Paste-like solder for vacuum soldering without flux, manufacturing process and application methods thereof

Abstract

A paste-like solder for vacuum soldering without flux, characterized in that the paste-like solder for vacuum soldering without flux consists of 45%-60% solder alloy powder and 40%-55% binder by mass; wherein the paste-like solder contains no flux; and wherein the solder alloy powder is made from 6%-10% Mg, 15%-20% Cu and 70%-75% Al by mass; and wherein the binder consists of 75%-85% hexanediol, 8%-12% rosin resin, 2%-6% 1-decanol and 1.5%-4% glycerol by mass; and wherein the particle size of the solder alloy powder is less than 49 µm.

Description

TECHNICAL AREA

[0001] The present invention relates to a paste-like solder for vacuum brazing of aluminum-based composite materials, a manufacturing process and a method of use thereof. STATE OF THE ART

[0002] In recent years, with the development of science and technology, SiCp / Al composites have attracted increasing attention from researchers. Due to their high specific strength, high specific modulus, high temperature resistance, corrosion resistance, wear resistance, good thermal conductivity, low coefficient of linear expansion, and good radiation resistance, SiCp / Al composites have great potential applications in the aerospace, defense, electronics, automotive, and instrumentation sectors, particularly in the electronic packaging of phased-array radar transceiver modules. Their lightweight design, thermal conductivity, and antiresonance properties make SiCp / Al composites especially desirable. Currently, vacuum brazing is commonly used for soldering SiCp / Al composites.However, the solders currently used for soldering SiCp / Al composites are mostly foil or strip-shaped, and these foil or strip-shaped solders, produced by centrifugal or rolling processes, are often very brittle, which is detrimental to workpiece clamping and no longer meets the requirements of modern soldering production. For some components to be soldered with relatively complex and irregular shapes, paste-like solders offer ease of use, good conformability, solder savings, and good production efficiency, and are suitable for automated soldering processes.A typical paste-like solder consists of a solder alloy powder, a flux, and a binder. The flux is primarily used to remove the oxide film from the surface of the composite material during the soldering process. However, the flux cannot usually be completely drained during soldering, and the flux remaining in the solder joint will impair the performance of the soldered connection. Therefore, it is necessary to develop a paste-like solder without flux. CONTENT OF THE PRESENT INVENTION

[0003] The present invention provides a paste-like solder for vacuum soldering without flux, a manufacturing method and a method of use thereof, to solve the problem of currently existing paste-like solders that the flux cannot be completely drained from the solder joint, which leads to electrochemical corrosion at the solder joint, thereby impairing the performance of the solder joint.A paste-like solder for vacuum soldering without flux according to the present invention consists, according to mass fraction, of 45%-60% solder alloy powder and 40%-55% binder; wherein the paste-like solder contains no flux; and wherein, according to mass fraction, the solder alloy powder is made from 6%-10% Mg, 15%-20% Cu and 70%-75% Al; and wherein, according to mass fraction, the binder consists of 75%-85% hexanediol, 8%-12% rosin resin, 2%-6% 1-decanol and 1.5%-4% glycerol; and wherein the particle size of the solder alloy powder is less than 49 µm.

