IGBT (Insulated Gate Bipolar Translator) module-based batch power supply repair process and

Abstract

The invention relates to a batch power supply repair process and module based on an IGBT module. A power supply based on the IGBT module is reworked and repaired. Firstly, quality detection is carried out, and a power supply meeting the reworking and repairing requirements is selected; and sintering rework, brazing rework and aging test are carried out in sequence. In the step S1, sintering treatment is carried out; executing the following steps; s1.1, determining the number and position of failure chips of each component of the power supply; s1.2, the IGBT module is fixed on an anti-static working table; s1.3, shielding other areas of the IGBT module except the invalid chip by using a polyimide adhesive tape; s1.4, stripping the invalid chip from the ceramic copper-clad plate by using a scraper knife at normal temperature; s1.5, using a 100-mesh steel wire mesh to grind the area after the failure chip is stripped, and dipping a cotton swab in absolute ethyl alcohol to clean the residue of the failure chip in the area; the device is reasonable in design, compact in structure and convenient to use.

Description

Technical Field

[0001] This invention relates to a process and module for batch power supply repair based on IGBT modules. Background Technology

[0002] In recent years, thick-film DC power supply products have developed rapidly, with increasingly higher power outputs.

[0003] The increasing demands on power supply performance have led to high scrap rates, resulting in resource waste and high costs. Reworking repairable products to make full use of them has become an urgent technical problem to be solved.

[0004] Currently, rework is being addressed when mass-produced power supplies based on IGBT modules fail for various reasons. The main drawback of existing technologies is that the methods for aging power supplies in batches are mostly direct aging or adding a simple heat sink, which cannot effectively dissipate heat and cannot monitor the aging temperature of each product in real time, making it impossible to determine whether the power supply case temperature exceeds the specification requirements. As power supplies increase in power, how to reliably achieve aging in high-temperature environments, ensure effective heat dissipation during the aging process of batch products, and monitor the temperature of each product during the aging process to ensure it does not exceed the specifications has become an urgent problem to be solved.

[0005] Existing methods for aging power supplies based on IGBT modules after rework are mostly direct aging or adding a simple heat sink. These methods cannot effectively dissipate heat and cannot monitor the aging temperature of each product in real time, making it impossible to determine whether the power supply case temperature exceeds the specification requirements. In addition, with the development needs of the electronics industry, the integration level of electronic packaging metal shells is getting higher and higher, and the structure is becoming more and more complex. Some shell structures are complex and require multiple sintering. The connecting bridge structure is often used as a primary welding stage, and then the structure is brazed to the shell. Connecting bridge structure such as Figure 3 As shown. Eutectic silver-copper (Ag72Cu28) solder possesses low resistivity, excellent thermal conductivity, and vacuum sealing properties, making it the most commonly used solder for electronic packaging casings. It exhibits good wettability with the base metal. During brazing, the liquid phase time and maximum temperature must be controlled by adjusting the process profile to ensure optimal brazing results. However, during rework, after multiple sintering processes, the solder dispersion of the connecting bridge structure becomes difficult to control, resulting in insufficient solder accumulation at the weld joint, poor brazing performance, and the dispersed solder on the surface affecting subsequent plating and chip bonding. Figure 4 As shown. To solve this problem, it is necessary to find a brazing solder for a single brazing method that will not excessively disperse during the second brazing (maximum temperature 800℃). This would solve the problem of excessive solder flow at the joint of the shell after multiple sintering, which prevents the solder from accumulating, resulting in poor brazing effect and affecting product quality and reliability. Summary of the Invention

[0006] In general, the technical problem to be solved by this invention is to provide a batch power supply repair process and module based on IGBT modules, which is beneficial for heat dissipation during the aging process of batch power supplies and for real-time temperature monitoring of each product. To solve the above problems, the technical solution adopted by the present invention is as follows: A batch power supply repair process based on IGBT modules is proposed, which involves reworking and repairing power supplies based on IGBT modules. First, quality inspection is carried out to select power supplies that meet the rework and repair requirements. The sintering rework, brazing rework, and aging test were carried out in sequence.

