Power module and reflow soldering method thereof

Abstract

The present invention provides a power module and a reflow soldering method thereof, wherein the reflow soldering comprises the following steps: providing a copper-clad ceramic substrate, comprising a ceramic sheet and a copper foil sheet located on the surface of the ceramic sheet; forming a solder layer on the side of the copper foil sheet away from the ceramic sheet, wherein the solder layer contains a flux; stacking objects to be soldered on the side of the solder layer away from the ceramic sheet, and forming a glue layer on the bonding area of ​​the copper-clad ceramic substrate, and finally forming a soldering assembly; placing the soldering assembly in a reflow soldering furnace, and soldering the objects to be soldered with the copper-clad ceramic substrate; and cleaning and removing the residual flux and glue layer after soldering. The present invention integrates the thermal curing and removal of the glue into the inherent process of power module production, has strong compatibility, solves the adverse effects on wire bonding in the prior art, realizes 100% protection of the wire bonding area, ensures the appearance quality and reliability of the power module, and reduces its production cost.

Description

Technical Field

[0001] The invention belongs to the field of semiconductor integrated circuit manufacturing, and in particular relates to a power module and a reflow soldering method thereof. Background Art

[0002] In the field of modern power electronics, the packaging technology of power modules is crucial, among which the lead ultrasonic bonding technology occupies a core position due to its high reliability, wide application scenarios and cost-effectiveness. The lead ultrasonic bonding technology achieves effective connection between the lead wire and the copper-clad ceramic substrate in the power module by adjusting key process parameters such as ultrasonic power, ultrasonic frequency and bonding time.

[0003] However, the successful implementation of ultrasonic wire bonding technology not only relies on the precise control of process parameters, but also places strict requirements on the copper surface characteristics of the copper-clad ceramic substrate. Specifically, the degree of oxidation, flatness and presence of foreign matter on the copper surface will directly affect the bonding quality. In actual production, the reflow soldering process is widely used due to its ease of operation and cost-effectiveness, but this process is prone to small tin beads sputtering during the welding process. If these tin beads sputter to the copper surface of the copper-clad ceramic substrate, it will have an adverse effect on the wire bonding.

[0004] If the tin beads are not completely removed before bonding, the power module will be scrapped in the subsequent production process, thereby increasing production costs. In addition, the process of removing tin beads may damage the copper surface, thereby affecting the bonding strength and appearance quality. Therefore, how to effectively control and reduce the generation of tin beads, and how to completely remove the tin beads on the copper surface before bonding, is the key to improving the production efficiency and reliability of power modules.

[0005] Furthermore, during the welding process in a nitrogen reflow furnace, if the residual oxygen content is high, the furnace temperature is high, or a large number of modules are welded at a time, the copper surface of the copper-clad ceramic substrate is also prone to oxidation. The oxide layer on the copper surface will significantly reduce the strength of the wire bonding, thereby affecting the reliability and service life of the power module. Therefore, how to effectively control the formation of the oxide layer during the welding process and how to improve the oxidation resistance of the copper surface are important research directions for improving the performance of power modules and reducing production costs.

[0006] In summary, the existing ultrasonic bonding technology for wire leads has certain technical bottlenecks and the risk of increased production costs when facing the tin bead problem and copper surface oxidation problem caused by the reflow process. Therefore, it is urgent to develop a new technology or process to effectively solve these problems and improve the production efficiency and product quality of power modules. Summary of the invention

[0007] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a power module and a reflow soldering method thereof, so as to solve the problems of reduced production cost, production efficiency, reliability and service life of the power module in the prior art.

[0008] To achieve the above-mentioned object and other related objects, the present invention provides a power module reflow soldering method, comprising the following steps:

[0009] S1. Providing a copper-clad ceramic substrate, wherein the copper-clad ceramic substrate comprises a ceramic sheet and a copper foil sheet located on a surface of the ceramic sheet;

[0010] S2, printing solder on a welding area of ​​a side of the copper foil away from the ceramic sheet to form a solder layer, wherein the solder layer contains flux;

[0011] S3, stacking objects to be welded on a side of the solder layer away from the ceramic sheet, and forming a glue layer on the bonding area of ​​the copper-clad ceramic substrate, and finally forming a welded assembly;

[0012] S4, placing the welding assembly in a reflow oven, welding the object to be welded to the copper-clad ceramic substrate, wherein the glue layer begins to solidify during the welding preheating stage to protect the bonding area during the welding process;

[0013] S5. After welding, clean it to remove the residual flux and glue layer after welding.

