Low-residue flux and preparation method and application thereof

Abstract

The present disclosure provides a low-residue flux and a preparation method and application thereof, and belongs to the technical field of welding. The flux comprises an active agent, a self-crosslinking emulsion and a solvent; the mass ratio of the self-crosslinking emulsion and the active agent is 0.3-2:100; the mass ratio of the solvent and the active agent is 0.8-2:1; and the self-crosslinking emulsion comprises a self-crosslinking acrylic emulsion and a self-crosslinking polyurethane emulsion. The present disclosure adds the self-crosslinking emulsion to the flux, improves the coating firmness and welding performance of the flux, and reduces the welding smoke amount and organic residue.

Description

Technical Field

[0001] This disclosure relates to the field of welding technology, specifically to a low-residue flux, its preparation method, and its application. Background Technology

[0002] New energy vehicles powered by batteries are experiencing rapid development and application due to their advantages such as zero greenhouse gas emissions, no environmental pollution, high efficiency, and low noise. The structure of the battery's electrolyte inlet is complex, requiring high precision and skill in welding. When using traditional solder paste to weld the electrolyte inlet, the high organic content can cause components to penetrate into the battery. Furthermore, the evaporation and decomposition of organic solvents during welding introduce impurities into the battery, degrading its performance. This also contaminates battery seals and surrounding equipment, increasing cleaning difficulty. Additionally, the production of large amounts of fumes pollutes the environment and negatively impacts the health of operators. When using pre-formed solder, its large heat dissipation area and high flux content can leave voids and organic residues at the welding interface, affecting heat dissipation and post-weld reliability.

[0003] Therefore, in view of the shortcomings of the above-mentioned prior art, there is an urgent need to provide a no-clean, residue-free flux with high coating adhesion and welding performance, low welding fume production, and no residue after welding. Summary of the Invention

[0004] The purpose of this disclosure is to overcome the shortcomings of the prior art and to provide a low-residue flux, its preparation method, and its application.

[0005] To achieve the above objectives, the technical solution adopted in this disclosure is as follows: This disclosure provides a flux, including an activator, a self-crosslinking emulsion, and a solvent; the mass ratio of the self-crosslinking emulsion to the activator is 0.3-2:100; the mass ratio of the solvent to the activator is 0.8-2:1; the self-crosslinking emulsion includes a self-crosslinking acrylic emulsion and a self-crosslinking polyurethane emulsion.

[0006] In some embodiments, the mass ratio of the self-crosslinking emulsion to the surfactant is (1-1.7):100.

[0007] In some embodiments, the mass ratio of the self-crosslinking acrylic emulsion to the self-crosslinking polyurethane emulsion is (1.5-9):1.

[0008] In some embodiments, the glass transition temperature of the self-crosslinking acrylic emulsion is ≤30°C.

[0009] In some embodiments, the minimum film-forming temperature of the self-crosslinking polyurethane emulsion is ≤0°C.

[0010] In some embodiments, the activator is a fluoroaluminate.

[0011] In some embodiments, the solvent is at least one of water, alcohol, and ether.

[0012] In some embodiments, the alcohol is at least one selected from ethanol, n-propanol, and propylene glycol;

[0013] And / or, the ether is at least one of propylene glycol butyl ether, ethylene glycol butyl ether, propylene glycol methyl ether, ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, and dipropylene glycol dimethyl ether.

[0014] Secondly, a method for preparing the flux is provided, comprising the following steps: first, stirring the activator and solvent evenly, and then adding the self-crosslinking emulsion and stirring evenly to obtain the flux.

[0015] Thirdly, a metal-coated component is provided, the metal-coated component comprising a metal and the flux coated on at least a portion of the surface of the metal.

[0016] In some embodiments, the preparation method includes coating the flux onto at least a portion of the surface of a metal to obtain a metal-coated component.

[0017] In some embodiments, the flux is applied to at least a portion of the metal surface by simultaneous spraying and baking.

[0018] Fourthly, a brazing method is provided using the metal-coated component or a prepared metal-coated component, comprising the following steps: assembling at least one of the metal-coated components or a prepared metal-coated component with at least one metal component, and brazing the assembly.

[0019] Fifthly, a brazed assembly is provided, the brazed assembly being obtained by the method described above.

[0020] Sixthly, the application of the aforementioned metal-coated components in the brazing of power batteries, energy storage batteries, automotive radiators, and IGBT module radiators is provided.

