Tinned copper wire and preparation method thereof

Abstract

The invention relates to the technical field of alloy-plated copper wire production, and provides a tin-plated copper wire and a preparation method thereof.The tin-plated copper wire comprises a copper core and a tin alloy plating layer, and the tin alloy plating layer comprises the following components: 0.02-0.05 wt% of La, 0.01-0.05 wt% of Cu, 0.01-0.05 wt% of Ti, 0.01- 0.01 wt% to 0.03 wt% of P; 0.10 to 0.30 wt% of Cu; and the balance of Sn. 0.01-0.03 wt% of P can achieve a very good deoxidation effect, so that the oxygen content of the prepared tin alloy coating is reduced, oxide inclusion is reduced, 0.10-0.30 wt% of Cu and Sn form a solid solution, coating grains are refined together with 0.02-0.05 wt% of La, La can inhibit diffusion of copper and tin atoms at high temperature, generation of brittle intermetallic compounds such as Cu3Sn and Cu6Sn5 is reduced, a copper matrix is purified, element enrichment and internal defects are reduced, and the service life of the coating is prolonged. And the interface bonding force between the plating layer and the copper core is enhanced, and the cracking and falling probability of the plating layer is reduced. And La can optimize the microstructure of the plating layer, reduce pores and defects, improve the compactness of the plating layer and further enhance the corrosion resistance, so that the tinned copper wire prepared from the tin alloy plating layer on the copper core can stably adapt to a high-temperature packaging scene of electronic equipment.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of alloy copper wire production, and particularly relates to a tin-plated copper wire and a preparation method thereof. BACKGROUND

[0002] The tin-plated copper wire is a core basic material in the electronic industry and is widely used in lead wires of electronic components and jumper wires of circuit boards. With the rapid development of electronic devices towards miniaturization and high integration, the electronic packaging technology is gradually upgraded to an automated and high-efficiency mode, and the packaging temperature is significantly improved. Therefore, the performance requirements for the tin-plated copper wire are increasingly stringent, and in particular, the tin-plated copper wire needs to maintain good solderability and surface gloss after being placed at a high temperature for a long time.

[0003] In the related art, the pure tin-plated copper wire is prone to serious surface oxidation and the generation of a loose oxide film at a high temperature of 200 DEG C or above, which leads to a rapid decline in solderability. Meanwhile, the atomic diffusion between the copper core and the plating layer is accelerated at a high temperature, brittle intermetallic compounds are generated, the adhesion between the plating layer and the copper core is weakened, and the plating layer is cracked and peeled off, which seriously affects the conductivity and corrosion resistance and is difficult to meet the demand of the electronic industry for high-performance tin-plated copper wires. SUMMARY

[0004] The application aims to provide a tin-plated copper wire and a preparation method thereof, which can improve the problem that the performance of the tin-plated copper wire is prone to decline at a high temperature.

[0005] To achieve the above-mentioned application purposes, the technical solutions adopted by the application are as follows: In a first aspect, the application provides a tin-plated copper wire, which comprises a copper core and a tin alloy plating layer, and the tin alloy plating layer comprises the following components: La, 0.02-0.05wt%; P, 0.01-0.03wt%; Cu, 0.10-0.30wt%; the rest is Sn.

[0006] The tinned copper wire provided in the application can achieve good deoxidation effect by 0.01-0.03wt% P, so that the oxygen content of the tin alloy plating layer prepared is reduced, and the oxide inclusions are reduced, 0.10-0.30wt% Cu forms a solid solution with Sn, and together with 0.02-0.05wt% La, the plating layer grains are refined, and La can inhibit the diffusion of copper and tin atoms at high temperature, reduce the generation of brittle intermetallic compounds such as Cu3Sn and Cu6Sn5, purify the copper matrix, reduce element enrichment and internal defects, enhance the interface bonding force of the plating layer and the copper core, and reduce the probability of plating layer cracking and falling off. And La can optimize the microstructure of the plating layer, reduce pores and defects, improve the density of the plating layer, and thus enhance the corrosion resistance, reduce the performance short board caused by local thinning, so that the tinned copper wire prepared by the tin alloy plating layer on the copper core can be stably adapted to the high-temperature packaging scene of electronic equipment.

[0007] In some embodiments, the diameter of the copper core is 0.8-1.2mm, and the thickness of the tin alloy plating layer is 9-10μm.

[0008] In some embodiments, the copper core is an oxygen-free red copper core with a copper content of ≥99.99%.

[0009] In a second aspect, the application provides a tinned copper wire preparation method, which comprises: providing the components of the tin alloy plating layer and the copper core in any one of the first aspect, melting the components of the tin alloy plating layer to obtain a tin alloy melt; cleaning and drying the copper core to obtain a pretreated copper core; immersing the pretreated copper core in the tin alloy melt and taking it out to obtain a semi-finished tinned copper wire; sequentially polishing, cleaning and drying the semi-finished tinned copper wire to obtain a tinned copper wire.