[0004] The manufacturing process for the paste-like solder for vacuum soldering without flux according to the present invention is carried out in the following steps: 1. Production of solder alloy powders: ① Weighing of aluminium-magnesium alloy, copper and aluminium as raw materials according to the mass fraction of 6%-10% Mg, 15%-20% Cu and 70%-75% Al; wherein the Mg content in the aluminium-magnesium alloy is 50%; 2. Clean aluminum with ultrasound for 10-20 minutes, then clean aluminum with alcohol for 10-15 minutes, blow off the remaining alcohol on the surface with a blower to obtain clean aluminum; place copper in a 5-10% HCl solution and clean for 10-15 minutes, then place in deionized water and clean for 10-15 minutes, blow off the remaining liquid on the surface with a blower to obtain clean copper; ③ Wiping the inside of the induction melting furnace and crucible with alcohol and drying with a blower, placing the clean aluminum and copper into the crucible; ④ Transferring the crucible to the induction melting furnace and closing the furnace door, switching on the mechanical pump to evacuate the induction melting furnace, and switching off the mechanical pump when the vacuum level reaches 1Pa-10Pa; ⑤ Open the inflation valve and charge with argon gas until the internal pressure of the induction melting furnace is identical to the external pressure; ⑥ Switch on the heating device of the melting furnace, adjust the current frequency to heat until the metals in the crucible are melted, continuously shake the crucible lever so that the molten metals are evenly mixed; switch off the heating device after the metals have completely melted and been evenly mixed, allow the metal solution in the crucible to cool naturally for 1-3 minutes to obtain a metal solution; ⑦ Pouring the metal solution into a mold containing an aluminum-magnesium alloy when the color of the metal solution is dark red to obtain an alloy block, followed by placing the alloy block into the crucible; ⑧ Repeat steps ④ to ⑥ twice, then pour the recovered metal solution into the mold to obtain a columnar solder alloy; ⑨ Cutting the columnar solder alloy to obtain a block-shaped solder; wherein the particle size of the block-shaped solder is less than 3 mm; ⑩ First clean the block-shaped solder with ultrasound for 10-20 minutes and then with alcohol for 10-15 minutes, blowing off the alcohol remaining on the surface with a blower to obtain a clean block-shaped solder; ⑪ Clean the agate ball tank of the low-temperature planetary ball mill with alcohol and dry with a blower; add clean, block-shaped solder in a ball-to-material ratio of 20:1 to the agate ball tank; pour acetone into the agate ball tank until the acetone covers the agate balls; set the ball mill parameter to 550 rpm and the ball milling time to 20-24 hours; obtain a mixed solution of acetone and powdered solder; ⑫ Pouring the mixed solution of acetone and powdered solder into the drying tray, placing it in the vacuum drying oven and drying, with a vacuum level of -0.1Pa and a temperature set to 60 °C to obtain a solder alloy powder after drying; ⑬ Passing the solder alloy powder through a 200-mesh sieve after drying to obtain a solder alloy powder with a particle size of less than 49 µm; 2. Preparation of the binder: Pour 75%-85% hexanediol, 8%-12% rosin resin, 2%-6% 1-decanol and 1.5%-4% glycerin according to mass fraction into a beaker and place it in a water bath oven at constant temperature, setting the temperature to 80-90°C, stirring continuously with a glass rod to obtain a uniformly mixed binder; 3. Mixing: Weighing 45%-60% solder alloy powders and 40%-55% binder according to mass fraction and placing in a vacuum mixer, stirring thoroughly for 20 minutes to obtain a paste-like solder for vacuum soldering without flux.

[0005] The method of using the paste-like solder for vacuum soldering without flux according to the present invention is carried out in the following steps: 1. Cutting the sample to be soldered into sheet-shaped samples of 20mm×10mm×2mm using an electric spark cutting machine and sanding the sample successively with 400#, 600#, 800#, and 1000# sandpaper; cleaning the sanded sample first with ultrasound for 15-20 minutes and then with alcohol for 10-15 minutes; blowing off any alcohol remaining on the surface with a blower to obtain a clean sample to be soldered; the sample to be soldered being an aluminum-based composite material reinforced with silicon carbide particles; 2. Using a brush to brush the paste-like solder for vacuum soldering without flux onto the surface of the clean sample to be soldered, using an overlapping soldering method, and placing the overlapped sample on a 304 stainless steel clamping device and applying a pressure of 1.5MPa-2MPa; 3. Place the clamped sample in the vacuum oven and perform soldering; set the process parameters as follows: heating rate of 10°C / min, soldering temperature of 580°C, holding time of 30 minutes and vacuum level of less than 5×10 -4 Pa, cool in the oven after soldering is complete at 180°C and remove.

