A sealing method for IGBT module

Abstract

The present invention provides a sealing method for an IGBT module, relating to the technical field of IGBT module packaging structures. The present invention comprises the following steps: S1, the lower portion of the enclosure is fixedly connected to the base plate in an airtight manner; S2, encapsulating a bottom sealing layer in the cavity formed by the enclosure and the base plate; S3, encapsulating a stabilizing layer on the bottom sealing layer in the cavity; S4, encapsulating a top reinforcement layer on the stabilizing layer in the cavity; S5, fixing the upper portion of the enclosure to the cover plate. By using the sealing technology for IGBT modules, when the IGBT module is used in a low-pressure environment, although there is an air pressure difference between the inside and outside of the sealing structure, the phenomenon of partial discharge of microbubbles under the action of a high-voltage electric field will not occur, and the aging and decomposition of the organic insulating encapsulation body will not be caused, thereby effectively improving the reliability of the IGBT module.

Description

Technical Field

[0001] The present invention relates to the technical field of IGBT module packaging structures, and in particular to a sealing method for an IGBT module. Background Art

[0002] IGBT modules, with their high-voltage and high-current surge resistance and high switching frequency characteristics, have been widely used in the railway transportation industry. Due to their excellent performance, they are increasingly favored in aerospace applications such as rockets and missiles. IGBT modules are potted with silicone gel to improve the device's insulation properties, prevent partial discharge, and protect chip components and aluminum bonding wires.

[0003] In the prior art, IGBT modules are non-airtight packages. Because the interfaces between the module's internal electrodes and the frame, the frame and the base plate, and the chip assembly and the substrate are not completely sealed, tiny gaps exist. The potting compound cannot completely penetrate these tiny gaps, resulting in tiny enclosed spaces within the potting body. When used on the ground, the presence of the tiny enclosed space within the IGBT module does not cause any usage problems. However, when used in a low-voltage environment, a pressure difference will form inside and outside the tiny enclosed space, causing the tiny enclosed space to gradually release gas to the outside, thereby causing the potting body to deform and form microbubbles. Microbubbles will produce local discharges under the action of a high-voltage electric field. Long-term and continuous local discharges will cause the organic insulating potting body to gradually age and decompose, damaging the walls of adjacent microbubbles to form larger air gaps, which in turn causes greater local discharges. As the local discharge energy continues to increase, the insulating properties of the potting body are eventually lost, causing the IGBT module to fail. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a sealing method for an IGBT module which can achieve no bubble generation in a potting body under a low-pressure environment, thereby making the IGBT module reliable for use under a low-pressure environment.

[0005] The sealing method for an IGBT module provided by the present invention comprises the following steps:

[0006] S1. The lower part of the frame is fixedly bonded to the base plate in an airtight manner;

[0007] S2. Potting the bottom sealing layer in the cavity formed by the frame and the bottom plate;

[0008] S3. In the cavity, encapsulating a stabilizing layer on the bottom sealing layer;

[0009] S4. In the cavity, encapsulating a top reinforcement layer on the stabilizing layer;

[0010] S5. Fix the upper portion of the frame to the cover plate.

[0011] The IGBT module involved in the present invention includes:

[0012] A surrounding frame, wherein the lower portion of the surrounding frame is fixedly connected to the periphery of the bottom plate, and the surrounding frame and the bottom plate form a cavity;

[0013] a cover plate fixedly connected to the upper portion of the surrounding frame;

[0014] Separate copper-clad substrates are welded to the upper surface of the base plate;

[0015] A chip assembly and a terminal, wherein the fixed ends of the chip assembly and the terminal are respectively welded to the copper-clad substrate, wherein the free end of the terminal extends out of the cover plate opening;

[0016] Metal bonding wires are welded between the upper surfaces of the separated copper-clad substrates, and metal bonding wires are welded between the chip components;

[0017] The enclosure and base plate are connected in an airtight manner to form a cavity. The potting compound poured into the cavity is divided into three layers. By completely housing the IGBT module within the potting compound, the IGBT module is placed in an airtight, sealed structure. Because the sealed structure is free of gas, the interior of the IGBT module is protected from the effects of the external low-pressure environment. In a low-pressure environment, gas trapped in the tiny, enclosed spaces formed by the tiny gaps between the IGBT module's terminals and the enclosure, the enclosure and base plate, and the chip assembly and substrate will not escape into the potting compound.