[0014] Preferably, the copper-clad ceramic substrate is a double-sided copper-clad ceramic substrate, and the copper foil comprises a first copper foil and a second copper foil, and the first copper foil and the second copper foil are separately arranged on two opposite sides of the ceramic sheet;

[0015] The solder layer comprises a first solder layer and a second solder layer, the first solder layer is located on a side of the first copper foil away from the ceramic sheet, and the second solder layer is located on a side of the second copper foil away from the ceramic sheet;

[0016] The object to be soldered includes a chip and a heat sink. The chip is located on a side of the first solder layer away from the ceramic sheet, and the heat sink is located on a side of the second solder layer away from the ceramic sheet.

[0017] Preferably, the object to be soldered includes one or more of a chip and a heat sink.

[0018] Preferably, the solder layer comprises a solder paste layer.

[0019] Preferably, the glue layer is formed by dispensing glue on the bonding area of ​​the copper-clad ceramic substrate using a glue dispenser, wherein the glue used for dispensing is a thermosetting modified polycyclic resin glue, and the viscosity of the glue is 50cPs~10000cPs.

[0020] Preferably, the glue dispensing machine includes a spray glue dispensing machine or a pneumatic glue dispensing machine.

[0021] Preferably, when the viscosity of the glue is 50 cPs~4000 cPs, a spray-type dispensing machine is used for dispensing; when the viscosity of the glue is 4000 cPs~10000 cPs, a pneumatic dispensing machine is used for dispensing.

[0022] Preferably, the thickness of the glue layer is 0.2-1.5 mm.

[0023] Preferably, the cleaning is specifically to first use a water-based cleaning solution for ultrasonic cleaning at least once, and then use pure water for rinsing at least once; wherein the ultrasonic cleaning is performed at 55°C~65°C for 6~10 minutes; and the rinsing is performed at 40~50°C for 3~5 minutes.

[0024] The present invention also provides a power module, wherein the power module is obtained by welding using any of the power module reflow welding methods described above.

[0025] As described above, the power module and the reflow soldering method thereof of the present invention have the following beneficial effects:

[0026] The process of the present invention is simple and easy to operate, and the thermal curing and removal of glue are integrated into the inherent process of power module production, and has strong compatibility. Glue is dispensed on the bonding area of ​​the copper-clad ceramic substrate to form a glue layer, and the thermal curing of the glue is compatible with the reflow soldering process. The glue is cured in the preheating stage of the reflow soldering. Since the bonding area is wrapped and covered, the glue layer prevents the tin beads generated in the welding process from contacting and welding with the copper foil, and avoids oxidation of the copper surface, thereby protecting the bonding area. After the welding is completed, the process of removing the glue is compatible with the process of cleaning the solder flux, and a water-based cleaning liquid is used to remove the residual solder flux and glue after welding.

[0027] The present invention solves the adverse effects of tin beads and copper surface oxidation generated by reflow soldering on wire bonding, can achieve 100% protection of the wire bonding area, improve the yield from 80% to 100%, effectively avoid rework and scrapping, ensure the appearance quality and reliability of the power module, reduce the production cost of the power module and improve its production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1It is a flow chart of a power module reflow soldering method according to a specific embodiment of the present invention.

[0029] Figure 2 It is a schematic diagram showing the structure of a welding assembly in a specific embodiment of the present invention.

[0030] Figure 3 It shows a schematic diagram of the structure of the power module in Embodiment 1 of the present invention.

[0031] Explanation of the accompanying drawings: 1. copper-clad ceramic substrate; 100. ceramic sheet; 101. first copper foil sheet; 102. second copper foil sheet; 201. first solder layer; 202. second solder layer; 301. chip; 302. heat sink; 400. glue layer; 500. bonding wire. DETAILED DESCRIPTION

[0032] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0033] Before further describing the specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terms used in the examples of the present invention are intended to describe specific embodiments, rather than to limit the scope of protection of the present invention. The test methods in the following examples without specifying specific conditions are generally carried out under conventional conditions or under conditions recommended by the manufacturers.

[0034] When the embodiments give numerical ranges, it should be understood that, unless otherwise specified in the present invention, both endpoints of each numerical range and any numerical value between the two endpoints can be selected. Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as those generally understood by those skilled in the art. In addition to the specific methods, equipment, and materials used in the embodiments, according to the grasp of the prior art by those skilled in the art and the record of the present invention, any methods, equipment, and materials of the prior art similar or equivalent to the methods, equipment, and materials described in the embodiments of the present invention can also be used to realize the present invention.