[0006] The present invention has the following advantages: 1. The present invention uses solder alloy powders with a uniform particle size and good degree of formability and a binder with a viscosity of 5 to 7 cp, which are uniformly mixed according to the mass fraction, to produce a paste-like solder for vacuum brazing of SiCp / Al composites; for some components with complex structure and irregular shape, the difficulties of currently existing foil-shaped or strip-shaped solders in brazing and assembly as well as in the operation of irregular precision parts with complex shape and the disadvantages for the automated production of solder joints are solved, and the problems of conventional paste-like solders with flux, namely that the flux residues remain in the brazing joint and cannot be drained off, are also solved;The present invention has the advantages of being easy to use, saving solder, being suitable for automated production, and improving the strength and airtightness of the solder joint. The paste-like solder in the present invention contains no flux, thus avoiding the problem of flux not being able to drain from the solder joint during the soldering process and the relatively difficult-to-clean residues after soldering, which can lead to electrochemical corrosion. The present invention is easy to operate and highly adaptable, thereby improving the solder stability and production efficiency of SiCp / Al composites. 2. In comparison to the patent / patent application “a paste-like solder for brazing composite materials and a manufacturing process and method of use thereof” (CN103100800 A) and “a paste-like aluminum alloy solder with medium temperature and its manufacturing process” (CN108436324 A), the paste-like solder according to the present invention contains no flux and consists only of a solder alloy powder and a binder.When soldering a SiCp / Al composite material using the paste-like solder produced by the present invention in a vacuum atmosphere, the composite material exhibits a large difference between the coefficient of expansion of the oxide film on the surface of the composite and the coefficient of expansion of the base material during the heating process, and the film on the surface of the composite material will automatically break down. At the same time, the paste-like solder produced by the present invention uses a highly active solder alloy powder that exhibits a certain self-soldering effect. Therefore, by using the paste-like solder produced by the present invention under a vacuum atmosphere, a function can be achieved to eliminate the oxide film on the surface of the SiCp / Al composite material in order to achieve good metal soldering. 3. In comparison to the patent / patent application “a paste-like solder for brazing composite materials and a manufacturing process and method of use thereof” (CN103100800 A) and “a paste-like aluminum alloy solder with medium temperature and its manufacturing process” (CN108436324 A), the present invention avoids the deficiency that the flux cannot be completely drained from the brazing joint, thereby reducing the hidden risk of electrochemical corrosion at the brazing joint, reducing manufacturing costs, and achieving ease of use, while simultaneously improving the strength and airtightness of the brazed connection. BRIEF DESCRIPTION OF THE DRAWING Fig. Figure 1 shows a physical diagram of a solder alloy powder produced in step 1 of a second embodiment; Fig. Figure 2 shows a physical diagram of a binder produced in step 2 of a second embodiment; Fig. Figure 3 shows a physical diagram of a paste-like solder produced in step 3 of a second embodiment for vacuum soldering without flux. DETAILED DESCRIPTION

[0007] Detailed embodiment 1: In the present embodiment, a paste-like solder for vacuum soldering without flux consists, according to mass fraction, of 45%-60% solder alloy powder and 40%-55% binder; wherein the paste-like solder contains no flux; and wherein, according to mass fraction, the solder alloy powder is made from 6%-10% Mg, 15%-20% Cu and 70%-75% Al; and wherein, according to mass fraction, the binder consists of 75%-85% hexanediol, 8%-12% rosin resin, 2%-6% 1-decanol and 1.5%-4% glycerol; and wherein the particle size of the solder alloy powder is less than 49 µm.

[0008] Detailed embodiment 2: The difference between the present embodiment and the first detailed embodiment is that the paste-like solder for vacuum soldering without flux is further enhanced with a transition group element, the amount of which is 0.1%–3.5%. Otherwise, it is the same as the first detailed embodiment.

[0009] Detailed embodiment 3: The difference between the present embodiment and the first or second detailed embodiment is that the transition group element is Ti. Otherwise, it is the same as the first or second detailed embodiment.

