Multi-stage sealed power electronic module

Abstract

The invention relates to a power electronics module (1) comprising: a substrate (10); -a first power electronic component (11a), which is arranged on the first face (10a) of the substrate (10); -a first cover (15a) defining, together with the substrate, a first cavity (17a) in which the first electronic power component (11a) is housed; -a second power electronic component (11b), which is arranged on the second face (10b) of the substrate (10); and-a second cover (15b) defining, together with the substrate, a second cavity (17b) in which the second electronic power component (11b) is housed; -a first annular seal (16a), which seals the first cavity (17a); -a second annular seal (16b), which seals the second cavity (17b); wherein the first annular seal (16a) and the second annular seal (16b) are formed from a sintered material, and wherein the first cavity (17a) and the second cavity (17b) enclose a gas or a gas mixture.

Description

Technical Field

[0001] The technical field of the present invention is the field of electronic power modules.

[0002] The invention more particularly relates to an electronic power module comprising a plurality of electronic power components distributed over a plurality of levels or stages. Background Art

[0003] Electronic power modules can realize basic functions such as switching, rectification, and voltage division.

[0004] So-called "2D" or "single-stage" power modules typically consist of one or more electronic power components soldered to a ceramic substrate equipped with metal tracks. The ceramic substrate is attached to a copper baseplate, which serves as a mechanical support and transfers heat generated by the components to a cooling device (usually a heat sink). The electrical connections between the components and the metal tracks of the substrate within the power module are partially provided by so-called bond wires. These components are enclosed in a housing filled with an encapsulation material.

[0005] The purpose of the encapsulation material is to ensure the dielectric strength of the power module and protect the components from external aggressors (moisture, contamination, etc.). In addition, the encapsulation material strengthens the electrical insulation between the conductors and improves the resistance to partial discharges, especially due to defects in the metallization of the ceramic substrate.

[0006] Electronic power components can be transistors, thyristors, and diodes. These components are formed from semiconductor materials. Wide-bandgap (or wide-gap) semiconductor materials, such as gallium nitride (GaN), gallium arsenide (GaAs), silicon carbide (SiC), and diamond, are increasingly replacing silicon due to their improved performance in terms of current density, operating frequency, and withstand voltage.

[0007] There are also so-called "3D" or "multi-level" electronic power modules, which include multiple electronic components distributed in different layers (also called "levels"). These electronic components are usually arranged on both sides of the substrate or between multiple stacked substrates.

[0008] The operation of electronic power modules (single-stage or multi-stage) generates temperature cycles that can be relatively severe. These temperature cycles generate significant mechanical stresses in one or more substrates and at the interfaces between the electronic components and the one or more substrates. These mechanical stresses induce a variety of failure modes in electronic power modules.

[0009] WO2019 / 101634A1 describes a multi-stage electronic power module designed to reduce the risk of failure. The module comprises metal supports and electronic power components disposed on or between the metal supports. The metal supports are assembled together to give the module a generally tubular shape with a circular cross-section. The supports have a T-shaped, F-shaped, or rectangular cross-section.

[0010] The supply current flows into and out of the electronic components through the metal support, which is able to effectively dissipate heat by conduction, convection and radiation simultaneously. The metal support provides a substrate without ceramic layers that may become embrittled due to thermal cycling.

[0011] The electronic power module also includes a sealed tubular cover made of plastic. This cover is attached to a portion of the metal support. The metal support and cover together define an internal channel through which a cooling fluid (e.g., gas or heat transfer liquid) circulates. The cooling fluid circulates within the internal channel, enabling the module to be cooled. The cooling fluid also ensures electrical insulation of the module.

[0012] However, due to the coolant circulation, the electronic power module described in document WO 2019 / 101634 A1 is difficult to integrate into an electromechanical actuator (such as an electric motor). Summary of the Invention

[0013] Therefore, there is a need for a multi-stage electronic power module that has good electrical insulation performance and is easy to integrate.

[0014] According to one aspect of the present invention, this need is met by providing an electronic power module comprising:

[0015] a substrate having a first side and a second side opposite to the first side;

[0016] a first electronic power component, the first electronic power component being arranged on the first side of the substrate;

[0017] a first cover, the first cover being disposed on the first side of the substrate and defining a first cavity together with the substrate,

[0018] A first electronic power component is accommodated in the first cavity;

[0019] a second electronic power component, the second electronic power component being arranged on the second side of the substrate;

[0020] a second cover, the second cover being disposed on the second surface of the substrate and defining a second cavity together with the substrate,

[0021] A second electronic power component is accommodated in the second cavity.

[0022] a first annular seal is provided between the substrate and the first cover, the first annular seal sealingly closing the first cavity; and

[0023] A second annular seal is provided between the substrate and the second cover, the second annular seal sealingly closing the second cavity.

[0024] The first annular seal and the second annular seal are formed of a sintered material, preferably a silver-based material, and the first cavity and the second cavity enclose a gas or a gas mixture.

