Power module and preparation method therefor

Abstract

A power module and a preparation method therefor. The power module comprises a heat dissipation substrate, a circuit board, an auxiliary circuit board, 2N power chips, a lead frame and a strip busbar, wherein the strip busbar comprises an upper busbar and a lower busbar that are stacked and insulated from each other.

Description

Power module and preparation method thereof

[0001] This application claims priority to Chinese patent application No. 202410158925.2, filed on February 4, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present disclosure relates to the technical field of power modules, and in particular to a power module and a preparation method thereof. Background Art

[0003] The rapid development of power semiconductor devices requires power electronic devices to have higher voltages, greater power capacity, and higher reliability. In recent years, silicon carbide (SiC), as a new wide-bandgap semiconductor material, has enabled SiC power devices such as SiC Metal Oxide Semiconductor Field Effect Transistors (SiC MOSFETs) to achieve higher switching frequencies, higher junction temperatures, and lower switching losses. As a result, they have been widely used in power modules, and packaging technology for SiC power devices is also developing rapidly. Summary of the Invention

[0004] In view of the shortcomings of the related art, the present disclosure provides a technical solution for a power module, which reduces the internal parasitic inductance of the power module through a strip busbar design solution with a laminated structure.

[0005] In one aspect, a power module is provided, comprising a circuit board and a strip busbar, wherein the strip busbar is disposed on the circuit board and is used for electrical connection of a power bridge. The strip busbar comprises an upper busbar and a lower busbar that are stacked and insulated from each other.

[0006] In some embodiments, the lower busbar is used to connect the second end of the power chip belonging to the upper bridge in the power bridge with the first end of the power chip belonging to the lower bridge, and the upper busbar is used to connect the second end of the power chip belonging to the lower bridge in the power bridge to the side where the power chip belonging to the upper bridge is located, so as to introduce the power supply of the power bridge from the side where the power chip belonging to the upper bridge is located.

[0007] In some embodiments, the strip busbar further includes an intermediate insulating film, and the lower busbar, the intermediate insulating film, and the upper busbar are stacked in sequence.

[0008] In some embodiments, the thickness of the intermediate insulating film is any value between 0.1 mm and 0.3 mm.

[0009] In some embodiments, the power module also includes the 2N power chips, which are respectively arranged on the circuit board, and the lower busbar includes N independent lower busbar segments, the first ends of the N lower busbar segments are connected one-to-one with the second ends of the N power chips belonging to the upper bridge among the 2N power chips, the second ends of the N lower busbar segments are connected one-to-one with the first ends of the N power chips belonging to the lower bridge among the 2N power chips, and one end of the upper busbar is respectively connected to the second ends of the N power chips belonging to the lower bridge; wherein N is an integer greater than or equal to 1.

[0010] In some embodiments, the power module also includes a lead frame, which is arranged on the circuit board and electrically connected to the circuit board. The first ends of the N power chips belonging to the upper bridge are connected to the positive end of the power supply through the circuit board and the lead frame, and the second ends of the N power chips belonging to the lower bridge are connected to the negative end of the power supply through the upper busbar, the circuit board and the lead frame.

[0011] In some embodiments, the power module further includes an auxiliary circuit board, which is disposed on the circuit board and has at least one driving circuit disposed on the auxiliary circuit board. The control ends of the 2N power chips are respectively connected to the corresponding driving circuits through bonding wires.

[0012] In some embodiments, the power module introduces the driving power of the driving circuit from the side where the N power chips belonging to the lower bridge are located through the lead frame and the circuit board.

[0013] In some embodiments, the power module further includes a heat dissipation substrate, and the circuit board is disposed on the heat dissipation substrate.

[0014] In some embodiments, the power module further includes a plastic package, which covers the circuit board, the at least one auxiliary circuit board, the 2N power chips, a portion of the lead frame and the strip busbar, exposing the external connection portion of the lead frame.

[0015] On the other hand, a method for preparing a power module is also provided, comprising: preparing a heat dissipation substrate, a circuit board, 2M auxiliary circuit boards, 2N power chips, 2N control resistors, a thermistor, a lead frame, and a strip busbar, wherein the circuit board includes an upper bridge circuit board and a lower bridge circuit board. The 2N control resistors are pre-distributed and pre-attached to the copper layers on the auxiliary circuit boards of the 2M auxiliary circuit boards, and the 2N control resistors are electrically connected to the corresponding copper layers on the auxiliary circuit boards by silver sintering. M auxiliary circuit boards of the 2M auxiliary circuit boards and N power chips of the 2N power chips are attached to the copper layer on the circuit board of the upper bridge circuit board, and the lower copper layers of the auxiliary circuit boards of the M auxiliary circuit boards and the first ends of the N power chips are electrically connected to the copper layer on the circuit board of the upper bridge circuit board by silver sintering. Mount the other M auxiliary circuit boards among the 2M auxiliary circuit boards, the other N power chips among the 2N power chips, and the thermistor to the copper layer on the circuit board of the lower bridge circuit board. Use silver sintering to electrically connect the other M auxiliary circuit boards, the other N power chips, and the thermistor to the copper layer on the circuit board of the lower bridge circuit board. Mount the upper bridge circuit board and the lower bridge circuit board to the heat dissipation substrate. Use solder to perform a single soldering operation to solder the lower copper layer of the upper bridge circuit board and the lower copper layer of the lower bridge circuit board to the heat dissipation substrate. After the single soldering operation, connect the drive circuit on the 2M auxiliary circuit boards to the drive power supply via bonding wires. Connect the control terminals of the 2N power chips to predetermined positions on the drive circuit via bonding wires through the 2N control resistors connected in series in a one-to-one correspondence. Wherein, M and N are integers greater than or equal to 1, and M is less than N.

