Laminated power module and preparation method thereof

Abstract

The invention discloses a stacked power module and a preparation method, and relates to the field of semiconductors, the power module comprises a metal radiator and circuit boards which are sequentially stacked above the metal radiator, and at least more than two layers of circuit boards are subjected to function conduction through arrangement of conductive columns and conductive through holes. A, the conductive columns are fixed at the input end and / or the output end of the bottom layer circuit board so as to meet the function conduction between the upper circuit board and the lower circuit board; b, the conductive through holes are correspondingly arranged right above the conductive columns, and the loop length is the shortest after the function is conducted; and c, vertically fixing the welded conductive columns on the bottom layer circuit board through a mold so as to meet the requirement that the upper ends of the conductive columns can be correspondingly assembled into the conductive through holes. According to the invention, innovative conductive column direct connection structure design and positioning design are adopted, and the problems of large size, poor integration level, tedious preparation process, difficulty in accurate assembly, relatively long loop, relatively large parasitic inductance, relatively high voltage peak and relatively large electromagnetic radiation of the existing module are solved.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a stacked power module and a preparation method thereof, which are particularly suitable for use in welding machines. Background Art

[0002] A power module is a functionally integrated module composed of semiconductor devices. Depending on the semiconductor components encapsulated, power modules can implement various functions, such as rectification and inversion. Due to their convenient switching capabilities and stable and reliable operation, they are widely used in various inverter power supply scenarios requiring power conversion, such as welding machines.

[0003] In the existing technology, there are many technologies related to power modules, including: For example, publication number CN119383933A discloses an inverter power supply that, by directly attaching a power module to the copper-plated layer of an aluminum radiator, not only utilizes the aluminum radiator as the power module's load output but also effectively improves its heat dissipation. Typically, when the power circuit in a power module is operating, a separate circuit board is required to configure a driver circuit to control and drive the power circuit's normal operation. However, in actual applications, the existing circuit board carrying the driver circuit is mounted on the side of the aluminum radiator, and the two are connected by welding metal wires. A careful analysis revealed that, because the driver circuit remains part of the power module, the inverter power supply fails to achieve further integration between the circuit board carrying the driver circuit and the power module, resulting in a larger overall volume and a longer loop length for the power module. This not only results in poor integration of the power module, but also leads to larger parasitic inductance, higher voltage spikes, and greater electromagnetic radiation in the power module's loop. Furthermore, the connection between the two is made by welding metal wires. Because the metal wires are soft and thin and the solder joints are small, alignment between the metal wires and the solder joints is difficult, making mechanized intelligent welding inconvenient and prone to cold solder joints and overlay welds.

[0004] For example, the document with publication number CN113346713A discloses a discrete device and a power module package, which includes a cooler, a power unit and a driving unit arranged in parallel in three layers of lower, middle and upper. The discrete device in the power unit includes a positive power terminal, a negative power terminal, a control signal terminal and a protective power terminal. The positive power terminal and the negative power terminal are welded on the power unit circuit substrate. The control signal terminal and the protective power terminal are insulated through the insulating hole of the power unit circuit substrate and then welded on the driving circuit board of the driving unit. The package discloses a scheme in which the chip on one layer of circuit board is welded with another circuit board through a pin. However, after careful analysis, it is found that the technology is to package each discrete device (chip) first and then integrate with other circuits into one. It needs to package each discrete device separately first, and then integrate the whole through the circuit board. This makes the power module a device-level packaging and integration structure, which has the problems of complex structure and complicated preparation process. In addition, since each discrete device involves multiple pin terminals, and each discrete device is connected with the signal connection terminal on the driving unit through the pin terminal, not only the circuit position layout on each unit is limited, but also the circuit loop is long, which leads to the problems of large volume, large loop parasitic inductance, high voltage spike and large electromagnetic radiation.

[0005] In addition, the prior art also discloses a connection structure between two circuit boards using a plug and a socket, such as the document with publication number CN215268898U which discloses a plug-in PCB board structure. However, this kind of connection structure needs to process plug and socket on two circuit boards respectively, and in order to facilitate installation, a support seat for adapting the plug pin and the socket hole on the two circuit boards needs to be designed between the two circuit boards. Therefore, the plug and the socket have the problems of complex preparation process on the circuit board, high material cost and production cost. In addition, the socket has a large volume, the plug has a small diameter and is easy to bend and deform, which also has the problems of large area occupation on the circuit board, difficulty in making the power module more miniaturized and difficulty in assembly.

[0006] However, the prior art does not find a direct connection method between the circuit boards through the column and the through hole. Therefore, it is necessary to provide a new technology to solve the above technical problems. SUMMARY

[0007] The present invention addresses the technical problems of existing power modules, such as large size, poor integration, cumbersome preparation process, difficulty in accurately implementing mechanized intelligent welding, poor welding effect, and large parasitic inductance, high voltage spikes, and large electromagnetic radiation caused by long loops. The present invention provides a stacked power module and preparation method. First, the present invention adopts an innovative conductive column direct connection structure design based on the stacked structure, which can uniformly utilize conductive columns and conductive through-holes to achieve functional conductivity between the upper and lower circuit boards, enabling chip-level integration of the power module. This not only effectively simplifies the structure of the power module and improves its integration, but also reduces the number of pin terminals and maximizes the shortening of the loop length, thereby effectively reducing the parasitic inductance, voltage spikes, and electromagnetic radiation of the power module loop. Secondly, the present invention can keep several conductive columns vertical throughout the assembly and sintering process through mold positioning, so that each conductive column can be smoothly assembled into each conductive through-hole at the same time, avoiding the problem of both being unable to be assembled smoothly due to the bending of any conductive column. In addition, during assembly, it is also convenient to use mechanical intelligent welding to avoid cold welding and overlay welding, thereby improving the stability and reliability of welding.

[0008] To achieve the above object, the technical solution adopted by the present invention is as follows: A stacked power module includes a metal heat sink with circuit boards stacked on top. At least two layers of circuit boards are connected by a number of conductive posts and conductive through-holes. The modules must meet the following technical requirements: a. Fix the lower end of the conductive pillar to the input and / or output end of the bottom circuit board, and the minimum spacing between adjacent conductive pillars is 2.2mm to ensure functional conductivity between the upper and lower circuit boards; b. The conductive through holes are set just above the conductive posts, and the loop length is the shortest after the upper and lower circuit boards are functionally connected; c. Limit the bottom circuit board on the lower mold, and apply solder paste to the position of the corresponding fixed conductive column on the bottom circuit board; use a pin insertion machine to automatically insert the conductive column into the positioning socket of the upper mold, and use a detachable limit baffle to limit the lower end of the conductive column; use the positioning pins and positioning holes to close the upper and lower molds, and after closing the molds, pull out the limit baffle to make the lower ends of the conductive columns fall into the solder paste application positions on the bottom circuit board respectively, and send the mold into the welding equipment. After welding, the conductive columns are vertically fixed on the bottom circuit board to ensure that the upper ends of each conductive column can be assembled into each conductive through-hole.

[0009] The conductive column is a T-shaped structure including a cylindrical rod and a cylindrical cap. The cylindrical cap is welded and fixed on the bottom circuit board, and the cylindrical rod is welded and fixed in the conductive through hole. The diameter of the cylindrical rod is 1-1.2 mm.

[0010] The bottom circuit board is provided with a power circuit, and the upper circuit board is provided with a functional circuit, a transfer wire and a plurality of power terminals. The functional circuit and the power terminals are respectively connected to the conductive through-holes through the transfer wires; the conductive column is provided at the input end and / or the output end of the power circuit. After the power circuit and the conductive column are integrally encapsulated on the bottom circuit board, they are connected to the functional circuit through the conductive through-holes and the transfer wires.

[0011] The shortest loop length after the upper and lower circuit boards are functionally connected means that the length of the transfer wires between the conductive through-holes and the functional circuits and between the conductive through-holes and the power terminals are the shortest.

