Copper-silver superfine wire and preparation method thereof

Abstract

The application discloses a kind of copper silver superfine filaments and its preparation method, the copper silver superfine filaments, by silver, strontium, copper and inevitable impurities, wherein silver in copper silver superfine micro micro filament mass fraction ≤0.003%, strontium in copper silver superfine micro filament mass fraction ≤0.005%, the preparation method is: in double ditch electric furnace, copper is refined to obtain melt, then through wire feeder, silver wire and strontium wire are added to the melt, when copper alloy liquid in line with design composition is obtained, the copper alloy rod is formed by up-drawing, the copper alloy rod is continuously extruded to obtain wire rod, the wire rod is sequentially subjected to rough drawing, fine drawing to obtain copper silver superfine filament, the copper silver superfine filament of the application has the advantages of high plasticity, high hardness, high oxidation resistance, easy welding, high conductivity and the like, and is widely used in communication, microelectronic semiconductor device field.

Description

Technical Field

[0001] This invention relates to a copper-silver ultrafine wire and its preparation method, belonging to the field of fine processing and preparation of non-ferrous metal materials. Background Technology

[0002] Copper microfilaments are widely used in integrated circuits, micromotors, LCDs (liquid crystal displays), high-speed broadband transmission cables, high-speed transmission lines, and mobile communication microfilaments. With the rapid development of the electronics and information industry, especially laptops, mobile communication products, and terminal signal transmission products, the demand for copper microfilaments will continue to increase. However, due to the special specifications of microfilaments, there are very few domestic companies capable of producing them, and these products are heavily reliant on imports, especially in the high-end microfilament field (wire diameter below 0.05mm), where products are mainly imported from manufacturers in Germany, Japan, and South Korea. These microfilaments generally require high conductivity, good solderability, and single-wire lengths exceeding 3000-5000 meters. Because microfilaments are prone to breakage and oxidation during processing, their yield is low, and the processing technology is difficult. Currently, the main method for processing these microfilaments in China is to use the upward drawing method to produce oxygen-free copper rods, roll them to 8-10mm diameter wire, and then draw them until they become finished wires. This process has drawbacks such as a long workflow, complex control, low yield, and difficulty in processing microfilaments with a diameter of less than 0.05 mm. A literature search revealed no publicly available reports identical to this invention. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the first objective of this invention is to provide a copper-silver ultrafine wire with high plasticity, strong oxidation resistance, and good solderability.

[0004] The second objective of this invention is to provide a method for preparing copper-silver ultrafine filaments.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] This invention provides a copper-silver ultrafine filament, which is composed of silver, strontium, copper and unavoidable impurities, wherein the mass fraction of silver in the copper-silver ultrafine filament is ≤0.003% and the mass fraction of strontium in the copper-silver ultrafine filament is ≤0.005%.

[0007] In this invention, the total content of trace impurity elements ranges from 0.001% to 0.006%.

[0008] This invention increases the elongation of copper wire by adding trace amounts of silver and strontium (Sr) alloying elements, thereby improving its plastic processing capability and reducing its hardness to a certain extent. The alloying of trace amounts of silver and strontium rare earth elements improves the overall performance of ultrafine copper-based wires, solving the major problems of easy breakage, easy oxidation, and difficulty in welding of fine copper wires, which affect their processing, preparation, and use performance. Furthermore, the addition of silver also increases the conductivity of copper microwires.

[0009] However, in this invention, the amount of silver and strontium (Sr) added needs to be effectively controlled. If the silver content is too low, the plasticity and conductivity of the material cannot be improved, while if it is too high, the conductivity will also decrease. Generally, it is around 99.99%. At the same time, the plasticity is reduced in the fine drawing process, and it is impossible to continue drawing. If the amount of strontium added is too low, it will not play a role in purification and grain refinement. If it is too high, rare earth compounds will be formed. Rare earth compounds have high melting points, which is not conducive to upward drawing. Moreover, the presence of rare earth compounds reduces the plasticity of the metal, that is, the wire will break and cannot be drawn further after a certain amount of deformation.