[0010] The tinned copper wire preparation method provided in the application melts the components of the tin alloy plating layer to obtain a tin alloy melt, cleans and dries the copper core to remove the oil stains and oxide layers on the surface of the copper core, obtains a pretreated copper core, then immerses the pretreated copper core in the tin alloy melt and takes it out to make the plating layer uniformly adhere to the surface of the copper core, obtains a semi-finished tinned copper wire, and finally sequentially polishes, cleans and dries the semi-finished tinned copper wire to obtain a tinned copper wire. This process tightly combines the tin alloy and the copper core in a hot-dip plating manner, fully utilizes the high-temperature oxidation resistance, strong plating layer bonding force, stable soldering performance, excellent corrosion resistance and good electrical conductivity brought by the components, and meets the batch production and high-quality requirements of the electronic equipment high-temperature packaging scene.

[0011] In some embodiments, the melting of the components of the tin alloy plating layer to obtain a tin alloy melt comprises: heating and melting Sn to obtain a tin melt; adding La, P and Cu into the tin melt to obtain a tin alloy melt.

[0012] In some embodiments, in the heating and melting Sn to obtain a tin melt, the melting temperature is 250°C.

[0013] In some embodiments, the cleaning and drying treatment of the copper core to obtain a pretreated copper core comprises: immersing the copper core in a 5-8% alkaline solution to obtain a first copper core; immersing the first copper core in an 8-12% acidic solution to obtain a second copper core; wherein the immersion time is 4-6 min; water washing the second copper core to obtain a third copper core; drying the third copper core to obtain a pretreated copper core.

[0014] In some embodiments, in the immersing the copper core in a 5-8% alkaline solution to obtain a first copper core, the immersion temperature is 55-65°C, and the immersion time is 9-11 min.

[0015] In some embodiments, in the drying the third copper core to obtain a pretreated copper core, the drying temperature is 110-125°C, and the drying time is 18-25 min.

[0016] In some embodiments, the taking out the pretreated copper core after being immersed in the tin alloy melt to obtain a semi-finished tinned copper wire comprises: immersing the pretreated copper core vertically in the tin alloy melt at a speed of 0.5 m / min for 3 s to obtain a tin-liquid-attached copper wire; blowing off the excess tin liquid on the tin-liquid-attached copper wire to obtain a semi-finished tinned copper wire; wherein the air pressure for blowing off is 0.3 MPa.

[0017] In some embodiments, in the polishing, cleaning and drying of the semi-finished tinned copper wire in sequence to obtain a tinned copper wire, the drying temperature is 100-105°C, and the drying time is 12-15 min.

[0018] The above description is only a summary of the technical solutions of the present application. In order to more clearly understand the technical means of the present application, the following specific embodiments of the present application can be implemented according to the content of the specification, and in order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the following specific embodiments of the present application are described. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0020] Figure 1 is a schematic flow chart of the preparation method of the tinned copper wire provided by the embodiments of the present application. DETAILED DESCRIPTION

[0021] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clear, the present application will be further described in detail in combination with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application, and are not used to limit the present application.

[0022] In the present application, the term "and / or" describes the association relationship of the associated objects, which means that there can be three kinds of relationships, for example, A and / or B can mean that A exists alone, A and B exist together, and B exists alone. Wherein A and B can be singular or plural. The character " / " generally represents an "or" relationship between the associated objects before and after it.

[0023] In the present application, "at least one" means one or more, and "multiple" means two or more. "At least one of the following" or similar expressions means any combination of these items, including any combination of single item or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can mean a, b, c, a-b (i.e. a and b), a-c, b-c, or a-b-c, wherein a, b, and c can be single or multiple.

[0024] It should be understood that in various embodiments of the present application, the size of the sequence number of the above processes does not mean the order of execution, and part or all of the steps can be executed in parallel or in sequence, and the execution order of each process should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0025] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0026] The weight of the related components mentioned in the embodiment specification of the present application can not only refer to the specific content of each component, but also represent the proportional relationship between the weights of each component. Therefore, as long as the content of the related components in the embodiment specification of the present application is scaled up or down in proportion, it is within the scope disclosed in the embodiment specification of the present application. Specifically, the mass mentioned in the embodiment specification of the present application can be µg, mg, g, kg, and other mass units commonly known in the chemical industry.

[0027] The terms "first", "second" are only for descriptive purposes, to distinguish objects such as substances from each other, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. For example, without departing from the scope of the present application, the first XX can also be referred to as the second XX, and similarly, the second XX can also be referred to as the first XX. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features.