[0016] In some embodiments, the method for preparing the power module further includes: pre-attaching the lead frame and the strip busbar to a fixed position, performing secondary welding with solder, electrically connecting the lead frame to the upper bridge circuit board and the lower bridge circuit board respectively, and electrically connecting the strip busbar to the 2N power chips, the upper bridge circuit board and the lower bridge circuit board respectively. After the secondary welding, a plastic encapsulation material is used for plastic encapsulation to cover the upper bridge circuit board, the lower bridge circuit board, the auxiliary circuit board, the 2N power chips, part of the lead frame and the strip busbar, exposing the external connection part of the lead frame. After the plastic encapsulation is completed, the drive signal pin on the lead frame is bent into a vertical shape by a rib cutting mold to facilitate connection with the drive board.

[0017] The beneficial effects of some embodiments of the present disclosure are as follows: a power module is designed in combination with a circuit board and a strip busbar, the strip busbar includes an upper busbar and a lower busbar that are stacked and insulated from each other, and the electrical connection of the power topology structure in the power bridge is performed through the strip busbar with a stacked structure, which reduces the planar occupied area of ​​the strip busbar and thereby reduces the parasitic inductance inside the module, is conducive to bringing into play the high-frequency characteristics of the power chip in the power module, reduces the harmonics of the output sinusoidal current, and improves the stability of the system.

[0018] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings are incorporated into and constitute a part of the specification, illustrate embodiments consistent with the present disclosure, and together with the specification, are used to explain the principles of the present disclosure. Obviously, the drawings described below are only some embodiments of the present disclosure. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without inventive work. In the drawings:

[0020] FIG1 is a top view of the overall appearance of a power module according to some embodiments;

[0021] FIG2 is a bottom view of the overall appearance of a power module according to some embodiments;

[0022] FIG3 is a diagram of the internal structure of a power module according to some embodiments (before strip busbar welding);

[0023] FIG4 is a diagram of the internal structure of a power module according to some embodiments (after welding of the strip busbar);

[0024] 5A is a top view of an auxiliary circuit board according to some embodiments;

[0025] 5B is a side view of an auxiliary circuit board according to some embodiments;

[0026] FIG6A is a top view of an upper bridge circuit board according to some embodiments;

[0027] FIG6B is a side view of an upper bridge circuit board according to some embodiments;

[0028] FIG7A is a top view of a lower bridge circuit board according to some embodiments;

[0029] FIG7B is a side view of a lower bridge circuit board according to some embodiments;

[0030] FIG8 is a side view of a power module according to some embodiments (hiding auxiliary DBCs and bonding wires);

[0031] FIG9 is a structural diagram of a lead frame according to some embodiments;

[0032] FIG10A is a top view of a strip bus bar according to some embodiments;

[0033] FIG10B is a side view of a strip bus bar according to some embodiments;

[0034] FIG11 is a circuit topology diagram of a power module according to some embodiments;

[0035] FIG12 is a schematic diagram of current flows in upper and lower arms of a power module according to some embodiments; and

[0036] FIG13 is a schematic diagram of current flow in a driving loop of a power module according to some embodiments. DETAILED DESCRIPTION

[0037] The following will describe the embodiments of the present disclosure with reference to the accompanying drawings and preferred embodiments. Those skilled in the art will readily understand the other advantages and benefits of the present disclosure from the contents disclosed in this specification. The present disclosure may also be implemented or applied through different specific embodiments, and the details in this specification may be modified or altered based on different viewpoints and applications without departing from the spirit of the present disclosure. It should be understood that the preferred embodiments are merely illustrative of the present disclosure and are not intended to limit the scope of protection of the present disclosure.

[0038] It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present disclosure. Therefore, the illustrations only show components related to the present disclosure and are not drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component can be changed at will, and the component layout type may also be more complicated.

[0039] In the following description, numerous details are discussed to provide a more thorough explanation of the embodiments of the present disclosure. However, it will be apparent to those skilled in the art that the embodiments of the present disclosure may be practiced without these specific details. In other embodiments, well-known structures and devices are shown in block diagram form rather than in detail to avoid making the embodiments of the present disclosure difficult to understand.

