Electronic power board

Abstract

The present invention relates to an electronic power board (1) comprising: - a capacitive laminated bus bar (2) in the form of a first stack of two metal layers, particularly copper, namely an inner metal layer and an outer metal layer (4) separated from each other by a first layer of electrically insulating material; - a layer of thermal interface material disposed between said first stack and a metal base; - an integrated current sensor comprising a magnetic flux concentrator (9) inserted into openings made in the metal base, said magnetic flux concentrator (9) containing a second stack of layers comprising a second layer of electrically insulating material, a layer of material conductive to the current to be measured, a printed circuit board (PCB), and a current measurement component. Figure for the abstract: Fig 2

Description

Title of the invention: Electronic power board technical field

[0001] The present invention relates to power electronic design, and more particularly to the design of electronic power boards incorporating, for example, semiconductors. These power boards are generally implemented in applications related to the conversion of electrical energy in various fields. These may include the automotive or aeronautical transport sector (electric and hybrid motors for automobiles in particular) and the energy sector (self-consumption of electricity in a home / building, applications to smart grids, vehicle-to-grid (V2G) applications, etc.). Previous technique

[0002] There are many configurations for this type of card, each with its own advantages and disadvantages. One challenge that must be addressed during their design is ensuring the most efficient possible dissipation of the heat generated within the card. French patents FR 2801 725 and US8232637 tackle this issue: the former uses an external heat sink adapted to the desired power output, which increases the overall size of the system, while the latter incorporates cooling fluid channels within the card, which complicates its design and operation.

[0003] Another issue is the compactness of the board, and there is a real need for the integration of all electrical / electronic components into a single system, which can be as compact / integrated as possible.

[0004] The invention then aims at the design of an improved power board. In particular, it aims at a board that allows greater integration of its components, while maintaining, or improving, its performance in terms of thermal dissipation. Summary of the invention

[0005] The invention relates firstly to an electronic power board comprising - a laminated capacitive bus bar in the form of a first stack of two layers of metal, in particular copper, namely an inner metallic layer and an outer metallic layer separated from each other by a first layer of electrically insulating material, - a layer of thermal interface material disposed between said first stack and a metal base, - an integrated current sensor comprising a magnetic flux concentrator (9) which is inserted into openings made in the metal base, said magnetic flux concentrator containing a second stack of layers comprising a second layer of electrically insulating material, a layer of material conductive with respect to the current to be measured, a printed circuit board called PCB, and a current measurement component.

[0006] This card is in particular of the insulated metallic substrate (IMS) type, specifically multilayered, for example with two, three or four layers, preferably single-sided. In one embodiment, it is a two-layer, single-sided insulated metallic substrate.

[0007] The term “bus bar”, although of Anglo-Saxon origin, is well known in the field of electronic boards, and can be translated by the French term interconnection bar or even electrical distribution bar.

[0008] The term "sole" is also well known in the field of electronic boards, and corresponds to the support of the board, on which the layers and components are deposited.

[0009] The invention thus proposes a power board which can integrate electronic and / or mechanical and / or electromechanical functions, and whose design allows, in particular, the integration of different components, in particular new generation semiconductor components known as wide band gap components, also known under the Anglo-Saxon term of "Wide Band Gap" components, within high power density converters.

[0010] To achieve this, the invention uses a multi-layer metal (usually copper) SMI-type board rather than a single-layer board: a laminated bus bar is thus constructed according to the invention, with two metallic layers, which can be connected respectively to the positive and negative potentials of a voltage source, for example, an electric battery, to which the board is intended to be connected. Compared to a conventional power module, the board according to the invention, with this laminated bus bar to which ceramic capacitors can be added, will eliminate, or at least drastically reduce, the inductive effects related to the length of the loops between the positive and negative potentials in question. Indeed, the ceramic capacitors can be placed as close as possible to the semiconductor components.

[0011] Another advantage of the card according to the invention is that it can be manufactured using conventional manufacturing techniques, in particular with any EMS type tooling (for the acronym of the Anglo-Saxon term "Electronic Manufacturing Service"): It is therefore inexpensive / simple to produce. Furthermore, it remains compatible with most standard discrete packages for surface-mount semiconductor components.