[0035] See also Figures 1 to 3 It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0036] Compared with the methods of controlling tin bead sputtering based on the prior art, such as using specially designed tooling protection, adjusting the amount and formula of solder flux, optimizing the printing process and furnace temperature curve, the method of the present invention is simple to operate, has strong compatibility with normal process steps, and has a more significant improvement effect. Moreover, compared with the methods of reducing the degree of copper surface oxidation by reducing the furnace temperature during the welding process, increasing the nitrogen concentration, etc. in the prior art, the method of the present invention will not cause process problems, such as cold welding and oxidation of individual modules.

[0037] The present invention provides a power module reflow soldering method, please refer to Figure 1 , including the following steps:

[0038] S1, providing a copper-clad ceramic substrate 1, wherein the copper-clad ceramic substrate 1 comprises a ceramic sheet 100 and a copper foil sheet located on a surface of the ceramic sheet 100;

[0039] S2, printing solder on the welding area of ​​the copper foil away from the ceramic sheet 100 to form a solder layer, wherein the solder layer contains flux;

[0040] S3, stacking the objects to be welded on the side of the solder layer away from the ceramic sheet 100, and forming a glue layer 400 on the bonding area of ​​the copper-clad ceramic substrate 1, and finally forming a welded assembly;

[0041] S4, placing the welding assembly in a reflow oven, welding the object to be welded to the copper-clad ceramic substrate 1, wherein the glue layer 400 begins to solidify during the welding preheating stage to protect the bonding area during the welding process;

[0042] S5. After the welding is completed, cleaning is performed to remove the residual flux and glue layer 400 after the welding.

[0043] Specifically, glue is dispensed on the bonding area of ​​the copper-clad ceramic substrate 1 to form a glue layer 400, and the thermal curing of the glue is made compatible with the reflow soldering process. The glue is cured in the preheating stage of the reflow soldering. Since the bonding area is wrapped and covered, the glue layer 400 prevents the tin beads generated during the welding process from contacting and welding with the copper foil, and avoids oxidation of the copper surface, thereby protecting the bonding area. After welding is completed, the process of removing the glue is made compatible with the process of cleaning the flux, so as to remove the residual flux and glue after welding.

[0044] In a specific embodiment of the present invention, after removing the residual flux and glue layer 400, drying is performed, and then the object to be soldered and the bonding area are interconnected using a bonding wire 500, wherein the bonding wire 500 is one of a copper wire, an aluminum wire, and an aluminum-clad copper wire.

[0045] As an example, the copper-clad ceramic substrate 1 in step S1 uses a double-sided copper-clad ceramic substrate 1 , and the copper foil includes a first copper foil 101 and a second copper foil 102 , which are separately arranged on two opposite sides of the ceramic sheet 100 .

[0046] As an example, the solder layer in step S2 includes a first solder layer 201 and a second solder layer 202 , wherein the first solder layer 201 is located on a side of the first copper foil 101 away from the ceramic sheet 100 , and the second solder layer 202 is located on a side of the second copper foil 102 away from the ceramic sheet 100 .

[0047] As an example, in step S3 , the objects to be soldered include a chip 301 and a heat sink 302 . The chip 301 is located on a side of the first solder layer 201 away from the ceramic sheet 100 , and the heat sink 302 is located on a side of the second solder layer 202 away from the ceramic sheet 100 .

[0048] For details, see Figure 2 The copper-clad ceramic substrate 1 used in this specific embodiment is a double-sided copper-clad ceramic substrate 1, one side of the copper-clad ceramic substrate 1 is used for welding with the chip 301, and the other side is used for welding with the heat sink 302; the first copper foil 101 is divided into several areas, including a welding area and a bonding area, the first side of the chip 301 is subsequently welded to the first copper foil 101 in the welding area by reflow soldering, the second side of the chip 301 is connected to the bonding area of ​​the first copper foil 101 by lead ultrasonic bonding, and a glue layer 400 is formed in the bonding area of ​​the first copper foil 101, and the glue layer 400 begins to solidify during the welding preheating stage, so as to protect the bonding area during the welding process to ensure the strength of the lead bonding; the second copper foil 102 is a whole copper surface, which is used for subsequent welding with the heat sink 302 by reflow soldering.

[0049] Of course, in other embodiments, the copper-clad ceramic substrate 1 may also be a single-sided copper-clad ceramic substrate 1 , with only one side being welded to the object to be welded. In practical applications, this can be selected according to needs and is not overly limited here.