[0010] In a preferred embodiment, the copper-silver ultrafine filaments have the following composition by mass percentage: silver 0.001%-0.003%; strontium 0.0005%-0.005%; the balance being copper and unavoidable impurities.

[0011] In a further preferred embodiment, the copper-silver ultrafine filament has the following composition by mass percentage: silver 0.0003%-0.00036%; strontium 0.0005%-0.0045%; the balance being copper and unavoidable impurities.

[0012] This invention provides a method for preparing copper-silver ultrafine wires. Copper is refined in a double-ditch electric furnace to obtain a melt. Silver wire and strontium wire are then added to the melt through a wire feeding machine to obtain a copper alloy liquid with the designed composition. The melt is then drawn upward to form a copper alloy rod. The copper alloy rod is continuously extruded to obtain a wire rod. The wire rod is then subjected to coarse drawing and fine drawing to obtain copper-silver ultrafine wires.

[0013] In this invention, the purity of the raw materials used is above 99.998%. In actual operation, high-purity copper raw materials are loaded into a medium-frequency double-groove induction furnace for melting. After refining to obtain the melt, silver and strontium wires are inserted into the melting chamber of the double-groove furnace using a wire feeding machine at a set speed. The wire feeding machine speed needs to be adjusted according to the analysis of the alloy composition before the furnace. Using the method of this invention, by controlling the addition of silver and strontium wires, a copper alloy rod with excellent plasticity that conforms to the designed composition can be controllably obtained. Then, through continuous extrusion, due to the heat generated by friction and the deformation heat of the material itself, the plasticity of the copper-silver alloy is greatly improved, and fine and uniform recrystallized grains are obtained. These fine recrystallized grains are very beneficial for subsequent coarse and fine drawing, allowing the drawing to continue, thereby obtaining ultra-fine wires with an infinitely long diameter of 0.01-0.05 mm.

[0014] In a preferred embodiment, the refining temperature is 1200℃-1280℃, and the refining time is 20-30 minutes.

[0015] In a preferred embodiment, the diameters of the silver wire and the strontium wire are both 2-3 mm.

[0016] In a preferred embodiment, the silver wire is laid out at a speed of 1-3 cm / min, and the strontium wire is laid out at a speed of 3-5 cm / min.

[0017] In actual operation, the wire feeding speed should be adjusted within the above range according to the analysis of the alloy composition in front of the furnace. If it is not within the above range, the composition will be inaccurate.

[0018] In a preferred embodiment, the diameter of the copper alloy rod is 16-20mm.

[0019] In actual operation, a 400 continuous extrusion press is used for extrusion.

[0020] In a preferred embodiment, the continuous extrusion speed is 3-5 rpm. The inventors have discovered that the continuous extrusion speed needs to be effectively controlled. If the extrusion speed is too low, the extruder will stall; if it is too high, the extrusion temperature will rise, causing grain growth and reduced plasticity.

[0021] In a preferred embodiment, the continuous extruder does not have a buffer chamber; the billet enters directly into the deformation die cavity through the friction shoe, and the discharge direction is tangential to the extrusion wheel.

[0022] The continuous extrusion press of this invention is similar to equal angle extrusion, which makes the grains of the billet more uniform and improves the plasticity of the material during the extrusion process.

[0023] In a preferred embodiment, after continuous extrusion, the resulting wire rod is cooled in a water tank using an antioxidant. This cooling method prevents oxidation of the wire rod surface.

[0024] In a preferred embodiment, the diameter of the rod is 8-10 mm.

[0025] After obtaining the rod, it can be drawn to the target diameter using existing conventional processes. This invention can achieve this. Microfilaments smaller than 0.05 mm

[0026] In a preferred embodiment, annealing is performed between both the coarse drawing passes and the fine drawing passes. The annealing temperature is 480–550°C, and the annealing time is 0.5–1 hour.

[0027] In actual operation, the process of drawing an 8mm diameter wire rod down to an ultrafine wire diameter of 0.05mm is as follows:

[0028] Rough drawing: The processing rate is 86%, with 9 passes. The equipment has a built-in annealing device during the drawing process to prevent the wire from breaking.