[0012] Preferably, the magnetic flux concentrator has a bottom wall, in particular square or parallelepiped in shape, and side walls, two of said side walls, in particular opposite walls, being inserted into two openings made in the metal base.

[0013] Preferably, the second stack is attached to the inner face of the portion of the base located between the two openings, and the opposite face of said portion of the base is attached to the bottom wall of the magnetic flux concentrator, in particular by a layer of adhesive. The term "inner face" refers to the face on the side of the stack in question.

[0014] This concentrator thus has, for example, a U-shaped form, with a flat bottom wall that receives the second stack, and two side walls extending perpendicularly from two of its opposite edges to the flat wall. These side walls, by fitting into the openings in the metal base, press the bottom wall with the second stack against one face of the portion of the base located between the two openings, while the side walls pass through the base via its openings and extend along the opposite face of said base. The other face of the portion of the base in question supports the second stack.

[0015] Advantageously, the inner and / or outer metallic layers can extend relative to each other so as to provide at least one accessible area on the outer surface of each of the outer and inner layers, in particular to form tracks for attaching components, notably by soldering, including at least one component selected from among AC connectors, DC connectors, capacitors, power semiconductors, and DC or AC voltage measurement components. In fact, the outer layer only partially covers the inner layer; areas of the inner layer "protrude" beyond the extent of the outer layer so as to be accessible.The outer layer can also "extend" beyond the extent of the inner layer: they therefore do not have the same extent, even if the majority of their surfaces overlap (via the intermediate layer of electrical insulation).

[0016] Preferably, the first part of the outer metal layer of the first stack is provided with a protective coating of varnish-type material (not shown), and other parts of said outer metal layer are uncoated and constitute tracks for attaching, in particular by soldering, components, in particular at least one selected from AC or DC connectors, capacitors, power semiconductors, phase voltage measurement components. Indeed, it is known to protect the external metallic layer with a protective varnish, and it is therefore possible to choose to selectively remove the varnish in certain areas (or to deposit it selectively) to leave one or more "bare" areas for connecting / fixing components.

[0017] Advantageously, the card according to the invention comprises at least one capacitor, in particular of the ceramic type, and / or at least one DC- and DC+ direct current electrical connector, which is fixed, in particular by soldering, respectively by their positive terminal on the external metal layer and by their negative terminal on the internal metal layer of the first stack.

[0018] Advantageously, the card according to the invention comprises at least one AC current connector and / or at least one power semiconductor fixed to the outer metal layer and / or to the inner metal layer. The outer and inner metal layers are then preferably equipped with vias directly above the location of said AC current connector(s) and / or said power semiconductor(s). These vias (or microvias) are, in a known manner, made in the form of pins, of electrically conductive material, which are placed between the two layers and in contact with them, thus ensuring the distribution of current between the two metal layers and also acting as heat sinks.

[0019] The card according to the invention may include at least one DC or AC voltage measurement component, fixed, in particular by welding, on the external metal layer or on the internal metal layer of the first stack.

[0020] Advantageously, the board may include components capable of emitting heat during operation, fixed to the inner or outer metal layer, in particular at least one power semiconductor and / or at least one connector, particularly for AC current, and the outer and inner metal layers are equipped with vias in the vicinity of said components. These vias (or microvias), as indicated above, ensure current sharing between the two layers, but in addition, here they promote the heat dissipation of the components most likely to generate heat, which is the case for the power semiconductors and the AC current connectors, towards the metal base of the board.

[0021] According to one embodiment, the metal base plate is thermally connected to a heat-dissipating component, which is external to the board. In this case, its thickness is conventional, for example on the order of 1 to 5 mm.

[0022] According to another embodiment, the face of the metal base opposite that supporting the second layer of electrically insulating material has three-dimensional patterns, in particular fins. The base of the card thus becomes the heat-dissipating component of the card, thereby eliminating the need for an external heat-dissipating component (or at least reducing the need for one). (less efficient / less bulky heat sink component). This achieves an additional level of integration for the board.

[0023] The invention also relates to any multilayer SMI type power card whose base is thus configured.

[0024] In particular, in this embodiment, a fairly thick metal sole can be provided, for example at least 5 mm, or more than 5 mm, in particular at least 8 or 10 mm, and even several tens of millimeters. Its thickness can notably be between 10 and 30 mm or between 10 and 20 mm, so as to have sufficient thickness to engrave the fin-type or stud-type patterns while maintaining the continuity of the sole.