[0028] In the related art, pure tin plated layer plated copper wire in the high temperature environment of 200℃ and above, easy to appear surface oxidation is serious, the generation of loose oxide film leads to the problem of rapid decline of soldering performance, at the same time, high temperature will accelerate the atomic diffusion between copper core and plating layer, generate brittle intermetallic compound, cause the adhesion between plating layer and copper core to weaken, lead to plating layer cracking, falling off, seriously affect the conductivity and corrosion resistance, difficult to meet the demand of electronic industry development for high performance tin plated copper wire.

[0029] Based on this, in order to improve the problem that the performance of the tin plated copper wire in the related art is prone to decline at high temperature, the embodiment of the present application provides the following scheme.

[0030] The first aspect of the embodiment of the present application provides a tin plated copper wire, which comprises a copper core and a tin alloy plating layer. The tin alloy plating layer comprises the following components: La 0.02~0.05wt%; P 0.01~0.03wt%; Cu 0.10~0.30wt%; and the rest is Sn.

[0031] It can be understood that La 0.02~0.05wt% means that when the total weight of the raw materials is 100, the lanthanum content is between 0.02 and 0.05, for example, it can be 0.02, 0.03, 0.05, etc., but is not limited to this. When the La content is less than 0.02wt%, a continuous and dense oxide film cannot be formed, and the effect on improving high-temperature oxidation resistance and brazing wettability is not significant; when the La content is greater than 0.05%, rare earth enriched phases are easily formed in the coating, leading to increased brittleness of the coating. P refers to phosphorus, and the phosphorus content is between 0.01 and 0.03, for example, it can be 0.01, 0.02, 0.03, etc., but is not limited to this. Gu refers to copper, and its content is between 0.10 and 0.30, for example, it can be 0.10, 0.20, 0.30, etc., but is not limited to this. The remainder being Sn means that after determining the contents of the above three elements La, P, and Cu, the remaining mass percentage is all tin.

[0032] As can be seen from the above, the 0.01~0.03wt% P in the tin-plated copper wire provided in this application embodiment can play a good deoxidation role, thereby reducing the oxygen content of the prepared tin alloy coating and reducing oxide inclusions. The 0.10~0.30wt% Cu and Sn form a solid solution, and together with the 0.02~0.05wt% La, they refine the coating grains. Furthermore, La can inhibit the diffusion of copper and tin atoms at high temperatures, reduce the formation of brittle intermetallic compounds such as Cu3Sn and Cu6Sn5, purify the copper matrix, reduce element enrichment and internal defects, enhance the interfacial bonding between the coating and the copper core, and reduce the probability of coating cracking and peeling. Moreover, La can optimize the microstructure of the coating, reduce porosity and defects, increase the coating density, thereby enhancing corrosion resistance and reducing performance shortcomings caused by local thinness. This allows the tin-plated copper wire made from the tin alloy coating on the copper core to be stably adapted to the high-temperature packaging scenarios of electronic devices.

[0033] In some embodiments, the diameter of the copper core is 0.8~1.2 mm, and the thickness of the tin alloy plating is 9~10 μm.

[0034] It is understood that the diameter of the copper core is 0.8~1.2mm, for example, 0.8mm, 1.0mm, 1.2mm, etc., but is not limited to this. The thickness of the tin alloy plating is 9~10μm, for example, 9μm, 9.5μm, 10μm, etc., but is not limited to this.

[0035] With this configuration, the diameter of the copper core is 0.8~1.2mm, which can balance the mechanical strength and conductivity of the copper wire and meet the requirements of miniaturization and high integration of electronic devices for lead wire thickness. The 9~10μm tin alloy plating thickness allows functional elements such as La, P, and Cu to play their full role and form a dense and uniform protective layer. This reduces the insufficient anti-oxidation and corrosion resistance caused by an excessively thin plating layer, and also reduces the impact of an excessively thick plating layer on the bending, welding and other processing properties of the copper wire.

[0036] In some embodiments, the copper core is an oxygen-free copper core with a copper content of ≥99.99%.

[0037] It can be understood that copper content ≥99.99% means that the total content of impurity elements (such as iron, zinc, lead, etc.) in the copper core does not exceed 0.01%. Oxygen-free copper core refers to copper material that avoids the participation of oxygen in the production process, reducing defects such as oxidation inclusions and porosity inside the copper core.

[0038] This configuration ensures that high-purity oxygen-free copper can maximize the conductivity of the copper wire, reduce resistivity, and meet the signal transmission efficiency requirements of electronic devices. At the same time, it reduces the negative impact of impurities on the adhesion of the plating layer, and reduces the possibility of gaps or abnormal reactions at the interface between the plating layer and the copper core caused by impurities. This provides a pure and stable substrate for the uniform adhesion and performance of the tin alloy plating, thereby improving the overall reliability of the product.

[0039] The second aspect of this application provides a method for preparing tin-plated copper wire. Please refer to [link to relevant documentation]. Figure 1 The methods for preparing tin-plated copper wire include: S100, providing the components of the tin alloy plating layer and the copper core as described in any of the above embodiments, and melting the components of the tin alloy plating layer to obtain a tin alloy melt.

