Packaging method of half-bridge plastic package type power module

Abstract

The invention discloses a packaging method of a half-bridge plastic packaging type power module. According to the technical scheme, external pins are omitted, the signal terminal module and the power terminal module are directly welded to the AMB substrate, and the leading-out process of a complex frame structure in a traditional packaging process is remarkably simplified; packaging steps are simpler, fixing, welding and subsequent protection processing of a large number of pins do not need to be processed, and the process difficulty is reduced; potential fault points caused by factors such as welding points between the pins and the module, contact resistance, mechanical stress of the pins and the like in a traditional pin connection mode are reduced. The direct welding mode enhances the stability of internal connection of the module, improves the reliability of the module in severe working environments of vibration, temperature change and the like, and reduces the fault risk caused by the problems of connection looseness, oxidation and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor device packaging, and in particular to a packaging method for a half-bridge plastic-encapsulated power module. Background Art

[0002] In the current field of power module technology, the widespread adoption of SiC (silicon carbide) materials is driving increasingly stringent requirements for their packaging. While HPD-packaged SiC modules were once popular, numerous issues have emerged in practical applications, including poor performance at junction temperature, which hinders the full potential of SiC materials in high-temperature environments. The presence of stray inductance also limits high-frequency performance. Furthermore, there are issues with PC power cycling and H3TRB reverse bias reliability under high-temperature and high-humidity conditions, preventing this packaging process from fully realizing the SiC material's greatest advantages.

[0003] Traditional plastic-encapsulated half-bridge SiC modules with front-side pin-outs also face a dilemma. Due to the fixed pin-out locations reserved in the mold, the modules are incompatible with a variety of circuit topologies, significantly limiting their versatility and applicability. Furthermore, the pin-outs lack flexibility, making it difficult to meet the complex and ever-changing requirements of actual circuit layouts. During the packaging process, the complex framework structure for the outward lead significantly increases the difficulty of the packaging process, increasing production costs and reducing efficiency. Summary of the Invention

[0004] In view of the problems existing in the above-mentioned prior art, the present invention provides a packaging method for a half-bridge plastic-encapsulated power module, which can effectively solve the problems existing in the above-mentioned prior art.

[0005] The technical solution of the present invention is:

[0006] According to one aspect of the present invention, the following steps are included:

[0007] S1. Etching at least one mounting unit on the surface of the AMB ceramic substrate, wherein the mounting unit includes: a chip mounting area, a power terminal module mounting area, and a signal terminal module mounting area;

[0008] S2. In an oxygen-free environment, sinter and fix the chip on the chip mounting area;

[0009] S3. Welding the metal electrodes to the power terminal module mounting area and the signal terminal module mounting area to achieve electrical connection with the AMB ceramic substrate; at the same time, welding the metal bonding parts to the AMB ceramic substrate to achieve electrical connection with the AMB ceramic substrate; electrically connecting the chip gate to the signal terminal on the surface of the AMB ceramic substrate through the metal bonding wire;

[0010] S4. Welding the power terminal module and the signal terminal module to the metal electrodes in the corresponding mounting areas;

[0011] S5. Welding the metal electrodes to the end surfaces of the power terminal module and the signal terminal module facing away from the AMB ceramic substrate;

[0012] S6. Injection molding is performed on the outside of the AMB ceramic substrate and the mounting unit to form a plastic sealing layer, exposing only the metal electrode end surfaces of the power terminal module and the metal electrode end surfaces of the signal terminal module;

[0013] S7, soldering the pin to the metal electrode of the signal terminal module;

[0014] S8. Assemble the plastic-sealed power module onto a heat sink.

[0015] Furthermore, the chip sintering in step S2 includes:

[0016] Print sintered silver paste with a silver content of 88-92% on the chip mounting area with a printing thickness of 80-120μm;

[0017] Place the AMB ceramic substrate in an oxygen-free oven at 80-120°C for 10-30 minutes to remove the solvent;

[0018] Introduce nitrogen into the pressure sintering furnace, apply a pressure of 0.5-1.0 MPa, and sinter at a temperature of 220-260° C. for 15-25 minutes to fix the chip.

[0019] Furthermore, the metal electrode is a full copper metal electrode or a full copper gold-plated metal electrode.

[0020] Furthermore, the metal electrode welding in step S3 includes:

[0021] Use metal electrodes with a thickness of 0.3-0.5mm and weld them in a formic acid welding furnace at a temperature of 180-220℃;

[0022] The formic acid gas concentration is maintained at 200-500 ppm, and the welding time is controlled at 60-120 seconds to form an electrical connection between the metal electrode and the AMB ceramic substrate.

[0023] Furthermore, in step S3, the chip gate is electrically connected to the signal terminal on the surface of the AMB ceramic substrate through a metal bonding wire, which specifically includes:

[0024] An aluminum wire bonder is used to bond the chip gate and the AMB ceramic substrate.

[0025] Furthermore, in step S4, the power terminal module is welded using a preformed solder sheet with a copper content of ≥99.9%, and is welded in a formic acid reducing atmosphere at 250-280° C. for 30-60 seconds, with a solder layer thickness of 50-100 μm.

[0026] Furthermore, the molding of the plastic sealing layer in step S6 includes:

[0027] Use epoxy molding compound for injection molding at a pressure of 8-12 MPa and a temperature of 165-180°C, with a curing time of 3-5 minutes;

[0028] After plastic sealing, laser polishing is used to remove overflow, with a laser power of 50-80W and a scanning interval of 0.1-0.3mm.

[0029] Furthermore, the pin welding in step S7 includes:

[0030] Laser cleaning of the metal electrodes of the signal terminal module to remove oxides on the surface of the metal electrodes. The laser wavelength is 322-355nm, the power is 20-40W, and the scanning speed is 100-200mm / s.

[0031] Ultrasonic welding equipment is used to weld the pin to the center of the metal electrode at a frequency of 60-100kHz and a pressure of 0.5-1.0N with a tolerance of ±0.1mm.

[0032] Furthermore, the heat sink assembly in step S8 includes:

[0033] Print solder on the surface of the heat sink with a thickness of 150-200μm;

[0034] Sintering is carried out by step-by-step heating: the first stage is 150℃ for deoxidation for 8-10 minutes, the second stage is 280-320℃ for 12-15 minutes, and the pressure is 5-10MPa.

[0035] Furthermore, when a tin-based preformed solder sheet is used, the thickness of the solder sheet is 0.2-0.3 mm; and soldering is performed in a formic acid furnace at 230-250° C. for 90-150 seconds.

