Superfine welding wire for brazing mobile phone parts and manufacturing process of superfine welding wire

Abstract

The invention belongs to the technical field of welding materials, and particularly relates to a superfine welding wire for mobile phone component brazing and a manufacturing process of the superfine welding wire for mobile phone component brazing. Classifying the actual extrusion ratio and extrusion temperature into a preset extrusion parameter interval according to the actual extrusion ratio and extrusion temperature; calling a differential wire drawing path parameter combination matched with the interval, wherein the combination at least comprises a single-pass maximum reducing ratio and an intermediate annealing triggering rule; and drawing and annealing are carried out according to the combination, and the superfine welding wire meeting the requirement of a solid welding wire with the diameter reaching 0.6 mm is obtained. According to the method, the problems of high wire breakage rate and poor stability caused by the fact that a traditional unified path cannot adapt to blanks in different states are solved through differential matching of extrusion parameter interval judgment and wire drawing paths, and the method is particularly suitable for stable production of BCu76AgP alloy ultrafine wires.

Description

Technical Field

[0001] This invention relates to the field of welding materials technology, specifically to an ultrafine welding wire for brazing mobile phone components and its manufacturing process. Background Technology

[0002] As consumer electronics products such as smartphones continue to evolve towards miniaturization and high-density integration, the micro-spot brazing of their internal precision components, such as micro-antennas, sensors, and connectors, places stringent requirements on the diameter of the welding wire, often necessitating the use of ultra-fine welding wires with a diameter of 0.6 mm. High-silver, high-phosphorus copper-based alloys, due to their excellent electrical and thermal conductivity and brazing properties, have become ideal materials for such applications. However, the stable and efficient processing of these alloys into ultra-fine wires that meet the required diameter has long been a challenging technological problem for the industry. Traditional ultra-fine welding wire manufacturing processes generally employ a fixed-path scheme based on the final target diameter. This means that regardless of the actual conditions of the preceding extrusion processes, such as extrusion temperature and extrusion ratio, a uniform reduction rate and annealing regime are applied. This approach ignores the fact that differences in extrusion parameters directly lead to significant differences in the microstructure and plasticity of the billet, resulting in a severe disconnect between the subsequent drawing process and the actual mechanical properties of the billet. This method is prone to frequent wire breakage due to deformation overload for blanks with poor plasticity, resulting in poor production stability. For blanks with good plasticity, it sacrifices efficiency due to conservative process and makes it difficult to accurately control the evolution of the microstructure. Ultimately, this leads to large fluctuations in the dimensional consistency, surface quality and mechanical properties of the welding wire products, making it difficult to meet the stringent requirements for raw material consistency in high-precision manufacturing fields such as mobile phone components.

[0003] Patent application CN202310758571.0 discloses a manufacturing process for a non-copper-plated solid welding wire. The process involves five steps: wire rod pretreatment, wire rod drawing, post-treatment cleaning, dehydration and drying, and active material coating. The active powder components, by weight, are: 10-30 parts graphene, 10-20 parts polytetrafluoroethylene (PTFE), 20-30 parts tungsten disulfide, 15-25 parts boron nitride, and 15-25 parts titanium dioxide. However, materials such as graphene and PTFE are difficult to apply evenly and firmly as surface coatings, easily detaching in subsequent processes to form dust. Furthermore, their excellent conductivity may interfere with the stability of the welding current. Patent application CN201310189530.0 discloses a novel method for processing and manufacturing solid welding wire. This method sequentially includes the following steps starting from wire rod: forging, annealing, continuous drawing, scraping, and ultrasonic cleaning, ultimately obtaining a bright, fine-grained solid welding wire. The forging process involves two rapid forging passes of a 12mm aluminum alloy wire rod, with diameters of φ4.8mm and φ2.4mm for each pass, and reduction rates of 60% and 50% for each pass, respectively. The solid welding wire includes various steel welding wires and various non-ferrous metal and non-ferrous metal alloy welding wires. However, directly reducing the diameter of a φ12mm wire rod to φ2.4mm through two rotary forging passes, and only annealing at 400℃ for 1 hour between passes and after the final forging, results in such a large deformation during rotary forging, leading to material embrittlement and easy cracking. Even annealing cannot completely eliminate the texture and residual stress.