[0007] As a further improvement to the above technical solution: In S1, during the sintering process, the following steps are performed; S1.1 Determine the number and location of failed chips in each component of the power supply; S1.2, Fix the IGBT module on the anti-static workbench; S1.3, Use polyimide tape to cover other areas of the IGBT module other than the failed chip; S1.4, Use a scraper to peel the failed chip off the ceramic copper-clad laminate at room temperature; S1.5, use a 100-mesh steel wire mesh to smooth the area after the failed chip has been removed, and use a cotton swab dipped in anhydrous ethanol to clean the residue of the failed chip in the area. S1.6, Use a nitrogen spray gun to further clean the residue from the failed chip; S1.7 Remove the polyimide tape used for masking and observe under a 60x microscope whether there are any defective chip residues inside the IGBT module. S1.8 After confirming that there are no failed chip residues inside the IGBT module, apply Sn63Pb37 solder paste to the original failed chip location and then place the tested and qualified IGBT module inside. S1.9, Place the IGBT module in a vacuum sintering furnace for re-sintering; S1.10, Use an X-ray machine to check whether the void ratio of the sintered IGBT module meets the requirements.

[0008] In S2, brazing is underway; Perform the following steps; S2.1 Clean all components of the power supply to ensure surface cleanliness. Select silver-copper solder with a Cu content between 35% and 50% for brazing. S2.2, Use molds to position each component of the power supply to ensure accurate positioning; S2.3, Brazing the assembled components, with the maximum temperature set to 820℃-830℃ and the high-temperature time to 300s-400s; S2.4, Inspect the brazing effect under a microscope; S2.5, Assemble the sintered IGBT module onto the housing and braze it. S2.6, secondary brazing.

[0009] In Season 3, during the re-aging process... Mass production power supplies based on IGBT modules include IGBT modules and housings housing IGBT modules; The aging tooling includes an aging PCB board; an aging heat dissipation aluminum plate is installed on the aging PCB board; temperature sensors are distributed on the aging heat dissipation aluminum plate. The temperature sensor is electrically connected to a temperature monitoring device; Aged and refined heat dissipation aluminum plates are used to house product modules; Old, refined PCB boards are used as the base layer; Aged and refined heat dissipation aluminum plate as the middle layer; The product module is at the top level; Temperature sensors are distributed on the aged aluminum heat dissipation plate.

[0010] The following installation steps are included in the old-fashioned testing; First, using the aging PCB board required to meet the high-temperature aging function of mass power supplies, screw holes are pre-drilled around the aging PCB board and assembled with the aging heat dissipation aluminum plate. Secondly, using computer-aided design (CAD) based on the aged PCB board, the product module is placed on the aged heat dissipation aluminum plate; then, temperature sensors and a display screen to display the temperature monitored by each temperature sensor in real time are prepared; then, the aged PCB board, aged heat dissipation aluminum plate, and temperature sensors are assembled, and the temperature monitored by each temperature sensor is displayed on the display screen.

[0011] A power module is a module repaired based on the above-mentioned process. In this rework and repair process, the focus is on improving the brazing, sintering, and aging processes; other processes can be based on existing solutions.

[0012] Among these methods, the aging process effectively dissipates heat from high-power power supplies while allowing real-time monitoring of the actual temperature of each unit, meeting both aging requirements and ensuring product safety. The multi-layer assembly aging method saves space and can meet the aging needs of batch rework products. In a sense, even for high-power power supplies, there are suitable aging methods; this approach can be applied to the aging of more reworked products.

[0013] This aging method has a simple structure, practical functions, high integration, and cost savings, and can effectively improve the reliability and operability of aging.

[0014] This invention enables the rework of one or more IGBT modules in a multi-chip IGBT module with a thick film process and metal casing, avoiding oxidation of other chips or circuits in the module during the rework process and preventing voids in the solder joints. This invention uses silver-copper solder with a Cu content between 35% and 50% and performs brazing at a high temperature of 820℃-830℃, which solves the problems of large flowability and poor brazing effect of tube shells after multiple sintering, and improves product quality. Attached Figure Description

[0015] Figure 1 This is a top view of the entire old refining scheme. Figure 2 This is a cross-sectional view of the entire aging process. Figure 3 This is a schematic diagram of the structure of the present invention.

