Power module, preparation method thereof and power equipment

Abstract

The invention relates to the field of electronic power, and discloses a power module, a preparation method thereof and power equipment. The power module comprises a first substrate, a second substrate, a chip and a packaging body, the first substrate comprises a first surface and a second surface, and the first surface is used for mounting the chip; the second substrate comprises a bearing surface, the bearing surface is used for bearing the first substrate, and the bearing surface is in contact with the second surface; the bearing surface comprises a first area and a second area, the first area is opposite to the first substrate, the second area is annularly arranged around the first area, and the surface material of the second area comprises copper, copper alloy or copper oxide; the packaging body is used for wrapping the chip, the first substrate and at least part of the second substrate, and the packaging body is in contact with the second area. No other metal coating or organic coating exists between the surface of the second area and the packaging body, so that high-strength connection between the second substrate and the packaging body can be realized, and the structural reliability of the power module can be improved.

Description

Technical Field

[0001] The present application relates to the field of electronic power, and particularly to a power module, a preparation method thereof, and a power device. Background Art

[0002] A power module is a functional module that combines power electrical components according to certain functions and then encapsulates or potting them into a whole with a plastic encapsulant, and is widely used in devices such as servo motors, frequency converters, and inverters. Considering the high heat dissipation and insulation requirements of the power module, a metal-clad ceramic substrate with significant advantages such as high temperature resistance, corrosion resistance, high mechanical strength, and non-deterioration is usually selected as the carrier of the electrical components in the power module, and a heat dissipation substrate with high thermal conductivity is selected as the carrier of the ceramic substrate to dissipate heat externally through the heat dissipation substrate.

[0003] Currently, the material of the heat dissipation substrate in the power module is generally copper. In actual applications, in order to prevent corrosion, a layer of nickel is usually plated on the surface of the heat dissipation substrate. However, the bonding force between the nickel layer and the plastic encapsulant is weak. When the external environment or the temperature inside the power module changes, due to the difference in the thermal expansion coefficients of different materials, the thermal stress will cause the connection between the heat dissipation substrate and the plastic encapsulant to break. In this way, the overall thermal stress inside the module will be concentrated on the ceramic substrate, and when the stress received by the ceramic substrate exceeds its strength threshold, cracking will occur, thereby resulting in the failure of the insulation withstand voltage of the power module. Summary of the Invention

[0004] The present application provides a power module, a preparation method thereof, and a power device to improve the structural strength of the power module.

[0005] In a first aspect, the present application provides a power module, which may include a first substrate, a second substrate, a chip, and a package. The first substrate includes a first surface and a second surface disposed opposite to each other in a first direction, and the first surface can be used to mount the chip. The second substrate includes a bearing surface for bearing the first substrate, and the bearing surface is in contact with the second surface of the first substrate. The bearing surface includes a first region and a second region. The projection of the first region in the first direction coincides with the projection of the second surface of the first substrate in the first direction. The second region is arranged in a ring shape around the first region, and the surface material of the second region includes copper, copper alloy, or copper oxide. The package is used to wrap at least part of the chip, the first substrate, and the second substrate, thereby encapsulating the power module into an integral whole. Since the second region is exposed in the area not covered by the second surface, the second region can form contact with the package. Also, since there is no other metal coating or organic coating between the surface of the second region and the package, the bonding force between the second substrate and the package is relatively strong. When the external environment or the temperature inside the power module changes, the second substrate and the package can still maintain sufficient connection strength under the action of thermal stress, and the first substrate also reduces the risk of cracking due to the reduced thermal stress, thereby significantly improving the structural reliability of the power module.

[0006] In some embodiments, the surface material of the first region may be the same as the surface material of the second region; in some other embodiments, the surface of the first region may have a metal coating.

[0007] In some embodiments, the surface roughness of the second region is greater than the surface roughness of the first region. By increasing the surface roughness of the second region, the connection strength between the second region and the package can be further improved.

[0008] Exemplarily, the second region can be roughened by means such as laser ablation, physical sandblasting, electroless plating, electroplating, physical sputtering, etc.

[0009] In some embodiments, the ring width of the second region may be greater than or equal to 2 mm. By designing the ring width h of the second region within the above size range, the connection strength between the second substrate and the package can be ensured to resist the action of thermal stress inside the power module, thereby reducing the risk of delamination between the second substrate and the package.

[0010] In some embodiments, the bearing surface includes a groove located within the second region, and the inner wall surface material of the groove includes copper, copper alloy, or copper oxide. The package can be partially filled in the groove, thereby improving the connection strength between the second substrate and the package by using the concave-convex fit between the groove and the package. Also, since the inner wall surface of the groove is also made of copper, copper alloy, or copper oxide material, it is equivalent to increasing the surface area of the second region, and thus helps to further improve the connection strength between the second substrate and the package.