[0040] S200 involves cleaning and drying the copper core to obtain a pretreated copper core.

[0041] S300 involves immersing the pretreated copper core in molten tin alloy and then removing it to obtain a semi-finished tin-plated copper wire.

[0042] S400 involves polishing, cleaning, and drying the semi-finished tin-plated copper wire in sequence to obtain tin-plated copper wire.

[0043] As described above, the method for preparing tin-plated copper wire provided in this application involves melting the components of the tin alloy plating to obtain a tin alloy melt. The copper core is then cleaned and dried to remove oil and oxide layers from its surface, resulting in a pre-treated copper core. This pre-treated copper core is then immersed in the tin alloy melt and removed, allowing the plating to adhere evenly to its surface, resulting in a semi-finished tin-plated copper wire. Finally, the semi-finished tin-plated copper wire is polished, cleaned, and dried sequentially to obtain the final tin-plated copper wire. This process uses hot-dip plating to tightly bond the tin alloy to the copper core, fully leveraging the synergistic effects of the components to achieve high-temperature oxidation resistance, strong plating adhesion, stable brazing performance, excellent corrosion resistance, and good conductivity. This method is suitable for the mass production and high-quality requirements of high-temperature packaging scenarios in electronic devices.

[0044] In some embodiments, in step S100, the components of the tin alloy plating are melted to obtain a tin alloy melt, including: S110 involves heating and melting Sn to obtain molten tin.

[0045] S120: La, P and Cu are added to molten tin and stirred to obtain molten tin alloy.

[0046] It is understandable that melting can be carried out using melting equipment such as medium-frequency induction melting furnaces and resistance heating melting crucibles, while mechanical stirrers (such as high-temperature resistant ceramic stirring paddles) or electromagnetic stirring systems are used to assist in mixing, so that the elements can be fully dissolved and evenly dispersed.

[0047] This setup involves first heating and melting Sn to provide a uniform and stable matrix melt for the subsequent addition of functional elements. Then, adding La, P, and Cu to the tin melt and stirring breaks the concentration gradient during the element dissolution process, ultimately resulting in a tin alloy melt with uniform composition and stable performance, laying the foundation for subsequent immersion plating to form a high-quality coating.

[0048] Optionally, in some embodiments, in step S110, Sn is heated and melted to obtain molten tin at a melting temperature of 250°C.

[0049] It is understandable that 250℃ is the suitable melting temperature of Sn. At this temperature, Sn can be completely melted into a fluid liquid without being lost due to excessive temperature or its properties changing. It can also reduce the problems of insufficient Sn melting and high liquid viscosity caused by excessively low temperature.

[0050] With this setting, the melting temperature of 250℃ can balance the fluidity and stability of the melt, allowing the subsequently added La, P, and Cu to dissolve quickly and disperse evenly, while reducing the oxidation caused by the contact between the melt and air, thus lowering the probability of oxide inclusions in the coating. At the same time, it provides a suitable temperature environment for coating adhesion during copper core immersion plating, so that the coating thickness is uniform and the bonding is tight.

[0051] Optionally, in some embodiments, in step S200, the copper core is cleaned and dried to obtain a pretreated copper core, including: S210, the copper core is soaked in a 5-8% alkaline solution to obtain the first copper core.

[0052] S220, the first copper core is immersed in an 8-12% acidic solution to obtain the second copper core; wherein the immersion time is 4-6 minutes.

[0053] S230, the second copper core is washed with water to obtain the third copper core.

[0054] S240, the third copper core is dried to obtain a pretreated copper core.

[0055] It is understood that alkaline solutions can be sodium hydroxide solutions, potassium hydroxide solutions, etc. A 5-8% alkaline solution means that the mass of the alkaline substance (taking sodium hydroxide as an example) accounts for 5-8% of the total mass of the solution; that is, every 100g of sodium hydroxide solution contains 5-8g of sodium hydroxide solute, with the remainder being solvent (deionized water or purified water). Acidic solutions can be hydrochloric acid solutions, nitric acid solutions, sulfuric acid solutions, etc. An 8-12% sulfuric acid solution means that the mass of the acidic substance (taking sulfuric acid as an example) accounts for 8-12% of the total mass of the solution; that is, every 100g of sulfuric acid solution contains 8-12g of sulfuric acid solute, with the remainder being solvent (deionized water or purified water). The soaking time is 4-6 minutes, for example, 4 minutes, 5 minutes, 6 minutes, etc., but not limited to this. When immersing the first copper core in an 8-12% acidic solution, the soaking condition is room temperature. Water washing refers to rinsing with deionized water or purified water. The drying method can be hot air drying, vacuum drying, or infrared drying, but is not limited to this.

