WO2024178963A1

WO2024178963A1 - Power device and power module

Info

Publication number: WO2024178963A1
Application number: PCT/CN2023/120242
Authority: WO
Inventors: 廖小景; 彭浩; 麻斌
Original assignee: 华为数字能源技术有限公司
Priority date: 2023-02-28
Filing date: 2023-09-21
Publication date: 2024-09-06
Also published as: CN116314066A

Abstract

A power device and a power module. The power device comprises: a circuit board (8), a power module (9) and a heat sink (7), the power module (9) being arranged on the circuit board (8), and the heat sink (7) being arranged on the side of the power module (9) facing away from the circuit board (8). The power module (9) comprises: a metal layer-cladded substrate (2), a chip (4), and a plastic package body (1); the metal layer-cladded layer substrate (2) and the chip (4) are stacked, and are plastically packaged in the plastic package body (1); the plastic package body (1) comprises a recessed part (1-1); the recessed part (1-1) is arranged on the side of plastic package body (1) facing away from the heat sink (7), and is located between the surface of the side of the plastic package body (1) facing away from the heat sink (7) and the circuit board (8), so as to form a stress relief space between the circuit board (8) and the plastic package body (1); the projection of the recessed part (1-1) in the thickness direction of the power module (9) covers the projection of the chip (4) in the thickness direction of the power module (9). The power device provided by the present application improves the heat dissipation efficiency and safety thereof.

Description

Power device and power module

This application claims the priority of the Chinese patent application filed with the China Patent Office on February 28, 2023, with application number 202310216979.5 and application name “A Power Device and Power Module”, the entire contents of which are incorporated by reference in this application.

Technical Field

The present application relates to the field of electronic power technology, and in particular to a power device and a power module.

Background Art

In recent years, green energy has been developing day by day and has gradually become the main means to solve the energy crisis. Power modules are widely used as the core components of green energy. Intelligent power modules (IPM: Intelligent Power Module) integrate logic, control, detection and protection circuits. They are easy to use, which not only reduces the size and development time of the system, but also greatly enhances the reliability of the system. It adapts to the development direction of today's power devices and has been widely used in the field of power electronics.

First, when the chip failure in the power module releases stress and causes a short circuit, it is easy to cause the device housing and chip insulation to fail and leak, causing safety problems; second, in order to adapt to high-voltage applications, it is necessary to further increase the withstand voltage of the power module without increasing the module size to be suitable for high-voltage miniaturization scenarios; finally, as the power of the current power module is getting higher and higher, the heat dissipation capacity needs to be improved urgently. The above problems of power modules have seriously restricted the development of the new energy industry, so the industry needs new power modules to continue to promote the progress of the industry.

Summary of the invention

The present application provides a power device and a power module. In the present application, the power module in the power device is improved, so that the structural safety, pressure resistance and heat dissipation of the entire power device are improved. First, a recessed portion is added at the corresponding position of the plastic package below the chip, so that a weak point is formed on the plastic package below the chip, so that when the chip fails and generates stress, it is easier to release from the weak point without damaging the metal-clad substrate above the chip, thereby reducing the short circuit between the heat sink and the chip due to the cracking of the insulating layer in the metal-clad substrate, thereby reducing the serious safety problems caused by the short circuit; secondly, by adding a heat sink with high thermal conductivity between the metal-clad substrate and the chip of the power module, the structural strength between the metal-clad substrate and the chip is improved, so that the chip stress can be more easily released from the plastic package below the chip. The recessed portion of the plastic package body is released, and the heat dissipation performance of the power module is also enhanced; thirdly, a first groove is added to the edge of the plastic package body close to the metal-clad substrate, so that the creepage distance between the pin and the heat sink of the power module is increased without increasing the thickness of the plastic package body, thereby ensuring that the volume of the power module remains unchanged and the manufacturing cost is not increased; finally, a second groove is arranged at the relative position of the first groove in the plastic package body, and the second groove and the recessed portion are both located on the side of the plastic package body away from the metal-clad substrate, and the second groove can reduce the risk of cracks at the corresponding position of the second groove due to the crimping of the heat sink.

To this end, the embodiments of the present application adopt the following technical solutions:

In the first aspect, the embodiment of the present application provides a power device. The power device includes: a circuit board, a power module and a heat sink, the power module is arranged on the circuit board, and the heat sink is arranged on the side of the power module away from the circuit board; the power module includes a metal-clad substrate, a chip and a plastic package; the metal-clad substrate and the chip are stacked and plastic-sealed in the plastic package; the plastic package includes a recessed portion, the recessed portion is arranged on the side of the plastic package away from the heat sink, and is located between the surface of the plastic package away from the heat sink and the circuit board, so as to form a stress release space between the circuit board and the plastic package, and the projection of the recessed portion in the thickness direction of the power module covers the projection of the chip in the thickness direction of the power module.

It can be understood that the recessed portion added in the plastic package provides a relatively weak position for the power module, guiding the stress generated by the chip to be released from the recessed portion without damaging the insulating layer in the metal-clad substrate, thereby reducing the possibility of short circuit between the chip and the heat sink, effectively improving the structural stability and safety of the power module, that is, improving the stability and safety of the power device.

In combination with the first aspect, in a first possible implementation manner, the power module in the power device further includes a heat sink, the heat sink is disposed between the metal-clad substrate and the chip, the thickness of the heat sink in the power module is greater than the thickness of the metal layer in the metal-clad substrate, the projection of the heat sink in the thickness direction of the power module covers the projection of the chip in the thickness direction of the power module, and the area of the heat sink is greater than the area of the chip. Generally, the length and width of the projection of the heat sink in the thickness direction of the power module are respectively greater than the length and width of the projection of the chip in the thickness direction of the power module by more than 1 mm. It can be understood that the added heat sink compensates for the problem that the metal-clad substrate can withstand poor stress due to the thin metal layer, thereby enhancing the structural strength between the metal-clad substrate and the chip in the power module, and the heat sink cooperates with the recessed portion to make it easier for the chip stress to be released from the recessed portion, thereby reducing the occurrence of the problem that the insulating layer in the metal-clad substrate causes a short circuit between the chip and the radiator due to damage, improving the safety of the power module, and thus improving the safety of the power device. At the same time, since the heat sink has high thermal conductivity, various parts of the chip can fully contact the heat sink, maximizing the use of the heat dissipation area, thereby further enhancing the thermal conductivity of the power module, improving the power density of the power module, and thus improving the power output of the power device.

