A method for producing a brazing material

Abstract

The application belongs to the field of preparation of brazing filler metal, and particularly relates to a preparation method of brazing filler metal. The preparation method of brazing filler metal comprises the following steps: welding together upper brazing filler metal strips, at least one middle brazing filler metal strip and lower brazing filler metal strips under the action of electrode rollers; the composition of the at least one middle brazing filler metal strip is different from that of the upper brazing filler metal strips and the lower brazing filler metal strips, and the upper brazing filler metal strips, the at least one middle brazing filler metal strip and the lower brazing filler metal strips are fused into integral alloy brazing filler metal during brazing. The preparation method of brazing filler metal provided by the application can melt the composite interface of adjacent two brazing filler metal strips under the action of resistance heat and form metallurgical bonding under the pressure of electrode rollers after multiple brazing filler metal strips enter the electrode rollers, so that functional composite brazing filler metal with high integrity is obtained, the integral alloy can be conveniently fused on the basis of metallurgical bonding during brazing, the deviation of the composition of the brazing filler metal from the design or the unstable situation is reduced, and the realization of the expected weld function is ensured.

Description

Technical Field

[0001] This invention belongs to the field of brazing filler metal preparation, and specifically relates to a method for preparing brazing filler metal. Background Technology

[0002] Brazing alloys are widely used in aerospace, electrical engineering, automotive, electronics, and refrigeration appliances, earning them the reputation of being an industrial "all-purpose adhesive." Different service environments require different brazed joint properties. For example, environments requiring high sealing performance necessitate brazed joints with good flowability; environments with prolonged exposure to high salt corrosion, such as marine environments, require joints with excellent corrosion resistance; and environments subjected to long-term impact require joints with high impact resistance. Obtaining joints with these different functional characteristics necessitates the development of welding electrodes with specific functionalities.

[0003] Silver-based brazing filler metals, primarily composed of Ag, Cu, and Zn, are widely used in industries such as machinery, home appliances, and tools. However, to meet varying performance requirements, low-melting-point elements like Sn are typically added to significantly lower the melting point and improve wettability. Traditional AgCuZnSn brazing filler metals are produced by adding Sn to AgCuZn alloys through a batching process, followed by smelting, casting, rolling, extrusion, and drawing. This results in varieties such as BAg25CuZnSn, BAg30CuZnSn, BAg40CuZnSn, BAg45CuZnSn, and BAg56CuZnSn. However, the Sn content in AgCuZnSn brazing filler metals produced using this method should not be too high (generally below 2%), otherwise it will significantly reduce the plasticity of the filler metal, leading to processing difficulties, low efficiency, and low yield, thus significantly increasing the production cost of this type of brazing filler metal. Other alloying elements, such as Ni, Co, and Mn, can play a corresponding role in performance adjustment (corrosion resistance, impact resistance) by adding appropriate amounts to the base brazing filler metal (silver, copper, and zinc brazing filler metal). However, they also have similar problems as mentioned above. This leads to the overall low production efficiency and high production cost of various functional brazing filler metals in industrial production.

[0004] To address the production challenges of the aforementioned functional solders, the applicant previously proposed a composite solder structure design (CN106181124A). This composite solder comprises a composite-rolled tin layer and a solder alloy layer, with flux layers sprayed onto the outer surfaces of both the tin layer and the solder alloy layer, forming a four-layer composite solder product. The key to this composite solder lies in the composite rolling of the tin layer and the solder alloy layer. Compared to traditional methods of depositing tin layers such as electroplating, hot-dip plating, thermal spraying, and chemical plating, the composite rolling scheme using a precision rolling mill can produce a tin layer with uniform thickness and aesthetically pleasing shape.

[0005] The composite rolling scheme using precision rolling mills requires a large rolling force to form a good mechanical bond. At the same time, during use, due to the low melting point of the Sn layer, the Sn layer will melt first and easily detach from the brazing alloy layer. As a result, the amount of Sn that fuses with the brazing alloy layer to form an integral alloy is reduced or unstable. This makes it difficult to ensure that the composition of the functional composite brazing alloy meets the design during brazing, which in turn leads to the weld function not meeting expectations. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing brazing filler metal, which solves the problem that the composition of existing functional composite brazing filler metals tends to deviate from the design during brazing, thus affecting the function of the weld.