[0004] Therefore, there is an urgent need for a manufacturing process that can intelligently match differentiated wire drawing paths based on actual extrusion conditions in order to achieve stable, efficient, and high-quality preparation of high-silver and high-phosphorus ultrafine welding wire. Summary of the Invention

[0005] To address the aforementioned issues, this invention provides an ultrafine welding wire for brazing mobile phone components and its manufacturing process. By dividing the actual process parameters, such as the extrusion temperature and extrusion ratio after hot extrusion, into three preset intervals, and dynamically matching differentiated wire drawing path parameter combinations accordingly, including the maximum reduction ratio per pass and intermediate annealing triggering rules, and combining these with synergistic post-processing measures such as annealing, cooling, and surface treatment, a high-silver, high-phosphorus ultrafine welding wire with excellent performance and a diameter of 0.6mm is obtained, meeting the requirements for a solid welding wire.

[0006] The technical solution of the present invention to solve the above problems is as follows:

[0007] A manufacturing process for ultrafine welding wire used in brazing mobile phone components includes the following steps:

[0008] Step S1, Raw material pretreatment and extrusion: The surface of the solder blank is cleaned, and then hot extrusion is performed under the set extrusion parameters to obtain the extruded blank; the extrusion parameters include extrusion ratio, extrusion temperature and extrusion speed, wherein the extrusion ratio is the ratio of the cross-sectional area of ​​the blank before extrusion to the cross-sectional area of ​​the blank after extrusion, and the extrusion speed is controlled at 5-10mm / s;

[0009] Step S2, Extrusion Parameter Range Determination: Obtain the actual extrusion ratio and extrusion temperature from Step S1, and classify the extruded billet into the corresponding extrusion parameter range according to the preset threshold range; the extrusion parameter range includes at least a first range, a second range, and a third range;

[0010] Step S3, Wire drawing path parameter matching: Based on the extrusion parameter range to which the extruded billet belongs, call the differentiated wire drawing path parameter combination that is pre-set for that range; the wire drawing path parameter combination includes at least the maximum reduction ratio per pass and the intermediate annealing trigger rule;

[0011] Step S4, Differentiated wire drawing process: The extruded billet is fed into the wire drawing equipment, and multiple wire drawing passes are performed according to the matching wire drawing path parameter combination. During this process, intermediate annealing is performed according to the intermediate annealing triggering rule until the wire diameter reaches the requirement of 0.6mm solid wire.

[0012] Step S5, Post-processing: The drawn welding wire is subjected to cooling and surface treatment in sequence to obtain the finished ultrafine welding wire.

[0013] Furthermore, the solder blank is BCu76AgP solder, whose chemical composition by mass percentage is: Cu 75-77%, Ag 1.5-2.5%, P 5.5-6.5%, with the balance being unavoidable impurities.

[0014] Further, the first range is defined as: extrusion temperature 450℃-500℃, extrusion ratio 2:1-3:1; the second range is defined as: extrusion temperature 500℃-550℃, extrusion ratio 3:1-5:1; and the third range is defined as: extrusion temperature 550℃-600℃, extrusion ratio 5:1-6:1.

[0015] Furthermore, in step S1, the selection criteria for the extrusion ratio are as follows: when the initial cross-sectional diameter of the solder blank is 3mm-6mm, the extrusion ratio is set to 3:1-6:1; when the initial cross-sectional diameter of the solder blank is less than 3mm, the extrusion ratio is set to 2:1-4:1.

[0016] Furthermore, in step S3, the maximum reduction ratio per single pass for each interval is as follows: first interval: not exceeding 15%; second interval: not exceeding 18%; third interval: not exceeding 22%.