[0010] Detailed embodiment 4: The manufacturing process for the paste-like solder for vacuum soldering without flux in the present embodiment is carried out with the following steps: 1. Production of solder alloy powders: ① Weighing of aluminium-magnesium alloy, copper and aluminium as raw materials according to the mass fraction of 6%-10% Mg, 15%-20% Cu and 70%-75% Al; wherein the Mg content in the aluminium-magnesium alloy is 50%; 2. Clean aluminum with ultrasound for 10-20 minutes, then clean aluminum with alcohol for 10-15 minutes, blow off the remaining alcohol on the surface with a blower to obtain clean aluminum; place copper in a 5-10% HCl solution and clean for 10-15 minutes, then place in deionized water and clean for 10-15 minutes, blow off the remaining liquid on the surface with a blower to obtain clean copper; ③ Wiping the inside of the induction melting furnace and crucible with alcohol and drying with a blower, placing the clean aluminum and copper into the crucible; ④ Transferring the crucible to the induction melting furnace and closing the furnace door, switching on the mechanical pump to evacuate the induction melting furnace, and switching off the mechanical pump when the vacuum level reaches 1Pa-10Pa; ⑤ Open the inflation valve and charge with argon gas until the internal pressure of the induction melting furnace is identical to the external pressure; ⑥ Switch on the heating device of the melting furnace, adjust the current frequency to heat until the metals in the crucible are melted, continuously shake the crucible lever so that the molten metals are evenly mixed; switch off the heating device after the metals have completely melted and been evenly mixed, allow the metal solution in the crucible to cool naturally for 1-3 minutes to obtain a metal solution; ⑦ Pouring the metal solution into a mold containing an aluminum-magnesium alloy when the color of the metal solution is dark red to obtain an alloy block, followed by placing the alloy block into the crucible; ⑧ Repeat steps ④ to ⑥ twice, then pour the recovered metal solution into the mold to obtain a columnar solder alloy; ⑨ Cutting the columnar solder alloy to obtain a block-shaped solder; where the particle size of the block-shaped solder is less than 3 mm; ⑩ First clean the block-shaped solder with ultrasound for 10-20 minutes and then with alcohol for 10-15 minutes, blowing off the alcohol remaining on the surface with a blower to obtain a clean block-shaped solder; ⑪ Clean the agate ball tank of the low-temperature planetary ball mill with alcohol and dry with a blower; add clean, block-shaped solder in a ball-to-material ratio of 20:1 to the agate ball tank; pour acetone into the agate ball tank until the acetone covers the agate balls; set the ball mill parameter to 550 rpm and the ball milling time to 20-24 hours; obtain a mixed solution of acetone and powdered solder; ⑫ Pouring the mixed solution of acetone and powdered solder into the drying tray, placing it in the vacuum drying oven and drying, with a vacuum level of -0.1Pa and a temperature set to 60 °C to obtain a solder alloy powder after drying; ⑬ Passing the solder alloy powder through a 200-mesh sieve after drying to obtain a solder alloy powder with a particle size of less than 49 µm; 2. Preparation of the binder: Casting of 75%-85% hexanediol, 8%-12% rosin resin, 2%-6% 1-decanol and Place 1.5%-4% glycerin, according to the mass fraction, into a beaker and place it in a water bath oven at a constant temperature, setting the temperature to 80-90°C, stirring continuously with a glass rod to obtain a uniformly mixed binder; 3. Mixing: Weighing 45%-60% solder alloy powders and 40%-55% binder according to mass fraction and placing in a vacuum mixer, stirring thoroughly for 20 minutes, to obtain a paste-like solder for vacuum soldering without flux.

[0011] The cleaning solution used in the ultrasonic cleaning process in the present embodiment uses a mixed solution of alcohol and acetone in a volume ratio of 1:1.

[0012] Detailed embodiment 5: The difference between the present embodiment and the fourth detailed embodiment is that the paste-like solder obtained in step 3 for vacuum soldering without flux is further enhanced with a transition group element, wherein the amount of the transition group element added is 0.1%–3.5%. This is otherwise identical to the fourth detailed embodiment.

[0013] Detailed embodiment 6: The difference between the present embodiment and the fourth or fifth detailed embodiment is that the transition group element is Ti, which is provided by a titanium-aluminum alloy and melted together with pure aluminum and pure copper; and wherein the Ti content in the titanium-aluminum alloy is 10%. Otherwise, it is the same as the fourth or fifth detailed embodiment. Due to its low price and high activity, the Ti element can react with silicon carbide ceramics. By adding the Ti element to the solder, a better soldering effect can be achieved.

[0014] Detailed embodiment 7: The method of use for the paste-like solder for vacuum soldering without flux in the present embodiment is carried out with the following steps: 1. Cutting the sample to be soldered into sheet-shaped samples of 20mm×10mm×2mm using an electric spark cutting machine and sanding the sample successively with 400#, 600#, 800#, and 1000# sandpaper; cleaning the sanded sample first with ultrasound for 15-20 minutes and then with alcohol for 10-15 minutes; blowing off any alcohol remaining on the surface with a blower to obtain a clean sample to be soldered; the sample to be soldered being an aluminum-based composite material reinforced with silicon carbide particles; 2. Using a brush to brush the paste-like solder for vacuum soldering without flux onto the surface of the clean sample to be soldered, using an overlapping soldering method, and placing the overlapped sample on a 304 stainless steel clamping device and applying a pressure of 1.5MPa-2MPa; 3. Place the clamped sample in the vacuum oven and perform soldering; set the process parameters as follows: heating rate of 10°C / min, soldering temperature of 580°C, holding time of 30 minutes and vacuum level of less than 5×10 -4 Pa, cool in the oven after soldering is complete at 180°C and remove.

