A method for preparing a low-cavitation preform and the low-cavitation preform

Abstract

This invention provides a method for preparing a low-cavitation-rate preformed solder sheet, comprising a core layer and a shell layer disposed around the core layer. By embedding the solid flux core layer within the solder alloy layer to form a sandwich-like shape, the flux can be effectively protected from oxidation. This eliminates the need for applying flux before brazing and removing flux after brazing, reducing manufacturing costs and the cavitation rate of the welded surface, thus improving the reliability of the solder sheet. Adding small amounts of iridium and rhodium increases the strength, hardness, and heat resistance of the tin alloy, increases the melting point of the solder sheet shell, and improves the overall mechanical strength of the solder sheet. Adding a small amount of tellurium improves the electrical and thermal conductivity of the solder sheet. Combined with silver and copper, a dense hexagonal lattice network structure is formed, facilitating flux penetration within the solder sheet shell and reducing the cavitation rate of the solder joint. Furthermore, the synergistic effect of rhodium and iridium provides good thermal and electrical conductivity and ductility, enhancing the storage stability of the solder sheet and improving the strength, hardness, and heat resistance of the alloy.

Description

[0001] This application is a divisional application. The original application has the application number 2022103395712 and the application date is April 1, 2022. The invention patent title is: A preformed welding sheet and its preparation method. Technical Field

[0002] This invention relates to the field of welding materials technology, specifically to a method for preparing a low-cavitation preformed welding sheet and the low-cavitation preformed welding sheet itself. Background Technology

[0003] Currently, the brazing methods used in heat exchangers or machinery mostly employ flux brazing, where flux is applied to the surfaces of the parts to be joined. Flux brazing requires both applying flux before brazing and removing the flux or its residue afterward, increasing the manufacturing cost of aluminum products. Furthermore, if the flux or its residue is not adequately removed after brazing, subsequent surface treatments may result in a deterioration of the surface quality.

[0004] Currently, most solder pads on the market are either bare solder pads or solder pads with flux coated on the surface. However, when a layer of flux is coated on the surface of the solder pad, the flux film is thin and easily becomes fragile or oxidized, resulting in the components in the flux not being utilized effectively.

[0005] Therefore, there is an urgent need for a preformed solder sheet and its preparation method that reduces the void rate of the welded surface after welding, improves heat dissipation and reliability, and does not apply flux to the surface of the joint, but uses flux as a solid core layer covering the solder sheet. Summary of the Invention

[0006] To address the technical problem of reducing the void ratio of the welded surface after welding and improving heat dissipation and reliability, this invention provides a preformed welding sheet.

[0007] The second objective of this invention is to provide a method for preparing a preformed solder sheet.

[0008] To achieve the first objective mentioned above, the technical solution adopted by the present invention is as follows:

[0009] A preformed solder sheet includes a core layer and a shell layer disposed around the core layer. By embedding the solid flux core layer in the solder alloy layer to form a sandwich shape, the flux can be well protected from oxidation. There is no need to apply flux before brazing or remove flux after brazing, which reduces manufacturing costs and the void rate of the welded surface after welding, and improves the reliability of the solder sheet.

[0010] The core layer is a flux comprising the following components: 65.4-72.6 wt% rosin, 10.4-14.8 wt% activator, 5.2-8.6 wt% surfactant, 5.3-6.1 wt% thixotropic agent, and 3.4-5.2 wt% antioxidant. The surfactant is a compound of 48-56 wt% unsaturated fatty amide and 44-52 wt% sodium dodecyl sulfate. By using a halogen-free activator, the corrosivity of the solder sheet to the substrate is reduced, and post-weld residue is minimized. The addition of the surfactant compounded with unsaturated fatty amide and sodium dodecyl sulfate gives the rosin high anti-blocking and penetrating properties, allowing the flux to penetrate the solder surface during brazing, thereby improving the stability and reliability of the solder sheet performance.

[0011] The shell layer is a solder alloy comprising the following components: 92.5-96.5 wt% tin, 1.2-2.3 wt% silver, 0.2-0.9 wt% copper, 0.12-0.61 wt% tellurium, 0.5-0.8 wt% rhodium, 0.09-0.2 wt% iridium, and 1.1-2.8 wt% palladium. The addition of small amounts of iridium and rhodium increases the strength, hardness, and heat resistance of the tin alloy, increases the melting point of the solder sheet shell, and improves the overall mechanical strength of the solder sheet. The addition of a small amount of tellurium improves the electrical and thermal conductivity of the solder sheet. Together with silver and copper, it forms a dense hexagonal lattice network structure, which facilitates the penetration of flux into the solder sheet shell and reduces the void rate of the solder joint.