[0011] In a specific implementation, the groove may be a ring structure. In this way, along the circumferential direction of the second region, high-strength connection can be achieved between any position of the second region and the package, and the connection strength between different positions and the package is relatively uniform, thereby reducing the risk of disconnection between the local area of the second substrate and the package.

[0012] In some embodiments, the bearing surface may further include a third region, which is arranged in a ring around the second region, and the surface roughness of the third region is less than that of the second region. In one implementation, the surface material of the third region may be the same as that of the second region; in another implementation, the surface of the third region may have a metal coating.

[0013] In some embodiments, the second substrate includes a plurality of fins, which can be arranged on the surface of the second substrate on the side facing away from the bearing surface, and the plurality of fins can be arranged at intervals in sequence. By using these fins, the heat dissipation area of the second substrate can be effectively increased, thereby improving the heat exchange efficiency between the second substrate and the external environment, and further contributing to improving the heat dissipation effect of the power module.

[0014] In a second aspect, the present application also provides a method for manufacturing a power module, and the manufacturing method may include the following steps:

[0015] Mount the chip on the first surface of the first substrate;

[0016] Place the first substrate on the first region of the bearing surface of the second substrate, and make the second surface of the first substrate contact the bearing surface. The second surface is the surface of the first substrate that is opposite to the first surface along the first direction, and the projection of the first substrate in the first direction coincides with the projection of the first region in the first direction;

[0017] Wrap at least part of the chip, the first substrate, and the second substrate in the package, and the package contacts the second region of the bearing surface, wherein the second region is arranged in a ring around the first region, and the surface material of the second region includes copper, copper alloy or copper oxide.

[0018] For the power module prepared by the above method, there is no other metal coating or organic coating between the surface of the second region and the package. Since the bonding force between copper, copper alloy or copper oxide and the package is relatively strong, when the external environment or the temperature inside the power module changes, the second substrate and the package can still maintain sufficient connection strength under the action of thermal stress, and the first substrate also reduces the risk of cracking due to the reduced thermal stress, thereby significantly improving the structural reliability of the power module.

[0019] In some embodiments, before fixing the first substrate to the first region of the bearing surface of the second substrate, the preparation method further includes:

[0020] Roughen the surface of the second region so that the surface roughness of the second region is greater than that of the first region, which can further improve the connection strength between the second region and the package, and thus help to further enhance the structural reliability of the power module.

[0021] In one implementation, the above-mentioned roughening of the surface of the second region specifically includes:

[0022] Roughen the surface of the second region of the bearing surface of the second substrate by a subtractive processing method, where the subtractive processing method includes laser ablation, chemical etching, physical sandblasting, etc.

[0023] In another implementation, the above-mentioned roughening of the surface of the second region specifically includes:

[0024] Roughen the surface of the second region of the bearing surface of the second substrate by an additive processing method, where the additive processing method includes electroplating, electroless plating, physical sputtering, etc.

[0025] In one implementation, the above-mentioned setting of the first substrate on the first region of the bearing surface of the second substrate specifically includes:

[0026] Use a solder without flux to set the first substrate on the first region of the bearing surface of the second substrate in an atmosphere of formic acid or a nitrogen-hydrogen mixed gas. Since the surface roughness of the second region of the bearing surface is relatively large, the surface of the second region is not wetted by the solder in an atmosphere of formic acid or a nitrogen-hydrogen mixed gas. Therefore, the solder will all concentrate on the first region, thus avoiding solder overflow to the second region and causing adverse effects on the subsequent packaging process.

[0027] In another implementation, when the surface material of the first region also includes copper, copper alloy or copper oxide, the above-mentioned setting of the first substrate on the first region of the bearing surface of the second substrate specifically includes:

[0028] Use a solder with flux to set the first substrate on the first region of the bearing surface of the second substrate. This method helps to enhance the welding effect between the first substrate and the second substrate, reduce the welding hole rate, and thus improve the welding strength between the first substrate and the second substrate.

[0029] In a third aspect, the present application further provides a power device, which may include a circuit board and the power module in any of the embodiments of the first aspect described above. The power module is electrically connected to the circuit board, so as to use the circuit board to provide functions such as current or voltage input and output and power supply for the power module. Brief Description of the Drawings

[0030] Figure 1 Schematic structural diagram of a photovoltaic system provided by an embodiment of the present application;

[0031] Figure 2 Schematic structural diagram of a power device provided by an embodiment of the present application;

[0032] Figure 3 Partial schematic structural diagram of a power module provided by an embodiment of the present application;

[0033] Figure 4 Partial schematic structural diagram of a power module provided by an embodiment of the present application;

[0034] Figure 5 Top view of a second substrate provided by an embodiment of the present application;

[0035] Figure 6 Top view of another second substrate provided by an embodiment of the present application;

[0036] Figure 7 Side view of a second substrate provided by an embodiment of the present application;

[0037] Figure 8 Side view of another second substrate provided by an embodiment of the present application;

[0038] Figure 9 Flowchart of a preparation method of a power module provided by an embodiment of the present application;

[0039] Figure 10 Flowchart of another preparation method of a power module provided by an embodiment of the present application.