[0012] The power circuit includes a three-phase rectifier circuit, an inverter circuit and a secondary rectifier circuit. The power input end of the three-phase rectifier circuit is electrically connected to some power terminals through conductive columns and conductive through-holes, the power output end of the three-phase rectifier circuit is electrically connected to some power terminals through conductive columns and conductive through-holes, the signal input end of the inverter circuit is electrically connected to the drive circuit through conductive columns and conductive through-holes, the power output end of the inverter circuit is electrically connected to some power terminals through conductive columns and conductive through-holes, and the power input end of the secondary rectifier circuit is electrically connected to some power terminals through conductive columns and conductive through-holes.

[0013] The bottom circuit board is a combination structure of multiple DBC circuit boards and a copper-plated layer. The copper-plated layer is coated on a metal radiator, and the DBC circuit board is welded and fixed on the copper-plated layer. The three-phase rectifier circuit and the inverter circuit are respectively arranged at the lower and upper parts of a DBC circuit board, and the secondary rectifier circuit is respectively arranged on the copper-plated layer and the remaining DBC circuit boards.

[0014] The conductive columns at the power input end of the three-phase rectifier circuit are located at the lower part of the DBC circuit board and are arranged in a matrix. The conductive columns at the power output end of the three-phase rectifier circuit are respectively located in the middle of the right side and the upper left side of the DBC circuit board. The conductive columns at the signal input end of the inverter circuit are respectively located in the middle upper left side and the middle upper right side of the DBC circuit board. The conductive column at the power output end of the inverter circuit is located in the middle of the upper part of the DBC circuit board. The conductive columns at the power input end of the secondary rectifier circuit are evenly arranged on multiple DBC circuit boards.

[0015] The functional circuit includes a drive circuit, an IGBT resistor-capacitor absorption circuit and an FRD resistor-capacitor absorption circuit. The IGBT resistor-capacitor absorption circuit is connected in parallel with the three-phase rectifier circuit through conductive columns and conductive through-holes. The FRD resistor-capacitor absorption circuit is connected in parallel with the secondary rectifier circuit through conductive columns and conductive through-holes. The IGBT resistor-capacitor absorption circuit and the three-phase rectifier circuit share the conductive columns at the power output end of the three-phase rectifier circuit and the conductive columns at the power output end of the inverter circuit. The conductive columns between the FRD resistor-capacitor absorption circuit and the secondary rectifier circuit are symmetrically arranged on the copper-plated layer.

[0016] The upper circuit board includes a PCB circuit board or two PCB circuit boards stacked above the bottom circuit board. When the upper circuit board includes a PCB circuit board, the drive circuit, the IGBT resistor-capacitor absorption circuit and the FRD resistor-capacitor absorption circuit are all arranged on the PCB circuit board; when the upper circuit board includes two PCB circuit boards, the drive circuit is arranged on one of the PCB circuit boards, and the IGBT resistor-capacitor absorption circuit, the FRD resistor-capacitor absorption circuit and the power supply terminal are all arranged on the other PCB circuit board, and the PCB circuit board on which the drive circuit is arranged is located above the other PCB circuit board.

[0017] The IGBT resistance-capacitance absorption circuit and the FRD resistance-capacitance absorption circuit are respectively arranged on two PCB circuit boards. The two PCB circuit boards have the same height and are respectively located above the inverter circuit and the secondary rectifier circuit.

[0018] An insulating shell is fixed on the metal radiator, and the bottom circuit board, power circuit and conductive column are all encapsulated as a whole in the insulating shell through a vacuum potting process. Positioning grooves for fixing power terminals are respectively opened on both sides of the upper part of the insulating shell, and countersunk holes are provided in the positioning grooves, and nuts are provided in the countersunk holes; the power terminals are L-shaped copper bars welded and fixed to the upper circuit board, one end of each L-shaped copper bar is respectively arranged on both sides of the upper circuit board, and the other end of each L-shaped copper bar is fixed in the positioning groove by bolts and nuts and electrically connected to external devices.

[0019] A method for preparing a stacked power module includes designing a circuit board to be stacked on a metal heat sink based on the power module's conduction and heat dissipation requirements, and determining that the layout of conductive columns and conductive vias between the circuit boards should meet the following requirements: a. The lower end of the conductive pillar is fixed to the input and / or output end of the bottom circuit board, and the minimum spacing between adjacent conductive pillars is 2.2mm to ensure functional conductivity between the upper and lower circuit boards; b. The conductive through-holes are set just above the conductive posts to ensure the shortest loop length after the upper and lower circuit boards are connected; Based on the above requirements, the preparation method comprises the following steps: Step 1: Position the bottom PCB on the lower die, apply solder paste to the locations corresponding to the fixed conductive posts and the fixed power circuit on the bottom PCB, and place the power circuit on the corresponding solder paste; use a pin insertion machine to automatically insert the conductive posts into the positioning holes of the upper die, and use a detachable limit baffle to limit the lower end of the conductive posts; Step 2: Use the positioning pins and positioning holes to close the upper and lower molds. After closing the molds, pull out the limit baffles so that the lower ends of the conductive pillars fall into the corresponding solder paste positions on the bottom circuit board where the conductive pillars are fixed; Step 3: Place the mold into the welding equipment and use a vacuum reflow process to weld the power circuit and the conductive column to the bottom circuit board. After welding is completed, open the mold and remove the bottom circuit board. Step 4: Coat the metal heat sink with a copper layer, solder the bottom circuit board to the copper layer, then fix the insulating housing on the copper layer, and use a vacuum potting process to encapsulate the bottom circuit board, power circuit, and the lower end of the conductive column in the insulating housing; Step 5: Set up a correction plate with a number of conical countersunk correction holes corresponding to the conductive posts. Insert the conductive posts into the conical countersunk correction holes for correction, so that the conductive posts always remain vertical. Step 6: Setting up an upper circuit board. The upper circuit board is provided with functional circuits, transfer wires, and conductive through-holes corresponding to the conductive posts. The functional circuits are connected to the conductive through-holes via the transfer wires. The upper circuit board is moved by an intelligent manipulator so that the conductive through-holes correspond to the conductive posts. The upper circuit board is controlled to move downward until the upper ends of all the conductive posts are respectively fitted into the corresponding conductive through-holes, thereby achieving the upper and lower stacking of the circuit boards. Step 7: Solder the conductive posts and conductive through-holes to enable functional conduction between the upper and lower circuit boards through the conductive posts and conductive through-holes, thus completing the preparation.

[0020] In step 3, the vacuum reflow soldering process conditions are: preheating 100-150°C, heating rate 2-3°C / s, solder reflow temperature 217-227°C, maintaining oxygen content <5ppm during soldering, and holding for 30-90 seconds after soldering; In step 4, the specific process of the vacuum potting process is as follows: place the insulating shell and the bottom circuit board into the potting mold, evacuate to -0.1Mpa and exhaust the air, then inject silicone gel with a hardness of Shore 00-30 to fill the gap in the insulating shell and cover the bottom circuit board, power circuit and the lower end of the conductive column, and complete the vacuum potting after curing.

[0021] Compared with the prior art, the present invention has the following beneficial effects: 1. The power module provided by the present invention utilizes a stacked circuit board structure and an innovative direct-connection conductive post structure design. By meeting technical requirements a and b, the positions of the conductive posts, conductive vias, and related circuits can be arranged based on the principle of minimizing loop length after functional conduction to achieve functional conduction. During implementation, the layout of the circuits and devices can be completed in advance, and then the conductive posts can be uniformly led out. This allows the power module to achieve chip-level integration, effectively reducing the size of the power module and improving its integration. Furthermore, based on this chip-level integrated power module, the conductive posts can be led out after the overall layout, thereby reducing the number of pin terminals and simplifying the structure and manufacturing process of the power module. Furthermore, the minimum spacing between adjacent conductive posts is 2.2 mm. This not only helps ensure their insulation while meeting safety spacing requirements, but also facilitates effective fixing of the conductive posts to the circuit board, and further helps further reduce the overall size of the power module. Conversely, a spacing greater than 2.2 mm will increase the size of the power module. A spacing less than 2.2 mm will result in an inability to ensure insulation and inconvenience in mechanized manufacturing. Accordingly, since the volume of the power module is reduced and the loop length is minimized, the parasitic inductance, voltage spikes and electromagnetic radiation of the power module can also be fundamentally reduced.