[0007] To achieve the above objectives, the technical solution adopted by this invention is as follows: A method for preparing a brazing filler metal includes the following steps: an upper brazing filler metal strip, at least one middle brazing filler metal strip, and a lower brazing filler metal strip are welded together under the action of an electrode roller; the composition of at least one of the middle brazing filler metal strips is different from that of the upper brazing filler metal strip and the lower brazing filler metal strip; the upper brazing filler metal strip, at least one middle brazing filler metal strip, and the lower brazing filler metal strip are fused together into an integral alloy brazing filler metal during brazing.

[0008] The brazing filler metal preparation method provided by this invention involves multiple brazing filler metal strips entering an electrode roller. The composite interface of two adjacent brazing filler metal strips melts under the action of resistance heating and forms a metallurgical bond under the pressure of the electrode roller, resulting in a functional composite brazing filler metal with extremely high integrity. During brazing, the metallurgical bond allows for easy fusion into an integral alloy, reducing deviations from the design or instability in the composition of the brazing filler metal and ensuring the realization of the expected weld function.

[0009] Preferably, the upper and lower brazing filler strips are silver-based or copper-based brazing filler metals, and the middle brazing filler strip is a single-element metal strip or an alloy strip. Both the upper and lower brazing filler strips are base brazing filler metals, while the middle brazing filler strip optimizes the performance of the base brazing filler metal. The upper and lower brazing filler strips can have the same or different compositions. This design divides the base brazing filler metal into two parts, allowing for more uniform fusion of the components in the middle brazing filler strip during brazing, thereby further improving the uniformity and stability of the brazing effect.

[0010] More preferably, the elemental metal strip is pure copper or pure silver, and the alloy strip is a copper alloy strip, wherein the alloying elements in the copper alloy strip are selected from one or more combinations of Sn, Ni, Co, Mn, Zn, and Ag. Combining the middle solder strip with the upper and lower solder strips allows for the rapid production of the desired composite solder. Simultaneously, the introduction of alloying elements such as Sn, Ni, Co, and Mn is generally for the purpose of preparing composite solders with specific applications. For example, Sn can significantly improve solder flowability; Ni, Mn, and Co can improve the strength and toughness of brazed joints; and Mn also has the effect of lowering the melting point of the solder. Of course, alloy strips such as CuZn and AgCu, which are related to the elemental composition of the upper and lower solder strips, can also be selected to adjust the composition of the composite solder and simplify the preparation of new solders. This method can be used to form various silver-based solders with different functions, serving as the silver-based solder for the upper and lower solder strips. The processing is mature, and commercially available finished products conforming to specifications can be directly purchased and used. The middle brazing filler strip is made of copper alloy, which facilitates the dispersion of alloying elements and provides a good composite effect with the upper and lower brazing filler strips.

[0011] Preferably, before entering the electrode roller, low-melting-point metal powder is added to the composite interface of the upper, lower, and middle brazing filler strips. The melting point of the low-melting-point metal powder is not higher than 450°C. Adding low-melting-point metal powder to the composite interface increases the interfacial resistance, which facilitates the heating and melting welding between the strips during electrode roller rolling, thus improving the bonding strength of the composite brazing filler product. Low-melting-point metal powder can be added between all composite interfaces as needed, or selectively between certain composite interfaces depending on the characteristics of different brazing filler strips.

[0012] More preferably, the thickness of the added low-melting-point metal powder is no more than 0.1 mm.

[0013] More preferably, the low-melting-point metal powder is one or a combination of two or more of Sn powder, SnAg alloy powder, and CnSn alloy powder; the Sn content in the SnAg alloy powder and CnSn alloy powder is above 90% by mass. Sn powder, SnAg alloy powder, and CuSn alloy powder are all high Sn content (>93 wt%) powders with melting temperatures below 400℃. Their main purpose is to increase the overall Sn content of the composite brazing filler metal, effectively solving the problems of processing difficulties, low efficiency, and low yield associated with traditional methods for producing high Sn (>5 wt%) brazing filler metals.

[0014] Preferably, before entering the electrode roller, the surface of the middle solder strip to be laminated, or the surface of the upper and lower solder strips to be laminated, is laser-roughened. Laser roughening can remove impurities from the solder strip surface and also provide favorable conditions for resistive contact between the solder strips.

[0015] More preferably, the laser texturing controls the surface roughness Ra ≤ 1 μm.

