Encapsulated power module and inverter for vehicle

Abstract

The utility model relates to a packaged power module and an inverter for a vehicle. The power module includes: a substrate having a conductor layer; one or more power electronic elements disposed on the conductor layer of the substrate; the metal wires and the bonding pads are used for carrying out lead bonding between the sub-elements of the one or more power electronic elements and the conductor layer on the substrate; and the epoxy resin material packaging piece is used for packaging the power module to form the packaged power module and is doped with low-melting-point alloy filler, and the epoxy resin material packaging piece doped with the low-melting-point alloy filler covers the substrate, the conductor layer, the power electronic component, the metal wire and the bonding pad. The power module is packaged by the epoxy resin material doped with the low-melting-point alloy, so that the heat-conducting property and the electromagnetic shielding property of the epoxy resin are improved, and sealed packaging can be performed by hot press molding.

Description

Technical Field

[0001] The present application relates to an inverter for a vehicle and a power module used in the inverter, and more particularly to a method of using SnBi in epoxy resin. 58 A method of encapsulating power modules as filler. Background Art

[0002] Power conversion is very important for the normal operation of various devices, especially in electric vehicles. The driving motor requires three-phase AC current, while all energy storage systems such as batteries require DC current. Therefore, the vehicle is equipped with an inverter to convert the DC current of the electric vehicle battery into AC current to drive the vehicle.

[0003] As the main component in the inverter, the power module plays an important role. The power module is also called a power electronic module, which provides physical accommodation for multiple power components (usually power semiconductor devices). These power semiconductor devices (also called chips) are usually welded or sintered on an electronic substrate that carries the power semiconductor devices, and finally they are packaged to form an integrated module, namely the power module. Compared with the case where discrete power semiconductor devices are provided in each plastic housing, the packaged power module provides higher power density and is more reliable in many cases.

[0004] For the encapsulation of these power modules, transfer molding with thermosetting polymers such as epoxy resin is usually used in the prior art. For this reason, epoxy resin has been widely used as an encapsulation material in the third-generation Evo and fourth-generation Volumelane inverters to completely encapsulate the chip and all lead connections. However, on the one hand, transfer molding of epoxy resin has obvious disadvantages: the material utilization rate is not high, and the materials in the transfer tank, wall and runner cannot be reused, resulting in a large amount of material waste; on the other hand, the epoxy resin used for encapsulation does not have any electromagnetic shielding or thermal conductivity function.

[0005] Electronic devices require effective heat dissipation to keep the operating temperature within a safe range. At the same time, since the frequency range of electronic components in the field of new energy vehicles is very wide, the electromagnetic interference shielding (EMI SE) performance of electronic packaging materials becomes crucial.

[0006] In order to solve this problem, it is necessary to improve the packaging materials by adding dual-functional material components with thermal conductivity and electromagnetic shielding properties into the design of electronic products. Utility Model Content

[0007] The purpose of the present application is to improve the packaging of a power module to enhance the heat dissipation capability and electromagnetic interference shielding of the packaged power module.

[0008] To achieve the above-mentioned objectives, the present application provides a packaged power module, which comprises: a substrate having a conductor layer; one or more power electronic components arranged on the conductor layer of the substrate; metal wires and pads for wire bonding between sub-components of the one or more power electronic components and the conductor layer on the substrate; and an epoxy resin material package doped with a low-melting-point alloy filler for packaging the power module to form a packaged power module, wherein the epoxy resin material package doped with a low-melting-point alloy filler covers the substrate, the conductor layer, the power electronic components, and the metal wires and pads.

[0009] Optionally, the epoxy resin material package mixed with low melting point alloy filler is at least one plate or film that is thermoformed onto the power module by an upper mold and a lower mold of a thermoforming mold.

[0010] Optionally, the substrate is an active metal welding substrate formed by welding a ceramic material and a metal material.

[0011] Optionally, the power module further includes a heat sink made of a thermally conductive material.