[0056] This setup involves immersing the copper core in a 5-8% alkaline solution to obtain the first copper core. This effectively removes grease and other contaminants from the copper core surface, and the mild concentration prevents corrosion of the copper core substrate. The first copper core is then immersed in an 8-12% acidic solution for 4-6 minutes to obtain the second copper core. This process thoroughly dissolves the oxide layer (such as CuO or Cu2O) on the copper core surface and reduces the damage to the surface smoothness caused by high-temperature or prolonged acid pickling. The second copper core is then washed with water to remove residual acid and alkaline solutions and reaction products, resulting in the third copper core. The third copper core is then dried to obtain the pretreated copper core. This pretreatment creates excellent substrate conditions for the uniform adhesion of the tin alloy molten metal during subsequent immersion plating, effectively reducing defects such as plating blistering, peeling, and porosity, and ensuring the interfacial bonding strength and overall performance stability of the tin-plated copper wire.

[0057] In some embodiments, in step S210, the copper core is immersed in a 5-8% alkaline solution to obtain the first copper core. The immersion temperature is 55-65°C and the immersion time is 9-11 minutes.

[0058] It is understood that the soaking temperature is 55~65℃, for example, 55℃, 60℃, 65℃, etc., but not limited to this. The soaking time is 9~11 minutes, for example, 9 minutes, 10 minutes, 11 minutes, etc., but not limited to this.

[0059] This temperature range enhances the reactivity of the alkaline solution, accelerating the saponification and dissolution of oil. The 9-11 minute immersion time allows for thorough removal of oil from all areas of the copper core surface, reducing localized residue. Simultaneously, the gentle treatment conditions protect the copper core substrate from damage, maintaining the smoothness of the copper core surface and laying the foundation for subsequent pickling and plating adhesion.

[0060] In some embodiments, in step S230, the third copper core is dried to obtain a pretreated copper core. The drying temperature is 110~125℃ and the drying time is 18~25min.

[0061] It is understood that the drying temperature is 110~125℃, for example, 110℃, 120℃, 125℃, etc., but not limited to this. The drying time is 18~25min, for example, 18min, 20min, 25min, etc., but not limited to this.

[0062] With this setting, the drying conditions of 110~125℃ and 18~25min can quickly and effectively remove residual moisture from the surface of the copper core, thereby preventing the regeneration of the oxide layer on the surface of the copper core, ensuring the cleanliness and activity of the copper core surface, and promoting the tight bonding between the plating layer and the copper core.

[0063] In some embodiments, in step S300, the pretreated copper core is immersed in molten tin alloy and then removed to obtain a semi-finished tin-plated copper wire, comprising: S310, the pretreated copper core is vertically immersed in molten tin alloy at a speed of 0.5 m / min for 3 seconds to obtain copper wire with tin molten metal.

[0064] S320 removes excess tin from the copper wire to obtain a semi-finished tin-plated copper wire; the air pressure for blowing is 0.3 MPa.

[0065] It is understandable that vertical immersion at 0.5 m / min means that the pretreated copper core is immersed in the molten tin alloy at a uniform speed of 0.5 meters per minute, perpendicular to the surface of the molten tin alloy (at a 90° angle). Immersion for 3 seconds refers to the time the copper core remains stationary for 3 seconds after being immersed in the molten tin. The copper core can be purged using an air knife or compressed air nozzle.

[0066] This setup, with vertical immersion in molten tin alloy at a speed of 0.5 m / min, allows the copper core to make stable contact with the molten metal, reducing molten metal splashing or uneven plating thickness. The 3-second immersion time allows the copper core surface to be fully wetted and undergo a slight interfacial reaction with the molten metal, enhancing the adhesion between the plating and the copper core. The 0.3 MPa air pressure blows away excess molten tin, which not only precisely controls the plating thickness within the preset optimal range, but also reduces the risk of damage to the plating due to excessive pressure or molten tin residue due to insufficient pressure. This achieves uniform blowing away of molten tin across the entire surface of the copper wire, reducing defects such as plating protrusions and runs, ultimately resulting in a uniform, dense, and firmly bonded plating on the semi-finished tin-plated copper wire.

[0067] In some embodiments, in step S400, the semi-finished tin-plated copper wire is polished, cleaned, and dried sequentially to obtain the tin-plated copper wire. The drying temperature is 100~105℃ and the drying time is 12~15min.

[0068] It is understandable that polishing can be done using methods such as wool wheel polishing, light grinding with 400-grit sandpaper, or chemical mechanical polishing. Cleaning can be done by rinsing with deionized water or wiping with anhydrous ethanol to remove residual polishing debris, oil, and impurities. Drying can be done using hot air drying, vacuum drying, or a constant temperature oven. The drying temperature is 100~105℃, for example, 100℃, 103℃, 105℃, etc., but not limited to these. The drying time is 12~15 minutes, for example, 12 minutes, 14 minutes, 15 minutes, etc., but not limited to these.