[0040] Related art discloses a full-bridge, direct-water-cooled SiC automotive module. All chips in this module are soldered or silver-pasted to the conductive copper layer of a liner. Conductive copper busbars electrically connect each chip component and the power terminals of each chip component to the corresponding conductive layer of the liner. However, in this solution, all the conductive copper busbars are located on the same plane, which prevents further reduction of the module's internal parasitic inductance. This can easily lead to chip overvoltage breakdown under high-frequency switching conditions.

[0041] Related technologies also disclose a low-inductance plastic-encapsulated module that uses a small liner to independently extract the SiC chip gate drive signal. However, this module does not extract the Kelvin pole drive signal, which still poses the risk of SiC chip oscillation. Furthermore, the module's drive signal is vertically extracted from within the module, making the plastic encapsulation mold design difficult and prone to large-scale glue overflow, affecting product yield.

[0042] In summary, the chip packaging technology of SiC power devices in the related art has at least the following disadvantages: the parasitic inductance parameters inside the module are large, and it is difficult to achieve the high-frequency switching characteristics of the SiC chip.

[0043] In order to solve the above technical problems, some embodiments of the present disclosure respectively provide a power module 100 and a method for preparing the power module 100 . These embodiments will be described in detail below.

[0044] As shown in Figures 1-4, some embodiments of the present disclosure provide a power module 100. Power module 100 includes a heat dissipation substrate 1, a circuit board, an auxiliary circuit board 4, 2N power chips 5, a lead frame 8, and a strip busbar 7. The circuit board is disposed on the heat dissipation substrate 1. The auxiliary circuit board 4 is disposed on the circuit board, and a drive circuit is provided on the auxiliary circuit board 4.

[0045] 2N power chips 5 are mounted on a circuit board. The first ends of the 2N power chips 5 are electrically connected to the circuit board, and the control ends of the 2N power chips 5 are connected to a drive circuit. A lead frame 8 is mounted on the circuit board and electrically connected to the circuit board. One side of the lead frame 8 is connected to a power supply, and the other side of the lead frame 8 is connected to a drive power supply. The drive circuit is connected to the drive power supply.

[0046] As shown in Figures 3, 10A and 10B, the strip busbar 7 is provided on the circuit board, and the strip busbar 7 is used for the electrical connection of the power bridge. The power bridge is a key radio frequency passive component and is vital to modern communications and power systems. The strip busbar 7 includes an upper busbar 7-2 and a lower busbar 7-1 that are stacked and insulated from each other. The first ends of the N power chips 5 belonging to the upper bridge are connected to the positive end of the power supply. The lower busbar 7-1 is connected one-to-one to the second ends of the N power chips 5 belonging to the upper bridge and the first ends of the N power chips 5 belonging to the lower bridge. The second ends of the N power chips 5 belonging to the lower bridge are connected to the negative end of the power supply through the upper busbar 7-2.

[0047] For example, the upper busbar 7-2 is used to connect the second ends of the N power chips 5 belonging to the lower bridge to the side where the N power chips 5 belonging to the upper bridge are located, so as to introduce power supply from the side where the N power chips 5 belonging to the upper bridge are located.

[0048] It should be noted that N is an integer greater than or equal to 1.

[0049] In some embodiments, as shown in FIG3 , the circuit board includes an upper bridge circuit board 2 and a lower bridge circuit board 3 , and the upper bridge circuit board 2 and the lower bridge circuit board 3 are independently disposed on the heat dissipation substrate 1 .

[0050] In some embodiments, as shown in FIG3 , a power module 100 includes 12 power chips 5. The six power chips 5 belonging to the upper bridge are disposed on the upper bridge circuit board 2, and the first ends of the six power chips belonging to the upper bridge are connected to the positive terminal of the power supply through the upper bridge circuit board 2 and the lead frame 8. The six power chips 5 belonging to the lower bridge are disposed on the lower bridge circuit board 3, and the first ends of the six power chips 5 belonging to the lower bridge are led out through the lower bridge circuit board 3 to be connected one-to-one with the second ends of the six power chips 5 belonging to the upper bridge through the lower busbar 7-1.

[0051] In some embodiments, as shown in FIG3 , a power module 100 includes bonding wires 11 and four auxiliary circuit boards 4, two of which are disposed on an upper bridge circuit board 2. The drive circuits on the two auxiliary circuit boards 4 on the upper bridge circuit board 2 are interconnected via bonding wires 11, and the control terminals of the six power chips 5 belonging to the upper bridge are respectively connected to the corresponding drive circuits via bonding wires 11. The other two of the four auxiliary circuit boards 4 are disposed on a lower bridge circuit board 3. The drive circuits on the two auxiliary circuit boards 4 on the lower bridge circuit board 3 are interconnected via bonding wires 11, and the control terminals of the six power chips 5 belonging to the lower bridge are respectively connected to the corresponding drive circuits via bonding wires 11.