In combination with the first aspect, in a second possible implementation, the power module in the power device further includes a first groove and a pin, the first groove is arranged on a side of the plastic package body close to the radiator, and is located between the plastic package body and the radiator, forming a recessed space facing the radiator, and the first groove can increase the creepage distance between the pin and the radiator; the first part of the pin is arranged in the plastic package body, and generally, the power module is arranged on the circuit board by surface mounting or direct insertion using the second part of the pin. It can be understood that the recessed space formed by the first groove increases the surface wrinkle degree of the plastic package body, extends the surface length of the plastic package body, and thus increases the creepage distance between the pin and the radiator.

In combination with the first aspect, in a third possible implementation, the power module in the power device further includes a second groove, which is arranged on a side of the plastic package body away from the heat sink, and is located between the plastic package body and the circuit board, and extends along the surface of the circuit board to form a flat space facing the pin opening. Generally, the second groove is arranged opposite to the first groove, and the projection of the second groove in the thickness direction of the power module covers the projection of the first groove in the thickness direction of the power module. It can be understood that the second groove added at the relative position of the first groove in the plastic package body can reduce the risk of cracks at the corresponding position of the second groove due to the crimping of the heat sink.

In combination with the first aspect, in a fourth possible implementation, the metal-clad substrate includes a first metal layer, a second metal layer and an insulating layer, the second metal layer is arranged on a side of the insulating layer close to the chip, and the thickness of the heat sink is greater than the thickness of the second metal layer. Generally, the thickness of the heat sink is more than twice the thickness of the second metal layer. Generally, the metal-clad substrate is a copper-clad ceramic substrate (Direct Bond Copper, DBC), an active metal brazed copper substrate (Active metal brazed copper, AMB, such as Al2O3-AMB, Si3N4-AMB or AlN-AMB) or an insulated metal substrate (Insulated metal substrate, IMS), etc. Exemplarily, in order to further improve the power density, the metal-clad substrate can be formed of AlN-DBC, Si3N4-AMB or AlN-AMB with high thermal conductivity, which is not limited here. It can be understood that making the heat sink thicker than the first metal layer can improve the heat dissipation efficiency of the heat sink, while further enhancing the strength between the chip and the metal-clad substrate, reducing the problem of stress caused by chip failure and damaging the insulating layer in the metal-clad substrate, and improving the safety of the power device.

In combination with the first aspect, in a fifth possible implementation, the angle between the side wall of the first groove and the thickness direction of the power module is not zero, the bottom width of the first groove is smaller than the top width of the first groove, and by way of example, the first groove is a trapezoidal structure. Generally, the angle between the side wall of the first groove and the thickness direction of the power module is greater than or equal to 10 degrees, the distance from the top of the first groove to the top of the plastic package, the depth of the first groove, and the bottom width of the first groove are not less than 1 mm, and the first groove may have two side walls or one side wall. It can be understood that the trapezoidal structure is more stable than the vertical structure, and can effectively improve the damage resistance of the power module, thereby improving the reliability and safety of the power equipment.

In combination with the first aspect, in a sixth possible implementation, the first groove is a vertical structure. It can be understood that the vertical structure can effectively increase the surface length of the first groove compared to the trapezoidal structure, thereby increasing the creepage distance between the pin and the heat sink, increasing the voltage that the power module can withstand, and thus increasing the maximum voltage that the power device can withstand.

In combination with the first aspect, in a seventh possible implementation, the side wall of the first groove is provided with at least one stepped tooth. It is understandable that adding stepped teeth can effectively increase the surface length of the first groove, thereby increasing the creepage distance between the pin and the heat sink. At the same time, the more stepped teeth there are, the longer the creepage distance is, and the greater the voltage that the power module can withstand is.

In combination with the first aspect, in an eighth possible implementation, the first groove includes at least one sub-groove. It can be understood that by providing the sub-groove, the surface length of the first groove can be effectively increased, thereby increasing the creepage distance between the pin and the heat sink. At the same time, the more sub-grooves there are, the longer the creepage distance is, and the greater the voltage that the power module can withstand.

In combination with the first aspect, in a ninth possible implementation, the first groove is arranged at an edge of a side of the plastic package body close to the metal-clad substrate. Generally, the first groove can be arranged on one side, two sides, three sides, or four sides of the side of the plastic package body close to the metal-clad substrate.

In combination with the first aspect, in a tenth possible implementation, the power module further includes a bonding wire or an interconnection sheet, the chip is electrically connected to the pin via the bonding wire or the interconnection sheet, and the pin is gull-wing shaped or straight-insert shaped.

In combination with the first aspect, in an eleventh possible implementation, the bottom width of the recess is smaller than the top width of the recess. Generally, the angle between the side wall of the recess and the thickness direction of the power module is greater than or equal to 10 degrees. The length and width of the projection of the recess in the thickness direction of the power module are respectively more than 1 mm larger than the length and width of the projection of the chip in the thickness direction of the power module. At the same time, the depth of the recess is greater than or equal to 0.2 mm, and the distance between the bottom of the recess and the top of the bonding wire or the interconnection sheet is greater than or equal to 0.5 mm. It can be understood that the trapezoidal structure is more stable than the vertical structure, which can effectively improve the damage resistance of the power module, thereby improving the reliability and safety of the power equipment.

In combination with the first aspect, in a twelfth possible implementation, the bottom width of the second groove is smaller than the top width of the second groove. Generally, the angle between the side wall of the second groove and the thickness direction of the power module is greater than or equal to 10 degrees. The depth of the second groove is greater than or equal to 0.2 mm.