[0022] It should be noted that, due to the large number of conductive posts and their generally small diameters, they are often prone to bending during welding and assembly, and as long as one conductive post is bent, assembly failure will occur. To this end, the present invention, through technical requirement c, can ensure that the conductive posts remain vertical during welding and assembly, preventing them from bending, thereby enabling multiple conductive posts to be assembled into each conductive through-hole at the same time, thereby ensuring the accuracy of the assembly of the conductive posts and the conductive through-holes, and facilitating improved assembly efficiency. Furthermore, through the mutual coordination of the various technical requirements, on the one hand, the hard contact between the posts and the holes is easier to weld, and when preparing the power module, it is also convenient to automatically align the conductive through-holes with the conductive posts from top to bottom for installation and welding by mechanical means, which is both convenient for mechanical intelligent operation and accurate positioning, and can also avoid the occurrence of cold welding and overlay welding, reducing the problem of abnormal resistance increase caused by poor contact, ensuring the stability of circuit conduction, extending the service life of the power module, and improving production efficiency. On the other hand, the fixed structure of the conductive posts and the conductive through-holes can also play a stable supporting role for the upper circuit board, further enhancing the stability and reliability of the connection between the circuit boards, and reducing the risk of connection failure, ensuring the stability of the circuit conduction. In addition, the dependence on a large number of metal wires is reduced, and the complex process and production costs caused by bonding metal wires are reduced.

[0023] 2. While minimizing loop length and size, this invention also helps reduce electromagnetic radiation from high-frequency signals during transmission. The conductive posts and circuit boards themselves function as a shielding structure, inherently reducing signal interference between circuit boards. This minimizes the electromagnetic impact of the power module on surrounding circuits during operation, improving the electromagnetic compatibility of the entire device and reducing the need for additional shielding measures.

[0024] 3. The present invention utilizes a T-shaped conductive post comprising a cylindrical rod and a cylindrical cap. The cylindrical cap increases the contact area between the conductive post and the underlying circuit board, enhancing the weld strength between the conductive post and the underlying circuit board. The cylindrical rod, which mates with the conductive via, forms a stable and reliable weld, ensuring stable and reliable circuit transmission. The conductive post has a diameter range of 1-1.2 mm, ensuring sufficient structural strength for easy assembly with the conductive via while maintaining reasonable cost.

[0025] 4. This invention minimizes the length of the transfer wires between the conductive vias and the functional circuits, and between the conductive vias and the power terminals. This results in a power module with the shortest possible loop length after functional conduction, which not only reduces the size of the power module but also shortens the loop length. Furthermore, the coordination of the power terminals, conductive posts, and conductive vias facilitates the construction of a highly efficient current transmission path with the shortest possible loop length.

[0026] 5. In the present invention, the three-phase rectifier circuit, inverter circuit, and secondary rectifier circuit on the bottom circuit board can be specifically connected to the driver circuit, IGBT RC absorption circuit, and FRD RC absorption circuit on the upper circuit board through conductive posts and conductive through-holes. Furthermore, the IGBT RC absorption circuit and the three-phase rectifier circuit can share the conductive posts at the power output of the three-phase rectifier circuit and the power output of the inverter circuit, which helps reduce the number of conductive posts and make the power module smaller and the loop length minimized. The parallel design of the IGBT RC absorption circuit and FRD RC absorption circuit with the inverter circuit and the secondary rectifier circuit, respectively, helps to accurately suppress voltage fluctuations in the circuit and improve power conversion efficiency.

[0027] 6. By arranging the conductive pillars in separate zones on the bottom circuit board, the present invention can reduce the size of the power module and shorten the circuit length while still maintaining the need for shared conductive pillars. Furthermore, the regional arrangement of the conductive pillars facilitates fabrication and provides overall stable support for the upper circuit board.

[0028] 7. The upper circuit board of the present invention may include one or two PCBs. When a single PCB is used, the power module has a higher level of integration and a smaller size. When two PCBs are used, the power module has a slightly lower level of integration but is easier to disassemble and maintain. Furthermore, when two PCBs are used, by further dividing the PCB on which the RC snubber circuit is located into two separate pieces, each used to separately locate the IGBT RC snubber circuit and the FRD RC snubber circuit, compared to installing the RC snubber circuit on a single PCB, the PCB area can be further reduced while minimizing the loop length, while also facilitating separate disassembly and maintenance of the IGBT RC snubber circuit and the FRD RC snubber circuit.

[0029] 8. The present invention fixes the bottom circuit board, power circuit and conductive column in the insulating shell by vacuum potting, which has the effect of isolating the internal circuit from the influence of external dust and moisture, and is conducive to prolonging the service life of the power module. 9. The present invention arranges the power terminals on both sides of the upper circuit board, and combines the fixing structure of the positioning groove and the bolt, which not only facilitates the rapid docking with external devices and avoids the loose contact caused by vibration at the connection, but also strengthens the fixing of the upper circuit board.

[0030] 10. The preparation method of the present invention is simple and easy to implement, and can realize intelligent production by using machinery. It has strong promotion and replicability, and the power module obtained has the above-mentioned corresponding advantages, which will not be repeated here.

[0031] 11. The present invention adopts specific welding conditions in the vacuum reflow process, which has the advantage of improving the welding yield of the conductive column, which is beneficial to improving the qualified rate of the power module and ensuring stable and reliable conduction effect of the power module.

[0032] 12. The present invention adopts a specific vacuum potting process, which is beneficial to improving the protection performance and stability of the power module as a whole. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic diagram of the three-dimensional structure of the present invention when it includes two layers of circuit boards; Figure 2 This is a schematic diagram of the three-dimensional structure of the present invention when it includes a three-layer circuit board; Figure 3 It is a planar structural diagram of the three-phase rectifier circuit and inverter circuit on the bottom circuit board; Figure 4 It is a planar structural diagram of the secondary rectifier circuit on the bottom circuit board; Figure 5 This is a schematic diagram of the structure of the bottom circuit board on the lower mold; Figure 6This is a schematic diagram of the main structure of the conductive column on the upper mold; Figure 7 It is a side view structural diagram of the upper mold.

[0034] The markings in the figure are: 1. Bottom circuit board, 2. Upper circuit board, 3. IGBT resistor-capacitor absorption circuit, 4. Conductive column, 5. Conductive through-hole, 6. Power terminal, 7. Insulation shell, 8. Positioning groove, 9. Countersunk hole, 10. Three-phase rectifier circuit, 11. Inverter circuit, 12. Secondary rectifier circuit, 13. Drive circuit, 14. FRD resistor-capacitor absorption circuit, 15. Metal heat sink, 16. Copper plating layer, 17. DBC circuit board, 18. Lower mold, 19. Upper mold, 20. Positioning jack, 21. Limit baffle, 22. Pillar, 23. Positioning pin, 24. Positioning hole. DETAILED DESCRIPTION

[0035] Example 1 like Figure 1 、 Figure 2 As shown, this embodiment provides a stacked power module, including a metal heat sink 15. The metal heat sink 15 can be a conventional aluminum heat sink with fins on one side and a flat surface on the other side. Circuit boards are stacked on top of the metal heat sink 15. Crucially, at least two layers of circuit boards are functionally connected by providing a plurality of conductive columns 4 and a plurality of conductive through holes 5, and the following technical requirements must be met: a. Fix the lower end of the conductive pillar 4 to the input end and / or output end of the bottom circuit board 1, and the minimum spacing between adjacent conductive pillars 4 is 2.2 mm to ensure functional conduction between the upper and lower circuit boards.

[0036] b. The conductive through-holes 5 are arranged on the upper circuit board 2 and are arranged correspondingly above the conductive posts 4 so as to ensure that the loop length is the shortest after the upper and lower circuit boards are functionally connected.

[0037] c. Limit the bottom circuit board 1 on the lower mold 18, and apply solder paste to the position of the bottom circuit board 1 corresponding to the fixed conductive column 4; use a pin insertion machine to automatically insert the conductive column 4 into the positioning socket 20 of the upper mold 19, and use a detachable limit baffle 21 to limit the lower end of the conductive column 4; use the positioning pin 23 and the positioning hole 24 to close the upper mold 19 and the lower mold 18, and after closing the mold, pull out the limit baffle 21 to make the lower end of the conductive column 4 fall into the solder paste position on the bottom circuit board 1 respectively, and send the mold into the welding equipment. After welding, the conductive column 4 is vertically fixed on the bottom circuit board 1 to ensure that the upper end of each conductive column 4 can be assembled into each conductive through-hole 5 accordingly.

