Liquid soldering flux suitable for various welding processes and preparation method thereof

Abstract

The invention relates to a liquid soldering flux suitable for various welding processes and a preparation method of the liquid soldering flux. The liquid soldering flux comprises the following components in percentage by weight: 2.0 to 3.0 percent of film-forming agent, 1.0 to 2.0 percent of active agent, 0.1 to 0.5 percent of surfactant, 0.5 to 1.0 percent of corrosion inhibitor and the balance of solvent. According to the invention, a plurality of components such as a film forming substance with water resistance, solvent resistance and chemical resistance, an active agent with chelating property, a polyether modified polysiloxane surfactant with a twin structure, a 2-butoxyethyl benzoate solvent with high boiling point and splashing resistance and the like are compounded; the prepared liquid soldering flux is suitable for wave soldering, dip soldering, series soldering and the like and is halogen-free, low in residue, high in activity, high in reliability, few in splashing and residue and low in corrosion.

Description

Technical Field

[0001] This invention belongs to the field of electronic soft soldering materials technology, specifically relating to a liquid flux suitable for various soldering processes and its preparation method. Background Technology

[0002] Liquid fluxes are mainly used in welding processes such as wave soldering, dip soldering, and string soldering. With the rapid development of electronic information products, the performance requirements for fluxes are becoming increasingly stringent. For example, fluxes for wave soldering must have high activity, low residue, and low corrosion; fluxes for dip soldering, in addition to high activity, must also be free of spatter at rapid high temperatures; and fluxes for photovoltaic module string soldering need to be halogen-free and have low residue. These different processes place higher demands on the versatility and applicability of fluxes. To meet the needs of customers for different welding processes, flux manufacturers produce a wide variety of flux products of different types and models. Some flux formulations are suitable for wave soldering, some for dip soldering, and others for string soldering, etc. The applicability of each flux is limited, and each flux is difficult to apply to different welding processes, resulting in a wide variety of fluxes produced by companies with poor versatility. Furthermore, the production process of multiple flux varieties requires changing raw materials and cleaning reaction vessels, increasing raw material losses and affecting production efficiency. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of existing fluxes in terms of poor applicability, and to provide a flux that is suitable for different soldering processes, is halogen-free, has low residue, good activity, is not prone to spattering, and can prevent the PCB board from turning white after soldering. This invention also provides a method for preparing such flux.

[0004] To achieve the objectives of this invention, the technical solution adopted is as follows: A liquid flux suitable for various welding processes, wherein the components and contents of the liquid flux are: film-forming agent 2.0 wt.% to 3.0 wt.%, activator 1.0 wt.% to 2.0 wt.%, surfactant 0.1 wt.% to 0.5 wt.%, corrosion inhibitor 0.5 wt.% to 1.0 wt.%, and the balance being solvent; The film-forming agent is a compound mixture of DS50 and low softening point hydrogenated rosin; the mass ratio of polyurethane polyol resin DS50 to low softening point hydrogenated rosin is 1-2:2-4. The activator is a compound mixture of dimercaptosuccinic acid with chelating effect and long-chain saturated or unsaturated halogen-free organic acids with C16 or more; the mass ratio of dimercaptosuccinic acid to long-chain saturated or unsaturated halogen-free organic acids with C16 or more is 2-4:1-2. The surfactant is TEGO 4200; The corrosion inhibitor is benzotriazole; The solvent contains ethyl 2-butoxybenzoate in a content of 1 wt.% to 5 wt.% and the remainder is one of methanol, ethanol, and isopropanol.

[0005] Furthermore, the low softening point hydrogenated rosin is one of KR-610, HYPALE CH, or FORAL AX-E, with a softening point below 90°C.

[0006] Furthermore, the long-chain saturated or unsaturated halogen-free organic acid with C16 or higher is one of palmitic acid, stearic acid, octadecanoic acid, docosanoic acid, and tetracosanoic acid.

[0007] The preparation method of the liquid flux applicable to various welding processes described in this invention involves weighing methanol, ethanol, or isopropanol and placing them in a reaction vessel, then adding ethyl 2-butoxybenzoate and stirring until homogeneous. Next, polyurethane polyol resin DS50 is added and stirred for 5-7 minutes. Then, low softening point hydrogenated rosin, activator, surfactant, and corrosion inhibitor are added sequentially and stirred for 8-12 minutes to obtain the liquid flux.

[0008] The present invention has the following beneficial effects: 1. This invention uses DS50 polyurethane polyol resin, which is water-resistant, solvent-resistant, and chemical-resistant. It is a white liquid film-forming substance. Through reasonable compounding with hydrogenated rosin, it not only reduces post-soldering residues but also forms a film with high hardness and good gloss. This solves the technical problem of low reliability caused by flux residues after soldering, such as easy corrosion and whitening under high humidity and high chemical conditions.