[0012] Optionally, the substrate and the heat sink are an integral part.

[0013] Optionally, the power module is a component in an inverter of a vehicle.

[0014] The present application also relates to an inverter for a vehicle, which includes the packaged power module as described above, a heat sink attached to the power module, and a housing accommodating the power module and the heat sink, wherein a coolant for cooling the heat sink is provided in the housing.

[0015] The method of forming a packaged power module of the present invention is to use SnBi 58 The epoxy resin material of the power module is sealed and packaged. On the one hand, the thermal conductivity and electromagnetic shielding interference performance of the packaging material are improved. On the other hand, due to the addition of SnBi 58 The special properties of epoxy resin materials enable epoxy resin to be used to seal and encapsulate power modules through a hot pressing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Embodiments of the present application will be described in more detail with reference to the accompanying drawings, in which:

[0017] Figure 1 A schematic diagram of a power module used in a component of a vehicle inverter according to the present application;

[0018] Figure 2 Schematic diagram of the mold used for hot pressing. DETAILED DESCRIPTION

[0019] In the following, embodiments according to the present application will be described with reference to the accompanying drawings. The accompanying drawings are not drawn to scale, but some parts are enlarged for clarity. The same or similar features in the accompanying drawings will be represented by the same reference numerals, and their repeated description will be omitted.

[0020] Figure 1 The schematic diagram of the packaged power module according to the present application being located in a component of a vehicle inverter is shown, wherein the inverter component includes a power module 10 and a housing 5 for accommodating the power module 10 and a heat sink 6 attached to the power module 10 in the housing 5. The power module 10 includes a substrate 1, which may be an active metal welded ceramic substrate (i.e., an AMB substrate), or a ceramic copper-clad substrate commonly used in the art, etc., wherein the ceramic material may be Al 2 O 3 、AlN、Si 3 N 4 Etc. A conductor layer 2, such as a copper layer, is provided on the substrate 1. Power electronic components, such as a chip 3, are also provided on the substrate 1. Common ones include SiC chips, thermistors, gate resistors, etc. The chip 3 as an example of a power electronic component can be mounted on the surface of the substrate 1 by sintering or other means known in the art, for example, it can be provided on the surface of the conductor layer 2. Various parts of the chip 3 (such as the gate of a transistor, etc.) can also be wire-bonded to the conductor layer 2 through a lead 4. For example, aluminum wires can be used to connect the gate of the chip 3 and the conductor layer 2, thereby forming a power module.

[0021] In order to enhance heat dissipation, a heat sink 6 is attached to the surface side of the substrate 1 of the power module 10 opposite to the chip 3. The heat sink 6 includes a heat sink and a plurality of heat sink fins 9 extending from the heat sink. Figure 1 As shown, in the assembled inverter component, if necessary, a coolant 15 in contact with the heat sink 6 can be provided in the housing 5 to exchange heat with the heat sink 6, thereby taking away the heat generated by the power electronic element 3 during operation to further cool the power module.

[0022] like Figure 1 As shown, the power module 10 is sealed by the packaging material 8 as a whole, that is, it becomes a packaged power module 10. The packaging material 8 is doped with SnBi 58 The epoxy resin material of the filler 7. The packaging material 8 can be used to package the power module 10 by transfer molding process, or by hot pressing molding process. 58 The filler accounts for at least 50% by weight of the epoxy resin material.

[0023] Although Figure 1 It is shown that only one power electronic component, namely chip 3, is connected to the substrate 1, but in fact, multiple power electronic components can be mounted on the substrate 1 as needed. For example, in addition to a module containing a single power electronic switch (such as MOSFET, IGBT, BJT, thyristor, GTO or JFET) or a diode, the power module can also accommodate multiple semiconductor chips, which are connected to form a circuit of a certain structure, called a topology. The module also includes other components, such as ceramic capacitors to reduce switching voltage overshoot and NTC thermistors to monitor the substrate temperature of the module. In power modules containing more semiconductor chips or electronic switches, heat dissipation and electromagnetic shielding of the power module become more important.