[0052] In some embodiments, as shown in Figures 3, 5A, and 5B, the drive circuit is designed to be axisymmetric on the auxiliary circuit board 4. In addition, two auxiliary circuit boards 4 are dispersed on the upper bridge circuit board 2 or the lower bridge circuit board 3, and three power chips 5 are arranged around each auxiliary circuit board 4. The four auxiliary circuit boards 4 are dispersed and symmetrical as a whole.

[0053] In some embodiments, as shown in Figure 3, the power module 100 also includes 12 control resistors 6, and the 12 control resistors 6 are dispersedly arranged on 4 auxiliary circuit boards 4, each auxiliary circuit board 4 is provided with 3 control resistors 6, and the control ends of the 12 power chips 5 are connected to the driving circuit through the one-to-one corresponding 12 control resistors 6.

[0054] In some embodiments, as shown in FIG3-FIG4 , the power module 100 further includes a thermistor 9 , which is disposed on the lower bridge circuit board 3 and is connected in series in a drive loop formed by a drive circuit and a drive power supply.

[0055] In some embodiments, as shown in Figures 3-4, the first end of the power chip 5 is arranged on the back of the power chip 5, the second end and the control end of the power chip 5 are respectively arranged on the front of the power chip 5, and the back of the power chip 5 is in contact with and electrically connected to the circuit board (i.e., the upper bridge circuit board 2 or the lower bridge circuit board 3).

[0056] In some embodiments, as shown in Figures 6A-7B, the upper bridge circuit board 2 and the lower bridge circuit board 3 are both active metal brazing (AMB) ceramic substrates. The upper bridge circuit board 2 or the lower bridge circuit board 3 respectively includes a lower copper layer of the circuit board, a middle ceramic layer of the circuit board, and an upper copper layer of the circuit board, which are stacked in sequence. As shown in Figures 3-4 and 8, the lower copper layer of the circuit board is fixed to the heat dissipation substrate 1 by soldering, the auxiliary circuit board 4 and the 12 power chips 5 are all set on the upper copper layer of the circuit board by silver sintering, the lead frame 8 and the strip busbar 7 are all set on the upper copper layer of the circuit board by soldering, and the 12 power chips 5, the lead frame 8 and the strip busbar 7 are all electrically connected to the upper copper layer of the circuit board.

[0057] In some embodiments, as shown in Figures 6A and 6B , upper circuit board 2 includes an upper circuit board lower copper layer 2-1, an upper circuit board middle ceramic layer 2-2, and an upper circuit board upper copper layer 2-3, which are stacked in sequence. As shown in Figures 7A and 7B , lower circuit board 3 includes a lower circuit board lower copper layer 3-1, a lower circuit board middle ceramic layer 3-2, and an upper circuit board upper copper layer 3-3, which are stacked in sequence.

[0058] In some embodiments, as shown in Figures 5A and 5B, the auxiliary circuit board 4 is a direct bond copper (DBC) ceramic substrate, and the auxiliary circuit board 4 includes an auxiliary circuit board lower copper layer 4-1, an auxiliary circuit board middle ceramic layer 4-2, and an auxiliary circuit board upper copper layer 4-3 stacked in sequence. The auxiliary circuit board lower copper layer 4-1 is fixed on the upper copper layer of the circuit board (i.e., the upper copper layer 2-3 of the upper bridge circuit board and the upper copper layer 3-3 of the lower bridge circuit board) by silver sintering, and the driving circuit is arranged on the upper copper layer 4-3 of the auxiliary circuit board.

[0059] In some embodiments, as shown in Figures 3 and 6A to 7B, for the upper bridge circuit board 2, the copper layer 2-3 on the upper bridge circuit board includes a first region 2A, a second region 2B, and a third region 2C, which are insulated from each other. Two of the four auxiliary circuit boards 4 and the six power chips 5 belonging to the upper bridge are fixed to the first region 2A via silver sintering, and the first ends of the six power chips 5 belonging to the upper bridge are electrically connected to the first region 2A. For the lower bridge circuit board 3, the copper layer 3-3 on the lower bridge circuit board includes a fourth region 3A, a fifth region 3B, and a sixth region 3C, which are insulated from each other. The other two of the four auxiliary circuit boards 4 and the six power chips 5 belonging to the lower bridge are fixed to the fifth region 3B via silver sintering, and the first ends of the six power chips 5 belonging to the lower bridge are electrically connected to the fifth region 3B.

[0060] In some embodiments, as shown in Figures 3-4 and 9, the lead frame 8 includes a first lead frame segment 8A (i.e., the segment in the upper left corner of Figure 9), a second lead frame segment 8B (i.e., the segment in the middle of the left side of Figure 9), a third lead frame segment 8C (i.e., the segment in the lower left corner of Figure 9), a fourth lead frame segment 8D (i.e., the segment in the upper right corner of Figure 9), a fifth lead frame segment 8E (i.e., the segment in the middle of the right side of Figure 9) and a sixth lead frame segment 8F (i.e., the segment in the lower right corner of Figure 9).