In combination with the first aspect, in a thirteenth possible implementation, the heat sink in the power device is arranged on the side of the metal-clad substrate away from the chip by welding or sintering. Generally, a heat dissipation water channel is provided inside the heat sink, and the heat dissipation water channel has a water inlet and a water outlet. The coolant enters the heat dissipation water channel located inside the heat sink through the water inlet, absorbs the heat of the heat sink, and finally flows out from the water outlet to take away all the heat. It can be understood that the heat sink can absorb the heat transferred from the metal-clad substrate, reduce the temperature of the power module, and then reduce the temperature of the power device.

In combination with the first aspect, in a fourteenth possible implementation, a side of the metal-clad substrate facing away from the chip and a side of the plastic package body close to the heat sink are in the same plane. It can be understood that the above arrangement can make the heat sink and the metal layer of the metal-clad substrate fit smoothly, thereby improving the heat dissipation performance of the power module, and thus improving the heat dissipation performance of the power device.

In combination with the first aspect, in a fifteenth possible implementation manner, the metal-clad substrate, the heat sink, and the chip are stacked in sequence by welding or sintering.

In combination with the first aspect, in a sixteenth possible implementation, the heat sink in the power module has high thermal conductivity and high electrical conductivity. The high thermal conductivity can conduct the heat generated by the chip during operation to the heat sink, and the high electrical conductivity can meet the internal current flow requirements of the chip during operation, and provide a channel for the internal current flow. The material of the heat sink includes but is not limited to Cu, CuMo composite materials, diamond, diamond-copper composite materials, Al-SiC composite materials and other materials with high thermal conductivity. It can be understood that the heat sink uses a material with high thermal conductivity and high electrical conductivity, which can not only improve the heat dissipation performance of the chip, but also provide a current channel for the chip, thereby improving the heat dissipation performance of the power module, and then improving the power density of the power module.

In combination with the first aspect, in the seventeenth possible implementation, there are multiple chips in the power module. Generally, the recessed portion can be set according to the number of chips in the power module, and the recessed portion can be provided with at least one sub-region, and each sub-region of the recessed portion corresponds to at least one chip. Generally, the chip includes an insulated gate bipolar transistor chip, an insulated gate bipolar transistor chip and a diode chip sealed chip, a silicon metal oxide semiconductor field effect transistor, a silicon carbide metal oxide semiconductor field effect transistor, a gallium nitride metal oxide semiconductor field effect transistor, and other power semiconductor chips or IC driver chips.

In a second aspect, an embodiment of the present application provides a power module. The power module comprises: a metal-clad substrate, a chip and a plastic package; the metal-clad substrate and the chip are stacked and plastic-sealed in the plastic package; the plastic package comprises a recessed portion; the recessed portion is arranged on a side of the plastic package away from the metal-clad substrate, and the projection of the recessed portion in the thickness direction of the power module covers the projection of the chip in the thickness direction of the power module, so as to form a stress release portion on the plastic package on the side of the chip away from the metal-clad substrate.

It can be understood that the recessed portion added in the plastic package provides a relatively weak position for the power module, guiding the stress generated by the chip to be released from the recessed portion without damaging the insulating layer in the metal-clad substrate, thereby reducing the possibility of short circuit between the chip and the heat sink, and effectively improving the heat dissipation efficiency, structural stability and safety of the power module.

In combination with the second aspect, in a first possible implementation, the thickness of the heat sink in the power module is greater than the thickness of the metal layer in the metal-clad substrate, the projection of the heat sink in the thickness direction of the power module covers the projection of the chip in the thickness direction of the power module, and the area of the heat sink is greater than the area of the chip. Generally, the length and width of the projection of the heat sink in the thickness direction of the power module are respectively greater than the length and width of the projection of the chip in the thickness direction of the power module by more than 1 mm. It can be understood that the added heat sink compensates for the problem that the metal-clad substrate can withstand poor stress due to the thin metal layer, thereby enhancing the structural strength between the metal-clad substrate and the chip in the power module, and the heat sink cooperates with the recessed portion to make it easier for the chip stress to be released from the recessed portion, thereby reducing the problem of the chip and the heat sink being short-circuited due to damage to the insulating layer in the metal-clad substrate, improving the safety of the power module, and thus improving the safety of the power device. At the same time, since the heat sink has high thermal conductivity, various parts of the chip can fully contact the heat sink, maximizing the use of the heat dissipation area, thereby further enhancing the thermal conductivity of the power module, improving the power density of the power module, and thus improving the power output of the power device.

In combination with the second aspect, in a second possible implementation, the power module further includes: a first groove and a pin, the first groove is arranged on a side of the plastic package body close to the metal-clad substrate to form a recessed area on a side of the plastic package body close to the metal-clad substrate, and the first groove can increase the creepage distance between the pin and the heat sink; the first part of the pin is arranged in the plastic package body, and generally, the power module uses the second part of the pin to be arranged on the circuit board by surface mounting or direct insertion. It can be understood that the power module also includes: the recessed area formed by the first groove increases the surface wrinkle degree of the plastic package body and extends the surface length of the plastic package body, so the first groove can increase the creepage distance between the pin and the heat sink.

In combination with the second aspect, in a third possible implementation, the power module further includes: a second groove, the second groove being arranged on a side of the plastic package body away from the heat sink, and extending along a side of the plastic package body away from the metal-clad substrate to form a flat space facing the pin opening. Generally, the second groove is arranged opposite to the first groove, and the projection of the second groove in the thickness direction of the power module covers the projection of the first groove in the thickness direction of the power module. It can be understood that the second groove added at the relative position of the first groove in the plastic package body can reduce the risk of cracks at the corresponding position of the second groove due to the crimping of the heat sink.