[0038] In the technical requirement a, according to the different circuits on the bottom circuit board 1, the number of the conductive columns 4 is multiple, and the setting mode has three kinds, which are: the conductive column 4 can be set at the input end of the circuit, the conductive column 4 can be set at the output end of the circuit, and the conductive column 4 can be set at the input end and the output end of the circuit.

[0039] Further, the minimum spacing between adjacent conductive columns 4 is 2.2 mm, which can ensure the insulation effect between adjacent conductive columns 4 under the premise of meeting the safety distance, and can further reduce the volume of the power module as a whole.

[0040] In the technical requirement b, in addition to setting each conductive via 5 directly above each conductive column 4, the spacing between the conductive via 5 and each circuit on the upper circuit board 2 is set to be the shortest, so that the loop length is the shortest after the upper and lower circuit boards are functionally connected.

[0041] In the technical requirement c, as shown in the figure, Figure 5-Figure 7 The upper mold 19 and the lower mold 18 are both graphite molds with rectangular structure, the positioning holes 24 are symmetrically arranged at both ends of the mold closing surface of the lower mold 18, the positioning pins 23 are symmetrically fixed at both ends of the mold closing surface of the upper mold 19, and the positioning pins 23 correspond to the positioning holes 24 one by one, and the positioning pins 23 are further provided with grooves, which can form a sliding groove for the sliding of the limiting baffle 21 through the grooves on the positioning pins 23 at both ends of the upper mold 19. The upper mold 19 is further provided with a support 22 at each corner of the non-mold closing surface, which is used to support the upper mold 19 to make the mold closing surface face upward when the conductive column 4 is inserted, so as to facilitate the insertion of the conductive column 4 into the positioning hole 20 from the upper side by using the pin insertion machine. The diameter of the lower end of the conductive column 4 is larger than that of the column body, and the shape of the positioning hole 20 is matched with that of the conductive column 4. The limiting baffle 21 is arranged on the upper mold 19 through the sliding groove formed by the positioning pins 23, and can be pulled out from the sliding groove. After the conductive column 4 is inserted into the positioning hole 20 of the upper mold 19 by the pin insertion machine, the upper end of the conductive column 4 passes through the positioning hole 20, but the lower end of the conductive column 4 is limited in the positioning hole 20, and then the limiting baffle 21 is inserted to block and limit the lower end of the conductive column 4. At this time, the upper mold 19 can be turned over at will, and the conductive column 4 will not fall off. After the positioning pins 23 and the positioning holes 24 are closed, the limiting baffle 21 is pulled out, so that the lower end of the conductive column 4 falls into the corresponding tin paste position on the bottom circuit board 1 for welding. Through the cooperation of the upper mold 19 and the lower mold 18, a plurality of conductive columns 4 can always keep vertical during the welding and assembly process, which facilitates the smooth assembly of the conductive column 4 into the conductive via 5. Usually, a plurality of bottom circuit boards 1 can be limited on the same lower mold 18, and correspondingly, a plurality of conductive columns 4 can be inserted into the same upper mold 19 at the same time, so as to realize batch production.

[0042] Those skilled in the art will understand that functional connectivity refers to the ability of the two circuit boards, through the coordination of the conductive posts 4 and the conductive vias 5, to achieve functions such as power transmission, signal transfer, and control logic, thereby ensuring that the entire module performs its intended functions, such as power conversion and signal control, according to the designed logic. Furthermore, the spacing between the upper and lower adjacent circuit boards must meet the minimum safety spacing requirement of 6.5mm for air insulation.

[0043] In this embodiment, if Figure 1 、 Figure 2 As shown, the conductive post 4 is a T-shaped structure consisting of a cylindrical rod and a cylindrical cap. The cylindrical cap is welded to the underlying circuit board 1, while the cylindrical rod is welded to the conductive via 5. The outer diameter of the cylindrical cap is larger than that of the cylindrical rod, which enhances the stability and reliability of the connection between the conductive post 4 and the underlying circuit board 1. The outer diameter of the cylindrical rod is slightly smaller than that of the conductive via 5, facilitating mechanized assembly and soldering of the cylindrical rod end through the conductive via 5, preventing cold solder joints and overlay welds, and improving soldering reliability.

[0044] Furthermore, the diameter of the conductive pillar 4 can be in the range of 1-1.2 mm, ensuring that the conductive pillar 4 has sufficient structural strength to facilitate assembly with the conductive via 5 while ensuring reasonable cost. Conversely, if the diameter of the conductive pillar 4 is greater than 1.2 mm, it will result in excessive cost. If the diameter of the conductive pillar 4 is less than 1 mm, it will lack structural strength and will be easily bent, making it difficult to assemble smoothly with the corresponding conductive via 5. Of course, the diameter of the conductive pillar 4 can also be increased accordingly for special scenarios requiring high current.

[0045] In this embodiment, a power circuit is configured on the bottom circuit board 1, and a functional circuit, a transfer wire (preset copper-clad wire that performs a conductive function) and a plurality of power terminals 6 are configured on the upper circuit board 2. The functional circuit and the power terminals 6 are respectively connected to the conductive through-holes 5 via the transfer wires; the conductive pillars 4 are arranged at the input and / or output ends of the power circuit. After the power circuit and the conductive pillars 4 are integrally encapsulated on the bottom circuit board 1, they are connected to the functional circuit via the conductive through-holes 5 and the transfer wires.

[0046] Furthermore, in technical requirement b, the shortest loop length after the upper and lower circuit boards are functionally connected means: the length of the transfer wire between the conductive through hole 5 and the functional circuit is the shortest, and the length of the transfer wire between the conductive through hole 5 and the power terminal 6 is the shortest, thereby shortening the loop length of the power module.

[0047] This embodiment does not limit the power circuits and functional circuits on the circuit board. Those skilled in the art may configure the required circuits on the circuit board based on actual operating conditions. In summary, this embodiment, through the limitations of technical requirements ac, enables chip-level integration of the power module and uniformly utilizes conductive pillars 4 and conductive vias 5 to achieve functional conduction, thereby achieving the effects of reducing size, increasing integration, simplifying structure, simplifying the manufacturing process, facilitating assembly, facilitating mechanized intelligent welding, improving welding quality, shortening loop length, reducing parasitic inductance, reducing voltage spikes, and reducing electromagnetic radiation.

[0048] Example 2 This embodiment further optimizes the structure of the power module based on the first embodiment.

[0049] In this embodiment, if Figure 1 、 Figure 2 As shown, the bottom circuit board 1 is a composite structure of multiple DBC circuit boards 17 and a copper layer 16. The copper layer 16 is applied to a metal heat sink 15, to which the DBC circuit boards 17 are soldered. The power circuit and conductive posts 4 are disposed on the copper layer 16 and the DBC circuit boards 17, respectively. This structure effectively uses a shared copper layer 16 between the bottom circuit board 1 and the heat sink, saving material and improving heat dissipation. Of course, depending on specific functional requirements, the bottom circuit board 1 can also be composed entirely of DBC circuit boards 17 or other similar circuit boards.

[0050] In this embodiment, if Figures 1-4 As shown, the power circuit includes a three-phase rectifier circuit 10, an inverter circuit 11, and a secondary rectifier circuit 12. Conductive posts 4 are respectively arranged at the power input and power output terminals of the three-phase rectifier circuit 10, the signal input and power output terminals of the inverter circuit 11, and the power input terminal of the secondary rectifier circuit 12. The three-phase rectifier circuit 10 and the inverter circuit 11 are respectively arranged at the lower and upper portions of a DBC circuit board 17. Depending on actual operating conditions, the three-phase rectifier circuit 10 and the inverter circuit 11 can also be arranged on two DBC circuit boards 17 arranged one above the other. The secondary rectifier circuit 12 is respectively arranged on the copper-plated layer 16 and on the remaining DBC circuit boards 17. Specifically, the secondary rectifier circuit 12 includes a chip and a copper connector. The lower surface of the chip is directly welded to the copper-plated layer 16. One end of the copper connector is welded to the upper surface of the chip, and the other end is welded to the DBC circuit board 17. At this time, the current generated by the chip can flow to the metal heat sink 15 through the copper plating layer 16 , and then the metal heat sink 15 is used as the current output of the secondary rectifier circuit 12 .