[0025] According to yet another embodiment, the face of the metal base opposite that supporting the second layer of electrically insulating material is provided, notably by brazing or additive manufacturing, with a layer, particularly continuous or discontinuous, of metallic material having three-dimensional surface patterns, such as fins. Here, a heat-dissipating component is thus integrated by attaching it to the base.

[0026] Advantageously, the card according to the invention comprises power semiconductors: it forms a control inverter for an electrical machine, said inverter comprises a plurality of switching arms, each switching arm comprising power semiconductors.

[0027] The invention also relates to the use of the card described above to control the power supply of an electric machine (an electric motor). Description of embodiments

[0028] The invention will be described below in more detail with the aid of figures and non-limiting examples implementing it. List of figures

[0029] [Fig.1] Figure 1 is a schematic representation of a voltage inverter type power stage. [Fig.2] Figure 2 is a top view representation of an example of a map according to the invention. [Fig.3] [Fig.3] is a cavalier view representation of the example map according to the invention according to [Fig.2]. [Fig.4] Figure 4 is a simplified representation of a portion of the example map according to Figures 2 and 3. [Fig. 5] Figure 4 is a simplified representation of a variant of the portion of the example map according to figures 2 and 3. [Fig.6] Fig. 6 is a representation of the metal base of an example card according to the invention, conforming to Fig. 4. [Fig.7a] and [Fig.7a] Figures 7a and 7b represent the two layers of metal (Cu) used in an example of a card, as shown in particular in figures 2 and 3. [Fig.8] Figure 8 is a simplified representation of a magnetic concentrator integrated into an example of a card according to the invention, as shown in particular in Figures 2 and 3.

[0030] The figures are not limiting, are extremely schematic for at least some of them, and do not necessarily respect the scale between the different components shown.

[0031] The same references designate, from one figure to another, the same components / elements.

[0032] An example of a non-limiting map will be described below with the help of the various figures: Figure 1 shows the electronic schematic of an example of a circuit board according to the invention, in accordance with conventions known in the field. It shows: - DC current connections 18,19 at the positive and negative terminals (DC+ and DC-) - a laminated capacitive bus bar with two layers of metal (copper), which actually corresponds to an assembly including connectors 18, 19 and capacitors 20 - 21 power semiconductors - electromechanical AC 16 current connectors - 8 current sensors - 20 ceramic capacitors

[0033] Figures 2 and 3 are complementary views of an example of a card implementing this electronic scheme: they show a card 1 comprising power semiconductors 21, the outer metal layer 4 of the laminated bus bar 2 (described later), DC current connectors 18, 19, electromechanical AC current connectors 16, ceramic-type capacitors 20, current sensors integrated into magnetic concentrators 9 (detailed later), all these components being fixed / connected to the laminated bus bar 2 as detailed later, vias 23 to ensure electrical continuity between the two metal layers 3 and 4, particularly in the area of ​​the AC connector, and / or to facilitate heat dissipation in the vicinity of components most likely to give off heat, including power semiconductors, and finally a metal base 7.

[0034] Figure 4 shows a simplified cross-sectional view of a portion of the structure of the laminated capacitive bus bar 2: it comprises an electrical insulating layer 5 arranged between an internal metallic (copper) layer 3 and an external metallic (copper) layer 4, constituting a first stack. The electrical insulating layer 5 may, for example, be polymer-based, polyimide-based, or epoxy-based, possibly reinforced, for example, with glass fibers, such as those marketed by Arlon. This first stack is secured by its internal metallic layer 3 to the metallic base 7 by a layer 6 of thermal interface material. This layer 6 can also be polymer-based, particularly those designated as Controlled Thermal Expansion (CTEA) polymers, notably those marketed by Arlon Electronics under the name SMT, which can be epoxy or polyimide-based, reinforced with woven or non-woven aramid. The base 7 is preferably made of aluminum.

[0035] Figure 5 is a variant of Figure 4 concerning the shape of the sole: here, the sole 7' is shaped to have raised features, such as fins or studs, on its outer face (i.e., the face opposite to that in contact with layer 6), in order to create a large surface area for heat exchange with the outside. The sole can then fully act as an integrated heat sink, making it possible to eliminate any external heat sink (or at least to use one that is less efficient or more compact than the one conventionally required). In this case, we can plan for a fairly thick sole, several millimeters thick (at least 8 to 10 mm, for example between 10 and 30 or between 10 and 20 mm), so that we can engrave the desired patterns on the outer face to a certain thickness, to maximize the surface area of ​​exchange of the sole with the outside, while maintaining the continuity of the sole of course.

