0006] A heat sink 5 is generally positioned against the substrate 9, optionally via a base plate, to dissipate the heat generated by the electronic components 7 during their operation, for example, by means of metal fins. The power electronics module 3 also includes a gel 11 encapsulating the electronic components 7 on the substrate 9. A housing 13, also called a "ringframe," provides support and protection for the gel 11, the electronic components 7, and the substrate 9.

[0007] A power electronics module 3 also includes at least one power connection 15 brazed onto the substrate, allowing it to be connected to other power electronic modules or components. For this purpose, the power connection 15, most often made of copper and coated with a surface treatment, extends from the housing 13 along its length and can be connected by contact to an external connection bar 17. The power connection 15 and the external connection bar 17 are secured by passing a screw 19 through the bar. external connection 17, power connection 15 and housing 13. To facilitate fixing, a nut 21 can be taken into the mass of the housing 13 and a washer 23 can be positioned between the head of the screw 19 and the external connection bar 17.

[0008] A high-power electronics module integrates several chips in parallel, making it possible to increase the current capacity of said module. Furthermore, advances in microelectronics make it possible to achieve increasingly lower on-state resistances, thus increasing the currents flowing through said module for the same junction temperature.

[0009] Conversely, the power connections 15 of the modules have not changed.

[0010] These power connections 15 benefit from the cooling provided by the heatsink 5 on the substrate side 9, but are poorly cooled when they move away from the substrate 9, particularly outside the housing 13. The losses in these power connections 15 are essentially related to the contact resistance between the power connection 15 and the external connection bar 17.

[0011] As described previously, increasing power in power electronics requires increasing currents. This increase in current is only possible through the use of components with low on-state resistance, thus limiting thermal losses.

[0012] However, the increase in current will generate additional losses at the power connections 15 due to contact resistances.

[0013] These losses will be difficult to eliminate because these power connections 15 are located outside the module 3 and therefore do not benefit from the cooling provided by the heat sink 5.

[0014] It is therefore necessary to reduce contact resistances, in order to guarantee the thermal resistance of the power connections 15. Description of the invention

[0015] The present invention therefore aims to overcome the aforementioned disadvantages and to provide a power electronic module enabling an increase in the power passing through them.

[0016] The present invention relates to a power electronics module comprising a housing, a substrate, at least one electronic component mounted on the substrate, a gel encapsulating said electronic component in the housing, and a first power connection mounted on the substrate on one side and having one end extending on the other side outside the housing along an external surface of the housing so as to be connected to an external connection bar, the module comprising a second flexible power connection mounted on the substrate and configured to be connected to the same external connection bar as the first power connection when folded.

[0017] Thus, the second power connection increases the contact area with the external connection bar without compromising the compactness of the power electronics module. Since contact resistance is related to the contact area, this increased contact area between the power connections and the external connection bar reduces contact resistance, thereby allowing for increased current and power flow through the power electronics module. A current of 400 Amperes can thus flow, whereas only 200 Amperes could flow with a single power connection.

[0018] Advantageously, the first and second power connections are configured to accommodate, by sandwich-type contact between them, a portion of the external connection bar.

[0019] In one embodiment, the housing includes a nut taken from its mass, the module further including a screw configured to pass through in this order the second power connection, the external connection bar, the first power connection and the nut so as to hold the connection made in place.

[0020] Advantageously, and with equivalent cross-section, the respective lengths of the first and second power connections are equivalent between their respective last point of contact with the external connection bar and the substrate.

[0021] In a particular embodiment, the first and second power connections have a cross-section thickness between 0.5 mm and 5 mm.

[0022] Advantageously, the housing includes a rounded protrusion positioned between the respective ends of the first and second power connections extending outside the housing, the protrusion being configured to facilitate the folding of the second power connection onto the external connection bar.

[0023] Advantageously, the housing includes a removable tooling support configured to facilitate bending the second power connection onto the external connection bar, and the housing includes a removable tooling configured to facilitate bending the second power connection onto the external connection bar.

[0024] In a particular embodiment, the tooling includes a lever configured to multiply the force of an operator tenfold in order to simplify the bending of the second power connection on the external connection bar.

[0025] Advantageously, the first and second power connections have two dimensions at least ten times greater than their third dimension, and are each configured to have a contact surface with the external connection bar of between 0.1 and 10 square centimeters.

