Power assembly preparation method based on single-tube parallel connection

Abstract

The invention discloses a power assembly preparation method based on single-tube parallel connection. The method comprises the steps that copper layers are sprayed on different areas of the upper surface of an aluminum bottom plate; the aluminum bottom plate is subjected to pre-bending treatment; printing a layer of soldering paste on the surface of the copper layer; printing a composite soldering paste layer on the upper surface of the DBC insulating sheet; bending processing is carried out on the pins of the device; a plurality of devices and a plurality of DBC insulation sheets are sequentially placed on an aluminum bottom plate, vacuum welding with pulse pressure and temperature cooperative control is carried out, and a welded power assembly is obtained; and cleaning the power assembly, and finishing preparation. According to the invention, a plurality of single-tube devices are welded on the aluminum bottom plate through metal vacuum welding in combination with a process of spraying copper on the aluminum bottom plate to manufacture the power assembly, so that the power assembly can be flexibly spliced subsequently, the use of higher power is realized, and the heat dissipation efficiency is improved.

Description

Technical Field

[0001] This invention belongs to the technical field of power device fabrication, specifically relating to a method for fabricating a power module based on parallel connection of single transistors. Background Technology

[0002] With the development of power devices, especially chip technology, chip power density is increasing, making heat dissipation a key factor in power device applications. Power devices are semiconductor devices specifically designed to process and control high-voltage, high-current, or high-power electrical energy. They are the core actuators of power electronic systems, responsible for power conversion, switching, control, and regulation, and are suitable for applications requiring high current, such as driving motors and high-power power supplies. Essentially, they are electronic components with high output power. However, most existing power devices are used individually. In practical applications, especially in high-power scenarios, multiple individual transistors need to be connected in parallel. Installation and heat dissipation pose design challenges, requiring parallel soldering of individual devices, which is inefficient. Modular and component-based application scenarios have not yet been formed, and modular fabrication processes are also lacking. Summary of the Invention The purpose of this invention is to address the aforementioned shortcomings in the prior art by providing a method for fabricating power components based on parallel connection of single transistors, thereby solving the problem that the prior art lacks a modular fabrication process for power devices.

[0003] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for fabricating a power module based on parallel connection of single transistors includes the following steps: S1. Spray copper layer onto different areas of the upper surface of the aluminum base plate; S2. Pre-bend the aluminum base plate; S3. Print a layer of solder paste on the surface of the copper layer; S4. Print a composite solder paste layer on the upper surface of the DBC insulating sheet; S5. Bend the pins of the device; S6. Place multiple devices and multiple DBC insulating sheets sequentially on an aluminum base plate and perform vacuum welding with pulse pressure and temperature coordinated control to obtain the welded power assembly. S7. Clean the power components to complete the preparation process.

[0004] Furthermore, S1 specifically includes: At least two spaced areas are positioned on the surface of the aluminum base plate, and a 100µm copper layer with a thickness of 0.1 to 0.2 mm is sprayed into each area using cold gas dynamics spraying technology.

[0005] Furthermore, in S2, the pre-bent radius of the aluminum base plate is 0.3mm ± 0.05mm.

[0006] Furthermore, S3 specifically includes: An aluminum base plate coated with a copper layer is clamped onto a fixture, and a layer of solder paste with a thickness of 0.3 to 0.5 mm is printed on the surface of the copper layer along the long side of the aluminum base plate using a screen printing machine.

[0007] Furthermore, in step S4, a screen printing machine is used to print a composite solder paste layer on the upper surface of the DBC insulating sheet. The material of the composite solder paste layer on the upper surface of the DBC insulating sheet is SAC305 doped with rare earth elements, and its melting point is ≥220℃.

[0008] Furthermore, in step S6, multiple devices are placed on the composite solder paste layer on the upper surface of the corresponding DBC insulating sheet, and then the composite solder paste layer on the lower surface of the DBC insulating sheet is placed on the copper layer surface to complete the stacking and installation of the power components.

