Process for preparing high-density phosphor copper balls for electronic connection from scrap copper

Abstract

The invention relates to a process for preparing high-density phosphor copper balls for electronic connection from scrap copper, and belongs to the field of non-ferrous metal processing. The scrap copper obtained after crushing and magnetic separation is put into a sulfuric acid solution to be subjected to acid pickling and then put into a medium-frequency induction furnace to be smelted; a refining agent is added into the smelted copper liquid for refining; adding a phosphorus-copper master alloy, adjusting the phosphorus content, and continuously casting through an up-drawing continuous casting machine to obtain a phosphorus-copper rod; the phosphor copper rod is fed into a cold header to be subjected to cold heading to form a ball blank; putting the ball blank into an annealing furnace, uniformly covering the surface of the ball blank with a mixed solution of a titanate-carboxylate composite densifier and absolute ethyl alcohol through atomization spraying, and carrying out annealing treatment, polishing, cleaning and drying to obtain a phosphor copper ball; the titanate-carboxylate composite compacting agent is prepared from triethyl citrate, 1, 1 '-bis (diphenylphosphine) ferrocene, tetraisopropyl titanate, ethanol and p-toluenesulfonic acid; the phosphor copper ball prepared by the method meets the requirements in components, is high in density, and can meet the use requirements of electronic connection.

Description

Technical Field

[0001] This invention relates to the field of non-ferrous metal processing, and in particular to a process for preparing high-density phosphor bronze balls from scrap copper for electronic bonding. Background Technology

[0002] In the field of electronic bonding, phosphor bronze balls are an important anode material, and their quality plays a crucial role in the electroplating effect and the reliability of electronic connections. Traditional phosphor bronze balls are mostly made from electrolytic copper, which is costly. With the rapid development of the electronics industry, the amount of scrap copper generated is increasing daily, making the efficient utilization of scrap copper to prepare high-quality phosphor bronze balls a research hotspot.

[0003] Chinese patent CN101698271A discloses a high-efficiency, high-density phosphor bronze ball processing method, which uses a continuous extruder to extrude raw phosphor bronze rods, resulting in a fine-grained state both inside and outside the phosphor bronze rods.

[0004] Chinese Patent CN108890221B discloses a method for producing phosphor bronze balls, comprising the following steps: Preheating phosphor bronze rods crystallized using the upward continuous casting method in a preheating furnace at a temperature of 420℃-440℃; Ball rolling: removing the phosphor bronze rods from the preheating furnace and placing them on a spiral die to roll them into multiple phosphor bronze balls; Polishing: placing the phosphor bronze balls, abrasive, and brightener into a tumbler polishing machine and adding water to the tumbler; polishing time: 15-25 minutes; Air drying and washing: washing the polished phosphor bronze balls in a water washing and air drying machine for 10-15 minutes; Packaging and weighing: placing the packaging box on an electronic scale and gradually adding qualified phosphor bronze balls until the electronic scale displays 25±0.02kg; sealing the packaging box and then securing it with strapping.

[0005] In the existing technology, the preparation of phosphor bronze balls using waste copper has problems such as incomplete removal of impurities and low density, which leads to uneven dissolution of the prepared phosphor bronze balls during the electroplating process and affects the quality of electronic connection. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a process for preparing high-density phosphor bronze spheres from scrap copper for electronic bonding, the operation steps of which are as follows:

[0007] S1 waste copper pretreatment: First, sort the waste copper to remove large pieces of plastic and rubber impurities; then crush it to a particle size of 5-10mm and remove ferromagnetic impurities by magnetic separation; then put the crushed waste copper into sulfuric acid solution for acid washing for 10-30 minutes to remove surface oxides, rinse it with clean water after acid washing and dry it.

[0008] S2 smelting: The pretreated scrap copper is put into a medium-frequency induction furnace and heated to smelt. During the smelting process, a charcoal layer with a thickness of 50-100mm is covered on the surface of the copper liquid to isolate it from the air and prevent the copper liquid from oxidizing.

[0009] S3 Refining: Add 0.1-0.5 parts by weight of refining agent to 70-100 parts by weight of molten copper, stir to ensure that the refining agent is in full contact with the molten copper, then let it stand for 30-60 minutes and remove the surface slag.