[0012] As described above, the unsaturated fatty amide includes one or more of oleamide and erucamide. By adding oleamide, the friction during mixing of the flux system is reduced, and the penetration performance of the system is enhanced.

[0013] In the preformed solder sheet described above, the activator is one or more combinations of succinic acid, glutaric acid, pimelic acid, and malic acid.

[0014] As described above, the thixotropic agent is a combination of hydroquinone, dodecyl stearic acid and modified hydrogenated castor oil. By using multiple thixotropic agents in combination, the solder sheet is prevented from collapsing, thus preventing phenomena such as tailing, adhesion and collapse during brazing.

[0015] As described above, the rosin in the preformed solder sheet is a compound of hydrogenated rosin and disproportionated rosin. By compounding hydrogenated rosin and disproportionated rosin, the spread rate of the solder sheet on the substrate can be improved, giving the solder sheet better wetting properties, full solder joints, bright surface, and better forming effect.

[0016] In the preformed solder sheet described above, the ratio of disproportionated rosin to hydrogenated rosin is 3-4:6-7.

[0017] As described above, the antioxidant in the preformed solder sheet is one or more combinations of ethoxyquinoline, 2-ethyl ether azole, and methylbenzotriazole, which can improve the antioxidant properties of the solder sheet, inhibit the oxidation of tin, and help reduce the occurrence of the pillow effect.

[0018] As described above, the preformed welding sheet has an overall shape that is square, circular, arc-shaped, ring-shaped, frame-shaped, or strip-shaped.

[0019] As described above, the core layer thickness of the preformed solder sheet is 50-70 μm, and the shell layer thickness is 0.3-0.8 mm.

[0020] To achieve the second objective mentioned above, the technical solution adopted by the present invention is as follows:

[0021] The method for preparing the preformed solder sheet as described in any of the preceding methods includes the following steps:

[0022] S1. Weigh the above alloy components according to the stated weight percentages and smelt them.

[0023] S2. Cool the molten solution and die-cast it in a mold to obtain a solder shell for later use;

[0024] S3. Add rosin to a container and heat to 120-140℃. After it dissolves, add the surfactant and stir until completely dissolved.

[0025] S4. Keep the temperature at 120-140℃, add the thixotropic agent and stir until completely dissolved;

[0026] S5. Reduce the temperature to 60-80℃, add antioxidants and activators, stir for 40-60 minutes to obtain liquid flux;

[0027] S6. Cool the liquid flux to room temperature, roll it into shape, and obtain solid flux;

[0028] S7. Embed the solid flux into the solder shell and stamp it to obtain the final product.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] 1. This invention provides a preformed solder sheet, comprising a core layer and a shell layer disposed around the core layer. By embedding the solid flux core layer within the solder alloy layer to form a sandwich-like shape, the flux can be effectively protected from oxidation. There is no need to apply flux before brazing or remove it after brazing, reducing manufacturing costs and the void rate on the welded surface, thus improving the reliability of the solder sheet. The solder alloy shell is composed of tin, silver, copper, tellurium, rhodium, palladium, and iridium. Adding small amounts of iridium and rhodium increases the strength, hardness, and heat resistance of the tin alloy, increases the melting point of the solder sheet shell, and improves the overall mechanical strength of the solder sheet. Adding a small amount of tellurium improves the electrical and thermal conductivity of the solder sheet. Combined with silver and copper, a dense hexagonal lattice network structure is formed, facilitating flux penetration within the shell and reducing the void rate of the solder joint. Furthermore, the combination of rhodium and iridium provides good thermal and electrical conductivity and ductility, improving the storage stability of the solder sheet and enhancing the strength, hardness, and heat resistance of the alloy.

[0031] 2. The flux selected in this application is used as the core layer. By using a halogen-free activator, the corrosion of the solder sheet to the substrate is reduced, and the residue after welding is reduced. By adding a surfactant compounded with unsaturated fatty amide and sodium dodecyl sulfonate, the rosin has high anti-adhesion and penetration properties. During brazing, the flux can penetrate into the surface of the solder to improve the stability and reliability of the solder sheet performance.