[0009] Furthermore, in step S6, the vacuum welding process involving coordinated control of pulsed pressure and temperature specifically includes: S61. Place the stacked power components into a high-temperature vacuum welding furnace. S62. The power components are preheated using gradient heating and nitrogen protection. S63. After preheating, maintain the high temperature state in the high temperature vacuum welding furnace; S64. Vacuum welding of power components is performed using third-order pulse pressure oscillation. S65. A segmented pressure relief method is used to release the vacuum from the power components; S66. Introduce nitrogen gas to cool the power components.

[0010] Furthermore, in S62, the gradient heating includes: first raising the temperature to 180°C at a heating rate of 3°C / s, and then raising the temperature to 230-250°C at a heating rate of 1°C / s; the protective flow rate of nitrogen gas is 8L / min.

[0011] Furthermore, in S64, there is a third-order pulse pressure oscillation, and the pulse gas is high-purity nitrogen with an oxygen content of ≤400ppm. In the first stage, a high-vacuum suction method is used to evacuate the high-temperature vacuum welding furnace to a vacuum, maintain the pressure level at 100Pa, and continue for 30-50 seconds to allow large air bubbles in the molten solder to expand and burst during the welding process. Phase 2: Gradually introduce pulsed gas to form a pressure gradient and maintain the pressure level at 10³ Pa for 2-3 seconds to allow large air bubbles to rise to the solder surface. Phase 3: Rapidly introduce pulsed gas to create a micro-positive pressure impact, with a pressure level of 10.5 Pa, lasting for 1-2 seconds, to drive the solder into the microscopic gaps.

[0012] The power module fabrication method based on parallel connection of single tubes provided by this invention has the following beneficial effects: This invention uses metal vacuum welding, combined with copper spraying on an aluminum base plate, to weld multiple (2-4) single-tube devices onto the aluminum base plate, creating a high-yield (small) component. This allows for flexible panelization in the future, enabling higher power output and improved heat dissipation efficiency.

[0013] This invention achieves an extremely low welding void rate through vacuum metal welding; it achieves weldability of the aluminum plate by spraying copper onto the aluminum base plate, while replacing the copper plate and reducing the cost of small components; and it can improve the flexibility of power components by using different panel layouts for the small components.

[0014] The power component of this invention has strong stability due to the welding process between each layer, and has higher reliability compared to the commonly used crimping and tooling locking methods.

[0015] The power components manufactured using vacuum welding in this invention can improve thermal conductivity by about 20% compared to traditional methods, which translates to a power increase of nearly 20%. These power components are easy to assemble and combine, allowing them to be applied to larger power applications. Attached Figure Description

[0016] Figure 1 This is a flowchart of the power component fabrication method based on parallel single-tube connection in this embodiment.

[0017] Figure 2 This is a schematic diagram of the power component structure based on parallel single-tube connection in this embodiment. Figure 1 ; Figure 3 This is a schematic diagram of the power component structure based on parallel single-tube connection in this embodiment. Figure 2 .

[0018] The components include: 1. Aluminum base plate; 2. Copper layer; 3. DBC insulating sheet; 4. Components. Detailed Implementation

[0019] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0020] This embodiment of the power module fabrication method based on single-tube parallel connection uses metal vacuum welding, combined with copper spraying on an aluminum base plate 1, to weld multiple (2-4) single-tube devices 4 onto the aluminum base plate 1, thus fabricating a low-power module. This allows for flexible panelization in the future, enabling higher power applications. (See reference...) Figure 1 Specifically, it includes the following: S1. Copper layer 2 is sprayed onto different areas of the upper surface of aluminum base plate 1; refer to Figure 2 and Figure 3 At least two spaced areas are positioned on the surface of the aluminum base plate 1. In this embodiment, three identical areas are preferably set, with each area spaced apart and each area corresponding to a device 4. Then, using cold gas dynamics spraying technology, a 100µm copper layer 2 is sprayed in each area, with a thickness of 0.1 to 0.2 mm.

[0021] S2. Pre-bend the aluminum base plate 1; The pre-bent radius of the aluminum base plate 1 is 0.3mm ± 0.05mm, which ensures the flatness of the aluminum base plate 1 after welding.