[0051] Furthermore, the conductive posts 4 at the power input end of the three-phase rectifier circuit 10 are located at the bottom of the DBC circuit board 17 and arranged in a matrix. The conductive posts 4 at the power output end of the three-phase rectifier circuit 10 are located in the middle right and upper left portions of the DBC circuit board 17, respectively. The conductive posts 4 at the signal input end of the inverter circuit 11 are located in the upper middle left and upper middle right portions of the DBC circuit board 17, respectively. The conductive post 4 at the power output end of the inverter circuit 11 is located in the middle of the upper portion of the DBC circuit board 17. The conductive posts 4 at the power input end of the secondary rectifier circuit 12 are evenly arranged on multiple DBC circuit boards 17. By arranging the conductive posts 4 in different areas on the bottom circuit board 1, the module can be made smaller and the loop length shorter, and can provide stable support for the upper circuit board 2 as a whole.

[0052] Furthermore, the functional circuit includes a drive circuit 13, an IGBT resistor-capacitor absorption circuit 3 and an FRD resistor-capacitor absorption circuit 14. The specific connection relationship between the power circuit and the functional circuit is as follows: the power input end of the three-phase rectifier circuit 10 is electrically connected to part of the power terminal 6 through the conductive column 4 and the conductive through-hole 5, the power output end of the three-phase rectifier circuit 10 (the power input end of the inverter circuit 11) is electrically connected to part of the power terminal 6 through the conductive column 4 and the conductive through-hole 5, the signal input end of the inverter circuit 11 is electrically connected to the drive circuit 13 through the conductive column 4 and the conductive through-hole 5, the power output end of the inverter circuit 11 is electrically connected to part of the power terminal 6 through the conductive column 4 and the conductive through-hole 5, and the power input end of the secondary rectifier circuit 12 is electrically connected to part of the power terminal 6 through the conductive column 4 and the conductive through-hole 5. The IGBT RC absorption circuit 3 is connected in parallel with the three-phase rectifier circuit 10 via conductive pillars 4 and conductive vias 5. The FRD RC absorption circuit 14 is connected in parallel with the secondary rectifier circuit 12 via conductive pillars 4 and conductive vias 5. The IGBT RC absorption circuit 3 and the three-phase rectifier circuit 10 share the conductive pillars 4 at the power output end of the three-phase rectifier circuit 10 and the conductive pillars 4 at the power output end of the inverter circuit 11. The conductive pillars 4 between the FRD RC absorption circuit 14 and the secondary rectifier circuit 12 are symmetrically arranged on the copper-plated layer 16. By sharing the conductive pillars 4, the number of conductive pillars 4 is reduced, the cost is lowered, and the volume of the power module is reduced.

[0053] It should be noted that the specific circuit structures and mutual connection methods of the three-phase rectifier circuit 10, inverter circuit 11, secondary rectifier circuit 12, drive circuit 13 and resistor-capacitor absorption circuit in this embodiment are all existing conventional technologies. For example, the three-phase rectifier circuit 10 includes multiple rectifier diode chips and corresponding copper connecting pieces, the inverter circuit 11 includes multiple IGBT chips and corresponding copper connecting pieces, and the secondary rectifier circuit 12 includes multiple FRD chips and corresponding copper connecting pieces.

[0054] The power terminals 6 in this embodiment can be configured accordingly based on the specific circuit. Based on the above specific circuit, the number of power terminals 6 can be 11. Among them, three power terminals 6 can serve as the power input terminals of the three-phase rectifier circuit 10, two power terminals 6 can serve as the power output terminals of the inverter circuit 11, and two power terminals 6 can serve as the power input terminals for external capacitors. These two power input terminals for external capacitors are connected to the power output terminals of the three-phase rectifier circuit 10 (the power input terminals of the inverter circuit 11) through conductive posts 4. Finally, four power terminals 6 can serve as the power input terminals of the secondary rectifier circuit 12. Correspondingly, the three-phase rectifier circuit 10 is electrically connected to five power terminals 6 (including three power input terminals of the three-phase rectifier circuit 10 and two power output terminals for external capacitors) through the conductive pillars 4 and the conductive through-holes 5, the inverter circuit 11 is electrically connected to two power terminals 6 (two power output terminals of the inverter circuit 11) through the conductive pillars 4 and the conductive through-holes 5, and the secondary rectifier circuit 12 is electrically connected to four power terminals 6 (four power input terminals of the secondary rectifier circuit 12) through the conductive pillars 4 and the conductive through-holes 5.

[0055] In this embodiment, the number of conductive pillars 4 at the power input end of the three-phase rectifier circuit 10 can be 9, 12, or 16, etc. The number of conductive pillars 4 between the power output end of the three-phase rectifier circuit 10 and the external capacitor can be 4 or 8, etc. The number of conductive pillars 4 between the drive circuit 13 and the signal input end of the inverter circuit 11 can be 3, 4, 7, or 8, etc. The number of conductive pillars 4 between the IGBT RC circuit 3 and the inverter circuit 11 is twice n, where n is a natural number, and the number of conductive pillars 4 between the FRD RC circuit 14 and the secondary rectifier circuit 12 is twice n, where n is a natural number. Of course, the number of the above conductive pillars 4 can be increased or decreased accordingly depending on the current passing through and the connection method of each circuit.

[0056] Figure 3A circuit structure diagram of a three-phase rectifier circuit 10 and an inverter circuit 11 on a bottom circuit board 1 is shown. As can be seen from the figure, the number of conductive pillars 4 at the power input end of the three-phase rectifier circuit 10 is 9 (located at the lower part of the DBC circuit board 17 and arranged in a 3*3 matrix), the number of conductive pillars 4 from the power output end of the three-phase rectifier circuit 10 (the power input end of the inverter circuit 11) to the external capacitor is 8 (4 of which are located in the middle of the right side of the DBC circuit board 17 and arranged vertically, and the other 4 are located in the upper left side and arranged in a 2*2 matrix), the number of conductive pillars 4 at the signal input end of the inverter circuit 11 is 7 (4 of which are located in the upper middle part of the left side of the DBC circuit board 17 and arranged in a 2*2 matrix, and the other 3 are located in the upper middle part of the right side and arranged in a triangle), and the number of conductive pillars 4 at the power output end of the inverter circuit 11 is 8 (located in the middle of the upper part of the DBC circuit board 17 and arranged vertically). There are 16 conductive pillars 4 between the IGBT RC absorption circuit 3 and the inverter circuit 11. These 16 conductive pillars 4 are shared with the conductive pillars 4 between other circuits. Specifically, the IGBT RC absorption circuit 3 is divided into four paths. Each path is connected in parallel with the four IGBT chips of the inverter circuit 11. The four paths share the same 16 conductive pillars 4 with the power input terminal (the power output terminal of the three-phase rectifier circuit 10) and the power output terminal of the inverter circuit 11.

[0057] Figure 4 A circuit structure diagram of a secondary rectifier circuit 12 on a copper-plated layer 16 is shown. As can be seen from the figure, there are 48 conductive pillars 4 on the secondary rectifier circuit 12, of which 44 conductive pillars 4 are used to electrically connect to four power terminals 6 (four power input terminals of the secondary rectifier circuit 12), and the other four conductive pillars 4 are connected to the FRD resistor-capacitor absorption circuit 14.