[0009] 2. This invention employs a compound mixture of dimercaptosuccinic acid with chelating properties and long-chain saturated or unsaturated halogen-free organic acids with C16 or higher. First, under the energy provided by heating, dimercaptosuccinic acid utilizes the carboxylic acid H⁺ ions to weakly erode the oxide lattice, causing some metal ions (such as Cu²⁺ and Ag⁺) to "loosen" from the lattice. These loosened metal ions are immediately "captured" by the coordinating atoms O / S of the dimercaptosuccinic acid molecule, forming one or more five- or six-membered ring structures. This ring structure exhibits extremely high stability (referred to as the chelation effect). The chelation reaction begins at the surface of the oxide layer and gradually penetrates inward. As the surface oxide is converted into soluble chelates and dissolves, the next layer of oxide is exposed and continues to be chelated until fresh, different Cu (mainly involved in wave soldering, dip soldering, and string soldering processes) and Ag (mainly involved in string soldering processes) metal substrates are exposed. This metal substrate provides a guarantee for the subsequent solder alloy welding. Secondly, a long-chain saturated or unsaturated halogen-free organic acid activator system with C16 or higher is used. The activators in this system have better high-temperature resistance and spatter resistance than commonly used low-carbon activators. Furthermore, through compounding with dimercaptosuccinic acid, its welding activity is suitable for wave soldering, string soldering, and dip soldering. In addition, the multiple five- or six-membered ring chelates formed due to the chelation effect have extremely high stability and corrosion resistance, and are well-matched with corrosion inhibitors, further reducing the corrosiveness of the flux.

[0010] 3. This invention uses TEGO 4200, a twin-structure polyether modified polysiloxane surfactant. Because this surfactant has extremely low surface tension and excellent spreading ability, it is also a very good and efficient wetting agent. By adding this substance, the activity and solderability of the flux can be further enhanced.

[0011] 4. This invention utilizes high-boiling-point, anti-spatter ethyl 2-butoxybenzoate, which can more effectively assist in the fusion of components and reduce spatter during high-temperature welding. Simultaneously, this substance can also be used as a cleaning agent for surface contaminants on various metal substrates, effectively removing foreign matter and preparing the surface for subsequent welding.

[0012] In summary, this invention uses a combination of multiple components, including a white liquid film-forming substance with water resistance, solvent resistance, and chemical resistance; a chelating surfactant; a polyether-modified polysiloxane surfactant with a twin structure; and a high-boiling-point, anti-spatter ethyl 2-butoxybenzoate solvent, to prepare a liquid flux suitable for wave soldering, dip soldering, and string soldering. This flux is characterized by low residue, high activity, high reliability, and low spatter resistance, reducing the inconvenience caused by changing raw materials and cleaning reaction vessels during the production of multiple fluxes and simplifying the production process. Detailed Implementation

[0013] The present invention will be further described below with reference to the embodiments. Example 1

[0014] This liquid flux, suitable for various welding processes, comprises the following components and contents: 1.5 wt.% polyurethane polyol resin DS50, 1.5 wt.% KR-610 rosin, 1.6 wt.% dimercaptosuccinic acid, 0.4 wt.% palmitic acid, 0.1 wt.% twin-structure polyether modified polysiloxane surfactant TEGO 4200, 0.5 wt.% benzotriazole, 93.4 wt.% methanol, and 1.0 wt.% 2-butoxybenzoate. The polyurethane polyol resin DS50 is a synthetic resin from TEGO, model TEGO VariPlus DS50, and TEGO 4200 is a surfactant manufactured by TEGO; both are commercially available.

[0015] Liquid flux is prepared as follows: methanol is placed in a reaction vessel, ethyl 2-butoxybenzoate is added, and the mixture is stirred for 2 to 3 minutes. Then, polyurethane polyol resin DS50 is added and stirred for 5 to 7 minutes. Next, KR-610 rosin, dimercaptosuccinic acid, palmitic acid, TEGO 4200, and benzotriazole are added in sequence and stirred for 8 to 12 minutes to obtain the liquid flux. Example 2

[0016] This liquid flux is suitable for various welding processes. Its components and contents are as follows: DS50 1.0 wt.%, HYPALE CH rosin 1.0 wt.%, dimercaptosuccinic acid 1.0 wt.%, stearic acid 1.0 wt.%, TEGO 4200 0.3 wt.%, benzotriazole 0.8 wt.%, ethanol 92.9 wt.%, and ethyl 2-butoxybenzoate 2.0 wt.%.

[0017] The flux for solder wire is prepared as follows: Ethanol is placed in a reaction vessel, ethyl 2-butoxybenzoate is added, and the mixture is stirred for 2 to 3 minutes. Then DS50 is added, and the mixture is stirred for 5 to 7 minutes. Then HYPALE CH rosin, dimercaptosuccinic acid, stearic acid, TEGO 4200, and benzotriazole are added in sequence, and the mixture is stirred for 8 to 12 minutes to obtain the liquid flux. Example 3

[0018] This liquid flux, suitable for various welding processes, comprises the following components and contents: DS50 0.6 wt.%, FORAL AX-E rosin 2.4 wt.%, dimercaptosuccinic acid 0.8 wt.%, octadecanoic acid 0.2 wt.%, TEGO 4200 0.5 wt.%, benzotriazole 1.0 wt.%, isopropanol 91.5 wt.%, and ethyl 2-butoxybenzoate 3.0 wt.%.