In combination with the second aspect, in a fourth possible implementation, the angle between the side wall of the first groove and the thickness direction of the power module is not zero, the bottom width of the first groove is smaller than the top width of the first groove, and the first groove is a trapezoidal structure. Generally, the angle between the side wall of the first groove and the thickness direction of the power module is greater than or equal to 10 degrees, the distance from the top of the first groove to the top of the plastic package, the depth of the first groove, and the bottom width of the first groove are not less than 1 mm, and the first groove may have two side walls or one side wall. It can be understood that the trapezoidal structure is more stable than the vertical structure, and can effectively improve the damage resistance of the power module.

In combination with the second aspect, in a fifth possible implementation, the first groove is a vertical structure. It is understandable that the vertical structure can effectively increase the surface length of the first groove compared to the trapezoidal structure, thereby increasing the creepage distance between the pin and the heat sink and increasing the voltage that the power module can withstand.

In combination with the second aspect, in a sixth possible implementation, the side wall of the first groove is provided with at least one stepped tooth. It is understandable that adding stepped teeth can effectively increase the surface length of the first groove, thereby increasing the creepage distance between the pin and the heat sink. At the same time, the more stepped teeth there are, the longer the creepage distance is, and the greater the voltage that the power module can withstand is.

In combination with the second aspect, in a seventh possible implementation, the first groove includes at least one sub-groove. It can be understood that by providing the sub-groove, the surface length of the first groove can be effectively increased, thereby increasing the creepage distance between the pin and the heat sink. At the same time, the more sub-grooves there are, the longer the creepage distance is, and the greater the voltage that the power module can withstand.

In combination with the second aspect, in an eighth possible implementation, the first groove is arranged at an edge of a side of the plastic package body close to the metal-clad substrate. Generally, the first groove can be arranged on one side, two sides, three sides, or four sides of the side of the plastic package body close to the metal-clad substrate.

In combination with the second aspect, in a ninth possible implementation, the bottom width of the recess is smaller than the top width of the recess. Generally, the angle between the side wall of the recess and the thickness direction of the power module is greater than or equal to 10 degrees. The length and width of the projection of the recess in the thickness direction of the power module are respectively more than 1 mm larger than the length and width of the projection of the chip in the thickness direction of the power module. At the same time, the depth of the recess is greater than or equal to 0.2 mm, and the distance between the bottom of the recess and the top of the bonding wire or the interconnection sheet is greater than or equal to 0.5 mm. It can be understood that the trapezoidal structure is more stable than the vertical structure, and can effectively improve the damage resistance of the power module.

In combination with the second aspect, in a tenth possible implementation manner, the bottom width of the second groove is smaller than the top width of the second groove. Generally, the angle between the side wall of the second groove and the thickness direction of the power module is greater than or equal to 10 degrees. The depth of the second groove is greater than or equal to 0.2 mm.

In combination with the second aspect, in an eleventh possible implementation, there are multiple chips in the power module. Generally, the recessed portion can be set according to the number of chips in the power module, and the recessed portion can be provided with at least one sub-region, and each sub-region of the recessed portion corresponds to at least one chip. Generally, the chip includes an insulated gate bipolar transistor chip, an insulated gate bipolar transistor chip and a diode chip sealed chip, a silicon metal oxide semiconductor field effect transistor, a silicon carbide metal oxide semiconductor field effect transistor, a gallium nitride metal oxide semiconductor field effect transistor, and other power semiconductor chips or IC driver chips.

In combination with the second aspect, in a twelfth possible implementation, a side of the metal-clad substrate facing away from the chip and a side of the plastic package body close to the heat sink are in the same plane. It can be understood that the above arrangement can make the heat sink and the metal layer of the metal-clad substrate fit smoothly, thereby improving the heat dissipation performance of the power module, and thus improving the heat dissipation performance of the power device.

In a third aspect, an embodiment of the present application provides a method for manufacturing a power module, the manufacturing method comprising:

The first step: stacking the metal-clad substrate, the heat sink, and the chip in sequence by welding or sintering;

The second step: plastic encapsulation, using a plastic encapsulation body to seal the metal-clad substrate, the heat sink and the chip, the plastic encapsulation body comprising a recessed portion; the recessed portion is arranged on a side of the plastic encapsulation body away from the metal-clad substrate, and the projection of the recessed portion in the thickness direction of the power module covers the projection of the chip in the thickness direction of the power module.

In combination with the third aspect, in a first possible implementation manner, the plastic package body further includes a first groove, which is arranged on a side of the plastic package body close to the metal-clad substrate, and the first groove can increase the creepage distance between the pins in the power module and the heat sink.

In combination with the third aspect, in a second possible implementation, the plastic packaging body also includes a second groove, which is arranged on a side of the plastic packaging body facing away from the heat sink, and the projection of the second groove in the thickness direction of the power module covers the projection of the first groove in the thickness direction of the power module.

In combination with the third aspect, in a third possible implementation, after the first step, the manufacturing method further includes: electrically connecting the chip to the pins in the power module by welding or sintering using the bonding wires or interconnection sheets.

In combination with the third aspect, in a fourth possible implementation, after the second step, the manufacturing method further includes: stamping the pins to form the pins into a gull-wing shape or a straight-insert shape.

In a fourth aspect, an embodiment of the present application provides a power conversion circuit, characterized in that the power conversion circuit includes: a capacitor and at least one power module, the power module is electrically connected to the capacitor, the capacitor is used to provide voltage to the power module, and the at least one power module is used for AC/DC conversion. Wherein, the power module also includes: a metal-clad substrate, a heat sink, a chip and a plastic package; the metal-clad substrate, the heat sink and the chip are stacked in sequence and plastic-sealed in the plastic package; the plastic package includes a recessed portion; the recessed portion is arranged on the side of the plastic package away from the metal-clad substrate, and the projection of the recessed portion in the thickness direction of the power module covers the projection of the chip in the thickness direction of the power module. It can be understood that the power conversion circuit includes a power module as in the embodiment of the application of the first aspect, and since the power module has good heat dissipation and higher power density, the power conversion efficiency of the motor driver can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of a power device structure provided in Embodiment 1;

FIG2A is a schematic diagram of a power module structure provided in Example 1;

[Corrected 18.10.2023 in accordance with Article 91]
FIG2B is a three-dimensional diagram of a power module structure provided in Example 1;

FIG3 is a schematic diagram of another power module structure provided in Example 1;

FIG4 is a schematic diagram of another power module structure provided in Embodiment 1;

FIG5 is a schematic diagram of another power module structure provided in Embodiment 1;

6A-6C are front views of a power module structure provided in Example 1;

FIG. 7 is a method for manufacturing a power module provided in the second embodiment.