[0036] By adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art:

[0037] First, this technical solution significantly simplifies the lead-out process of the complex frame structure in the traditional packaging process by eliminating external pins and directly welding the signal terminal module and the power terminal module to the AMB substrate; the packaging steps are simpler, and there is no need to deal with the fixing, welding and subsequent protection of a large number of pins, which reduces the process difficulty.

[0038] Second, it reduces potential failure points in traditional pin connections due to factors such as solder joints between the pins and the module, contact resistance, and mechanical stress on the pins themselves. Direct soldering enhances the robustness of the module's internal connections, improving its reliability in harsh operating environments such as vibration and temperature fluctuations, while reducing the risk of failures caused by loose connections, oxidation, and other issues.

[0039] Third, it shortens the signal transmission path and current loop, effectively reducing the module's stray inductance. For high-frequency applications, lower stray inductance can reduce electromagnetic interference and voltage spikes during switching, improve power conversion efficiency, and make the module more stable when operating at high frequencies.

[0040] Fourthly, symmetrically arranging the chip mounting area can evenly conduct heat to the substrate, avoid local overheating, and improve thermal stability; it is conducive to uniform current distribution, reduces electric field concentration, and enhances electrical reliability; it balances the module's center of gravity, disperses mechanical stress, and improves mechanical stability; it helps to reduce electromagnetic interference and enhance electromagnetic compatibility; it can also simplify the manufacturing and packaging process, improve production efficiency and product quality consistency, and thus comprehensively optimize the performance of the power module. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0042] Figure 1 This is a schematic diagram of the planar structure of the power module in the present invention;

[0043] Figure 2 Schematic diagram of the planar structure of the mounting unit in the present invention, wherein the area within the dotted line is the chip mounting area;

[0044] Figure 3 This is a schematic diagram of the planar structure of the installation unit in the present invention, wherein the area within the dotted line is the power terminal module installation area;

[0045] Figure 4 This is a schematic diagram of the planar structure of the installation unit in the present invention, wherein the area within the dotted line is the signal terminal module installation area;

[0046] Figure 5 This is a schematic diagram of the planar structure of the present invention, in which the plastic encapsulation layer is wrapped around the outside of the power module, the AMB ceramic substrate is assembled on the heat sink, and the pin needles are assembled on the signal terminal module;

[0047] In the figure: AMB ceramic substrate-1, mounting unit-2, chip mounting area-21, recessed portion-210, power terminal module mounting area-22, signal terminal module mounting area-23, metal bonding part-3, chip-4, signal terminal module-5, power terminal module-6, plastic encapsulation layer-7, pin needle-8, metal electrode-9, heat sink-10, solder-11, metal bonding wire-12. DETAILED DESCRIPTION

[0048] The present invention will be described in further detail below with reference to the accompanying drawings and examples. It is particularly noted that the following examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. Similarly, the following examples are only some embodiments of the present invention and are not intended to be exhaustive. All other embodiments obtained by those of ordinary skill in the art without creative effort are intended to fall within the scope of protection of the present invention.

[0049] like Figures 1 to 5 As shown, this solution provides a packaging method for a half-bridge plastic-encapsulated power module. Figures 1 to 5 This is a structural diagram of a half-bridge plastic-encapsulated power module.

[0050] See also Figures 1 to 5 , including: AMB ceramic substrate 1, AMB ceramic substrate 1 is made of silicon nitride or aluminum nitride, with copper cladding on both sides for module circuit etching, and ceramic material in the middle for insulation. AMB ceramic substrate 1 is provided with at least one mounting unit 2. Specifically, there are multiple mounting units 2, and multiple mounting units 2 are distributed on the AMB ceramic substrate 1. In this embodiment, the number of mounting units 2 is three, and the three mounting units 2 are arranged at intervals on the AMB ceramic substrate 1.

[0051] See Figures 1 to 5 One end surface of the mounting unit 2 is distributed with at least one chip mounting area 21 , at least one power terminal module mounting area 22 and at least one signal terminal module mounting area 23 . The chip mounting area 21 is located in the middle of the mounting unit 2 .

[0052] See Figure 3 Preferably, there are two chip mounting areas 21, which are arranged in mirror-symmetric fashion on the mounting unit 2. Chips 4 are distributed within the chip mounting areas 21. Chip mounting areas 21 are concave in shape. Chips 4 are electrically connected to the AMB ceramic substrate 1 via metal bonding wires 3. Chips 4 are third-generation wide-bandgap semiconductor chips.

[0053] See Figure 4The power terminal module mounting area 22 is located at the upper and / or lower end of the mounting unit 2. There are four power terminal module mounting areas 22, three of which are spaced apart at the upper end of the mounting unit 2, and one of which is located at the lower end of the mounting unit 2. Specifically, the power terminal module mounting area 22 at the lower end of the mounting unit 2 is symmetrical with the power terminal module mounting area 22 located in the middle of the upper end of the mounting unit 2. The power terminal module 6 is welded to the power terminal module mounting area 22. If there is only one power terminal module 6, it can be welded to any of the four power terminal module mounting areas 22. Metal electrodes 9 are provided on both the upper and lower end surfaces of the power terminal module 6. The metal electrodes 9 are either solid copper or gold-plated copper. The metal electrode 9 on one end surface of the power terminal module 6 exposed to the outside is welded to the external device to achieve an electrical connection; the metal electrode 9 on the other end surface is welded to the power terminal module mounting area 22.

[0054] See Figure 5 The signal terminal module mounting area 23 is located on the periphery of the chip mounting area 21; it also includes a signal terminal module 5 and a power terminal module 6, and the signal terminal module 5 is welded to the signal terminal module mounting area 23. There are multiple signal terminal module mounting areas 23, one of which is located above the recessed portion 210 of the concave chip mounting area 21. In this embodiment, there are four signal terminal module mounting areas 23, two of which are located above the recessed portions 210 of the two concave chip mounting areas 21, respectively, and the two signal terminal module mounting areas 23 are mirror-symmetrical; the other two signal terminal module mounting areas 23 are spaced apart along the length direction of the AMB ceramic substrate 1 at the right end of the AMB ceramic substrate 1. If there is only one signal terminal module 5, then this signal terminal module 5 can be welded to any position in the four signal terminal module mounting areas 23.

