A green liquid-phase assisted brazing method for connecting complex multilayer aluminum alloy microchannel structures

Abstract

This invention discloses a green liquid-phase assisted brazing method for connecting complex multilayer aluminum alloy microchannel structures. First, the surfaces of the aluminum alloy component to be welded are ground smooth. An Al-Si based brazing filler metal is pre-formed between the two surfaces. The non-welding surfaces of the aluminum alloy component are uniformly coated with solder resist and dried. Then, the component is placed in a high-temperature vacuum brazing furnace. Next, the high-temperature vacuum brazing furnace is heated to the preheating temperature at a rate of 10°C / min and held for a period of time. Heating continues at a rate of 10°C / min to the connection temperature and is held for a period of time. At the beginning of the holding period, pressure is rapidly applied to the aluminum alloy component to expel excess liquid brazing filler metal. Finally, after the holding period, the pressure applied to the aluminum alloy component is removed, and the high-temperature vacuum brazing furnace is cooled to a certain temperature at a rate of 5°C / min. The liquid brazing filler metal solidifies and forms a reliable connection with the aluminum alloy component, and then cools naturally to room temperature with the furnace. This method solves the problems of brazing filler metal melting and clogging of microchannels and reducing the corrosion performance of microchannel heat sinks. It has low requirements for the surface roughness of the surfaces to be welded and eliminates the need for acid and alkali cleaning.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy brazing technology, and in particular relates to a green liquid phase-assisted brazing method for connecting complex multilayer aluminum alloy microchannel structures. Background Technology

[0002] To achieve better heat dissipation in electronic packaging modules and meet the heat dissipation requirements of circuit chips and other structures, multilayer microchannel heat sinks have been widely used in many fields, including military, due to their high heat dissipation efficiency. Because aluminum alloys are low in cost, lightweight, corrosion-resistant, and have excellent thermal conductivity, many research institutions have proposed using aluminum alloys to fabricate multilayer microchannel heat sinks in recent years. The complex structure of aluminum alloy microchannels requires each channel to achieve a dense connection with the cover plate with minimal deformation. Based on the complex structure of multilayer aluminum alloy microchannels and the welding characteristics of aluminum alloy materials, the commonly used welding methods are currently brazing and diffusion welding.

[0003] During diffusion welding of aluminum alloys or aluminum-based composites, the oxide film on the joining surface can hinder atomic diffusion at the interface, easily reducing the strength of the weld joint or even causing incomplete fusion defects. When using diffusion welding to join aluminum alloys, not only is it necessary to remove the oxide film with environmentally harmful acid and alkali solutions before welding, but a new aluminum oxide film will also form on the aluminum alloy during assembly after acid and alkali washing. In addition, diffusion welding requires high surface roughness of the sample. For complex multilayer microchannel structures, large welding pressure is often required to break the oxide film on the aluminum alloy surface, expose the base metal, and promote the closure of pores at the interface. However, excessive welding pressure can easily lead to excessive deformation of the welded part, causing product failure and scrap.

[0004] For brazing connections of complex multilayer microchannel structures in aluminum alloys, it is necessary to reduce the vacuum brazing process temperature to prevent melting corrosion caused by overheating of the base material. Simultaneously, it is crucial to use Al-Si-based brazing filler metals with good wettability and flowability to ensure reliable connection and strength. However, key problems with vacuum brazing are as follows: 1) The microchannel space is small, making it easy for the brazing filler metal to flow into the channels, hindering the flow of the working medium and affecting heat dissipation performance. 2) Significant compositional differences between the brazing filler metal and the base material lead to electrochemical corrosion in microchannel heat sinks during long-term service, causing joint cracking and shortening the lifespan of the heat sink. 3) During use, microchannel heat sinks experience significant internal pressure due to changes in the working medium temperature, requiring high joint strength. However, brazed joints are prone to incomplete welding defects, resulting in poor mechanical properties. Furthermore, the flow of the brazing filler metal causes variations in the weld seam thickness, leading to uneven performance at different locations within the microchannel and impacting practical applications.