Figure markings: plastic package body-1, recessed portion 1-1, sub-area 1-1-1, first groove 1-2, stepped tooth 1-2-1, sub-groove 1-2-2, second groove 1-3, metal-clad substrate 2, first metal plate 2-1, second metal plate 2-2, insulating layer 2-3, heat sink 3, chip 4, pin 5, bonding wire 6, radiator 7, circuit board 8, power module 9.

DETAILED DESCRIPTION

The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application.

Power modules play an important role in power devices. They are the core components of power devices in the fields of new energy vehicles, smart photovoltaics, etc. When the power device is working, the power module realizes the conversion of AC/DC power by frequently switching between on and off states. However, frequent state switching will bring a lot of heat to the power module, and high temperature will cause the conversion efficiency of the power chip in the power module to decrease or even damage it. At the same time, with the development of the industry towards high-voltage scenarios, power modules are also developing in the direction of high voltage, such as high-voltage fast charging of new energy vehicles and high-voltage power generation of smart photovoltaics. Therefore, it has always been the focus of industry research to timely export the heat generated by the power module under high-voltage working state, reduce the temperature of the power module under working state, increase the withstand voltage value of the power module, and maintain the long-term stable operation of the power module.

There are many problems with current power modules. First of all, in order to improve the heat dissipation efficiency, the industry currently attaches a three-layer structure substrate on the chip before installing a heat sink or radiator, such as a direct bond copper (DBC), an active metal brazed copper (AMB, such as Al2O3-AMB, Si3N4-AMB or AlN-AMB) or an insulated metal substrate (IMS). The upper and lower layers of the three-layer substrate are conductive and thermally conductive materials. The lower layer close to the power chip can provide a channel for the flow of current inside the power chip and can also be used to promptly conduct the heat generated by the power chip. The upper layer close to the radiator can mainly provide protection for the power chip and reduce the impact of external impact on the power chip. The middle layer is an insulating layer, which can prevent the conductive and thermally conductive material of the lower layer from being connected to the radiator, thereby preventing the chip from having problems such as short circuits. However, since the lower layer of the substrate, such as DBC, is generally connected to the power chip using a copper layer, the lower copper layer is relatively thin and has limited effect on improving transient thermal performance, resulting in a small effective heat diffusion area and suboptimal steady-state thermal performance.

Secondly, in order to improve the withstand voltage of the power module, the industry currently increases the creepage distance between the pins of the power chip and the heat sink by increasing the thickness of the plastic package. However, the increase in the thickness of the plastic package will increase the process and cost of the power module. At the same time, the increase in the thickness of the plastic package is not conducive to the heat dissipation of the power module, nor is it conducive to the application of the power module in miniaturization scenarios, thereby limiting the development of the power module.

Finally, since the power module needs to run for a long time and its working environment is also diverse, the power chip in the power module will inevitably fail due to various reasons. For example, the failure of the power chip generates stress, which damages the insulation layer in the metal-clad substrate, causing a short circuit between the power chip and the heat sink, leading to serious safety accidents. Therefore, how to minimize the harm of the failure when the power chip fails and not affect the operation of the entire system has put forward new requirements for the safety and reliability of the power module.

In view of the above problems, the present application provides a novel power device, power module structure, manufacturing method and power conversion circuit. The present application first adds a recessed portion in the plastic package, forms a weak point on the plastic package below the chip, so that the stress generated by the chip failure is more easily released from the weak point without damaging the metal-clad substrate above the chip, reducing the short circuit between the heat sink and the chip caused by the cracking of the insulating layer in the metal-clad substrate, thereby reducing the serious safety problems caused by the short circuit. In accordance with the recessed portion, in order to make up for the disadvantage that the metal layer in the metal-clad substrate can withstand poor stress, a heat sink is arranged between the chip and the metal-clad substrate. Generally, the thickness of the heat sink can be set to be more than one times the thickness of the metal layer in the metal-clad substrate. The heat sink can also improve the stress bearing capacity between the chip and the heat sink, enhance the structural stability of the power module, further guide the chip stress to be released from the recessed portion, and reduce the possibility of short circuit between the chip and the heat sink due to damage to the insulating layer in the heat sink caused by stress generated by chip failure. At the same time, since the heat sink has high thermal and electrical conductivity, it can improve the overall heat dissipation efficiency of the power module.

In order to improve the pressure resistance of the power module without reducing the heat dissipation capacity of the power module, the present application adds a first groove on the edge of the plastic package body close to the metal-clad substrate, so that the creepage distance between the pin and the heat sink of the power module is increased without increasing the thickness of the plastic package body, ensuring that the heat dissipation capacity of the power module is not reduced and the process manufacturing cost is not increased. Finally, in order to further improve the structural stability of the power module, a second groove is set at the relative position of the first groove in the plastic package body. The second groove and the recessed portion are also located on the side of the plastic package body away from the metal-clad substrate. The second groove can reduce the risk of cracks at the corresponding position of the second groove due to the crimping of the heat sink.

