Power module with overmold and system comprising such power module

Abstract

The invention relates to a power module comprising: • a first and a second electrical connection portion, each electrical connection portion having a main plate; • a transistor, the upper surface of the transistor defining a reference plane; and • an electrically insulating overmold, the upper surface of the electrically insulating overmold having a cavity; said cavity having a flat bottom, a strip or wire forming a first bridge, both ends of which lie flat on the upper surface of the transistor, the orthogonal projection of the highest point of the first bridge on the reference plane being comprised in the orthogonal projection on the reference plane of the flat bottom of the cavity, and wherein the difference between the distance D5 of the highest point of the first bridge with respect to the reference plane and the thickness of the strip or wire is greater than or equal to the difference between the distance D3 between a plane parallel to the reference plane passing through the highest point of the electrically insulating overmold and the reference plane and the distance D2 between a plane parallel to the reference plane passing through the highest point of the electrically insulating overmold and a plane parallel to the reference plane passing through the lowest point of the cavity.

Description

Technical Field

[0001] The present invention relates to a power module having an overmolded component, an electrical system, and a voltage converter including such a power module. Background Technology

[0002] A power module is an electronic module that typically contains semiconductor chips (such as transistors, called power transistors) designed to generate energy conversion circuits, such as switching units, inverters, or even rectifier bridges.

[0003] Power modules known in the prior art include:

[0004] - Preferably, the first and second electrical connection portions are made of metal, each electrical connection portion having a main board that extends along the same main plane and is thus substantially coplanar;

[0005] - A transistor mounted on the upper surface of the motherboard of the first electrical connection portion, the upper surface of which defines a reference plane, the transistor being electrically connected to the upper surface of the motherboard of the second electrical connection portion via at least one strip or via at least one wire; and

[0006] - For example, an electrically insulating overmolded part made of resin covers at least a portion of the upper surface of the motherboard of the transistor and the first and second electrical connection portions, the upper surface of the electrically insulating overmolded part having a cavity at least partially located above the strip or wire.

[0007] However, in cases of transistor overheating, such as short circuits, heat can diffuse into the electrical insulators, posing a fire hazard that could endanger surrounding components. Summary of the Invention

[0008] The purpose of this invention is to at least partially overcome the above-mentioned problems.

[0009] Therefore, according to a first aspect of the present invention, a power module is provided, comprising:

[0010] - Preferably, the first and second electrical connection portions are made of metal, each electrical connection portion having a main board that extends along the same main plane and is thus substantially coplanar;

[0011] - A transistor mounted on the upper surface of the motherboard of the first electrical connection portion, the upper surface of which defines a reference plane, the transistor being electrically connected to the upper surface of the motherboard of the second electrical connection portion via at least one strip or via at least one wire; and

[0012] - For example, an electrically insulating overmolded part made of resin covers at least a portion of the upper surface of the motherboard of the transistor and the first and second electrical connection portions, the upper surface of the electrically insulating overmolded part having a cavity at least partially located above the strip or wire.

[0013] The power module is characterized in that the cavity has a flat bottom, a strip or wire forms a first bridge with its two ends flatly located on the upper surface of the transistor, the orthogonal projection of the highest point of the first bridge onto a reference plane is included in the orthogonal projection of the flat bottom of the cavity onto the reference plane, and wherein the difference between the distance D5 of the highest point of the first bridge relative to the reference plane and the thickness of the strip or wire is greater than or equal to the difference between the distance D3 between the plane parallel to the reference plane passing through the highest point of the electrically insulating overlay and the distance D2 between the plane parallel to the reference plane passing through the highest point of the electrically insulating overlay and the plane parallel to the reference plane passing through the lowest point of the cavity.

[0014] The fact that the cavity is at least partially located above the strip or wire in geometry means that the intersection between the orthogonal projection of the strip or wire onto the principal plane and the orthogonal projection of the cavity onto the same principal plane is not empty.

[0015] With the help of this technical feature, the thickness of the electrically insulating overmolded part can be adjusted according to the arrangement of the strips or wires, so that the thickness is smaller or even zero above the strips or wires.

[0016] Furthermore, the relationship between the distances D5, D2, D3 and the thickness of the strip or wire ensures that the upper end of the first bridge formed by the strip or wire is located in the cavity, so that the electrically insulating overmolded part is subjected to little or no holding force on the upper end.

[0017] In this way, the holding force of the electrically insulating overmolded part applied to the strip or wire, especially to the upper end, is reduced, making the strip or wire more prone to breakage when heated.

[0018] Therefore, the strips or wires in the power module according to the invention break at a lower temperature than those in the power module according to the prior art. Due to this breakage at a lower temperature, any heating of the transistor is limited.

[0019] In other words, in the event of a transistor malfunction, the temperature of the electrically insulating overlay of the power module according to the invention remains lower than that of the power module according to the prior art, making it less likely for the power module according to the invention to catch fire.

[0020] The power module according to the invention may further include one or more of the following optional features, which may be considered individually or even in any technically possible combination.

[0021] According to another feature, the difference between distance D3 and distance D2 is greater than or equal to the thickness of the strip or wire, preferably greater than or equal to twice the thickness of the strip or wire.