[0018] According to one aspect of the present invention, the ratio of the hardness of the bottom sealing layer to the stabilization layer to the top reinforcement layer is (2-3):1:(2-3);

[0019] The bottom sealing layer contains all the chip components. The stabilization layer is located on top of the bottom sealing layer and contains all the metal bonding wires. The top reinforcement layer is located on top of the stabilization layer. The three layers have different hardnesses. Specifically, the stabilization layer is harder than the bottom sealing layer and the top reinforcement layer. The softer stabilization layer does not exert compressive stress on the metal bonding wires and can protect them. Because the IGBT module generates heat during operation in a low-voltage environment, the bottom sealing layer and the top reinforcement layer have a certain hardness to effectively prevent the stabilization layer from expanding due to the influence of air pressure and temperature.

[0020] According to one aspect of the present invention, the bottom sealing layer is cured silicone rubber; the stabilizing layer is cured silicone gel; and the top reinforcement layer is cured silicone rubber or epoxy glue.

[0021] Silicone rubber has high elasticity and can better solve the thermal mismatch problem between the base plate, the surrounding frame, and the adhesive between the base plate and the surrounding frame.

[0022] According to one aspect of the present invention, the following steps are performed before step S1:

[0023] S1a. Degassing the silicone rubber, the silicone gel, and the epoxy adhesive under a vacuum environment.

[0024] The silicone rubber, the silicone gel and the epoxy adhesive forming the potting body are subjected to a vacuum degassing treatment to eliminate microbubbles. When the IGBT module is used in a low-pressure environment, although there is an air pressure difference inside and outside the sealing structure, local discharge of microbubbles under the action of a high-voltage electric field will not occur, and aging and decomposition of the organic insulating potting body will not be caused, thereby improving the reliability of the IGBT module.

[0025] According to one aspect of the present invention, in step S1, epoxy glue is used to fix and bond the lower portion of the frame to the bottom plate;

[0026] The ratio of the thermal expansion coefficient of the frame to the thermal expansion coefficient of the epoxy adhesive is (0.8-1.2):1.

[0027] In the concept of the present invention, the epoxy adhesive used to bond the lower part of the frame and the bottom plate has a bonding strength greater than 10N / mm 2 , so that the bottom plate and the frame form a good bonding strength, effectively preventing gas circulation. In this step, you can use epoxy glue that has not been vacuum degassing treated.

[0028] The thermal expansion coefficient of the frame material should preferably be close to that of the epoxy adhesive. When the IGBT module is heated, the frame and the epoxy adhesive maintain essentially the same expansion ratio, eliminating any gaps between them and ensuring an airtight connection between the epoxy adhesive and the frame.

[0029] According to one aspect of the present invention, in step S2, the silicone rubber is potted in the lower part of the cavity until the bottom sealing layer is higher than the chip assembly, and the silicone rubber is allowed to stand for 1 minute to solidify, wherein the potting process is carried out in a 0.1 mbar vacuum environment.

[0030] According to one aspect of the present invention, in step S3, the silicone gel is mixed in a piston-type static mixer, and the potting process is performed in a 0.1 mbar vacuum environment. The steps of potting the stabilization layer are as follows:

[0031] S31, filling the cavity with the silicone gel occupying 1 / 4 of the cavity height and covering all metal bonding wires, and letting it stand for 2 minutes to 5 minutes;

[0032] S32, continue to pot the silicone gel until the upper surface of the silicone gel is 1.5 mm to 5 mm away from the upper surface of the frame, and let it stand for 1.5 minutes;

[0033] S33, solidifying the silicone gel in the cavity.