The first embodiment provided by the present application is as shown in FIG1 , and the first embodiment of the present application provides a power device, the power device comprising a circuit board 8, a power module 9 and a heat sink 7. The power module 9 is arranged on the circuit board 8 by means of a surface mount through pins 5, and the heat sink 7 is arranged on a side of the power module 9 away from the circuit board 8. The power module 9 comprises a plastic package 1, a metal-clad substrate 2, a heat sink 3 and a chip 4. The heat sink 3 is placed between the metal-clad substrate 2 and the chip 4, wherein the metal-clad substrate 2 includes a first metal layer 2-1, a second metal layer 2-2 and an insulating layer 2-3, and the second metal layer 2-2 and the heat sink 3 are combined together by welding or sintering. Since in the prior art the thickness of the first metal layer 2-1 and the second metal layer 2-2 are relatively thin, the structural strength is insufficient, and the safety requirements of the power device cannot be met, in this application, the thickness of the heat sink 3 is twice the thickness of the second metal layer 2-2, and of course it can be thicker. For example, the thickness of the heat sink 3 is 2.5 times the thickness of the second metal layer 2-2. Therefore, the heat sink 3 can enhance the structural strength between the chip 4 and the metal-clad substrate 2, and when the chip 3 is damaged and generates stress, the protection of the metal-clad substrate 2 is enhanced, and the possibility of damage to the insulating layer 2-3 in the metal-clad substrate 2 is reduced. At the same time, in order to fully utilize the contact area of the heat sink, the length and width of the heat sink 3 are 1 mm larger than the length and width of the chip 4, respectively. Of course, the heat sink 3 can be larger, and the length and width of the heat sink 3 can also be 1.5 mm larger than the length and width of the chip 4, respectively. In addition, the heat sink 3 can also improve the heat dissipation performance of the power module 9, ensuring the heat dissipation performance of the power device. The material of the heat sink 3 is the same as that of the first metal layer 2-1 and the second metal layer 2-2, both of which are Cu, but can also be other materials with high thermal and electrical conductivity such as CuMo composite materials, diamond, diamond-copper composite materials, Al-SiC composite materials. The heat sink 3 has thermal and electrical conductivity properties, which can not only provide heat dissipation for the chip 4, but also provide a current channel for the internal current of the chip 4.

The metal-clad substrate 2, the heat sink 3 and the chip 4 are plastic-encapsulated by the plastic encapsulation body 1. The heat sink 3 can enhance the structural strength between the chip 4 and the metal-clad substrate 2. Adaptively, in order to further protect the insulating layer 2-3 in the metal-clad substrate 2, a recessed portion 1-1 is added to the plastic encapsulation body 1, so that a weak point can be formed on the plastic encapsulation body below the chip 4, so that when the chip 4 fails and generates stress, it is easier to release from the weak point, thereby protecting the insulating layer 2-3. The shape of the recessed portion 1-1 is a regular trapezoid, the bottom width of the recessed portion 1-1 is smaller than the top width of the recessed portion 1-1, and the side wall inclination angle of the recessed portion 1-1 is 10 degrees. Of course, the inclination angle can be larger, for example, the side wall inclination angle of the recessed portion 1-1 is 12 degrees. In order to achieve a better protection effect, the length and width of the bottom of the recessed portion 1-1 are 1.0mm larger than the length and width of the chip 4. Of course, the recessed portion 1-1 can also be larger, for example, the length and width of the bottom of the recessed portion 1-1 are 1.2mm larger than the length and width of the chip 4. In terms of the depth design of the recessed portion 1-1, the depth of the recessed portion 1-1 in Figure 1 is 0.2mm. Of course, it can also be deeper. For example, the depth of the recessed portion 1-1 in Figure 1 is 0.3mm. A safe distance also needs to be ensured between the bottom of the recessed portion 1-1 and the bonding wire 6. The distance between the bottom of the recessed portion 1-1 and the bonding wire 6 is 0.5mm. Of course, the distance can also be larger. The distance between the bottom of the recessed portion 1-1 and the bonding wire 6 is 0.6mm. This structure is more stable than the vertical structure, which can effectively improve the damage resistance of the power module 9 and also improve the safety of the power device. There can be multiple chips 4, and correspondingly, multiple chip areas can also be set, and each chip area corresponds to a recessed portion 1-1. As shown in FIG2A, there are two chips 4 inside the power module 9, and two sub-areas 1-1-1 of the recessed portion 1-1 are set at the bottom of the plastic package 1, corresponding to the two chip areas respectively. As shown in FIG2B, it is a three-dimensional diagram of the power module 9. In order to clearly show the structure of the recessed portion 1-1, in FIG2B, part of the recessed portion 1-1 is set upward, and it can be seen that the recessed portion 1-1 has two sub-areas respectively. It should be pointed out that FIG2A and FIG2B are not in a one-to-one correspondence. The arrangement direction of the sub-areas of the recessed portion 1-1 in FIG2A is opposite to that in FIG2B.

A first groove 1-2 is added to the plastic package 1. The first groove 1-2 is arranged between the plastic package 1 and the heat sink 7 to form a concave space facing the heat sink 7. As shown by the arrow in FIG1 , the surface wrinkle degree of the plastic package 1 is increased, and the surface length of the plastic package 1 is extended. The creepage distance between the pin 5 and the heat sink 7 can be increased, thereby increasing the voltage resistance of the power module 9, and thus improving the voltage resistance of the power device. The first groove 1-2 does not increase the thickness of the plastic package 1, so it will not reduce the heat dissipation capacity of the power module 9, and at the same time, it will not increase the manufacturing cost of the power module 9 due to the increase in the material used in the plastic package 1. As shown in FIG1 , the first groove 1-2 is a trapezoidal structure, and the bottom width of the first groove 1-2 is less than the top width of the first groove 1-2. Here, the side wall inclination angle of the first groove 1-2 is 10 degrees. Of course, the inclination angle can be larger, for example, the side wall inclination angle of the recessed portion 1-1 is 12 degrees. The distance from the top of the first groove 1-2 to the top of the plastic package 1, the depth of the first groove 1-2, and the width of the bottom of the first groove 1-2 are 1.0 mm. Of course, a larger value can also be set. For example, the distance from the top of the first groove 1-2 to the top of the plastic package 1, the depth of the first groove 1-2, and the width of the bottom of the first groove 1-2 are 1.2 mm. The trapezoidal structure is more stable than the vertical structure, which can effectively improve the damage resistance of the power module 9, thereby improving the safety of the power device.