[0032] 3. The present invention provides a method for preparing a preformed solder sheet, which involves preparing a flux core layer and a solder alloy shell in sequence, and then embedding the flux core layer into the alloy shell. The process is simple, the reaction is mild, and no harmful gases are generated during the process, making it suitable for mass production. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0034] Figure 1 This is a cross-sectional view of a preformed welding sheet according to this application. Detailed Implementation

[0035] The technical solution of the present invention will be described below with reference to Examples 1-5.

[0036] Example 1

[0037] A preformed solder pad includes a solder alloy shell layer 2 and a flux core layer 1, wherein the composition of the solder alloy layer 2 is shown in Table 1, and the composition of the flux is shown in Table 2. Its preparation method includes the following steps:

[0038] Weigh each component according to the weight percentages in Tables 1 and 2, and set aside. Melt the solder alloy in Table 1; cool the molten solution and die-cast it in a mold to obtain the solder shell, and set aside.

[0039] Add rosin to a container according to Table 2, heat to 120°C, and after it dissolves, add surfactant and stir until completely dissolved; keep the temperature at 120°C, add thixotropic agent and stir until completely dissolved; lower the temperature to 60°C, add antioxidant and activator, and stir for 40 minutes to obtain liquid flux; cool the liquid flux to room temperature, roll it into shape to obtain solid flux; embed the solid flux into the solder shell and stamp it to obtain the final product.

[0040] Example 2

[0041] A preformed solder pad includes a solder alloy shell layer 2 and a flux core layer 1, wherein the composition of the solder alloy layer 2 is shown in Table 1, and the composition of the flux is shown in Table 2. Its preparation method includes the following steps:

[0042] Weigh each component according to the weight percentages in Tables 1 and 2, and set aside. Melt the solder alloy in Table 1; cool the molten solution and die-cast it in a mold to obtain the solder shell, and set aside.

[0043] Add rosin to a container according to Table 2, heat to 130°C, and after it dissolves, add surfactant and stir until completely dissolved; keep the temperature at 130°C, add thixotropic agent and stir until completely dissolved; lower the temperature to 70°C, add antioxidant and activator, and stir for 50 minutes to obtain liquid flux; cool the liquid flux to room temperature, roll it into shape to obtain solid flux; embed the solid flux into the solder shell and stamp it to obtain the final product.

[0044] Example 3

[0045] A preformed solder pad includes a solder alloy shell layer 2 and a flux core layer 1, wherein the composition of the solder alloy layer 2 is shown in Table 1, and the composition of the flux is shown in Table 2. Its preparation method includes the following steps:

[0046] Weigh each component according to the weight percentages in Tables 1 and 2, and set aside. Melt the solder alloy in Table 1; cool the molten solution and die-cast it in a mold to obtain the solder shell, and set aside.

[0047] Add rosin to a container according to Table 2, heat to 140°C, and after it dissolves, add a surfactant and stir until completely dissolved; keep the temperature at 140°C, add a thixotropic agent and stir until completely dissolved; lower the temperature to 80°C, add an antioxidant and an activator, and stir for 60 minutes to obtain a liquid flux; cool the liquid flux to room temperature, roll it into shape, and obtain a solid flux; embed the solid flux into a solder shell and stamp it to obtain the final product.

[0048] Example 4

[0049] A preformed solder pad includes a solder alloy shell layer 2 and a flux core layer 1, wherein the composition of the solder alloy layer 2 is shown in Table 1, and the composition of the flux is shown in Table 2. Its preparation method includes the following steps:

[0050] Weigh each component according to the weight percentages in Tables 1 and 2, and set aside. Melt the solder alloy in Table 1; cool the molten solution and die-cast it in a mold to obtain the solder shell, and set aside.

[0051] Add rosin to a container according to Table 2, heat to 140°C, and after it dissolves, add a surfactant and stir until completely dissolved; keep the temperature at 140°C, add a thixotropic agent and stir until completely dissolved; lower the temperature to 80°C, add an antioxidant and an activator, and stir for 60 minutes to obtain a liquid flux; cool the liquid flux to room temperature, roll it into shape, and obtain a solid flux; embed the solid flux into a solder shell and stamp it to obtain the final product.

[0052] Example 5

[0053] A preformed solder pad includes a solder alloy shell layer 2 and a flux core layer 1, wherein the composition of the solder alloy layer 2 is shown in Table 1, and the composition of the flux is shown in Table 2. Its preparation method includes the following steps:

[0054] Weigh each component according to the weight percentages in Tables 1 and 2, and set aside. Melt the solder alloy in Table 1; cool the molten solution and die-cast it in a mold to obtain the solder shell, and set aside.