[0016] Figure 4 This is a schematic diagram of the structure of the present invention. Figure 5 This is the Ag-Cu phase diagram of the present invention. The components include: 1. Molybdenum substrate; 2. Connecting copper wires; 3. Brazing solder; 11. Aged PCB board; 12. Aged heat dissipation aluminum plate; 13. Product module; 14. Temperature sensor. Detailed Implementation like Figure 1-5 Based on the batch power supply repair process of IGBT modules, the power supply based on IGBT modules is repaired by rework. First, quality inspection is carried out to select power supplies that meet the rework repair requirements. The sintering rework, brazing rework, and aging test are carried out in sequence. Other steps are the same as the original process or can be adjusted in a routine manner. The process is as follows: S1, undergo sintering treatment; S1.1 Determine the number and location of failed chips in each component of the power supply; S1.2, Fix the IGBT module on the anti-static workbench; S1.3, Use polyimide tape to cover other areas of the IGBT module other than the failed chip; S1.4, Use a scraper to peel the failed chip off the ceramic copper-clad laminate at room temperature; S1.5, use a 100-mesh steel wire mesh to smooth the area after the failed chip has been removed, and use a cotton swab dipped in anhydrous ethanol to clean the residue of the failed chip in the area. S1.6, Use a nitrogen spray gun to further clean the residue from the failed chip; S1.7 Remove the polyimide tape used for masking and observe under a 60x microscope whether there are any defective chip residues inside the IGBT module. S1.8 After confirming that there are no failed chip residues inside the IGBT module, apply Sn63Pb37 solder paste to the original failed chip location and then place the tested and qualified IGBT module inside. S1.9, Place the IGBT module in a vacuum sintering furnace for re-sintering; S1.10, Use an X-ray machine to check whether the void ratio of the sintered IGBT module meets the requirements; S2, perform brazing; pass Figure 5 The phase diagram shows that solders with Cu content below 24% and above 33% both have liquidus lines above 800℃, so solders within this range should be preferred. However, solders with Cu content below 24% cannot be used for brazing copper components. This is because during the heating process, silver and copper atoms diffuse into each other at the contact surface between the solder and the component, resulting in a eutectic liquid phase. The appearance of this liquid phase further accelerates the dissolution of silver and copper. Once the brazing temperature exceeds the eutectic temperature of 779℃, a large amount of copper in the copper component dissolves into the solder, turning the solder into a eutectic alloy solution, causing significant corrosion of the copper component. Therefore, solders with Cu content above 33% should be selected.

[0017] Experiments showed that with a Cu content between 35% and 50%, a maximum temperature of 820℃-830℃, and a high-temperature time of 300s-400s, the first-time brazing effect was good, the second-time brazing had small dispersion, and the brazing interface was good. S2.1 Clean all components of the power supply to ensure surface cleanliness. Select silver-copper solder with a Cu content between 35% and 50% for brazing. S2.2, Use molds to position each component of the power supply to ensure accurate positioning; S2.3, Braze the 10 assembled products at a maximum temperature of 820℃-830℃ for 300s-400s. S2.4, Inspect the brazing effect under a microscope; S2.5, Assemble the sintered IGBT module onto the housing and perform normal brazing and sintering; S2.6 After secondary brazing, the brazing of the connecting bridge is good and the discrete area is small. This scheme can effectively improve the brazing effect of the primary welding structure.

[0018] S3, Re-aged.

[0019] In the aging test, the mass power supply based on IGBT modules includes the IGBT modules and the housing containing the IGBT modules; The aging tooling includes an aging PCB board (11); an aging heat dissipation aluminum plate (12) is provided on the aging PCB board (11); and temperature sensors (14) are distributed on the aging heat dissipation aluminum plate (12). The temperature sensor (14) is electrically connected to a temperature monitoring device; Old, refined heat dissipation aluminum plate (12) is used to place product modules (13). Old PCB board (11) as the bottom layer; Aged heat dissipation aluminum plate (12) is used as the middle layer; Product module (13) is the top level; Temperature sensors (14) are distributed on the aged heat dissipation aluminum plate (12). The aging test includes the following steps; Conduct aging tests; First, using the aged PCB board (11) required to meet the high-temperature aging function of mass power supplies, screw holes are reserved at appropriate positions around the aged PCB board (11) to facilitate assembly with the aged heat dissipation aluminum plate (12). Secondly, using computer-aided design (CAD), based on factors such as the placement of the product module (13) on the old PCB board (11), the middle of the bottom of the product, and the location of the reserved screw holes, an old PCB board heat dissipation aluminum plate (12) that can perfectly fit the circuit board is designed; then, temperature sensors (14) and a display screen that displays the temperature monitored by each temperature sensor (14) in real time are prepared; finally, the old PCB board (11), the old PCB board heat dissipation aluminum plate (12), and the temperature sensors (14) are assembled, and the temperature monitored by each temperature sensor (14) is displayed on the display screen; For components with missing or insufficient solder joints, especially copper parts bonded to molybdenum or molybdenum-copper alloys, brazing is required. The first step in solving this problem is to select a suitable solder. During the first brazing, the solder should have good wettability with the substrate, and during the second brazing, excessive dispersion should be avoided to ensure solder accumulation at the brazing joint. The secondary brazing solder is generally Ag72Cu28, with a maximum welding temperature of 800 degrees Celsius. The melting point of the primary brazing solder should be higher than this temperature. To ensure the electrical and other properties of the weld interface, silver-copper alloy solder is preferred. The present invention has been described in detail for the purpose of making the disclosure clearer, and the prior art will not be listed in detail.