In the first groove 1-2, as shown in FIG3, a step tooth 1-2-1 can be added, and the step tooth 1-2-1 can effectively increase the surface length of the first groove 1-2, thereby further increasing the creepage distance between the pin 5 and the heat sink 7, and ultimately improving the withstand voltage of the power module 9. It can be inferred that the more the number of step teeth 1-2-1, the longer the creepage distance. The present application does not impose a specific restriction on the number of step teeth 1-2-1, which can be one, two, three or four.

In the first groove 1-2, as shown in FIG4, a sub-groove 1-2-2 can be added to the first groove 1-2. Similar to the step teeth 1-2-1, the sub-groove 1-2-2 can also increase the surface length of the first groove 1-2, thereby further increasing the creepage distance between the pin 5 and the heat sink 7, and ultimately improving the withstand voltage of the power module 9. It can be inferred that the more sub-grooves 1-2-2 there are, the longer the creepage distance. The present application does not impose any specific restrictions on the number of sub-grooves 1-2-2, which can be one, two, three, or four.

In some special scenarios, as shown in Figure 5, the first groove 1-2 can also be rectangular, that is, the side wall of the first groove 1-2 can be a vertical structure. Compared with the trapezoidal structure, the rectangular structure can effectively increase the surface length of the first groove, thereby increasing the creepage distance between the pin 5 and the heat sink 7, and can effectively increase the voltage that the power module 9 can withstand.

As shown in Figures 6A-6C, it is a top view of the power module 9, from which it can be seen that the first groove 1-2 can be set on one side, two sides or four sides of the edge of the plastic package body 1 close to the metal-clad substrate 2. It can be set according to the specific scene. This application does not make specific restrictions.

The second groove 1-3 is arranged between the plastic package 1 and the circuit board 8, and extends along the surface of the circuit board 8 to form a flat space facing the pin 5 opening. The second groove 1-3 added to the relative position of the first groove 1-2 in the plastic package 1 can reduce the risk of cracks in the corresponding position of the second groove 1-3 due to the crimping of the heat sink 7. The shape of the second groove 1-3 is also a trapezoid, and the bottom width of the second groove 1-3 is less than the top width of the second groove 1-3. As shown in Figure 1, the angle between the side wall of the second groove 1-3 and the thickness direction of the power module 9 is 10 degrees. Of course, the angle can be larger, for example, the angle between the side wall of the second groove 1-3 and the thickness direction of the power module 9 is 12 degrees. The depth of the second groove 1-3 is 0.2mm, and of course, it can also be deeper, for example, the depth of the second groove 1-3 is 0.3mm. The second groove 1-3 can play a buffering role and protect the power module 9 when the power module 9 is under pressure.

As shown in Figure 1, the power module 9 also includes pins 5 and bonding wires 6, wherein the bonding wires 6 can also be replaced by interconnection sheets. The chip 4 is electrically connected to the pins 5 through the bonding wires 6 or the interconnection sheets. The first part of the pins 5 is arranged inside the plastic package 1, and the second part of the pins 5 is used to connect to the circuit board 8. In the present embodiment, the pins 5 are gull-wing shaped, and of course the pins 5 can also be straight-inserted.

As shown in FIG1 , the heat sink 7 is arranged on the side of the metal-clad substrate 2 away from the chip 4 by welding or sintering. The heat sink 7 and the metal-clad substrate 2 can also be bonded by thermal conductive interface materials such as thermal silicone grease, graphite film, silicone gel, and phase change material. A heat dissipation waterway is provided inside the heat sink 7, and the heat dissipation waterway has a water inlet and a water outlet. The coolant enters the heat dissipation waterway located inside the heat sink 7 from the water inlet, absorbs the heat of the heat sink 7, and finally flows out from the water outlet to take away all the heat. The heat sink 7 can absorb the heat transferred from the metal-clad substrate 2, so that the temperature of the power module 9 is reduced. And it can be seen from FIG1 that the heat sink 7 and the upper surface of the plastic package 1 are in the same plane, so that the heat sink 7 can be flatly bonded with the second metal layer 2-2 of the metal-clad substrate 2, thereby improving the heat dissipation performance of the power module 9. The heat sink 7 has heat dissipation fins, which can increase the heat dissipation area and improve the heat dissipation efficiency of the heat sink 7.

A second embodiment of the present application provides a method for manufacturing a power module, and the method includes:

S1: stacking the metal-clad substrate 2, the heat sink 3, and the chip 4 in sequence by welding or sintering; wherein the thickness of the heat sink 3 is greater than the thickness of the second metal layer 2-2 in the metal-clad substrate 2, and the projection of the heat sink 3 in the thickness direction of the power module covers the projection of the chip 4 in the thickness direction of the power module;

S2: Plastic encapsulation, using a plastic encapsulation body 1 to seal the metal-clad substrate 2, the heat sink 3 and the chip 4, the plastic encapsulation body 1 is provided with a recessed portion 1-1, a first groove 1-2 and a second groove 1-3; wherein the recessed portion 1-1 and the second groove 1-3 are arranged on a side of the plastic encapsulation body 1 away from the metal-clad substrate 2, and the projection of the recessed portion 1-1 in the thickness direction of the power module covers the projection of the chip 4 in the thickness direction of the power module; the first groove 1-2 and the second groove 1-3 are arranged opposite to each other, the first groove 1-2 is arranged on a side of the plastic encapsulation body 1 close to the metal-clad substrate 2, and the projection of the second groove 1-3 in the thickness direction of the power module covers the projection of the first groove 1-2 in the thickness direction of the power module.

The plastic encapsulation material used in the plastic encapsulation body 1 uses a low modulus plastic encapsulation material, which can improve the reliability of the power module. The plastic encapsulation material can be formed by a material with an elastic modulus between 0.5GPa and 20GPa, such as an epoxy plastic encapsulation material, etc., which is not limited here. In the specific implementation, the upper and lower surfaces of the power module can be ground after the plastic encapsulation is completed so that the two sides of the power module are parallel. Of course, grinding is not required according to demand. Exemplarily, after the plastic encapsulation, the pins 5 exposed outside the power module can also be tinned to prevent oxidation of the pins 5 and increase the solderability of the pins 5.