[0058] In this embodiment, if Figure 1 、 Figure 2As shown, the upper circuit board 2 can be a single PCB or two PCBs stacked above the bottom circuit board 1. When the upper circuit board 2 comprises a single PCB, the drive circuit 13, the IGBT RC snubber circuit 3, and the FRD RC snubber circuit 14 are all disposed on that PCB. When the upper circuit board 2 comprises two PCBs, the drive circuit 13 is disposed on one PCB, while the IGBT RC snubber circuit 3, the FRD RC snubber circuit 14, and the power terminals 6 are all disposed on the other PCB, with the PCB on which the drive circuit 13 is disposed being located above the other PCB. Typically, there is a certain distance between the three-phase rectifier circuit 10 and the secondary rectifier circuit 12, and the PCB on which the RC snubber circuit is disposed is larger than the PCB on which the drive circuit 13 is disposed. To improve stability after the circuit boards are secured and facilitate subsequent removal and replacement of the drive circuit 13, the PCB on which the drive circuit 13 is disposed is preferably located above the other PCB. Of course, without regard to the aforementioned requirements, the PCB on which the drive circuit 13 is disposed can also be located below the other PCB. In addition, under the premise of meeting the functions required by this embodiment, the number of PCB circuit boards included in the upper circuit board 2 can be expanded accordingly as needed.

[0059] Further, such as Figure 2 As shown, the IGBT RC snubber circuit 3 and the FRD RC snubber circuit 14 are again separately arranged on two PCB circuit boards. These two PCB circuit boards are of the same height and are located above the inverter circuit 11 and the secondary rectifier circuit 12, respectively. Compared to simultaneously arranging the IGBT RC snubber circuit 3 and the FRD RC snubber circuit 14 on a single PCB circuit board, the use of two PCB circuit boards in this circuit board layer reduces material usage and PCB area while minimizing loop length, and also facilitates separate assembly and maintenance.

[0060] When the upper circuit board 2 includes two PCBs, the PCB with the RC snubber circuit is the first PCB, and the PCB with the driver circuit 13 is the second PCB. Functional conduction is achieved between the bottom circuit board 1 and the first PCB, and between the bottom circuit board 1 and the second PCB, via the conductive posts 4 and conductive vias 5. There are two connection structures between the bottom circuit board 1 and the second PCB, as follows: The first method is that the conductive pillar 4 on the bottom circuit board 1 is insulated and passes through the first PCB circuit board and is then soldered and fixed to the conductive through hole 5 on the second PCB circuit board. At this time, the driving circuit 13 on the second PCB circuit board can be connected to the power circuit on the bottom circuit board 1 through this part of the conductive pillar 4.

[0061] The second type is to provide a conductive pillar 4 between the first PCB and the second PCB. The conductive pillar 4 can be welded and fixed to either the first PCB or the second PCB. Preferably, the conductive pillar 4 is welded to the second PCB, and the other end of the conductive pillar 4 can be welded and fixed to the conductive through-hole 5 of the first PCB. In this case, the drive circuit 13 on the second PCB can be connected to the power circuit via the conductive pillar 4 between the second PCB and the first PCB drive circuit 13 board, and the conductive pillar 4 between the first PCB drive circuit 13 board and the bottom circuit board 1.

[0062] To facilitate the fixation of the second PCB circuit board, support columns and positioning columns can be provided on the first PCB circuit board, and the second PCB circuit board can be supported and fixed through corresponding screws and screw holes.

[0063] In this embodiment, if Figure 1 、 Figure 2 As shown, an insulating shell 7 is also fixed on the metal heat sink 15, and the insulating shell 7 can be fixed to the copper-plated layer 16 by means of bolts or the like. The bottom circuit board 1, the power circuit and the conductive column 4 are all encapsulated in the insulating shell 7 as a whole through a vacuum potting process. In addition, positioning grooves 8 for fixing the power terminals 6 are respectively provided on both sides of the upper part of the insulating shell 7. A polygonal countersunk hole 9 is provided in the positioning groove 8. A polygonal nut is provided in the countersunk hole 9 and can limit the rotation of the nut. Preferably, the power terminals 6 are L-shaped copper bars welded and fixed on the upper circuit board 2. One end of each L-shaped copper bar is respectively arranged on both sides of the upper circuit board 2, and the other end of each L-shaped copper bar is respectively fixed in the positioning groove 8. After the other end of the L-shaped copper bar is placed in the positioning groove 8, the L-shaped copper bar can be fixed in the positioning groove 8 by bolts and nuts, thereby achieving the fixation of the upper circuit board 2 and electrical connection with external devices. In addition, the L-shaped copper bar can also cooperate with the conductive column 4 to achieve enhanced fixation of the upper circuit board 2, so that the stability and anti-vibration effect of the upper circuit board 2 are better.

[0064] During the preparation of this embodiment, a mold can be used to simultaneously realize the welding and fixation of each circuit and the conductive column 4 on the bottom circuit board 1, and each circuit can be prepared separately using a different mold, or can be prepared simultaneously using the same mold. It is only necessary to design corresponding limiting areas and corresponding positioning holes 20 on the upper and lower molds.

[0065] The working principle of this embodiment is: When the power circuit is working, the external three-phase power supply is connected to the three power terminals 6 on the upper circuit board 2 as the power input end. The current enters the power input end of the three-phase rectifier circuit 10 in sequence through the preset transfer wires, conductive through-holes 5 and 9 conductive pillars 4, and is rectified by the three-phase rectifier circuit 10 and output as DC to the inverter circuit 11. At the DC output end of the three-phase rectifier circuit 10 (the power input end of the inverter circuit 11), it is output to the two power terminals 6 for external capacitors through 8 conductive pillars 4. The inverter circuit 11 outputs to the two power terminals 6 as the power output end through 8 conductive pillars 4. The two power terminals 6 are connected to the primary of the transformer, and the secondary of the transformer is connected to the secondary rectifier circuit 12 through 4 power terminals 6. These four power terminals 6 input current into the secondary rectifier circuit 12 through 44 conductive pillars 4. The output current of the secondary rectifier circuit 12 can be output to the load through the metal heat sink 15. After receiving an external control signal, the drive circuit 13 transmits the control signal to the signal input terminal of the inverter circuit 11 via seven conductive pillars 4, thereby driving and controlling the inverter circuit 11. The IGBT RC absorption circuit 3 provides RC absorption to the inverter circuit 11 via 16 conductive pillars 4, and the FRD RC absorption circuit 14 provides RC absorption to the secondary rectifier circuit 12 via four conductive pillars 4, thereby suppressing voltage fluctuations in the circuit and improving power conversion efficiency.

[0066] The power module provided in this embodiment has the advantages of small size, high integration, simple structure and preparation process, ability to realize mechanized intelligent welding, good welding effect, short loop length, low parasitic inductance, low voltage spike and low electromagnetic radiation, and is particularly suitable for use in welding machines.

[0067] Example 3 This embodiment provides a method for preparing the stacked power module described in embodiment 1 or embodiment 2. The method includes designing the circuit boards to be stacked on the metal heat sink 15 based on the conduction and heat dissipation requirements of the power module, and determining that the layout of the conductive pillars 4 and the conductive vias 5 between the circuit boards should meet the following requirements: a. The lower end of the conductive pillar 4 is fixed to the input end and / or output end of the bottom circuit board 1, and the minimum spacing between adjacent conductive pillars 4 is 2.2 mm to ensure functional conduction between the upper and lower circuit boards.

[0068] b. The conductive through-hole 5 is provided on the upper circuit board 2 and is correspondingly provided directly above the conductive pillar 4 to ensure that the loop length is the shortest after the upper and lower circuit boards are functionally connected.

[0069] Based on the above requirements, the preparation method comprises the following steps: Step 1. Limit the bottom circuit board 1 on the lower mold 18, apply solder paste at the position corresponding to the fixed conductive column 4 and the position corresponding to the fixed power circuit on the bottom circuit board 1, and place the power circuit at the solder paste position corresponding to the fixed power circuit; use a pin insertion machine to automatically insert the conductive column 4 into the positioning hole 20 of the upper mold 19, and use a detachable limit baffle 21 to limit the lower end of the conductive column 4.

[0070] Step 2: Use the positioning pins 23 and the positioning holes 24 to close the upper mold 19 and the lower mold 18. After closing the mold, pull out the limit baffle 21 to make the lower ends of the conductive pillars 4 fall into the corresponding solder paste positions on the bottom circuit board 1 to fix the conductive pillars 4.