[0040] Reference Signs:

[0041] 1000 - Power device; 100 - Housing; 200 - Circuit board; 300 - Power device; 310 - First substrate; 310a - First surface;

[0042] 310b - Second surface; 311 - Ceramic substrate; 312 - First metal layer; 313 - Second metal layer; 320 - Second substrate; 320a - Bearing surface;

[0043] 321 - First region; 322 - Second region; 323 - Third region; 324 - Groove; 325 - Fin; 330 - Chip; 340 - Package;

[0044] 350 - Pin; 360 - Solder. Detailed Description of the Embodiments

[0045] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings. However, the exemplary embodiments can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Identical reference numerals in the figures denote identical or similar structures, and thus their repeated description will be omitted. In the embodiments of this application, the words expressing positions and directions are described by taking the accompanying drawings as examples, but can be changed according to needs, and all such changes are included within the protection scope of this application. The accompanying drawings of the embodiments of this application are only used to illustrate the relative positional relationship and do not represent the true scale.

[0046] It should be noted that specific details are set forth in the following description to facilitate understanding of this application. However, the embodiments of this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the connotation of the embodiments of this application. Therefore, this application is not limited by the specific embodiments disclosed below.

[0047] Power devices are widely used in scenarios such as photovoltaic systems, energy storage systems, or the powertrain systems of new energy vehicles, etc., for performing power conversion on the current or voltage in the application system. Power devices can include inverters, micro-inverters in photovoltaic systems, or converters in energy storage systems, or motor controllers in the powertrain of new energy vehicles, etc.

[0048] Taking the photovoltaic system as an example, Figure 1 is a schematic structural diagram of a photovoltaic system provided by an embodiment of this application. The photovoltaic system includes one or more photovoltaic strings, an inverter, and a transformer. Among them, the photovoltaic string can include a plurality of photovoltaic modules connected in series. The photovoltaic module is a DC power source formed by encapsulating solar cells in series or in parallel, and is used to convert light energy into electrical energy; the inverter is a DC-AC power device, which can be used to convert the DC power output by the photovoltaic string into AC power and output it to the transformer; the transformer is used to step up the AC power output by the inverter and then merge it into the AC grid, thereby realizing the grid connection of the photovoltaic system.

[0049] Figure 2 is a schematic structural diagram of the power device 1000 provided by an embodiment of this application. This power device can be Figure 1 the inverter in the photovoltaic system shown, or can also be other types of power devices, and this application does not make any limitations in this regard. Refer to Figure 2As shown, the power device 1000 may include a housing 100, a circuit board 200 and a power module 300 contained in the housing 100, and the power module 300 is electrically connected to the circuit board 200. The circuit board 200 may be a printed circuit board (PCB), a flexible printed circuit (FPC), or a hard-soft circuit board. The power module 300 is a core component of the power device 1000 for realizing the power conversion function. The power module 300 may include multiple ports, such as input positive and negative ports, output positive and negative ports, power supply positive and negative ports, etc. These ports are electrically connected to the circuit board 200 through pins, so that the circuit board 200 is used to provide the power module 300 with current or voltage input and output and power supply functions.

[0050] The power module 300 may include various electrical components such as chips, inductors, resistors, capacitors, etc. These electrical components are connected according to certain functional combinations and then packaged into a whole through plastic packaging materials. The packaging material can protect the power components from the influence of the external environment (water vapor, temperature, dust impurities, etc.), and can achieve composite functions such as heat conduction, insulation, moisture resistance, pressure resistance, and support.

[0051] Considering the high heat dissipation and insulation requirements of the power module 300, a ceramic substrate with significant advantages such as high temperature resistance, corrosion resistance, high mechanical strength, and low degradation is usually selected as a carrier of the electrical device in the power module 300. Since the ceramic material itself is not conductive, in order to achieve electrical connection between the power module and the outside world, it is necessary to perform metallization wiring on the surface of the ceramic substrate formed by the ceramic material, so that the metal-coated ceramic substrate can reliably achieve thermal and electrical separation. In addition, a heat dissipation substrate is usually provided in the power module 300, and the heat dissipation substrate can be used as a carrier of the ceramic substrate and carried on the side of the ceramic substrate facing away from the power device.