[0061] First leadframe segment 8A and third leadframe segment 8C are electrically connected to first region 2A and are each connected to the positive terminal of a power source. Second leadframe segment 8B is connected to second region 2B and is connected to the negative terminal of a power source.

[0062] Fourth leadframe segment 8D is electrically connected to fourth region 3A, which is connected to the driver circuit on lower bridge circuit board 3 via bonding wires 11. Fourth leadframe segment 8D is also connected to a driver power supply. Fifth leadframe segment 8E is electrically connected to fifth region 3B. Sixth leadframe segment 8F is electrically connected to sixth region 3C, which is connected to third region 2C via bonding wires 11. Third region 2C is also connected to the driver circuit on upper bridge circuit board 2 via bonding wires 11. Sixth leadframe segment 8F is also connected to a driver power supply.

[0063] In some embodiments, as shown in Figures 4, 8, 10A, and 10B, the strip busbar 7 further includes an intermediate insulating film 7-3. Along the direction away from the circuit board, the lower busbar 7-1, the intermediate insulating film 7-3, and the upper busbar 7-2 are stacked in sequence. The lower busbar 7-1 includes six independent lower busbar segments. The first ends of the six lower busbar segments are connected to the second ends of the six power chips 5 belonging to the upper bridge in a one-to-one correspondence, and the second ends of the six lower busbar segments are connected to the first ends of the six power chips 5 belonging to the lower bridge in a one-to-one correspondence. The first end of the upper busbar 7-2 is connected to the second ends of the six power chips 5 belonging to the lower bridge, and the second end of the upper busbar 7-2 is connected to the second region 2B.

[0064] In summary, the first ends of the six power chips 5 belonging to the upper bridge are connected to the positive end of the power supply through the first area 2A of the upper bridge circuit board 2, the first lead frame segment 8A and the third lead frame segment 8C, and the second ends of the six power chips belonging to the lower bridge are connected to the negative end of the power supply through the upper busbar 7-2, the second area 2B of the upper bridge circuit board 2 and the second lead frame segment 8B.

[0065] In some embodiments, as shown in FIG1 , the power module 100 further includes a plastic encapsulation body 10, which covers the circuit board, the auxiliary circuit board 4, the twelve power chips 5, a portion of the lead frame 8, and the strip busbars 7, leaving the external connection portion of the lead frame 8 exposed. The plastic encapsulation body 10 isolates the internal circuits of the power module 100 from the outside air, thereby protecting the internal circuits of the power module 100. Furthermore, the encapsulation material (e.g., epoxy molding compound (EMC)) of the plastic encapsulation body 10 has a higher thermal conductivity than traditional potting materials, which helps improve the heat dissipation efficiency of the power chip 5.

[0066] It should be noted that the number of power chips 5 is not limited to 12 as shown in Figures 3 and 4, and can also be 6, 8 or other numbers. It can be flexibly designed and selected according to the required power of the electric drive system, and this disclosure does not limit this.

[0067] That is, the power module 100 includes 2N power chips 5, wherein N power chips 5 of the 2N power chips 5 belong to the upper bridge and are disposed on the upper bridge circuit board 2. The other N power chips 5 of the 2N power chips 5 belong to the lower bridge and are disposed on the lower bridge circuit board 3.

[0068] Correspondingly, the number of auxiliary circuit boards 4 is not limited to 4 as shown in FIG. 3 and FIG. 4 , and may also be other numbers such as 2.

[0069] That is, the power module 100 includes 2M auxiliary circuit boards 4 , M of the 2M auxiliary circuit boards 4 are arranged on the upper bridge circuit board 2 , and the other M of the 2M auxiliary circuit boards 4 are arranged on the lower bridge circuit board 3 .

[0070] The number of control resistors 6 is not limited to 12 as shown in Figures 3 and 4, and can also be 6, 8, or other numbers. However, the number of control resistors 6 is always equal to the number of power chips 5. Similarly, the lower busbar 7-1 includes N independent lower busbar segments.

[0071] It should also be noted that M is an integer greater than or equal to 1, and M is less than N.

[0072] Thus, some embodiments of the present invention disclose a single-sided water-cooled power module 100, the power module 100 mainly includes a heat dissipation substrate 1, a circuit board (including an upper bridge circuit board 2 and a lower bridge circuit board 3), an auxiliary circuit board 4, a power chip 5, a control resistor 6, a strip busbar 7, a lead frame 8, a thermistor 9, a plastic package 10, a bonding wire 11 and other auxiliary materials (such as EMC plastic package, silver film and solder). Based on the packaging of multiple power chips 5, multiple bridge arms are formed as shown in Figure 11.