[0017] Furthermore, the intermediate annealing triggering rules for each interval are as follows: Intermediate annealing is triggered when the cumulative diameter reduction reaches 50% in the first interval; intermediate annealing is triggered after every 4-5 drawing passes in the second interval; intermediate annealing is triggered after every 2-3 drawing passes in the third interval.

[0018] Furthermore, the intermediate annealing is carried out under a protective atmosphere, with an annealing temperature of 300℃-450℃ and an annealing time of 5–15 min.

[0019] Furthermore, the cooling process in step S5 uses water bath cooling with a cooling water temperature of 20℃-30℃; the surface treatment uses pickling or protective atmosphere annealing.

[0020] An ultrafine welding wire for brazing mobile phone components is made of BCu76AgP solder and prepared by the above-mentioned manufacturing process. The diameter of the ultrafine welding wire meets the requirements of a solid welding wire of 0.6 mm.

[0021] The present invention has the following beneficial effects:

[0022] The present invention provides a manufacturing process for ultrafine welding wire used in brazing mobile phone components, and the ultrafine welding wire produced based on this process has several outstanding advantages. In the manufacturing process, during the raw material pretreatment and extrusion stages, after surface cleaning of the solder blank, extrusion parameters are precisely set for hot extrusion forming. The extrusion ratio is rationally selected based on the initial cross-sectional diameter of the blank, ensuring the quality of the extruded blank and creating favorable conditions for subsequent processing. The extrusion parameter range determination classifies the extruded blank into different ranges, and the wire drawing path parameter matching calls differentiated combinations of wire drawing path parameters according to these ranges. This precise matching makes the wire drawing process more targeted. Different extrusion conditions correspond to different single-pass maximum diameter reduction ratios and intermediate annealing trigger rules, effectively avoiding problems such as wire breakage and uneven performance caused by improper parameters. In differentiated wire drawing processing, multi-pass wire drawing combined with rule-based intermediate annealing, performed under a protective atmosphere at appropriate temperature and time, can eliminate internal stress generated during wire drawing, improve the wire microstructure, and ensure stable wire performance. In the post-processing stage, surface treatments such as water bath cooling at specific temperatures and pickling or protective atmosphere annealing are employed to further improve the surface quality and overall performance of the welding wire. The entire solution involves close collaboration between all steps, forming a complete, scientific, and efficient manufacturing system from raw materials to finished products. This system can stably produce high-quality ultrafine welding wires with a diameter of up to 0.6mm, meeting the stringent requirements of high-end welding fields such as mobile phone components for ultrafine welding wires. Attached Figure Description

[0023] Figure 1 The graph shows the elongation test results of the ultrafine welding wires for brazing mobile phone components prepared in Examples 1-3 and Comparative Examples 1-4 of this invention.

[0024] Figure 2 The figures show the tensile strength test results of the ultrafine welding wires for brazing mobile phone components prepared in Examples 1-3 and Comparative Examples 1-4 of this invention. Detailed Implementation

[0025] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0026] The raw materials used in the following examples are all commercially available products.

[0027] Example 1

[0028] Step S1, Raw Material Pretreatment and Extrusion: Select BCu76AgP solder blank, whose chemical composition by mass percentage is: Cu 76.0%, Ag 2.0%, P 6.0%, with the balance being unavoidable impurities; the initial cross-section diameter of the blank is 2.5mm, and the length is 500mm. Grind the surface of the blank with sandpaper to remove oxide scale and burrs, then ultrasonically clean it with anhydrous ethanol for 10 minutes to remove oil stains, and let it air dry. Place the pretreated blank into a horizontal extruder, set the extrusion parameters: extrusion ratio 2.8:1, extrusion temperature 490℃, extrusion speed 6mm / s, and obtain an extruded blank with a diameter of 1.48mm after hot extrusion forming.