[0052] The heat dissipation substrate is the core heat dissipation functional structure and channel of the power module 300, so it needs to have good thermal conductivity. At present, the material of the heat dissipation substrate in the power module 300 is generally copper. In practical applications, in order to prevent the heat dissipation substrate from corrosion and to improve the appearance of the heat dissipation substrate, a layer of nickel is usually plated on the surface of the heat dissipation substrate. However, the bonding force between the plated nickel and the plastic packaging material is weak. When the external environment or the temperature inside the power module 300 changes, due to the mismatch of the thermal expansion coefficients between different materials inside the power module 300, thermal stress will be generated between different materials. This thermal stress will cause the connection between the heat dissipation substrate and the plastic packaging material to be disconnected, causing the internal structure of the power module 300 to be layered. In this way, the overall thermal stress inside the module will be concentrated on the ceramic substrate. When the stress on the ceramic substrate exceeds its strength threshold, it will crack, which will cause the insulation withstand voltage failure of the power module 300.

[0053] In view of this, an embodiment of the present application provides a power module 300 and a power device 1000 applying the power module 300. There is a relatively strong bonding force between the heat dissipation substrate and the plastic encapsulation material of the power module 300, so as to reduce the risk of disconnection between the heat dissipation substrate and the encapsulation material, and reduce the thermal stress on the ceramic substrate, reducing the risk of cracking of the ceramic substrate. Furthermore, the structural strength of the power module 300 and the reliability of the power device 1000 applying the power module 300 can be improved. The power module 300 and the power device 1000 provided by the embodiments of the present application will be specifically described below with reference to the accompanying drawings.

[0054] Figure 3 It is a schematic partial structure diagram of a power module 300 provided by an embodiment of the present application. Refer to Figure 3 As shown, in the embodiment of the present application, the power module 300 may include a first substrate 310, a second substrate 320, a chip 330, and an encapsulation body 340. The first substrate 310 includes a first surface 310a and a second surface 310b, and the first surface 310a and the second surface 310b are arranged opposite to each other in a first direction, which can be understood as the thickness direction of the first substrate 310. Among them, the first surface 310a of the first substrate 310 can be used to mount the chip 330. The second substrate 320 includes a bearing surface 320a, which can be used to bear the first substrate 310, and the bearing surface 320a is in contact with the second surface 310b of the first substrate 310. That is to say, the second substrate 320 is borne on the side of the first substrate 310 facing away from the chip 330, and the chip 330, the first substrate 310, and the second substrate 320 are arranged in sequence along the first direction. The heat generated when the chip 330 works can be transferred to the second substrate 320 through the first substrate 310 and dissipated to the outside through the second substrate 320, so as to realize the heat dissipation of the chip 330. The encapsulation body 340 can be used to wrap at least part of the chip 330, the first substrate 310, and the second substrate 320, so as to encapsulate the power module 300 into a whole. Exemplarily, the encapsulation body 340 may expose the surface of the second substrate 320 facing away from the first substrate 310 to utilize the surface of this side of the second substrate 320 to dissipate heat to the outside.

[0055] In some embodiments, the chip 330 may include an insulated gate bipolar transistor (IGBT), a metal-oxide-semiconductor field-effect transistor (MOSFET), or a power transistor, etc. There may be one or more chips 330. One or more chips 330 and other electrical components of the power module 300 form a power conversion circuit. The power module 300 realizes power conversion functions such as DC-AC and DC-DC through the power conversion circuit. Based on this, the power module 300 provided in the embodiments of the present application can be applied to power devices such as inverters, micro-inverters, converters, and motor controllers.

[0056] In some embodiments, the power module 300 further includes a plurality of pins 350. At least a part of each pin 350 is wrapped in the package 340. In one implementation, the first surface 310a of the first substrate 310 includes a plurality of pads. One end of each pin 350 is welded to a corresponding pad respectively, so as to fix each pin 350 on the first surface 310a layer and realize electrical connection with the first surface 310a. The other end of each pin 350 is respectively exposed outside the package 340, so that each pin 350 can be electrically connected to an external device, and further realize the electrical connection between the power module 300 and the external device. Here, the external device may be a circuit board of the power device to which the power module 300 is applied.

[0057] Figure 4 It is a schematic diagram of the partial structure of the power module 300 provided in the embodiments of the present application. Refer to Figure 4As shown, in the embodiment of the present application, the first substrate 310 may be a ceramic substrate. The first substrate 310 includes a ceramic substrate 311 and two metal layers, and the two metal layers are respectively fixed on the opposite side surfaces of the ceramic substrate 311. For the convenience of description, in this embodiment, the metal layers fixed on the two side surfaces of the ceramic substrate 311 are respectively referred to as the first metal layer 312 and the second metal layer 313. Among them, one side surface of the first metal layer 312 facing away from the ceramic substrate 311 may form the first surface 310a of the first substrate 310, and one side surface of the second metal layer 313 facing away from the ceramic substrate 311 may form the second surface 310b of the first substrate 310. In addition to being used for mounting the chip 330, the first surface 310a of the first substrate 310 can also mount electrical components such as inductors, resistors, and capacitors. The chip 330 and these electrical components can be fixed on the first surface 310a through a soldering process. Among them, the chip 330 can be electrically connected to the first metal layer 312 through a wire bonding (WB) process or a clip soldering process, etc. The second surface 310b of the first substrate 310 can be welded and fixed on the bearing surface of the second substrate 320 through a solder 360. In the soldering processes of the above electrical components to the first substrate 310 and the first substrate 310 to the second substrate 320, the solders used include but are not limited to lead solder, lead-free solder, sintered silver, sintered copper, etc.