[0025] The gas (or gas mixture) contained within the first and second sealed cavities provides a high degree of electrical insulation between the internal components of the electronic power module. Consequently, the power module is free of encapsulation materials (typically polymeric materials), which in prior art 2D modules tend to degrade during partial discharges (particularly in the so-called triple-point region between the ceramic substrate, the current-carrying metal tracks, and the encapsulation material).

[0026] Since no fluid circulation is required, integration of electronic power modules, such as in electromechanical actuators, is further facilitated. Instead, the electrically insulating gas is enclosed. Furthermore, sintering is a technique for sealing the cover to the substrate and enclosing the cavity, making it easy to form an annular seal.

[0027] In a first embodiment of the electronic power module, the first cover comprises:

[0028] - a first substrate formed from a first electrically insulating ceramic material; and

[0029] at least one first conductive element passing through the first substrate and electrically connected to the first electronic power component;

[0030] And the second covering member comprises:

[0031] - a second substrate formed from a second electrically insulating ceramic material; and

[0032] At least one second conductive element passing through the second substrate and electrically connected to the second electronic power component.

[0033] According to a development of the first embodiment, the first substrate and the second substrate are substrates made of aluminum nitride.

[0034] In a second embodiment, the first cover and the second cover each include a metal layer and an electrically insulating layer provided on an outer surface of the metal layer.

[0035] The electronic power module may further include:

[0036] - a third electronic power component, the third electronic power component being arranged on the first side of the substrate and being accommodated in the first cavity

[0037] in; and

[0038] a fourth electronic power component, which is arranged on the second side of the substrate and accommodated in the second cavity.

[0039] For example, the first electronic power component is connected in parallel with the third electronic power component, the second electronic power component is connected in parallel with the fourth electronic power component, the first electronic power component is a transistor, the second electronic power component is a transistor, the third electronic power component is a diode, and the fourth electronic power component is a diode.

[0040] In addition to the features discussed in the preceding paragraphs, the electronic power module according to an aspect of the present invention may have one or more of the following additional features, which may be considered individually or in any technically possible combination:

[0041] - the substrate is a metal substrate;

[0042] The first electronic power component comprises a first terminal electrically connected to the substrate and a conductive portion electrically connected to the first cover.

[0043] Second terminal;

[0044] The second electronic power component comprises a first terminal electrically connected to the substrate and a conductive portion electrically connected to the second cover.

[0045] Second terminal;

[0046] Each of the first electronic power component and the second electronic power component is electrically conductive via a conductive track and the conductive material formed

[0047] A seal is electrically connected to the substrate;

[0048] - the first electronic power component is electrically connected to the conductive portion of the first cover via conductive tracks and a conductive seal formed of the sintered material; and

[0049] The second electronic power component is electrically connected to the conductive portion of the second cover via conductive tracks and a conductive seal formed of the sintered material.

[0050] A second aspect of the invention relates to an electromechanical actuator comprising at least one electronic power module according to the first aspect of the invention.

[0051] The electromechanical actuator preferably comprises a three-phase motor and a three-phase motor drive and supply circuit comprising a plurality of electronic power modules according to the first aspect of the invention for generating phase currents for the three-phase motor.

[0052] Each electronic power module is advantageously arranged facing a winding head of the three-phase electric machine.

[0053] A third aspect of the present invention relates to a method for manufacturing an electronic power module, the method comprising the following steps:

[0054] - providing a substrate, a first cover and a second cover;

[0055] - attaching a first electronic power component to the first cover;

[0056] - depositing a sintered material onto the first cover to form a first bead around the first electronic power component;

[0057] - attaching a second electronic power component to the second cover;

[0058] - depositing the sintered material onto the second cover to form a second bead around the second electronic power component;

[0059] - transferring the first cover to the substrate by placing the first bead and the second bead of the sintered material in contact with the substrate

[0060] a first side of a substrate and transferring the second cover to an opposite second side of the substrate; and

[0061] - sintering the sintered material to form a first annular seal and a second annular seal, the first annular seal sealingly closing a first cavity defined by the first cover and the substrate, and the second annular seal sealingly closing a second cavity defined by the second cover and the substrate, the first cavity and the second cavity enclosing a gas or a gas mixture.

[0062] Preferably, the substrate is a substrate made of aluminum, and the method further comprises: before the step of transferring the cover, a step of forming silver-based conductive tracks on the first side and the second side of the substrate, the step of forming the silver-based conductive tracks comprising the following operations:

[0063] - depositing a paste comprising silver particles by screen printing;

[0064] - drying the slurry; and

[0065] - Annealing the paste at a temperature equal to or higher than 570°C. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Further features and advantages of the present invention will become apparent from the following description, which is given for illustrative purposes only and not for limiting purposes, with reference to the accompanying drawings, in which:

[0067] - Figure 1 is a schematic cross-sectional view of an electronic power module according to a first embodiment;

[0068] - Figure 2 is a schematic cross-sectional view of an electronic power module according to a second embodiment;

[0069] - Figure 3 It is a partial stereoscopic diagram of a three-phase motor integrated with multiple electronic power modules;

[0070] - Figures 4A to 4E schematically illustrates the steps in a method for manufacturing an electronic power module; and

[0071] - Figure 5 The aluminum-silver phase diagram is shown.

