Halogen-free environment-friendly flux and preparation method thereof
By using halogen-free environmentally friendly flux in the hot-dip tin plating process of copper wire, a protective film is formed using succinic acid, triethanolamine, and modified nanomaterials. This solves the problems of high corrosivity, smoke generation, and insufficient wettability of traditional fluxes, achieving high-efficiency, environmentally friendly plating quality and production efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- YINGTAN ZHONGXIN INTO COPPER CO LTD
- Filing Date
- 2026-04-17
- Publication Date
- 2026-06-12
AI Technical Summary
Existing fluxes have problems such as high corrosivity, smoke generation, insufficient wettability, and poor oxidation resistance in the hot-dip tin plating process of copper wire, which affect the plating quality and production efficiency.
It uses a halogen-free environmentally friendly flux containing succinic acid, triethanolamine, benzotriazole, silicone leveling agent and modified nanomaterials. By forming a protective film and uniformly coating the copper wire surface, it promotes the spread of molten solder, prevents oxidation and brittleness, and improves wettability.
It achieves smoke-free operation at high temperatures, bright and uniform coating, no black spots on the copper wire surface, improves coating adhesion and long-term reliability, and reduces equipment corrosion risk.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of flux technology, specifically to a halogen-free environmentally friendly flux and its preparation method. Background Technology
[0002] Hot-dip tin plating of copper wire is a common wire processing technology that aims to form a dense, bright, and continuous tin plating layer on the surface of copper wire. This process can significantly improve the corrosion resistance, solderability, and electrical connection stability of copper wire, and prevent copper oxidation and migration. In this process, flux is a key auxiliary material that affects the plating quality, production efficiency, and cost.
[0003] On a continuous high-speed hot-dip tin-plating production line, copper wires need to complete flux coating, preheating, tin immersion and cooling in a short time. This places stringent requirements on the flux: (1) It must effectively remove the oxide film continuously generated on the surface of the copper wire within a short preheating time; (2) It should promote the rapid and uniform spread of molten tin on the clean surface of the copper wire to form a continuous plating layer and prevent missed plating and tin nodules; (3) It should not undergo violent decomposition or carbonization at the high temperature of preheating and tin immersion, so as to avoid the generation of smoke and residues that affect the brightness of the plating layer and the cleanliness of the equipment; (4) It should protect the cleaned copper wires from secondary oxidation before entering the tin pot; (5) There should be no harmful smoke during the production process, and the residues after plating should be non-corrosive and not affect the long-term reliability of the wire.
[0004] Traditional fluxes used for hot-dip tin plating of copper wire are mostly inorganic salt solutions such as zinc chloride and ammonium chloride, or hydrochloric acid systems. Although highly active, they are also highly corrosive, easily producing black oil and fumes, damaging equipment and the working environment. Furthermore, the residues are hygroscopic and conductive, affecting the insulation performance of the wire. Some improved environmentally friendly fluxes, however, suffer from insufficient wetting properties and poor oxidation resistance under high-speed production conditions.
[0005] In summary, the preparation of a halogen-free, environmentally friendly flux is of great significance in order to solve the above problems. Summary of the Invention
[0006] The purpose of this invention is to provide a halogen-free, environmentally friendly flux and its preparation method to solve the problems raised in the prior art.
[0007] To achieve the above objectives, the present invention provides the following technical solution: A halogen-free environmentally friendly flux, characterized in that: the raw materials of the halogen-free environmentally friendly flux include the following components: 2wt%~6wt% succinic acid, 1wt%~4wt% triethanolamine, 0.1wt%~0.6wt% corrosion inhibitor, 0.1wt%~1.2wt% organosilicon leveling agent, and the remainder being solvent, based on 100wt%.
[0008] In a more optimized configuration, the corrosion inhibitor includes at least one of benzotriazole and methylbenzotriazole; the organosilicon leveling agent is a polyether-modified polysiloxane; and the solvent includes at least one of isopropanol, deionized water, and ethanol.