[0022] S3. Print a layer of solder paste on the surface of copper layer 2; A layer of solder paste is printed onto the surface of copper layer 2 using screen printing. Specifically, the aluminum base plate 1 is fixed on a tooling fixture, and a layer of solder paste (lead-based or lead-free solder paste is selected depending on the application; generally, Pb62Sn36Ag2 and Sn96.5Ag3Cu0.5 are used) is printed onto its surface using a screen printing machine. Since the aluminum base plate 1 is pre-bent, the printing must be performed along the long side of the aluminum base plate 1 to ensure the consistency of the solder paste thickness after printing. The thickness of the solder paste is controlled between 0.3 and 0.5 mm.

[0023] S4. Print a composite solder paste layer on the upper surface of the DBC insulating sheet 3 to improve the welding stability of the DBC insulating sheet 3. Specifically, a composite solder paste layer is printed on the upper surface of the DBC insulating sheet 3 using a screen printing machine. The material of the composite solder paste layer on the upper surface of the DBC insulating sheet 3 is SAC305 doped with rare earth elements, and its melting point is ≥220℃.

[0024] S5. Bend the pins of device 4 to ensure the consistency of the pin bending, wherein the consistency of the bent pins is within 0.2mm.

[0025] S6. Place multiple devices 4 and multiple DBC insulating sheets 3 sequentially on the aluminum base plate 1, and perform vacuum welding with pulse pressure and temperature coordinated control to obtain the welded power assembly. First, place the three devices 4 on the composite solder paste layer on the upper surface of the corresponding DBC insulating sheet 3, and then place the composite solder paste layer on the lower surface of the DBC insulating sheet 3 on the solder paste on the surface of the copper layer 2 to complete the stacking and installation of the power components.

[0026] This embodiment demonstrates vacuum welding with coordinated pulse pressure and temperature control, specifically including: S61. Place the stacked power components into a high-temperature vacuum welding furnace. S62. The power components are preheated using gradient heating and nitrogen protection to suppress pre-oxidation; The gradient heating process includes: first raising the temperature to 180℃ at a heating rate of 3℃ / s, and then raising the temperature to 230-250℃ at a heating rate of 1℃ / s; the protective flow rate of nitrogen gas is 8L / min.

[0027] S63. After preheating, maintain the high temperature state in the high temperature vacuum welding furnace; The high-temperature state of this embodiment is 240±10℃, and the vacuum degree is <0.1kpa, which is used to remove residual atmospheric gas and prevent solder splatter.

[0028] S64. Vacuum welding of power components is performed using third-order pulse pressure oscillation. The third-order pulsed pressure oscillation uses high-purity nitrogen as the pulsed gas, with an oxygen content ≤400ppm; its pulse frequency is 15-20Hz.

[0029] The third-order pulse pressure oscillation includes: Phase 1: High vacuum suction is used to evacuate the high-temperature vacuum welding furnace to a vacuum, maintaining the pressure level below 100Pa for 30-50 seconds, so that large air bubbles in the molten solder will expand and burst during the welding process. Phase 2: Gradually introduce pulsed gas to form a pressure gradient and maintain the pressure level at 10³ Pa for 2-3 seconds to allow large air bubbles to rise to the solder surface. Phase 3: Rapidly introduce pulsed gas to create a micro-positive pressure impact, with a pressure level of 10. 5 Pa, lasting for 1-2 seconds, to drive the solder into the microscopic gaps.

[0030] S65. A segmented pressure relief method is used to release the vacuum from the power components; S66. Introduce nitrogen gas to cool the power components.

[0031] S7. Clean the power components to complete the preparation process.

[0032] Specifically, a hydrocarbon cleaning solution is used to clean the surface and remove welding residues to ensure the appearance of the power components.

[0033] After welding, the void rate is tested by X-ray. The void rate after welding is guaranteed to be less than 5% for the whole and less than 1% for a single void.

[0034] Although specific embodiments of the invention have been described in detail with reference to the accompanying drawings, this should not be construed as limiting the scope of protection of this patent. Various modifications and variations that can be made by a person skilled in the art without inventive effort within the scope described in the claims still fall within the scope of protection of this patent.