[0026] The present invention also relates to a method for connecting an external connection bar to a power electronics module as defined above, comprising the following steps:

[0027] - Positioning an external connection bar on the first connection of power ;

[0028] - Folding the second power connection so as to sandwich the external connection bar between the first and second power connections; and

[0029] - Insertion of a screw through the second power connection, of the bar external connection, and the first power connection. Brief description of the drawings

[0030] Other objects, features and advantages of the invention will become apparent from the following description, given solely by way of non-limiting example, and made with reference to the accompanying drawings in which:

[0031] [Fig-1] is a schematic cross-sectional view of an assembly comprising a module power electronics and a heat sink according to the state of the art;

[0032] [Fig.2] is a schematic cross-sectional view of a power electronics module according to the invention;

[0033] [Fig.3] is a schematic cross-sectional view of a particular embodiment of the power electronics module according to [Fig.2]; and

[0034] [Fig.4] is a representation of the steps in the process of connecting a bar external connection to a power electronics module according to the invention.

[0035] Detailed description of at least one embodiment

[0036] A schematic cross-sectional view of a power electronics module 25 according to the invention is shown in [Fig.2].

[0037] The power electronics module 25 comprises at least one electronic component 27, an electrically insulating and thermally conductive substrate 29 onto which the electronic component(s) 27 are mounted, for example, by brazed or sintered joints. The electrical connections between the electronic components 27 are made via the substrate 29 and / or by wires, and / or by ribbons, and / or by clips.

[0038] Optionally, a heat sink can be attached to the power electronics module 25.

[0039] The power electronics module 25 also includes a gel 31 encapsulating the electronic components 27 on the substrate 29. A housing 33 allows the gel 31, the electronic components 27 and the substrate 29 to be held and protected.

[0040] The housing 33 is, for example, attached to the substrate 29 by fastening means (not shown) positioned at the ends of said substrate 29. The substrate 29 is less than one centimeter thick. Its other dimensions extend along a plane, for example, a polygonal plane. The fastening means of the substrate 29 to the housing 33 are then fixed at the edge of the polygon defining the shape of the substrate 29.

[0041] The housing 33 may comprise a plastic material. It covers, without being in contact with, a face of the substrate 29 on which the electronic components 27 are mounted.

[0042] The substrate 29 is for example an AMB type substrate (“Active Metam Brazed” in Anglo-Saxon terms), or a DBC type substrate (“Direct Bonded Copper” in Anglo-Saxon terms), or even an SMI type substrate, in other words an electrically insulated and thermally conductive metallic substrate.

[0043] The electronic component(s) 27 are, for example, semiconductor chips, and / or diodes, and / or transistors.

[0044] The power electronics module 25 also includes a first power connection 35 carried on the substrate 29 on one side and one end of which extends on the other side outside the housing 33 along an external surface 37 of the housing 33 so as to be connected to an external connection bar 39.

[0045] The power electronics module 25 further includes a second foldable power connection 41 carried on the substrate 29 and configured to be connected to the same external connection bar 39 as the first power connection 35 when folded.

[0046] For example, the first and second power connections 35 and 41 are equivalent to communication buses whose cross-sectional area is between 1 and 1000 square millimeters, preferably between 400 and 600 square millimeters, and whose cross-sectional thickness is between 0.5 mm and 2 mm, preferably between 1 mm and 1.5 mm.

[0047] Optionally, with equivalent cross-sections, the respective lengths of the first and second power connections 35 and 41 are equivalent between their respective last points of contact with the external connection bar and the substrate. Indeed, as shown in [Fig. 2], the length of the second power connection 41 is greater than the length of the first power connection 35, since potentially more current flows through the first power connection 35 than through the second power connection 41, thus making the presence of the second connection of power 41 less efficient. Equalizing their length helps to reduce this effect.

[0048] The first and second power connections 35 and 41 are made, for example, of copper and are optionally coated with a surface treatment. The first and second power connections 35 and 41 are brazed or sintered onto the substrate 29 and allow the power electronics module 25 to be connected to other power electronic modules or components via the external connection bar 39.

[0049] In particular, the first and second power connections 35 and 41 are configured to be positioned on either side of a portion of the external connection bar 39 so as to sandwich it.

[0050] Advantageously, the first and second power connections 35 and 41 have two dimensions at least ten times greater than their third dimension, namely their thickness, in other words the thickness of their section.

[0051] The first and second power connections 35 and 41 are each configured to have a contact area with the external connection bar of between 0.1 and 10 square centimeters, preferably between 4 and 6 square centimeters.

[0052] The housing 33 includes a nut 43 tapped and taken from the mass of said housing 33, the power electronics module 25 further including a threaded screw 45 configured to pass through in this order the second power connection 41, the external connection bar 39, the first power connection 35 and the nut 43 so as to secure the power connections 35 and 41 to the external connection bar 39.

[0053] Obviously, perforations must first be made in the power connections 35 and 41 as well as in the external connection bar 39.

[0054] A washer 47 can be positioned between the head of the screw 45 and the second power connection 4L

[0055] Figure 2 illustrates the power electronics module 25 once the bar of External connection 39 is installed.