[0072] For increased clarity, the same or similar elements are denoted by the same reference numerals throughout the drawings. DETAILED DESCRIPTION

[0073] Figure 1 An electronic power module 1 according to a first embodiment is schematically shown. The electronic power module 1 may have the function of converting an AC voltage into a DC voltage (rectifier function), converting a DC voltage into an AC voltage (inverter function), modifying the RMS value of the AC voltage (dimmer function), modifying the average value of the DC voltage (chopper function), or modifying the frequency of the AC voltage (cycloconverter function) or dissipating current (active resistor function).

[0074] The power module 1 comprises a substrate 10 and at least two electronic power components: a first component 11 a arranged on a first face 10 a of the substrate 10 and a second component 11 b arranged on a second face 10 b of the substrate 10 opposite the first face 10 a .

[0075] Thus, the power module 1 comprises two component levels, a first level comprising (at least) a first component 11 a and a second level comprising (at least) a second component 11 b .

[0076] The substrate 10 is preferably a metal substrate. The substrate can be formed from a single metal layer (e.g., aluminum or copper) or from a plurality of stacked metal layers formed from different metals. For example, the substrate is a rectangular plate-shaped substrate. The thickness of the substrate is preferably between 0.2 mm and 2 mm. The substrate may have recesses, protrusions (preferably, a ratio of width to height of between 1 and 3) and additional thickness, in other words, the substrate may have a texture. Therefore, the surfaces 10a and 10b of the substrate are not necessarily flat, as Figure 1 Shown schematically. In addition, these faces can be rough and / or porous.

[0077] Advantageously, the substrate 10 forms a power conductor carrying one or more electrical outputs of the power module 1. The substrate is capable of conducting high currents (typically greater than 20 A).

[0078] One or more additional conductors 12 may be attached to the substrate 10 to facilitate connecting the power module 1 to one or more electrical devices (in the example below, an electric motor and a current sensor). Figure 1 The power module 1 comprises two additional conductors 12 attached to two opposite sides of the substrate 10. These additional conductors 12 then constitute output terminals of the power module 1. Each additional conductor 12 preferably extends perpendicularly to the substrate 10.

[0079] Thus, substrate 10 acts as an electrical bridge (or common point) between the two component levels. During operation of power module 1, the temperature at substrate 10 is substantially constant, as the substrate is made entirely of metal. Sudden temperature changes (called transients) are eliminated, which has the effect of reducing (thermal) noise on one or more electrical outputs of power module 1 and improving reliability from the perspective of thermomechanical stress.

[0080] Advantageously, substrate 10 is covered on each of its faces 10a and 10b with one or more conductive tracks 13 (called facings). These conductive tracks 13 are preferably made of a silver-based conductive material which has the advantage of being non-oxidizable.

[0081] The first component 11a and the second component 11b are each electrically connected to the substrate 10, preferably via one of a conductive track 13 and a conductive seal 14 formed of a sintered material.

[0082] The sintered material of the conductive seal 14 is advantageously a silver-based or copper-based material. In particular, the silver-based conductive seal 14 and the conductive tracks 13 based on the same metal form a high-performance electrical and mechanical connection, particularly in terms of electrical resistance and electrical and thermal conductivity. This type of connection is particularly suitable for the high operating temperatures typically found in electronic power modules.

[0083] Alternatively, the silver-based or copper-based conductive seal 14 is formed on an electroless nickel immersion gold ("ENIG") or electroless nickel palladium immersion gold ("ENEPIG") type conductive track or finish.

[0084] The power module 1 further includes:

[0085] a first cover 15 a provided on the first face 10 a of the substrate 10 ;

[0086] - a second cover 15b provided on the second face of the substrate 10;

[0087] a first annular seal 16a arranged between the substrate 10 and the first cover 15a; and

[0088] A second annular seal 16b is arranged between the substrate 10 and the second cover 15b.

[0089] The first cover 15 a defines, together with the substrate 10 , a first cavity 17 a in which the first component 11 a is accommodated, while the second cover 15 b defines, together with the substrate 10 , a second cavity 17 b in which the second component 11 b is accommodated.

[0090] Preferably, the first component 11a is electrically connected to the first cover 15a and the second component 11b is electrically connected to the second cover 15b. Advantageously, the components 11a and 11b are connected to the covers 15a and 15b in the same manner as they are connected to the substrate 10, via conductive tracks 13 (here provided on the inner faces of the covers 15a and 15b) and conductive seals 14.