[0010] S4 phosphorus content adjustment: Add phosphorus copper master alloy and stir evenly to make the phosphorus mass fraction in the copper liquid 0.03%-0.07%;

[0011] S5 continuous casting: The copper liquid with adjusted phosphorus content is continuously cast through an upward continuous casting machine, with a cooling rate of 5-10℃ / s, to produce phosphor bronze rods with a diameter of 8-12mm.

[0012] S6 Cold Heading: The phosphor bronze rod is fed into a cold heading machine and cold-headed into a ball blank;

[0013] S7 Annealing:

[0014] Place the billet into the annealing furnace, heat it to 200-300℃, and hold it for 20-30 minutes;

[0015] A mixed solution was prepared by diluting the titanate-carboxylic acid ester composite densifier with anhydrous ethanol at a mass ratio of 1:5-10. 0.14%-0.3% of the mixed solution by mass of the blank was then uniformly covered on the surface of the blank by atomization spraying at a spraying rate of 5-10 mL / min to ensure that the densifier completely wetted the blank.

[0016] Continue heating to 400-600℃, hold for 1-3 hours, then cool to room temperature with the furnace;

[0017] S8 Surface Treatment: Polish the annealed ball blank for 15-30 minutes, rinse with clean water, and dry at 80-100℃ to obtain the finished phosphor bronze ball;

[0018] The preparation method of the titanate-carboxylic acid ester composite densifier is as follows, according to parts by mass:

[0019] H1: Add 10-15 parts of triethyl citrate, 0.1-0.5 parts of 1,1'-bis(diphenylphosphine)ferrocene, and 6-10 parts of tetraisopropyl titanate to 35-45 parts of anhydrous ethanol and mix under nitrogen protection.

[0020] H2: Add 0.5-1 part of p-toluenesulfonic acid, stir and react at 70-80℃ for 4-6 hours, and then rotary evaporate to obtain the composite densifier.

[0021] In some embodiments, the mass percentage of the S1 sulfuric acid solution is 10-20%.

[0022] In some embodiments, the S2 melting temperature is 1100-1300℃.

[0023] In some embodiments, the refining agent is a mixture of borax and sodium carbonate in a mass ratio of 2:1.

[0024] In some embodiments, the stirring rate of S3 is 200-300 r / min, and the time is 10-15 minutes.

[0025] In some embodiments, the phosphorus content in the phosphorus-copper master alloy of S4 is 10-15% by mass.

[0026] In some embodiments, the pressure of the S6 cold heading machine is 300-500 MPa.

[0027] Reaction mechanism:

[0028] The titanate-carboxylic acid ester composite densifier added during the annealing stage exhibits a synergistic effect at 400-600℃:

[0029] The carboxyl group (-COOH) derived from triethyl citrate is rapidly adsorbed on the surface and internal micropore walls of the spherical blank at low temperature, inhibiting the abnormal growth of copper grains during the annealing process;

[0030] The titanium oxide bond (-Ti-O-) slowly hydrolyzes at the annealing temperature to generate nano-TiO2 particles, which gradually fill the micropores formed by cold heading.

[0031] The phosphine ligands of 1,1'-bis(diphenylphosphine)ferrocene stabilize the dispersibility of nano-TiO2 through their conjugated structure, preventing agglomeration, while enhancing the binding force between the carboxyl group and the copper matrix, forming a synergistic system of "adsorption-crystal control-nanofilling-stable dispersion", which significantly improves the density.

[0032] Technical effects:

[0033] 1. Adding a densifier at a low temperature during the annealing stage can completely avoid the problem of high-temperature decomposition. Its active ingredients react fully at 400-600℃, so that the density of the phosphor bronze balls meets the requirements of material density for electronic connection.

[0034] 2. The atomized spraying method ensures that the densifier evenly covers the blank, and with the protection of nitrogen atmosphere, it reduces surface oxidation, improves the surface smoothness of the finished product, and has better dissolution uniformity during the electroplating process.

[0035] 3. The filling effect of nano-TiO2 and the stress relief of annealing work together to improve the mechanical properties of phosphor bronze balls, enhance their crack resistance after cold heading, and reduce the scrap rate.

[0036] 4. The refined grains and the filling effect of nano-TiO2 jointly enhance the mechanical properties of the material, improve the crack resistance of phosphor bronze balls during cold heading, reduce the scrap rate during processing, and improve the surface finish of the finished product, meeting the stringent requirements of electronic packaging for dimensional accuracy and appearance quality. Detailed Implementation

[0037] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description is provided in conjunction with embodiments and comparative examples:

[0038] 1. Composition analysis: Inductively coupled plasma optical emission spectrometry (ICP-OES) was used to analyze the content of copper, phosphorus and impurity elements in the finished phosphor bronze balls.