[0073] The control resistor 6 is pre-attached to the auxiliary circuit board 4 by silver sintering. The power chip 5, the auxiliary circuit board 4, and the thermistor 9 are electrically interconnected with the copper layers on the circuit board (the copper layers 2-3 on the upper bridge circuit board and the copper layers 3-3 on the lower bridge circuit board) by silver sintering. The lower copper layers of the circuit board (the lower copper layers 2-1 on the upper bridge circuit board and the lower copper layers 3-1 on the lower bridge circuit board) are soldered to the heat dissipation substrate 1 by solder (such as PbSn5Ag2.5). The drive signal of the power chip 5 is electrically interconnected with the auxiliary circuit board 4 and the copper layers on the circuit board by bonding wires 11. The strip busbar 7 and the lead frame 8 are electrically interconnected with the power chip 5 and the copper layers on the circuit board by solder (such as SnPb10).

[0074] It is understandable that the power chip 5 is not limited to silicon carbide MOSFET, but can also be a silicon carbide bipolar junction transistor (BJT), silicon carbide insulated-gate bipolar transistor (IGBT) and other silicon carbide power switching tubes, and the present disclosure does not limit this.

[0075] In some embodiments, as shown in Figures 10A and 10B , the strip busbar 7 comprises a three-layer stacked structure. As shown in Figure 12 , the current loop from the positive DC voltage DC+ to the AC voltage AC on the lower busbar 7-1 overlaps with the current loop from the AC voltage AC to the negative DC voltage DC- on the upper busbar 7-2. This reduces the footprint of the strip busbar 7 on the power module 100, thereby reducing the parasitic inductance within the power module 100. This facilitates leveraging the high-frequency characteristics of the power chip 5, thereby reducing harmonics in the output sinusoidal current and improving system stability.

[0076] The distance between the lower busbar 7-1 and the upper busbar 7-2 is any value between 0.1mm and 0.3mm (such as 0.1mm, 0.2mm or 0.3mm). An intermediate insulating film 7-3 (such as a polyimide film (PI film)) is pressed between the lower busbar 7-1 and the upper busbar 7-2. The intermediate insulating film 7-3 is used for insulation between the lower busbar 7-1 and the upper busbar 7-2.

[0077] In addition, the auxiliary circuit board 4 is used to interconnect the drive signals of the power chip 5. Unlike the conventional power module 100 in which the drive circuit is etched on the copper layer of the circuit board, the power module in some embodiments of the present disclosure, through the design of the auxiliary circuit board 4, isolates the power circuit of the power module 100 from the drive circuit, thereby reducing interference between the power circuit and the drive circuit. Furthermore, as shown in FIG13 , the drive circuit etched on the copper layer 4-3 of the auxiliary circuit board of the auxiliary circuit board 4 is symmetrically designed. This not only makes the current of the drive circuit symmetrical, which helps reduce the parasitic inductance parameters of the drive circuit and improve the high-frequency oscillation problem of the power chip 5, but also greatly reduces the complexity of the etching pattern on the copper layer 2-3 on the upper bridge circuit board and the copper layer 3-3 on the lower bridge circuit board, making the upper and lower copper layers of the upper bridge circuit board 2 and the lower bridge circuit board 3 more symmetrical, which helps reduce warping during the production process of the upper bridge circuit board 2 and the lower bridge circuit board 3, thereby improving the packaging yield of the power module 100.

[0078] As shown in Figures 6A to 7B, since the upper bridge circuit board 2 and the lower bridge circuit board 3 do not need to etch the driving circuit, the copper layer 2-3 on the upper bridge circuit board and the copper layer 3-3 on the lower bridge circuit board have better integrity, which facilitates compatibility with power chips of different manufacturers and different sizes.

[0079] In some embodiments, the second end of the power chip 5 (such as the Kelvin source of the silicon carbide MOSFET) and the control end (such as the gate of the silicon carbide MOSFET) are respectively arranged on the front side of the power chip 5. In this way, the second end and the control end of the power chip 5 can be directly connected to the drive circuit through the bonding wire 11, which facilitates reducing the size of the drive circuit and further reduces the parasitic inductance inside the power module 100.

[0080] In addition, the upper bridge circuit board 2 and the lower bridge circuit board 3 are independently designed, which is different from the upper and lower bridge integrated circuit boards of the traditional power module 100. This is beneficial to reducing the stress and strain of welding between the circuit board and the heat dissipation substrate 1, and reducing the warping deformation of the heat dissipation substrate 1 after welding, thereby reducing the overflow of glue in the subsequent plastic packaging process of the power module 100, which is beneficial to improving the packaging yield of the power module 100.

[0081] Based on the above power module 100 , some embodiments of the present disclosure further provide a method for preparing the power module 100 , which includes steps S1 to S6 .

[0082] S1. As shown in FIG3 , prepare a heat dissipation substrate 1, an upper bridge circuit board 2, a lower bridge circuit board 3, 2M auxiliary circuit boards 4, 2N power chips 5, 2N control resistors 6, a thermistor 9, a lead frame 8, and a strip busbar 7.