[0009] In a more optimized form, the raw materials of the halogen-free environmentally friendly flux also include 4-8% polymethacrylic acid modified nanomaterials; the preparation method of the polymethacrylic acid modified nanomaterials is as follows: Step 1: (1) Add copper salt, tin salt and complexing agent to deionized water and mix evenly to obtain copper-tin mixture; add sodium borohydride and complexing agent to deionized water and mix evenly, adjust pH to 10~12 to obtain reaction solution; (2) Under ultrasonic conditions, add conductive nanomaterial to reaction solution and mix, add copper-tin mixture, continue ultrasonication, and load Cu6Sn5 in situ; filter, wash, dry and grind to obtain modified nanomaterial; Step 2: Disperse the modified nanomaterials in deionized water, add methacrylic acid, acrylamide, and an initiator, heat and stir to react, filter and dry to obtain polymethacrylic acid modified nanomaterials.
[0010] In a more optimized form, the raw materials for the polymethacrylic acid modified nanomaterial include the following components: by mass parts, 10-15 parts modified nanomaterial, 5-10 parts methacrylic acid, 0.07-0.12 parts acrylamide, 0.1-0.5 parts initiator, and 60-80 parts deionized water; the initiator includes at least one of ammonium persulfate and potassium persulfate; and the thickness of the polymethacrylic acid in the polymethacrylic acid modified nanomaterial is 100-400 nm.
[0011] In a more optimized form, the raw materials of the copper-tin reaction solution include the following components: by mass parts, 0.5-0.6 parts copper salt, 0.8-1 parts tin salt, 1-2 parts complexing agent, and 30-50 parts deionized water; the raw materials of the reaction solution include the following components: by mass parts, 1-2.5 parts sodium borohydride, 1-2 parts complexing agent, and 100-200 parts deionized water.
[0012] Ideally, the particle size of Cu6Sn5 on the surface of the modified nanomaterial is 20~50nm.
[0013] In a more optimized form, the conductive nanomaterial includes at least one of graphene, reduced graphene oxide, MXene, carbon nanotubes, and nanographite sheets.
[0014] Ideally, the reduced graphene oxide has a thickness of 1-20 nm and a lateral dimension of 100 nm-1 μm.
[0015] A method for preparing a halogen-free, environmentally friendly flux includes the following steps: The solvent is heated to 40-50°C, and the raw materials of the halogen-free environmentally friendly flux are added sequentially. The mixture is stirred evenly and filtered through a 100-150 mesh filter to obtain the halogen-free environmentally friendly flux.
[0016] Compared with the prior art, the beneficial effects of the present invention are: In this solution, succinic acid can quickly react with copper oxide during the preheating stage to form a soluble complex. Its decomposition temperature matches well with the preheating temperature of hot-dip tin plating, providing the necessary cleaning capability. Triethanolamine and succinic acid form an in-situ buffer system to adjust the pH value of the working solution and prevent excessive acidity from corroding the equipment or over-eroding the copper substrate.
[0017] Benzotriazole exhibits a significant synergistic antioxidant effect, forming an extremely thin composite protective film on the copper wire surface during the preheating stage. This effectively blocks air and prevents secondary oxidation of the cleaned surface before it enters the solder pot. It can work with triethanolamine to enhance the protection of copper and prevent oxidation points from forming. The preferred organosilicon leveling agent is polyether-modified polysiloxane, which significantly reduces the surface tension of the flux aqueous solution, allowing it to uniformly and completely coat the high-speed copper wire, forming a thin and continuous liquid film and ensuring uniform activation. It promotes the wetting and spreading of molten solder on the copper wire surface, reduces interfacial tension, helps form a uniform, smooth, and bright plating layer, and reduces dross caused by uneven spreading.
[0018] However, Cu6Sn5 is generated during the hot-dip tin plating process of copper wire. Excessive Cu6Sn5 will increase brittleness and cause tin to fall off. With long-term use or under high temperature environment, the pure tin layer on the surface will be gradually completely consumed, causing black spots to easily appear on the surface of the copper wire. In order to alleviate the formation of Cu6Sn5 during the hot-dip tin plating process of copper wire, the solution introduces reduced graphene oxide into the flux. If the amount added is too small, it will cause exposed solder, and if the amount added is too large, it will reduce the wettability of the tin plating solution and cause poor plating continuity.