[0071] Step 3: Send the mold into the welding equipment, and use the vacuum reflow process to weld the power circuit and the conductive column 4 to the bottom circuit board 1. After welding is completed, open the mold and take out the bottom circuit board 1.

[0072] Step 4: Coat a copper plating layer 16 on the metal heat sink 15, solder and fix the bottom circuit board 1 on the copper plating layer 16, then fix the insulating shell on the copper plating layer 16, and use a vacuum potting process to encapsulate the bottom circuit board 1, the power circuit and the lower end of the conductive column 4 in the insulating shell.

[0073] Step 5: Set up a correction plate with a number of conical countersunk correction holes corresponding to the conductive posts 4. Insert the conductive posts 4 into the conical countersunk correction holes for correction so that the conductive posts 4 always remain vertical.

[0074] Step 6: Set up the upper circuit board 2. The upper circuit board 2 is equipped with functional circuitry, adapter wires, and conductive vias 5 corresponding to the conductive posts 4. The functional circuitry is connected to the conductive vias 5 via the adapter wires. The intelligent robotic arm moves the upper circuit board 2 so that the conductive vias 5 align with the conductive posts 4. The upper circuit board 2 is then controlled to move downward until the upper ends of all conductive posts 4 fit into their corresponding conductive vias 5, completing the stacking of the circuit boards. To improve production efficiency, this step can be performed simultaneously with steps 1-5.

[0075] Step 7: Solder the conductive posts 4 and the conductive through-holes 5 to enable functional conduction between the upper and lower circuit boards through the conductive posts 4 and the conductive through-holes 5, thereby completing the preparation.

[0076] In this embodiment, the vacuum reflow soldering process uses the following soldering conditions: preheating at 100-150°C, a heating rate of 2-3°C / s, a solder reflow temperature of 217-227°C, maintaining an oxygen content of less than 5 ppm during soldering, and holding the soldering temperature for 30-90 seconds after soldering. These specific soldering conditions improve the soldering yield of the conductive pillars 4, thereby increasing the qualified rate of the power modules.

[0077] In this embodiment, the vacuum potting process involves placing the insulating housing 7 and bottom PCB 1 into a potting mold. The mold is then evacuated to -0.1 MPa, after which the air is expelled. Silicone gel with a Shore 00-30 hardness is then injected to completely fill the gaps within the insulating housing 7 and cover the bottom PCB 1, power circuitry, and the lower ends of the conductive pillars 4. After curing, the vacuum potting process is complete. This specific vacuum potting process improves the overall protection and stability of the power module.

[0078] The method is now described in detail by taking the preparation of the stacked power module provided in Example 2 as an example.

[0079] It is assumed that the three-phase rectifier circuit 10 and the inverter circuit 11 are respectively mounted on two DBC circuit boards 17, and the secondary rectifier circuit 12 is respectively mounted on the copper plating layer 16 and four DBC circuit boards 17. Specifically, Figure 5-Figure 7 As shown, When preparing the three-phase rectifier circuit 10, in the lower mold 18, first place the DBC circuit board 17 in the limit area of ​​the lower mold 18, and apply solder paste on the DBC circuit board 17 corresponding to the position of the fixed conductive column 4, the position of the fixed chip and the position of the fixed copper connecting piece. Place the rectifier diode chip on the solder paste corresponding to the fixed chip position, then apply solder paste on the rectifier diode chip, and place the two ends of the copper connecting piece on the solder paste corresponding to the fixed copper connecting piece position and the solder paste of the rectifier diode chip respectively. In the upper mold 19, the conductive column 4 is first automatically inserted into the positioning socket 20 of the upper mold 19 using a pin insertion machine, and the limit baffle 21 is inserted to limit the lower end of the conductive column 4, and then the positioning pin 23 and the positioning hole 24 are used to close the upper mold 19 and the lower mold 18. After closing the mold, the limit baffle 21 is pulled out, and the lower end of each conductive column 4 can automatically fall onto the solder paste corresponding to the fixed position of the conductive column 4 under the action of gravity. It can be sent into the welding equipment to realize the welding and fixation of the three-phase rectifier circuit 10 and the conductive column 4 on the DBC circuit board 17.

[0080] Similarly, the preparation of the inverter circuit 11 and the secondary rectifier circuit 12 can be completed. It should be noted that when preparing the secondary rectifier circuit 12, the FRD chip is directly placed in the limit area of ​​the lower mold 18, and the FRD chip and the DBC circuit board 17 can be connected into a whole through the copper connecting piece. Finally, each circuit and the conductive column 4 are correspondingly welded on the copper plating layer 16.

[0081] In detail, based on the same innovative concept, the specific implementation process of this embodiment can refer to the implementation of the aforementioned power module, and the repeated parts will be omitted.

[0082] The above description is only a specific embodiment of the present invention. Any feature disclosed in this specification, unless otherwise stated, can be replaced by other equivalent features; all disclosed features, or all steps in the methods or processes, except for mutually exclusive features and / or steps, can be combined in any way.

Claims

1. A stacked power module, comprising a metal heat sink (15), with circuit boards stacked on top of the metal heat sink (15), characterized in that: At least two layers of circuit boards are connected to each other by providing a plurality of conductive posts (4) and a plurality of conductive through holes (5), and the following technical requirements should be met: a. Fixing the lower end of the conductive column (4) to the input end and / or output end of the bottom circuit board (1), and the minimum spacing between adjacent conductive columns (4) is 2.2 mm to ensure functional conduction between the upper and lower circuit boards; b. The conductive through hole (5) is correspondingly arranged directly above the conductive column (4), and the loop length is the shortest after the upper and lower circuit boards are functionally connected; c. Position the bottom circuit board (1) on the lower mold (18), and apply solder paste to the positions of the bottom circuit board (1) corresponding to the fixed conductive posts (4); automatically insert the conductive posts (4) into the positioning holes (20) of the upper mold (19) using a pin insertion machine, and position the lower ends of the conductive posts (4) using a detachable limiting baffle (21); close the upper mold (19) and the lower mold (18) using the positioning pins (23) and the positioning holes (24); after closing the molds, remove the limiting baffle (21) so that the lower ends of the conductive posts (4) fall into the positions of the solder paste on the bottom circuit board (1), and send the mold into the welding equipment. After welding, the conductive posts (4) are vertically fixed on the bottom circuit board (1) to ensure that the upper ends of the conductive posts (4) can be assembled into the conductive through holes (5) accordingly.

2. The stacked power module according to claim 1, wherein: The conductive column (4) is a T-shaped structure comprising a cylindrical rod and a cylindrical cap, the cylindrical cap is welded and fixed on the bottom circuit board (1), and the cylindrical rod is welded and fixed in the conductive through hole (5), and the diameter of the cylindrical rod is 1-1.2 mm.

3. The stacked power module according to claim 1 or 2, characterized in that: The bottom circuit board (1) is provided with a power circuit, and the upper circuit board (2) is provided with a functional circuit, a switching conductor, and a plurality of power terminals (6). The functional circuit and the power terminals (6) are respectively connected to the conductive through-holes (5) via the switching conductors. The conductive column (4) is provided at the input end and / or the output end of the power circuit. After the power circuit and the conductive column (4) are integrally packaged on the bottom circuit board (1), they are connected to the functional circuit via the conductive through-holes (5) and the switching conductors.

4. The stacked power module according to claim 3, wherein: The shortest loop length after the upper and lower circuit boards are functionally connected means that the length of the transfer wires between the conductive through hole (5) and the functional circuit and between the conductive through hole (5) and the power terminal (6) is the shortest.

5. The stacked power module according to claim 3, wherein: The power circuit comprises a three-phase rectifier circuit (10), an inverter circuit (11) and a secondary rectifier circuit (12). The power input end of the three-phase rectifier circuit (10) is electrically connected to a portion of the power terminals (6) through a conductive column (4) and a conductive through hole (5). The power output end of the three-phase rectifier circuit (10) is electrically connected to a portion of the power terminals (6) through a conductive column (4) and a conductive through hole (5). The signal input end of the inverter circuit (11) is electrically connected to the drive circuit (13) through a conductive column (4) and a conductive through hole (5). The power output end of the inverter circuit (11) is electrically connected to a portion of the power terminals (6) through a conductive column (4) and a conductive through hole (5). The power input end of the secondary rectifier circuit (12) is electrically connected to a portion of the power terminals (6) through a conductive column (4) and a conductive through hole (5).