[0034] In the present invention, the silicone gel is transparent, contains metal bonding wires, and contacts the chip assembly. The silicone gel has a certain hardness and is resistant to high pressure, which can prevent the formation of bubbles while not causing significant stress on the metal bonding wires.

[0035] According to one aspect of the present invention, in step S4, the epoxy glue or silicone rubber is poured onto the stabilization layer until the thickness of the top reinforcement layer reaches 1.5 mm to 2.5 mm, and then allowed to stand for 1 minute to cure the epoxy glue or silicone rubber, wherein the pouring process is carried out in a vacuum environment of 0.1 mbar.

[0036] The epoxy adhesive has a thermal expansion coefficient similar to that of the epoxy resin frame and exhibits strong bonding strength. Preferably, the frame is made of epoxy resin and the top reinforcement layer is made of epoxy adhesive. When the IGBT module is heated, the frame and the epoxy adhesive serving as the top reinforcement layer maintain essentially the same expansion ratio, eliminating any gaps between the top reinforcement layer and the frame, thereby ensuring airtightness between the two layers. Because the top reinforcement layer effectively seals the upper layer of the IGBT module's sealing structure, the present invention allows for a gas layer to exist between the top reinforcement layer and the cover plate. Although this gas layer communicates with the external environment of the IGBT module through an opening in the cover plate, it does not affect the airtightness of the sealing structure.

[0037] According to one aspect of the present invention, the following steps are performed before step S1:

[0038] S1b, steam cleaning the frame and the bottom plate at a temperature of 70±5°C for 4±1 min;

[0039] The steam phase cleaning process is to heat the vapor phase cleaning solvent to boiling. The vapor phase cleaning solvent rises and contacts the cold components to be cleaned. The vapor condenses on the surface of the components, taking away the pollutants on the surface of the components and returning to the heating tank. The vapor phase cleaning solvent is heated and vaporized again. It rises and contacts the cold components and becomes liquid and drips. This cycle can effectively remove the dirt, oil stains and other excess materials on the bonding parts of the frame and the bottom plate. S1c, spray cleaning the frame and the bottom plate, the cleaning temperature is 70±5℃, the spraying time is 1±0.5min,

[0040] Dry for 5±2 minutes.

[0041] The steps S1b and S1c need to be performed sequentially. The steps S1b and S1c need to be performed before step S1, but there is no sequential relationship between them and step S1a.

[0042] When epoxy adhesive is used to bond clean, dirt-free and dry surrounding frames and base plates, the bonding strength between the surrounding frames and base plates can be effectively enhanced.

[0043] According to one aspect of the present invention, the following steps are implemented between step S1 and step S2:

[0044] S1d, coating a coupling agent on the inner surface of the cavity, wherein the coupling agent has a thickness ranging from 10 μm to 30 μm;

[0045] In step S2, the thickness of the silicone rubber is in the range of 1.5 mm to 2.5 mm.

[0046] Coating agent is applied to the cavity. The appropriate coupling agent specifications should be selected based on the materials of the base plate and the frame, so that it is suitable for bonding materials such as silicone rubber, metal, or ceramic. The coupling agent between the substrate and the silicone rubber is a thin layer of coating material that enhances the bonding performance between the silicone rubber and the substrate.

[0047] According to one aspect of the present invention, in step S1a, the silicone rubber is subjected to a degassing treatment in a vacuum environment of 9 mbar-11 mbar, with a rotation speed of 55 rpm-65 rpm and a degassing treatment time of 3 min-7 min;

[0048] In step S1a, the silicone gel is degassed in a vacuum environment of 4 mbar to 6 mbar, the stirring shaft speed is 55 rpm to 65 rpm, and the degassed time is 18 min to 22 min;

[0049] In step S1a, the epoxy adhesive is degassed in a vacuum environment of 4 mbar to 6 mbar, the stirring shaft speed is 55 rpm to 65 rpm, and the degassed time is 8 min to 12 min.