[0039] 2. Density test: The actual density of the phosphor bronze balls is measured by the water displacement method, and the density is calculated by comparing it with the theoretical density; Density = (Actual density / Theoretical density) × 100%.

[0040] Example 1

[0041] A process for preparing high-density phosphor bronze spheres from scrap copper for electronic bonding includes the following steps:

[0042] S1 waste copper pretreatment: First, the waste copper is sorted to remove large pieces of plastic and rubber impurities; then it is crushed to a particle size of 10mm and ferromagnetic impurities are removed by magnetic separation; then the crushed waste copper is placed in sulfuric acid solution for acid washing for 10 minutes to remove surface oxides, rinsed with clean water after acid washing and dried.

[0043] S2 smelting: The pre-treated scrap copper is put into a medium-frequency induction furnace and heated for smelting; during the smelting process, a 50mm thick layer of charcoal is placed on the surface of the molten copper to isolate it from the air and prevent the molten copper from oxidizing.

[0044] S3 Refining: Add 0.1g of refining agent to 70g of molten copper, stir to ensure that the refining agent is fully in contact with the molten copper, then let it stand for 30 minutes and remove the surface slag.

[0045] S4 phosphorus content adjustment: Add phosphorus copper master alloy and stir evenly to make the phosphorus mass fraction in the copper liquid 0.03%;

[0046] S5 Continuous Casting: The copper liquid with adjusted phosphorus content is continuously cast through an upward continuous casting machine with a cooling rate of 5℃ / s to produce a phosphor bronze rod with a diameter of 8mm.

[0047] S6 Cold Heading: The phosphor bronze rod is fed into a cold heading machine and cold-headed into a ball blank;

[0048] S7 Annealing:

[0049] Place the billet into the annealing furnace, heat it to 200℃, and hold it for 20 minutes;

[0050] A mixed solution was prepared by diluting the titanate-carboxylic acid ester composite densifier with anhydrous ethanol at a mass ratio of 1:5. The mixed solution, at a mass ratio of 0.14% of the billet, was then sprayed evenly over the surface of the billet by atomization at a spraying rate of 5 mL / min to ensure that the densifier completely wetted the billet.

[0051] Continue heating to 400℃, hold at that temperature for 1 hour, then cool to room temperature with the furnace.

[0052] S8 Surface Treatment: Polish the annealed ball blank for 15 minutes, rinse with water and dry at 80℃ to obtain the finished phosphor bronze ball;

[0053] The preparation method of the titanate-carboxylic acid ester composite densifier is as follows:

[0054] H1: Add 10g of triethyl citrate (CAS No.: 77-93-0), 0.1g of 1,1'-bis(diphenylphosphine)ferrocene, and 6g of tetraisopropyl titanate (CAS No.: 546-68-9) to 35g of anhydrous ethanol and mix under nitrogen protection;

[0055] H2: Add 0.5g of p-toluenesulfonic acid, stir and react at 70℃ for 4 hours, then evaporate by rotary evaporation to obtain a titanate-carboxylic acid ester composite densifier.

[0056] The S1 sulfuric acid solution has a mass percentage of 10%.

[0057] The S2 melting temperature is 1100℃.

[0058] The refining agent is a mixture of borax and sodium carbonate in a mass ratio of 2:1.

[0059] The stirring rate of S3 is 200 r / min, and the stirring time is 10 minutes.

[0060] The phosphorus content in the S4 phosphorus copper master alloy is 10% by mass.

[0061] The pressure of the S6 cold heading machine is 300 MPa.

[0062] Example 2

[0063] A process for preparing high-density phosphor bronze spheres from scrap copper for electronic bonding includes the following steps:

[0064] S1 waste copper pretreatment: First, the waste copper is sorted to remove large pieces of plastic and rubber impurities; then it is crushed to a particle size of 8mm and ferromagnetic impurities are removed by magnetic separation; then the crushed waste copper is placed in sulfuric acid solution for acid washing for 15 minutes to remove surface oxides, rinsed with clean water after acid washing and dried.

[0065] S2 smelting: The pre-treated scrap copper is put into a medium-frequency induction furnace and heated for smelting; during the smelting process, a 60mm thick layer of charcoal is placed on the surface of the molten copper to isolate it from the air and prevent the molten copper from oxidizing.