[0055] In this embodiment, one end of the signal terminal module 5 is equipped with a pin 8, which is located within the orthographic projection area of ​​the AMB ceramic substrate 1. The AMB ceramic substrate 1 and the mounting unit 2 are wrapped with a plastic layer 7. Metal electrodes 9 are provided on both the upper and lower surfaces of the signal terminal module 5. The metal electrode 9 on the upper surface of the signal terminal module 5 is welded to the pin 8, and the copper metal electrode on the lower surface of the signal terminal module 5 is welded to the signal terminal module mounting area 23.

[0056] Working principle:

[0057] When the half-bridge plastic-encapsulated power module is in operation, it first receives external control signals through the pins on the signal terminal module 5. Since the signal terminal module 5 is directly welded to the signal terminal module mounting area 23 and located on the periphery of the chip mounting area 21, it can quickly and stably transmit the control signal to the chip 4 in the chip mounting area 21, thereby controlling the conduction and cutoff of the power module and achieving efficient conversion and regulation of electrical energy. The power terminal module 6 is directly welded to the power terminal module mounting area 22 and is tightly connected to the chip 4 through an optimized layout and welding method. The electrical energy output by the chip 4 is efficiently transmitted to the external circuit to complete tasks such as power amplification and driving. The entire process is carried out under the protection of the plastic encapsulation layer, avoiding interference and damage to the internal components by the external environment. At the same time, the compact internal structure design also shortens the signal transmission path, reduces energy loss, and improves the efficiency and reliability of the power module. Moreover, since the external pins are omitted, the internal space is more rationally utilized, further improving the performance and stability of the module.

[0058] The packaging method of the above-mentioned half-bridge plastic-encapsulated power module includes the following steps:

[0059] Example 1:

[0060] S1, etching to form at least one mounting unit 2 on the surface of the AMB ceramic substrate 1, the mounting unit including: a chip mounting area 21, a power terminal module mounting area 22 and a signal terminal module mounting area 23;

[0061] The specific operations of step S1 are:

[0062] The material of AMB ceramic substrate 1 is silicon nitride (Si3N4) or aluminum nitride (AlN), with copper layer on both sides, and the thickness of the copper layer is preferably 0.2-0.3mm. Use a plasma cleaning machine to treat the surface of AMB ceramic substrate 1, parameters: argon atmosphere, power 300-500W, time 2-5 minutes, to remove organic matter and particles. Photoresist coating: spin coating positive photoresist (such as AZ4620), rotation speed 1500-2500rpm, glue thickness 5-8μm, soft baking (90℃, 3 minutes). Expose the installation unit pattern through a photomask (UV wavelength 365nm, energy 200-300mJ / cm 2 ); developer (0.5% NaOH solution) dissolves the unexposed areas to form an etching mask. Acidic etching solution (FeCl3 or H2SO4 / H2O2 system), temperature 40-50°C, etching rate 10-20μm / min.

[0063] Etching depth: The copper layer is completely etched through, exposing the ceramic insulating layer (depth = copper layer thickness ± 0.02mm);

[0064] Sidewall control: tilt angle of 70°-85° to avoid steep sidewalls that may cause a decrease in metal bonding strength;

[0065] Functional area definition (see Figure 3-5 );

[0066] Chip mounting area (21): a rectangular or concave area, the size of which matches the shape of the chip (4), with bonding space reserved at the edge;

[0067] Power terminal module mounting area (22): distributed at the edge of the AMB ceramic substrate 1, with an area ≥ 120% of the terminal electrode area;

[0068] Signal terminal module mounting area (23): surrounds the chip mounting area 21 and includes gate signal traces (line width 0.1-0.2 mm).

[0069] Glue removal and cleaning:

[0070] The photoresist was removed with acetone, ultrasonically cleaned (DI water + isopropyl alcohol), and dried with nitrogen.

[0071] Shape detection:

[0072] Laser confocal microscopy is used to check the etching depth tolerance (±5μm) to ensure there is no residual copper or over-etching.

[0073] S2. In an oxygen-free environment, the chip 4 is sintered and fixed on the chip mounting area 21. The chip sintering in step S2 includes: printing a sintered silver paste with a silver content of 88-92% on the chip mounting area 21, with a printing thickness of 80-120 μm; placing the AMB ceramic substrate 1 in an oxygen-free oven and pre-baking it at 80-120°C for 10-30 minutes to remove the solvent; introducing nitrogen into the pressure sintering furnace, applying a pressure of 0.5-1.0 MPa, and sintering at a temperature of 220-260°C for 15-25 minutes to achieve chip fixation.

[0074] The specific operations of step S2 are:

[0075] S21. Clean the stencil of the printing equipment to ensure that it is not blocked or deformed. The opening size of the stencil should match the chip mounting area 21, and the thickness should be controlled within the range of 80-120μm to ensure that the silver paste printing thickness meets the requirements.

[0076] S22. Adjust the parameters of the printing equipment: scraper angle 45°-60°, scraper pressure 20-30N / cm 2 , printing speed 20-40mm / s.

[0077] S23. Place the evenly stirred sintered silver paste on the steel mesh, start the printing equipment, and evenly print the silver paste on the chip mounting area 21. During the printing process, closely observe the distribution of the silver paste to ensure that the silver paste evenly covers the chip mounting area 21 without missing, overprinting, or unevenness.

[0078] S24. After printing is completed, use a high-precision microscope to check the printing quality of the silver paste to ensure that the thickness of the silver paste is within the range of 80-120μm, the edges are neat, and there is no obvious tailing or diffusion.

[0079] S25. Check the sealing performance of the oxygen-free oven to ensure that it can maintain an oxygen-free environment during the baking process. The oxygen content in the oven should be controlled below 10ppm. Preheat the oxygen-free oven in advance, set the temperature to 80-120℃, and wait for the temperature to stabilize. At the same time, turn on the circulation fan in the oven to ensure even temperature distribution.

[0080] S26. Place the pre-baked AMB ceramic substrate 1 together with the fixture into the sintering chamber of the pressure sintering furnace, ensuring that it is placed stably to prevent the silver paste from shifting or deforming during the sintering process. The temperature in the sintering chamber should be evenly distributed to ensure consistent sintering quality.

[0081] S27. Start the gas supply system of the pressure sintering furnace and introduce nitrogen at a flow rate of 10-15 L / min. During the ventilation process, closely observe the pressure changes in the sintering furnace to ensure that the pressure is stable within the range of 0.5-1.0 MPa.