[0021] Compared with the prior art, the beneficial effects of this disclosure are as follows: Firstly, by adding a self-crosslinking emulsion to the flux, the self-crosslinking emulsion used in this disclosure replaces the adhesive in the flux, thereby reducing the decomposition of organic matter and spatter during the welding process. Therefore, after welding, there is no need to clean the weldment, welding equipment, and fixtures. Secondly, the flux of this disclosure has a low organic content, further reducing the decomposition of organic matter and the amount of smoke during the welding process, thus improving safety and environmental friendliness. Thirdly, this disclosure uses self-crosslinking acrylic emulsion and self-crosslinking polyurethane emulsion as self-crosslinking emulsions. During film formation, the self-crosslinking acrylic easily bonds with the hydroxyl groups in the activator to form a coating on the metal surface. The combined action of the self-crosslinking polyurethane emulsion and the self-crosslinking acrylic emulsion improves the adhesion of the flux to the metal and the welding performance, effectively preventing a decrease in the coating firmness and welding performance of the flux. Attached Figure Description

[0022] Figure 1 Ultrasonic scanning image of the welding void rate of flux in Example 10;

[0023] Figure 2 Ultrasonic scanning image of the welding void rate of flux in Comparative Example 5;

[0024] Figure 3 Examples of coating adhesion tests before and after Example 10 are shown.

[0025] Figure 4 The image shows the results of the flux coating adhesion test in Comparative Example 10.

[0026] Figure 5 Example images of flux coating adhesion before and after comparison example 10. Detailed Implementation

[0027] To facilitate understanding of this disclosure, a more complete description will be provided below. However, this disclosure may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure.

[0028] As used in this article:

[0029] "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0030] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0031] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1-5” is disclosed, the described range should be interpreted as including ranges “1-4”, “1-3”, “1-2”, “1-2 and 4-5”, “1-3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0032] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0033] "Parts by mass" refers to the basic unit of measurement that expresses the mass ratio of multiple components. One part can represent any unit mass, such as 1g or 2.689g. If we say that component A has "a" parts by mass and component B has "b" parts by mass, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it can mean that the mass of component A is aK and the mass of component B is bK (K is any number representing a multiplier). It is important to understand that, unlike the number of parts by mass, the sum of the mass parts of all components is not limited to 100 parts.

[0034] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0035] This disclosure provides a flux comprising an activator, a self-crosslinking emulsion, and a solvent; the mass ratio of the self-crosslinking emulsion to the activator is 0.3-2:100; the mass ratio of the solvent to the activator is 0.8-2:1; the self-crosslinking emulsion comprises a self-crosslinking acrylic emulsion and a self-crosslinking polyurethane emulsion.

[0036] Specifically, the mass ratio of the self-crosslinking emulsion to the surfactant can be, but is not limited to, 0.3:100, 0.5:100, 0.7:100, 0.9:100, 1.1:100, 1.3:100, 1.5:100, 1.7:100, or 2:100; preferably (1-1.8):100.

[0037] Specifically, the mass ratio of the solvent to the surfactant is 0.8-2:1, and can be, for example, but not limited to, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, or 2:1.

[0038] This disclosure adds a self-crosslinking emulsion to the flux. Firstly, the self-crosslinking emulsion used in this disclosure replaces the adhesive in the flux, thereby reducing organic matter decomposition and spatter during welding. Therefore, after welding, there is no need to clean the workpiece, welding equipment, and fixtures. Secondly, the flux of this disclosure has a low organic matter content, further reducing organic matter decomposition and smoke during welding, thus improving safety and environmental friendliness. Thirdly, this disclosure uses self-crosslinking acrylic emulsion and self-crosslinking polyurethane emulsion as self-crosslinking emulsions. During film formation, the self-crosslinking acrylic easily bonds with the hydroxyl groups in the activator, forming a coating on the metal surface. The combined effect of the self-crosslinking polyurethane emulsion and the self-crosslinking acrylic emulsion improves the flux's adhesion to the metal and welding performance, effectively preventing a decrease in flux coating firmness and welding performance.

[0039] In this disclosure, the mass ratio of the self-crosslinking emulsion to the activator affects the flux performance. If the mass ratio is less than 0.3:100, it leads to a decrease in flux coating adhesion and welding performance, and also causes flux powder to fall off during the coating process. If the mass ratio is greater than 2:100, it leads to a higher amount of smoke generated during welding and a higher amount of residual organic matter, thus resulting in a decrease in welding performance. This disclosure preferably uses a mass ratio of 1-1.7:100 for the crosslinking emulsion to the activator, which can obtain a flux with high coating adhesion and welding performance, as well as low welding smoke.