[0019] To improve the wettability of the tin plating solution, the proposed method involves in-situ generation of nano-Cu6Sn5 on the surface of reduced graphene oxide, resulting in modified nanomaterials. The reduced graphene oxide can achieve point anchoring and dispersion during the in-situ generation of Cu6Sn5, avoiding particle agglomeration and enabling uniform coating of polymethyl methacrylate in the subsequent process.
[0020] Cu6Sn5 is a natural interface phase in the copper-tin system, which is highly wettable and compatible with molten tin and copper substrate. The outer shell itself is an IMC, which will not damage the interfacial metallurgical bond. It achieves the purpose of improving wettability, improving dispersibility, stabilizing interface distribution, controlling the growth of intermetallic compounds, enhancing coating adhesion and reducing brittleness.
[0021] However, the low hydroxyl content on the surface of nano-Cu6Sn5 makes it difficult to achieve effective grafting modification using silane coupling agents, resulting in easy agglomeration and poor dispersibility in flux systems. To address these issues, this solution employs in-situ polymerization / copolymerization of methacrylic acid and acrylamide to obtain polymethacrylic acid. The nano-Cu6Sn5 layer on the modified nanomaterial contains exposed Cu and Sn atoms, which can interact with the carboxyl and amino groups of polymethacrylic acid to form an interface, thus binding the polymer coating layer and obtaining polymethacrylic acid-modified nanomaterials. The coating process is mild and does not generate new metal oxide layers on the surface of the nano-Cu6Sn5 layer. It only undergoes moderate swelling in water and alcohol-water systems and does not detach from the surface of the polymethacrylic acid-modified nanomaterials, ensuring stable dispersion of the material in flux systems.
[0022] After flux is applied to copper wire and preheated, the polymethyl methacrylate modified nanomaterials in a swollen state can achieve good adhesion to the copper surface. Under the high temperature conditions of hot-dip tin plating, the coated polymethyl methacrylate layer undergoes partial thermal decomposition, exposing the internal nano-Cu6Sn5 layer again. Since Cu6Sn5 has good wettability with both molten tin and the copper substrate, it does not reduce the solder spread rate. However, if the polymethyl methacrylate coating layer is too thick, a continuous organic barrier layer will form on the particle surface, which cannot be rapidly degraded during the short-term hot-dip tin plating process, thus hindering solder wetting and spreading, resulting in a decrease in spread rate and oxidation resistance. Detailed Implementation
[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0024] In the following specific embodiments, "parts" refers to parts by weight. In this embodiment, it should be noted that there are no special restrictions on the manufacturers of the raw materials involved in this invention. Exemplary examples include: copper chloride dihydrate (copper salt) CAS number 10125-13-0; stannous chloride dihydrate (tin salt) CAS number 10025-69-1; trisodium citrate (complexing agent) CAS number 68-04-2; sodium borohydride CAS number 16940-66-2; methylpropane... The CAS number for acrylic acid is 79-41-4; the CAS number for acrylamide is 79-06-1; the CAS number for potassium persulfate (initiator) is 7727-21-1; the CAS number for succinic acid is 110-15-6; the CAS number for triethanolamine is 102-71-6; the CAS number for benzotriazole is 95-14-7; the model number for polyether-modified polysiloxane (organosilicon leveling agent) is BYK333; and the CAS number for methyl methacrylate is 80-62-6.
[0025] Example 1: A method for preparing a halogen-free, environmentally friendly flux, comprising the following steps: 93.2 parts of solvent (isopropanol and deionized water in a mass ratio of 1:1) were heated to 50°C, and 4 parts of succinic acid, 2 parts of triethanolamine, 0.3 parts of benzotriazole and 0.5 parts of polyether-modified polysiloxane (organosilicon leveling agent) were added in sequence. The mixture was then uniformly mixed to obtain a halogen-free environmentally friendly flux.