[0050] In step S1, a two-component vacuum preparation system is used to perform degassing treatment;

[0051] In steps S2, S3 and S4, glue pouring is carried out using an offline four-axis single-nozzle two-component vacuum box glue pouring machine. The curing temperature of the silicone rubber is 20°C-30°C, the curing temperature of the silicone gel is 65°C-75°C, and the curing temperature of the epoxy glue is 95°C-105°C.

[0052] In the sealing method of the present invention, a two-component vacuum preparation system is used for degassing. The system can be set to a circulation mode so that the glue circulates in the barrel, the material pump and the material pipe according to the set parameters, flushing the pipe wall and the inner cavity of the material pump to achieve the effect of degassing and making the glue uniform.

[0053] In the sealing method of the present invention, an offline four-axis single-nozzle two-component vacuum box glue dispensing machine is used for glue dispensing. The barrel, pump, and pipe are equipped with heating functions, ensuring full heating and temperature monitoring of the glue, thereby improving the fluidity of the glue.

[0054] Reliability verification of the IGBT module sealed by the sealing method of the present invention:

[0055] 1. Temperature cycle test. The cycle temperature is -55℃ to 150℃, and the cycle is 100 times. After the test, the bottom sealing layer, stabilization layer, and top reinforcement layer have no discoloration, debonding, cracking, etc.

[0056] 2. Withstand voltage test: 1200V withstand voltage test: No sparks were found in the bottom sealing layer, stabilization layer and top reinforcement layer.

[0057] 3. Low-pressure test. The air pressure was set to 0.01 mbar. The IGBT module's electrical performance was normal during the test. After the test, the IGBT module cover was opened, the top reinforcement layer removed, and the bottom sealing layer and stabilization layer visually inspected under a 40x microscope to ensure there was no debonding or bubbles.

[0058] Compared to the prior art, the technical solution of the present invention has the following significant advantages: the silicone rubber, silicone gel, and epoxy adhesive forming the potting body undergo a vacuum degassing treatment, eliminating microbubbles. The frame and base plate are connected in an airtight manner to form a cavity. The potting body poured into the cavity is divided into three layers. By completely housing the IGBT module within the potting body, the IGBT module is placed in an airtight sealed structure. Because the sealed structure is free of gas, the interior of the IGBT module is protected from the external low-pressure environment. In a low-pressure environment, gas trapped in the tiny gaps between the internal terminals of the IGBT module and the frame, between the frame and base plate, and between the chip assembly and the substrate cannot escape into the potting body. This fundamentally eliminates the cause of partial discharge in the IGBT module, eliminates bubbles generated during potting, and seals gas trapped in the gaps during welding. This prevents the IGBT module from releasing gas even in low-pressure environments, preventing the generation of bubbles that can cause partial discharge. Through the sealing technology used for IGBT modules, when the IGBT module is used in a low-voltage environment, although there is an air pressure difference inside and outside the sealed structure, local discharge of microbubbles under the action of high-voltage electric field will not occur, and aging and decomposition of the organic insulating potting body will not be caused, which effectively improves the reliability of the IGBT module. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 This is a flow chart of a sealing method for an IGBT module according to an embodiment of the present invention;

[0060] Figure 2 A flowchart of a sealing method for an IGBT module according to another embodiment of the present invention;

[0061] Figure 3 It is a structural schematic diagram of the low-pressure-resistant high-power IGBT module of the present invention.

[0062] Figure numbers: 1-enclosing frame; 2-bottom plate; 3-bottom sealing layer; 4-stabilizing layer; 5-top reinforcement layer; 6-cover plate; 7-coupling agent; 8-metal bonding wire; DETAILED DESCRIPTION

[0063] 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 the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be derived from these drawings without inventive effort.

[0064] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. The embodiments cannot be described one by one here, but the embodiments of the present invention are not limited to the following embodiments.