[0050] As an example, the object to be soldered includes one or more of a chip 301 and a heat sink 302 .

[0051] Specifically, if the copper-clad ceramic substrate 1 is a single-sided copper-clad ceramic substrate 1, the object to be soldered can be a chip 301 or a heat sink 302; if the copper-clad ceramic substrate 1 is a double-sided copper-clad ceramic substrate 1, the object to be soldered can be both a chip 301 and a heat sink 302, or both a chip 301 and a heat sink 302.

[0052] As an example, the solder layer includes a solder paste layer.

[0053] For details, see Figure 2The first solder layer 201 and the second solder layer 202 include solder paste layers, wherein both the first solder layer 201 and the second solder layer 202 contain flux.

[0054] As an example, the glue layer 400 is formed by dispensing glue on the bonding area of ​​the copper-clad ceramic substrate 1 using a glue dispenser, wherein the glue used for dispensing is a thermosetting modified polycyclic resin glue, and the viscosity of the glue is 50 cPs~10000 cPs.

[0055] Specifically, the thermosetting modified polycyclic resin glue is a single-component, water-soluble glue that is thermoset by high-temperature baking. It can be cured by baking at 150°C for 25 minutes. Generally speaking, the higher the temperature, the faster the curing. It is hard after curing and can withstand temperatures of 280°C for 2 hours without charring, and has excellent thermal stability. In the subsequent reflow soldering process, the thermal curing of the glue is compatible with the reflow soldering process. During the preheating stage of welding, the glue layer 400 begins to cure. The glue layer 400 can prevent the tin beads generated during the reflow soldering process from contacting and welding with the bonding area of ​​the first copper foil 101. Even if the glue layer 400 is not completely cured during the preheating stage of welding, its surface is cured, which does not affect the blocking of the tin beads by the glue layer 400.

[0056] Specifically, the heat-cured modified polycyclic resin adhesive can be completely dissolved in water after heat curing, and will not cause adhesive residue on the surface of the material or affect the appearance.

[0057] Specifically, in a specific embodiment of the present invention, the viscosity of the glue may include values ​​within any range such as 50 cPs, 100 cPs, 1000 cPs, 2000 cPs, 4000 cPs, 6000 cPs, 8000 cPs, 10000 cPs, etc.

[0058] As an example, the glue dispenser includes a spray glue dispenser or a pneumatic glue dispenser.

[0059] Specifically, the spray-type glue dispensing machine adopts the injection technology, replaces the syringe with a nozzle, and uses the high-pressure airflow to accurately spray the glue on the bonding area of ​​the first copper foil 101 in the form of a jet; the pneumatic glue dispensing machine drives the glue dispensing valve through air pressure to drip the glue to the position where glue is needed; in addition, the glue dispensing machine used in the specific embodiment of the present invention is an automatic or semi-automatic glue dispensing machine, which can reduce manual operation, improve production efficiency, reduce human errors, and improve product consistency and stability.

[0060] As an example, when the viscosity of the glue is 50cPs~4000cPs, a spray dispensing machine is used for dispensing; when the viscosity of the glue is 4000cPs~10000cPs, a pneumatic dispensing machine is used for dispensing.

[0061] Specifically, when the viscosity of the glue is within any range of 50cPs, 100cPs, 500cPs, 1000cPs, 2000cPs, 3000cPs, 4000cPs, etc., a spray dispensing machine is used for dispensing; when the viscosity of the glue is within any range of 4000cPs, 6000cPs, 8000cPs, 10000cPs, etc., a pneumatic dispensing machine is used for dispensing.

[0062] As an example, the thickness of the glue layer 400 is 0.2-1.5 mm.

[0063] Specifically, the thickness of the glue layer 400 formed after the glue is applied is controlled by adjusting the dispensing pressure, dispensing speed and the shape and size of the glue discharge needle of the dispensing machine. In a specific embodiment of the present invention, the thickness of the glue layer 400 may include any value within a range of 0.2mm, 0.3mm, 0.5mm, 0.8mm, 1.0mm, 1.2mm, 1.5mm, etc.

[0064] As an example, the cleaning in step S5 is specifically to first use a water-based cleaning solution for ultrasonic cleaning at least once, and then use pure water for rinsing at least once; wherein, the ultrasonic cleaning is performed at 55°C~65°C for 6~10 minutes; and the rinsing is performed at 40~50°C for 3~5 minutes.