[0058] In one embodiment, the ceramic substrate 311 can be prepared from materials such as relatively low-cost alumina or aluminum nitride to reduce the overall cost of the power module 300. The first metal layer 312 and the second metal layer 313 can be copper layers respectively, then the first substrate 310 can be a direct bonding copper (DBC) ceramic substrate, or can be an active metal brazing (AMB) ceramic substrate. In other embodiments, the first metal layer 312 and the second metal layer 313 can also be aluminum layers respectively, then the first substrate 310 is a direct bonded aluminum (DBA) ceramic substrate.

[0059] Figure 5 The top view of a second substrate 320 provided by the embodiment of the present application. Referring together to Figure 3 and Figure 5 As shown, in the embodiment of the present application, the projection of the first substrate 310 in the first direction is within the projection range of the bearing surface 320a in the first direction, or it can be understood that the edge of the second substrate 320 extends beyond the edge of the first substrate 310 to improve the heat dissipation performance of the power module 300 by increasing the volume of the second substrate 320. Exemplarily, the second substrate 320 can be made of copper or copper alloy.

[0060] In this embodiment, the bearing surface 320a of the second substrate 320 includes a first region 321 and a second region 322. The contour of the first region 321 is consistent with the edge contour of the second surface 310b of the first substrate 310. The projection of the second surface 310b in the first direction coincides with the projection of the first region 321 in the first direction. That is to say, the second surface 310b can cover the first region 321, and the second region 322 is exposed in the region of the bearing surface that is not covered by the second surface 310b. It should be noted that the coincidence defined in the embodiments of the present application is not limited to a completely coincident relationship, and a relationship that is not completely coincident due to factors such as design tolerances and assembly tolerances is allowed, and a small range of errors is allowed. The second region 322 is arranged around the first region 321. It is easy to understand that the second region 322 is an annular structure, and the second region 322 is exposed in the region not covered by the second surface 310b. Therefore, the package 340 can form contact with the second region 322.

[0061] In a specific implementation, the surface material of the second region 322 includes copper, copper alloy or copper oxide, that is to say, there is no other metal coating or organic coating between the surface of the second region 322 and the package 340. Compared with these coatings, the bonding force between copper, copper alloy or copper oxide and the package 340 is relatively strong. Therefore, when the external environment or the temperature inside the power module 300 changes, the second substrate 320 and the package 340 can still maintain sufficient connection strength under the action of thermal stress, and the first substrate 310 also reduces the risk of cracking due to the reduced thermal stress, thereby significantly improving the structural reliability of the power module 300.

[0062] In addition, the surface material of the first region 321 is not limited. For example, in one implementation, the surface material of the first region 321 can be the same as the surface material of the second region 322; in another implementation, the surface of the first region 321 can have a metal coating.

[0063] In some embodiments, the surface of the second region 322 can be a relatively rough surface. For example, the surface roughness of the second region 322 is greater than the surface roughness of the first region 321. By increasing the surface roughness of the second region 322, the connection strength between the second region 322 and the package 340 can be further improved, and thus the structural reliability of the power module 300 can be enhanced again. Exemplarily, in this embodiment, methods such as laser ablation, physical sandblasting, electroless plating, electroplating, and physical sputtering can be used to roughen the surface of the second region 322.

[0064] In some embodiments, the ring width h of the second region 322 may be greater than or equal to 2 mm. It should be noted that the ring width h of the second region 322 can be understood as the width between the inner ring and the outer ring of the second region 322 along the arrangement direction of the first region 321 and the second region 322. By designing the ring width h of the second region 322 within the above dimension range, the connection strength between the second substrate 320 and the package 340 can be ensured to resist the action of thermal stress inside the power module 300, thereby reducing the risk of delamination between the second substrate 320 and the package 340.

[0065] Figure 6 Another top view of the second substrate 320 provided by the embodiment of the present application. Referring together Figure 3 and Figure 6 As shown, in the embodiment of the present application, the bearing surface 320a of the second substrate 320 further includes a third region 323. The third region 323 can be arranged in a ring shape around the second region 322. That is to say, the first region 321, the second region 322, and the third region 323 are arranged in sequence from the inside to the outside. Among them, the surface material of the third region 323 is not limited. For example, in one implementation, the surface material of the third region 323 can be the same as the surface material of the second region 322; in another implementation, the surface of the third region 323 can have a metal coating. In addition, the surface roughness of the third region 323 can be less than the surface roughness of the second region 322.