Claims

1. A method for fabricating a power module based on parallel connection of single transistors, characterized in that, Includes the following steps: S1. Spray copper layer onto different areas of the upper surface of the aluminum base plate; S2. Pre-bending the aluminum base plate; S3. Print a layer of solder paste on the surface of the copper layer; S4. Print a composite solder paste layer on the upper surface of the DBC insulating sheet; S5. Bend the pins of the device; S6. Place multiple devices and multiple DBC insulating sheets sequentially on an aluminum base plate and perform vacuum welding with pulse pressure and temperature coordinated control to obtain the welded power assembly. S7. Clean the power components to complete the preparation process.

2. The method for fabricating a power module based on parallel single-tube connection according to claim 1, characterized in that, S1 specifically includes: At least two spaced areas are positioned on the surface of the aluminum base plate, and a 100µm copper layer with a thickness of 0.1 to 0.2 mm is sprayed into each area using cold gas dynamics spraying technology.

3. The method for fabricating a power module based on parallel single-tube connection according to claim 1, characterized in that, In S2, the pre-bent radius of the aluminum base plate is 0.3mm ± 0.05mm.

4. The method for fabricating a power module based on parallel single-tube connection according to claim 1, characterized in that, S3 specifically includes: An aluminum base plate coated with a copper layer is clamped onto a fixture, and a layer of solder paste with a thickness of 0.3 to 0.5 mm is printed on the surface of the copper layer along the long side of the aluminum base plate using a screen printing machine.

5. The method for fabricating a power module based on parallel single-tube connection according to claim 1, characterized in that, In step S4, a composite solder paste layer is printed on the upper surface of the DBC insulating sheet using a screen printing machine. The material of the composite solder paste layer on the upper surface of the DBC insulating sheet is SAC305 doped with rare earth elements, and its melting point is ≥220℃.

6. The method for fabricating a power module based on parallel single-tube connection according to claim 1, characterized in that, In step S6, multiple devices are placed on the composite solder paste layer on the upper surface of the corresponding DBC insulating sheet, and then the composite solder paste layer on the lower surface of the DBC insulating sheet is placed on the copper layer surface to complete the stacking and installation of the power components.

7. The method for fabricating a power module based on parallel single-tube connection according to claim 1, characterized in that, In step S6, the vacuum welding process, which involves coordinated control of pulsed pressure and temperature, specifically includes: S61. Place the stacked power components into a high-temperature vacuum welding furnace. S62. The power components are preheated using gradient heating and nitrogen protection. S63. After preheating, maintain the high temperature state in the high temperature vacuum welding furnace; S64. Vacuum welding of power components is performed using third-order pulse pressure oscillation. S65. A segmented pressure relief method is used to release the vacuum from the power components; S66. Introduce nitrogen gas to cool the power components.

8. The method for fabricating a power module based on parallel connection of single transistors according to claim 7, characterized in that, In step S62, the gradient heating includes: first raising the temperature to 180°C at a heating rate of 3°C / s, and then raising the temperature to 230-250°C at a heating rate of 1°C / s; the protective flow rate of nitrogen gas is 8L / min.

9. The method for fabricating a power module based on parallel single-tube connection according to claim 7, characterized in that, In S64, there is a third-order pulse pressure oscillation, and the pulse gas is high-purity nitrogen with an oxygen content of ≤400ppm. In the first stage, a high-vacuum suction method is used to evacuate the high-temperature vacuum welding furnace to a vacuum, maintain the pressure level at 100 Pa, and continue for 30-50 seconds to allow large air bubbles in the molten solder to expand and burst during the welding process. Phase 2: Gradually introduce pulsed gas to form a pressure gradient and maintain the pressure level at 10³ Pa for 2-3 seconds to allow large air bubbles to rise to the solder surface. Phase 3: Rapidly introduce pulsed gas to create a micro-positive pressure impact, with a pressure level of 10. 5 Pa, lasting for 1-2 seconds, to drive the solder into the microscopic gaps.

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