[0026] Example 2: A method for preparing a halogen-free, environmentally friendly flux, comprising the following steps: 94.1 parts of solvent (deionized water and ethanol in a mass ratio of 2:1) were heated to 50°C, and 3 parts of succinic acid, 2.5 parts of triethanolamine, 0.4 parts of benzotriazole and 0.5 parts of polyether-modified polysiloxane (organosilicon leveling agent) were added in sequence. The mixture was then uniformly mixed to obtain a halogen-free environmentally friendly flux.
[0027] Example 3 is based on Example 1, with the addition of 7 parts of polymethacrylic acid modified nanomaterials; the remaining operation steps are the same; The preparation method of polymethacrylic acid modified nanomaterials is as follows: Step 1: (1) Add 0.57 parts of copper chloride dihydrate, 1 part of stannous chloride dihydrate, and 1.2 parts of trisodium citrate (a coordinating agent) to 45 parts of deionized water and mix evenly to obtain a copper-tin reaction solution; add 2.5 parts of sodium borohydride and 1.2 parts of trisodium citrate (a coordinating agent) to 200 parts of deionized water and mix evenly, and adjust the pH to 11 with 2M NaOH aqueous solution to obtain a reaction solution; (2) Under ultrasonic conditions of 550W, add reduced graphene oxide (the thickness of the reduced graphene oxide is 4nm and the lateral dimension is 500nm) to the reaction solution and mix, add the copper-tin reaction solution at a rate of 1 drop / 2 seconds (0.05mL / drop), continue ultrasonication, filter, wash, vacuum dry, and grind to obtain modified nanomaterials; the particle size of nano-Cu6Sn5 on the surface of the modified nanomaterials is 42nm; Step 2: The preparation method of polymethyl methacrylate modified nanomaterials is as follows: 15 parts of modified nanomaterials are dispersed in 80 parts of deionized water, 10 parts of methacrylic acid, 0.1 parts of acrylamide, and 0.3 parts of potassium persulfate (initiator) are added dropwise, and the mixture is heated and stirred at 75°C. After filtration, washing, and drying, polymethyl methacrylate modified nanomaterials are obtained; the thickness of the polymethyl methacrylate on its surface is 200 nm. 86.2 parts of solvent (isopropanol and deionized water in a 1:1 mass ratio) were heated to 50°C. Then, 4 parts of succinic acid, 2 parts of triethanolamine, 0.3 parts of benzotriazole and 0.5 parts of polyether-modified polysiloxane (organosilicon leveling agent) were added sequentially until completely dissolved. Then, 7 parts of polymethacrylic acid-modified nanomaterials were added, stirred evenly, and filtered through a 150-mesh filter to obtain a halogen-free environmentally friendly flux.
[0028] Comparative Example 1: A method for preparing a halogen-free flux; A halogen-free flux is obtained by uniformly mixing 6 parts adipic acid, 2 parts ethylene glycol, 0.5 parts sodium dodecylbenzenesulfonate (a nonionic surfactant), and the remainder isopropanol.