[0066] In one implementation, the outer ring of the third region 323 extends to the edge of the bearing surface 320a. That is to say, the third region 323 is the outermost ring region of the bearing surface 320a. The ring width of the third region 323 can be determined according to parameters such as the area of the bearing surface, the area of the first region 321, and the ring width of the second region 322. The present application does not limit this.

[0067] Figure 7 A side view of a second substrate 320 provided by the embodiment of the present application. Referring together Figure 3 and Figure 7 As shown, in the embodiment of the present application, the bearing surface 320a of the second substrate 320 includes a groove 324. The groove 324 is specifically located within the second region 322. Therefore, the surface material of the inner wall of the groove 324 (including the side wall and the bottom wall of the groove 324) can also be copper, copper alloy, or copper oxide. When forming the package 340, the package 340 can be filled in the groove 324. In this way, on the one hand, the connection strength between the second substrate 320 and the package 340 can be improved by using the structural characteristics of the groove 324. On the other hand, since the inner wall surface of the groove 324 is also made of copper, copper alloy, or copper oxide material, it is equivalent to increasing the surface area of the second region 322. Therefore, it helps to further improve the connection strength between the second substrate 320 and the package 340.

[0068] Exemplarily, the groove 324 can be designed as an annular structure. In this way, along the circumferential direction of the second region 322, a high-strength connection can be achieved between any position of the second region 322 and the package 340, and the connection strength at different positions with the package 340 is relatively uniform, thereby reducing the risk that a local area of the second substrate 320 is disconnected from the package 340.

[0069] It should be noted that in the case where the bearing surface 320a of the second substrate 320 includes a third region, the bearing surface 320a can also be provided with a groove 324, and the groove 324 can also be located within the second region 322. Details are not elaborated here.

[0070] Figure 8 Another side view of the second substrate 320 provided by the embodiment of the present application. Referring together to Figure 3 and Figure 8 As shown, in the embodiment of the present application, the second substrate 320 includes a plurality of fins 325. The plurality of fins 325 can be arranged on the surface of the second substrate 320 facing away from the bearing surface 320a, that is, on the surface of the second substrate 320 exposed outside the package 340, and the plurality of fins 325 can be arranged at intervals in sequence. By using these fins 325, the heat dissipation area of the second substrate 320 can be effectively increased, thereby improving the heat exchange efficiency between the second substrate 320 and the external environment, and further contributing to improving the heat dissipation effect on the power module 300.

[0071] Of course, in some other embodiments, the power module 300 may further include a heat sink. In this case, the second substrate 320 may not need to be provided with fins 325. The heat sink is in contact with the surface of the second substrate 320 exposed outside the package 340. The heat transferred from the first substrate 310 to the second substrate 320 can be further transferred from the second substrate 320 to the heat sink, so that the heat dissipation of the power module 300 is achieved by the heat sink. The second substrate 320 and the heat sink can be fixedly connected by welding, sintering, etc. Exemplarily, the heat sink can be a liquid-cooled heat sink or an air-cooled heat sink.

[0072] The embodiment of the present application also provides a method for manufacturing a power module, and the manufacturing method includes the following steps:

[0073] Mount the chip on the first surface of the first substrate;

[0074] Place the first substrate on the first region of the bearing surface of the second substrate, and make the second surface of the first substrate in contact with the bearing surface. The second surface is the surface of the first substrate that is opposite to the first surface along the first direction, and the projection of the first substrate in the first direction coincides with the projection of the first region in the first direction;

[0075] At least part of the chip, the first substrate, and the second substrate are wrapped in the package body, and the package body contacts the second area of the bearing surface. Wherein, the second area is arranged in a ring around the first area, and the surface material of the second area includes copper, copper alloy, or copper oxide.

[0076] For the power module prepared by the above method, there is no other metal coating or organic coating between the surface of the second area and the package body. Since the bonding force between copper, copper alloy, or copper oxide and the package body is relatively strong, when the external environment or the temperature inside the power module changes, the second substrate and the package body can still maintain sufficient connection strength under the action of thermal stress, and the first substrate also reduces the risk of cracking due to the reduced thermal stress, thereby significantly improving the structural reliability of the power module.

[0077] In some embodiments, before fixing the first substrate to the first area of the bearing surface of the second substrate, the preparation method further includes:

[0078] Roughen the surface of the second area so that the surface roughness of the second area is greater than that of the first area. This can further improve the connection strength between the second area and the package body, thus helping to further improve the structural reliability of the power module.