[0083] S2. As shown in FIG3 , 2N control resistors 6 are pre-distributed and pre-mounted on the copper layers 4 - 3 on the auxiliary circuit boards of 2M auxiliary circuit boards 4 . The 2N control resistors 6 are electrically connected to the corresponding copper layers 4 - 3 on the auxiliary circuit boards by silver sintering.

[0084] S3. As shown in Figure 3, M auxiliary circuit boards 4 among the 2M auxiliary circuit boards 4 and N power chips 5 among the 2N power chips 5 are mounted on the upper copper layer of the upper bridge circuit board 2 (i.e., the upper copper layer 2-3 of the upper bridge circuit board). By using silver sintering, the auxiliary circuit board lower copper layer 4-1 of the M auxiliary circuit boards 4 and the first ends of the N power chips 5 are electrically connected to the upper copper layer of the upper bridge circuit board 2.

[0085] S4. As shown in Figure 3, the other M auxiliary circuit boards 4 among the 2M auxiliary circuit boards 4, the other N power chips 5 among the 2N power chips 5, and the thermistor 9 are mounted on the copper layer on the circuit board of the lower bridge circuit board 3 (i.e., the copper layer 3-3 on the lower bridge circuit board). The other M auxiliary circuit boards 4, the other N power chips 5, and the thermistor 9 are electrically connected to the copper layer on the circuit board of the lower bridge circuit board 3 by silver sintering.

[0086] S5. As shown in Figure 3, mount the upper bridge circuit board 2 and the lower bridge circuit board 3 onto the heat dissipation substrate 1, and use solder (such as PbSn5Ag2.5) to perform one welding, and weld the lower copper layer of the upper bridge circuit board 2 (i.e., the upper bridge circuit board lower copper layer 2-1) and the lower copper layer of the lower bridge circuit board 3 (i.e., the lower bridge circuit board lower copper layer 3-1) to the heat dissipation substrate 1 respectively.

[0087] S6. As shown in FIG3 , after one welding, the driving circuits on the 2M auxiliary circuit boards 4 are connected to the driving power supply through the bonding wires 11, and the control ends of the 2N power chips 5 are connected to the predetermined positions on the driving circuits through the bonding wires 11 through the 2N control resistors 6 connected in series one by one.

[0088] It should be noted that M and N are integers greater than or equal to 1, and M is less than N.

[0089] In some embodiments, after step S6 , the method for preparing the power module 100 further includes steps S7 to S9 .

[0090] S7. As shown in Figure 4, pre-attach the lead frame 8 and the strip busbar 7 to a fixed position, use solder (such as SnPb10) for secondary welding, and electrically connect the lead frame 8 to the upper bridge circuit board 2 and the lower bridge circuit board 3 respectively, and electrically connect the strip busbar 7 to the 2N power chips 5, the upper bridge circuit board 2 and the lower bridge circuit board 3 respectively.

[0091] S8. As shown in Figure 1, after the secondary soldering, a plastic encapsulation compound is used to encapsulate the upper bridge circuit board 2, lower bridge circuit board 3, auxiliary circuit board 4, 2N power chips 5, part of the lead frame 8, and the strip busbar 7, leaving the external connection portion of the lead frame 8 exposed. The plastic encapsulation body 10 isolates the internal circuit of the power module 100 from the external air, thereby protecting the internal circuit of the power module 100. In addition, the thermal conductivity of the plastic encapsulation compound is higher than that of traditional potting materials, which helps to improve the heat dissipation efficiency of the power chip 5.

[0092] S9. As shown in FIG. 1 and FIG. 4 , after the plastic encapsulation is completed, the drive signal pins (i.e., the fourth lead frame segment 8D and the sixth lead frame segment 8F) on the lead frame 8 are bent into a vertical shape through a rib cutting mold to facilitate connection with the drive board.

[0093] The above embodiments are merely illustrative of the principles and effects of the present disclosure and are not intended to limit the present disclosure. Anyone familiar with the technology may modify or change the above embodiments without violating the spirit and scope of the present disclosure. Therefore, all equivalent modifications or changes made by persons of ordinary skill in the art without departing from the spirit and technical ideas disclosed in the present disclosure should still be covered by the claims of the present disclosure. It should be emphasized that the flowcharts and block diagrams in the accompanying drawings illustrate the system architecture, functions, and operations that may be implemented by the system according to various embodiments of the present disclosure.

[0094] The above embodiments are merely illustrative of the principles and effects of the present disclosure and are not intended to limit the present disclosure. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present disclosure. Therefore, any equivalent modifications or alterations made by a person skilled in the art without departing from the spirit and technical concepts disclosed herein shall be covered by the claims of the present disclosure.

Claims

1. A power module, comprising: circuit boards; as well as A strip busbar is arranged on the circuit board and is used for the electrical connection of the power bridge; the strip busbar includes an upper busbar and a lower busbar that are stacked and insulated from each other.