[0022] The relationship between the distances of D2, D3 and the thickness of the strip or wire ensures that there is a minimum resin thickness above the transistor, so that the transistor is properly protected by the resin.

[0023] According to another feature, the cavity has a flat bottom, and the power module is characterized in that the orthogonal projection of the highest point of the strip or wire on the reference plane is included in the orthogonal projection of the flat bottom on the reference plane, and the difference between the distance D1 of the highest point of the strip or wire relative to the reference plane and the thickness of the strip or wire is greater than or equal to the difference between the distance D3 and the distance D2.

[0024] According to another feature, a strip or wire forms a second bridge, one end of which is flat on the upper surface of the transistor and the other end of which is flat on the upper surface of the motherboard of the second electrical connection portion. The orthogonal projection of the highest point of the second bridge onto the reference plane is included in the orthogonal projection of the flat bottom of the cavity onto the reference plane. The difference between the distance D6 of the highest point of the second bridge relative to the reference plane and the thickness of the strip or wire is greater than or equal to the difference between the distance D3 and the distance D2.

[0025] According to another feature, the transistor is connected to the upper surface of the motherboard of the second electrical connection portion via multiple strips and / or wires, and the cavity has a flat bottom. The power module is characterized in that the orthogonal projection of the highest point of each strip and / or wire onto the reference plane is included in the orthogonal projection of the flat bottom of the cavity onto the reference plane, and for each strip and / or wire, the difference between the distance of the highest point of the strip and / or wire relative to the reference plane and the thickness of the strip or wire is greater than or equal to the difference between distance D3 and distance D2.

[0026] According to another feature, the cavity is at least partially located above the highest part of the strip or wire.

[0027] According to another feature, the cavity is at least partially located above the first bridge.

[0028] According to another feature, the cavity is at least partially located above the second bridge.

[0029] According to another feature, the first electrical connection portion is designed to be connected to the positive terminal of a DC voltage source.

[0030] According to another feature, the second electrical connection portion is intended to be connected to a phase of the rotating motor.

[0031] According to another feature, the first electrical connection portion includes at least one electrical connector protruding from its motherboard.

[0032] According to another feature, the electrical connector of the first electrical connection portion protrudes from the main board of the first electrical connection portion into the main plane.

[0033] According to another feature, the electrical connector and the main board supporting the first electrical connection portion of the electrical connector are made as a single continuous material.

[0034] According to another feature, the second electrical connection portion includes at least one electrical connector protruding from its motherboard.

[0035] According to another feature, the electrical connector of the second electrical connection portion protrudes from the main board of the second electrical connection portion into the main plane.

[0036] According to another feature, the electrical connector and the main board of the second electrical connection portion supporting the electrical connector are made as a single continuous material.

[0037] According to another feature, the transistor is electrically connected to the upper surface of the motherboard of the first electrical connection portion.

[0038] According to another characteristic, the electrically insulating overmolded part is a single piece.

[0039] According to another characteristic, the cavity is filled with gel or resin, which has a lower hardness than the electrically insulating overmolded part.

[0040] According to another characteristic, the transistor is either a FET ("field-effect transistor") type transistor or an IGBT ("insulated-gate bipolar transistor") type transistor.

[0041] According to another characteristic, FET-type transistors are MOSFET transistors made of silicon (Si-MOSFET) or silicon carbide (SiC-MOSFET), or FET transistors made of gallium nitride (GaN-FET).

[0042] According to another characteristic, the transistor is, for example, a HEMT ("high electron mobility transistor") made of gallium nitride.

[0043] According to another characteristic, transistors are in the form of plates, for example, they are basically rectangular, with an upper surface and a lower surface.

[0044] According to another feature, the lower surface of the transistor presses against the upper surface of the motherboard to which the transistor is mounted in the first electrical connection portion.

[0045] According to another feature, the transistor is electrically connected to the upper surface of the motherboard of the first electrical connection portion via its lower surface.

[0046] According to another feature, the overmolded part has a resin pad that protrudes downwards.

[0047] According to another feature, the motherboards are separated from each other by at least one gap along the main plane, and an overmolded part fills each gap, and has a lower surface in each gap that is flush with the lower surface of the motherboard.

[0048] According to another feature, the resin pad protrudes from the lower surface of the overmolded part present in the gap.

[0049] According to another feature, the electrical connection portion is obtained by cutting a single metal plate.

[0050] According to another feature, the overmolded part exposes at least a portion of the lower surface of the motherboard with at least one electrical connection portion, the exposed portion being designed to press against the heatsink.

[0051] According to another feature, the cavity is at least partially cut in the upper surface of the electrically insulating overmolded part by laser ablation.

[0052] It should be noted that the relationship between distances D2, D3, and D4 also ensures that there is a sufficient resin layer between the cavity bottom and the transistor, so that the transistor is not damaged during the laser ablation process in the cavity.

[0053] According to another feature, the cavity has a flat bottom.

[0054] According to another feature, the flat bottom of the cavity is composed of multiple steps located at different heights.

[0055] According to another feature, the bottom of the cavity is flat, except for the protrusion located below the strip or wire.