[0065] like Figure 1 As shown, a sealing method for an IGBT module according to an embodiment of the present invention includes the following steps:

[0066] S1. The lower portion of the frame 1 is fixedly bonded to the base plate 2 in an airtight manner;

[0067] S2, encapsulating the bottom sealing layer 3 in the cavity formed by the frame 1 and the bottom plate 2;

[0068] S3. In the cavity, a stabilizing layer 4 is encapsulated on the bottom sealing layer 3;

[0069] S4. In the cavity, a top reinforcement layer 5 is encapsulated on the stabilization layer 4;

[0070] S5. Fix the upper portion of the surrounding frame 1 to the cover plate 6.

[0071] The enclosure 1 and base plate 2 are connected in an airtight manner to form a cavity. The potting compound within this cavity is divided into three layers. By completely enclosing the IGBT module within the potting compound, the IGBT module is placed in an airtight, sealed structure. Because the sealed structure is free of gas, the interior of the IGBT module is protected from the effects of the external low-pressure environment. In a low-pressure environment, gas trapped in the tiny, enclosed spaces formed by the tiny gaps between the IGBT module's internal terminals and the enclosure 1, the enclosure 1 and base plate 2, and the chip assembly and substrate will not escape into the potting compound.

[0072] In this embodiment, the hardness ratio of the bottom sealing layer 3 to the stabilizing layer 4 to the top reinforcing layer 5 is (2-3):1:(2-3);

[0073] The bottom sealing layer 3 contains all the chip components. The stabilization layer 4 is provided on top of the bottom sealing layer 3 and contains all the metal bonding wires 8. The top reinforcement layer 5 is provided on top of the stabilization layer 4. The three layers have different hardnesses. Specifically, the stabilization layer 4 is harder than the bottom sealing layer 3 and the top reinforcement layer 5. The softer stabilization layer 4 does not exert compressive stress on the metal bonding wires 8 and can protect them. Because the IGBT module generates heat during operation in a low-voltage environment, the bottom sealing layer 3 and the top reinforcement layer 5 have a certain hardness to effectively prevent the volume expansion of the stabilization layer 4 caused by the influence of air pressure and temperature.

[0074] In this embodiment, the bottom sealing layer 3 is cured silicone rubber; the stabilizing layer 4 is cured silicone gel; and the top reinforcing layer 5 is cured silicone rubber or epoxy glue.

[0075] Silicone rubber has low hardness and high elasticity, and can better solve the thermal mismatch problem between the bottom plate 2 , the surrounding frame 1 , and the adhesive between the bottom plate 2 and the surrounding frame 1 .

[0076] In this embodiment, in step S1, epoxy glue is used to fix and bond the lower portion of the frame 1 and the bottom plate 2;

[0077] The ratio of the thermal expansion coefficient of the frame 1 to the thermal expansion coefficient of the epoxy adhesive is (0.8-1.2):1.

[0078] The epoxy adhesive used to bond the lower portion of the frame 1 to the base plate 2 has a bonding strength greater than 10 N / mm2, which effectively prevents gas from flowing between the base plate 2 and the frame 1. In this step, the epoxy adhesive that has not been vacuum degassed is used.

[0079] Preferably, the thermal expansion coefficient of the material making up the frame 1 should be close to that of the epoxy adhesive. When the IGBT module is heated, the frame 1 and the epoxy adhesive, acting as an adhesive, maintain substantially the same expansion ratio, eliminating any gap between the epoxy adhesive and the frame 1. This ensures an airtight connection between the epoxy adhesive and the frame 1. In this embodiment, the frame 1 is made of epoxy resin.

[0080] In step S2, silicone rubber is potted in the lower portion of the cavity until the bottom sealing layer 3 is higher than the chip assembly. The silicone rubber is allowed to stand for 1 minute to cure. The potting process is performed in a 0.1 mbar vacuum environment. In this embodiment, the thickness of the silicone rubber ranges from 1.5 mm to 2.5 mm.

[0081] In step S3, the silicone gel is mixed using a piston-type static mixer, and the potting process is performed in a 0.1 mbar vacuum environment. The steps for potting the stabilizing layer 4 are as follows:

[0082] S31, filling the cavity with silicone gel that occupies 1 / 4 of the cavity height and covers all metal bonding wires 8, and letting it stand for 2 minutes to 5 minutes;

[0083] S32, continue to pot the silicone gel until the distance between the upper surface of the silicone gel and the upper surface of the frame 1 is 1.5 mm to 5 mm, and let it stand for 1.5 minutes;

[0084] S33, solidifying the silicone gel in the cavity.