[0040] In this disclosure, the mass ratio of solvent to activator also affects the use and performance of flux. If the mass ratio of solvent to activator is less than 0.8:1, the flux is prone to clogging the coating equipment during the coating process. If the mass ratio of solvent to activator is greater than 2:1, it will increase the number of flux coatings, reduce the efficiency of flux use, and may lead to a decrease in the soldering performance of flux.

[0041] In some embodiments, the mass ratio of the self-crosslinking acrylic emulsion to the self-crosslinking polyurethane emulsion is (1.5-9):1, for example, but not limited to 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, 7.5:1, 8:1, 8.5:1, and 9:1.

[0042] In this disclosure, the mass ratio of self-crosslinking acrylic emulsion to self-crosslinking polyurethane emulsion also affects the performance of the flux. Too much or too little self-crosslinking polyurethane emulsion will lead to a decrease in the coating adhesion of the flux.

[0043] In some embodiments, the glass transition temperature of the self-crosslinking acrylic emulsion is ≤30°C, and may be, for example, but not limited to, -40°C, -35°C, -30°C, -25°C, -20°C, -15°C, -10°C, -5°C, 0°C, 5°C, 10°C, 15°C, 20°C, 25°C, or 30°C.

[0044] Specifically, the glass transition temperature of the self-crosslinking acrylic emulsion was determined with reference to the GB / T 27816 standard.

[0045] In some embodiments, the minimum film-forming temperature of the self-crosslinking polyurethane emulsion is ≤0°C, for example, but not limited to -45°C, -40°C, -35°C, -30°C, -25°C, -20°C, -15°C, -10°C, -5°C, and 0°C.

[0046] When the glass transition temperature of a self-crosslinking acrylic emulsion is greater than 30°C or the minimum film-forming temperature of a self-crosslinking polyurethane emulsion is greater than 0°C, it will lead to an increase in the weld void rate.

[0047] Specifically, the minimum film-forming temperature of the self-crosslinking polyurethane emulsion was tested in accordance with the GB / T 9267-2008 standard.

[0048] In one embodiment, the activator is a fluoroaluminate, including potassium fluoroaluminate such as KAlF4, K2AlF5, K3AlF6, K2AlF5·H2O, cesium fluoroaluminate such as CsAlF4, Cs2AlF5, Cs3AlF6, and potassium cesium fluoroaluminate such as KCs2Al3F4. 12CsK2AlF6, and alkali metal zinc fluoroaluminates such as KZnAlF6, K2ZnAlF7, KZn2AlF8, KZnAl2F9, CsZnAlF6, Cs2ZnAlF7, CsZn2AlF8, and CsZnAl2F9, etc. Each of the foregoing may be amorphous and / or partially or completely in one or more XRD-separable phases. Generally, activators and their manufacture are known: for example, potassium fluoroaluminate can be manufactured from HAlF4 (obtained from HF and Al(OH)3 or Al2O3) and KOH. This is described, for example, in US4,428,920, US4,579,605, and US5,968,288. US 3,951,328, US6,221,129, or US3,971,501 describe fluxes based on KAlF4 and K3AlF6. US4,689,092 describes a flux based on potassium fluoroaluminate and cesium fluoroaluminate. CN 104822488A describes a flux based on general formula K. w Zn x Al y F z The flux is represented by the alkali metal zinc fluoroaluminate, where w, x, y, and z are positive integers, and the greatest common divisor of w, x, y, and z is 1.

[0049] In one embodiment, the average particle size of the surfactant is preferably below 80 μm. For example, the average particle size of the surfactant can be, but is not limited to, 1 μm, 3 μm, 5 μm, 7 μm, 10 μm, 12 μm, 15 μm, 17 μm, 20 μm, 23 μm, 25 μm, 28 μm, 30 μm, 32 μm, 35 μm, 37 μm, 40 μm, 43 μm, 45 μm, 48 μm, 50 μm, 52 μm, 55 μm, 57 μm, 60 μm, 63 μm, 65 μm, 68 μm, 70 μm, 72 μm, 75 μm, 78 μm, preferably 1 to 50 μm, and particularly preferably 1 to 20 μm. When the average particle size of the activator is within the above range, the activator exhibits high reactivity with aluminum alloys and improves the inhibition effect of chemical reactions with oxygen; it also improves the welding wettability of the flux, thereby enhancing the welding bond strength.