[0056] According to another feature, the bottom of the cavity is flat, except for the protrusions located under each strip and / or each wire.

[0057] According to another feature, the protruding part rises from the flat bottom of the cavity.

[0058] According to a second aspect of the invention, an electrical system is also provided, comprising a heat sink and a power module according to a first aspect of the invention, wherein the heat sink is in thermal contact with a lower surface exposed by an overmolded member.

[0059] According to a third aspect of the invention, a voltage converter is also proposed, which includes a power module according to the first aspect of the invention or even an electrical system according to the second aspect of the invention.

[0060] This voltage converter is designed to connect between a power source providing DC voltage and a rotating motor, for performing conversion between the DC voltage of the power source and at least one phase voltage of the rotating motor. Attached Figure Description

[0061] The invention will be better understood from the following description, which is provided by way of example only and with reference to the accompanying drawings, wherein:

[0062] Figure 1 An electrical system including a voltage converter implementing the invention is illustrated schematically in a first embodiment of the invention;

[0063] Figure 2 In the first embodiment of the present invention Figure 1 An exploded 3D view of the voltage converter;

[0064] Figure 3 In the first embodiment of the present invention Figure 2 A three-dimensional top view of the power module of the voltage converter, without overlay molding;

[0065] Figure 4 It is similar to Figure 3 The view shows an overmolded part;

[0066] Figure 5 yes Figure 3 and 4 A three-dimensional bottom view of the power module, featuring an overmolded component;

[0067] Figure 6 This is a schematic diagram illustrating the relationship between some physical dimensions of the power module in the first embodiment of the present invention;

[0068] Figure 7 This is a schematic diagram illustrating the relationship between some physical dimensions of the power module in a second embodiment of the present invention; and

[0069] Figure 8 This is a schematic diagram illustrating the relationship between some physical dimensions of the power module in the third embodiment of the present invention. Detailed Implementation

[0070] refer to Figure 1 The electrical system 100 that implements the invention in the first embodiment will now be described.

[0071] For example, electrical system 100 is intended to be installed in a motor vehicle.

[0072] The electrical system 100 first includes a power supply 102, which is designed to provide a DC voltage U, for example, in the range of 10 V and 100 V, such as 48 V or even 12 V.

[0073] Therefore, power supply 102 is a DC voltage source. This power supply includes, for example, a battery.

[0074] The electrical system 100 also includes a motor 130, which includes multiple phases (not shown) having their own phase voltages.

[0075] The electrical system 100 also includes a voltage converter 104 connected between the power supply 102 and the motor 130 to perform the conversion between DC voltage U and phase voltage.

[0076] The voltage converter 104 first includes a positive bus 106 and a negative bus 108, which are designed to be connected to a power supply 102 to receive a DC voltage U. The positive bus 106 receives a high potential and the negative bus 108 receives a low potential.

[0077] The voltage converter 104 also includes at least one power module 110. The power module 110 includes one or more phase buses, which are respectively connected to one or more phases of the motor 130 to provide their respective phase voltages.

[0078] In the described example, the voltage converter 104 includes three power modules 110, each power module including two phase buses 1221, 1222 connected to the two phases of the motor 130.

[0079] More specifically, in the described example, motor 130 includes two three-phase systems, each comprising three phases, and is designed to be electrically phase-shifted by 120° to each other. Preferably, the first phase bus 1221 of power module 110 is connected to the three phases of the first three-phase system, and the second phase bus 1222 of power module 110 is connected to the three phases of the second three-phase system.

[0080] For each phase bus 1221, each power module 110 includes a first electrical component (in this case, a high-side switch 1121) connected between the positive bus 106 and the phase bus 1221, and a second electrical component (in this case, a low-side switch 1141) connected between the phase bus 1221 and the negative bus 108. Thus, switches 1121 and 1141 are arranged to form switch arms, with the phase bus 1221 forming a center tap.

[0081] For each phase bus 1222, each power module 110 also includes a third electrical component (in this case, a high-side switch 1122) connected between the positive bus 106 and the phase bus 1222, and a fourth electrical component (in this case, a low-side switch 1142) connected between the phase bus 1222 and the negative bus 108. Thus, switches 1122 and 1142 are arranged to form switch arms, with the phase bus 1222 forming a center tap.

[0082] Each switch 1121, 1141, 1122, 1142 includes first and second main terminals 116, 118 and a control terminal 120 for selectively opening and closing the switch 1121, 1141, 1122, 1142 between its two main terminals 116, 118 according to a control signal applied thereto. Switches 1121, 1141, 1122, 1142 are preferably transistors, such as metal-oxide-semiconductor field-effect transistors (MOSFETs), with their gate forming the control terminal 120 and their drain and source forming the main terminals 116, 118, respectively. Alternatively, switches 1121, 1141, 1122, 1142 may be insulated-gate bipolar transistors (or IGBTs).

[0083] In the described example, switches 1121, 1141, 1122, and 1142 each take the form of a plate, for example, which is generally rectangular and has an upper surface and a lower surface. A first main terminal 116 extends on the lower surface, while a second main terminal 118 extends on the upper surface. Switches 1121, 1141, 1122, and 1142 are designed to allow a current greater than 1 A to pass through between their main terminals 116 and 118.

