Electrical assembly, in particular for an inverter

Abstract

The invention relates to an electrical assembly (1), in particular for an inverter, comprising: - a printed circuit board (2) comprising at least one conductive track (3) on the surface, - an electrical connection piece (5) in electrical contact with a conductive track of the printed circuit board (2), the electrical connection piece (5) being secured to the printed circuit board (2) and having a thickness at least 10 or 20 times greater than the thickness of the conductive track on the surface, in order to allow assembly by laser welding between this electrical connection piece (5) and a power busbar (20) to be connected to the electrical assembly.

Description

[0001] DESCRIPTION

[0002] Title: Electrical assembly, particularly for an inverter

[0003] [1] The present document relates in particular to an electrical assembly, specifically for an inverter.

[0004] [2] Power modules (or "Power Modules" in English) manufactured by material transfer molding are known and are connected to power busbars (also referred to in English as "Busbar") by laser welding, for example, during their integration into an inverter. In these power modules, laser welding can be performed satisfactorily, melting the copper of both parts (busbar + copper block) to create the mechanical joint.

[0005] [3] Another technology for manufacturing power modules uses a printed circuit board with conductive traces to be connected to power busbars.

[0006] [4] The present invention proposes in particular an innovative solution for making the electrical connection between a conductive track of a printed circuit board and a power busbar.

[0007] [5] The invention thus relates to an electrical assembly, in particular for an inverter, comprising:

[0008] - a printed circuit board comprising at least one conductive trace on its surface,

[0009] - an electrical connection piece in electrical contact with a conductive track of the printed circuit board, the electrical connection piece being integral with the printed circuit board and having a thickness at least 5 times greater than or equal to the thickness of the conductive track on the surface to allow assembly by laser welding between this electrical connection piece and a power busbar to be connected to the electrical assembly.

[0010] [6] The invention overcomes a difficulty in making an electrical connection between a conductive trace on a printed circuit board and a power busbar, a difficulty arising from the fact that the power busbar is generally quite thick (approximately 2 mm) while the conductive trace on the surface of the printed circuit board is much thinner (for example, a maximum thickness of 70 microns). [7] A significant difference in thickness between the power busbar and the conductive trace on the surface of the printed circuit board poses a problem because, for laser welding, the laser power must be controlled.Laser welding is done by penetration, as the power busbar is placed on the conductive track and the laser must first pass through the thickness of the power busbar before reaching the conductive track underneath, to melt part of the power busbar and the conductive track and make the mechanical joint.

[0011] [8] A laser with too high a power that reaches the conductive track may present a risk of degradation of the insulating material of the printed circuit board.

[0012] [9] The invention overcomes this problem by means of the electrical connection piece, which has sufficient thickness to stop the laser power transmitted through the power busbar. The invention thus makes it possible to avoid, in a simple and economical manner, degradation of the insulating material of the printed circuit board. Therefore, in the present invention, only one additional part (the electrical connection piece) is used to perform the electrical assembly by laser welding.

[0013]

[0010] According to one aspect of the invention, the electrical connection piece has a thickness greater than or equal to at least 10 times, or at least 20 times, or at least 30 times, or at least 40 times, or at least 50 times, the thickness of the conductive track on the surface of the printed circuit board.

[0014]

[0011] According to one aspect of the invention, the electrical connection piece is a block of metal, in particular copper.

[0015]

[0012] The electrical connection piece may have a bar-like shape, for example substantially in the shape of a paving stone. Alternatively, the electrical connection piece may have a cylindrical shape.

[0016]

[0013] According to one aspect of the invention, the thickness of the electrical connection piece is at least greater than 0.3 times the thickness of the power busbar.

[0017]

[0014] According to one aspect of the invention, the thickness of the electrical connection piece is substantially equal to the thickness of the power busbar.

[0018]

[0015] Thickness is a dimension measured along an axis perpendicular to the plane of the printed circuit board.

[0019]

[0016] According to one aspect of the invention, the electrical connection piece is configured to be completely covered by the power busbar.

[0020]

[0017] According to one aspect of the invention, the electrical connection piece is mounted on the surface of the printed circuit board, on a conductive track.