[0024] In the present application, the packaging material 8 is improved by using SnBi as an example of a low melting point alloy. 58 SnBi is added as filler to epoxy resin materials. 58 It is a low melting point alloy with low melting point, good wettability and mechanical properties, good electrical and thermal conductivity, and it shows potential advantages in electromagnetic shielding and heat dissipation. More importantly, low melting point alloy fillers can achieve the transition between the two existing states of rigid particles and deformable droplets in the polymer matrix, which makes low melting point alloy composites have some special properties that ordinary materials do not have.

[0025] The above-mentioned low melting point alloy (LMPA) in this application is described as SnBi 58 , but this is just an example, other materials can also be used as needed, these materials can be selected from indium, gallium, tin, bismuth and their compounds, their melting points are lower than 340°C at atmospheric pressure, and the performance of the composite material can be greatly improved by adding low melting point alloys. For example, studies have shown that the composite material obtained by introducing low melting point alloys into the matrix of polyvinylidene fluoride (PVDF) will show a continuous LMPA network structure partially wrapped by PVDF microspheres. When the loading amount of LMPA reaches 50%, the composite material shows 6.38Wm - 1 K -1 The thermal conductivity of the epoxy resin is increased by almost 2774% compared with pure PVDF resin. At the same time, excellent electromagnetic shielding (EMI SE) performance is also achieved, with a total EMI SE of -68.79dB at 10GHz. 58 , and the same order of improvement in thermal conductivity and electromagnetic shielding performance as the above-mentioned composite materials can also be achieved.

[0026] In this application, SnBi 58Epoxy resin as LMPA filler will be applied as encapsulation material in the power module. In the epoxy resin matrix, SnBi 58 The alloy particles surround multiple epoxy resin microspheres to form a ring-shaped network structure, which effectively improves the thermal conductivity and electromagnetic shielding effect of the epoxy resin matrix. 58 The alloy, as a "binder", solves the problem that thermosetting epoxy resin is difficult to form by hot pressing by virtue of the solid-liquid phase transition behavior of the low melting point alloy. 58 Fillers) can be thermoformed onto the surface of the component to be protected (power module), greatly reducing packaging cycle time and cost.

[0027] Therefore, the SnBi 58 The packaging material 8 of the filler can be used to package the power module 10 by a transfer molding process, or by a hot pressing molding process.

[0028] When the transfer molding process is adopted, firstly, one or more power electronic components such as chip 3 are mounted or sintered on substrate 1 as in the prior art process, and then chip 3 is wire bonded to form a power module. Then, the entire power module after mounting power electronic components such as chip 3 on substrate 1 and wire bonding is packaged. During packaging, substrate 1 is placed in a transfer molding mold (not shown in the figure), and then SnBi 58 The preformed block of epoxy resin material with filler (epoxy resin material is plastic or fluid at low temperature, and when it is heated to a certain temperature, a so-called cross-linking reaction occurs to form a rigid solid) is heated in a preheating furnace at a certain preheating temperature, and then put into the transfer tank of the transfer molding machine. Under the pressure of the transfer molding piston, the SnBi doped 58 The epoxy resin material with filler is extruded into the runner and injected into the mold cavity through the gate. 58 The epoxy resin material of the filler is quickly solidified in the mold. After a period of pressure maintenance, the power module 10 reaches a certain hardness. Then, the power module is ejected with an ejector pin, and the molding process is completed.

[0029] When the entire power module 10 is packaged by hot pressing after the power electronic components such as the chip 3 are mounted on the substrate 1 and wire-bonded, as shown in FIG. Figure 2 As shown, an exemplary hot pressing mold is shown, which has an upper mold 11 and a lower mold 12. Between the upper mold 11 and the lower mold 12, a SnBi doped 58The plate or film 13, 14 made of epoxy resin material with filler is then placed between the upper mold 11 and the lower mold 12, and placed in the SnBi doped 58 The epoxy resin plate or film 13 and 14 filled with fillers are then closed by closing the upper mold 11 and the lower mold 12, thereby 58 The epoxy resin plates 13 and 14 filled with fillers are thermoformed onto the power module 10 to encapsulate the power module 10 .