[0082] S28. Start the heating system of the pressure sintering furnace and slowly raise the temperature to 220-260°C at a heating rate of 5-10°C / min. Maintain and sinter at this temperature for 15-25 minutes. During the sintering process, the silver particles in the silver paste diffuse and aggregate under the action of high temperature and pressure, forming a dense sintering layer, which firmly fixes the chip 4 on the chip mounting area 21. Every 5 minutes, check the sintering status through the observation window and temperature monitoring system of the sintering furnace to ensure that the temperature, pressure, and atmosphere are stable and there are no abnormal fluctuations. If any abnormality is found, adjust the sintering parameters or shut down the machine for inspection.

[0083] S29. After sintering is completed, turn off the heating system and allow the temperature in the sintering furnace to cool naturally to below 100°C. During the cooling process, continue to introduce nitrogen to maintain a stable pressure of 0.5-1.0 MPa to prevent thermal stress and damage to the chip 4 and AMB ceramic substrate 1 caused by a sudden drop in temperature. After cooling to below 100°C, slowly release the pressure in the sintering furnace to ensure that the pressure drops steadily to atmospheric pressure. Then open the sintering furnace door and remove the sintered AMB ceramic substrate 1.

[0084] S3, welding the metal electrode 9 to the power terminal module mounting area 22 and the signal terminal module mounting area 23 to achieve electrical connection with the AMB ceramic substrate 1; at the same time, welding the metal bonding part 3 to the AMB ceramic substrate 1 to achieve electrical connection with the AMB ceramic substrate 1; electrically connecting the gate of the chip 4 to the signal terminal on the surface of the AMB ceramic substrate 1 through the metal bonding wire 3; specifically, the welding of the metal electrode 9 in step S3 includes: using a metal electrode 9 with a thickness of 0.3-0.5mm, welding at a temperature of 180-220℃ in a formic acid welding furnace; maintaining the formic acid gas concentration at 200-500ppm, and controlling the welding time to 60-120 seconds to form an electrical connection between the metal electrode 9 and the AMB ceramic substrate 1. In step S3, the gate of the chip 4 is electrically connected to the signal terminal on the surface of the AMB ceramic substrate 1 through the metal bonding wire 3, specifically including: using an aluminum wire bonding machine to bond the gate of the chip 4 to the AMB ceramic substrate 1.

[0085] The specific operations of step S3 are:

[0086] S31. Preheat the formic acid soldering furnace to the set temperature, ensuring it remains stable within the range of 180-220°C. Start the formic acid gas supply in advance and adjust the concentration to 200-500 ppm. Also, prepare the necessary tools for soldering, such as fixtures, tweezers, and soldering irons. Ensure soldering is performed in a dust-free, oil-free, and water-free environment, with a temperature of 20-25°C and a humidity of 40%-60%. Keep the workbench clean and stable to avoid vibration that could affect the soldering process.

[0087] S32. Use tweezers to place the metal electrodes 9 on the power terminal module mounting area 22 and the signal terminal module mounting area 23, respectively, ensuring that the contact surface between the soldering pads and the mounting areas is flat and well-fitted. Note that the soldering pads must be positioned accurately to avoid offset or skew to ensure a reliable connection after soldering.

[0088] S33. Place the AMB ceramic substrate 1 with the metal electrodes 9 placed on it, along with the fixture, into a formic acid soldering furnace for preheating. The preheating temperature is controlled at 150-170°C for 2-3 minutes. This process helps the solder pad and mounting area to heat up slowly, reducing the impact of thermal stress on the material. Simultaneously, the formic acid gas begins to reduce the surface of the solder pad, removing surface oxides and improving the solderability of the pad.

[0089] S34. After preheating is complete, continue heating to 180-220°C at a rate of 5-8°C / min. At this temperature, the formic acid gas continuously reduces the surface of the solder pad, preventing oxidation of the metal surface. Continue soldering for 60-120 seconds, adjusting the specific time based on the thickness and material of the solder pad, as well as the actual performance of the soldering furnace, to ensure that the solder pad is fully melted and forms a good metallurgical bond with the AMB ceramic substrate 1, achieving an electrical connection.

[0090] S35. During the soldering process, apply appropriate pressure to the soldering lug using the soldering furnace's pressure head or a dedicated fixture, within a range of 0.5-1.0 MPa, to ensure a close fit between the lug and the mounting area, promoting solder flow and filling. Simultaneously, use a thermometer and pressure sensor to monitor temperature and pressure changes during the soldering process in real time, ensuring that the parameters remain stable within the set range to ensure soldering quality.

[0091] S36. After welding is completed, slowly cool the welding furnace to room temperature at a cooling rate of 3-6°C / min. During the cooling process, continue to introduce formic acid gas or cover with inert gas to prevent the weld from being oxidized at high temperatures.

[0092] S37. After cooling, inspect the appearance of the welded parts to check for defects such as cold joints, leaking solder, excessive or insufficient solder, etc. Use a magnifying glass or microscope to observe the surface quality of the solder joints. The solder joints should be smooth and round, without obvious pores, cracks, or inclusions.

[0093] S38. Mount the chip 4 on the chip mounting area 21, ensuring that the chip 4 is positioned accurately and corresponds to the signal terminals on the surface of the AMB ceramic substrate 1. Use a high-precision positioning device or an optical alignment system to check the relative position of the chip 4 and the signal terminals, ensuring that their position accuracy is within the range of ±0.05mm.

[0094] S39. Start the aluminum wire bonding machine and secure one end of the metal bonding wire 3 to the gate of chip 4 and the other end to the signal terminal on the surface of the AMB ceramic substrate 1. During the bonding process, the welding head of the aluminum wire bonding machine acts on the metal bonding wire 3 at a set frequency and pressure to ensure that the metal bonding wire 3 forms a solid bond with the gate and signal terminals of chip 4. The bonding points should be evenly distributed, with no empty bonds or missed bonds, and the curvature of the bonding wire should be natural, without obvious distortion or stretching.

[0095] S4. Weld the power terminal module 6 and the signal terminal module 5 to the metal electrodes 6 of the corresponding mounting areas. Specifically, in step S4, the power terminal module 6 is welded using a preformed solder sheet with a copper content ≥ 99.9%, and the welding is carried out at 250-280°C in a formic acid reducing atmosphere for 30-60 seconds, with a solder layer thickness of 50-100 μm.

[0096] The specific operations of step S4 are:

[0097] S41. Select a preformed solder sheet with a copper content of ≥99.9% and a thickness of 0.2-0.3 mm. Cut it according to the size and shape of the power terminal module 6 and the signal terminal module 5 to ensure that the contact area between the solder sheet and the module and the metal electrode 6 is appropriate to achieve good electrical connection and mechanical fixation.