[0066] S3 Refining: Add 0.2g of refining agent to 80g of molten copper, stir to ensure that the refining agent is fully in contact with the molten copper, then let it stand for 40 minutes and remove the surface slag.

[0067] S4 phosphorus content adjustment: Add phosphorus copper master alloy and stir evenly to make the phosphorus mass fraction in the copper liquid 0.04%;

[0068] S5 Continuous Casting: The copper liquid with adjusted phosphorus content is continuously cast through an upward continuous casting machine with a cooling rate of 6℃ / s to produce a phosphorus copper rod with a diameter of 9mm.

[0069] S6 Cold Heading: The phosphor bronze rod is fed into a cold heading machine and cold-headed into a ball blank;

[0070] S7 Annealing:

[0071] Place the billet into the annealing furnace, heat it to 240℃, and hold it for 25 minutes;

[0072] After diluting the titanate-carboxylic acid ester composite densifier with anhydrous ethanol at a mass ratio of 1:6, the mixed solution at a mass ratio of 0.2% of the billet was uniformly covered on the surface of the billet by atomization spraying at a spraying rate of 6 mL / min to ensure that the densifier completely wetted the billet.

[0073] Continue heating to 450℃, hold at that temperature for 2 hours, then cool to room temperature with the furnace.

[0074] S8 Surface Treatment: Polish the annealed ball blank for 20 minutes, rinse with water, and dry at 85℃ to obtain the finished phosphor bronze ball;

[0075] The preparation method of the titanate-carboxylic acid ester composite densifier is as follows:

[0076] H1: Add 12g of triethyl citrate (CAS No.: 77-93-0), 0.2g of 1,1'-bis(diphenylphosphine)ferrocene, and 7g of tetraisopropyl titanate (CAS No.: 546-68-9) to 38g of anhydrous ethanol and mix under nitrogen protection;

[0077] H2: Add 0.6g of p-toluenesulfonic acid, stir and react at 75℃ for 5 hours, then evaporate by rotary evaporation to obtain a titanate-carboxylic acid ester composite densifier.

[0078] The S1 sulfuric acid solution has a mass percentage of 15%.

[0079] The S2 melting temperature is 1150℃.

[0080] The refining agent is a mixture of borax and sodium carbonate in a mass ratio of 2:1.

[0081] The stirring rate of S3 is 250 r / min, and the stirring time is 10 minutes.

[0082] The phosphorus content in the S4 phosphorus copper master alloy is 10% by mass.

[0083] The pressure of the S6 cold heading machine is 400 MPa.

[0084] Example 3

[0085] A process for preparing high-density phosphor bronze spheres from scrap copper for electronic bonding includes the following steps:

[0086] S1 waste copper pretreatment: First, the waste copper is sorted to remove large pieces of plastic and rubber impurities; then it is crushed to a particle size of 6mm and ferromagnetic impurities are removed by magnetic separation; then the crushed waste copper is placed in sulfuric acid solution for acid washing for 25 minutes to remove surface oxides, rinsed with clean water after acid washing and dried.

[0087] S2 smelting: The pre-treated scrap copper is put into a medium-frequency induction furnace and heated for smelting; during the smelting process, a charcoal layer with a thickness of 90mm is covered on the surface of the copper liquid to isolate it from the air and prevent the copper liquid from oxidizing.

[0088] S3 Refining: Add 0.4g of refining agent to 90g of molten copper, stir to ensure that the refining agent is in full contact with the molten copper, then let it stand for 50 minutes and remove the surface slag.

[0089] S4 phosphorus content adjustment: Add phosphorus copper master alloy and stir evenly to make the phosphorus mass fraction in the copper liquid 0.06%;

[0090] S5 Continuous Casting: The copper liquid with adjusted phosphorus content is continuously cast through an upward continuous casting machine with a cooling rate of 8℃ / s to produce a phosphor bronze rod with a diameter of 11mm.

[0091] S6 Cold Heading: The phosphor bronze rod is fed into a cold heading machine and cold-headed into a ball blank;

[0092] S7 Annealing:

[0093] Place the billet into the annealing furnace, heat it to 280℃, and hold it for 25 minutes;

[0094] A mixed solution was prepared by diluting the titanate-carboxylic acid ester composite densifier with anhydrous ethanol at a ratio of 1:8. The mixed solution, at a ratio of 0.25% of the billet mass, was then sprayed evenly over the surface of the billet by atomization at a spraying rate of 8 mL / min to ensure that the densifier completely wetted the billet.