[0065] For details, see Figure 3 The glue layer 400 and the flux are removed at the same time by cleaning. The glue removal process is compatible with the flux removal process. The process is simple and easy to operate. After the glue layer 400 is removed, on the one hand, tin beads are prevented from sputtering to the bonding area of ​​the first copper foil 101 during the reflow soldering process, and on the other hand, oxidation of the copper surface in the bonding area is prevented, which effectively improves the bonding strength of the subsequent lead ultrasonic bonding and improves the reliability and service life of the power module.

[0066] In a specific embodiment of the present invention, the water-based cleaning liquid is preferably an alkaline water-based flux cleaning liquid, which includes some pure water and organic components. The alkaline water-based flux cleaning liquid commonly used in the art can be used. No excessive restrictions are made here. When the water-based cleaning liquid is used for ultrasonic cleaning, the residual flux and glue layer 400 after welding can be removed at the same time, and the glue layer 400 is soluble in the water-based cleaning liquid.

[0067] Specifically, the number of ultrasonic cleanings is usually two times, which can be selected according to actual conditions. The temperature of ultrasonic cleaning can include values ​​within any range such as 55°C, 58°C, 60°C, 62°C, 65°C, etc., and the time of ultrasonic cleaning can include values ​​within any range such as 6min, 7min, 8min, 9min, 10min, etc.; the number of rinsings is usually two times, which can be selected according to actual conditions. The temperature of rinsing can include values ​​within any range such as 40°C, 42°C, 44°C, 46°C, 48°C, 50°C, etc., and the time of rinsing can include values ​​within any range such as 3min, 4min, 5min, etc.; heating and turning on ultrasound during cleaning can accelerate degumming and improve cleaning efficiency.

[0068] The present invention also provides a power module, which is obtained by welding using the power module reflow welding method.

[0069] In order to better understand the power module and the reflow soldering method thereof in the present invention, the power module and the reflow soldering method thereof in the present invention are described below with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present invention in any way.

[0070] Example 1

[0071] In this embodiment, EconoPACK TM Taking packaging as an example, a power module reflow soldering method is provided, including the following steps:

[0072] S1, providing a double-sided copper-clad ceramic substrate 1, wherein the copper-clad ceramic substrate 1 comprises a ceramic sheet 100 and a first copper foil sheet 101 and a second copper foil sheet 102 located on two sides of the ceramic sheet 100;

[0073] S2, printing solder paste on the welding area of ​​the first copper foil 101 away from the ceramic sheet 100 to form a first solder layer 201, the first solder layer 201 contains solder flux, and printing solder paste on the entire side of the second copper foil 102 away from the ceramic sheet 100 to form a second solder layer 202, the second solder layer 202 contains solder flux;

[0074] S3, stacking the chip 301 on the side of the first solder layer 201 away from the ceramic sheet 100, and using a modified polycyclic resin glue with a viscosity of 10000 cPs, using a semi-automatic pneumatic glue dispenser to dispense glue on the bonding area of ​​the copper-clad ceramic substrate 1, the glue head is made of stainless steel, the glue outlet is flat, the size is 20G, the glue dispensing pressure is 0.1Mpa, the glue dispensing speed is 15mm / s, forming a glue layer 400 with a thickness of 0.6mm, and finally forming a welding assembly;

[0075] S4, placing the welding assembly in a reflow oven, welding the object to be welded to the copper-clad ceramic substrate 1, wherein the preheating temperature is lower than 200°C, the preheating is 4 minutes, the glue layer 400 begins to solidify during the welding preheating stage, and after the preheating stage solidification is completed, it enters the high-temperature welding zone, the glue layer 400 is used to protect the bonding area during the welding process, wherein the peak temperature of the high-temperature welding zone is 250°C, and the welding time is 3 minutes;

[0076] S5. After welding is completed, cleaning is carried out. The first two tanks of the cleaning equipment are water-based cleaning liquid. Ultrasonic cleaning is turned on and heated to 60°C. Cleaning is done for 8 minutes each. The last two tanks are pure water, heated to 45°C, and rinsed for 4 minutes each to remove 400% of the residual flux and glue layer after welding.

[0077] See also Figure 3 The present embodiment also provides a power module, which is obtained by soldering using the power module reflow soldering method of the present embodiment. After removing the flux and glue layer 400, it is dried at 80°C for 6 minutes, and then a 15 mil aluminum wire is used as a bonding wire 500 to interconnect the chip 301 with the bonding area.