[0098] S42. Place the cut preformed solder sheets on the soldering surfaces of the power terminal module 6 and the signal terminal module 5, as well as on the metal electrodes 6 in the corresponding mounting areas. Ensure that the solder sheets are placed accurately to avoid offset or skew to ensure connection reliability after soldering.

[0099] S43. Place the components with the soldering pieces and modules in a formic acid furnace with a formic acid reducing atmosphere for preheating. The preheating temperature is controlled at 200-230°C for 1-3 minutes. The soldering pieces and modules are heated up slowly to reduce the impact of thermal stress on the materials. At the same time, the formic acid gas begins to reduce the surface of the soldering pieces to remove surface oxides and improve the solderability of the soldering pieces.

[0100] After preheating, continue heating to 250-280°C at a rate of 5-10°C / min to ensure uniform heating of the solder pads and avoid local overheating that could cause uneven solder melting or damage the module. During the heating process, a formic acid reducing atmosphere is continuously applied to further ensure the cleanliness and activity of the solder pad surface.

[0101] S45. Maintain the temperature at 250-280°C for 30-60 seconds to fully melt the solder and wet the surfaces of the power terminal module 6, signal terminal module 5, and the metal electrodes 6 in the corresponding mounting areas, achieving a good metallurgical bond. Simultaneously, control the atmosphere in the welding area to prevent oxygen from entering and causing re-oxidation of the welded area, thereby ensuring welding quality.

[0102] S46. After welding is completed, slowly cool the formic acid furnace to room temperature at a cooling rate of 3-8°C / min. The welded parts will gradually solidify during the cooling process, forming a stable electrical connection and mechanical structure. During the cooling process, the welded parts can be properly protected, such as covered with inert gas, to prevent oxidation at high temperatures.

[0103] S47. After cooling, inspect the appearance of the welded parts to check for defects such as cold joints, leaking welds, excessive or insufficient solder, etc. If necessary, clean the welded parts with specialized tools to remove excess solder or impurities. Ensure that the connection surfaces between the power terminal module 6 and the signal terminal module 5 and the metal electrode 6 are smooth and flat, without any residue that could affect electrical performance and mechanical strength.

[0104] S48. The signal terminal module 5 can be welded using a similar process as the power terminal module 6. However, since the size and shape of the signal terminal module 5 may differ from those of the power terminal module 6, the size and shape of the soldering tabs, as well as the welding parameters, need to be adjusted based on the actual situation. Generally, the welding temperature of the signal terminal module 5 can be slightly lower than that of the power terminal module 6, and the holding time can be shortened accordingly, but the welding quality must be ensured to meet the requirements.

[0105] S5, welding the metal electrode 6 to the end surface of the power terminal module 6 and the signal terminal module 5 facing away from the AMB ceramic substrate 1;

[0106] The specific operations of step S5 are:

[0107] S51. Carefully inspect the end surfaces of the power terminal module 6 and the signal terminal module 5 facing away from the AMB ceramic substrate 1, as well as the surface of the metal electrode 6, to ensure they are clean and free of oxides, oil, dust, and other impurities. If necessary, clean them with an appropriate detergent and blow dry them with nitrogen. Also, inspect the size, shape, and specifications of the metal electrode 6 to ensure they meet the requirements, and to check for surface defects such as scratches and cracks.

[0108] S52: Prepare solder suitable for soldering the metal electrodes 6, such as tin-silver solder with a silver content of 2-3%, which has good soldering performance and electrical conductivity. Cut the solder into solder pieces or solder wires of appropriate sizes for subsequent use.

[0109] S53. Preheat the formic acid soldering furnace to the set temperature, usually 180-220°C, and ensure that the formic acid gas concentration is maintained at 200-500 ppm to provide a good reducing atmosphere during the soldering process and prevent oxidation of the metal surface. At the same time, prepare the necessary soldering tools such as clamps, tweezers, and soldering iron, and ensure they are in good working condition.

[0110] S54. Place the prepared solder sheet or wire on the end surface of the power terminal module 6 and the signal terminal module 5 facing away from the AMB ceramic substrate 1. Ensure that the solder is positioned accurately and in close contact with the end surface. Then, align the metal electrode 6 above the solder, ensuring that the metal electrode 6 is aligned with the solder and the center of the end surface to avoid deviation or skew.

[0111] S55. Place the components with the solder and metal electrode 6 in a formic acid soldering furnace for preheating. The preheating temperature is controlled at 150-180°C for 1-2 minutes. The solder and metal electrode 6 are heated slowly to reduce the impact of thermal stress on the material. At the same time, the formic acid gas begins to reduce the metal surface to remove surface oxides and improve welding performance.

[0112] S56. After preheating is complete, continue heating to 180-220°C at a rate of 5-8°C / min to ensure uniform heating of the solder and avoid local overheating that may cause uneven solder melting or damage to the metal electrode 6. During the heating process, closely observe the state of the solder. When the solder begins to melt, adjust the temperature and time appropriately to ensure that the solder is fully melted and wets the metal electrode 6 and the end surface.

[0113] S57. Maintain the temperature at 180-220°C for 30-60 seconds to ensure that the solder is completely melted and forms a good metallurgical bond with the metal electrode 6 and the end face. At the same time, use an appropriate tool to gently press the metal electrode 6 to ensure a tight bond with the solder. However, be careful not to apply excessive pressure to avoid damaging the metal electrode 6 or the module.

[0114] S58. After welding is completed, slowly cool the welding furnace to room temperature at a cooling rate of 3-6°C / min. This allows the welded parts to gradually solidify during the cooling process, forming a stable electrical connection and mechanical structure. During the cooling process, formic acid gas can continue to be introduced or an inert gas can be covered to prevent the welded parts from being oxidized at high temperatures.

[0115] S59. After cooling, inspect the appearance of the welded parts to check for defects such as cold joints, leaking solder, excessive or insufficient solder, etc. If necessary, clean the welded parts with specialized tools to remove excess solder or impurities. Ensure that the connection surfaces between the metal electrode 6 and the power terminal module 6 and signal terminal module 5 are smooth and flat, without any residue that could affect electrical performance and mechanical strength.

[0116] S510: The signal terminal module 5 can be soldered using a similar process as the power terminal module 6. However, since the size and shape of the signal terminal module 5 may differ from those of the power terminal module 6, the amount of solder and soldering parameters may need to be adjusted based on the actual situation. Generally, the soldering temperature of the signal terminal module 5 can be slightly lower than that of the power terminal module 6, and the holding time can be shortened accordingly, but the soldering quality must be ensured to meet the requirements.