[0015] Detailed embodiment 8: The difference between the present embodiment and the seventh detailed embodiment is that the paste-like solder for vacuum brazing without flux is also suitable for vacuum brazing SiCp / Al composites with Kovar alloys, high-silicon aluminum, or other aluminum alloys. This is the same as the fourth detailed embodiment.

[0016] Detailed embodiment 9: The difference between the present embodiment and the seventh or eighth detailed embodiment lies in the fact that the vacuum furnace in step 3 is a vacuum tube furnace. Otherwise, it is the same as the seventh or eighth detailed embodiment.

[0017] The following exemplary embodiments demonstrate the advantages of the present invention: Exemplary embodiment 1: A manufacturing process for the paste-like solder for vacuum soldering without flux is carried out with the following steps: 1. Production of solder alloy powders: ① Weighing of 16% aluminium-magnesium alloy, 17% copper and 67% aluminium as raw materials according to mass fraction; wherein the Mg content in the aluminium-magnesium alloy is 50%; 2. Clean aluminum with ultrasound for 15 minutes, then clean aluminum with alcohol for 10 minutes, blow off the remaining alcohol on the surface with a blower to obtain clean aluminum; place copper in a 5% HCl solution and clean for 10 minutes, then place in deionized water and clean for 10 minutes, blow off the remaining liquid on the surface with a blower to obtain clean copper; ③ Wiping the inside of the induction melting furnace and crucible with alcohol and drying with a blower, placing the clean aluminum and copper into the crucible; ④ Transferring the crucible to the induction melting furnace and closing the furnace door, switching on the mechanical pump to evacuate the induction melting furnace, and switching off the mechanical pump when the vacuum level reaches 8Pa; ⑤ Open the inflation valve and charge with argon gas until the internal pressure of the induction melting furnace is identical to the external pressure; ⑥ Switch on the heating device of the melting furnace, adjust the current frequency to heat until the metals in the crucible are melted, continuously shake the crucible lever so that the molten metals are evenly mixed; switch off the heating device after the metals have completely melted and been evenly mixed, allow the metal solution in the crucible to cool naturally for 1-3 minutes to obtain a metal solution; ⑦ Pouring the metal solution into a mold containing an aluminum-magnesium alloy when the color of the metal solution is dark red to obtain an alloy block, followed by placing the alloy block into the crucible; ⑧ Repeat steps ④ to ⑥ twice, then pour the recovered metal solution into the mold to obtain a columnar solder alloy; ⑨ Cutting the columnar solder alloy to obtain a block-shaped solder; where the particle size of the block-shaped solder is less than 3 mm; ⑩ First clean the block-shaped solder with ultrasound for 10 minutes and then with alcohol for 10-15 minutes, blowing off the alcohol remaining on the surface with a blower to obtain a clean block-shaped solder; ⑪ Clean the agate ball tank of the low-temperature planetary ball mill with alcohol and dry with a blower; add clean, block-shaped solder in a ball-to-material ratio of 20:1 to the agate ball tank; pour acetone into the agate ball tank until the acetone covers the agate balls; set the ball mill parameter to 550 rpm and the ball milling time to 20 hours; obtain a mixed solution of acetone and powdered solder; ⑫ Pouring the mixed solution of acetone and powdered solder into the drying tray, placing it in the vacuum drying oven and drying, with a vacuum level of -0.1Pa and a temperature set to 60 °C to obtain a solder alloy powder after drying; ⑬ Passing the solder alloy powder through a 200-mesh sieve after drying to obtain a solder alloy powder with a particle size of less than 49 µm; 2. Preparation of the binder: Pour 80% hexanediol, 11% rosin resin, 6% 1-decanol and 3% glycerin according to mass fraction into a beaker and place it in a water bath oven at constant temperature, set the temperature to 85 °C, continuously stir with a glass rod to obtain a uniformly mixed binder; 3. Mixing: Weighing 55% solder alloy powders and 45% binder according to mass fraction and placing in a vacuum mixer, stirring thoroughly for 20 minutes to obtain a paste-like solder for vacuum soldering without flux. Example 2: A manufacturing process for the paste-like solder for vacuum soldering without flux is carried out with the following steps: 1. Production of solder alloy powders: ① Weighing of 16% aluminium-magnesium alloy, 17% copper, 10% titanium-aluminium alloy and 57% aluminium as raw materials according to mass fraction; wherein the Mg content in the aluminium-magnesium alloy is 50%; and wherein the Ti content in the titanium-aluminium alloy is 10%. 