To make a complete power module, there is S11 after S1, and the chip 4 is electrically connected to the pin 5 by welding or sintering using the bonding wire 6 or the interconnection sheet. At the same time, there is S21 after S2, and the pin 5 is stamped to form a gull-wing shape or a straight plug shape.

The third embodiment of the present application provides a power conversion circuit, the power conversion circuit includes a capacitor and at least one power module as in any of the above application embodiments, the power module is electrically connected to the capacitor, the capacitor is used to provide voltage for the power module, and the power conversion circuit is used for AC/DC conversion. In the embodiment of the present application, the structure and working principle of the power module can refer to the description of the above embodiment, and will not be repeated in the embodiment of the present application.

In general, the power conversion circuit provided in the embodiment of the present application includes the power module in any of the above application embodiments. Since the power module adopts the structure in the above embodiment, the heat dissipation performance of the power module is greatly improved, and the pressure resistance is also enhanced. Therefore, the power chip of the same area, the power chip using the power module of the embodiment of the present application can withstand a higher current, thereby obtaining a higher power density, and the power conversion circuit using this power module can also output a higher power and have a higher power conversion efficiency. At the same time, since the power module in the embodiment of the present application is provided with a recessed portion and a second groove, the reliability of the power module is further improved, the working life of the chip 4 is extended, and the reliability of the power conversion circuit in the third embodiment is also improved.

The above are only specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

A power device, characterized in that the power device comprises: a circuit board, a power module and a heat sink, wherein the power module is arranged on the circuit board, and the heat sink is arranged on a side of the power module away from the circuit board;

The power module comprises a metal-clad substrate, a chip and a plastic package, wherein the metal-clad substrate and the chip are stacked and plastic-sealed in the plastic package;

The plastic package body includes a recessed portion, which is arranged on a side of the plastic package body away from the heat sink and is located between a surface of the plastic package body away from the heat sink and a circuit board to form a stress release space between the circuit board and the plastic package body, and the projection of the recessed portion in the thickness direction of the power module covers the projection of the chip in the thickness direction of the power module.
The power device according to claim 1 is characterized in that the power module also includes a heat sink, which is located between the metal-clad substrate and the chip, and the thickness of the heat sink is greater than the thickness of the metal layer in the metal-clad substrate, and the projection of the heat sink in the thickness direction of the power module covers the projection of the chip in the thickness direction of the power module.
The power device according to claim 1 or 2, characterized in that the power module further comprises a first groove and a pin, wherein the first groove is arranged on a side of the plastic package body close to the heat sink and is located between the plastic package body and the heat sink to form a recessed space facing the heat sink, so that the creepage distance between the pin and the heat sink is increased;

The first part of the pin is arranged in the plastic package, and the power module is arranged on the circuit board through the second part of the pin.
The power device according to claims 1-3 is characterized in that the power module also includes a second groove, which is arranged on a side of the plastic package body facing away from the heat sink, and is located between the plastic package body and the circuit board, and extends along the surface of the circuit board to form a flat space facing the pin opening.
The power device according to any one of claims 1 to 4 is characterized in that there are multiple chips in the power module, the recess includes at least one sub-region, and each sub-region of the recess corresponds to at least one chip.
The power device according to any one of claims 1-5 is characterized in that the plastic package body includes a first groove, including: a side wall of the first groove is provided with at least one stepped tooth.
The power device according to any one of claims 1-6 is characterized in that the plastic package body includes a first groove, including: the first groove includes at least one sub-groove.
The power device according to any one of claims 1 to 7, characterized in that the angle between the side wall of the recessed portion and the thickness direction of the power module is not zero, and the bottom width of the recessed portion is smaller than the top width of the recessed portion;

The angle between the side wall of the first groove and the thickness direction of the power module is not zero, and the bottom width of the first groove is smaller than the top width of the first groove;

The angle between the side wall of the second groove and the thickness direction of the power module is not zero, and the bottom width of the second groove is smaller than the top width of the second groove.
A power module, characterized in that the power module comprises a metal-clad substrate, a chip and a plastic package, wherein the metal-clad substrate and the chip are stacked and plastic-sealed in the plastic package;

The plastic package body includes a recessed portion, which is arranged on a side of the plastic package body away from the metal-clad substrate, and the projection of the recessed portion in the thickness direction of the power module covers the projection of the chip in the thickness direction of the power module, so as to form a stress release portion on the plastic package body on the side of the chip away from the metal-clad substrate.
The power module according to any one of claims 1-4 is characterized in that the power module comprises a heat sink, which is arranged between the metal-clad substrate and the chip, the thickness of the heat sink is greater than the thickness of the metal layer in the metal-clad substrate, and the projection of the heat sink in the thickness direction of the power module covers the projection of the chip in the thickness direction of the power module.
The power module according to claim 1, characterized in that the power module further comprises a first groove and a pin, wherein the first groove is arranged on a side of the plastic package body close to the metal-clad substrate to form a recessed area on a side of the plastic package body close to the metal-clad substrate, so that the creepage distance between the pin in the first groove and the heat sink is increased;

The first part of the pin is arranged in the plastic package, and the second part of the pin is used to arrange the power module on a circuit board.
The power module according to claim 1 or 2 is characterized in that the power module also includes a second groove, which is arranged on a side of the plastic package body away from the metal-clad substrate and extends along a side of the plastic package body away from the metal-clad substrate to form a flat space facing the pin opening.
The power module according to any one of claims 1-3 is characterized in that there are multiple chips in the power module, the recess includes at least one sub-region, and each sub-region of the recess corresponds to at least one chip.
The power module according to any one of claims 1-5 is characterized in that the plastic package body includes a first groove, including: a side wall of the first groove is provided with at least one stepped tooth.
The power module according to any one of claims 1 to 6 is characterized in that the plastic package body includes a first groove, including: the first groove includes at least one sub-groove.