[0069] This setup, with a gentle drying temperature of 100~105℃ and a drying time of 12~15 minutes, can efficiently remove moisture while reducing the risk of plating oxidation, grain growth, or excessive diffusion with the copper core caused by high temperatures. This ensures the density and adhesion of the plating, ultimately resulting in a finished tin-plated copper wire with a smooth and clean surface, stable dimensional accuracy, and excellent overall performance, making it suitable for the stringent requirements of high-temperature packaging scenarios in electronic devices.

[0070] The following description is based on specific embodiments.

[0071] Example 1 1) Heat and melt 10 kg of Sn at 250 °C to obtain molten tin; add 2 g of La, 1 g of P and 10 g of Cu to the molten tin and stir evenly to obtain molten tin alloy.

[0072] 2) Take an oxygen-free copper core with a diameter of 0.8 mm, and wash it with alkali (5% sodium hydroxide solution, soaked at 55℃ for 9 min), acid (8% hydrochloric acid solution, soaked at room temperature for 4 min), wash it with water (rinse with deionized water 3 times), and dry it (dry at 110℃ for 18 min) to obtain a pretreated copper core.

[0073] 3) The pretreated copper core is vertically immersed in molten tin at a speed of 0.5 m / min for 3 seconds. After immersion, excess molten tin is removed by air knife at a pressure of 0.3 MPa. A tin alloy coating with a thickness of 9 μm is formed on the surface of the copper core to obtain a semi-finished tin-plated copper wire.

[0074] 4) Polish the surface of the semi-finished tin-plated copper wire (lightly grind with 400-grit sandpaper), clean (rinse with deionized water), and dry (dry at 100℃ for 15 minutes) to obtain tin-plated copper wire.

[0075] Example 2 1) Heat and melt 10 kg of Sn at 250 °C to obtain molten tin; add 3 g of La, 2 g of P and 20 g of Cu to the molten tin and stir evenly to obtain molten tin alloy.

[0076] 2) Take an oxygen-free copper core with a diameter of 1.0 mm, and wash it with alkali (6% sodium hydroxide solution, soaked at 60℃ for 10 min), acid (10% sulfuric acid solution, soaked at room temperature for 5 min), wash it with water (rinse with deionized water 3 times), and dry it (dry at 120℃ for 20 min) to obtain a pretreated copper core.

[0077] 3) The pretreated copper core is vertically immersed in molten tin at a speed of 0.5 m / min for 3 seconds. After immersion, excess molten tin is removed by air knife at a pressure of 0.3 MPa, forming a tin alloy coating with a thickness of 9.5 μm on the surface of the copper core, thus obtaining a semi-finished tin-plated copper wire.

[0078] 4) Polish the surface of the semi-finished tin-plated copper wire (lightly grind with 400-grit sandpaper), clean (rinse with deionized water), and dry (dry at 102℃ for 13 minutes) to obtain tin-plated copper wire.

[0079] Example 3 1) Heat and melt 10 kg of Sn at 250 °C to obtain molten tin; add 5 g of La, 3 g of P and 30 g of Cu to the molten tin and stir evenly to obtain molten tin alloy.

[0080] 2) Take an oxygen-free copper core with a diameter of 1.2 mm, and wash it with alkali (8% potassium hydroxide solution, soaked at 65℃ for 11 min), acid (12% nitric acid solution, soaked at room temperature for 6 min), wash it with water (rinse with deionized water 3 times), and dry it (dry at 125℃ for 25 min) to obtain a pretreated copper core.

[0081] 3) The pretreated copper core is vertically immersed in molten tin at a speed of 0.5 m / min for 3 seconds. After immersion, excess molten tin is removed by air knife at a pressure of 0.3 MPa. A tin alloy coating with a thickness of 10 μm is formed on the surface of the copper core to obtain a semi-finished tin-plated copper wire.

[0082] 4) Polish the surface of the semi-finished tin-plated copper wire (lightly grind with 400-grit sandpaper), clean (rinse with deionized water), and dry (dry at 105℃ for 12 minutes) to obtain tin-plated copper wire.

[0083] Comparative Example 1 1) Heat and melt 10 kg of Sn at 250 °C to obtain molten tin; add 2 g of P and 20 g of Cu to the molten tin and stir evenly to obtain molten tin alloy.

[0084] 2) Take an oxygen-free copper core with a diameter of 1.0 mm, and wash it with alkali (6% sodium hydroxide solution, soaked at 60℃ for 10 min), acid (10% sulfuric acid solution, soaked at room temperature for 5 min), wash it with water (rinse with deionized water 3 times), and dry it (dry at 120℃ for 20 min) to obtain a pretreated copper core.

[0085] 3) The pretreated copper core is vertically immersed in molten tin at a speed of 0.5 m / min for 3 seconds. After immersion, excess molten tin is removed by air knife at a pressure of 0.3 MPa, forming a tin alloy coating with a thickness of 9.5 μm on the surface of the copper core, thus obtaining a semi-finished tin-plated copper wire.