[0016] Preferably, the voltage applied by the electrode roller is 220~380V, the current is 1~3A, and the pressure is 10~25MPa. Using these conditions, a good welding effect can be easily achieved.

[0017] In summary, the core beneficial effects of this invention are mainly reflected in the following aspects: 1) The method of processing basic brazing filler metal and functional brazing filler metal separately reduces the processing difficulty.

[0018] 2) By using roller electrodes and resistance heating, and with full computer control, continuous production of functional composite brazing filler metal strips is achieved, significantly improving the machinability of the brazing filler metal, which helps to increase production efficiency and reduce production costs.

[0019] 3) Adding a gas shield during resistance heating can prevent oxidation during resistance heating; after welding, the composite wide strip can be directly prepared into finished composite brazing electrodes by a cutting machine and a rolling cutter.

[0020] 4) By using a single base material and combining it with various functional welding electrodes, the company can quickly switch between multiple types of functional brazing filler metal strips without affecting its normal production process.

[0021] 5) Both the basic brazing filler metal strip and the functional brazing filler metal strip can be purchased from the market, achieving separation of smelting and processing, resulting in good confidentiality of the final brazing filler metal formula and low environmental pollution. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the apparatus for preparing functional composite solder according to the present invention; Among them, 1-upper unwinding roller; 2-lower unwinding roller; 3-middle unwinding roller; 4-electrode roller; 5-gas protection box; 6-cutting machine; 7-roll cutting machine; 8-finished functional composite brazing electrode; Figure 2 This is a microscopic interface structure diagram of the functional composite solder prepared in Example 1 of the present invention; Figure 3 This is a microscopic interface structure diagram of the functional composite solder prepared in Example 2 of the present invention. Detailed Implementation

[0023] To address the challenges of preparing existing functional composite brazing filler metals and their high production costs, this invention proposes a method for the continuous preparation of functional composite brazing filler metals. The method primarily involves welding an upper brazing filler strip, at least one middle brazing filler strip, and a lower brazing filler strip together under the action of an electrode roller. The composition of at least one of the middle brazing filler strips differs from that of the upper and lower brazing filler strips. During brazing, the upper brazing filler strip, at least one middle brazing filler strip, and the lower brazing filler strip are fused together to form a monolithic alloy brazing filler metal.

[0024] The above method is applicable to different series of solders, such as silver-based and copper-based solders, and can obtain components with different compositions and properties, which is beneficial not only to solder production but also to solder application. This method also facilitates rapid switching between different product types and mass production, reducing production costs.

[0025] A schematic diagram of the apparatus for preparing functional composite solder according to the present invention is shown below. Figure 1 As shown, it includes an unwinding device, electrode rollers, a shearing machine, and a rolling cutter.

[0026] The unwinding device includes an upper unwinding roller 1, a lower unwinding roller 2, and a middle unwinding roller 3, used for unwinding the upper, lower, and middle brazing filler metal strips, respectively. The electrode roller 4 is housed inside a protective gas chamber 5 to prevent oxidation of the solder surface during heating; the protective gas can be an inert gas or a reducing gas. A shearing machine 6 and a rolling cutter 7 are sequentially located downstream of the electrode rollers to cut the formed composite solder strip, obtaining the finished functional composite brazing filler electrode 8.

[0027] Preferably, the electrode roller has a hollow structure, and coolant can be introduced into the interior to cool the electrode roller. The coolant can be selected from one or more of water, methoxy-nonafluorobutane, 2-(trifluoromethyl)-3-ethoxydodecylfluorohexane, nonafluoroisobutyl ether, and C5-18-perfluoroane electronic fluorinated liquid.

[0028] The following is a detailed description of the brazing filler metal production method based on the above-described apparatus, which comprises the following steps: (1) Production of conventional brazing solder strips (upper and lower brazing solder strips) a. Place the raw materials with the prepared basic components in a smelting furnace for smelting and then cast them into ingots.

[0029] b. After heating the ingot, place it in an extruder and extrude it into a thick plate shape through a die; c. Obtain solder strips of specified thickness and width through rolling, and then wind them into coils after surface cleaning for later use. Here, the thickness of the upper and lower solder strips can be 4~10mm, and the width can be 30~100mm.

[0030] (2) Production of functional brazing solder strip (center brazing solder strip) a. Place the prepared raw materials with basic functional components in a smelting furnace for smelting and then cast them into ingots.