[0091] The first annular seal 16a and the second annular seal 16b hermetically seal the first cavity 17a and the second cavity 17b, respectively. The first and second annular seals are made of a sintered material, preferably a silver-based sintered material. The sintered material is advantageously the same as that of the conductive seal 14. Using the same sintered material to form the conductive seal 14 and the annular seals 16a and 16b significantly simplifies the manufacture of the power module 1.

[0092] In order to reduce the risk of the covers 15 a and 15 b falling off, each annular seal 16 a , 16 b is advantageously arranged in contact with a conductive track 13 provided on the substrate 10 .

[0093] The substrate 10 extends beyond the annular seals 16a and 16b to enable electrical connection of the power module 1 (directly or via additional conductors 12).

[0094] The chambers 17a and 17b enclose a gas, preferably a neutral gas (e.g., argon, nitrogen, or helium). Alternatively, these chambers may contain a gas mixture, e.g., air. The pressure of the gas (or gas mixture) may be atmospheric pressure (when the chambers 17a and 17b are sealed) or a much lower pressure, typically less than 133.3×10 -3 Pa (i.e., 10 -3 Torr) to obtain a primary vacuum configuration. The gas pressure is advantageously 133.3×10 -6 Pa(10 -6 Torr) and 133.3x10 -7 Pa(10 -7 Torr), i.e., an auxiliary vacuum configuration, to avoid partial discharges that may occur in the main vacuum. Cavities 17a and 17b do not contain water vapor.

[0095] The gas contained in cavities 17a and 17b provides electrical insulation between the internal components of power module 1. Annular seals 16a and 16b, in particular, prevent moisture from entering cavities 17a and 17b (which could cause partial discharges). Preventing moisture from entering the cavities helps improve component reliability and electrical connections. Furthermore, the electrical insulation of electronic power module 1 does not rely on cooling and does not require circulating fluids, as is the case with prior art modules, which facilitates the integration of electronic power modules.

[0096] The annular seals 16a and 16b can achieve a case junction thermal resistance R of less than 0.3°C / W. JC These annular seals also enable a more compact module to be obtained compared to prior art annular seals with encapsulating (or coating) material.

[0097] Like substrate 10, covers 15a and 15b preferably have a substantially parallelepiped shape. Each of covers 15a and 15b preferably has a thickness between 0.2 mm and 2 mm. Therefore, unlike conventional power modules with right-angled metal supports, power module 1 has a smaller overall size.

[0098] The thickness of the covers 15a and 15b may be constant or substantially constant (with a thickness variation of less than 100 μm). Alternatively, one or both of the covers 15a and 15b may have a peripheral edge extending toward the substrate 10 to increase the volume of the first cavity 17a and / or the second cavity 17b (particularly depending on the thickness of the components contained therein).

[0099] Preferably, the covers 15a and 15b are made of the same material or materials and have the same dimensions, so that the power module 1 is symmetrical overall with respect to the substrate 10. This symmetry reduces mechanical stress, especially bending stress, within the power module 1 (this is achieved by positioning the neutral plane of the module in the substrate 10).

[0100] The first component 11a and the second component 11b are preferably active components, for example transistors, diodes, or thyristors. The first and second components include at least two terminals or electrodes (not shown). Advantageously, the first terminal of the first component 11a and the first terminal of the second component 11b are electrically connected to the substrate 10, the second terminal of the first component 11a is electrically connected to the conductive portion of the first cover 15a, and the second terminal of the second component 11b is electrically connected to the conductive portion of the second cover 15b. Therefore, the function of these covers is that they are used to transmit electrical signals between the exterior and interior of the power module 1.

[0101] The electrical connections of the electronic power module 1 are advantageously made on the outer surfaces of the covers 15a and 15b and on at least one end of the central substrate 10, which further facilitates the integration of the electronic power module, especially in electrical devices where available space is limited. The outer surfaces of the covers 15a and 15b are preferably planar or substantially planar (with a thickness variation of less than 100 μm).

[0102] In this first embodiment, the covers 15a and 15b each comprise a substrate 151 of an electrically insulating ceramic material and one or more conductive elements 152 extending through the substrate 151. The conductive elements 152 (also referred to as inserts) are hermetic, i.e., they prevent any exchange of fluids (e.g., water vapor) between the exterior and interior of the power module 1. These conductive elements serve to conduct electrical current between the exterior and interior of the module, to or from the electronic power components.

[0103] Thus, at least one conductive element 152 of the first cover 15a is electrically connected to the second terminal of the first component 11a, and at least one conductive element 152 of the second cover 15b is electrically connected to the second terminal of the second component 11b. Advantageously, the components 11a and 11b are connected to the conductive elements 152 of the covers 15a and 15b in the same manner as they are connected to the substrate 10, via the conductive tracks 13 (here provided on the inner surfaces of the covers 15a and 15b) and the conductive seal 14.

[0104] The conductive element 152 may also serve to dissipate heat generated by the components 11a and 11b (both electrically conductive and thermally conductive elements).