[0005] In summary, in view of the welding requirements and problems of aluminum alloy microchannel heat sinks, this application proposes a green liquid phase assisted brazing method for connecting complex multilayer aluminum alloy microchannel structures. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the technical problem this invention aims to solve is to propose a green liquid-phase assisted brazing method for connecting complex multilayer aluminum alloy microchannel structures. This method eliminates the need to remove the oxide film from the surface of the aluminum alloy parts before brazing and has low requirements for surface roughness. During the brazing heat treatment stage, pressure is applied to expel excess liquid-phase brazing filler metal at the interface to assist in the connection. This results in good interface formation, improved joint strength and corrosion resistance, and the achievement of precise connections for complex aluminum alloy microchannel structures.

[0007] The present invention solves the aforementioned technical problem by adopting the following technical solution:

[0008] A green liquid-phase assisted brazing method for connecting complex multilayer aluminum alloy microchannel structures, characterized by comprising the following steps:

[0009] Step 1: Grind the surfaces of the two aluminum alloy parts to be welded flat. Pre-form Al-Si based brazing filler metal between the surfaces of the two aluminum alloy parts to be welded. Coat the non-welding surfaces of the aluminum alloy parts evenly with solder resist and dry them. Place the two aluminum alloy parts as a whole in a high-temperature vacuum brazing furnace.

[0010] Step 2: Wait for the pressure inside the high-temperature vacuum brazing furnace to drop to 1.5 × 10⁻⁶. -3 Below Pa, the high-temperature vacuum brazing furnace is heated to the preheating temperature at a rate of 10℃ / min and held for a period of time; then it is heated to the connection temperature at a rate of 10℃ / min and held for a period of time. At the beginning of the holding period, pressure is quickly applied to the aluminum alloy part through the pressure head to squeeze out the excess liquid phase brazing material. The total downward displacement after the pressure head touches the aluminum alloy part satisfies equation (1).

[0011] x=αd1+d2(1)

[0012] In the formula: x is the total downward displacement after the pressure head touches the aluminum alloy part, α is the linear expansion coefficient of the aluminum alloy, d1 is the total height of the two aluminum alloy parts along the pressure direction, and d2 is the pre-fabricated thickness of the brazing filler metal.

[0013] Step 3: After the heat preservation is completed, the pressure applied to the aluminum alloy parts is removed, and the high-temperature vacuum brazing furnace is cooled to a certain temperature at a rate of 5℃ / min. The liquid phase Al-Si based brazing filler metal solidifies and forms a reliable connection with the two aluminum alloy parts. Finally, the furnace is allowed to cool naturally to room temperature.

[0014] Furthermore, in step 1, the thickness of the brazing filler metal prefabrication is 20-50 μm.

[0015] Furthermore, in step 2, the heat preservation time at both the preheating temperature and the connection temperature is 5 to 30 minutes.

[0016] Furthermore, the Al-Si based solder is one of Al-Si-Mg, Al-Si-Cu, or Al-Si-Mg-Cu solder.

[0017] Furthermore, the aluminum alloy component is made of either 6063 or 6061 aluminum alloy.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] 1. During the brazing and heat preservation stage, pressure is applied to the aluminum alloy components to expel excess liquid brazing filler metal at the interface. The interface consists only of Al-Si based brazing filler metal and the aluminum alloy matrix, filling micro-gaps of the same scale as the surface roughness. After cooling and solidification, a reliable metallurgical connection is formed. This method effectively solves the problems of microchannel blockage after brazing filler metal melts and reduced corrosion performance of multilayer aluminum alloy microchannel heat sinks, significantly improving the connection performance of the joint at room temperature and extending the service life of multilayer aluminum alloy microchannel heat sinks. The downward displacement of the pressure head during the pressure application process is related to the linear expansion coefficient of the aluminum alloy, the total height of the two aluminum alloy components along the pressure direction, and the pre-made thickness of the brazing filler metal, achieving precise connection of complex multilayer aluminum alloy microchannel structures.

[0020] 2. Compared to diffusion welding methods for aluminum alloys, this invention has lower requirements for the surface roughness of the surfaces to be welded. Only roughening the surface with coarse-grit sandpaper is needed, eliminating the need for acid and alkali washing to remove the oxide film on the aluminum alloy surface. This makes the welding process more environmentally friendly and pollution-free. Compared to conventional brazing of aluminum alloys, pressure is applied to the aluminum alloy parts during the brazing heat treatment stage, squeezing out excess liquid brazing filler metal. Only liquid phase fills the microscopic gaps at the interface, which are equal in size to the surface roughness. There is no brazing seam at the interface; it consists only of the aluminum alloy matrix. The joint is well-bonded, without cracks, voids, or other defects, and no brittle intermetallic compounds are formed. The joint is as strong as the base material.