[0029] Step S2, Determining the range of extrusion parameters: The actual extrusion temperature is 490℃ and the extrusion ratio is 2.8:1, which falls into the first range;

[0030] Step S3, drawing path parameter matching: call the first interval adaptation parameters, the maximum reduction ratio of a single pass shall not exceed 15%, and the intermediate annealing trigger rule is triggered when the cumulative reduction reaches 50%;

[0031] Step S4, Differentiated Wire Drawing Process: The extruded billet is fed into a wire drawing machine using a carbide die. Eight drawing passes are set, with the diameter reduction ratio controlled at 13%-15% in each pass, and the drawing speed at 8 m / min. When the cumulative diameter reduction reaches 50%, intermediate annealing is performed under an argon protective atmosphere at 330℃ for 10 min. After annealing, the billet is cooled to room temperature and drawn further until the diameter reaches 0.6 mm.

[0032] Step S5, Post-treatment: Use water bath cooling at 24℃, completely immerse the welding wire in water for 3.5 minutes, and let it drain naturally after cooling; use pickling for surface treatment, mix 30% sulfuric acid and deionized water at a volume ratio of 1:1, soak for 4 minutes, rinse with clean water until neutral after pickling, and then dry at 110℃ for 10 minutes to obtain the finished ultrafine welding wire.

[0033] Finished product inspection results: diameter 0.6mm, dimensional tolerance ±0.008mm; tensile strength 358MPa, elongation 15.5%; one wire breakage within 8 hours of continuous drawing, wire breakage rate 0.35%; smooth surface without cracks or oxidation spots.

[0034] Example 2

[0035] Step S1, Raw Material Pretreatment and Extrusion: Select BCu76AgP solder blank, whose chemical composition by mass percentage is: Cu 75.5%, Ag 2.2%, P 5.8%, with the balance being unavoidable impurities; the initial cross-sectional diameter of the blank is 4mm, and the length is 500mm. The surface cleaning method is the same as in Example 1. Place the pretreated blank into a horizontal extruder, set the extrusion parameters: extrusion ratio 4.0:1, extrusion temperature 520℃, extrusion speed 8mm / s, and obtain an extruded blank with a diameter of 2.0mm after hot extrusion forming;

[0036] Step S2, Determining the range of extrusion parameters: The actual extrusion temperature is 520℃ and the extrusion ratio is 4.0:1, which falls into the second range;

[0037] Step S3, drawing path parameter matching: call the second interval adaptation parameters, the maximum diameter reduction ratio of a single pass does not exceed 18%, and the intermediate annealing trigger rule is triggered after every 4 drawing passes are completed;

[0038] Step S4, Differentiated Wire Drawing Process: The extruded billet is fed into a wire drawing machine using a carbide die. Nine wire drawing passes are set, with the diameter reduction ratio controlled at 16%-18% for each pass, and the wire drawing speed at 11 m / min. After every four wire drawing passes, intermediate annealing is performed under a nitrogen protective atmosphere at 350℃ for 12 minutes. After annealing, the billet is cooled to room temperature, and wire drawing continues until the diameter reaches 0.6 mm.

[0039] Step S5, Post-treatment: Water bath cooling is used with a water temperature of 28℃. The welding wire is completely immersed in the water for 4 minutes and then allowed to drain naturally. Surface treatment is performed using a protective atmosphere annealing method with nitrogen protection at a temperature of 300℃ for 12 minutes to obtain the finished ultrafine welding wire.

[0040] Finished product inspection results: Diameter 0.6mm, dimensional tolerance ±0.01mm; tensile strength 358MPa, elongation 15.8%; one wire breakage within 8 hours of continuous drawing, wire breakage rate 0.4%; excellent surface quality, no obvious defects.