[0055] Add rosin to a container according to Table 2, heat to 140°C, and after it dissolves, add a surfactant and stir until completely dissolved; keep the temperature at 140°C, add a thixotropic agent and stir until completely dissolved; lower the temperature to 80°C, add an antioxidant and an activator, and stir for 60 minutes to obtain a liquid flux; cool the liquid flux to room temperature, roll it into shape, and obtain a solid flux; embed the solid flux into a solder shell and stamp it to obtain the final product.

[0056] Table 1: Component weight ratio of solder alloy powder in Examples 1-5

[0057]

[0058]

[0059] Table 2: Component weight ratio of fluxes in Examples 1-5

[0060]

[0061] The preformed weld sheets obtained in Examples 1-5 were subjected to performance tests, and the test results are shown in Table 3.

[0062] Table 3: Test Results of Examples 1-5 and Comparative Examples

[0063]

[0064] As can be seen from the table, this invention provides a pre-formed solder sheet. By embedding a solid flux core layer within the solder alloy layer to form a sandwich-like shape, it effectively protects the flux from oxidation. This eliminates the need for pre-brazing flux application and post-brazing flux removal, reducing manufacturing costs and the voiding rate of the welded surface, thus improving the reliability of the solder sheet. The solder alloy shell is composed of tin, silver, copper, tellurium, rhodium, palladium, and iridium. Adding small amounts of iridium and rhodium increases the strength, hardness, and heat resistance of the tin alloy, increases the melting point of the solder sheet shell, and improves the overall mechanical strength of the solder sheet. Adding a small amount of tellurium improves the electrical and thermal conductivity of the solder sheet. Combined with silver and copper, it forms a dense hexagonal lattice network structure, facilitating flux penetration within the solder sheet shell and reducing the voiding rate of the solder joint. Furthermore, the synergistic effect of rhodium and iridium provides good thermal and electrical conductivity and ductility, enhancing the storage stability of the solder sheet and improving the strength, hardness, and heat resistance of the alloy.

[0065] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for producing a preform soldering piece with low void ratio, characterized in that, It comprises the following steps: S1, take the solder alloy components by weight percentage, melt; S2, the molten solution is cooled, pressure casting in the mold, get solder shell, for future use; S3, add rosin to the container, heated to 120-140℃, after dissolving, add surfactant, stirring to completely dissolved; S4, keep the temperature at 120-140℃, add thixotropic agent stirring until completely dissolved; S5, the temperature is reduced to 60-80℃, add antioxidant, activator, stirring 40-60min, get liquid flux; S6, the liquid flux is cooled to room temperature, roll forming, get solid flux; S7, the solid flux is embedded in the solder shell, stamping, get it; The solder alloy is composed of 92.5-96.5wt% of tin, 1.2-2.3wt% of silver, 0.2-0.9wt% of copper, 0.12-0.61wt% of tellurium, 0.5-0.8wt% of rhodium, 0.09-0.2wt% of iridium and 1.1-2.8wt% of palladium; The solid flux has the following component weight ratio: 65.4-72.6wt% of rosin, 10.4-14.8wt% of activator, 5.2-8.6wt% of surfactant, 5.3-6.1wt% of thixotropic agent and 3.4-5.2wt% of antioxidant; the surfactant is composed of 48-56wt% of unsaturated fatty amide and 44-52wt% of sodium dodecyl sulfonate; the unsaturated fatty amide includes one or more of oleic acid amide and erucic acid amide; In step S3, the rosin is a combination of hydrogenated rosin and disproportionated rosin; the ratio of the disproportionated rosin to the hydrogenated rosin is 3-4:6-7; In step S4, the thixotropic agent is a combination of hydroquinone, dodecyl hydroxystearic acid and modified hydrogenated castor oil; In step S5, the activator is one or more of succinic acid, glutaric acid, heptanedioic acid and malic acid.

2. The method of claim 1, wherein: In step S5, the antioxidant is one or more of ethoxyquinoline, 2-ethyl etherazole and methyl benzotriazole.

3. The low void fraction preform solder of claim 1 or 2, wherein: It comprises a core layer (1) and a shell layer (2) arranged on the side of the core layer (1); The core layer (1) is the solid flux, and the shell layer (2) is the solder alloy.

4. The low void fraction preform of claim 3, wherein: The overall shape of the preform solder piece is square, circular, arc, ring, frame or strip; the thickness of the core layer (1) is 50-70μm, and the thickness of the shell layer (2) is 0.3-0.8mm.

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