[0021] 3. This method enables reliable connections between aluminum alloys at relatively low temperatures, with short pressure application times, low pressure values, minimal joint deformation, high precision, and no residual Al-Si-based brazing filler metal at the interface, resulting in good corrosion resistance. Compared to traditional brazing, it is more suitable for connecting complex multilayer microchannel structures and for mass production. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the brazed assembly of the present invention;

[0023] Figure 2 This is a heating curve diagram of an embodiment of the present invention;

[0024] Figures 3(a) and (b) are scanning electron microscope images of the connector interface in Embodiment 1 of the present invention;

[0025] Figures 4(a) and (b) are scanning electron microscope images of the connector interface in Embodiment 2 of the present invention;

[0026] Figures 5(a) and (b) are scanning electron microscope images of the connector interface in Embodiment 3 of the present invention;

[0027] Figure 6 This is a schematic diagram of the joint interface evolution mechanism in Embodiment 1 of the present invention;

[0028] Figure 7 This is a graph showing the change in shear strength of the joint in Embodiment 1 of the present invention with connection temperature;

[0029] Figure 8 This is a graph showing the change in shear strength of the joint in Embodiment 2 of the present invention with heat preservation time;

[0030] Figure 9 This is a schematic diagram of the structure of the multi-microchannel component in Embodiment 4 of the present invention. Detailed Implementation

[0031] Specific embodiments are given below with reference to the accompanying drawings. These specific embodiments are only used to describe the technical solution of the present invention in detail and are not intended to limit the scope of protection of this application.

[0032] This invention provides a green liquid-phase assisted brazing method for connecting complex multilayer aluminum alloy microchannel structures, specifically including the following steps:

[0033] Step 1: Grind the surfaces of the two aluminum alloy parts to be welded smooth. Pre-form Al-Si based brazing filler metal between the surfaces of the two aluminum alloy parts to be welded. Coat the non-welding surfaces of the two aluminum alloy parts evenly with solder resist and dry. Use a fixture to place the two aluminum alloy parts on a graphite disk with the pressure head above the aluminum alloy parts to form a brazing assembly. Place the brazing assembly in a high-temperature vacuum brazing furnace.

[0034] The pre-fabrication thickness of the brazing filler metal is 20-50 μm;

[0035] Step 2: Wait for the pressure inside the high-temperature vacuum brazing furnace to drop to 1.5 × 10⁻⁶. -3Below Pa, the high-temperature vacuum brazing furnace is heated to the preheating temperature at a heating rate of 10℃ / min and held for a period of time (5-30min); then heated to the connection temperature (melting temperature of Al-Si based brazing filler metal) at a heating rate of 10℃ / min, the Al-Si based brazing filler metal completely melts and wets the welding surfaces of the two aluminum alloy parts; the connection temperature is held for a period of time (5-30min), at the beginning of the holding period, pressure is applied to the aluminum alloy parts through the pressure head to squeeze out the excess liquid phase of Al-Si based brazing filler metal at the connection interface, and the total downward displacement after the pressure head touches the aluminum alloy parts satisfies equation (1); during the holding period, a complex metallurgical reaction occurs at the solid-liquid interface between the aluminum alloy parts and the Al-Si based brazing filler metal.

[0036] x=αd1+d2 (1)

[0037] In the formula: x is the total downward displacement after the pressure head touches the aluminum alloy part, α is the linear expansion coefficient of the aluminum alloy, d1 is the total height of the two aluminum alloy parts along the pressure direction, and d2 is the pre-fabricated thickness of the brazing filler metal.

[0038] Step 3: After the heat preservation is completed, the pressure applied to the aluminum alloy parts is removed, and the high-temperature vacuum brazing furnace is cooled to a certain temperature at a rate of 5℃ / min. The liquid phase Al-Si based brazing filler metal solidifies and forms a reliable connection with the two aluminum alloy parts, forming a joint. Finally, the furnace is allowed to cool naturally to room temperature to prevent the joint from generating large residual thermal stress.

[0039] The aluminum alloy parts are made of, but are not limited to, 6063 and 6061 aluminum alloys.