2. Clean the titanium-aluminum alloy with ultrasound for 15 minutes, then clean with alcohol for 10 minutes, blow off any remaining alcohol from the surface with a blower to obtain a clean titanium-aluminum alloy; clean aluminum with ultrasound for 15 minutes, then clean with alcohol for 10 minutes, blow off any remaining alcohol from the surface with a blower to obtain clean aluminum; immerse copper in a 5% HCl solution and clean for 10 minutes, then immerse in deionized water and clean for 10 minutes, blow off any remaining liquid from the surface with a blower to obtain clean copper; ③ Wiping the inside of the induction melting furnace and crucible with alcohol and drying with a blower, placing the clean titanium-aluminium alloy and the clean aluminum and copper into the crucible; ④ Transferring the crucible to the induction melting furnace and closing the furnace door, switching on the mechanical pump to evacuate the induction melting furnace, and switching off the mechanical pump when the vacuum level reaches 8Pa; ⑤ Open the inflation valve and charge with argon gas until the internal pressure of the induction melting furnace is identical to the external pressure; ⑥ Switch on the heating device of the melting furnace, adjust the current frequency to heat until the metals in the crucible are melted, continuously shake the crucible lever so that the molten metals are evenly mixed; switch off the heating device after the metals have completely melted and been evenly mixed, allow the metal solution in the crucible to cool naturally for 1-3 minutes to obtain a metal solution; ⑦ Pouring the metal solution into a mold containing an aluminum-magnesium alloy when the color of the metal solution is dark red to obtain an alloy block, followed by placing the alloy block into the crucible; ⑧ Repeat steps ④ to ⑥ twice, then pour the recovered metal solution into the mold to obtain a columnar solder alloy; ⑨ Cutting the columnar solder alloy to obtain a block-shaped solder; wherein the particle size of the block-shaped solder is less than 3 mm; ⑩ First clean the block-shaped solder with ultrasound for 10 minutes and then with alcohol for 10-15 minutes, blowing off the alcohol remaining on the surface with a blower to obtain a clean block-shaped solder; ⑪ Clean the agate ball tank of the low-temperature planetary ball mill with alcohol and dry with a blower; add clean, block-shaped solder in a ball-to-material ratio of 20:1 to the agate ball tank; pour acetone into the agate ball tank until the acetone covers the agate balls; set the ball mill parameter to 550 rpm and the ball milling time to 20 hours; obtain a mixed solution of acetone and powdered solder; ⑫ Pouring the mixed solution of acetone and powdered solder into the drying tray, placing it in the vacuum drying oven and drying, with a vacuum level of -0.1Pa and a temperature set to 60 °C to obtain a solder alloy powder after drying; ⑬ Passing the solder alloy powder through a 200-mesh sieve after drying to obtain a solder alloy powder with a particle size of less than 49 µm; 2. Preparation of the binder: Pour 80% hexanediol, 11% rosin resin, 6% 1-decanol and 3% glycerin according to mass fraction into a beaker and place it in a water bath oven at constant temperature, set the temperature to 85 °C, continuously stir with a glass rod to obtain a uniformly mixed binder; 3. Mixing: Weighing 55% solder alloy powders and 45% binder according to mass fraction and placing in a vacuum mixer, stirring thoroughly for 20 minutes to obtain a paste-like solder for vacuum soldering without flux. Fig. Figure 1 shows a physical diagram of a solder alloy powder produced in step 1 of a second embodiment; Fig. Figure 2 shows a physical diagram of a binder produced in step 2 of a second embodiment; Fig.Figure 3 shows a physical diagram of a paste-like solder for fluxless vacuum soldering produced in step 3 of a second embodiment. The figures show that the product has a uniform particle size and a good degree of formability. Exemplary embodiment 3: The difference between the present exemplary embodiment and the second exemplary embodiment is as follows: Weighing 16% aluminium-magnesium alloy, 17% copper, 20% titanium-aluminium alloy and 47% aluminium as raw materials according to the mass fraction in step ①; wherein the Mg content in the aluminium-magnesium alloy is 50%; and wherein the Ti content in the titanium-aluminium alloy is 10%. Exemplary embodiment 4: The paste-like solders for vacuum soldering without flux obtained in exemplary embodiments 1 to 3 are each used for soldering, the work steps being as follows: 1. Cutting the sample to be soldered into sheet-shaped samples of 20mm×10mm×2mm using an electric spark cutting machine and successively sanding the sample with 400#, 600#, 800#, and 1000# sandpaper; cleaning the sanded sample first with ultrasound for 10 minutes and then with alcohol for 10 minutes; blowing off any alcohol remaining on the surface with a blower to obtain a clean sample to be soldered; the sample to be soldered being an aluminum-based composite material reinforced with silicon carbide particles; 2. Using a brush to brush the paste-like solder for vacuum soldering without flux onto the surface of the clean sample to be soldered, using an overlapping soldering method, and placing the overlapped sample on a 304 stainless steel clamping device and applying a pressure of 1.5MPa-2MPa; 3. Place the clamped sample in the vacuum oven and perform soldering; set the process parameters as follows: heating rate of 10°C / min, soldering temperature of 580°C, holding time of 30 minutes and vacuum level of less than 2×10 -5 Pa, cool in the oven after soldering is complete at 180°C and remove.