[0095] Continue heating to 550℃, hold at that temperature for 2 hours, then cool to room temperature with the furnace.

[0096] S8 Surface Treatment: Polish the annealed ball blank for 25 minutes, rinse with water, and dry at 95℃ to obtain the finished phosphor bronze ball;

[0097] The preparation method of the titanate-carboxylic acid ester composite densifier is as follows:

[0098] H1: Add 14g of triethyl citrate (CAS No.: 77-93-0), 0.4g of 1,1'-bis(diphenylphosphine)ferrocene, and 9g of tetraisopropyl titanate (CAS No.: 546-68-9) to 43g of anhydrous ethanol and mix under nitrogen protection;

[0099] H2: Add 0.8g of p-toluenesulfonic acid, stir and react at 75℃ for 5 hours, then evaporate by rotary evaporation to obtain a titanate-carboxylic acid ester composite densifier.

[0100] The S1 sulfuric acid solution has a mass percentage of 15%.

[0101] The S2 melting temperature is 1250℃.

[0102] The refining agent is a mixture of borax and sodium carbonate in a mass ratio of 2:1.

[0103] The stirring rate of S3 is 250 r / min, and the stirring time is 15 minutes.

[0104] The phosphorus content in the S4 phosphorus copper master alloy is 15% by mass.

[0105] The pressure of the S6 cold heading machine is 400 MPa.

[0106] Example 4

[0107] A process for preparing high-density phosphor bronze spheres from scrap copper for electronic bonding includes the following steps:

[0108] S1 waste copper pretreatment: First, the waste copper is sorted to remove large pieces of plastic and rubber impurities; then it is crushed to a particle size of 5mm and ferromagnetic impurities are removed by magnetic separation; then the crushed waste copper is placed in sulfuric acid solution for acid washing for 30 minutes to remove surface oxides, rinsed with clean water after acid washing and dried.

[0109] S2 smelting: The pre-treated scrap copper is put into a medium-frequency induction furnace and heated for smelting; during the smelting process, a 100mm thick layer of charcoal is placed on the surface of the molten copper to isolate it from the air and prevent the molten copper from oxidizing.

[0110] S3 Refining: Add 0.5g of refining agent to 100g of molten copper, stir to ensure that the refining agent is fully in contact with the molten copper, then let it stand for 60 minutes and remove the surface slag.

[0111] S4 phosphorus content adjustment: Add phosphorus copper master alloy and stir evenly to make the phosphorus mass fraction in the copper liquid 0.07%;

[0112] S5 Continuous Casting: The copper liquid with adjusted phosphorus content is continuously cast through an upward continuous casting machine with a cooling rate of 10℃ / s to produce a phosphor bronze rod with a diameter of 12mm.

[0113] S6 Cold Heading: The phosphor bronze rod is fed into a cold heading machine and cold-headed into a ball blank;

[0114] S7 Annealing:

[0115] Place the billet into the annealing furnace, heat it to 300℃, and hold it for 30 minutes;

[0116] A mixed solution was prepared by diluting the titanate-carboxylic acid ester composite densifier with anhydrous ethanol at a ratio of 1:10. The mixed solution, at a ratio of 0.3% of the billet mass, was then uniformly applied to the surface of the billet by atomization spraying at a rate of 10 mL / min to ensure that the densifier completely wetted the billet.

[0117] Continue heating to 600℃, hold at that temperature for 3 hours, then cool to room temperature with the furnace.

[0118] S8 Surface Treatment: Polish the annealed ball blank for 30 minutes, rinse with water and dry at 100℃ to obtain the finished phosphor bronze ball;

[0119] The preparation method of the titanate-carboxylic acid ester composite densifier is as follows:

[0120] H1: Add 15g of triethyl citrate (CAS No.: 77-93-0), 0.5g of 1,1'-bis(diphenylphosphine)ferrocene, and 10g of tetraisopropyl titanate (CAS No.: 546-68-9) to 45g of anhydrous ethanol and mix under nitrogen protection;

[0121] H2: Add 1g of p-toluenesulfonic acid, stir and react at 80℃ for 6 hours, then evaporate by rotary evaporation to obtain a titanate-carboxylic acid ester composite densifier.

[0122] The S1 sulfuric acid solution has a mass percentage of 20%.