[0040] The Al-Si based solder includes, but is not limited to, Al-Si-Mg, Al-Si-Cu, and Al-Si-Mg-Cu solders. The solder melts completely at the connection temperature and has good wettability on the aluminum alloy surface.

[0041] During the pretreatment process before welding, aluminum alloy parts are processed using an electrical discharge wire cutting machine, and then ultrasonically cleaned in acetone for 10-15 minutes to remove oil stains.

[0042] Because brazing requires a high degree of vacuum, the pressure in the high-temperature vacuum brazing furnace at the joining temperature should not exceed 4.5 × 10⁻⁶. -3 Pa.

[0043] Example 1

[0044] This embodiment takes 6063 aluminum alloy and Al-Si-Mg-Cu solder as an example, and specifically includes the following steps:

[0045] Step 1: Machine two Φ30×40mm aluminum alloy parts from 6063 aluminum alloy using wire EDM, and ultrasonically clean them in acetone for 10 minutes. The area of ​​the surface to be welded is 15×15πmm. 2 The surfaces of the two aluminum alloy parts to be welded are mechanically ground smooth using 400-grit sandpaper, without the need for additional oxide film removal. A 50μm thick Al-Si-Mg-Cu solder filler is pre-formed between the surfaces to be welded on the two aluminum alloy parts. A solder resist is applied to the non-welding surfaces and dried. Anhydrous ethanol solvent is added to Y2O3 powder and mixed evenly to obtain the solder resist. The two aluminum alloy parts are placed on a graphite disk using a graphite jig, and a graphite indenter is placed on the aluminum alloy parts to obtain the desired result. Figure 1 The brazed assembly shown is placed in a high-temperature vacuum brazing furnace.

[0046] Step 2: Wait until the pressure inside the high-temperature vacuum brazing furnace decreases to 1.5 × 10⁻⁶. -3 Below Pa, start the heating program; the heating curve is as follows: Figure 2 As shown; the high temperature vacuum brazing furnace is heated to the preheating temperature of 400℃ at a heating rate of 10℃ / min and held for 10min; then heated to the connection temperature of 550℃ at a heating rate of 10℃ / min and held for 10min. At the beginning of the holding, pressure is applied to the aluminum alloy part through the graphite indenter. According to formula (1), the downward displacement of the graphite indenter is 1.08mm, and the excess liquid phase Al-Si-Mg-Cu brazing filler metal is squeezed out.

[0047] Step 3: After the heat preservation is completed, remove the pressure applied to the aluminum alloy part, cool the high temperature vacuum brazing furnace to 400°C at a rate of 5°C / min, and finally let it cool naturally to room temperature.

[0048] Figure 3 is a scanning electron microscope image of the joint interface in this embodiment. As can be seen from the figure, the joint is well bonded, without defects such as cracks or voids, and there are no brazing seams at the interface. It is composed only of an aluminum alloy matrix, and no brittle intermetallic compounds are generated. Figure 6 The diagram shows the evolution mechanism of the joint interface, indicating that the joint does not have a layered structure and there is no brazing seam. Figure 7 The results are tensile strength test results of the joints at different connection temperatures (《Metallic Materials - Tensile Testing - Part 1: Test at Room Temperature》, standard number: GB / T228.1-2010, testing instrument: electronic universal testing machine, model: MTS Model E45.106). The 6063 aluminum alloy was brazed using Al-Si-Mg-Cu brazing filler metal. When the connection temperature was 530℃, the joint had a maximum tensile strength of 115MPa. The fracture locations of the joints were all in the base material, proving that each joint has the same strength as the base material.

[0049] Example 2

[0050] This embodiment takes 6063 aluminum alloy and Al-Si-Cu solder as an example, and specifically includes the following steps:

[0051] Step 1: Machine two Φ30×40mm aluminum alloy parts from 6063 aluminum alloy using wire EDM, and ultrasonically clean them in acetone for 10 minutes. The area of ​​the surface to be welded is 15×15πmm. 2 The surfaces of the two aluminum alloy parts to be welded are mechanically ground smooth with 400-grit sandpaper, without the need for additional oxide film removal. A 50μm thick Al-Si-Cu brazing filler metal is pre-formed between the surfaces of the two aluminum alloy parts to be welded, and a solder resist is applied to the non-welding surfaces and dried. The two aluminum alloy parts are placed on a graphite disk using a graphite fixture, and a graphite pressure head is placed on the aluminum alloy parts to obtain a brazed assembly. The brazed assembly is then placed in a high-temperature vacuum brazing furnace.