[0056] Figure 3 schematically represents a cross-sectional view of the power electronics module 25 according to a particular embodiment and before the external connection bar 39 is fully installed. The power electronics module 25 can, for example, be delivered in this configuration to a user who will then need to perform an operation to install the second power connection 41 on the external connection bar 39.

[0057] In this embodiment, the housing 33 includes a rounded protrusion 49 positioned between the respective ends 51 and 53 of the first and second power connections 35 and 41 extending outside the housing 33, the protrusion 49 being configured to facilitate folding the second power connection 41 onto the external connection bar 39.

[0058] In particular, by exerting a lever arm type force on the second power connection 41, the latter will bear on the protrusion 49 and will deform, in other words bend, so as to position itself on the external connection bar 39 which will have been positioned beforehand.

[0059] The protrusion 49 is for example of a height configured so that the second power connection 41 is directly at the height of the external connection bar 39 after folding.

[0060] To facilitate folding, the housing 33 includes a removable tool 55 configured to facilitate folding the second power connection 41 onto the external connection bar 39, the tool 55 preferably including a lever 55 configured to multiply the force of an operator so as to simplify the folding of the second power connection 41 onto the external connection bar 39.

[0061] Advantageously, the housing 33 includes a tool holder 57 for the tool 55. The holder 57 is, for example, in the form of a fastening means to which the tool 55 can be removably attached. Once the folding is complete, the tool 55 can therefore be removed from the power electronics module 25.

[0062] The steps of the method of connecting the external connection bar 39 to the power electronics module 25 according to the invention have been schematically represented in [Fig.4].

[0063] A step 59 is first carried out of positioning the external connection bar 39 on the first power connection 35.

[0064] Then, step 61 is performed, folding the second power connection 41 so as to sandwich the external connection bar 39 between the first and second power connections 35 and 4L

[0065] Finally, a step 63 is carried out of inserting the screw 45 through the second power connection 41, the external connection bar 39, and the first power connection 35.

Claims

Demands

1. Power electronics module (25) comprising a housing (33), a substrate (29), at least one electronic component (27) mounted on the substrate (29), a gel (31) encapsulating said electronic component (27) in the housing (33) and a first power connection (35) mounted on the substrate (29) on the one hand and having one end extending on the other hand outside the housing (33) along an external surface (37) of the housing (33) so as to be connected to an external connection bar (39), characterized in that it comprises a second foldable power connection (41) mounted on the substrate (29) and configured to be connected to the same external connection bar (39) as the first power connection (35) when folded.

2. Module (25) according to claim 1, wherein the first and second power connections (35; 41) are configured to accommodate by sandwich-type contact between them a portion of the external connection bar (39).

3. Module (25) according to any one of claims 1 and 2, wherein the housing (33) includes a nut (43) taken from its mass, the module (25) further comprising a screw (45) configured to pass through in this order the second power connection (41), the external connection bar (39), the first power connection (35) and the nut (43) so as to maintain the connection made in place.

4. Module (25) according to any one of claims 1 to 3, wherein, at equivalent cross-section, the respective lengths of the first and second power connections (35; 41) are equivalent between their respective last point of contact with the external connecting bar (39) and the substrate (29).

5. Module (25) according to any one of claims 1 to 4, wherein the first and second power connections (35; 41) have a cross-section thickness between 0.5 mm and 2 mm.

6. Module (25) according to any one of claims 1 to 5, wherein the housing (33) comprises a rounded protrusion (49) positioned between the respective ends (51; 53) of the first and second power connections (35; 41) extending outside the housing (33), the protrusion (49) being configured to facilitate folding of the second power connection (41) onto the external connection bar (39).

7. Module (25) according to any one of claims 1 to 6, wherein the housing (33) includes a removable tooling (55) support (57) configured to facilitate folding the second power connection (41) onto the external connection bar (39), and a removable tooling (55) configured to facilitate folding the second power connection (41) onto the external connection bar (39).

8. Module (25) according to claim 7, wherein the tooling (55) includes a lever configured to multiply the force of an operator tenfold so as to simplify the bending of the second power connection (41) onto the external connection bar (39).

9. Module (25) according to any one of claims 1 to 8, wherein the first and second power connections (35; 41) have two dimensions at least ten times greater than their third dimension, and are each configured to have a contact area with the external connecting bar (39) of between 0.1 and 10 square centimeters.

10. A method for connecting an external connecting bar (39) to a power electronics module (25) according to any one of claims 1 to 9, comprising the following steps: - Positioning (step 59) of an external connecting bar (39) on the first power connection (35); - Bending (step 61) of the second power connection (41) so as to sandwich the external connecting bar (39) between the first and second power connections (35; 41); and - Inserting (step 63) of a screw (45) through the second power connection (41), the external connecting bar (39), and the first power connection (35).

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