[0079] Among them, the roughening of the surface of the second area can be achieved in various ways. Taking two roughening methods as examples below, two different preparation methods of the power module are described in detail.

[0080] First, refer to Figure 9 as shown in Figure 9 which is a flowchart of a preparation method of a power module provided by an embodiment of the present application. The preparation method includes the following steps:

[0081] Step 1: Install the chip 330 on the first surface 310a of the first substrate 310. Wherein, the first substrate 310 includes, but is not limited to, ceramic substrates of types such as DBC, AMB, DBA, etc. The chip 330 can be welded and fixed to the first surface 310a, and is electrically connected to the first substrate 310 through wire bonding technology or clip welding technology, etc. In addition, in addition to the chip 330, electrical components such as inductors, resistors, capacitors, and pins 350 can also be installed on the first surface of the first substrate. These electrical components and the chip 330 can be fixed on the first surface together through reflow soldering technology.

[0082] Step 2: Roughen the surface of the second region 322 of the bearing surface 320a of the second substrate 320 by a subtractive process, so that the surface roughness of the second region 322 is greater than that of the first region 321. The subtractive process includes laser ablation, chemical etching, physical sandblasting, etc. The second substrate 320 can be made of copper or copper alloy. The surface material of the second region 322 after roughening includes copper, copper alloy or copper oxide.

[0083] Step 3: Place the first substrate 310 on the first region 321 of the bearing surface 320a of the second substrate 320, and make the second surface 310b of the first substrate 310 contact the bearing surface 320a. The first region 321 of the bearing surface 320a is located inside the second region 322, and the second region 322 is arranged around the first region 321. The second surface 310b is the surface of the first substrate 310 that is opposite to the first surface 310a along the first direction, and the projection of the second surface 310b in the first direction coincides with the projection of the first region 321 in the first direction.

[0084] It should be noted that in some implementations, Step 1 and Step 3 can also be interchanged, that is, the first substrate 310 and the second substrate 320 can be assembled first, and then electrical components such as the chip 330 can be installed on the first substrate 310. The present application does not make specific restrictions on this.

[0085] In the above Step 3, placing the first substrate 310 on the first region 321 of the bearing surface 320a of the second substrate 320 can be achieved in two ways. One way is to use a no-clean solder 360 and place the first substrate 310 on the first region 321 of the bearing surface 320a of the second substrate 320 in an atmosphere of formic acid or a nitrogen-hydrogen mixture. Since the surface roughness of the second region 322 of the bearing surface 320a is relatively large, in an atmosphere of formic acid or a nitrogen-hydrogen mixture, the surface of the second region 322 is not wetted by the solder, so the solder 360 will all concentrate on the first region 321, so that local welding of the first substrate 310 and the first region 321 of the bearing surface 320a can be achieved, and the overflow of the solder 360 to the second region 322 and the adverse impact on the subsequent packaging process can be avoided. Another way is to use a flux-cored solder 360 when the surface material of the first region 321 is also copper, copper alloy or copper oxide, and place the first substrate 310 on the first region 321 of the bearing surface 320a of the second substrate 320. This way helps to enhance the welding effect between the first substrate 310 and the second substrate 320, reduce the welding porosity, and thus improve the welding strength between the first substrate 310 and the second substrate 320.

[0086] Step 4: Wrap at least part of the chip 330, the first substrate 310, and the second substrate 320 in the encapsulation body 340, and the encapsulation body 340 contacts the second region 322 of the bearing surface 320a. Since there is no other metal coating or organic coating between the surface of the second region 322 and the encapsulation body 340, a high-strength connection can be achieved between the second substrate 320 and the encapsulation body 340, thereby improving the structural reliability of the power module.

[0087] First, refer to Figure 10 as shown in Figure 10 FIG. 2 is a flowchart of another method for manufacturing a power module provided by an embodiment of the present application. The manufacturing method includes the following steps:

[0088] Step 1: Mount the chip 330 on the first surface 310a of the first substrate 310. The first substrate 310 includes, but is not limited to, ceramic substrates of types such as DBC, AMB, DBA, etc. The chip 330 can be soldered and fixed on the first surface 310a and electrically connected to the first substrate 310 through wire bonding process or clip soldering process, etc. In addition to the chip, electrical components such as inductors, resistors, capacitors, pins 350, etc. can also be mounted on the first surface 310a of the first substrate 310, and these electrical components and the chip 330 can be fixed on the first surface 310a together through the reflow soldering process.

[0089] Step 2: Roughen the surface of the second region 322 of the bearing surface 320a of the second substrate 320 by an additive treatment method so that the surface roughness of the second region 322 is greater than the surface roughness of the first region 321. The additive treatment method includes electroplating, electroless plating, physical sputtering, etc. The second substrate 320 can be made of copper or copper alloy. The surface material of the second region 322 after roughening includes copper, copper alloy or copper oxide.