[0052] Step 2: Wait until the pressure inside the high-temperature vacuum brazing furnace decreases to 1.5 × 10⁻⁶. -3 Below Pa, the high-temperature vacuum brazing furnace is heated to the preheating temperature of 400℃ at a heating rate of 10℃ / min and held for 10min; then heated to the connection temperature of 520℃ at a heating rate of 10℃ / min and held for 10min. At the beginning of the holding, pressure is applied to the aluminum alloy part through the graphite indenter. According to formula (1), the downward displacement of the graphite indenter is 1.03mm, and the excess liquid phase Al-Si-Cu brazing filler is squeezed out.

[0053] Step 3: After the heat preservation is completed, remove the pressure applied to the aluminum alloy part, cool the high temperature vacuum brazing furnace to 400°C at a rate of 5°C / min, and finally let it cool naturally to room temperature.

[0054] Figure 4 is a scanning electron microscope image of the joint interface in this embodiment. It can be seen that the joint is well bonded, without defects such as cracks or voids, and there are no brazing seams at the interface. It is composed only of an aluminum alloy matrix, and no brittle intermetallic compounds are generated. Figure 8 The results are the tensile strength test results of the joints under different brazing holding times (《Metallic Materials Tensile Testing Part 1: Test Method at Room Temperature》, standard number: GB / T 228.1-2010, the testing instrument is electronic universal testing machine, model: MTS Model E45.106). 6063 aluminum alloy was brazed using Al-Si-Cu brazing filler metal. When the brazing holding time varied between 5-30 min, the maximum shear strength of the joint was obtained at 10 min, which was 118 MPa. The fracture location of the joints was always in the base material, proving that each joint has the same strength as the base material.

[0055] Example 3

[0056] This embodiment takes 6061 aluminum alloy and Al-Si-Cu solder as an example, and specifically includes the following steps:

[0057] Step 1: Machine 6061 aluminum alloy into two Φ30×40mm parts using wire EDM and ultrasonically clean them in acetone for 10 minutes. The area of ​​the surface to be welded is 15×15πmm. 2 The surfaces of the two aluminum alloy parts to be welded are mechanically ground smooth with 400-grit sandpaper, without the need for additional oxide film removal. A 50μm thick Al-Si-Cu brazing filler metal is pre-formed between the surfaces of the two aluminum alloy parts to be welded, and a solder resist is applied to the non-welding surfaces and dried. The two aluminum alloy parts are placed on a graphite disk using a graphite fixture, and a graphite pressure head is placed on the aluminum alloy parts to obtain a brazed assembly. The brazed assembly is then placed in a high-temperature vacuum brazing furnace.

[0058] Step 2: Wait until the pressure inside the high-temperature vacuum brazing furnace decreases to 1.5 × 10⁻⁶. -3 Below Pa, the high-temperature vacuum brazing furnace is heated to the preheating temperature of 400℃ at a heating rate of 10℃ / min and held for 10min; then heated to the connection temperature of 520℃ at a heating rate of 10℃ / min and held for 10min. At the beginning of the holding, pressure is applied to the aluminum alloy part through the graphite indenter. According to formula (1), the downward displacement of the graphite indenter is 1.04mm, and the excess liquid phase Al-Si-Cu brazing filler is squeezed out.

[0059] Step 3: After the heat preservation is completed, remove the pressure applied to the aluminum alloy part, cool the high temperature vacuum brazing furnace to 400°C at a rate of 5°C / min, and finally let it cool naturally to room temperature.

[0060] Figure 5 is a scanning electron microscope image of the joint interface in this embodiment. It can be seen that the joint is well bonded, without defects such as cracks or voids, and there are no brazing seams at the interface. It is composed only of an aluminum alloy matrix, and no brittle intermetallic compounds are generated.