[0086] 4) Polish the surface of the semi-finished tin-plated copper wire (lightly grind with 400-grit sandpaper), clean (rinse with deionized water), and dry (dry at 102℃ for 13 minutes) to obtain tin-plated copper wire.

[0087] Comparative Example 2 1) Heat and melt 10 kg of Sn at 250 °C to obtain molten tin; add 3 g of La, 2 g of P and 20 g of Cu to the molten tin and stir evenly to obtain molten tin alloy.

[0088] 2) Take an oxygen-free copper core with a diameter of 1.0 mm, and wash it with alkali (6% sodium hydroxide solution, soaked at 60℃ for 10 min), acid (10% sulfuric acid solution, soaked at room temperature for 5 min), wash it with water (rinse with deionized water 3 times), and dry it (dry at 120℃ for 20 min) to obtain a pretreated copper core.

[0089] 3) The pretreated copper core is vertically immersed in molten tin at a speed of 0.5 m / min for 3 seconds to form a tin alloy coating with a thickness of 15 μm, thus obtaining a semi-finished tin-plated copper wire.

[0090] 4) Polish the surface of the semi-finished tin-plated copper wire (lightly grind with 400-grit sandpaper), clean (rinse with deionized water), and dry (dry at 102℃ for 13 minutes) to obtain tin-plated copper wire.

[0091] Comparative Example 3 1) Heat and melt 10 kg of Sn at 250 °C to obtain molten tin; add 3 g of La, 2 g of P and 20 g of Cu to the molten tin and stir evenly to obtain molten tin alloy.

[0092] 2) Take an oxygen-free copper core with a diameter of 1.0 mm, and wash it with alkali (6% sodium hydroxide solution, soaked at 60℃ for 10 min), acid (10% sulfuric acid solution, soaked at room temperature for 5 min), wash it with water (rinse with deionized water 3 times), and dry it (dry at 120℃ for 20 min) to obtain a pretreated copper core.

[0093] 3) Using molten tin alloy as the electroplating solution, the current density is controlled at 2A / dm² and the electroplating time is 8min to form a tin alloy coating with a thickness of about 9.5μm on the surface of the copper core, thus obtaining a semi-finished tin-plated copper wire.

[0094] 4) Polish the surface of the semi-finished tin-plated copper wire (lightly grind with 400-grit sandpaper), clean (rinse with deionized water), and dry (dry at 102℃ for 13 minutes) to obtain tin-plated copper wire.

[0095] The tin-plated copper wires prepared in all the above embodiments and comparative examples were tested for high-temperature oxidation resistance, brazing performance, coating adhesion, corrosion resistance, and conductivity. The test methods are as follows: 1. High-temperature oxidation resistance: Weigh the initial mass of the sample using an electronic analytical balance and record the initial surface state using a microscope; after placing the sample in a 220℃ high-temperature constant temperature oven for 100 hours, remove it and cool it, wipe the surface with anhydrous ethanol, and observe the surface state using a microscope.

[0096] 2. Brazing performance: Wipe the oil stains on the sample surface with an alcohol swab, immerse one end of the sample (10mm length) into molten lead-free brazing filler metal at 250℃ (immersion speed 5mm / s, hold for 10s); measure the stable wetting force with a brazing wetting force tester, record the welding time with a high-speed camera, and observe whether there are any cold solder joints or missing solder joints after cooling.

[0097] 3. Coating adhesion: Fix the sample on a universal testing machine with a bending fixture and bend it 180° around a cylinder with a diameter twice its own at a speed of 5 mm / min (after bending, return to the initial state). After each bend, observe with a stereomicroscope and record the number of bends when the coating first cracks and peels off.

[0098] 4. Corrosion resistance: After wiping the sample with alcohol, place it in a neutral salt spray test chamber [5% sodium chloride solution, temperature 35℃, salt spray deposition 1~2mL / (h・80cm²)], with the sample placed at an angle of 15°~30° to the vertical direction; after continuous spraying for 48h, take out the sample, rinse it with deionized water for 5min, wipe it dry with anhydrous ethanol, and observe whether there are corrosion spots on the surface.

[0099] 5. Conductivity: Measure the diameter and length of the sample with vernier calipers and calculate the cross-sectional area. Measure the resistance at both ends of the sample with a DC double-arm bridge and calculate the resistivity according to the formula ρ=R×S / L (measure 5 times for each sample and take the average value).

[0100] The test results are shown in Table 1 below.