[0084] It should be understood that the positive busbar 106, negative busbar 108, and phase busbars 1221 and 1222 are rigid electrical conductors designed to withstand a current of at least 1 A, which is intended to pass through switches 1121, 1141, 1122, and 1142. They are preferably at least 1 mm thick.

[0085] Furthermore, in the described example, the positive bus 106 first includes a positive common bus 106A connecting the power modules 110, and in each power module 110, includes a positive local bus 106B connected to the positive common bus 106A. Similarly, the negative bus 108 includes a negative common bus 108A connecting the power modules 110, and in each power module 110, includes negative local buses 108B1, 108B2 for each low-side switch 1141, 1142, wherein the negative local buses 108B1, 108B2 are connected to the negative common bus 108A. The connections are shown as a diamond shape in the figure.

[0086] Furthermore, in the described example, both the positive common bus 106A and the negative common bus 108A are formed by a single conductive portion.

[0087] Furthermore, in the described example, motor 130 is a rotating electric motor that functions as both an alternator and an electric motor. More specifically, the vehicle also includes an internal combustion engine (not shown) with an output shaft, to which motor 130 is connected via a belt (not shown). The internal combustion engine is intended to drive the wheels of the vehicle through its output shaft. Therefore, during operation as an alternator, motor 130 supplies electrical energy to power source 102 from the rotation of its output shaft. Voltage converter 104 then operates as a rectifier. During operation as an electric motor, the motor drives the output shaft (in addition to or in place of the internal combustion engine). Voltage converter 104 then operates as an inverter.

[0088] The motor 130 is located, for example, in a gearbox or in the clutch of a motor vehicle, or as an alternative to an alternator.

[0089] The structure and layout of the components of the voltage converter 104 will be described in further detail with reference to the vertical direction HB, where "H" represents the top and "B" represents the bottom. This vertical direction HB is indicated by the reference symbol V in the figures.

[0090] refer to Figure 2 The voltage converter 104 includes a heat sink 206 with a heat exchange surface 204, and a power module 110. Figure 2 The diagram shows a single power module 110 mounted on the heat sink 206. Heat exchange between the heat exchange surface 204 of the heat sink 206 and the power module 110 occurs, for example, through direct contact between the heat exchange surface 204 of the heat sink 206 and the power module 110 or through thermal paste.

[0091] The voltage converter 104 also includes a support housing 208, on which secondary electronic modules, such as the control module 210, are fixed. Figure 1 In the example, control module 210 is a control board. Alternatively, support housing 208 is mounted on heat sink 206.

[0092] refer to Figure 3 The power module 110 will now be described.

[0093] The power module 110 includes a plurality of electrical connection portions 304, 3041, 3042, and 3043, preferably made of metal.

[0094] Each electrical connection portion 304, 3041, 3042, 3043 has a motherboard 306, 3061, 3062, 3063 extending along a horizontal principal plane PP, the horizontal principal plane being identical for all motherboards 306, 3061, 3062, 3063, such that motherboards 306, 3061, 3062, 3063 are substantially coplanar. Specifically, in the described example, motherboards 306, 3061, 3062, 3063 have corresponding horizontal upper surfaces 308, 3081, 3082, 3083 extending at the same height. For clarity, upper surfaces 308, 3081, 3082, 3083 are shown only in the figures of the largest motherboards 306, 3061, 3062, 3063.

[0095] Specifically, the power module 110 includes a first electrical connection portion 3041 having a motherboard 3061 including an upper surface 3081, a second electrical connection portion 3042 having a motherboard 3062 including an upper surface 3082, and a third electrical connection portion 3043 having a motherboard 3063 including an upper surface 3083.

[0096] Furthermore, motherboards 306, 3061, 3062, and 3063 are separated from each other by at least one gap 310 along the main plane PP. In the described example, the width of each gap 310 is less than or equal to 5 mm. This means that the two motherboards defining the gap 310 are separated by a maximum of 5 mm along the gap 310.

[0097] Generally, at least one electrical connection portion 304 (in all the examples described) also has at least one electrical connector protruding from its main body 306, 3061, 3062, 3063. Each electrical connector is, for example, in the form of a pin 3121, or in the form of folded tabs 3122, 3123, or even in the form of a straight tab 3124.

[0098] In the example described here, the straight tab 3124 together with its main boards 3062 and 306 forms phase busbars 1221 and 1222, the folded tab 3123 together with its main board 3061 forms positive local busbar 106B, and the folded tab 3122 together with its main boards 3063 and 306 forms negative local busbars 108B1 and 108B2.

[0099] Each electrical connector 3121, 3122, 3123 has a fixed end 314 that is secured to the mainboard 306, 3062, 3063, 3061. In the example described, the body portion 316 extends vertically and terminates at a free end 318 and an elbow 320 that connects the fixed end 314 to the body portion 316. For clarity, these different elements of the electrical connectors 3121, 3122, 3123 are shown in the figures only for two electrical connectors 3121 and 3122, one in the form of a pin and the other in the form of a tab.