[0085] In this embodiment, the silicone gel is transparent and contains the metal bonding wires 8 and is in contact with the chip assembly. The silicone gel has a certain hardness and is resistant to high pressure, which can prevent the formation of bubbles while not causing significant stress on the metal bonding wires 8.

[0086] In step S4, epoxy glue or silicone rubber is poured on the stabilizing layer 4 until the thickness of the top reinforcement layer 5 reaches 1.5 mm to 2.5 mm, and then left to stand for 1 minute to cure the epoxy glue or silicone rubber. The pouring process is carried out in a vacuum environment of 0.1 mbar.

[0087] The epoxy adhesive has a thermal expansion coefficient close to that of the epoxy resin frame 1 and exhibits strong bonding strength. Preferably, the frame 1 is made of epoxy resin, and the top reinforcement layer 5 is made of epoxy adhesive. When the IGBT module is heated, the frame 1 and the epoxy adhesive serving as the top reinforcement layer 5 maintain substantially the same expansion ratio, eliminating any gap between the top reinforcement layer 5 and the frame 1, thereby ensuring airtightness between the top reinforcement layer 5 and the frame 1. Because the top reinforcement layer 5 effectively seals the upper layer of the IGBT module's sealing structure, in this embodiment, a gas layer can exist between the top reinforcement layer 5 and the cover plate 6. Although this gas layer communicates with the external environment of the IGBT module through the opening in the cover plate 6, it does not affect the airtightness of the sealing structure.

[0088] In this embodiment, in steps S2, S3 and S4, an offline four-axis single-nozzle two-component vacuum box glue potting machine is used for glue potting, and the curing temperature of silicone rubber is 25°C, the curing temperature of silicone gel is 70°C, and the curing temperature of epoxy glue is 100°C.

[0089] In this embodiment, in step S1, a two-component vacuum preparation system is used to perform a degassing process;

[0090] A two-component vacuum preparation system is used for degassing. The system can be set to a circulation mode so that the glue circulates in the barrel, pump and pipe according to the set parameters, flushing the pipe wall and the inner cavity of the pump to achieve the effect of degassing and making the glue uniform.

[0091] In this embodiment, an offline four-axis single-nozzle two-component vacuum box glue dispensing machine is used for glue dispensing. The barrel, pump, and pipe are equipped with heating functions to ensure full heating and temperature monitoring of the glue, thereby improving the fluidity of the glue.

[0092] like Figure 2 As shown, according to another embodiment of the present invention, the following steps are performed before step S1:

[0093] S1a. Degas the silicone rubber, silicone gel and epoxy adhesive in a vacuum environment.

[0094] The silicone rubber, silicone gel and epoxy adhesive that form the potting body undergo vacuum degassing treatment to eliminate microbubbles. When the IGBT module is used in a low-voltage environment, although there is an air pressure difference inside and outside the sealed structure, there will be no local discharge of microbubbles under the action of a high-voltage electric field, and the aging and decomposition of the organic insulating potting body will not be caused, thereby improving the reliability of the IGBT module.

[0095] According to another embodiment of the present invention, the following steps are performed after step S1a:

[0096] S1b: Steam cleaning of the enclosure 1 and the bottom plate 2 at a temperature of 70±5°C and a steam cleaning time of 4±1 min.

[0097] The steam vapor phase cleaning process is to heat the vapor phase cleaning solvent to boiling. The vapor phase cleaning solvent vapor rises and contacts the cold component to be cleaned. The vapor condenses on the surface of the component, taking away the pollutants on the surface of the component and returning to the heating tank. The vapor phase cleaning solvent is heated again and vaporized and rises to contact the cold component to become liquid and drip. This cycle can effectively remove the dirt, oil stains and other excess materials at the bonding parts of the frame 1 and the bottom plate 2.