[0123] The S2 melting temperature is 1300℃.

[0124] The refining agent is a mixture of borax and sodium carbonate in a mass ratio of 2:1.

[0125] The stirring rate of S3 is 300 r / min, and the stirring time is 15 minutes.

[0126] The phosphorus content in the S4 phosphorus copper master alloy is 15% by mass.

[0127] The pressure of the S6 cold heading machine is 500 MPa.

[0128] Comparative Example 1

[0129] A process for preparing high-density phosphor bronze spheres from scrap copper for electronic bonding includes the following steps:

[0130] S1 waste copper pretreatment: First, the waste copper is sorted to remove large pieces of plastic and rubber impurities; then it is crushed to a particle size of 10mm and ferromagnetic impurities are removed by magnetic separation; then the crushed waste copper is placed in sulfuric acid solution for acid washing for 10 minutes to remove surface oxides, rinsed with clean water after acid washing and dried.

[0131] S2 smelting: The pre-treated scrap copper is put into a medium-frequency induction furnace and heated for smelting; during the smelting process, a 50mm thick layer of charcoal is placed on the surface of the molten copper to isolate it from the air and prevent the molten copper from oxidizing.

[0132] S3 Refining: Add 0.1g of refining agent to 70g of molten copper, stir to ensure that the refining agent is fully in contact with the molten copper, then let it stand for 30 minutes and remove the surface slag.

[0133] S4 phosphorus content adjustment: Add phosphorus copper master alloy and stir evenly to make the phosphorus mass fraction in the copper liquid 0.03%;

[0134] S5 Continuous Casting: The copper liquid with adjusted phosphorus content is continuously cast through an upward continuous casting machine with a cooling rate of 5℃ / s to produce a phosphor bronze rod with a diameter of 8mm.

[0135] S6 Cold Heading: The phosphor bronze rod is fed into a cold heading machine and cold-headed into a ball blank;

[0136] S7 Annealing: Place the billet in an annealing furnace, heat it to 400℃, hold it at that temperature for 1 hour, and then cool it to room temperature in the furnace.

[0137] S8 Surface Treatment: Polish the annealed ball blank for 15 minutes, rinse with water and dry at 80℃ to obtain the finished phosphor bronze ball;

[0138] The S1 sulfuric acid solution has a mass percentage of 10%.

[0139] The S2 melting temperature is 1100℃.

[0140] The refining agent is a mixture of borax and sodium carbonate in a mass ratio of 2:1.

[0141] The stirring rate of S3 is 200 r / min, and the stirring time is 10 minutes.

[0142] The phosphorus content in the S4 phosphorus copper master alloy is 10% by mass.

[0143] The pressure of the S6 cold heading machine is 300 MPa.

[0144] Comparative Example 2

[0145] A process for preparing high-density phosphor bronze spheres from scrap copper for electronic bonding includes the following steps:

[0146] S1 waste copper pretreatment: First, the waste copper is sorted to remove large pieces of plastic and rubber impurities; then it is crushed to a particle size of 10mm and ferromagnetic impurities are removed by magnetic separation; then the crushed waste copper is placed in sulfuric acid solution for acid washing for 10 minutes to remove surface oxides, rinsed with clean water after acid washing and dried.

[0147] S2 smelting: The pre-treated scrap copper is put into a medium-frequency induction furnace and heated for smelting; during the smelting process, a 50mm thick layer of charcoal is placed on the surface of the molten copper to isolate it from the air and prevent the molten copper from oxidizing.

[0148] S3 Refining: Add 0.1g of refining agent to 70g of molten copper, stir to ensure that the refining agent is fully in contact with the molten copper, then let it stand for 30 minutes and remove the surface slag.

[0149] S4 phosphorus content adjustment: Add phosphorus copper master alloy and stir evenly to make the phosphorus mass fraction in the copper liquid 0.03%;

[0150] S5 Continuous Casting: The copper liquid with adjusted phosphorus content is continuously cast through an upward continuous casting machine with a cooling rate of 5℃ / s to produce a phosphor bronze rod with a diameter of 8mm.

[0151] S6 Cold Heading: The phosphor bronze rod is fed into a cold heading machine and cold-headed into a ball blank;

[0152] S7 Annealing:

[0153] Place the billet into the annealing furnace, heat it to 200℃, and hold it for 20 minutes;

[0154] A mixed solution was prepared by diluting the composite densifier with anhydrous ethanol at a ratio of 1:5. The mixed solution, at a ratio of 0.14% of the billet mass, was then sprayed evenly over the surface of the billet by atomization at a spraying rate of 5 mL / min to ensure that the densifier completely wetted the billet.