[0029] Comparative Example 2 is based on Example 3, except that methacrylic acid is replaced with methyl methacrylate monomer; the remaining operating steps are the same. The preparation method of polymethyl methacrylate modified nanomaterials is as follows: Step 1: (1) Add 0.57 parts of copper chloride dihydrate, 1 part of stannous chloride dihydrate, and 1.2 parts of trisodium citrate (a coordinating agent) to 45 parts of deionized water and mix evenly to obtain a copper-tin reaction solution; add 2.5 parts of sodium borohydride and 1.2 parts of trisodium citrate (a coordinating agent) to 200 parts of deionized water and mix evenly, and adjust the pH to 11 with 2M NaOH aqueous solution to obtain a reaction solution; (2) Under ultrasonic conditions of 550W, add reduced graphene oxide (the thickness of the reduced graphene oxide is 4nm and the lateral dimension is 500nm) to the reaction solution and mix, add the copper-tin reaction solution at a rate of 1 drop / 2 seconds (0.05mL / drop), continue ultrasonication, filter, wash, vacuum dry, and grind to obtain modified nanomaterials; the particle size of nano-Cu6Sn5 on the surface of the modified nanomaterials is 42nm; Step 2: The preparation method of polymethyl methacrylate modified nanomaterials is as follows: 15 parts of modified nanomaterials are dispersed in 80 parts of deionized water, 10 parts of methyl methacrylate, 0.1 parts of acrylamide, and 0.3 parts of potassium persulfate (initiator) are added dropwise, and the mixture is heated and stirred at 75°C. After filtration, washing, and drying, polymethyl methacrylate modified nanomaterials are obtained; the thickness of the methyl methacrylate layer on its surface is 252 nm. 86.2 parts of solvent (isopropanol and deionized water in a 1:1 mass ratio) were heated to 50°C. Then, 4 parts of succinic acid, 2 parts of triethanolamine, 0.3 parts of benzotriazole and 0.5 parts of polyether-modified polysiloxane (organosilicon leveling agent) were added sequentially until completely dissolved. Then, 7 parts of polymethyl methacrylate-modified nanomaterials were added, stirred evenly, and filtered through a 150-mesh filter to obtain a halogen-free environmentally friendly flux.
[0030] Comparative Example 3 is based on Example 3, but without the addition of reduced graphene oxide; the remaining operating steps are the same. The preparation method of polymethacrylic acid modified nanomaterials is as follows: Step 1: (1) Add 0.57 parts of copper chloride dihydrate, 1 part of stannous chloride dihydrate, and 1.2 parts of trisodium citrate (complexing agent) to 45 parts of deionized water and mix evenly to obtain a copper-tin reaction solution; add 2.5 parts of sodium borohydride and 1.2 parts of trisodium citrate (complexing agent) to 200 parts of deionized water and mix evenly, and adjust the pH to 11 with 2M NaOH aqueous solution to obtain a reaction solution; (2) Under ultrasonic conditions of 550W, add the copper-tin reaction solution to the reaction solution at a rate of 1 drop / 2 seconds (0.05mL / drop), continue ultrasonication, filter, wash, vacuum dry, and grind to obtain nano Cu6Sn5; the particle size of nano Cu6Sn5 is 58nm; Step 2: The preparation method of polymethyl methacrylate modified nanomaterials is as follows: 15 parts of nano-Cu6Sn5 are ultrasonically dispersed in 80 parts of deionized water, 10 parts of methacrylic acid, 0.1 parts of acrylamide, and 0.3 parts of potassium persulfate (initiator) are added dropwise, and the mixture is heated and stirred at 75°C. After filtration, washing, and drying, polymethyl methacrylate modified nanomaterials are obtained; the thickness of the polymethyl methacrylate on its surface is 234 nm. 86.2 parts of solvent (isopropanol and deionized water in a 1:1 mass ratio) were heated to 50°C. Then, 4 parts of succinic acid, 2 parts of triethanolamine, 0.3 parts of benzotriazole and 0.5 parts of polyether-modified polysiloxane (organosilicon leveling agent) were added sequentially until completely dissolved. Then, 7 parts of polymethacrylic acid-modified nanomaterials were added, stirred evenly, and filtered through a 150-mesh filter to obtain a halogen-free environmentally friendly flux.
[0031] Comparative Example 4 is based on Example 3, but uses a silane coupling agent to modify graphene; the remaining operation steps are the same. The modified nanomaterials are prepared by mixing ethanol, water, and silane coupling agent in a ratio of 10:35:4, adding reduced graphene oxide, stirring in a high-speed mixer (2500 r / min) for 3 minutes, and drying at 80°C to obtain the modified nanomaterials. 86.2 parts of solvent (isopropanol and deionized water in a 1:1 mass ratio) were heated to 50°C. Then, 4 parts of succinic acid, 2 parts of triethanolamine, 0.3 parts of benzotriazole and 0.5 parts of polyether-modified polysiloxane (organosilicon leveling agent) were added sequentially until completely dissolved. Then, 7 parts of modified nanomaterials were added, stirred evenly, and filtered through a 150-mesh filter to obtain a halogen-free environmentally friendly flux.