[0050] Specifically, the average particle size of the active agent was obtained by testing according to the GB / T 19077-2016 standard.

[0051] In one embodiment, the flux may further include additives, wherein the additives constitute no more than 0.5 wt% of the flux by mass, preferably no more than 0.2 wt% of the flux by mass; more preferably, the flux does not contain additives.

[0052] In one embodiment, the additives include binders, thickeners, thixotropic agents, solder metals, solder metal alloys, etc., which can be used alone or in combination.

[0053] Additives can be added to flux through mechanical mixing. However, excessive additive content can lead to a decrease in the overall performance of the flux.

[0054] Examples of suitable adhesives include, but are not limited to, polyolefins, polyurethanes, polymethacrylates, and butyl rubber.

[0055] Examples of suitable thickeners include, but are not limited to, different types of cellulose ethers or polyvinyl alcohols of different degrees of hydrolysis. Different types of cellulose ethers, for example, are called methylcellulose if they are substituted with methyl; hydroxyethylcellulose if they are substituted with hydroxyethyl; and hydroxypropylcellulose if they are substituted with hydroxypropyl.

[0056] The composition of the solder metal and / or solder metal alloy is not specifically limited. That is, regardless of the composition of the solder metal and / or solder metal alloy used, the flux disclosed herein will not impair the formation of solder voids and the inhibition of solder ball formation, and will ensure the uniformity of flux coating, as well as the balance of low flux residue, solder wettability and scratch resistance.

[0057] Examples of components that can be used in solder metals and / or solder metal alloys include, but are not limited to, at least one of Sn, Pb, Ag, Bi, In, Cu, Zn, Ga, Sb, Au, Pd, Ge, Ni, Cr, Al, Co, Fe, and Si.

[0058] Using flux containing the aforementioned solder metals and / or solder metal alloys can suppress cracking at the solder joints, even under conditions of severe temperature fluctuations and vibrations.

[0059] In some embodiments, the solvent is at least one of water, alcohol, and ether.

[0060] As mentioned in this article, "alcohol" refers to a compound in which the hydrogen atom in the side chain of aliphatic alkanes, alicyclic alkanes or aromatic alkanes is replaced by a hydroxyl group, and the general formula is a hydroxyl group connected to a saturated sp3 hybridized carbon atom.

[0061] Specifically, this disclosure prefers fatty alcohols, which can be, but are not limited to, fatty monohydric alcohols and fatty dihydric alcohols.

[0062] In one embodiment, the alcohol is an aliphatic monohydric alcohol, wherein the number of carbon atoms in the aliphatic monohydric alcohol is ≤12. Specific examples of aliphatic monohydric alcohols include methanol, ethanol, n-propanol, isopropanol, n-butanol, and isobutanol. This disclosure preferably uses n-propanol as an aliphatic monohydric alcohol.

[0063] In one embodiment, the alcohol is an aliphatic diol, and the number of carbon atoms in the aliphatic diol is ≤6. Specific examples of aliphatic diols include ethylene glycol, propylene glycol, trimethylethylene glycol, 1,3-butanediol, 2,3-butanediol, 1,4-butanediol, 1,5-pentanediol, and 1,6-hexanediol; propylene glycol is preferred as an aliphatic diol in this disclosure.

[0064] In one embodiment, the ether is at least one selected from propylene glycol butyl ether, ethylene glycol butyl ether, propylene glycol methyl ether, ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, and dipropylene glycol dimethyl ether.

[0065] Specifically, this disclosure prefers water as a solvent. Compared with alcohol and / or ether, water has better solubility and dispersion of surfactants and self-crosslinking emulsions. In addition, water is an inorganic substance, non-toxic, environmentally friendly, safe, and lower in cost.

[0066] Secondly, a method for preparing the flux is provided, comprising the following steps: first, stirring the activator and solvent evenly, and then adding the self-crosslinking emulsion and stirring evenly to obtain the flux.

[0067] In the preparation process of the flux disclosed herein, the self-crosslinking emulsion and the activator should not be mixed first or simultaneously. If the self-crosslinking emulsion and the activator are mixed first or simultaneously, the activator will absorb the solvent in the self-crosslinking emulsion, causing the self-crosslinking emulsion to fail to crosslink or reduce the degree of self-crosslinking of the self-crosslinking emulsion, thereby reducing the strength and welding performance of the flux.