[0155] Continue heating to 400℃, hold at that temperature for 1 hour, then cool to room temperature with the furnace.

[0156] S8 Surface Treatment: Polish the annealed ball blank for 15 minutes, rinse with water and dry at 80℃ to obtain the finished phosphor bronze ball;

[0157] The preparation method of the composite densifier is as follows:

[0158] H1: Add 10g of triethyl citrate (CAS No.: 77-93-0) and 6g of tetraisopropyl titanate (CAS No.: 546-68-9) to 35g of anhydrous ethanol and mix under nitrogen protection;

[0159] H2: Add 0.5g of p-toluenesulfonic acid, stir and react at 70℃ for 4 hours, then evaporate by rotary evaporation to obtain the composite densifier.

[0160] The S1 sulfuric acid solution has a mass percentage of 10%.

[0161] The S2 melting temperature is 1100℃.

[0162] The refining agent is a mixture of borax and sodium carbonate in a mass ratio of 2:1.

[0163] The stirring rate of S3 is 200 r / min, and the stirring time is 10 minutes.

[0164] The phosphorus content in the S4 phosphorus copper master alloy is 10% by mass.

[0165] The pressure of the S6 cold heading machine is 300 MPa.

[0166] Comparative Example 3

[0167] A process for preparing high-density phosphor bronze spheres from scrap copper for electronic bonding includes the following steps:

[0168] S1 waste copper pretreatment: First, the waste copper is sorted to remove large pieces of plastic and rubber impurities; then it is crushed to a particle size of 10mm and ferromagnetic impurities are removed by magnetic separation; then the crushed waste copper is placed in sulfuric acid solution for acid washing for 10 minutes to remove surface oxides, rinsed with clean water after acid washing and dried.

[0169] S2 smelting: The pre-treated scrap copper is put into a medium-frequency induction furnace and heated for smelting; during the smelting process, a 50mm thick layer of charcoal is placed on the surface of the molten copper to isolate it from the air and prevent the molten copper from oxidizing.

[0170] S3 Refining: Add 0.1g of refining agent to 70g of molten copper, stir to ensure that the refining agent is fully in contact with the molten copper, then let it stand for 30 minutes and remove the surface slag.

[0171] S4 phosphorus content adjustment: Add phosphorus copper master alloy and stir evenly to make the phosphorus mass fraction in the copper liquid 0.03%;

[0172] S5 Continuous Casting: The copper liquid with adjusted phosphorus content is continuously cast through an upward continuous casting machine with a cooling rate of 5℃ / s to produce a phosphor bronze rod with a diameter of 8mm.

[0173] S6 Cold Heading: The phosphor bronze rod is fed into a cold heading machine and cold-headed into a ball blank;

[0174] S7 Annealing:

[0175] Place the billet into the annealing furnace, heat it to 200℃, and hold it for 20 minutes;

[0176] A mixed solution was prepared by diluting the composite densifier with anhydrous ethanol at a ratio of 1:5. The mixed solution, at a ratio of 0.14% of the billet mass, was then sprayed evenly over the surface of the billet by atomization at a spraying rate of 5 mL / min to ensure that the densifier completely wetted the billet.

[0177] Continue heating to 400℃, hold at that temperature for 1 hour, then cool to room temperature with the furnace.

[0178] S8 Surface Treatment: Polish the annealed ball blank for 15 minutes, rinse with water and dry at 80℃ to obtain the finished phosphor bronze ball;

[0179] The preparation method of the composite densifier is as follows:

[0180] H1: Add 10g of triethyl citrate (CAS No.: 77-93-0) and 0.1g of 1,1'-bis(diphenylphosphine)ferrocene to 35g of anhydrous ethanol and mix under nitrogen protection;

[0181] H2: Add 0.5g of p-toluenesulfonic acid, stir and react at 70℃ for 4 hours, then evaporate by rotary evaporation to obtain the composite densifier.

[0182] The S1 sulfuric acid solution has a mass percentage of 10%.

[0183] The S2 melting temperature is 1100℃.

[0184] The refining agent is a mixture of borax and sodium carbonate in a mass ratio of 2:1.