[0117] S6. Injection molding is performed on the outside of the AMB ceramic substrate 1 and the mounting unit 2 to form a plastic layer 7, exposing only the end face of the metal electrode 6 of the power terminal module 6 and the end face of the metal electrode 6 of the signal terminal module 5; specifically, the molding of the plastic layer 7 in step S6 includes: injection molding using epoxy molding compound at a pressure of 8-12 MPa and a temperature of 165-180°C, with a curing time of 3-5 minutes; after plastic molding, laser polishing is performed to remove overflow, with a laser power of 50-80 W and a scanning interval of 0.1-0.3 mm.

[0118] The specific operations of step S6 are:

[0119] S61. Preheat the injection mold to 100-120℃ to make the mold temperature uniform, which helps to improve the fluidity and filling performance of the epoxy molding compound and reduce the internal stress caused by temperature difference.

[0120] S62. Set the injection molding machine temperature to 165-180°C and the pressure to 8-12 MPa to ensure that the epoxy molding compound can fully flow and fill the mold cavity under high temperature and pressure, forming a complete plastic encapsulation layer 7. At the same time, adjust the injection molding machine's screw speed and injection speed to match the mold filling requirements.

[0121] S63. Carefully place the welded power module in the cavity of the injection mold to ensure that the power module is positioned accurately and aligned with the positioning device of the mold to avoid displacement or deformation during the injection molding process.

[0122] S64. Start the injection molding machine and inject the epoxy molding compound into the mold cavity. The injection pressure is controlled at 8-12 MPa and the injection temperature is controlled at 165-180°C. During the injection molding process, closely observe the flow of the epoxy molding compound to ensure that it can evenly fill the entire cavity and wrap the exterior of the AMB ceramic substrate 1 and the mounting unit 2, while avoiding damage or contamination to the end faces of the metal electrodes 6 of the power terminal module 6 and the signal terminal module 5.

[0123] S65. After injection molding is complete, the mold is maintained at a temperature of 165-180°C for curing for 3-5 minutes. During the curing process, the epoxy molding compound undergoes a chemical reaction to form a hard plastic layer 7, which tightly encapsulates the internal components of the power module and provides good electrical insulation and mechanical protection.

[0124] S66. Prepare the laser polishing equipment, ensuring that the laser power is adjustable within the range of 50-80W and the scanning pitch is set between 0.1-0.3mm. Meanwhile, install the appropriate laser focusing and scanning mirrors, and adjust the optical path of the equipment to ensure that the laser beam is well focused and can accurately act on the surface of the plastic encapsulation layer 7.

[0125] S67. Place the cured power module on the workbench of the laser polishing equipment and adjust the module's position so that the laser beam can accurately illuminate the overflow area on the surface of the plastic coating layer 7. Set the laser power to 50-80W and the scanning interval to 0.1-0.3mm. According to the thickness and hardness of the overflow, appropriately adjust the laser scanning speed and number of reciprocating strokes to polish and remove the overflow layer by layer. During the polishing process, pay attention to the condition of the plastic coating layer 7 surface to avoid excessive polishing that may damage the plastic coating layer 7 surface or accidentally damage the end face of the metal electrode 6.

[0126] S68. After laser polishing to remove the overflow, use compressed air or nitrogen to purge the module surface to remove dust and debris generated by polishing. Then, inspect the surface of the plastic encapsulation layer 7 to ensure that it is smooth and flat, without obvious scratches, pits, or residue, and that the end faces of the metal electrodes 6 of the power terminal module 6 and the signal terminal module 5 are fully exposed without any obstruction or contamination.

[0127] S7. Solder the pin 8 to the metal electrode 6 of the signal terminal module 5 using ultrasonic pin welding equipment. The metal electrode 6 to which the pin 8 is welded is exposed, and during actual production, a portion may be exposed outside the plastic layer 7. Specifically, the pin 8 welding in step S7 includes: laser cleaning the metal electrode 9 of the signal terminal module 5 to remove oxides on the surface of the metal electrode 9, using a laser wavelength of 322-355nm, a power of 20-40W, and a scanning speed of 100-200mm / s; and using ultrasonic welding equipment at a frequency of 60-100kHz and a pressure of 0.5-1.0N to weld the pin 8 to the center of the metal electrode 9, with a tolerance of ±0.1mm.

[0128] The specific operations of step S7 are:

[0129] S71. Place the signal terminal module 5 on the workbench of the laser cleaning equipment to ensure that it is firmly fixed and will not be displaced during the cleaning process.

[0130] S72. Turn on the laser cleaning equipment, set the laser wavelength to 322-355nm, power to 20-40W, and scanning speed to 100-200mm / s.

[0131] S73. After cleaning, use a magnifying glass or microscope to check the cleanliness of the surface of the metal electrode 9 to ensure that there is no residual oxide, scratches, or damage on the surface. If necessary, the cleaning process can be repeated until the surface reaches the desired clean state.

[0132] S74. Place the cleaned signal terminal module 5 on the workbench of the ultrasonic welding equipment to ensure it is firmly fixed. Use tweezers to pick up the pin 8 and place it directly above the metal electrode 9 of the signal terminal module 5. Note that the insertion depth of the pin 8 should be controlled within 1 / 2 to 2 / 3 of the thickness of the metal electrode 9 to ensure the connection strength and electrical performance after welding.

[0133] S75. Before welding, perform equipment debugging to ensure that the ultrasonic welding equipment's welding head is in good contact with pin 8 and that the pressure is moderate. The welding head should be perpendicular to the surface of pin 8 to ensure uniform energy transfer during welding and avoid unstable welding quality due to poor contact.

[0134] S76. Start the ultrasonic welding equipment and weld pin 8 to the center of metal electrode 9. During welding, the ultrasonic welding equipment applies force to pin 8 at a frequency of 60-100 kHz and a pressure of 0.5-1.0 N. The welding time is controlled within 10-20 ms, and the amplitude is controlled within 20-40 μm. During welding, the argon shielding device continuously provides argon protection to prevent oxidation of the metal at high temperatures.