[0018] According to one aspect of the invention, the electrical connection piece, which is mounted on the surface of the printed circuit board, is soldered to the conductive track.

[0021]

[0019] For example, the electrical connection piece is soldered onto the conductive track with tin, in particular by passing through a furnace.

[0022]

[0020] In another embodiment of the invention, the printed circuit board has a cavity configured to receive the electrical connection piece.

[0023]

[0021] For example, the cavity is formed by overmolding the insulating material forming the printed circuit board.

[0024]

[0022] Alternatively, the electrical connection piece is presented as an insert inserted into the cavity, in particular by force. In this case, for example, the electrical connection piece is not soldered to the printed circuit board.

[0025]

[0023] According to one aspect of the invention, the electrical connection piece is connected to one or more conductive tracks of the printed circuit board, for example by electrical vias formed in the electronic board.

[0026]

[0024] For example, the conductive track of the printed circuit board and the power busbar are made of copper.

[0027]

[0025] According to one aspect of the invention, the printed circuit board comprises several layers of electrically insulating material between which conductive tracks are present.

[0028]

[0026] According to one aspect of the invention, the printed circuit board includes at least one transistor, in particular buried within the printed circuit board, for switching electrical power.

[0029]

[0027] According to one aspect of the invention, the printed circuit board includes electrical vias for making electrical connections between different elements of the printed circuit board.

[0030]

[0028] The invention also relates to a power module comprising an electrical assembly as described above.

[0031]

[0029] The invention further relates to a voltage converter comprising an electrical assembly as described above, with an electrical connection between the electrical connection piece of the printed circuit board and a power busbar.

[0032]

[0030] According to one aspect of the invention, the voltage converter comprises the power module connected to the power busbar.

[0031] The invention further relates to an inverter comprising an electrical assembly as described above, with an electrical connection between the electrical connection piece of the printed circuit board and a power busbar.

[0033]

[0032] The invention also relates to an inverter comprising a voltage converter as described above.

[0034]

[0033] Other features, details and advantages of the invention will become clearer upon reading the following description on the one hand, and several illustrative and non-limiting examples of embodiments given with reference to the accompanying schematic drawings on the other hand, in which:

[0035]

[0034] [Fig 1] Figure 1 is a schematic and partial representation of a power module according to an example of an embodiment of the invention;

[0036]

[0035] [Fig. 2] Figure 2 is a cross-sectional view of the power module of Figure 1;

[0037]

[0036] [Fig. 3] Figure 3 is a cross-sectional view of a power module according to another embodiment of the invention.

[0038]

[0037] The features, variants, and different embodiments of the invention can be combined in various ways, provided they are not incompatible or mutually exclusive. In particular, variants of the invention may be conceived comprising only a selection of features, described hereafter in isolation from the other described features, if this selection of features is sufficient to confer a technical advantage and / or to differentiate the invention from the prior art.

[0039]

[0038] Figures 1 and 2 show a power module 100 of an inverter, comprising an electrical assembly 1 according to an example of an embodiment of the invention.

[0040]

[0039] Electrical assembly 1 comprises:

[0041] - a printed circuit board 2 (also referred to in English as "Printed Circuit Board" or PCB) having at least one conductive track 3 on the surface (namely a conductive track present on an external face of the printed circuit board 2),

[0042] - an electrical connection piece 5 in electrical contact with the conductive track 3 of the printed circuit board 2, the electrical connection piece 5 being integral with the printed circuit board 2 and having a thickness at least 10 or 20 times greater than the thickness of the conductive track 3 on the surface to allow assembly by laser welding between this electrical connection piece 5 and a power busbar 20 (also referred to in English as "Busbar") to be connected to the electrical assembly 1.

[0043]

[0040] The electrical connection piece 5 has a thickness equal to at least 5 times, or at least 20 times, or at least 30 times, or at least 40 times, or at least 50 times, the thickness of the conductive track 3 on the surface of the printed circuit board 2.

[0044]

[0041] In the example described, the power busbar 20 generally has a large thickness of approximately 2 mm while the conductive track 3 on the surface of the printed circuit board has a much smaller thickness of approximately 70 microns.

[0045]

[0042] The printed circuit board 2 comprises several layers 19 of electrical insulating material between which are present conductive tracks 21.