[0185] The stirring rate of S3 is 200 r / min, and the stirring time is 10 minutes.

[0186] The phosphorus content in the S4 phosphorus copper master alloy is 10% by mass.

[0187] The pressure of the S6 cold heading machine is 300 MPa.

[0188] Table 1: Detection Experiment Data of Examples and Comparative Examples

[0189]

[0190] Based on the data analysis of the above embodiments and comparative examples, the phosphor bronze spheres prepared by the present invention meet the requirements in terms of composition and density, and can meet the requirements for electronic connection.

[0191] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A process for preparing high-density phosphor bronze spheres from scrap copper for electronic bonding, characterized in that: The operating steps are as follows: S1 waste copper pretreatment: First, sort the waste copper to remove large pieces of plastic and rubber impurities; then crush it to a particle size of 5-10mm and remove ferromagnetic impurities by magnetic separation; then put the crushed waste copper into sulfuric acid solution for acid washing for 10-30 minutes to remove surface oxides, rinse it with clean water after acid washing and dry it. S2 smelting: The pretreated scrap copper is put into a medium-frequency induction furnace and heated to smelt. During the smelting process, a charcoal layer with a thickness of 50-100mm is covered on the surface of the copper liquid to isolate it from the air and prevent the copper liquid from oxidizing. S3 Refining: Add 0.1-0.5 parts by weight of refining agent to 70-100 parts by weight of molten copper, stir to ensure that the refining agent is in full contact with the molten copper, then let it stand for 30-60 minutes and remove the surface slag. S4 phosphorus content adjustment: Add phosphorus copper master alloy and stir evenly to make the phosphorus mass fraction in the copper liquid 0.03%-0.07%; S5 continuous casting: The copper liquid with adjusted phosphorus content is continuously cast through an upward continuous casting machine, with a cooling rate of 5-10℃ / s, to produce phosphor bronze rods with a diameter of 8-12mm. S6 Cold Heading: The phosphor bronze rod is fed into a cold heading machine and cold-headed into a ball blank; S7 Annealing: Place the billet into the annealing furnace, heat it to 200-300℃, and hold it for 20-30 minutes; A mixed solution was prepared by diluting the titanate-carboxylic acid ester composite densifier with anhydrous ethanol at a mass ratio of 1:5-10. 0.14%-0.3% of the mixed solution by mass of the blank was then uniformly covered on the surface of the blank by atomization spraying at a spraying rate of 5-10 mL / min to ensure that the densifier completely wetted the blank. Continue heating to 400-600℃, hold for 1-3 hours, then cool to room temperature with the furnace; S8 Surface Treatment: Polish the annealed ball blank for 15-30 minutes, rinse with clean water, and dry at 80-100℃ to obtain the finished phosphor bronze ball; The preparation method of the titanate-carboxylic acid ester composite densifier is as follows, according to parts by mass: H1: Add 10-15 parts of triethyl citrate, 0.1-0.5 parts of 1,1'-bis(diphenylphosphine)ferrocene, and 6-10 parts of tetraisopropyl titanate to 35-45 parts of anhydrous ethanol and mix under nitrogen protection. H2: Add 0.5-1 part of p-toluenesulfonic acid, stir and react at 70-80℃ for 4-6 hours, and then rotary evaporate to obtain the composite densifier.

2. The process for preparing high-density phosphor bronze balls from scrap copper for electronic bonding according to claim 1, characterized in that: The mass percentage of the S1 sulfuric acid solution is 10-20%.

3. The process for preparing high-density phosphor bronze balls from scrap copper for electronic bonding according to claim 1, characterized in that: The S2 melting temperature is 1100-1300℃.

4. The process for preparing high-density phosphor bronze balls from scrap copper for electronic bonding according to claim 1, characterized in that: The refining agent is a mixture of borax and sodium carbonate in a mass ratio of 2:

1.

5. The process for preparing high-density phosphor bronze balls from scrap copper for electronic bonding according to claim 1, characterized in that: The stirring rate of S3 is 200-300 r / min, and the stirring time is 10-15 minutes.

6. The process for preparing high-density phosphor bronze balls from scrap copper for electronic interconnection according to claim 1, characterized in that: The phosphorus content in the S4 phosphorus copper master alloy is 10-15% by mass.

7. The process for preparing high-density phosphor bronze balls from scrap copper for electronic bonding according to claim 1, characterized in that: The pressure of the S6 cold heading machine is 300-500 MPa.

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