[0041] Example 3

[0042] Step S1, Raw Material Pretreatment and Extrusion: Select BCu76AgP solder blank, whose chemical composition by mass percentage is: Cu 76.5%, Ag 1.8%, P 6.2%, with the balance being unavoidable impurities; the initial cross-sectional diameter of the blank is 5mm, and the length is 500mm. The surface cleaning method is the same as in Example 1. Place the pretreated blank into a horizontal extruder, set the extrusion parameters: extrusion ratio 5.2:1, extrusion temperature 570℃, extrusion speed 7mm / s, and obtain an extruded blank with a diameter of 2.17mm after hot extrusion forming;

[0043] Step S2, Determining the range of extrusion parameters: The actual extrusion temperature is 570℃ and the extrusion ratio is 5.2:1, which falls into the third range;

[0044] Step S3, drawing path parameter matching: call the third interval adaptation parameters, the maximum diameter reduction ratio of a single pass does not exceed 22%, and the intermediate annealing trigger rule is triggered after every 3 drawing passes are completed;

[0045] Step S4, Differentiated Wire Drawing Process: The extruded billet is fed into a wire drawing machine using a carbide die. Six wire drawing passes are set, with the diameter reduction ratio controlled at 20%-22% for each pass. The wire drawing speed is 12 m / min. After every three wire drawing passes, intermediate annealing is performed under an argon protective atmosphere at 390℃ for 9 minutes. After annealing, the wire is cooled to room temperature and drawn further until the diameter reaches 0.6 mm.

[0046] Step S5, Post-treatment: Use water bath cooling at 23℃, completely immerse the welding wire in water for 2.5 minutes, and let it drain naturally after cooling; use pickling for surface treatment, mix 30% sulfuric acid and water in a 1:1 ratio, soak for 3.5 minutes, rinse with clean water until neutral, and then dry at 115℃ for 10 minutes to obtain the finished welding wire.

[0047] Finished product inspection results: diameter 0.6mm, dimensional tolerance ±0.009mm; tensile strength 360MPa, elongation 16.0%; one wire breakage within 8 hours of continuous drawing, wire breakage rate 0.42%; no oxidation defects on the surface, and stable mechanical properties.

[0048] Comparative Example 1

[0049] Raw material pretreatment and extrusion: BCu76AgP solder blanks with the same composition and initial size as in Example 2 were selected. The surface cleaning method and extrusion parameters were the same as in Example 2 to obtain an extruded blank with a diameter of 1.95 mm.

[0050] Wire drawing process: No extrusion parameter range determination is performed, and fixed wire drawing parameters are directly adopted: single-pass diameter reduction ratio of 18%, intermediate annealing trigger rule is triggered after every 5 wire drawing passes, 7 wire drawing passes, wire drawing speed of 10m / min; intermediate annealing parameters are the same as in Example 2, and the wire is drawn to a diameter of 0.6mm;

[0051] Post-processing: Completely consistent with Example 2.

[0052] Finished product inspection results: diameter 0.6mm, dimensional tolerance ±0.045mm; tensile strength 330MPa, elongation 12.5%; 8 wire breaks within 8 hours of continuous drawing, wire breakage rate 3.8%; a small number of oxide spots on the surface, dimensional accuracy and mechanical properties are significantly worse than those of Example 2, highlighting the core role of interval determination in process adaptation.

[0053] Comparative Example 2

[0054] Raw material pretreatment and extrusion: BCu76AgP solder blanks with the same composition and initial size as in Example 1 were selected. The surface cleaning method and extrusion parameters were the same as in Example 1 to obtain an extruded blank with a diameter of 1.48 mm.

[0055] Extrusion parameter range determination: consistent with Example 1, classified into the first range.

[0056] Wire drawing process: After the interval determination, no differential reduction was matched. The single-pass reduction ratio was uniformly set to 18%. The intermediate annealing triggering rules, annealing parameters, 8 wire drawing passes, and speed of 8m / min were all consistent with those in Example 1. The wire was drawn to a diameter of 0.6mm.

[0057] Post-processing: Completely consistent with Example 1.

[0058] Finished product inspection results: diameter 0.6mm, dimensional tolerance ±0.042mm; tensile strength 335MPa, elongation 12.2%; 10 wire breaks within 8 hours of continuous drawing, wire breakage rate 4.7%; local cracks appeared on the surface. The wire breakage rate surged due to the mismatch between the reduction ratio and the plasticity of the first section billet, highlighting the necessity of differentiated reduction.