[0036] Figure 6 represents the outer face of the sole 7' according to Figure 5, with three-dimensional patterns in the form of studs, which are uniformly distributed over the entire outer surface. Alternatively, non-homogeneous pattern distributions may be provided, with higher concentrations of patterns in certain areas of the sole. The patterns may be always the same or vary in their shape or size across the surface of the sole.

[0037] Figures 7a and 7b respectively represent the outer metal layer 4 and the inner metal layer 3 of the laminated bus bar 2. In the stacking described in [Fig. 4], Only the superimposed portions of the two layers were shown. But, as is known, they present - areas, notably delimited by the dotted lines 4a shown in [Fig.7b], where the outer layer 4 completely covers the inner layer 3, - and areas of the inner layer 3 that "extend" from the outer layer 4, in particular a substantially square or rectangular area delimited by the dotted lines 3a shown in [Fig.7b], to provide tracks where components and connectors can be fixed / connected to this inner layer. The outer layer 4 is provided with a protective varnish (not shown), in a known manner, except in specific areas to provide tracks where components and connectors can be fixed / connected.

[0038] Thus, as shown in [Fig.7a], the outer layer 4 is provided (preferably by soldering) with a DC+ direct current connector 18, at least one capacitor 20, an AC alternating current connector 16, and at least one power semiconductor 21.

[0039] And as shown in [Fig.7b], the inner layer 3 is provided (preferably also by soldering) with a DC-19 direct current connector.

[0040] Figure 8 details the structure of the current measuring sensor 8 and how it is integrated into the board 1: it comprises a U-shaped magnetic concentrator 9, i.e., having a bottom wall 91 and two opposing side walls 92 perpendicular to the bottom wall. This concentrator is inserted into the base 7 through two openings 10 made in the base 7 with appropriate dimensional adjustments so that the concentrator 9 can be held in position with its bottom wall 91 disposed against the outer face of the portion of the base 7 located between the two openings 10. Its side walls 92 extend from the side of the opposite, inner face of said portion of the base.In the concentrator 9, there is a stack of layers which successively includes a layer 11 of insulating dielectric material (in particular of the polymer type, in particular based on polyimide or epoxy, such as those marketed by the company ARLON), a layer 12 of material conducting the current to be measured (for example in copper), a printed circuit 13 (PCB in RF4) and the current measurement element 14 (for example a current measurement integrated circuit called IC)).

[0041] It can be seen that the side walls 92 of the concentrator 9 are higher than this stack of layers / components. This stack of layers and components 11, 12, 13, 14 is therefore located on one of the faces, called the inner face, of the portion of the base 7 which is situated between the two openings 10 through which the concentrator 9 was inserted. The layers are bonded to one another by known techniques, in particular by gluing. Thus, the printed circuit board layer 13 is preferably so lidarized to layer 12 of conductive material and to layer 14 of current measuring element by bonding (bonding layers not shown).

[0042] And to secure the whole (stacking on portion of base 7) to the concentrator 9, a layer of glue 23 is also used for example. This glue is therefore located between the inner face of the bottom wall 91 of the concentrator 9 and the outer face of the portion of base (that is to say the face opposite to the inner face on which the stacking has been deposited).

[0043] It is understood that the power board according to the invention can include a variable number of components depending on the needs / specifications (ceramic capacitors, power semiconductors, voltage or current measurement components).

[0044] It can be seen that this board perfectly meets the increasingly demanding integration requirements in the field of power electronics, regardless of the electrical system involved. In particular, it can be used to great advantage in the field of electrified transport.

Claims

Demands

1. Electronic power card (1) comprising - a capacitive laminated bus bar (2) in the form of a first stack of two layers of metal, in particular copper, namely an inner metal layer (3) and an outer metal layer (4) separated from each other by a first layer (5) of electrically insulating material, - a layer (6) of thermal interface material disposed between said first stack and a metal base (7), - an integrated current sensor (8) comprising a magnetic flux concentrator (9) which is inserted into openings (10) made in the metal base (7), said magnetic flux concentrator (9) containing a second stack of layers comprising a second layer (11) of electrically insulating material, a layer (12) of material conductive with respect to the current to be measured, a printed circuit board (13) referred to as a PCB, and a current measurement component (14).