[0105] The conductive elements 152 may be, in particular, vias or heat sinks. These conductive elements are preferably formed from one or more metals, for example selected from the group consisting of copper, aluminum, tungsten, gold, titanium, silver, palladium and alloys thereof.

[0106] The substrate 151 of the covers 15a and 15b is preferably formed from the same ceramic material, such as aluminum nitride (AlN), aluminum oxide (Al2O3), silicon carbide (SiC), aluminum silicon carbide (AlSiC), or silicon nitride (Si3N4). Aluminum nitride is particularly advantageous because it has high thermal conductivity, high electrical conductivity, and can be easily incorporated into the sealing insert. Compared to metal, the thermal expansion coefficient of aluminum nitride is also closer to that of the semiconductor material forming the substrate of components 11a and 11b. Therefore, covers 15a and 15b comprising aluminum nitride have the advantage of significantly reducing thermomechanical stresses within power module 1.

[0107] like Figure 1 As shown, the power module 1 may include more than two electronic power components, for example, two per stage, for a total of four.

[0108] Therefore, the power module 1 may include:

[0109] a third component 11 c , which is arranged on the first face 10 a of the substrate 10 and is housed in the first cavity 17 a ;

[0110] a fourth component 11 d , which is arranged on the second face 10 b of the substrate 10 and is housed in the second cavity 17 b .

[0111] Like the first and second components 11a and 11b, each of the third and fourth components 11c and 11d is connected to the substrate 10 and to at least one conductive element 152 of the covers 15a and 15b, preferably via conductive tracks 13 and conductive seals 14 made of sintered material.

[0112] The electronic power module 1 can be easily integrated into an electromechanical actuator. For example, the electromechanical actuator includes a three-phase motor and a power supply and control circuit for the three-phase motor. This circuit includes a plurality of power modules 1, preferably the same number of power modules 1 as the number of inductors or coils included in the three-phase motor. Each power module 1 powers the motor by generating one of the motor's phase currents.

[0113] Figure 3 A portion of a three-phase motor 40 is shown. The figure shows only three coils and the motor shaft has been intentionally omitted. The power modules 1 are advantageously arranged inside the motor 40, preferably opposite the winding heads 41 of the motor 40 (one module per coil).

[0114] In this application example, the power module 1 is a four-component configuration. Components 11a to 11d are connected together to form a bridge arm of the inverter installation. The first component 11a is a transistor (preferably a metal oxide semiconductor field effect transistor (MOSFET) or an insulated gate bipolar transistor (IGBT)), the second component 11b is a transistor (preferably a MOSFET or IGBT), the third component 11c is a diode, and the fourth component 11d is a diode.

[0115] Reference again Figure 1 The first component 11a (transistor) and the third component 11c (diode) are connected in parallel between the positive supply voltage V+ carried by the conductive element 152 of the first cover 15a (for example, a heat sink of copper-tungsten alloy) and the first electrical output V of the power module 1 carried by the substrate 10. S The second component 11b (transistor) and the fourth component 11d (diode) are connected in parallel between the negative power supply voltage V- carried by the conductive element 152 of the second cover 15b (for example, a heat sink of copper-tungsten alloy) and the electrical output V of the power module 1. S between.

[0116] The first control signal G1 is routed to the gate of the transistor 11 a via a through-hole 152 (e.g., tungsten) through the first cover 15 a, a conductive seal 14 of sintered material, and a conductive track 13 provided on the first face 10 a of the substrate 10 but electrically insulated therefrom by a first dielectric layer 18.

[0117] Similarly, the second control signal G2 is routed to the gate of transistor 11b via a through hole 152 (e.g., tungsten) passing through the second cover 15b and a conductive track 13 arranged on the inner face of the second cover 15b (possibly covered with a second dielectric layer 18 to enhance electrical insulation).

[0118] The power module 1 comprises a second electrical output V 霍尔 The second electrical output is carried by substrate 10 and is connected to a current sensor (e.g., a Hall effect current sensor). This current sensor measures the phase current delivered to the motor. Thus, in this example, power module 1 is a bridge arm of an inverter incorporating a current measurement device.

[0119] Figure 2An electronic power module 1 according to a second embodiment is shown. This second embodiment differs from the first embodiment primarily in the construction of the covers 15 and 15b. Here, the covers 15 and 15b each comprise a metal layer 153 instead of a ceramic substrate. Advantageously, these covers also include an electrically insulating layer 154 disposed on the outer surface of the metal layer 153. The insulating layer 154 limits partial discharges between the metal layers 153 of the covers 15a and 15b and adjacent conductive components (e.g., conductive components of an electric machine in which the power module 1 is integrated). For example, these insulating layers are made of AlN and have a thickness of 100 μm.

[0120] The metal layer 153 of the first cover 15a and the metal layer 153 of the second cover 15b carry the positive supply voltage V+ and the negative supply voltage V-, respectively. An insulating layer 154 completely covers the exterior of the metal layer 153, except for the areas where electrical contact is required. The control signal G1 of transistor 11a is routed via a conductive track 13 provided on substrate 10 and separated from substrate 10 by a first dielectric layer 18. The control signal G2 of transistor 11b is routed via a conductive track 13 arranged on the inner surface of the second cover 15b and separated from the metal layer 153 of the same cover by a second dielectric layer 18.