[0068] Specifically, there is no specific limitation on the stirring time, as long as all components are stirred evenly. In order to improve the uniformity of each component, the stirring time should be greater than 5 minutes after each addition of the component. In order to further improve the preparation efficiency of flux, the preferred stirring time in this disclosure is 6-20 minutes, for example, but not limited to 6 minutes, 8 minutes, 10 minutes, 12 minutes, 14 minutes, 16 minutes, 18 minutes, and 20 minutes.

[0069] Specifically, the stirring speed is not specifically limited, as long as the components are stirred evenly. To improve the uniformity of the components, the stirring speed should not be less than 60 r / min. To avoid splashing of the components during stirring, the preferred stirring speed in this disclosure is 70-200 r / min, such as, but not limited to, 70 r / min, 90 r / min, 110 r / min, 130 r / min, 150 r / min, 170 r / min, and 200 r / min.

[0070] Thirdly, a metal-coated component is provided, the metal-coated component comprising a metal and the flux coated on at least a portion of the surface of the metal.

[0071] In some embodiments, the preparation method includes coating the flux onto at least a portion of the surface of a metal to obtain a metal-coated component.

[0072] Specifically, there are no specific restrictions on the method of flux application, as long as the flux can be evenly applied to the metal, such as thermal spraying or electrostatic spraying.

[0073] Specifically, the temperature of the thermal spraying is known to those skilled in the art. For example, the temperature of the thermal spraying is 80-130℃, and may be, but is not limited to, 80℃, 82℃, 85℃, 87℃, 90℃, 93℃, 95℃, 98℃, 100℃, 103℃, 105℃, 107℃, 110℃, 112℃, 115℃, 118℃, 120℃, 123℃, 125℃, 128℃, or 130℃.

[0074] Specifically, the voltage of the electrostatic coating is known to those skilled in the art, for example, it can be 40-135kV, specifically, but not limited to, 40kV, 42kV, 45kV, 47kV, 50kV, 53kV, 55kV, 58kV, 60kV, 65kV, 70kV, 75kV, 80kV, 85kV, 90kV, 95kV, 100kV, 105kV, 110kV, 115kV, 120kV, 125kV, 130kV, and 135kV.

[0075] In some embodiments, the flux is applied to at least a portion of the metal surface by simultaneous spraying and baking.

[0076] This disclosure combines spraying with baking, thus solving the problem that when the organic content in the flux is low, the flux liquid agglomerates into droplets after being sprayed onto the metal surface, resulting in uneven flux coating.

[0077] In addition, metal-coated parts can be made in one of the following forms: strips, filaments, washers, bars, rings, sheets and other preforms.

[0078] Fourthly, a brazing method using a prepared metal-coated component is provided, comprising the steps of: assembling at least one prepared metal-coated component with at least one metal component, and brazing the assembly.

[0079] As described above, metal-coated parts can be brazed, a joining process in which two or more metal articles are joined together by melting and flowing a brazing material (which may be a metal or a metal alloy) into a joint defined between the metal articles. More specifically, brazing is performed by heating the metal-coated parts and the metal articles in an assembly manner with respect to a temperature (referred to herein as the “brazing temperature”) at which the metal or metal alloy in the metal-coated parts (referred to herein as the “brazing material”) melts while the parts to be joined remain undried. After subsequent cooling, the brazing material forms brazing fillets that bond the metal articles together at their mating surfaces.

[0080] Depending on the specific materials of the metal parts to be brazed together, the brazing material in the metal-coated part can include any conventional brazing material. In embodiments, the brazing material includes silicon-containing materials, such as alloys of silicon and metals, which serve as brazing materials. In one embodiment, the metal-coated part is used to braze aluminum articles together, and the brazing material includes an Al-Si alloy or its precursor as the brazing material. The Al-Si alloy may optionally include additional elements for alloying and / or providing corrosion protection. Such additional elements include, but are not limited to, zinc, bismuth, strontium, germanium, and / or tin. An example of a suitable brazing material for joining aluminum articles is an Al-Si eutectic composition that melts at about 577°C.

[0081] It should be understood that in other implementations, depending on the chemical composition of conventional brazing materials, different alloys may be used instead of silicon-containing materials, such as, but not limited to, any combination of zinc, aluminum, tin, silver, copper, or nickel.

[0082] These components can also be joined by laser brazing. This method is described in US2003 / 0178399. Preferably, instead of laser brazing, the components to be brazed are heated using the CAB (Controlled Atmosphere Brazing) method. This method is carried out in a closed system that prevents unwanted atmospheres (such as air) from contacting the components during the brazing process and for a desired time before and after brazing.