[0031] b. After heating the ingot, place it in an extruder and extrude it into a thick plate shape through a die; c. The solder strip of specified thickness and width is obtained through rolling, and after surface cleaning, it is wound into coils for later use. Here, the thickness of the middle solder strip can be 1~8mm, and the width can be 30~100mm. The widths of the upper and lower solder strips and the middle solder strip are the same to achieve a synchronous electrode composite solder strip; the thickness of the middle solder strip is generally not greater than the thickness of the upper and lower solder strips to prevent the upper and lower solder strips from being too thin, which could cause slippage when the upper and lower rollers apply pressure.

[0032] (3) Preparation of composite welding strip a. Place two conventional brazing solder strips on the two outer unwinding rollers, and place one or more functional brazing solder strips on the corresponding middle unwinding rollers; b. After the surfaces of the upper and lower brazing strips to be laminated are roughened by laser, they enter between two electrode rollers. The two electrode rollers shrink towards the middle, pressing the three layers of brazing strips together. The current and pressure between the electrodes are controlled by a computer system. c. According to Ampere's law, the resistance increases due to the gap between the middle solder strip and the upper and lower solder strips. According to Q=I... 2 RT, the heat generation increases, and the interface composite area will heat up and melt; d. Due to the pressure between the two roller electrodes, the middle brazing strip and the upper and lower brazing strips undergo metallurgical bonding and are welded together to form a composite brazing strip.

[0033] e. The overall resistance heating device is placed in a protective gas chamber, which can effectively prevent the surface of the solder from oxidizing during the heating process, thus affecting the composite effect. The protective gas can be an inert gas or a reducing gas.

[0034] (4) Cutting of composite welding strip a. The composite welding strip is cut and rolled, and different blades are used to roll it into composite welding rods of the corresponding width according to the required width; b. Composite welding electrodes can be packaged and shipped after deburring and quality inspection.

[0035] The implementation process of the present invention will be described in detail below with reference to specific embodiments. In the following embodiments, the width of the upper and lower solder strips and the middle solder strip are all 100mm.

[0036] I. Specific embodiments of the brazing filler metal preparation method of the present invention are as follows: Example 1 The method for preparing the solder in this embodiment includes the following steps: (1) Production of conventional brazing wire a. The raw materials with the prepared basic components are placed in a smelting furnace for smelting and then cast into ingots.

[0037] b. After heating the ingot, it is placed in an extruder and extruded into a thick plate shape through a special mold.

[0038] c. Obtain BAg35Cu32Zn33 welding strip with a thickness of 4.2mm by rolling, and then wind it into coils for later use after surface cleaning.

[0039] In other implementation scenarios, other conventional silver-based solders may also be selected, such as BAg50Cu30Zn20 as the conventional solder strip.

[0040] (2) Production of functional solder strips a. Place the prepared raw materials with basic functional components in a smelting furnace for smelting and then cast them into ingots.

[0041] b. After heating the ingot, it is placed in an extruder and extruded into a thick plate shape through a special mold.

[0042] c. Obtain CuSn welding strips with a specified thickness of 1.6 mm by rolling (Cu90Sn10, i.e., Sn mass content of 10%, balance of Cu), and wind them into coils for later use after surface cleaning.

[0043] (3) Preparation of composite welding strip a. Place two conventional brazing filler metal strips (BAgCuZn) on the two unwinding rollers and place one CuSn functional brazing filler metal strip (as the middle brazing filler metal strip) on the unwinding roller.

[0044] b. Before entering the electrode rollers, the surfaces of the upper and lower solder strips to be composited are laser-roughened. Laser roughening removes impurities from the solder strip surface and provides favorable conditions for resistive contact between the upper and lower solder strips. The surface roughness Ra should be controlled to ≤1μm. The upper and lower solder strips, and the middle solder strip, are sequentially combined and enter between the two electrode rollers in the gas-protected box. The two electrode rollers contract towards the center, pressing the three layers of solder strips together. The system is controlled by a computer system: electrode voltage 380V, current 2A, pressure between electrodes 2kN, contact area between electrode rollers and solder strips 2mm*100mm, and solder strip pressure 10MPa.

[0045] c. According to Ampere's law, the resistance increases due to the gap between the middle solder strip and the upper and lower solder strips. According to Q=I... 2 RT, the heat generation increases, and the interface composite area will heat up and melt.