[0135] S77. Use a magnifying glass or microscope to inspect the appearance of the welded area to check whether the pin 8 is perpendicular to the surface of the metal electrode 9 and whether the surface of the weld is smooth and free of defects such as cracks, pores, cold solder joints, and leaks. Measure the deviation between the welded position of the pin 8 and the designed position to ensure that its position accuracy is within ±0.1mm. Use appropriate tensile testing equipment to perform a tensile test on the welded pin 8 to ensure that its weld strength meets the requirements. The general tensile force should be ≥10N. Use electrical testing equipment such as a multimeter to measure the electrical conductivity between the welded pin 8 and the signal terminal module 5 to ensure that its resistance is ≤10mΩ and the insulation resistance is ≥100MΩ to verify that the electrical performance after welding meets the requirements. If the test results do not meet the requirements, the welding operation must be repeated until the qualified standards are met.

[0136] S8. Assemble the encapsulated power module onto heat sink 10. Heat sink 10 is a metal heat sink used to transfer heat from the power module to the outside world. Specifically, assembling heat sink 10 in step S8 includes: printing solder on the surface of heat sink 10. The solder is sintered silver, sintered copper, or tin solder. The printing thickness is 150-200μm; and sintering is performed in a stepwise manner: the first stage is 150°C for deoxidation for 8-10 minutes, and the second stage is sintering at 280-320°C for 12-15 minutes at a pressure of 5-10MPa.

[0137] The specific operations of step S8 are:

[0138] S81. According to the size of the heat sink 10 and the characteristics of the solder, set the parameters of the printing equipment, the scraper angle is 45-60 degrees, and the scraper pressure is 20-30N / cm 2 , the printing speed is 20-40mm / s to ensure that the solder can be evenly printed on the surface of the heat sink.

[0139] S82. Place the heat sink 10 on the workbench of the printing equipment to ensure that it is firmly fixed and will not be displaced or shaken during the printing process, thereby affecting the printing quality.

[0140] S83. Start the printing equipment and print the solder evenly on the surface of the heat sink 10. The printing thickness is controlled at 150-200 μm. During the printing process, closely observe the distribution of the solder to ensure that the solder is evenly covered in the soldering area of ​​the heat sink 10 without missing, overprinting, or unevenness.

[0141] S84. Place the plastic-sealed power module on the heat sink 10. Use a positioning fixture or a visual positioning system to accurately align the module's installation position based on the positioning marks on the power module and the heat sink 10, so that the power module's mounting holes are aligned with the positioning holes on the heat sink 10.

[0142] S85. Carefully place the power module on the heat sink 10, ensuring that the module is parallel to the heat sink 10 and avoiding tilting or twisting. At the same time, check the gap between the power module and the heat sink 10 to ensure that the gap is uniform and does not affect the welding quality.

[0143] S86. Place the heat sink 10 with the power module mounted on it into the sintering equipment and slowly heat it to 150°C at a rate of 5-10°C / min. Maintain the temperature at 150°C ± 5°C and perform a deoxidation treatment for 8-10 minutes. This process uses a relatively low temperature to initially activate the solder, enhancing its fluidity. It also removes adsorbed moisture and some volatile impurities from the solder and the soldering surface, creating favorable conditions for subsequent sintering.

[0144] S87. After deoxidation is completed, continue to heat up to 280-320°C at a heating rate of 10-15°C / min. Within this temperature range, maintain the temperature stable at the set value ±5°C according to the melting point and characteristics of the solder, and perform sintering for 12-15 minutes. During this process, the solder fully melts and wets the contact surface of the heat sink 10 and the power module, forming a good metallurgical bond. During the sintering process, the atmosphere in the sintering equipment must be kept stable. Usually, an inert gas protection (such as nitrogen or argon) is used, and the gas flow rate is controlled at 10-20L / min to prevent the solder from oxidizing at high temperatures.

[0145] S88. Throughout the sintering process, apply a pressure of 5-10 MPa. This pressure must be evenly distributed across the soldering area between the power module and heat sink 10 to ensure that the molten solder fully fills the small gap between them, enhancing soldering reliability and thermal conductivity. Pressure can be applied using a pressure head or specialized fixture on the sintering equipment. A pressure sensor must be used to monitor pressure changes in real time and ensure that the pressure remains stable within the set range.

[0146] S89. After sintering is complete, turn off the heating system and allow the sintering equipment and the power module and heat sink 10 components therein to cool naturally to room temperature under inert gas protection. The cooling rate must be controlled to ≤10°C / min during the cooling process to avoid thermal stress caused by excessive temperature differences, which could cause deformation or cracking of the power module or heat sink, affecting welding quality and module performance.

[0147] When the half-bridge plastic-encapsulated power module needs to be installed on an external device, the signal terminal module 5 is assembled and fixed to the external device through the pin needle 8, and the power terminal module 6 is welded and fixed to the metal electrode of the external device through the metal electrode 9 exposed outside the plastic layer 7.

[0148] Implementation 2:

[0149] The difference from the first embodiment is that in step S8, when a tin-based preformed solder sheet is used, the thickness of the solder sheet is 0.2-0.3 mm; and soldering is performed in a formic acid furnace at 230-250° C. for 90-150 seconds.

[0150] S81. Select a tin-based preform with a thickness of 0.2-0.3mm. Ensure it meets relevant standards and is free of impurities, oxidation, and deformation. Ensure that its dimensions match the soldering area of ​​the heat sink and power module. Check that the surface of the preform is flat and smooth, free of scratches, pits, and other defects. Ensure that the edges are neat and free of burrs and defects to ensure soldering quality.

[0151] S82. Use a clean cloth dipped in an appropriate amount of isopropyl alcohol to gently wipe the surface of the solder pad to remove dust, oil, and other impurities. Be gentle when wiping to avoid scratching the surface of the solder pad.

[0152] S83. Check the surface of the heat sink 10 again to ensure it is clean, dry, and free of oxides. If necessary, perform plasma cleaning or chemical cleaning to enhance the adhesion of the solder. For heat sinks 10 with larger areas, automatic cleaning equipment can be used for batch processing to improve efficiency and cleaning effect.

[0153] S84. Verify that the plastic encapsulation layer 7 of the power module is intact, free of cracks and chippings, that the metal electrodes 9 are free of oxidation and contamination, and that the installation dimensions meet design requirements. Check that the contact surface between the power module and the heat sink 10 is flat. If necessary, perform light grinding or polishing to ensure good thermal contact.

[0154] S85. Evenly place tin-based preforms on the soldering area of ​​the heat sink 10, ensuring that the preforms are evenly attached to the surface of the heat sink 10 without wrinkles or bubbles. A dedicated positioning fixture or optical alignment system can be used to assist in the placement of the preforms, improving accuracy and efficiency.