[0083] These components can also be connected by induction brazing, for example, by the induction brazing methods described in CN102909449A and CN102985207A.

[0084] Brazing is performed at a temperature higher than the melting point of the flux and the brazing metal, and sufficiently high to form a solid bond. Preferably, the brazing temperature is equal to or higher than 410°C, very preferably equal to or higher than 420°C. Preferably, the brazing temperature is lower than or equal to 680°C, more preferably equal to or lower than 650°C, and particularly preferably equal to or lower than 630°C. In the case of vacuum brazing, these temperatures may be even lower than those for brazing in the presence of gas.

[0085] Fifthly, a brazed assembly is provided, which is obtained by a brazing method using the metal-coated component described above. For example, an assembled component made of aluminum (including aluminum alloys) and copper (including copper alloys) components, wherein the aluminum and copper components are joined together by brazing in the presence of a flux or metal-coated component. Such components are available according to the method described above. The term "assembled component" includes sandwich structures useful for the construction of machines, vehicles, or buildings. For example, components made of aluminum and copper can be used in shipbuilding, offshore industries, space transportation systems, and devices and machines for the medical industry. Components made of aluminum and copper can be used, for example, in the manufacture of heat exchangers, such as automotive radiators, IGBT module radiators, and air conditioners (e.g., in stationary refrigerators, like the freezer compartment), and especially for portable air conditioners. Brazed components of aluminum and copper can also be used for purposes where contact with corrosive chemicals occurs, such as in storage tanks for chemical substances, or in pipes or devices for the chemical industry, such as reactors for chemical reactions.

[0086] The sixth aspect provides the application of the aforementioned metal-coated components in the brazing of power batteries and energy storage batteries; such as the welding of liquid cooling plates, filling ports, tabs, terminals, electrode terminals, and cover plates of power batteries and energy storage batteries.

[0087] To further understand this application, the following detailed description, in conjunction with specific embodiments, illustrates a flux, its preparation method, and its application. Unless otherwise specified, all raw materials involved in this application are commercially available.

[0088] The raw materials used in the embodiments and comparative examples are described below, but are not limited to these materials:

[0089] Table 1

[0090] name Performance parameters Brand factory Self-crosslinking acrylic emulsion 1 The glass transition temperature is 0℃ LA-6162A Zhaoqing Xinguangli Chemical Industry Co., Ltd. Self-crosslinking acrylic emulsion 2 The glass transition temperature is 28℃ XK-919 Covestro Self-crosslinking acrylic emulsion 3 The glass transition temperature is 42℃ XK-252 Covestro Self-crosslinking polyurethane emulsion 1 The minimum film-forming temperature is -5℃ F0415 Shenzhen Yoshida Chemical Co., Ltd. Self-crosslinking polyurethane emulsion 2 The minimum film-forming temperature is 0℃ TK2109 Dongguan Taikang Polymer Technology Co., Ltd. Self-crosslinking polyurethane emulsion 3 The minimum film-forming temperature is 5℃ 55 Guangzhou Ruilin New Materials Co., Ltd. Polyvinylpyrrolidone The weight-average molecular weight is 10,000. Aladdin Polyacrylic acid The viscosity-average molecular weight is 3 million. Guangdong Wengjiang Chemical Reagent Co., Ltd.

[0091] Examples and Comparative Examples

[0092] The components and weight parts of the fluxes described in the examples and comparative examples are shown in Table 2.

[0093] The flux preparation method described in the examples and comparative examples includes the following steps:

[0094] Weigh the activator, self-crosslinking acrylic emulsion, self-crosslinking polyurethane emulsion, and solvent according to the weight proportions in Table 2; stir the self-crosslinking acrylic emulsion, self-crosslinking polyurethane emulsion, and solvent at 100 r / min for 10 min, then add the activator and stir at 60 r / min for 10 min to obtain the flux.

[0095] Table 2

[0096]

[0097] Example 14

[0098] This embodiment provides a flux. The only difference between the flux in this embodiment and that in embodiment 6 is that self-crosslinking acrylic emulsion 2 is used instead of self-crosslinking acrylic emulsion 1. All other components and amounts are the same as in embodiment 6.

[0099] Example 15

[0100] This embodiment provides a flux. The only difference between the flux in this embodiment and that in embodiment 6 is that self-crosslinking acrylic emulsion 3 is used instead of self-crosslinking acrylic emulsion 1. All other components and amounts are the same as in embodiment 6.