[0121] In order to prevent short circuits between the (metal) substrate 10 and the covers 15 a and 15 b , the annular seals 16 a and 16 b are separated from the substrate 10 and the covers 15 a and 15 b by a further dielectric layer 18 .

[0122] Thus, metal layer 153, substrate 10, and annular seals 16a and 16b form a structure similar to a Faraday cage, which protects electronic components from electromagnetic fields and electrostatic discharge.

[0123] The power module 1 is not limited to combining Figure 1 and Figure 2 In particular, each level of components may comprise a plurality (two or more) of electronic power components (preferably of the transistor, diode or thyristor type) connected in parallel or in series.

[0124] Figures 4A to 4E Steps S1 to S5 of a method for producing a power module 1 are schematically shown.

[0125] like Figure 4A As shown, the first step S1 of the manufacturing method includes providing a substrate 10 and covers 15a and 15b for transferring electronic power components (steps S2 and S3; Figures 4B to 4C ) and assembling these electronic power components by sintering (steps S4 and S5; Figure 4D and Figure 4E ) to prepare.

[0126] The manufacturing method may further include forming one or more conductive tracks 13 on each of the faces 10a and 10b of the substrate 10 and depositing one or more dielectric layers 18 on either or both of the faces 10a and 10b.

[0127] In the power module 1 according to the first embodiment (see Figure 1 and Figure 4A ), providing the first cover 15a or the second cover 15b may include the following operations:

[0128] - providing a ceramic substrate 151; and

[0129] - Forming one or more conductive elements 152 (or inserts) in the ceramic substrate 151 , for example by creating a cavity and filling the cavity with metal.

[0130] The manufacturing method may then comprise forming one or more conductive tracks 13 on the inner face of the cover 15a, 15b and depositing one or more dielectric layers 18 onto this same inner face.

[0131] The conductive tracks 13 are for example made by screen printing silver paste (for example, made by Dupont TM ) company under the designation AS300), drying the silver paste, and annealing the silver paste. Dielectric layer 18 can also be formed by using a dielectric paste, such as the dielectric paste sold by DuPont™ under the designation AS100.

[0132] Silver paste (sometimes also referred to as "ink") comprises silver particles dispersed in a matrix, which preferably comprises a metal oxide, such as aluminum oxide (Al2O3).

[0133] By default, the silver conductive tracks 13 are poorly held on the substrate 10 or the aluminum metal layer 153 (covers 15a and 15b) due to the presence of a native oxide (Al2O3) layer on the surface, which forms a barrier. To improve this, it is possible to dissolve this native oxide layer (and thus deoxidize the surface) before depositing the silver paste, for example by depositing zincate on the native oxide layer.

[0134] In a preferred mode of carrying out the fabrication method, annealing of the silver paste is performed at a temperature of 570° C. or above (instead of the manufacturer's recommended temperature of 450° C. for AS300 paste). Figure 5The phase diagram shows that annealing at 567°C and above forms an aluminum-silver eutectic alloy, rather than an intermetallic alloy (between 425°C and 567°C). However, it is estimated that the eutectic alloy is four times stronger than the intermetallic alloy and is more stable over time, at least in terms of tear strength. Moreover, annealing at these temperatures destroys the aluminum oxide barrier layer. Therefore, a prior deoxidation step is not necessary. The annealing time is preferably between 30 and 300 minutes.

[0135] Figure 4B Step S2 includes:

[0136] - attaching the first component 11 a to the inner surface of the first cover 15 a , more specifically to the conductive track 13 ;

[0137] - depositing a first sintered material onto the first cover 15a so as to form a first annular bead (or

[0138] Article 20a; and

[0139] - Drying the first sintered material, for example, at 150° C. for 40 minutes.

[0140] Although shown in the same figure, these operations are performed sequentially (the first component 11a may be attached before or after the first annular bead 20a is formed).

[0141] like Figure 4B As shown, a first annular bead 20a may be formed on a peripheral edge of the first cover 15a.

[0142] Attaching the first component 11a preferably includes forming a first layer 21a of a second sintered material on the first cover 15a, depositing the first component 11a onto the first layer 21a, and drying the second sintered material of the first layer 21a. Thus, the first component 11a is connected to the first cover 15a by sealing with the sintered material rather than by welding or brazing.

[0143] Step S2 may further include forming a second layer 22a of a second sintered material on the first component 11a to subsequently connect the first component 11a to the substrate 10 by sealing with the sintered material. Alternatively, the second layer 22a of the second sintered material is deposited onto the substrate 10.