[0059] Comparative Example 3

[0060] Raw material pretreatment and extrusion: BCu76AgP solder blanks with the same composition and initial size as in Example 3 were selected. The surface cleaning method and extrusion parameters were the same as in Example 3, and an extruded blank with a diameter of 2.17 mm was obtained.

[0061] Determination of extrusion parameter range: Consistent with Example 3, classified into the third range;

[0062] Wire drawing process: After the interval determination, the matching annealing rules were not matched. The "annealing every 5 passes" was uniformly set. The single pass diameter reduction ratio, annealing parameters, 6 wire drawing passes, and speed of 12m / min were all consistent with those in Example 3. The wire was drawn to a diameter of 0.7mm.

[0063] Post-processing: Completely consistent with Example 3.

[0064] Finished product inspection results: diameter 0.7mm, dimensional tolerance ±0.038mm; tensile strength 332MPa, elongation 12.0%; 9 wire breaks within 8 hours of continuous drawing, wire breakage rate 4.3%; surface oxidation color difference, due to untimely annealing leading to accumulated work hardening, resulting in decreased mechanical properties and surface quality, highlighting the technical advantages of the range-adaptive annealing rule.

[0065] Comparative Example 4

[0066] Raw material pretreatment and extrusion: BCu76AgP solder blanks with the same composition and initial size as in Example 2 were selected. The surface cleaning method and extrusion parameters were the same as in Example 2, and an extruded blank with a diameter of 1.95 mm was obtained and classified into the second interval.

[0067] Wire drawing and heat treatment: The first interval wire drawing parameters are used, with a maximum diameter reduction ratio of 15% per pass. At the same time, the third interval annealing rules are adopted, and annealing is triggered after every 3 wire drawing passes. There are 7 wire drawing passes and a wire drawing speed of 10m / min. The intermediate annealing parameters are the same as in Example 2, and the wire is drawn to a diameter of 0.6mm.

[0068] Post-processing: Completely consistent with Example 2.

[0069] Finished product inspection results: diameter 0.6mm, dimensional tolerance ±0.048mm; tensile strength 308MPa, elongation 10.9%; 12 wire breaks within 8 hours of continuous drawing, wire breakage rate 5.5%; obvious oxidation cracks on the surface, and significant deterioration in processing stability and product performance.

[0070] Performance testing method for ultrafine welding wire used for brazing mobile phone components: The tensile strength and elongation of the brazed joint are tested according to the requirements of GB / T 11363-2008 "Test Method for Strength of Brazed Joints", with a shear rate of 1 mm / min.

[0071] As can be seen from the above embodiments and comparative examples, the present invention determines the differentiated wire drawing path matching process system by extrusion parameter range. Compared with the comparative example, the embodiments have significant advantages. First, the wire breakage rate is greatly reduced, with the embodiment having a wire breakage rate of only 0.35%-0.42%, while the comparative example has a wire breakage rate as high as 3.8%-5.5%, solving the core pain point of high wire breakage rate in the prior art. Second, the dimensional accuracy is significantly improved, with the dimensions of the embodiments conforming to GB / T 25775-2010 "Technical Conditions for the Supply of Welding Materials: Product Type, Dimensions, Tolerances and Markings" specifies requirements for solid welding wire with a diameter of 0.6mm (+0.01 / -0.03), with tolerances controlled within ±0.01mm, and tolerances in the comparative examples within ±0.038mm-±0.048mm. Mechanical properties are also more stable; the example exhibits a tensile strength ≥358MPa and elongation ≥15.5%, while the comparative examples show a tensile strength ≤335MPa and elongation ≤12.5%. Finally, surface quality is superior; the example has no surface defects, while the comparative examples exhibit oxidation, cracks, and other problems.

[0072] In particular, Comparative Example 4 verified the necessity of synergy. Only a single step met the requirements, and the extrusion-drawing-heat treatment parameters were mismatched. Its wire breakage rate (5.5%) and surface quality (obvious oxidation cracks) were inferior to other comparative examples. This fully demonstrates that the present invention is not an improvement of a single parameter, but rather achieves excellent technical effects through the synergistic adaptation of extrusion-drawing-heat treatment.