[0100] In the case of a straight tab, the electrical connector 3124 protrudes a considerable length into the main plane PP, for example, at least one centimeter, to allow it to be connected. Furthermore, the electrical connector 3124 has a retaining end 314 that is fixed to the main board 306, and this retaining end 314 is very wide, for example, at least one centimeter, to allow current to pass through.

[0101] In the described example, the electrical connection portion 304 is obtained by cutting from a metal plate.

[0102] In the example described here, the metal plate is made of copper. As an alternative embodiment, the metal plate could be made of aluminum or even gold.

[0103] Furthermore, as previously described, the power module 110 includes transistors 1121, 1122, 1141, and 1142, each transistor electrically connected between two upper surfaces 308, 3081, 3082, and 3083 of the two main boards 306, 3061, 3062, and 3063, for example, to allow and, if necessary, interrupt a power current, which may be, for example, greater than one ampere between the two main boards 306, 3061, 3062, and 3063. Each transistor 1121, 1122, 1141, and 1142 first has a lower surface pressed against one of the two upper surfaces 308, 3081, and 3082 to which it is electrically connected. Each transistor 1121, 1122, 1141, and 1142 also has an upper surface, a portion of which is electrically connected to the other of the two upper surfaces. In the described example, the upper surface of transistors 1121, 1122, 1141, and 1142 also includes a portion for controlling transistors 1121, 1122, 1141, and 1142, which is electrically connected, for example, to the upper surface of the third motherboard 306 via wire 328 in the described example.

[0104] In other words, transistor 1121 is mounted on and electrically connected to the upper surface 3081 of the motherboard 3061 of the first electrical connection portion 3041, and the first electrical connection element electrically connects transistor 1121 to the upper surface 3082 of the motherboard 3062 of the second electrical connection portion 3042.

[0105] The first electrical connection element includes two strips 3261, one end of each metal strip 3261 being soldered to the upper surface 3082 of the main board 3062 of the second electrical connection portion 3042 using a soldering method. The second end of each metal strip 3261 is then directly soldered to the transistor 1121 using a soldering method, such as ultrasonic or friction soldering.

[0106] In the example described here, the two strips 3261 are essentially the same shape.

[0107] Similarly, transistor 1141 is mounted on the upper surface 3082 of motherboard 3062 and electrically connected to the second electrical connection portion 3042, and the second electrical connection element electrically connects transistor 1141 to the upper surface 3083 of motherboard 3063 of the third electrical connection portion 3043.

[0108] The second electrical connection element includes two strips 3262, one end of each metal strip 3262 being soldered to the upper surface 3083 of the main board 3063 of the third electrical connection portion 3043 using a soldering method. The second end of each metal strip 3262 is directly soldered to the transistor 1141 using a soldering method, such as ultrasonic or friction soldering.

[0109] Similarly, transistors 1122 and 1142 are mounted on the upper surfaces 308 and 3081 of the main boards 306 and 3061, which are electrically connected to the electrical connection portions 304 and 3041, and their upper surfaces are electrically connected to one of the upper surfaces of another main board 306 via two strips 326 of the same shape.

[0110] In the described example, strips 326, 3261, and 3262 are made of aluminum and have a cross-section of, for example, 2 mm × 0.3 mm. In an alternative embodiment, strips 326, 3261, and 3262 are made of gold.

[0111] In the described example, wire 328 is made of aluminum and has a diameter of 0.2 mm. In an alternative embodiment, wire 328 is made of gold.

[0112] In the described example, the pin-shaped electrical connector 3121 is used to connect the power module 110 to the control module 210 in order to measure electrical values ​​and control transistors 1121, 1122, 1141, and 1142.

[0113] Furthermore, in the example still described, electrical connector 3122 is connected to the negative common bus 108A, and electrical connector 3123 is connected to the positive common bus 106A.

[0114] Furthermore, in the example described, two electrical connectors 3124 in the form of straight tabs form two phase buses 1221 and 1222 of the power module 110, respectively.

[0115] refer to Figure 4 The diagram shows the overmolded portion of the power module 110, which is indicated by reference numeral 402.

[0116] The overmolded component 402 is an electrical insulator and completely covers at least a portion of the upper surfaces 3081, 3082, 3083, and 308 of each transistor 1121, 1122, 1141, 1142 and the motherboards 3061, 3062, 3063, 306.

[0117] In the example described here, the overmolded part 402 also completely covers each wire 328.

[0118] In addition, the upper surface of the electrically insulating overmolded part 402 has a first cavity C1 located at least partially above the highest part of the first electrical connection element.

[0119] The first cavity C1 is at least partially cut out, for example, in the upper surface of the electrically insulating overmolded part 402 by laser ablation. By design, the bottom of the first cavity C1 is flat, for example, consisting of multiple steps at different heights, except for a protrusion rising from the flat bottom of the first cavity, which is located below each of the two strips 3261.

[0120] A portion of strip 3261 is therefore located in the first cavity C1, and the electrically insulating overmolded part 402 covers the remainder of strip 3261. In other words, the electrically insulating overmolded part 402 partially covers strip 3261 such that only the highest portion of strip 3261 in the top-to-bottom direction is not covered by the electrically insulating overmolded part 402, and is also located in the first cavity C1.