[0155] S86. Place the power module on the heat sink 10. Use a visual positioning system or a mechanical alignment device to accurately align the installation positions of the power module and the heat sink 10 to ensure that the relative position deviation between the two is controlled within ±0.2mm to ensure the contact effect and thermal conductivity after welding.

[0156] S87. Set the formic acid furnace temperature to 230-250°C, preheat, and stabilize the temperature. Set the soldering time to 90-150 seconds, optimizing the time within this range based on factors such as solder pad thickness and power module size. Ensure the furnace atmosphere is uniform and stable, with the formic acid concentration controlled between 300-500 ppm to provide a favorable reducing environment and prevent solder oxidation.

[0157] S88. During the soldering process, monitor the temperature and atmosphere in the formic acid furnace in real time to ensure that temperature fluctuations do not exceed ±5°C and that the formic acid gas concentration is stable. Observe the melting and flow of the solder to ensure that the solder evenly fills the gap between the power module and the heat sink, forming a good solder connection. If any abnormality is detected, adjust the soldering parameters or shut down the machine for inspection to ensure soldering quality.

[0158] S89. After soldering is complete, turn off the heating system and allow the power module and heat sink 10 assembly to cool naturally to room temperature in the formic acid furnace. During the cooling process, maintain a stable atmosphere in the furnace to avoid thermal stress in the soldering area due to large temperature differences, which could affect soldering quality.

[0159] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A packaging method for a half-bridge plastic-encapsulated power module, characterized in that: The following steps are involved: S1, etching to form at least one mounting unit (2) on the surface of an AMB ceramic substrate (1), wherein the mounting unit comprises: a chip mounting area (21), a power terminal module mounting area (22), and a signal terminal module mounting area (23); S2. In an oxygen-free environment, sintering and fixing the chip (4) on the chip mounting area (21); S3, welding the metal electrode (9) to the power terminal module mounting area (22) and the signal terminal module mounting area (23) to achieve electrical connection with the AMB ceramic substrate (1); at the same time, welding the metal bonding member (3) to the AMB ceramic substrate (1) to achieve electrical connection with the AMB ceramic substrate (1); electrically connecting the gate of the chip (4) to the signal terminal on the surface of the AMB ceramic substrate (1) through the metal bonding wire (3); S4, welding the power terminal module (6) and the signal terminal module (5) to the metal electrodes (6) of the corresponding mounting areas; S5, welding the metal electrode (6) to one end surface of the power terminal module (6) and the signal terminal module (5) facing away from the AMB ceramic substrate (1); S6, forming a plastic encapsulation layer (7) by injection molding outside the AMB ceramic substrate (1) and the mounting unit (2), exposing only the end surface of the metal electrode (6) of the power terminal module (6) and the end surface of the metal electrode (6) of the signal terminal module (5); S7, soldering the pin needle (8) to the metal electrode (6) of the signal terminal module (5); S8, assembling the plastic-sealed power module onto the heat sink (10).

2. The packaging method of a half-bridge plastic-encapsulated power module according to claim 1, wherein: The chip sintering in step S2 includes: Printing a sintered silver paste with a silver content of 88-92% in the chip mounting area (21) with a printing thickness of 80-120 μm; Pre-baking the AMB ceramic substrate (1) in an oxygen-free oven at 80-120° C. for 10-30 minutes to remove the solvent; Introduce nitrogen into the pressure sintering furnace, apply a pressure of 0.5-1.0 MPa, and sinter at a temperature of 220-260° C. for 15-25 minutes to fix the chip.

3. The packaging method of a half-bridge plastic-encapsulated power module according to claim 1, wherein: The metal electrode (9) is a full copper metal electrode or a full copper gold-plated metal electrode.

4. A packaging method for a half-bridge plastic-encapsulated power module according to claim 1 or 3, characterized in that: The welding of the metal electrode (9) in step S3 includes: A metal electrode (9) with a thickness of 0.3-0.5 mm is used for welding at a temperature of 180-220° C. in a formic acid welding furnace; The formic acid gas concentration is maintained at 200-500 ppm, and the welding time is controlled at 60-120 seconds to form an electrical connection between the metal electrode (9) and the AMB ceramic substrate (1).

5. The packaging method of a half-bridge plastic-encapsulated power module according to claim 1, wherein: In step S3, the gate of the chip (4) is electrically connected to the signal terminal on the surface of the AMB ceramic substrate (1) via the metal bonding wire (3), specifically comprising: An aluminum wire bonding machine is used to bond the chip (4) gate and the AMB ceramic substrate (1).

6. The packaging method of a half-bridge plastic-encapsulated power module according to claim 1, wherein: In the step S4, the power terminal module (6) is welded using a preformed welding sheet with a copper content of ≥99.9%, and is welded at 250-280° C. in a formic acid reducing atmosphere for 30-60 seconds, with a welding layer thickness of 50-100 μm.

7. The packaging method of a half-bridge plastic-encapsulated power module according to claim 1, wherein: The molding of the plastic sealing layer (7) in step S6 includes: Use epoxy molding compound for injection molding at a pressure of 8-12 MPa and a temperature of 165-180°C, with a curing time of 3-5 minutes; After plastic sealing, laser polishing is used to remove overflow, with a laser power of 50-80W and a scanning interval of 0.1-0.3mm.

8. The packaging method of a half-bridge plastic-encapsulated power module according to claim 1, wherein: The pin (8) welding in step S7 includes: Laser cleaning is performed on the metal electrode (9) of the signal terminal module (5) to remove oxides on the surface of the metal electrode (9), with a laser wavelength of 322-355 nm, a power of 20-40 W, and a scanning speed of 100-200 mm / s; Ultrasonic welding equipment is used to weld the pin (8) to the center of the metal electrode (9) at a frequency of 60-100 kHz and a pressure of 0.5-1.0 N, with a tolerance of ±0.1 mm.

9. The packaging method of a half-bridge plastic-encapsulated power module according to claim 1, wherein: The heat sink (10) assembly in step S8 includes: Printing solder on the surface of the heat sink (10) with a printing thickness of 150-200 μm; Sintering is carried out by step-by-step heating: the first stage is 150℃ for deoxidation for 8-10 minutes, the second stage is 280-320℃ for 12-15 minutes, and the pressure is 5-10MPa.

10. The packaging method of a half-bridge plastic-encapsulated power module according to claim 9, characterized in that: When a tin-based preformed solder sheet is used, the thickness of the solder sheet is 0.2-0.3 mm; soldering is performed in a formic acid furnace at 230-250° C. for 90-150 seconds.

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