[0018] A paste-like solder obtained in the first embodiment for vacuum soldering without flux is used for soldering, wherein a performance test is carried out on the sample after soldering, and wherein the shear strength is 75.45 MPa and the airtightness is 1×10 -9Pa·m3 / s is achieved. In the present embodiment, there is no binder residue at the solder joint after soldering.

[0019] A paste-like solder obtained in the second embodiment for vacuum soldering without flux is used for soldering, wherein a performance test is carried out on the sample after soldering, and wherein the shear strength is 85.75 MPa and the airtightness is 1×10 -9 Pa·m3 / s is achieved. In the present embodiment, there is no binder residue at the solder joint after soldering.

[0020] A paste-like solder obtained in the third embodiment for vacuum soldering without flux is used for soldering, wherein a performance test is carried out on the sample after soldering, and wherein the shear strength is 92.13 MPa and the airtightness is less than 1×10 -9 Pa·m3 / s.

Claims

[1] Paste-like solder for vacuum soldering without flux, characterized by , that the paste-like solder for vacuum soldering without flux consists of 45%-60% solder alloy powder and 40%-55% binder by mass; wherein the paste-like solder contains no flux; and wherein, by mass, the solder alloy powder is made of 6%-10% Mg, 15%-20% Cu and 70%-75% Al; and wherein, by mass, the binder consists of 75%-85% hexanediol, 8%-12% rosin resin, 2%-6% 1-decanol and 1.5%-4% glycerol; and wherein the particle size of the solder alloy powder is less than 49 µm. [2] Paste-like solder for vacuum soldering without flux according to claim 1, characterized by , that the paste-like solder for vacuum soldering without flux is further impregnated with a transition group element, wherein the amount added of the transition group element is 0.1%-3.5%. [3] Paste-like solder for vacuum soldering without flux according to claim 2, characterized by , that the transition group element is Ti. [4] Manufacturing process for a paste-like solder for vacuum soldering without flux according to claim 1, characterized by , that the manufacturing process for the paste-like solder for vacuum soldering without flux is carried out with the following steps:

1. Production of solder alloy powders: ① Weighing of aluminium-magnesium alloy, copper and aluminium as raw materials according to the mass fraction of 6%-10% Mg, 15%-20% Cu and 70%-75% Al; wherein the Mg content in the aluminium-magnesium alloy is 50%; 2. Clean aluminum with ultrasound for 10-20 minutes, then clean aluminum with alcohol for 10-15 minutes, blow off the remaining alcohol on the surface with a blower to obtain clean aluminum; place copper in a 5-10% HCl solution and clean for 10-15 minutes, then place in deionized water and clean for 10-15 minutes, blow off the remaining liquid on the surface with a blower to obtain clean copper; ③ Wiping the inside of the induction melting furnace and crucible with alcohol and drying with a blower, placing the clean aluminum and copper into the crucible; ④ Transferring the crucible to the induction melting furnace and closing the furnace door, switching on the mechanical pump to evacuate the induction melting furnace, and switching off the mechanical pump when the vacuum level reaches 1Pa-10Pa; ⑤ Open the inflation valve and charge with argon gas until the internal pressure of the induction melting furnace is identical to the external pressure; ⑥ Switch on the heating device of the melting furnace, adjust the current frequency to heat until the metals in the crucible are melted, continuously shake the crucible lever so that the molten metals are evenly mixed; switch off the heating device after the metals have completely melted and been evenly mixed, allow the metal solution in the crucible to cool naturally for 1-3 minutes to obtain a metal solution; ⑦ Pouring the metal solution into a mold containing an aluminum-magnesium alloy when the color of the metal solution is dark red to obtain an alloy block, followed by placing the alloy block into the crucible; ⑧ Repeat steps ④ to ⑥ twice, then pour the recovered metal solution into the mold to obtain a columnar solder alloy; ⑨ Cutting the columnar solder alloy to obtain a block-shaped solder; wherein the particle size of the block-shaped solder is less than 3 mm; ⑩ First clean the block-shaped solder with ultrasound for 15-20 minutes and then with alcohol for 10-15 minutes, blowing off the alcohol remaining on the surface with a blower to obtain a clean block-shaped solder; ⑪ Clean the agate ball tank of the low-temperature planetary ball mill with alcohol and dry with a blower; add clean, block-shaped solder in a ball-to-material ratio of 20:1 to the agate ball tank; pour acetone into the agate ball tank until the acetone covers the agate balls; set the ball mill parameter to 550 rpm and the ball milling time to 20-24 hours; obtain a mixed solution of acetone and powdered solder; ⑫ Pouring the mixed solution of acetone and powdered solder into the drying tray, placing it in the vacuum drying oven and drying, with a vacuum level of -0.1Pa and a temperature set to 60 °C to obtain a solder alloy powder after drying; ⑬ Passing the solder alloy powder through a 200-mesh sieve after drying to obtain a solder alloy powder with a particle size of less than 49 µm; 2. Preparation of the binder: Pour 75%-85% hexanediol, 8%-12% rosin resin, 2%-6% 1-decanol and 1.5%-4% glycerin according to mass fraction into a beaker and place it in a water bath oven at constant temperature, setting the temperature to 80-90°C, stirring continuously with a glass rod to obtain a uniformly mixed binder; 3. Mixing: Weighing 45%-60% solder alloy powders and 40%-55% binder according to mass fraction and placing in a vacuum mixer, stirring thoroughly for 20 minutes to obtain a paste-like solder for vacuum soldering without flux. [5] Manufacturing process for a paste-like solder for vacuum soldering without flux according to claim 4, characterized by , that the paste-like solder obtained in step 3 for vacuum soldering without flux is further mixed with a transition group element, wherein the amount added of the transition group element is 0.1%-3.5%. [6] Manufacturing process for a paste-like solder for vacuum soldering without flux according to claim 5, characterized by , that the transition group element is Ti, which is provided by a titanium-aluminium alloy and is melted together with clean aluminum and clean copper; and wherein the Ti content in the titanium-aluminium alloy is 10%. [7] Method of use for a paste-like solder for vacuum soldering without flux according to claim 1, characterized by , that the application procedure for the paste-like solder for vacuum soldering without flux is carried out with the following steps:

1. Cutting the sample to be soldered into sheet-shaped samples of 20mm×10mm×2mm using an electric spark cutting machine and sanding the sample successively with 400#, 600#, 800#, and 1000# sandpaper; cleaning the sanded sample first with ultrasound for 15-20 minutes and then with alcohol for 10-15 minutes; blowing off any alcohol remaining on the surface with a blower to obtain a clean sample to be soldered; the sample to be soldered being an aluminum-based composite material reinforced with silicon carbide particles; 2. Using a brush to brush the paste-like solder for vacuum soldering without flux onto the surface of the clean sample to be soldered, using an overlapping soldering method, and placing the overlapped sample on a 304 stainless steel clamping device and applying a pressure of 1.5MPa-2MPa; 3. Place the clamped sample in the vacuum oven and perform soldering; set the process parameters as follows: heating rate of 10°C / min, soldering temperature of 580°C, holding time of 30 minutes and vacuum level of less than 5×10-4 Pa, cool with the oven to 180°C after soldering is complete and remove. [8] Method of use for a paste-like solder for vacuum soldering without flux according to claim 7, characterized bythat the paste-like solder for vacuum soldering without flux remains suitable for vacuum soldering of SiCp / Al composites with Kovar alloys, high silicon aluminium or other aluminium alloys. [9] Method of use for a paste-like solder for vacuum soldering without flux according to claim 7, characterized by that the vacuum furnace in step 3 is a vacuum tube furnace.

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