[0121] In this way, the electrically insulating overmolded parts are subjected to a small or no holding force on the highest part of the strip 3261, which allows these strips to break easily when heated.

[0122] Similarly, the upper surface of the electrically insulating overmolded part 402 has a second cavity C2 located at least partially above the highest portion of the second electrical connection element 3262.

[0123] A portion of strip 3262 is therefore located in the second cavity C2, and the electrically insulating overmolded part 402 covers the remainder of strip 3262. In other words, the electrically insulating overmolded part 402 partially covers strip 3262 such that only the highest portion of strip 3262 in the top-to-bottom direction is not covered by the electrically insulating overmolded part 402, and is also located in the second cavity C2.

[0124] For the same reason as before, the electrically insulating overmolded part 402 applies a small holding force or no holding force on the highest part of the strip 3262, which allows the strips to break easily when heated.

[0125] Finally, the upper surface of the electrically insulating overmolded part 402 also has a third cavity C3 and a fourth cavity C4, which are at least partially located above the strips 326 of transistors 1122 and 1142, respectively, and are deep enough that only the upper portions of the strips 326 of transistors 1122 and 1142 are located in the third cavity C3 and the fourth cavity C4, respectively, so that the electrically insulating overmolded part 402 covers the rest of the strips 322.

[0126] The overmolded part 402 is made of resin, for example, or even epoxy resin. Preferably, the overmolded part 402 is integral as a single piece.

[0127] In the embodiments described herein, the cavity is empty of material. As an alternative embodiment, the cavity is filled with a gel, such as a dielectric and / or a silicone gel. The gel may also have a viscosity of 230-600 mPa⁻², preferably 400-500 mPa⁻², for example 465 mPa⁻², and / or may have a hardness of 65-180 g, preferably 110-160 g, for example 123 g or 154 g.

[0128] In another alternative embodiment, the cavity-filling resin is different from the resin forming the electrically insulating overmolded part 402. Specifically, the hardness of the cavity-filling resin is less than the hardness of the resin forming the electrically insulating overmolded part 402. For example, the electrically insulating overmolded part 402 is formed of, for example, an epoxy resin with a hardness between 70 and 90 Shore A, and the cavity is filled with, for example, an elastomeric resin with a hardness between 20 and 40 Shore A. The cavity-filling resin also meets the UL 94 V-0 fire rating, as defined by Underwriters Laboratories.

[0129] Figure 5 This is a bottom view of power module 110.

[0130] As can be seen from the figure, the overmolded part 402 exposes the lower surface 5021 of the motherboard 3061 of the first electrical connection portion 3041. This exposed portion is designed to press against the heat sink 206. Therefore, the heat sink 206 is in thermal contact with the lower surface 5021 exposed through the overmolded part 402. This thermal contact can be direct contact, or even contact through an insulated and thermally conductive electrical connection element.

[0131] Similarly, the overmolded part 402 exposes the lower surfaces 502, 5022, 5023 of the motherboards 306, 3062, 3063 for each of the other electrical connection portions 304, 3042, 3043. These exposed portions are designed to press against the heat sink 206. Therefore, the heat sink 206 is in thermal contact with the lower surfaces 502, 5022, 5023 exposed by the overmolded part 402. This thermal contact can be direct contact, or even contact via insulated and thermally conductive electrical connection elements.

[0132] In addition, the overmolded part 402 fills each gap 310 and has a lower surface in each gap 310 that is flush with the lower surface 502 of the main board 306.

[0133] The overmolded component 402 has at least one resin pad 506 that protrudes downward and is designed to directly contact the heat sink 206 to define a predetermined space between the lower surfaces 502, 5021, 5022, 5023 of the motherboards 306, 3061, 3062, 3063 and the heat sink 206, thereby defining the thickness of the thermally conductive element filling the space. In the described example, each resin pad 506 protrudes from the lower surface of the overmolded component in one of the gaps 310 present between the motherboards 306, 3061, 3062, 3063.

[0134] Figure 6 A partial view of the power module 110 is shown along a cut plane perpendicular to the main plane PP and passing through one of the strips of the first electrical connection element.

[0135] First, it should be noted that the upper surface of the first transistor 1121 defines the reference plane p.

[0136] Two identical strips 3261 each form the first bridge PO1 and the second bridge PO2.

[0137] The two ends of the first bridge PO1 are flatly located on the upper surface of the first transistor 1121. The orthogonal projection of the highest point of the first bridge PO1 onto the reference plane P is included in the orthogonal projection of the flat bottom of the first cavity C1 onto the reference plane P.

[0138] One end of the second bridge PO2 is flatly located on the upper surface of the first transistor 1121, and the other end of the second bridge PO2 is flatly located on the upper surface of the main board 3062 of the second electrical connection portion 3042. The orthogonal projection of the highest point of the second bridge PO2 onto the reference plane P is included in the orthogonal projection of the flat bottom of the first cavity C1 onto the reference plane P.

[0139] In the example described here, the two bridges PO1 and PO2 of the two strips 3261 have the same height. Thus, the orthogonal projection of the highest point of each strip 3261 onto the reference plane is included in the orthogonal projection of the flat bottom of the cavity onto the reference plane (P).