[0029] Fine drawing 1: Processing rate: 81.2%

[0030] Fine drawing 2: Processing rate: 81.44%

[0031] Fine drawing 3: Processing rates: 93% / 97%;

[0032] Fine drawing 4: Wire diameter.

[0033] The wire is also annealed during the fine drawing process to prevent it from breaking.

[0034] Principles and advantages

[0035] The copper-silver ultrafine filaments provided by this invention increase the elongation of the copper wire and improve its plastic processing ability by using trace amounts of silver and strontium (Sr) alloying elements, while reducing the hardness of the copper wire to a certain extent. The alloying of trace amounts of silver and strontium rare earth elements improves the comprehensive performance of ultrafine copper-based wires, solving the major problems of easy breakage, easy oxidation, and difficulty in welding of fine copper wires, which affect the processing, preparation, and use performance. Furthermore, the addition of silver also increases the conductivity of the copper microfilaments.

[0036] The preparation method provided by this invention involves melting high-purity copper raw material in a medium-frequency double-groove induction furnace. After refining to obtain a melt, silver and strontium wires are inserted into the melting chamber of the double-groove furnace using a wire feeding machine at a set speed. The speed of the wire feeding machine needs to be adjusted according to the analysis composition of the alloy before the furnace. Using the method of this invention, by controlling the addition of silver and strontium wires, a copper alloy rod with excellent plasticity that conforms to the design composition can be controllably obtained. Then, through continuous extrusion, the plasticity of the copper-silver alloy is greatly improved due to the heat generated by friction and the deformation heat of the material itself. Moreover, fine and uniform recrystallized grains are obtained. These fine recrystallized grains are very beneficial to subsequent coarse and fine drawing, allowing the drawing to continue, thereby obtaining an infinitely long fine wire.

[0037] The copper-silver ultrafine filaments disclosed in this invention have advantages such as high plasticity, high oxidation resistance, easy welding and high conductivity, and have broad application prospects in the field of microelectronics. Detailed Implementation

[0038] The present invention will be further described in detail below with reference to specific embodiments, but the present invention is not limited to the following embodiments.

[0039] Example 1:

[0040] The copper-silver ultrafine wire material contains Ag 0.003% by weight, Sr 0.005%, other trace impurities totaling 0.0060%, with the balance being Cu. High-purity copper is first placed at the bottom of a twin-ditch electric furnace. When the furnace temperature reaches 1250℃, this temperature is maintained for refining for 20 minutes. After the copper alloy solution in the twin-ditch electric furnace is thoroughly mixed, silver and strontium wires with a diameter of 2mm are fed in using a wire feeding machine. The feeding speed of the silver wire is 1cm / min, and the feeding speed of the strontium wire is 5cm / min. Then, based on the composition analysis before the furnace, when the alloy composition meets the specified requirements, the copper rod is drawn up. The prepared 16mm diameter copper rod is continuously extruded on a 400 continuous extrusion press (without a buffer chamber; the billet enters directly into the deformation die cavity through the friction shoe, and the discharge direction is tangential to the extrusion rollers). The extrusion speed of the continuous extrusion press is 3rd / min. The prepared 8mm diameter copper rod blank is passed through a water tank and cooled with an anti-oxidant, then drawn to the specified size according to conventional processes: Rough drawing: The processing rate is 86%, with 9 passes. The equipment includes an annealing device during the drawing process to prevent wire breakage. Fine drawing 1: Processing rate 81.2%: Fine drawing 2: Processing rate 81.44%: Fine drawing 3: Processing rate 93%; Fine drawing 4: The ultra-fine filaments are drawn with an annealing device during the same fine drawing process as the coarse drawing process to prevent the filaments from breaking.