[0032] Comparative Example 5 is based on Example 3, but with an increased thickness of the polymethacrylic acid layer; the remaining operating steps are the same. The preparation method of polymethacrylic acid modified nanomaterials is as follows: Step 1: (1) Add 0.57 parts of copper chloride dihydrate, 1 part of stannous chloride dihydrate, and 1.2 parts of trisodium citrate (a coordinating agent) to 45 parts of deionized water and mix evenly to obtain a copper-tin reaction solution; add 2.5 parts of sodium borohydride and 1.2 parts of trisodium citrate (a coordinating agent) to 200 parts of deionized water and mix evenly, and adjust the pH to 11 with 2M NaOH aqueous solution to obtain a reaction solution; (2) Under ultrasonic conditions of 550W, add reduced graphene oxide (the thickness of the reduced graphene oxide is 4nm and the lateral dimension is 500nm) to the reaction solution and mix, add the copper-tin reaction solution at a rate of 1 drop / 2 seconds (0.05mL / drop), continue ultrasonication, filter, wash, vacuum dry, and grind to obtain modified nanomaterials; the particle size of nano-Cu6Sn5 on the surface of the modified nanomaterials is 42nm; Step 2: The preparation method of polymethyl methacrylate modified nanomaterials is as follows: 15 parts of modified nanomaterials are dispersed in 80 parts of deionized water, 10 parts of methacrylic acid, 0.1 parts of acrylamide, and 0.3 parts of potassium persulfate (initiator) are added dropwise, and the mixture is heated and stirred at 75°C. After filtration, washing, and drying, polymethyl methacrylate modified nanomaterials are obtained; the thickness of the polymethyl methacrylate on its surface is 1.5 μm. 86.2 parts of solvent (isopropanol and deionized water in a 1:1 mass ratio) were heated to 50°C. Then, 4 parts of succinic acid, 2 parts of triethanolamine, 0.3 parts of benzotriazole and 0.5 parts of polyether-modified polysiloxane (organosilicon leveling agent) were added sequentially until completely dissolved. Then, 7 parts of polymethacrylic acid-modified nanomaterials were added, stirred evenly, and filtered through a 150-mesh filter to obtain a halogen-free environmentally friendly flux.
[0033] Test experiment; (1) According to the test method of GB / T9491, test the solder spread rate (%) of the halogen-free environmentally friendly fluxes prepared in Examples 1-3 and Comparative Examples 1-5 during welding. (2) The copper wire was pretreated and then hot-dip tinned at 260-280°C using the fluxes of Examples 1-3 and Comparative Examples 1-5 to obtain tinned copper wire. The tinned copper wire was aged for 96 hours at 85°C and 85% humidity, and the oxidation black spots on the surface of the tinned copper wire were observed.
[0034] Table 1
[0035] Conclusions: Compared with Example 1, Example 3 showed an improved spreading rate; Comparative Example 2 was based on Example 3, but methacrylic acid was replaced with methyl methacrylate monomer; the ester structure had weak bonding with the copper matrix and solder, resulting in reduced dispersibility in water, which affected the spreading rate of the flux and led to a decrease in oxidation resistance; Comparative Example 3 was based on Example 3, but no conductive nanomaterials were added; this caused nano-Cu6Sn5 to easily agglomerate, and the particle size of nano-Cu6Sn5 coated with the polymethacrylic acid layer increased, thus failing to play its due role in improving wettability, resulting in a decrease in wettability; furthermore, copper may diffuse through the nano-Cu6Sn5 layer to the tin layer, causing the tin layer to be consumed, reducing oxidation resistance, and leading to more black spots.