[0098] S1c, spray cleaning frame 1 and bottom plate 2, cleaning temperature 70±5℃, spray time 1±0.5min,

[0099] Dry for 5±2 minutes.

[0100] When epoxy adhesive is used to bond the clean, dirt-free and dry surrounding frame 1 and bottom plate 2 , the bonding strength between the surrounding frame 1 and bottom plate 2 can be effectively enhanced.

[0101] like Figure 3 As shown, according to another embodiment of the present invention, the following steps are implemented between step S1 and step S2:

[0102] S1d, coating the inner surface of the cavity with a coupling agent 7, wherein the thickness of the coupling agent 7 is in the range of 10 μm to 30 μm;

[0103] Coupling agent 7 is applied to the cavity. The appropriate specifications for coupling agent 7 should be selected based on the materials of base plate 2 and frame 1, so as to be suitable for bonding materials such as silicone rubber, metal, or ceramic. Coupling agent 7 is a thin layer of coating material between the substrate and silicone rubber, which enhances the bonding between the silicone rubber and the substrate.

[0104] According to another embodiment of the present invention, in step S1a, the silicone rubber is degassed in a vacuum environment of 10 mbar, with a rotation speed of 60 r / min and a degassed time of 5 min;

[0105] In step S1a, the silicone gel is degassed in a vacuum environment of 5 mbar, the stirring shaft speed is 60 r / min, and the degassed treatment time is 20 min;

[0106] In step S1a, the epoxy adhesive is degassed in a vacuum environment of 5 mbar, the stirring shaft speed is 60 r / min, and the degassed time is 10 min.

[0107] According to another embodiment of the present invention, reliability verification is performed on an IGBT module sealed by the sealing method of this embodiment:

[0108] 1. Temperature cycle test. The cycle temperature ranges from -55°C to 150°C, and the test is repeated 100 times. After the test, the bottom sealing layer 3, the stabilizing layer 4, and the top reinforcement layer 5 show no discoloration, debonding, or cracking.

[0109] 2. Voltage withstand test: 1200V voltage withstand test: No sparks were observed on the bottom sealing layer 3, the stabilizing layer 4 and the top reinforcement layer 5.

[0110] 3. Low-pressure test. The air pressure was set to 0.01 mbar. The IGBT module's electrical performance was normal during the test. After the test, the IGBT module cover 6 was opened, the top reinforcement layer 5 was removed, and a visual inspection was conducted under a 40x microscope to ensure that there was no debonding or bubbles within the bottom sealing layer 3 and stabilization layer 4.

[0111] The above contents are merely examples of specific implementations of the present invention. Any equipment and structures not described in detail should be understood to be implemented using general equipment and methods available in the art.

[0112] The above is merely a specific embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A sealing method for an IGBT module, characterized in that: The following steps are involved: S1, the lower portion of the frame (1) is fixedly connected to the base plate (2) in an airtight manner; S2, encapsulating a bottom sealing layer (3) in the cavity formed between the surrounding frame (1) and the bottom plate (2); S3, in the cavity, encapsulating a stabilizing layer (4) on the bottom sealing layer (3); S4, in the cavity, encapsulating a top reinforcement layer (5) on the stabilizing layer (4); S5, fixing the upper portion of the enclosure frame (1) to the cover plate (6); The bottom sealing layer (3) contains all chip components, the stabilizing layer (4) is arranged on the bottom sealing layer (3) and contains all metal bonding wires (8), the top reinforcement layer (5) is arranged on the stabilizing layer (4), and the bottom sealing layer (3), the stabilizing layer (4) and the top reinforcement layer (5) have different hardnesses, and the hardness of the stabilizing layer (4) is less than the hardness of the bottom sealing layer (3) and the top reinforcement layer (5); The hardness ratio of the bottom sealing layer (3), the stabilizing layer (4), and the top reinforcement layer (5) is (2-3):1:(2-3).