[0046]

[0043] The printed circuit board 2 includes at least one transistor, in particular buried within the printed circuit board 2, for switching electrical power.

[0047]

[0044] The printed circuit board 2 includes electrical vias for making electrical connections between different elements of the printed circuit board 2.

[0048]

[0045] The conductive track 3 of the printed circuit board 2 and the power busbar 20 are made of copper.

[0049]

[0046] The electrical connection piece 5 is a block of metal, in particular copper, and may have a bar shape, for example substantially in the shape of a paving stone.

[0050]

[0047] Here, the thickness of the electrical connection piece 5 is substantially equal to the thickness of the power busbar 20.

[0051]

[0048] Thickness is a dimension measured along an axis perpendicular to the plane of the printed circuit board 2.

[0052]

[0049] Laser welding is illustrated in Figure 2 by the W shape of the laser beam which passes through and melts the copper of the power busbar 20 and the electrical connection piece 5.

[0053]

[0050] The electrical connection piece 5 is configured to be completely covered by the power busbar 20.

[0054]

[0051] The electrical connection piece 5 is mounted on the surface of the printed circuit board 2, on a conductive track 3, and is soldered to the conductive track 3.

[0055]

[0052] For example, the electrical connection piece 5 is soldered onto the conductive track 3 with tin 30, in particular by passing through a furnace.

[0056]

[0053] In another embodiment of the invention illustrated in Figure 3, the printed circuit board 2 has a cavity 17 configured to receive the electrical connection piece 15. For example, an electrically insulating material is overmolded around the electrical connection piece 15. Again, for example, this overmolding step can be carried out at the same time as the overmolding step of the conductive tracks 3.

[0057]

[0054] Alternatively, the electrical connection piece 15 is presented as an insert inserted into the cavity 17, in particular by force-inserting into the cavity 17. In this case, for example, the electrical connection piece 5 is not soldered onto the printed circuit board 2.

[0058]

[0055] The electrical connection piece 15 is connected to one or more conductive tracks of the printed circuit board 2, for example by electrical vias formed in the electronic board.

Claims

DEMANDS

1. Electrical assembly (1), in particular for an inverter, comprising: - a printed circuit board (2) comprising at least one conductive trace (3) on its surface, - an electrical connection piece (5) in electrical contact with a conductive track of the printed circuit board (2), the electrical connection piece (5) being integral with the printed circuit board (2) and having a thickness at least 5 times greater than or equal to the thickness of the conductive track on the surface to allow assembly by laser welding between this electrical connection piece (5) and a power busbar (20) to be connected to the electrical assembly.

2. Electrical assembly according to the preceding claim, wherein the electrical connection piece (5) has a thickness greater than or equal to at least 10 times, or at least 20 times, or at least 30 times, or at least 40 times, or at least 50 times, the thickness of the conductive track on the surface of the printed circuit board (2).

3. Electrical assembly according to any one of the preceding claims, wherein the electrical connection piece (5) is a block of metal, in particular copper.

4. Electrical assembly according to any one of the preceding claims, wherein the electrical connecting piece (5) has a bar shape.

5. Electrical assembly according to any one of the preceding claims, wherein the electrical connection piece (5) is mounted on the surface of the printed circuit board (2), on a conductive track (3), being soldered to the conductive track.

6. Electrical assembly according to any one of claims 1 to 4, wherein the printed circuit board (2) has a cavity (17) configured to receive the electrical connection piece (15).

7. Voltage converter comprising an electrical assembly according to any one of the preceding claims, with an electrical connection between the electrical connection piece of the printed circuit board (2) and a power busbar (20).

8. Voltage converter according to the preceding claim, wherein the thickness of the electrical connection piece (5) is at least greater than 0.3 times the thickness of the power omnibus bar (20).

9. Voltage converter according to claim 7 or 8, wherein the thickness of the electrical connection piece (5) is substantially equal to the thickness of the power busbar (20).

10. Voltage converter according to any one of claims 7 to 9, wherein the electrical connection piece (5) is configured to be completely covered by the power busbar (20).

11. Inverter comprising a voltage converter according to any one of claims 7 to 10.

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