[0046] d. Due to the pressure between the two roller electrodes, the middle brazing strip and the upper and lower brazing strips undergo metallurgical bonding and are welded together to form a composite brazing strip.

[0047] e. The overall resistance heating device is placed in a protective gas chamber, which can effectively prevent the surface of the solder from oxidizing during the heating process, thus affecting the composite effect. The protective gas can be an inert gas or a reducing gas.

[0048] (4) Cutting of composite welding strip a. The composite welding strip is cut and rolled, and different blades are used to roll it into composite welding rods of the corresponding width according to the required width.

[0049] b. Composite welding electrodes can be packaged and shipped after deburring and quality inspection.

[0050] Based on Example 1, in order to increase the composite efficiency and the uniformity of melting of the finished composite brazing filler metal during use, multiple central brazing filler metal strips can be used, with each central brazing filler metal strip stacked on top of the other. The composition of each central brazing filler metal strip can be the same or different. For example, it can be a pure metal such as silver or copper, or it can be an alloy.

[0051] Example 2 The differences between the brazing filler metal preparation method in this embodiment and that in Embodiment 1 are explained as follows: (1) Production of conventional brazing wire A BAgCuZn welding strip with a thickness of 6mm was obtained by rolling (BAg35Cu32Zn33), and after surface cleaning, it was wound into a roll for later use.

[0052] (2) Production of functional solder strips CuNi welding strips with a thickness of 5mm (Cu90Ni10, i.e., Ni mass content of 10% and the balance of Cu) are obtained by rolling and then wound into coils for later use after surface cleaning.

[0053] (3) Preparation of composite welding strip Controlled by a computer system: electrode voltage is 380V, current is 3A, pressure between electrodes is 4kN, and welding strip pressure is 20MPa.

[0054] Example 3 The differences between the brazing filler metal preparation method in this embodiment and that in Embodiment 1 are explained as follows: (1) Production of conventional brazing wire BAg95Cu welding strips with a thickness of 6mm are obtained by rolling, and after surface cleaning, they are wound into coils for later use.

[0055] (2) Production of functional solder strips Pure copper strips with a thickness of 4mm are obtained by rolling, and after surface cleaning, they are wound into coils for later use.

[0056] (3) Preparation of composite welding strip Controlled by a computer system: the electrode voltage is 380V, the current is 2.7A, the pressure between the electrodes is 5kN, and the welding strip is subjected to a pressure of 25MPa.

[0057] Example 4 The differences between the brazing filler metal preparation method in this embodiment and that in Embodiment 1 are explained as follows: (1) Production of conventional brazing wire A BAgCuZn welding strip with a thickness of 6mm was obtained by rolling (BAg35Cu32Zn33), and after surface cleaning, it was wound into a roll for later use.

[0058] (2) Production of functional solder strips CuSn welding strips with a thickness of 5 mm are obtained by rolling, and after surface cleaning, they are wound into coils for later use.

[0059] (3) Preparation of composite welding strip a. Place two conventional brazing filler metal strips (BAgCuZn) on two unwinding rollers, and place one CuSn functional brazing filler metal strip on the unwinding roller.

[0060] b. At the included angle at the front end of the three-layer welding strip entering the roller, Cu5Sn95 alloy powder (i.e., Sn mass content 95%, balance Cu) is sprayed onto the two contact surfaces at a constant flow and speed through the spray nozzle. The thickness of the added Cu5Sn95 alloy powder is not greater than 0.1mm, which can reduce the welding current and increase the welding speed to a certain extent. Moreover, the added Sn can also lower the melting point of the brazing filler metal and improve the wetting performance.

[0061] c. The two electrode rollers retract towards the middle, pressing the three layers of solder strip together. The system is controlled by a computer system: electrode voltage 380V, current 1.7A, pressure between electrodes 3 kN, and solder strip pressure 15MPa.

[0062] d. According to Ampere's law, due to the gap between the middle solder strip and the upper and lower solder strips, and the presence of alloy powder, the resistance is relatively high. Therefore, according to Q=I... 2 RT (Rapid Heat Generation) increases the heat generated, and the alloy powder, with its low melting point, will rapidly heat up and melt.

[0063] e. Due to the pressure between the two roller electrodes, the middle brazing filler strip, CuSn alloy powder and outer brazing filler strip undergo metallurgical bonding and are welded together to form a composite brazing strip.