2. The sealing method for an IGBT module according to claim 1, characterized in that: The bottom sealing layer (3) is cured silicone rubber; The stabilizing layer (4) is a cured silicone gel; The top reinforcement layer (5) is cured silicone rubber or epoxy glue.

3. The sealing method for an IGBT module according to claim 2, characterized in that: Before step S1, the following steps are performed: S1a. Degassing the silicone rubber, the silicone gel, and the epoxy adhesive under a vacuum environment.

4. The sealing method for an IGBT module according to claim 3, wherein: In step S1, epoxy glue is used to fix and bond the lower portion of the frame (1) and the bottom plate (2); The ratio of the thermal expansion coefficient of the frame (1) to the thermal expansion coefficient of the epoxy adhesive is (0.8-1.2):

1.

5. The sealing method for an IGBT module according to claim 4, characterized in that: In step S2, the silicone rubber is potted in the lower part of the cavity until the bottom sealing layer (3) is higher than the chip assembly, and the silicone rubber is allowed to stand for 1 minute to solidify, wherein the potting process is carried out in a 0.1 mbar vacuum environment.

6. The sealing method for an IGBT module according to claim 4, characterized in that: In step S3, the silicone gel is mixed in a piston-type static mixing tube, and the potting process is carried out in a 0.1 mbar vacuum environment. The steps of potting the stabilization layer (4) are as follows: S31, filling the cavity with the silicone gel occupying 1 / 4 of the cavity height and covering all metal bonding wires (8), and letting it stand for 2 minutes to 5 minutes; S32, continue to pot the silicone gel until the distance between the upper surface of the silicone gel and the upper surface of the frame (1) is in the range of 1.5 mm to 5 mm, and let it stand for 1.5 minutes; S33, solidifying the silicone gel in the cavity.

7. The sealing method for an IGBT module according to claim 4, characterized in that: In the step S4, the epoxy glue or silicone rubber is poured onto the stabilizing layer (4) until the thickness of the top reinforcement layer (5) reaches 1.5 mm to 2.5 mm, and the epoxy glue or silicone rubber is cured by standing for 1 minute, wherein the pouring process is carried out in a vacuum environment of 0.1 mbar.

8. The sealing method for an IGBT module according to claim 5, 6 or 7, characterized in that: Before step S1, the following steps are performed: S1b, steam phase cleaning of the enclosure (1) and the bottom plate (2), the cleaning temperature being 70±5°C, and the steam cleaning time being 4±1min; S1c, spray cleaning the frame (1) and the bottom plate (2), the cleaning temperature is 70±5°C, the spraying time is 1±0.5min, Dry for 5±2 minutes.

9. The sealing method for an IGBT module according to claim 8, characterized in that: The following steps are performed between step S1 and step S2: S1d, coating a coupling agent (7) on the inner surface of the cavity, wherein the coupling agent (7) has a thickness ranging from 10 μm to 30 μm; In step S2, the thickness of the silicone rubber is in the range of 1.5 mm to 2.5 mm.

10. The sealing method for an IGBT module according to claim 9, characterized in that: In step S1a, the silicone rubber is subjected to a degassing treatment in a vacuum environment of 9 mbar-11 mbar, with a rotation speed of 55 rpm-65 rpm and a degassing treatment time of 3 min-7 min; In step S1a, the silicone gel is degassed in a vacuum environment of 4 mbar to 6 mbar, the stirring shaft speed is 55 rpm to 65 rpm, and the degassed time is 18 min to 22 min; In step S1a, the epoxy adhesive is degassed in a vacuum environment of 4 mbar to 6 mbar, the stirring shaft speed is 55 rpm to 65 rpm, and the degassed time is 8 min to 12 min. In step S1, a two-component vacuum preparation system is used to perform degassing treatment; In steps S2, S3 and S4, glue pouring is carried out using an offline four-axis single-nozzle two-component vacuum box glue pouring machine. The curing temperature of the silicone rubber is 20°C-30°C, the curing temperature of the silicone gel is 65°C-75°C, and the curing temperature of the epoxy glue is 95°C-105°C.

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