[0030] exist Figure 2 Two epoxy resin plates or films 13, 14 are shown in the figure, but as needed, for example, when only one side of the power module 10 needs to be sealed and packaged, only one epoxy resin plate or film 13, 14 can be set, and the power module 10 is placed between the plate or film and the upper mold 11 or the lower mold 12.

[0031] Generally, after being heated and cured, conventional epoxy resin cannot restore its fluidity even if heated again, and the epoxy resin cannot be hot-pressed. The reason why the packaging material 8 can be used to hot-press the power module 10 in the present application is that SnBi is doped in the epoxy resin. 58 Material.

[0032] In summary, the present application relates to a method for providing a packaged power module, comprising the following steps:

[0033] - Providing a substrate such as an active metal soldering substrate, and arranging power electronic components on the substrate, for example, mounting or sintering one or more power electronic components on a conductor layer of the substrate, wherein the power electronic components may be chips, for example.

[0034] -Provide leads for mounted power electronic components, so as to connect the sub-components of the power electronic components to the conductor layer on the substrate through the leads, realize the wire bonding of the power electronic components, and form a power module.

[0035] - Provided with SnBi doped 58 The epoxy resin material doped with SnBi 58 The epoxy resin material of the filler encapsulates the power module formed after the power electronic components are mounted and the wire bonding is completed.

[0036] Specifically, for the packaging step, on the one hand, the power module can be placed in a mold and 58 On the other hand, SnBi-doped 58 The epoxy resin material of the filler is thermoformed onto the power module for encapsulation.

[0037] By providing 58 The packaging material composed of the epoxy resin material of the filler can effectively dissipate the heat generated by the power module as an integrated electronic component during operation. In addition, in the inverter composed of this power module, the power module can also be combined with a heat sink made of a material with good thermal conductivity such as Al.

[0038] Although the figure shows that the heat sink 6 is a separate heat sink from the substrate 1, the substrate 1 and the heat sink 6 may be formed as an integral component as required, that is, the power module 10 may also be formed as a base 1 including an integral heat sink.

[0039] Although the present application is described in terms of preferred embodiments, this is not meant to limit the present application. It should be understood that the scope of protection of the present application is defined by the appended claims. Those skilled in the art may make various modifications without departing from the scope.

Claims

1. A packaged power module, the power module include: a substrate having a conductor layer; one or more power electronic components disposed on the conductive layer of the substrate; metal wires and pads for wire bonding between the one or more power electronic component subcomponents and the conductor layer on the substrate; and The invention discloses an epoxy resin material package doped with low melting point alloy filler for packaging a power module to form a packaged power module, wherein the epoxy resin material package doped with low melting point alloy filler covers the substrate, the conductor layer, the power electronic element, and the metal wires and pads.

2. The packaged power module according to claim 1, in, The epoxy resin material package mixed with low melting point alloy filler is at least one plate or film that is thermoformed onto the power module through an upper mold and a lower mold of a thermoforming mold.

3. The packaged power module according to claim 1 or 2, in, The substrate is an active metal welding substrate formed by welding ceramic material and metal material.

4. The packaged power module according to claim 3, in, The power module further comprises a heat sink made of a thermally conductive material.

5. The packaged power module according to claim 4, in, The substrate and the heat sink are integrated.

6. The packaged power module according to claim 1 or 2, in, The power module is a component in an inverter of a vehicle.

7. An inverter for a vehicle, comprising a packaged power module according to any one of claims 1 to 6, a heat sink attached to the power module, and a housing accommodating the power module and the heat sink, wherein a coolant for cooling the heat sink is also provided in the housing.

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