[0061] Example 4

[0062] This embodiment takes the brazing of a multi-microchannel component using 6063 aluminum alloy and Al-Si-Mg-Cu solder as an example, and specifically includes the following steps:

[0063] Step 1: Machine 6063 aluminum alloy into a 200×200×50mm plate and a 200×200×10mm cover plate using wire EDM. Machine multiple 2mm wide flow channels on the plate surface. Ultrasonically clean the plate and cover plate in acetone for 10 minutes. Mechanically grind the surfaces to be welded on the plate and cover plate with 400-grit sandpaper until smooth. Pre-form a 50μm thick Al-Si-Mg-Cu solder between the welding surfaces of the plate and cover plate. Apply solder resist to the non-welding surfaces and allow them to dry. Assemble the cover plate and plate to form the desired shape. Figure 9 The assembly shown is placed in a high-temperature vacuum brazing furnace.

[0064] Step 2: Wait until the pressure inside the high-temperature vacuum brazing furnace decreases to 1.5 × 10⁻⁶. -3 Below Pa, the high-temperature vacuum brazing furnace is heated to a preheating temperature of 400℃ at a heating rate of 10℃ / min and held for 10min; then heated to a connection temperature of 550℃ at a heating rate of 10℃ / min and held for 10min. At the beginning of the holding period, pressure is applied to the cover plate through the graphite indenter. According to formula (1), the downward displacement of the graphite indenter is 0.83mm, and the excess liquid phase Al-Si-Cu brazing filler metal is squeezed out.

[0065] Step 3: After the heat preservation is completed, remove the pressure applied to the cover plate, cool the high temperature vacuum brazing furnace to 400℃ at a rate of 5℃ / min, and finally let it cool naturally to room temperature.

[0066] A comparison of Examples 1, 2, and 3 shows that the present invention is applicable to connecting different aluminum alloys using different Al-Si based brazing fillers, demonstrating strong versatility. A comparison of Examples 1 and 4 shows that the method of the present invention is also applicable to connecting cold plates in large-size aluminum alloy microchannel heat exchangers, demonstrating strong applicability.

[0067] In summary, those skilled in the art can obtain brazed joints of aluminum alloys by referring to the content of this article and adjusting the brazing process parameters appropriately according to actual conditions, and the tensile strength of the joint is equal to that of the base material.

[0068] Any aspects not covered in this invention are applicable to existing technologies.

Claims

1. A green liquid-phase assisted brazing method for connecting complex multilayer aluminum alloy microchannel structures, characterized in that, The method includes the following steps: Step 1: Grind the surfaces of the two aluminum alloy parts to be welded flat. Pre-form Al-Si based brazing filler metal between the surfaces of the two aluminum alloy parts to be welded, with a brazing filler metal pre-formation thickness of 20-50 μm. Coat the non-welding surfaces of the aluminum alloy parts evenly with solder resist and dry them. Place the two aluminum alloy parts as a whole in a high-temperature vacuum brazing furnace. Step 2: Wait for the pressure inside the high-temperature vacuum brazing furnace to drop to 1.5 × 10⁻⁶. -3 Below Pa, the high-temperature vacuum brazing furnace is heated to the preheating temperature at a rate of 10℃ / min and held for 5~30min; then heated to the connection temperature at a rate of 10℃ / min and held for 5~30min. At the beginning of the holding, pressure is quickly applied to the aluminum alloy part through the pressure head to squeeze out the excess liquid phase brazing material. The total downward displacement after the pressure head touches the aluminum alloy part satisfies equation (1). （1） In the formula: This refers to the total downward displacement after the pressure head contacts the aluminum alloy part. The coefficient of linear expansion of aluminum alloy. The total height of the two aluminum alloy components along the pressure direction. Pre-set thickness for brazing filler metal; Step 3: After the heat preservation is completed, the pressure applied to the aluminum alloy parts is removed, and the high-temperature vacuum brazing furnace is cooled to a certain temperature at a rate of 5℃ / min. The liquid phase Al-Si based brazing filler metal solidifies and forms a reliable connection with the two aluminum alloy parts. Finally, the furnace is allowed to cool naturally to room temperature.

2. The green liquid-phase assisted brazing method for connecting complex multilayer aluminum alloy microchannel structures according to claim 1, characterized in that, The Al-Si based solder is one of Al-Si-Mg, Al-Si-Cu, or Al-Si-Mg-Cu solder.

3. The green liquid-phase assisted brazing method for connecting complex multilayer aluminum alloy microchannel structures according to claim 1, characterized in that, The aluminum alloy parts are made of either 6063 or 6061 aluminum alloy.

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