[0101] Example 16

[0102] This embodiment provides a flux. The only difference between the flux in this embodiment and that in embodiment 6 is that self-crosslinking polyurethane emulsion 2 is used instead of self-crosslinking polyurethane emulsion 1. All other components and amounts are the same as in embodiment 6.

[0103] Example 17

[0104] This embodiment provides a flux. The only difference between the flux in this embodiment and that in embodiment 6 is that self-crosslinking polyurethane emulsion 1 is replaced with self-crosslinking polyurethane emulsion 3, while the other components and amounts are the same as in embodiment 6.

[0105] Example 18

[0106] This embodiment provides a flux comprising the following components in parts by weight: 100 parts activator, 120 parts water, 1.5 parts self-crosslinking acrylic emulsion, 0.5 parts self-crosslinking polyurethane emulsion, and 0.4 parts diethanolamine;

[0107] The flux preparation method in this embodiment is the same as that in Example 6.

[0108] Performance testing

[0109] The performance of the fluxes obtained in the test examples and comparative examples was analyzed, and the test methods for each performance are as follows:

[0110] 1. Coating adhesion: The flux obtained in the examples and comparative examples was coated onto AlSi12 preformed solder sheets with dimensions of 10mm*25mm*0.2mm in the same manner, with a flux coating amount of 10%±1%, to obtain coated sheets; 50g±0.2g of coated sheets were placed in the same position in a vibratory feeder; the sheets were fed 12 times under the same parameters, and the mass of the coated sheets after 12 feedings was weighed. The powder shedding rate of the coated sheets was calculated. The formula for calculating the powder shedding rate of the coated sheets is: Powder shedding rate of coated sheets = (Amount of flux coated before feeding - Amount of flux coated after feeding) ÷ Amount of flux coated before feeding; The smaller the powder shedding rate of the coated sheets, the better the scratch resistance and adhesion performance of the coated sheets.

[0111] 2. Welding performance, welding fume output, and black residue

[0112] The flux obtained from the examples and comparative examples was applied to a ZnAl10 preformed solder sheet with dimensions of 11mm × 11mm × 0.2mm. The amount of flux applied was 8% ± 0.5%, resulting in a coated sheet.

[0113] The coated sheet was heated for 5 seconds at a temperature 40°C higher than the melting point of the activator, and pure copper was welded to a 3003 aluminum part. Five of each type of coated sheet were welded, and then the weld void rate was detected by an ultrasonic scanner. The average void rate of the five samples was recorded as the weld void rate.

[0114] During the welding process, an explosion-proof dust meter was used to measure the smoke size 10cm above the welding sheet. Five measurements were taken for each flux, and the average value was taken. The average smoke concentration generated when only the activator was used as the baseline value. The average smoke concentration of each flux divided by the baseline value was the amount of welding smoke, which is the relative smoke size.

[0115] Place five coated sheets on a pure copper plate, without placing any other items on top, and heat for 5 seconds at a temperature 40°C higher than the melting point of the surfactant. Observe whether there is any black residue.

[0116] 3. Number of times guns were blocked

[0117] Under the same parameters, spray continuously with a spray gun with a nozzle diameter of 1.2mm. Start spraying and start timing. If the gun gets clogged within 30 minutes, it is counted as one time. Then clean the spray gun and pipes and spray again. Repeat this process for a total of 3 times and record the number of times the gun gets clogged. If there is no gun clog and you spray continuously for 1.5 hours without any clog, it is counted as 0 times.

[0118] 4. Number of sprays

[0119] Under the same parameters, one sweep of the spray gun across the weld sheet is counted as one spray, and the number of times required to spray the ZnAl10 preformed weld sheet to a coating content of 8% is recorded.

[0120] The test results are shown in Table 3.

[0121] Table 3

[0122]

[0123]

[0124] As can be seen from the experimental data in Table 3, the coating powder shedding rate of the flux disclosed herein is less than 4%, the welding void rate is less than 36.5%, and the welding smoke amount is less than 1.55, indicating that the flux disclosed herein has high coating firmness and welding performance as well as low smoke amount.

[0125] Comparing Examples 1-4 and Comparative Examples 1-2, it can be seen that a low solvent content in the flux will cause the flux to clog the spray gun during the spraying process, making it impossible to spray; while a high solvent content in the flux will lead to an increase in the number of spraying operations and the solder void rate.