[0144] The sintering material is a paste comprising metal particles (preferably silver) and one or more organic elements whose purpose is to give the paste adhesiveness and enable it to be applied by screen printing (binder) and / or to separate the particles and to prevent them from sintering before their intended time (dispersant). These organic elements are largely removed during the drying operation. The sintering paste may also include additives to accelerate the (subsequent) sintering of the particles.

[0145] Possible other electronic power components belonging to the same level of components, such as the third component 11 c , are preferably attached to the first cover 15 a in the same way as the first component 11 a .

[0146] same, Figure 4C Step S3 includes attaching the second component 11b to the inner face of the second cover 15b (more specifically, to the conductive track 13), depositing a first sintered material on the second cover 15b to form a second annular bead 20b around the second component 11b (or its location), and drying the first sintered material. The second annular bead 20b is formed, for example, on the peripheral edge of the second cover 15b.

[0147] Attaching the second component 11b preferably includes forming a third layer 21b of a second sintered material on the second cover 15b, depositing the second component 11b onto the third layer 21b, and drying the second sintered material of the third layer 21b.

[0148] Step S3 may further comprise forming a fourth layer 22b of a second sintered material on the second component 11b to subsequently connect the second component 11b to the substrate 10 by sealing with the sintered material. Alternatively, the fourth layer 22b of the second sintered material is deposited onto the substrate 10.

[0149] Possible other electronic power components belonging to the same level of components, such as the fourth component 11d , are preferably attached to the second cover 15b in the same way as the second component 11a .

[0150] Prior to depositing the sintered material, an Ar / H plasma treatment may be performed to remove any organic contaminants from the substrate, deoxidize the substrate, texture the substrate to a desired arithmetic mean roughness (Ra) between 0.2 and 0.8, and activate the surface prior to sintering. Additionally, drying the first sintered material and drying the second sintered material may be performed simultaneously.

[0151] Advantageously, the second sintered material used to attach the component to the cover 15a, 15b or substrate 10 is the same as the first sintered material used to form the annular beads 20a and 20b. This manufacturing method is therefore particularly easy to implement. The first annular bead 20a is advantageously deposited simultaneously with the first layer 21a or the second layer 22a. Advantageously, the second annular bead 20b is deposited simultaneously with the third layer 22a or the fourth layer 22b.

[0152] exist Figure 4D In step S4 shown, the first cover 15a is transferred to the first side 10a of the substrate 10, and the second cover 15b is transferred to the second side 10b of the substrate 10. The annular beads 20a and 20b are placed in contact with the substrate 10. For example, the transfer is performed using a "flip chip" type device commonly used in the microelectronics industry.

[0153] Preferably, the covers 15a and 15b are positioned relative to the substrate 10 so that the annular beads 20a and 20b face each other. This arrangement tends to reduce mechanical stresses.

[0154] at last, Figure 4E Step S5 in the embodiment of the present invention comprises sintering the first sintered material to transform the annular beads 20a and 20b into the seals 16a and 16b. Simultaneously, the second sintered material is sintered to form the conductive seal 14 between the components 11a to 11d and the substrate 10, and between the components 11a to 11d and the cover members 15a and 15b. The sintering can be done in a partial vacuum or in air (where the silver conductive tracks do not oxidize). The air can serve to eliminate (calcine) any remaining organic elements in the sintering slurry or slurries.

[0155] Sintering can be performed under pressure using a hot press according to a predetermined temperature and pressure profile, for example, according to the method described in International Application WO 2022 / 200749 A2. The hot press preferably comprises a heating arm and a support on which the substrate-component-cover assembly is arranged. Preferably, the sintering step S5 comprises the following stages:

[0156] a first phase (the so-called creep phase), during which the support and the arm reach a creep temperature between 165° C. and 175° C. and remain at this temperature for a period between 30 and 60 seconds, and during which, after a rise of about 40 s,

[0157] applying a constant pressure between 0.5 MPa and 1 MPa for a period between 15 s and 30 s;

[0158] a second phase (the so-called sintering phase), lasting a period of between 60 and 400 s, during which the temperature of the arms and the support is kept constant between 205 and 255° C. and the pressure applied is between 10 and 30 MPa;

[0159] - a third phase (the so-called consolidation and cooling phase), during which the temperature is lowered (for example, returned to room temperature) while maintaining the pressure applied during the second phase.

[0160] For example, the duration of the third phase is between 1 minute and 10 minutes.

[0161] Alternatively, sintering is performed without pressure, for example according to the method described in WO 2017 / 046266 A1.

[0162] Combine Figures 4A to 4E The manufacturing method described is easy to implement because steps S2 and S3 are so-called "2D" assembly steps that can be performed on the panel in parallel with each other (in other words, simultaneously), unlike step S4 of transferring the covers 15a and 15b and step S5 of sintering ("3D" assembly steps). Similarly, the steps of forming the conductive tracks 13 and the dielectric layer 18 on the substrate 10 and the covers 15a and 15b can be performed in parallel.