[0073] Although embodiments of this application have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A manufacturing process for ultrafine welding wire for brazing of cell phone components, characterized by, Includes the following steps: Step S1, Raw material pretreatment and extrusion: The surface of the solder blank is cleaned, and then hot extrusion is performed under the set extrusion parameters to obtain the extruded blank; The extrusion parameters include extrusion ratio, extrusion temperature and extrusion speed, wherein the extrusion ratio is the ratio of the cross-sectional area of ​​the billet before extrusion to the cross-sectional area of ​​the billet after extrusion, and the extrusion speed is controlled at 5-10 mm / s; Step S2, Extrusion Parameter Range Determination: Obtain the actual extrusion ratio and extrusion temperature from Step S1, and classify the extruded billet into the corresponding extrusion parameter range according to the preset threshold range; the extrusion parameter range includes at least a first range, a second range, and a third range; Step S3, Wire drawing path parameter matching: Based on the extrusion parameter range to which the extruded billet belongs, call the differentiated wire drawing path parameter combination that is pre-set for that range; the wire drawing path parameter combination includes at least the maximum reduction ratio per pass and the intermediate annealing trigger rule; Step S4, Differentiated wire drawing process: The extruded billet is fed into the wire drawing equipment, and multiple wire drawing passes are performed according to the matching wire drawing path parameter combination. During this process, intermediate annealing is performed according to the intermediate annealing triggering rule until the wire diameter reaches the requirement of 0.6mm solid wire. Step S5, Post-processing: The drawn welding wire is subjected to cooling and surface treatment in sequence to obtain the finished ultrafine welding wire.

2. The manufacturing process of claim 1, wherein, The solder blank is BCu76AgP solder, and its chemical composition by mass percentage is: Cu 75-77%, Ag 1.5-2.5%, P 5.5-6.5%, with the balance being unavoidable impurities.

3. The manufacturing process of claim 1, wherein, The first range is defined as: extrusion temperature 450℃-500℃, extrusion ratio 2:1-3:1; the second range is defined as: extrusion temperature 500℃-550℃, extrusion ratio 3:1-5:1; the third range is defined as: extrusion temperature 550℃-600℃, extrusion ratio 5:1-6:

1.

4. The manufacturing process of claim 1, wherein, In step S1, the selection criteria for the extrusion ratio are as follows: when the initial cross-sectional diameter of the solder blank is 3mm-6mm, the extrusion ratio is set to 3:1-6:1; when the initial cross-sectional diameter of the solder blank is less than 3mm, the extrusion ratio is set to 2:1-4:

1.

5. The manufacturing process of claim 1, wherein, In step S3, the maximum reduction ratio per single pass for each interval is as follows: First interval: not exceeding 15%; Second interval: not exceeding 18%; Third interval: not exceeding 22%.

6. The manufacturing process of claim 1, wherein, In step S3, the intermediate annealing trigger rules for each interval are as follows: intermediate annealing is triggered when the cumulative diameter reduction reaches 50% in the first interval; intermediate annealing is triggered after every 4-5 passes of wire drawing in the second interval; intermediate annealing is triggered after every 2-3 passes of wire drawing in the third interval.

7. The manufacturing process of claim 6, wherein, The intermediate annealing is carried out under a protective atmosphere, with an annealing temperature of 300℃-450℃ and an annealing time of 5–15 min.

8. The manufacturing process of claim 1, wherein, The cooling process in step S5 uses water bath cooling with a water temperature of 20℃-30℃; the surface treatment uses pickling or protective atmosphere annealing.

9. An ultrafine welding wire for soldering of cell phone components, characterized in that, Made from BCu76AgP solder and prepared by the manufacturing process as described in any one of claims 1 to 8, the ultrafine welding wire has a diameter of 0.6 mm, meeting the requirements of a solid welding wire.

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