[0140] The relationship between the physical dimensions of strip 3261, overmolded part 402 and first cavity C1 will now be shown.

[0141] In the following description, height is defined relative to the top-bottom dimensions described above.

[0142] Distance D2 is the distance between a plane parallel to the reference plane passing through the highest point of the electrically insulating overmolded part 402 and a plane parallel to the reference plane P passing through the lowest point of the first cavity C1.

[0143] Distance D3 is the distance between a plane parallel to the reference plane P passing through the highest point of the electrically insulating overmolded part 402 and the reference plane P.

[0144] Distance D4 corresponds to the same thickness in each of the two strips 3261.

[0145] These distances D2, D3, and D4 are configured such that the difference between distances D3 and D2 is greater than or equal to twice the distance D4. In other words, distances D3, D2, and D4 verify the equation:

[0146] [Mathematical Relationship 1]

[0147]

[0148] By means of this mathematical relationship, the existence of a minimum resin thickness above the first transistor 1121 is ensured, so that the first transistor is properly protected by the resin.

[0149] Furthermore, this minimum resin thickness ensures that the first transistor 1121 is not at risk of being damaged when laser ablation of the first cavity C1 is performed.

[0150] Furthermore, if distance D5 is defined as the distance from the highest point of the first bridge PO1 to the reference plane P, then distances D5, D2, D3, and D4 are also configured such that the difference between distances D5 and D4 is greater than or equal to the difference between distances D3 and D2.

[0151] In other words, distances D2, D3, D4, and D5 verify the equation:

[0152] [Mathematical Relationship 2]

[0153]

[0154] Similarly, if distance D6 is defined as the distance of the highest point of the first bridge PO2 relative to the reference plane P, then distances D6, D2, D3, and D4 are also configured such that the difference between distances D6 and D4 is greater than or equal to the difference between distances D3 and D2.

[0155] In other words, distances D2, D3, D4, and D6 validate the equation:

[0156] [Mathematical Relationship 3]

[0157]

[0158] With the help of these mathematical relationships, the upper ends of the two bridges PO1 and PO2 are located in the first cavity C1, so that the overmolded part 402 applies little or no pressure to these upper ends.

[0159] In the described example, the two bridges PO1 and PO2 have the same height, and therefore the distances D5 and D6 are equal. The distances D5 and D6 are also equal to the distance D1 between the highest point of each of the two identical strips 3261 and the reference plane P.

[0160] In other words, distances D1, D3, D2, and D4 verify the equation:

[0161] [Mathematical Relationship 4]

[0162]

[0163] Clearly, there is the same relationship between the physical dimensions of strip 3262, overmolded part 402 and second cavity C2, as well as between the physical dimensions of strip 326, overmolded part 402 and cavities C3 and C4.

[0164] refer to Figure 7 The second embodiment of the invention will now be described. Elements that are the same as or similar to those in the first embodiment are referred to using the same reference numerals in the description of the second embodiment.

[0165] The second embodiment differs from the first embodiment in the shape of the strip 3261 and the size of the first cavity C1.

[0166] More specifically, for the two strips 3261, the second bridge PO2 has a higher height than the first bridge PO1 and creates a first cavity C1, such that the first bridge PO1 is completely covered by resin.

[0167] In the first embodiment, distances D2, D3, and D4 are configured such that the difference between distances D3 and D2 is greater than or equal to twice the distance D4. In other words, distances D3, D2, and D4 verify mathematical relation 1 of equation.

[0168] Furthermore, distances D2, D3, D4, and D6 validate mathematical relation 3 of equation 3.

[0169] Obviously, in this second embodiment, there is the same relationship between the physical dimensions of strip 3262, overmolded part 402 and second cavity C2, and between the physical dimensions of strip 326, overmolded part 402 and cavities C3 and C4.

[0170] refer to Figure 8 The third embodiment of the invention will now be described. Elements that are the same as or similar to those in the first or second embodiments are referred to using the same reference numerals in the description of the third embodiment.

[0171] The difference between this third embodiment and the first embodiment is that the two stripes are not the same.

[0172] Therefore, the height of the second bridge PO'2 of one of the two strips 326'1 is higher than the height of the second bridge PO2 of the other strip 3261.

[0173] As shown in the figure, the orthogonal projection of the highest point of each strip 3261, 326'1 onto the reference plane P is included in the orthogonal projection of the flat bottom of the first cavity C1 onto the reference plane P. For each strip 3261, 326'1, the difference between the distance of the highest point D6, D6' of the strip relative to the reference plane P and the thickness D4 of the strip is greater than or equal to the difference between the distance D3 and the distance D2.

[0174] It should also be noted that the present invention is not limited to the foregoing embodiments. In fact, it will be apparent to those skilled in the art that various modifications can be made to the above embodiments based on the teachings just disclosed to them.

[0175] For example, all or some of the strips 326, 3261, and 3262 can be replaced by wires and / or fuses.

[0176] As another example, transistors 1121, 1141, 1122, and 1142 can be FETs or HEMT transistors made of gallium nitride.