2. Card (1) according to the preceding claim, characterized in that it is a card of the type of isolated metal substrate said to be SMI, in particular multilayer, in particular double-layer and single-sided.

3. Card (1) according to any one of the preceding claims, characterized in that the magnetic flux concentrator (9) has a bottom wall (91), in particular of square or parallelepiped shape, and side walls (92), two of said side walls, in particular opposite walls, being inserted into two openings made (15) in the metal base (7).

4. Card (1) according to the preceding claim, characterized in that the second stack is attached to the inner face of the portion of the base arranged between the two openings (15), and in that the opposite face of said portion of the base is attached to the bottom wall (91) of the magnetic flux concentrator (9), in particular by a layer of glue (23).

5. A card (1) according to any one of the preceding claims, characterized in that the inner metallic layer (3) and / or the outer metallic layer (4) extend relative to each other so as to provide at least one accessible area on the outer surface of each of the outer (4) and inner (3) layers, in particular to constitute tracks for fixing components, in particular by soldering, of components, including at least one selected from AC connectors (16), DC connectors (18,19), capacitors (20), power semiconductors (21), DC or AC voltage measurement components (22).

6. Card (1) according to any one of the preceding claims, characterized in that a first part of the outer metal layer (4) of the first stack is provided with a protective material coating of the varnish type, and in that other parts of said outer metal layer (4) are uncoated and constitute tracks for fixing, in particular by soldering, components, in particular at least one selected from AC or DC current connectors (16, 18, 19), capacitors (20), power semiconductors (21), phase voltage measurement components (22).

7. Card (1) according to any one of the preceding claims, characterized in that at least one capacitor (20), in particular of ceramic type, and / or at least one DC- and DC+ electrical connector (18,19) is fixed, in particular by soldering, respectively by their positive terminal on the outer metal layer (4) and by their negative terminal on the inner metal layer (3) of the first stack.

8. Card (1) according to any one of the preceding claims, characterized in that it comprises at least one AC alternating current connector (16,17) and / or at least one fixed power semiconductor (21) fixed to the outer metal layer (4) or to the inner metal layer (3), and in that the outer metal layer (4) and inner metal layer (3) are equipped with vias (23) in line with the location of said AC alternating current connector(s) (16) and / or said power semiconductor(s) (21).

9. Card (1) according to any one of the preceding claims, characterized in that it comprises at least one DC or AC voltage measurement component (22), fixed, in particular by welding, to the outer metal layer (4) or to the inner metal layer (3) of the first stack.

10. A card (1) according to any one of the preceding claims, characterized in that the card comprises components capable of emitting heat during operation, fixed to the internal (3) or external (4) metallic layer, in particular at least one power semiconductor (21) and / or at least one connector, in particular for alternating current AC (16,17), and in that the external (4) and internal (3) metallic layers are equipped with vias (23') in the vicinity of said components.

11. Card (1) according to any one of the preceding claims, characterized in that the metal sole (7) is thermally connected to a heat-dissipating component.

12. Card (1) according to any one of the preceding claims, characterized in that the face of the metal base (7') which is opposite to that supporting the second layer of electrical insulating material (6) has three-dimensional patterns, in particular fins.

13. Card (1) according to the preceding claim, characterized in that the metal base (7') has a thickness of at least 5 mm, in particular of at least 8 or 10 mm, in particular between 10 and 30 mm.

14. Card (1) according to any one of the preceding claims, characterized in that the face of the metal base (7) which is opposite to that supporting the second layer of electrical insulating material (6) is provided, in particular by brazing or additive manufacturing, with a layer, in particular continuous or discontinuous, of metallic material which has three-dimensional surface patterns, of the fin type.

15. Card (1) according to any one of the preceding claims, characterized in that said card comprises power semiconductors (21), and in that it forms a drive inverter for an electrical machine, said inverter comprises a plurality of switching arms, each switching arm comprising power semiconductors (21).

16. Use of the card according to any one of the preceding claims to control the power supply of an electric motor.

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