[0090] Step 3: Place the first substrate 310 on the first region 321 of the bearing surface 320a of the second substrate 320 and make the second surface 310b of the first substrate 310 contact the bearing surface. The first region 321 of the bearing surface 320a is located inside the second region 322, and the second region 322 is arranged around the first region 321. The second surface 310b is the surface of the first substrate 310 that is opposite to the first surface 310a in the first direction, and the projection of the second surface 310b in the first direction coincides with the projection of the first region 321 in the first direction.

[0091] Similar to the previous embodiment, steps 1 and 3 in this embodiment can also be interchanged. In addition, placing the first substrate 310 on the first region 321 of the bearing surface 320a of the second substrate 320 can also be implemented by referring to the two methods in the previous embodiment, and details are not described here.

[0092] Step Four: Wrap at least part of the chip 330, the first substrate 310, and the second substrate 320 within the encapsulation body 340, and the encapsulation body 340 contacts the second region 322 of the bearing surface 320a. Since there is no other metal coating or organic coating between the surface of the second region 322 and the encapsulation body 340, a high-strength connection can be achieved between the second substrate 320 and the encapsulation body 340, thereby improving the structural reliability of the power module.

[0093] The above is only the specific implementation manner of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present application can easily think of changes or substitutions, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A power module, characterized in that, Comprising a first substrate, a second substrate, a chip, and a package, wherein: The first substrate includes a first surface and a second surface disposed opposite to each other in a first direction, and the first surface is used for mounting the chip; The second substrate includes a bearing surface for bearing the first substrate, and the bearing surface is in contact with the second surface; the bearing surface includes a first region and a second region, the projection of the first region in the first direction coincides with the projection of the second surface in the first direction, the second region is arranged in a ring around the first region, and the surface material of the second region includes copper, copper alloy, or copper oxide; The package is used for wrapping at least part of the chip, the first substrate, and the second substrate, and the package is in contact with the second region.

2. The power module according to claim 1, characterized in that, The surface roughness of the second region is greater than that of the first region.

3. The power module according to claim 1 or 2, characterized in that The ring width of the second region is greater than or equal to 2 mm.

4. The power module according to any one of claims 1-3, characterized in that, The bearing surface includes a groove located in the second region, and the inner wall surface material of the groove includes copper, copper alloy, or copper oxide.

5. The power module according to claim 4, wherein The groove is a ring structure.

6. The power module according to any one of claims 1-5, characterized in that, The bearing surface includes a third region arranged in a ring around the second region, and the surface roughness of the third region is less than that of the second region.

7. The power module according to any one of claims 1-6, characterized in that, The second substrate includes a plurality of fins, and the plurality of fins are arranged on the side of the second substrate facing away from the bearing surface and are arranged at intervals in sequence.

8. A preparation method of a power module, characterized in that, Including: Mounting the chip on the first surface of the first substrate; Placing the first substrate on the first region of the bearing surface of the second substrate and making the second surface of the first substrate in contact with the bearing surface, where the second surface is the surface of the first substrate that is opposite to the first surface in the first direction, and the projection of the second surface in the first direction coincides with the projection of the first region in the first direction; Wrapping at least part of the chip, the first substrate, and the second substrate in the package, and the package is in contact with the second region of the bearing surface, where the second region is arranged in a ring around the first region, and the surface material of the second region includes copper, copper alloy, or copper oxide.

9. The preparation method according to claim 8, characterized in that, Before fixing the first substrate to the first region of the bearing surface of the second substrate, the preparation method further includes: Roughening the surface of the second region to make the surface roughness of the second region greater than that of the first region.

10. The preparation method according to claim 9, characterized in that, The roughening of the surface of the second region specifically includes: Roughening the surface of the second region by a subtractive processing method, and the subtractive processing method includes laser ablation, chemical etching, and physical sandblasting.

11. The preparation method according to claim 9, characterized in that, The roughening of the surface of the second region specifically includes: Roughening the surface of the second region by an additive processing method, and the additive processing method includes electroplating, electroless plating, and physical sputtering.

12. The preparation method according to any one of claims 9-11, characterized in that, Placing the first substrate on the first region of the bearing surface of the second substrate specifically includes: Using a solder without flux, in an atmosphere of formic acid or a nitrogen-hydrogen mixture, place the first substrate on a first area of the bearing surface of the second substrate.

13. The preparation method according to any one of claims 9-11, characterized in that, The surface material of the first area includes copper, copper alloy or copper oxide. Placing the first substrate on the first area of the bearing surface of the second substrate specifically includes: Using a solder with flux, place the first substrate on the first area of the bearing surface of the second substrate.

14. A power device, characterized in that, It includes a circuit board and a power module as described in any one of claims 1-7, and the power module is electrically connected to the circuit board.

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