[0177] Furthermore, in the embodiments described above, each electrical connection element has a strip. As an alternative embodiment, these electrical connection elements may have only one strip. In another alternative embodiment, these electrical connection elements may have at least three strips.

[0178] In the detailed description of the invention provided above, the terminology used should not be construed as limiting the invention to the embodiments disclosed herein, but must be understood to include all equivalents, which are contemplated by those skilled in the art by applying their general knowledge to the implementation of the teachings just disclosed to them.

Claims

1. A power module (110), comprising: - A first electrical connection portion (3041) and a second electrical connection portion (3042) made of metal, each electrical connection portion having a main board (3061, 3062) that extends along the same principal plane (PP) and is thus substantially coplanar; - A transistor (1121) mounted on the upper surface of the motherboard (3061) of the first electrical connection portion (3041), the upper surface of the transistor (1121) defining a reference plane (P), the transistor (1121) being electrically connected to the upper surface of the motherboard (3062) of the second electrical connection portion (3042) via at least one strip (3261) or via at least one wire; as well as - An electrically insulating overmolded part (402) covers at least a portion of the upper surface of the main board (3061, 3062) of the transistor (1121) and the first electrical connection portion (3041) and the second electrical connection portion (3042), the upper surface of the electrically insulating overmolded part (402) having a cavity (C1) at least partially located above the strip (3261) or wire; The power module (110) is characterized in that the cavity (C1) has a flat bottom, the strip (3261) or wire forms a first bridge (PO1) with both ends flatly located on the upper surface of the transistor (1121), the orthogonal projection of the highest point of the first bridge (PO1) on the reference plane (P) is included in the orthogonal projection of the flat bottom of the cavity (C1) on the reference plane (P), and wherein the difference between the distance D5 of the highest point of the first bridge (PO1) relative to the reference plane (P) and the thickness (D4) of the strip (3261) or wire is greater than or equal to the difference between the distance D3 between the plane parallel to the reference plane passing through the highest point of the electrically insulating overlay (402) and the distance D2 between the plane parallel to the reference plane passing through the highest point of the electrically insulating overlay (402) and the plane parallel to the reference plane passing through the lowest point of the cavity (C1).

2. The power module (110) according to claim 1, wherein, The difference between the distance D3 and the distance D2 is greater than or equal to the thickness (D4) of the strip or wire.

3. The power module (110) according to any one of the preceding claims, wherein, The cavity (C1) has a flat bottom, and the power module (110) is characterized in that the orthogonal projection of the highest point of the strip (3261) or wire onto the reference plane (P) is included in the orthogonal projection of the flat bottom onto the reference plane (P), and the difference between the distance D1 of the highest point of the strip (3261) or wire relative to the reference plane (P) and the thickness (D4) of the strip or wire is greater than or equal to the difference between the distance D3 and the distance D2.

4. The power module (110) according to any one of claims 1 to 2, wherein, The strip (3261) or wire forms a second bridge (PO2), one end of which is flatly located on the upper surface of the transistor (1121), and the other end of which is flatly located on the upper surface of the main board (3062) of the second electrical connection portion (3042), wherein the orthogonal projection of the highest point of the second bridge (PO2) on the reference plane (P) is included in the orthogonal projection of the flat bottom of the cavity (C1) on the reference plane (P), and wherein the difference between the distance D6 of the highest point of the second bridge (PO2) relative to the reference plane (P) and the thickness (D4) of the strip or wire is greater than or equal to the difference between the distance D3 and the distance D2.

5. The power module (110) according to any one of claims 1 to 2, wherein, The transistor (1121) is connected to the upper surface of the main board (3062) of the second electrical connection portion (3042) via multiple strips (3261) and / or wires, wherein the cavity (C1) has a flat bottom, and the power module (110) is characterized in that the orthogonal projection of the highest point of each strip (3261) and / or wire on the reference plane (P) is included in the orthogonal projection of the flat bottom of the cavity (C1) on the reference plane (P), and for each strip (3261) and / or wire, the difference between the distance (D61, D62) of the highest point of the strip and / or wire relative to the reference plane (P) and the thickness (D4) of the strip (3261) or wire is greater than or equal to the difference between the distance D3 and the distance D2.

6. The power module (110) according to any one of claims 1 to 2, wherein, The cavity (C1) has been at least partially cut in the upper surface of the electrically insulating overmolded part (402) by laser ablation.

7. The power module (110) according to any one of claims 1 to 2, wherein, The overmolded part (402) exposes at least a portion of the lower surface (5021, 5022) of the motherboard (3061, 3062) of at least one electrical connection portion (3041, 3042), the exposed portion being designed to press against the heat sink (206).

8. The power module (110) according to claim 2, wherein, The difference between the distance D3 and the distance D2 is greater than or equal to twice the thickness of the strip or wire.

9. The power module (110) according to claim 1, wherein, The electrically insulating overmolded part (402) is made of resin.

10. An electrical system (100) comprising a heat sink (206) and a power module according to any one of claims 1 to 9, wherein the heat sink (206) is in thermal contact with a lower surface exposed by an overmolded member (402).

11. A voltage converter (104) comprising a power module (110) according to any one of claims 1 to 9 or even an electrical system (100) according to claim 10.

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