6. The stacked power module according to claim 5, characterized in that: The bottom circuit board (1) is a composite structure of multiple DBC circuit boards (17) and a copper-plated layer (16), wherein the copper-plated layer (16) is coated on a metal heat sink (15), and the DBC circuit board (17) is welded and fixed on the copper-plated layer (16). The three-phase rectifier circuit (10) and the inverter circuit (11) are respectively arranged on the lower part and the upper part of a DBC circuit board (17), and the secondary rectifier circuit (12) is respectively arranged on the copper-plated layer (16) and the remaining DBC circuit boards (17).

7. The stacked power module according to claim 6, characterized in that: The conductive posts (4) at the power input end of the three-phase rectifier circuit (10) are located at the lower part of the DBC circuit board (17) and are arranged in a matrix. The conductive posts (4) at the power output end of the three-phase rectifier circuit (10) are respectively located at the middle of the right side and the upper part of the left side of the DBC circuit board (17). The conductive posts (4) at the signal input end of the inverter circuit (11) are respectively located at the middle upper part of the left side and the middle upper part of the right side of the DBC circuit board (17). The conductive posts (4) at the power output end of the inverter circuit (11) are located in the middle of the upper part of the DBC circuit board (17). The conductive posts (4) at the power input end of the secondary rectifier circuit (12) are respectively and evenly arranged on multiple DBC circuit boards (17).

8. A stacked power module according to any one of claims 5 to 7, characterized in that: The functional circuit includes a driving circuit (13), an IGBT resistor-capacitor absorption circuit (3) and an FRD resistor-capacitor absorption circuit (14); the IGBT resistor-capacitor absorption circuit (3) is connected in parallel with the three-phase rectifier circuit (10) through a conductive column (4) and a conductive through-hole (5); the FRD resistor-capacitor absorption circuit (14) is connected in parallel with the secondary rectifier circuit (12) through a conductive column (4) and a conductive through-hole (5); the IGBT resistor-capacitor absorption circuit (3) and the three-phase rectifier circuit (10) share the conductive column (4) at the power output end of the three-phase rectifier circuit (10) and the conductive column (4) at the power output end of the inverter circuit (11); and the conductive column (4) between the FRD resistor-capacitor absorption circuit (14) and the secondary rectifier circuit (12) is symmetrically arranged on the copper plating layer (16).

9. The stacked power module according to claim 8, characterized in that: The upper circuit board (2) includes a PCB circuit board or two PCB circuit boards stacked and arranged above the bottom circuit board (1); when the upper circuit board (2) includes a PCB circuit board, the drive circuit (13), the IGBT resistor-capacitor absorption circuit (3), and the FRD resistor-capacitor absorption circuit (14) are all arranged on the PCB circuit board; when the upper circuit board (2) includes two PCB circuit boards, the drive circuit (13) is arranged on one of the PCB circuit boards, the IGBT resistor-capacitor absorption circuit (3), the FRD resistor-capacitor absorption circuit (14), and the power supply terminal (6) are all arranged on the other PCB circuit board, and the PCB circuit board on which the drive circuit (13) is arranged is located above the other PCB circuit board.

10. The stacked power module according to claim 9, characterized in that: The IGBT resistance-capacitance absorption circuit (3) and the FRD resistance-capacitance absorption circuit (14) are respectively arranged on two PCB circuit boards, the two PCB circuit boards having the same height and being respectively located above the inverter circuit (11) and the secondary rectifier circuit (12).

11. The stacked power module according to claim 3, characterized in that: An insulating shell (7) is fixed on the metal heat sink (15), and the bottom circuit board (1), the power circuit and the conductive column (4) are all encapsulated in the insulating shell (7) as a whole through a vacuum potting process. Positioning grooves (8) for fixing the power terminals (6) are respectively opened on both sides of the upper part of the insulating shell (7), and countersunk holes (9) are provided in the positioning grooves (8), and nuts are provided in the countersunk holes (9); the power terminals (6) are L-shaped copper bars fixed to the upper circuit board (2) by welding, and one end of each L-shaped copper bar is respectively arranged on both sides of the upper circuit board (2), and the other end of each L-shaped copper bar is fixed in the positioning groove (8) by bolts and nuts and is electrically connected to external devices.

12. A method for preparing a stacked power module, characterized in that: The method includes designing a circuit board to be stacked on the metal heat sink (15) based on the conduction requirements and heat dissipation requirements of the power module, and determining that the layout of the conductive columns (4) and the conductive through holes (5) between the circuit boards should meet the following requirements: a. The lower end of the conductive column (4) is fixed to the input end and / or output end of the bottom circuit board (1), and the minimum spacing between adjacent conductive columns (4) is 2.2 mm to ensure functional conduction between the upper and lower circuit boards; b. The conductive through hole (5) is correspondingly arranged just above the conductive column (4) to ensure that the loop length is the shortest after the upper and lower circuit boards are functionally connected; Based on the above requirements, the preparation method comprises the following steps: Step 1: Position the bottom circuit board (1) on the lower mold (18), apply solder paste at positions corresponding to the fixed conductive posts (4) and the fixed power circuit on the bottom circuit board (1), and place the power circuit on the corresponding solder paste; automatically insert the conductive posts (4) into the positioning holes (20) of the upper mold (19) using a pin insertion machine, and position the lower ends of the conductive posts (4) using a detachable limiting baffle (21); Step 2: Using the positioning pins (23) and the positioning holes (24), the upper mold (19) and the lower mold (18) are closed. After closing the molds, the limit baffle (21) is pulled out to allow the lower ends of the conductive pillars (4) to fall into the corresponding solder paste positions of the fixed conductive pillars (4) on the bottom circuit board (1); Step 3: Place the mold into a welding device and use a vacuum reflow process to weld the power circuit and the conductive column (4) to the bottom circuit board (1). After welding is completed, open the mold and remove the bottom circuit board (1). Step 4: Coating a copper plating layer (16) on the metal heat sink (15), soldering and fixing the bottom circuit board (1) on the copper plating layer (16), then fixing an insulating shell on the copper plating layer (16), and encapsulating the bottom circuit board (1), the power circuit and the lower end of the conductive column (4) in the insulating shell by a vacuum potting process; Step 5, setting a correction plate, on which a plurality of conical countersunk correction holes corresponding to the conductive posts (4) are provided, and the conductive posts (4) are inserted into the conical countersunk correction holes for correction, so that the conductive posts (4) are always kept vertical; Step 6: setting an upper circuit board (2), wherein the upper circuit board (2) is provided with a functional circuit, a transfer wire, and a conductive through hole (5) corresponding to the conductive column (4), and the functional circuit is connected to the conductive through hole (5) via the transfer wire; moving the upper circuit board (2) by an intelligent manipulator so that the conductive through hole (5) corresponds to the conductive column (4), and controlling the upper circuit board (2) to move downward until the upper ends of all the conductive columns (4) are respectively assembled into the corresponding conductive through holes (5), thereby realizing the upper and lower stacking of the circuit boards; Step 7: Weld the conductive posts (4) and the conductive through-holes (5) so that the upper and lower circuit boards can be functionally connected through the conductive posts (4) and the conductive through-holes (5), thereby completing the preparation.

13. The method for preparing a stacked power module according to claim 12, wherein: In step 3, the vacuum reflow soldering process conditions are: preheating 100-150°C, heating rate 2-3°C / s, solder reflow temperature 217-227°C, maintaining oxygen content <5ppm during soldering, and holding for 30-90 seconds after soldering; In step 4, the specific process of the vacuum potting process is as follows: placing the insulating shell (7) and the bottom circuit board (1) into the potting mold, evacuating to -0.1Mpa and exhausting the air, then injecting a silicone gel with a hardness of Shore 00-30 to fill the gap in the insulating shell (7) and cover the bottom circuit board (1), the power circuit and the lower end of the conductive column (4), and completing the vacuum potting after curing.

Images