2. The power module according to claim 1, wherein: The lower busbar is used to connect the second end of the power chip belonging to the upper bridge and the first end of the power chip belonging to the lower bridge in the power bridge. The upper busbar is used to connect the second end of the power chip belonging to the lower bridge in the power bridge to the side where the power chip belonging to the upper bridge is located, so as to introduce the power supply of the power bridge from the side where the power chip belonging to the upper bridge is located.

3. The power module according to claim 1 or 2, wherein: The strip busbar further includes an intermediate insulating film, and the lower busbar, the intermediate insulating film and the upper busbar are stacked in sequence.

4. The power module according to claim 3, wherein: The thickness of the intermediate insulating film is any value between 0.1 mm and 0.3 mm.

5. The power module according to any one of claims 1 to 4, further comprising 2N power chips, wherein the 2N power chips are respectively arranged on the circuit board; The lower busbar comprises N independent lower busbar segments. The first ends of the N lower busbar segments are connected one-to-one with the second ends of the N power chips belonging to the upper bridge among the 2N power chips. The second ends of the N lower busbar segments are connected to the first ends of the N power chips belonging to the lower bridge among the 2N power chips in a one-to-one correspondence; One end of the upper busbar is connected to the second ends of the N power chips belonging to the lower bridge respectively; wherein, N is an integer greater than or equal to 1.

6. The power module according to claim 5 further includes a lead frame, which is arranged on the circuit board and electrically connected to the circuit board, the first ends of the N power chips belonging to the upper bridge are connected to the positive end of the power power supply of the power bridge through the circuit board and the lead frame, and the second ends of the N power chips belonging to the lower bridge are connected to the negative end of the power power supply through the upper busbar, the circuit board and the lead frame.

7. The power module according to claim 6 further includes an auxiliary circuit board, which is arranged on the circuit board and has a drive circuit provided on the auxiliary circuit board, and the control terminals of the 2N power chips are respectively connected to the corresponding drive circuits through bonding wires.

8. The power module according to claim 7, wherein: The driving power supply of the driving circuit is introduced from the side where the N power chips belonging to the lower bridge are located through the lead frame and the circuit board. 9 . The power module according to claim 8 , further comprising a heat dissipation substrate, wherein the circuit board is disposed on the heat dissipation substrate.

10. The power module according to claim 8 or 9, further comprising a plastic package, wherein the plastic package covers the circuit board, the auxiliary circuit board, the 2N power chips, a portion of the lead frame and the strip busbar, exposing an external connection portion of the lead frame.

11. A method for preparing a power module, comprising: Prepare a heat dissipation substrate, a circuit board, 2M auxiliary circuit boards, 2N power chips, 2N control resistors, a thermistor, a lead frame, and a strip busbar. The circuit board includes an upper bridge circuit board and a lower bridge circuit board. Pre-mounting the 2N control resistors on the copper layers of the auxiliary circuit boards of the 2M auxiliary circuit boards, and electrically connecting the 2N control resistors to the corresponding copper layers on the auxiliary circuit boards by silver sintering; Mounting M of the 2M auxiliary circuit boards and N of the 2N power chips to the upper copper layer of the upper bridge circuit board, and electrically connecting the lower copper layers of the M auxiliary circuit boards and the first ends of the N power chips to the upper copper layer of the upper bridge circuit board by silver sintering; Mounting the other M auxiliary circuit boards among the 2M auxiliary circuit boards, the other N power chips among the 2N power chips, and the thermistor to the copper layer on the circuit board of the lower bridge circuit board, and electrically connecting the other M auxiliary circuit boards, the other N power chips, and the thermistor to the copper layer on the circuit board of the lower bridge circuit board by silver sintering; Mounting the upper bridge circuit board and the lower bridge circuit board on the heat dissipation substrate, performing one-time soldering with solder, and soldering the lower copper layer of the upper bridge circuit board and the lower copper layer of the lower bridge circuit board to the heat dissipation substrate respectively; After one welding operation, the driving circuits on the 2M auxiliary circuit boards are connected to the driving power supply via bonding wires, and the control terminals of the 2N power chips are connected to predetermined positions on the driving circuits via bonding wires through the 2N control resistors connected in series in a one-to-one correspondence. Wherein, M and N are integers greater than or equal to 1, and M is less than N.

12. The method for preparing a power module according to claim 11, further comprising: Pre-attaching the lead frame and the strip busbar to fixed positions, performing secondary soldering with solder, electrically connecting the lead frame to the upper bridge circuit board and the lower bridge circuit board respectively, and electrically connecting the strip busbar to the 2N power chips, the upper bridge circuit board, and the lower bridge circuit board respectively; After the secondary welding, a plastic encapsulation compound is used to encapsulate the upper bridge circuit board, the lower bridge circuit board, the auxiliary circuit board, the 2N power chips, a portion of the lead frame, and the strip busbar, exposing the external connection portion of the lead frame; After the plastic packaging is completed, the driving signal pins on the lead frame are bent into a vertical shape through a rib cutting molding die to facilitate connection with the driving board.

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