[0019] The flux for solder wire is prepared as follows: Isopropanol is placed in a reaction vessel, ethyl 2-butoxybenzoate is added, and the mixture is stirred for 2-3 minutes. Then DS50 is added, and the mixture is stirred for 5-7 minutes. Then FORAL AX-E rosin, dimercaptosuccinic acid, octadecanoic acid, TEGO 4200, and benzotriazole are added in sequence, and the mixture is stirred for 8-12 minutes to obtain the liquid flux. Example 4

[0020] This liquid flux, suitable for various welding processes, comprises the following components and contents: DS50 0.5 wt.%, KR-610 rosin 2.0 wt.%, dimercaptosuccinic acid 1.2 wt.%, docosanoic acid 0.8 wt.%, TEGO 4200 0.3 wt.%, benzotriazole 0.8 wt.%, isopropanol 91.4 wt.%, and ethyl 2-butoxybenzoate 3.0 wt.%.

[0021] Solder flux for solder wire is prepared as follows: Solvents such as isopropanol are placed in a reaction vessel, then ethyl 2-butoxybenzoate is added and stirred for 2-3 minutes. Then DS50 is added and stirred for 5-7 minutes. Next, KR-610 rosin, dimercaptosuccinic acid, docosanoic acid, TEGO 4200, and benzotriazole are added in sequence and stirred for 8-12 minutes to obtain liquid flux. Example 5

[0022] This liquid flux, suitable for various welding processes, comprises the following components and contents: DS50 0.4 wt.%, HYPALE CH rosin 1.6 wt.%, dimercaptosuccinic acid 0.5 wt.%, icosicosuccinic acid 0.5 wt.%, TEGO 4200 0.3 wt.%, benzotriazole 0.5 wt.%, ethanol 91.2 wt.%, and ethyl 2-butoxybenzoate 5.0 wt.

[0023] The flux for solder wire is prepared as follows: Ethanol is placed in a reaction vessel, then ethyl 2-butoxybenzoate is added and stirred for 2-3 minutes. Then DS50 is added and stirred for 5-7 minutes. Then HYPALE CH rosin, dimercaptosuccinic acid, icosuccinic acid, TEGO 4200 and benzotriazole are added in sequence and stirred for 8-12 minutes to obtain liquid flux.

[0024] The flux prepared according to the above component content and method was tested, and the performance test results are shown in Table 1.

[0025] Table 1 Performance testing results of liquid flux As shown in Table 1, the present invention exhibits excellent welding performance, minimal spatter, low corrosion, and a spread rate >80%, meeting the requirements of the international standard IPC-TM-650. It is suitable for various welding processes such as wave soldering, dip soldering, and string soldering.

[0026] The long-chain saturated or unsaturated halogen-free organic acids with C16 and above as described in this invention include, but are not limited to, palmitic acid, stearic acid, octadecanoic acid, docosanoic acid, and tetracosanoic acid. Low-softening-point hydrogenated rosin with a softening point below 90°C includes, but is not limited to, KR-610, HYPALE CH, and FORAL AX-E.

Claims

1. A liquid flux suitable for various welding processes, characterized in that, The liquid flux comprises and contains the following components and contents: film-forming agent 2.0 wt.% to 3.0 wt.%, activator 1.0 wt.% to 2.0 wt.%, surfactant 0.1 wt.% to 0.5 wt.%, corrosion inhibitor 0.5 wt.% to 1.0 wt.%, with the balance being solvent; The film-forming agent is a compound mixture of DS50 and low softening point hydrogenated rosin; the mass ratio of DS50 to low softening point hydrogenated rosin is 1-2:2-4. The activator is a compound mixture of dimercaptosuccinic acid and long-chain saturated or unsaturated halogen-free organic acids with C16 or more; the mass ratio of dimercaptosuccinic acid to long-chain saturated or unsaturated halogen-free organic acids with C16 or more is 2-4:1-2. The surfactant is TEGO 4200; The corrosion inhibitor is benzotriazole; The solvent contains ethyl 2-butoxybenzoate in a content of 1 wt.% to 5 wt.% and the remainder is one of methanol, ethanol, and isopropanol.

2. The liquid flux suitable for various welding processes according to claim 1, characterized in that, The low softening point hydrogenated rosin is one of KR-610, HYPALE CH, or FORAL AX-E, with a softening point below 90°C.

3. The liquid flux suitable for various welding processes according to claim 1 or 2, characterized in that, The long-chain saturated or unsaturated halogen-free organic acids with C16 or higher are one of palmitic acid, stearic acid, octadecanoic acid, docosanoic acid, and tetracosanoic acid.

4. The method for preparing liquid flux suitable for various welding processes as described in claim 1, 2, or 3, characterized in that the method... The following steps are taken: Weigh methanol, ethanol, or isopropanol and place them in a reaction vessel, then add ethyl 2-butoxybenzoate and stir until homogeneous. Then add DS50 and stir for 5-7 minutes. Next, add low softening point hydrogenated rosin, activator, surfactant, and corrosion inhibitor in sequence and stir for 8-12 minutes to obtain the liquid flux.

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