[0126] Comparing Examples 4-6 and Comparative Examples 3-4, it can be seen that when the mass ratio of self-crosslinking acrylic emulsion to self-crosslinking polyurethane emulsion in the flux is 1.5-9, the resulting flux coating has a powder shedding rate of less than 0.3% and a weld void rate of less than 28.5%, indicating that within this range, the flux of this disclosure has higher coating firmness and welding performance.

[0127] Comparing Examples 6, 8-11, and 5-7, it can be seen that when the mass ratio of self-crosslinking acrylic emulsion to activator is 0.3-2, the resulting flux has a coating powder shedding rate of less than 2%, a weld void rate of less than 28.5%, and a welding smoke amount of less than 1.4, indicating that the flux has good overall performance in terms of coating firmness, welding performance, and welding smoke amount. When the mass ratio of self-crosslinking acrylic emulsion to activator is less than 0.3, the coating powder shedding rate is 11.315%, and the coating firmness is reduced. When the mass ratio of self-crosslinking acrylic emulsion to activator is greater than 2, the resulting flux has a weld void rate ≥49.5% and a welding smoke amount ≥1.45, indicating an increase in smoke amount and a decrease in welding performance.

[0128] When the mass ratio of self-crosslinking acrylic emulsion to activator is 1-1.8, the resulting flux has a welding void rate of less than 20% and a powder shedding rate of less than 1%. At this time, the flux has better overall performance in terms of coating firmness, welding performance, and welding fume emission.

[0129] Comparing Examples 6 and 12-13, it can be seen that alcohol / ether as a solvent reduces coating adhesion compared to water.

[0130] Comparative Examples 6 and 8-9 show that, compared with conventional binders, the self-crosslinking emulsion selected in this disclosure as a binder can further improve the coating adhesion and welding performance of the flux, as well as reduce the amount of welding fumes from the flux.

[0131] Finally, it should be noted that the above embodiments are used to illustrate the technical solutions of this disclosure and not to limit the scope of protection of this disclosure. Although this disclosure has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this disclosure without departing from the substance and scope of the technical solutions of this disclosure.

Claims

1. A flux, characterized in that, Includes surfactants, self-crosslinking emulsions, and solvents; The mass ratio of the self-crosslinking emulsion to the surfactant is 0.3-2:100; The mass ratio of the solvent to the surfactant is 0.8-2:1; The self-crosslinking emulsion includes a self-crosslinking acrylic emulsion and a self-crosslinking polyurethane emulsion; The mass ratio of the self-crosslinking acrylic emulsion to the self-crosslinking polyurethane emulsion is (1.5-9):1; The glass transition temperature of the self-crosslinking acrylic emulsion is ≤30℃; The minimum film-forming temperature of the self-crosslinking polyurethane emulsion is ≤0℃; The active agent is fluoroaluminate.

2. The flux as described in claim 1, characterized in that, The mass ratio of the self-crosslinking emulsion to the surfactant is (1-1.7):

100.

3. The flux as described in claim 1, characterized in that, The solvent is at least one of water, alcohol, and ether.

4. The flux as described in claim 3, characterized in that, The alcohol is at least one of ethanol, n-propanol, and propylene glycol; And / or, the ether is at least one of propylene glycol butyl ether, ethylene glycol butyl ether, propylene glycol methyl ether, ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, and dipropylene glycol dimethyl ether.

5. The method for preparing flux according to any one of claims 1-4, characterized in that, The process includes the following steps: First, the activator and solvent are stirred evenly, and then the self-crosslinking emulsion is added and stirred evenly to obtain the flux.

6. A metal-coated component, characterized in that, The metal coating component includes metal and a flux as described in any one of claims 1-4 coated on at least a portion of the surface of the metal.

7. The method for preparing the metal-coated component as described in claim 6, characterized in that, The preparation method includes coating at least a portion of the surface of a metal with the flux as described in any one of claims 1-4 to obtain a metal-coated component.

8. The preparation method according to claim 7, characterized in that, The flux is applied to at least a portion of the metal surface by simultaneous spraying and baking.

9. A brazing method using a metal-coated component as described in claim 6 or a metal-coated component prepared according to any one of claims 7-8, characterized in that, The method includes the following steps: assembling at least one metal-coated component with at least one metal component, and brazing the assembly; wherein the metal-coated component is the metal-coated component as described in claim 6, or the metal-coated component prepared as described in any one of claims 7-8.

10. A brazed assembly, characterized in that, The brazed assembly is obtained by the method of claim 9.

11. The application of the metal-coated component as described in claim 6 in the brazing of power batteries, energy storage batteries, and automotive radiators.

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