[0041] The final product specifications are shown in Table 1:

[0042] Example 2:

[0043] The copper-silver ultrafine wire material contains Ag 0.0036% by weight, Sr 0.0045%, and other trace impurities totaling 0.0060%, with the balance being copper. High-purity copper is first placed at the bottom of a double-ditch electric furnace. When the furnace temperature reaches 1280℃, this temperature is maintained for refining for 30 minutes. After the copper alloy solution in the double-ditch electric furnace is thoroughly mixed, silver and strontium wires with a diameter of 2mm are fed in using a wire feeding machine. The feeding speed of the silver wire is 2cm / min, and the feeding speed of the strontium wire is 5cm / min. The composition is then analyzed before the furnace. When the alloy composition meets the specified requirements, the copper rod is drawn. The prepared 16mm diameter copper rod is continuously extruded on a 400 continuous extrusion press at a speed of 5rd / min. The prepared 8mm diameter copper rod billet is then drawn to the specified dimensions using conventional processes: rough drawing: The processing rate is 86%, with 9 passes. The equipment includes an annealing device during the drawing process to prevent wire breakage. Fine drawing 1: Processing rate 81.2%: Fine drawing 2: Processing rate 81.44%: Fine drawing 3: Processing rate 97%; Fine drawing 4: The ultra-fine copper wire has the same diameter as the coarse drawing process and comes with an annealing device to prevent the wire from breaking.

[0044] The final product specifications are shown in Table 1:

[0045] Table 1 Properties of Copper-Silver Ultrafine Filaments

[0046]

[0047] Comparative Example 1

[0048] The other conditions were the same as in Example 1, except that silver was not added. As a result, the wire broke during the drawing process, especially in the last pass where the plasticity was very low, causing the wire to break and preventing the next drawing pass.

[0049] Comparative Example 2

[0050] The other conditions were the same as in Example 1, except that the strontium content was 0.1%. The wire still broke during the drawing process, indicating that although the addition of strontium has the effect of refining the grains, it does not improve its plasticity compared with the effect of adding silver.

[0051] Comparative Example 3

[0052] All other conditions were the same as in Example 1, except that the extrusion speed was 6 rd / min. The result was wire breakage during the drawing process. This was because the excessively high extrusion speed caused the extrusion temperature to rise, leading to grain growth and a decrease in the material's plasticity. Wire breakage was also likely to occur in subsequent drawing passes.

Claims

1. A method for preparing copper-silver ultrafine wires, wherein copper is refined in a double-ditch electric furnace to obtain a melt, and then silver wire and strontium wire are added to the melt through a wire feeding machine to obtain a copper alloy liquid with the designed composition. The melt is then drawn upward to form a copper alloy rod, and the copper alloy rod is continuously extruded to obtain a wire rod. The wire rod is then subjected to coarse drawing and fine drawing in sequence to obtain copper-silver ultrafine wires. The diameters of the silver wire and strontium wire are both 2-3 mm; The silver wire is laid out at a speed of 1-3 cm / min, and the strontium wire is laid out at a speed of 3-5 cm / min. The continuous extrusion speed is 3-5 seconds / min; The continuous extrusion press used in the continuous extrusion does not have a buffer chamber. The billet enters directly into the deformation die cavity through the friction shoe, and the discharge direction is tangential to the extrusion wheel. The copper-silver ultrafine filaments, by mass percentage, have the following composition: silver 0.0001%-0.001%; ​​strontium 0.0005%-0.005%; the balance being copper and unavoidable impurities.

2. The method for preparing copper-silver ultrafine filaments according to claim 1, characterized in that: The refining temperature is 1200℃-1280℃, and the refining time is 20-30 minutes.

3. The method for preparing copper-silver ultrafine filaments according to claim 1, characterized in that: The diameter of the copper alloy rod is 16-20mm.

4. The method for preparing copper-silver ultrafine filaments according to claim 1, characterized in that: The diameter of the rod is 8-10mm.

5. The method for preparing copper-silver ultrafine wires according to claim 1, characterized in that: Annealing is performed between both the coarse drawing passes and the fine drawing passes. The annealing temperature is 480~550℃ and the annealing time is 0.5-1h.

6. The method for preparing copper-silver ultrafine wires according to claim 1, characterized in that: The copper-silver ultrafine filaments, by mass percentage, have the following composition: silver 0.0003%-0.00036%; strontium 0.0005%-0.0045%; the balance being copper and unavoidable impurities.

Images