[0036] Comparative Example 4, based on Example 3, modified reduced graphene oxide using a silane coupling agent; no nano-Cu6Sn5 layer was deposited on the surface of the reduced graphene oxide, resulting in weak bonding between the silane-modified reduced graphene oxide and the tin plating layer, and a decrease in the barrier effect of the reduced graphene oxide, thus leading to a decrease in antioxidant properties; Comparative Example 5, based on Example 3, increased the thickness of the polymethyl methacrylate layer; an excessively thick polymethyl methacrylate layer is difficult to degrade rapidly during high-temperature soldering, hindering solder wetting and spreading, resulting in a significant decrease in spread rate, but maintaining excellent antioxidant properties.
[0037] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.
Claims
1. A halogen-free, environmentally friendly flux, characterized in that: The raw materials of the halogen-free environmentally friendly flux include the following components: 2wt%~6wt% succinic acid, 1wt%~4wt% triethanolamine, 0.1wt%~0.6wt% corrosion inhibitor, 0.1wt%~1.2wt% organosilicon leveling agent, and the remainder being solvent, based on 100wt%.
2. The halogen-free environmentally friendly flux according to claim 1, characterized in that: The corrosion inhibitor includes at least one of benzotriazole and methylbenzotriazole; the organosilicon leveling agent is a polyether-modified polysiloxane; the solvent includes at least one of isopropanol, deionized water, and ethanol.
3. The halogen-free environmentally friendly flux according to claim 1, characterized in that: The raw materials for the halogen-free environmentally friendly flux also include 4-8% polymethyl methacrylate modified nanomaterials; the preparation method of the polymethyl methacrylate modified nanomaterials is as follows: Step 1: (1) Add copper salt, tin salt and complexing agent to deionized water and mix evenly to obtain copper-tin mixture; add sodium borohydride and complexing agent to deionized water and mix evenly, adjust pH to 10~12 to obtain reaction solution; (2) Under ultrasonic conditions, add conductive nanomaterial to reaction solution and mix, add copper-tin mixture, continue ultrasonication, and load Cu6Sn5 in situ; filter, wash, dry and grind to obtain modified nanomaterial; Step 2: Disperse the modified nanomaterials in deionized water, add methacrylic acid, acrylamide, and an initiator, heat and stir to react, filter and dry to obtain polymethacrylic acid modified nanomaterials.
4. The halogen-free environmentally friendly flux according to claim 3, characterized in that: The raw materials for the polymethyl methacrylate modified nanomaterial include the following components: by mass parts, 10-15 parts modified nanomaterial, 5-10 parts methacrylic acid, 0.07-0.12 parts acrylamide, 0.1-0.5 parts initiator, and 60-80 parts deionized water; the initiator includes at least one of ammonium persulfate and potassium persulfate; in the polymethyl methacrylate modified nanomaterial, the thickness of the polymethyl methacrylate is 100-400 nm.
5. The halogen-free environmentally friendly flux according to claim 3, characterized in that: The raw materials of the copper-tin reaction solution include the following components: by mass parts, 0.5-0.6 parts copper salt, 0.8-1 parts tin salt, 1-2 parts complexing agent, and 30-50 parts deionized water; the raw materials of the reaction solution include the following components: by mass parts, 1-2.5 parts sodium borohydride, 1-2 parts complexing agent, and 100-200 parts deionized water.
6. The halogen-free environmentally friendly flux according to claim 3, characterized in that: The particle size of Cu6Sn5 on the surface of the modified nanomaterial is 20~50nm.
7. The halogen-free environmentally friendly flux according to claim 3, characterized in that: The conductive nanomaterials include at least one of graphene, reduced graphene oxide, MXene, carbon nanotubes, and nanographite sheets.
8. The halogen-free environmentally friendly flux according to claim 7, characterized in that: The reduced graphene oxide has a thickness of 1~20nm and a lateral dimension of 100nm~1μm.
9. The method for preparing a halogen-free environmentally friendly flux according to claim 1, characterized in that: The following steps are included: The solvent is heated to 40-50°C, and the raw materials of the halogen-free environmentally friendly flux are added sequentially. The mixture is stirred evenly and filtered through a 100-150 mesh filter to obtain the halogen-free environmentally friendly flux.