[0020] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. It is obvious to those skilled in the art that multiple technical solutions of the present invention can be combined. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention. All technical contents not described in detail in the present invention are well-known technologies.

Claims

1. A bulk power supply repair process based on IGBT modules, characterized by: The rework repair is based on the IGBT module power supply; first, quality detection is performed, and the power supply meeting the rework repair requirements is selected; In turn, sintering rework, brazing rework, and aging test are performed.

2. The IGBT module based bulk power supply repair process of claim 1, wherein: In S1, sintering treatment is performed; The following steps are performed; S1.1, the number and position of failed chips of each component of the power supply are determined; S1.2, the IGBT module is fixed on an anti-static workbench; S1.3, the IGBT module other than the failed chip is shielded using a polyimide tape; S1.4, the failed chip is peeled off the ceramic copper clad plate at room temperature using a spatula; S1.5, the area after the failed chip is peeled off is ground flat using a 100-mesh steel mesh, and the failed chip residue in the area is cleaned using a cotton swab dipped in anhydrous ethanol; S1.6, the failed chip residue is further cleaned using a nitrogen gas spray gun; S1.7, the polyimide tape used for shielding is removed, and whether there is failed chip residue inside the IGBT module is observed under a 60-times microscope; S1.8, after it is determined that there is no failed chip residue inside the IGBT module, the original failed chip position is coated with Sn63Pb37 solder paste, and a tested qualified IGBT module is placed; S1.9, the IGBT module is placed in a vacuum sintering furnace for re-sintering; S1.10, whether the sintered IGBT module meets the requirements in terms of porosity is detected using an X-ray machine.

3. The IGBT module based bulk power supply repair process of claim 1, wherein: In S2, brazing is performed; The following steps are performed; S2.1, each component of the power supply is cleaned to ensure the surface is clean, and the brazing filler metal is selected to be silver-copper solder with Cu content between 35% and 50%; S2.2, the mold is used to position each component of the power supply to ensure accurate position; S2.3, the assembled components are brazed, with the highest temperature set to 820-830℃, and the high-temperature time set to 300-400s; S2.4, the brazing effect is observed under a microscope; S2.5, the sintered IGBT module is assembled to the shell for brazing and sintering; S2.6, secondary brazing is performed.

4. The IGBT module based bulk power supply repair process of claim 1, wherein: In S3, re-aging is performed, The IGBT module batch power supply includes an IGBT module and a shell carrying the IGBT module; The aging tooling includes an aging PCB (11); the aging PCB (11) is provided with an aging heat dissipation aluminum plate (12); the aging heat dissipation aluminum plate (12) is distributed with temperature sensors (14); The temperature sensors (14) are electrically connected with temperature monitoring equipment; The aging heat dissipation aluminum plate (12) is used for placing a product module (13); The aging PCB (11) is the bottom layer; The aging heat dissipation aluminum plate (12) is the middle layer; The product module (13) is the top layer; The aging heat dissipation aluminum plate (12) is distributed with temperature sensors (14).

5. The IGBT module based bulk power supply repair process of claim 4, wherein: In the aging test, the following installation steps are included; First, the aging PCB (11) meeting the high-temperature electrical aging function requirements of the batch power supply is used, screw holes are reserved around the aging PCB (11), and the aging PCB (11) is assembled with the aging heat dissipation aluminum plate (12); Secondly, by using computer aided design (CAD) according to the old PCB board (11), product module (13) is placed on the old heat dissipation aluminum plate (12); then, temperature sensor (14) and display screen for displaying the temperature monitored by each temperature sensor (14) in real time are prepared; secondly, the old PCB board (11), the old heat dissipation aluminum plate (12) and the temperature sensor (14) are assembled, and the temperature monitored by each temperature sensor (14) is displayed through the display screen.

6. A power module characterized by: is a module repaired based on the process of claim 1.

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