Claims

1. An electronic power module (1), comprising: - a substrate (10) having a first face (10a) and a second face (10b) opposite to the first face; a first electronic power component (11a) arranged on the first face (10a) of the substrate (10); a first cover (15a) arranged on the first face (10a) of the substrate (10) and delimiting, together with the substrate, a first cavity (17a) in which the first electronic power component (11a) is accommodated; - a second electronic power component (11b), which is arranged on the second face (10b) of the substrate (10); as well as a second cover (15b) arranged on the second face (10b) of the substrate (10) and delimiting, together with the substrate, a second cavity (17b) in which the second electronic power component (11b) is accommodated; Characterized in that, the electronic power module further comprises: a first annular seal (16a) disposed between the substrate (10) and the first cover (15a), the first annular seal sealingly closing the first cavity (17a); a second annular seal (16b) disposed between the substrate (10) and the second cover (15b), the second annular seal sealingly closing the second cavity (17b); The first and second annular seals (16a, 16b) are formed of a sintered material, preferably a silver-based material, and the first and second cavities (17a, 17b) enclose a gas or a gas mixture.

2. The module (1) according to claim 1, wherein - the substrate (10) is a substrate made of metal; - the first electronic power component (11a) comprises a first terminal electrically connected to the substrate (10) and a second terminal electrically connected to the conductive portion (152, 153) of the first cover (15a); The second electronic power component (11b) comprises a first terminal electrically connected to the substrate (10) and a second terminal electrically connected to the conductive portion (152, 153) of the second cover (15b).

3. The module (1) according to claim 2, wherein Each of the first and second electronic power components (11a, 11b) is electrically connected to the substrate (10) via a conductive track (13) and a conductive seal (14) formed of the sintered material.

4. Module (1) according to one of claims 2 and 3, wherein: - the first electronic power component (11a) is electrically connected to the conductive portion (152, 153) of the first cover (15a) via a conductive track (13) and a conductive seal (14) formed of the sintered material; The second electronic power component (11b) is electrically connected to the conductive portion (152, 153) of the second cover (15b) via a conductive track (13) and a conductive seal (14) formed of the sintered material.

5. The module (1) according to any one of claims 1 to 4, wherein The first covering member (15a) comprises: - a first substrate (151) formed of a first electrically insulating ceramic material; and at least one first conductive element (152), which passes through the first substrate (151) and is electrically connected to the first electronic power component (11); Wherein, the second covering member (15b) comprises: - a second substrate (151) formed of a second electrically insulating ceramic material; and - at least one second conductive element (152), which passes through the second substrate (151) and is electrically connected to the second electronic power component (11b).

6. The module (1) according to claim 5, wherein The first substrate and the second substrate (151) are substrates made of aluminum nitride.

7. The module (1) according to any one of claims 1 to 4, wherein The first cover and the second cover (15a, 15b) each include a metal layer (153) and an electrical insulation layer (154) provided on an outer surface of the metal layer (153).

8. An electromechanical actuator comprising at least one electronic power module (1) according to any one of claims 1 to 7.

9. An actuator according to claim 8, comprising a three-phase motor (40) and a three-phase motor drive and power supply circuit, wherein the three-phase motor drive and power supply circuit comprises a plurality of electronic power modules (1) according to any one of claims 1 to 7, and the electronic power modules are used to generate phase currents for the three-phase motor (40).

10. The actuator according to claim 9, wherein Each electronic power module (1) is arranged facing the winding end (41) of the three-phase motor (40).

11. A method for manufacturing an electronic module (1), comprising the following steps: - providing (S1) a substrate (10), a first cover (15a) and a second cover (15b); - attaching (S2) a first electronic power component (11a) to the first cover (15a); - depositing (S2) a sintered material onto the first cover (15a) so as to form a first bead (20a) around the first electronic power component (11a); - attaching (S3) a second electronic power component (11b) to the second cover (15b); - depositing (S3) the sintered material onto the second cover (15b) so as to form a second bead (20b) around the second electronic power component (11b); - transferring (S4) the first cover (15a) to a first face (10a) of the substrate (10) and transferring (S4) the second cover (15b) to an opposite second face (10b) of the substrate by placing the first and second beads (20a, 20b) of the sintered material in contact with the substrate; and - sintering (S5) the sintered material to form a first annular seal and a second annular seal (16a, 16b), the first annular seal (16a) sealingly closing a first cavity (17a) defined by the first cover (15a) and the substrate (10), and the second annular seal (16b) sealingly closing a second cavity (17b) defined by the second cover (15b) and the substrate (10), the first cavity and the second cavity enclosing a gas or a gas mixture.

12. The method according to claim 11, wherein The substrate (10) is a substrate made of aluminum, and the method further comprises: before the step (S4) of transferring the covering members (15a, 15b), a step of forming silver-based conductive tracks (13) on the first surface (10a) and the second surface (10b) of the substrate (10), the step of forming the silver-based conductive tracks comprising the following operations: - depositing a paste comprising silver particles by screen printing; - drying the slurry; and - Annealing the paste at a temperature equal to or higher than 570°C.

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