[0064] The composition of the composite solder product prepared in this way is shown in Table 1 below.

[0065] Table 1. Composition Description of Composite Brazing Alloys II. Experimental Examples Experimental Example 1 The interfacial bonding of the functional composite solders obtained in Examples 1 and 2 was observed, and the results are as follows: Figure 2 and Figure 3 As shown in the figure, the three layers of the functional composite brazing filler metal obtained in the embodiment are tightly bonded, exhibiting a typical metallurgical bonding state.

[0066] Experimental Example 2 Based on Example 3, the pressure on the welding strip was adjusted to 10MPa, 15MPa and 20MPa respectively, and the interlayer tensile strength of the composite welding strip under different pressures was investigated (GB / T 228-2002 Metallic Materials Tensile Test Method at Room Temperature). The results are shown in Table 2.

[0067] Table 2 Interlayer tensile strength of composite welded strips under different pressures As shown in Table 2, the interlayer tensile strength of the composite welding strip produced using the method of this invention reaches 104~173 MPa, demonstrating good interlayer bonding. Furthermore, due to the adoption of a sandwich-like structure, the overall integrity of the material is significantly improved, which also helps to enhance the uniformity of melting during the use of the welding strip.

[0068] Example 3 Based on Example 4, with other conditions kept constant, the current and welding speed required for the welding process of the composite brazing filler metal without the addition of alloy powder were compared, and the results are shown in Table 3.

[0069] Table 3. Comparison of composite effects of technical solutions with and without alloy powder. As shown in Table 3, after adding alloy powder, the surface roughness between the upper and lower solder strips and the middle layer increased, the required current decreased from 1.9A to 1.7A, and the welding speed decreased from 2s to 1.5s, which improved the welding rate of the composite brazing filler metal. Moreover, the interfacial bonding effect of the composite solder strip was better than that without adding alloy powder.

Claims

1. A method for preparing a solder, characterized in that, Includes the following steps: An upper brazing strip, at least one middle brazing strip, and a lower brazing strip enter between two vertically arranged electrode rollers and are welded together under the action of the electrode rollers. The composite interface of two adjacent brazing strips melts under the action of resistance heat and forms a metallurgical bond under the pressure of the electrode rollers. The composition of at least one of the middle brazing strips is different from that of the upper and lower brazing strips. The upper brazing strip, at least one middle brazing strip, and the lower brazing strip are fused together into a whole alloy brazing strip during brazing. The upper and lower brazing strips are silver-based or copper-based brazing strips, and the middle brazing strip is pure copper strip, pure silver strip, or copper alloy strip. The alloying elements in the copper alloy strip are selected from one or more combinations of Sn, Ni, Co, Mn, Zn, and Ag. Before entering the electrode roller, a low melting point metal powder with a melting point not higher than 450°C is added to the composite interface of the upper, lower and middle brazing strips. The low melting point metal powder is one or a combination of two or more of Sn powder, SnAg alloy powder and CuSn alloy powder.

2. The method for preparing the solder as described in claim 1, characterized in that, The upper and lower brazing strips are both BAg35Cu32Zn33 or BAg50Cu30Zn20, and the middle brazing strip is Cu90Sn10.

3. The method for preparing the solder as described in claim 1, characterized in that, The upper and lower brazing strips are both BAg35Cu32Zn33, and the middle brazing strip is Cu90Ni10.

4. The method for preparing the solder as described in claim 1, characterized in that, The upper and lower solder strips are both BAg35Cu32Zn33 and both are BAg95Cu, while the middle solder strip is pure copper.

5. The method for preparing the solder as described in claim 1, characterized in that, The thickness of the added low-melting-point metal powder is no more than 0.1 mm.

6. The method for preparing the brazing filler metal as described in claim 4, characterized in that, The Sn content in the SnAg alloy powder and CuSn alloy powder is above 90%.

7. The method for preparing the solder as described in claim 1, characterized in that, Before entering the electrode roller, the surface to be laminated in the middle of the brazing strip or the surface to be laminated in the upper and lower brazing strips is laser roughened.

8. The method for preparing the solder as described in claim 7, characterized in that, The laser texturing process controls the surface roughness Ra to be ≤1μm.

9. The method for preparing the solder as described in claim 1, characterized in that, The electrode rollers are subjected to a voltage of 220~380V, a current of 1~3A, and a pressure of 10~25MPa.

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