[0101] Table 1 According to the test data in Table 1, the tin-plated copper wires prepared using the raw materials and preparation method of this application exhibit superior high-temperature oxidation resistance. In Examples 1-3, after being stored at 220℃ for 100 hours, the surface of the tin-plated copper wires showed no obvious oxidation and remained bright. In contrast, the surface of Comparative Example 1 showed obvious oxidation and yellowing, while the surface of Comparative Example 3 showed significant oxidation and a dull color. This highlights that the synergistic ratio of La, P, Cu, and Sn in this application effectively inhibits oxidation reactions at high temperatures. Regarding brazing performance, the welding time of the examples was only 0.63~0.64s, with no instances of incomplete or missed welds, far superior to Comparative Example 1's 0.87s (a few incomplete welds) and Comparative Example 3's 0.92s (multiple incomplete welds and a few missed welds). This demonstrates that the combination of the component ratio and hot-dip plating process in this application optimizes the wetting performance of the coating and ensures welding reliability. Regarding coating adhesion, the example can withstand 5 180° bends without cracking or peeling, while Comparative Example 1 cracked significantly after 3 bends, and Comparative Example 3 cracked after 2 bends and partially peeled off after 3 bends. This shows that the synergistic effect of the components and the process specifications in this application significantly enhance the interfacial adhesion between the coating and the copper core. In terms of corrosion resistance, the example showed no corrosion spots or rust after a 48-hour neutral salt spray test, while all comparative examples showed varying degrees of corrosion, confirming that the coating in this application has higher density and better protective effect. Regarding electrical conductivity, the resistivity of the example is only 0.0158~0.0161 Ω・mm² / m, lower than all comparative examples. Therefore, the tin-plated copper wire prepared in this application has stronger oxidation resistance in high-temperature environments, is less prone to forming a loose oxide film, and can maintain a bright surface for a long time; its brazing performance is more stable, its wettability decreases slowly, reducing the risk of poor soldering and missing soldering; the coating has a higher bonding force with the copper core, is not easy to crack or fall off, and the coating has good density and better corrosion resistance, which can stably adapt to high-performance application scenarios of electronic devices such as high-temperature packaging.

[0102] 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 tinned copper wire, characterized in that, The tin-plated copper wire comprises a copper core and a tin alloy plating layer, and the tin alloy plating layer comprises the following components: La, 0.02-0.05wt%; P, 0.01-0.03wt%; Cu, 0.10-0.30wt%; the rest is Sn.

2. The tinned copper wire of claim 1, wherein, The diameter of the copper core is 0.8-1.2mm, and the thickness of the tin alloy plating layer is 9-10μm.

3. The tinned copper wire of claim 1, wherein, The copper core is an oxygen-free red copper core with a copper content of ≥99.99%.

4. A method of producing a tinned copper wire, characterized by, The preparation method of the tin-plated copper wire comprises the following steps: providing the components of the tin alloy plating layer and the copper core according to any one of claims 1-3, melting the components of the tin alloy plating layer to obtain a tin alloy melt; cleaning and drying the copper core to obtain a pretreated copper core; immersing the pretreated copper core in the tin alloy melt and taking it out to obtain a semi-finished tin-plated copper wire; polishing, cleaning and drying the semi-finished tin-plated copper wire in sequence to obtain a tin-plated copper wire.

5. The method of producing a tinned copper wire according to claim 4, wherein The melting of the components of the tin alloy plating layer to obtain a tin alloy melt comprises the following steps: melting Sn by heating to obtain a tin melt; adding La, P and Cu into the tin melt and stirring to obtain a tin alloy melt.

6. The method of producing a tinned copper wire according to claim 5, wherein In the step of melting Sn by heating to obtain a tin melt, the melting temperature is 250℃.

7. The method of producing a tinned copper wire according to claim 4, wherein The cleaning and drying of the copper core to obtain a pretreated copper core comprises the following steps: immersing the copper core in an alkaline solution with a concentration of 5-8% to obtain a first copper core; immersing the first copper core in an acidic solution with a concentration of 8-12% to obtain a second copper core; wherein the immersion time is 4-6min; washing the second copper core with water to obtain a third copper core; drying the third copper core to obtain a pretreated copper core.

8. The method of producing a tinned copper wire according to claim 7, wherein In the step of immersing the copper core in an alkaline solution with a concentration of 5-8% to obtain a first copper core, the immersion temperature is 55-65℃, and the immersion time is 9-11min; In the step of drying the third copper core to obtain a pretreated copper core, the drying temperature is 110-125℃, and the drying time is 18-25min.

9. The method of producing a tinned copper wire according to claim 4, wherein The immersion of the pretreated copper core in the tin alloy melt to obtain a semi-finished tin-plated copper wire comprises the following steps: immersing the pretreated copper core vertically in the tin alloy melt at a speed of 0.5m / min for 3s to obtain a tin-liquid-coated copper wire; blowing off the excess tin liquid on the tin-liquid-coated copper wire to obtain a semi-finished tin-plated copper wire; wherein the air pressure for blowing off is 0.3MPa.

10. The method of producing a tinned copper wire according to claim 4, wherein In the step of polishing, cleaning and drying the semi-finished tin-plated copper wire in sequence to obtain a tin-plated copper wire, the drying temperature is 100-105℃, and the drying time is 12-15min.

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