[0078] After testing, the bonding shear force of the 15mil aluminum wire is stable at more than 2000gf, that is, the bonding interface in this embodiment can withstand a relatively large force without cracking when subjected to shear force, and has high strength, ensuring the reliability and durability of the power module.

[0079] In summary, the process of the present invention is simple and easy to operate, and the glue thermal curing and glue removal are integrated into the inherent process of power module production, which has strong compatibility. The glue is applied to the bonding area of ​​the copper-clad ceramic substrate to form a glue layer, and the glue thermal curing is compatible with the reflow soldering process. The glue is cured in the preheating stage of the reflow soldering. Since the bonding area is wrapped and covered, the glue layer prevents the tin beads generated during the welding process from contacting and welding with the copper foil, and avoids the oxidation of the copper surface, thereby protecting the bonding area; after the welding is completed, the glue removal process is compatible with the process of cleaning the solder flux, and a water-based cleaning liquid is used to remove the residual solder flux and glue after welding. The present invention solves the adverse effects of the tin beads and copper surface oxidation generated by the reflow soldering on the lead bonding, can achieve 100% protection of the lead bonding area, and improve the yield from 80% to 100%, effectively avoiding rework and scrapping, ensuring the appearance quality and reliability of the power module, reducing the production cost of the power module and improving its production efficiency. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial utilization value.

[0080] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A power module reflow soldering method, characterized in that: The following steps are involved: A copper-clad ceramic substrate is provided, wherein the copper-clad ceramic substrate comprises a ceramic sheet and a copper foil sheet located on a surface of the ceramic sheet; Printing solder on a welding area of ​​a side of the copper foil away from the ceramic sheet to form a solder layer, wherein the solder layer contains flux; Stacking objects to be welded on a side of the solder layer away from the ceramic sheet, and forming a glue layer on the bonding area of ​​the copper-clad ceramic substrate to finally form a welded assembly; Placing the welding assembly in a reflow oven, welding the object to be welded to the copper-clad ceramic substrate, wherein the glue layer begins to solidify during the welding preheating stage to protect the bonding area during the welding process; After soldering is completed, cleaning is performed to remove the residual flux and glue layer after soldering.

2. The power module reflow soldering method according to claim 1, characterized in that: The copper-clad ceramic substrate adopts a double-sided copper-clad ceramic substrate, and the copper foil comprises a first copper foil and a second copper foil, and the first copper foil and the second copper foil are separately arranged on two opposite sides of the ceramic sheet; The solder layer comprises a first solder layer and a second solder layer, the first solder layer is located on a side of the first copper foil away from the ceramic sheet, and the second solder layer is located on a side of the second copper foil away from the ceramic sheet; The object to be soldered includes a chip and a heat sink. The chip is located on a side of the first solder layer away from the ceramic sheet, and the heat sink is located on a side of the second solder layer away from the ceramic sheet.

3. The power module reflow soldering method according to claim 1, characterized in that: The object to be soldered includes one or more of a chip and a heat sink.

4. The power module reflow soldering method according to claim 1, characterized in that: The solder layer includes a solder paste layer.

5. The power module reflow soldering method according to claim 1, characterized in that: The glue layer is formed by dispensing glue on the bonding area of ​​the copper-clad ceramic substrate using a glue dispenser, wherein the glue used for dispensing is a thermosetting modified polycyclic resin glue, and the viscosity of the glue is 50cPs~10000cPs.

6. The power module reflow soldering method according to claim 5, characterized in that: The glue dispensing machine includes a spray type glue dispensing machine or a pneumatic glue dispensing machine.

7. The power module reflow soldering method according to claim 6, characterized in that: When the viscosity of the glue is 50cPs~4000cPs, a spray-type dispensing machine is used for dispensing; when the viscosity of the glue is 4000cPs~10000cPs, a pneumatic dispensing machine is used for dispensing.

8. The power module reflow soldering method according to claim 1, characterized in that: The thickness of the glue layer is 0.2-1.5 mm.

9. The power module reflow soldering method according to claim 1, characterized in that: Specifically, the cleaning is firstly performed with a water-based cleaning solution for ultrasonic cleaning at least once, and then rinsed with pure water at least once; wherein, the ultrasonic cleaning is performed at 55°C to 65°C for 6 to 10 minutes; and the rinsing is performed at 40 to 50°C for 3 to 5 minutes.

10. A power module, characterized in that: The power module is obtained by soldering using the power module reflow soldering method described in any one of claims 1 to 9.

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