Low-residue flux, and preparation method therefor and use thereof

Abstract

The present disclosure relates to the technical field of welding, and provides a low-residue flux, and a preparation method therefor and a use thereof. The flux of the present disclosure comprises an active agent, a self-crosslinking emulsion and a solvent; the mass ratio of the self-crosslinking emulsion to the active agent is 0.3-2:100; the mass ratio of the solvent to 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. In the present disclosure, the self-crosslinking emulsion is added to the flux, thereby improving the coating adhesion and welding performance of the flux, and reducing welding fume and organic residues.

Description

Low-residue flux and preparation method and application thereof TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of welding, in particular to a low-residue flux and preparation method and application thereof. BACKGROUND

[0002] New energy vehicles powered by batteries have been rapidly developed and applied today due to their advantages such as no greenhouse gas emission, no pollution to the environment, high efficiency and low noise. The structure of the power battery injection port is complex, and the welding requirement is high and difficult. When the traditional solder paste is used to weld the power battery injection port, a large amount of organic matter is contained in the traditional solder paste, which easily causes the solder paste composition to penetrate into the battery. At the same time, a large amount of organic solvent volatilizes and organic matter decomposes and splashes during the welding process. On the one hand, various impurities enter the battery, causing the battery performance to decrease. On the other hand, the battery seal and the surrounding equipment are also polluted, increasing the cleaning difficulty. On the other hand, a large amount of smoke is generated, polluting the environment and causing adverse effects on the health of the operators. When using preformed solder, due to the large heat dissipation area of the preformed solder, the solder paste is easy to leave more cavities and organic matter residues at the welding interface due to the high content of flux in the solder paste, affecting the heat dissipation effect and post-weld reliability.

[0003] Therefore, in view of the deficiencies in the prior art, it is urgent to provide a no-clean low-residue flux with high coating firmness and welding performance, small amount of welding smoke and no residue after welding. SUMMARY

[0004] The present disclosure aims to overcome the deficiencies of the prior art and provides a low-residue flux and a preparation method and application thereof.

[0005] To achieve the above-mentioned purpose, the technical solution adopted by the present disclosure is as follows: the present disclosure provides a flux, which 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.

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

[0007] In some embodiments, the mass ratio of the self-crosslinking acrylic emulsion and 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℃.

[0009] In some embodiments, the self-crosslinking polyurethane emulsion has a minimum film formation temperature ≤ 0℃.

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

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

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

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

[0014] In a second aspect, a preparation method of the flux is provided, comprising the following steps: firstly stirring the active agent and the solvent uniformly, and then adding the self-crosslinking emulsion and stirring uniformly to obtain the flux.

[0015] In a third aspect, a metal coated part is provided, comprising a metal, and the flux coated on at least part of the surface of the metal.

[0016] In some embodiments, the preparation method comprises coating the flux on at least part of the surface of the metal to obtain the metal coated part.

[0017] In some embodiments, the flux is coated on at least part of the surface of the metal by simultaneous spraying and baking.

[0018] In a fourth aspect, a brazing method using the metal coated part or the prepared metal coated part is provided, comprising the following steps: assembling at least one metal coated part or the prepared metal coated part with at least one metal part, and brazing the assembly.

[0019] In a fifth aspect, a brazed assembly is provided, which is obtained by the method.

[0020] In a sixth aspect, the metal coated part is provided for brazing of power batteries, energy storage batteries, automobile radiators, IGBT module radiators.

[0021] Compared with the prior art, the beneficial effects of the present disclosure are: the present disclosure adds a self-crosslinking emulsion in the flux, in the first aspect, the self-crosslinking emulsion used by the present disclosure replaces the adhesive in the flux, thereby reducing the decomposition and spatter of organic matter in the welding process, so that after welding, the welding parts, welding equipment and clamps do not need to be cleaned; in the second aspect, the content of organic matter in the flux of the present disclosure is reduced, which further reduces the decomposition and smoke amount of organic matter in the welding process, and improves the safety and environmental protection; in the third aspect, the present disclosure uses self-crosslinking acrylic emulsion and self-crosslinking polyurethane emulsion as the self-crosslinking emulsion, the self-crosslinking acrylic is easy to connect with the hydroxyl group in the active agent during the film forming process, forming a coating to cover the metal surface, and the self-crosslinking polyurethane emulsion and the self-crosslinking acrylic emulsion work together to improve the adhesion of the flux to the metal and the welding performance, effectively avoiding the decrease of the coating firmness and welding performance of the flux. DETAILED DESCRIPTION

[0022] Fig. 1 is an ultrasonic scan diagram of the welding cavity rate of the flux of Example 10;

[0023] Fig. 2 is an ultrasonic scan diagram of the welding cavity rate of the flux of Comparative Example 5;

[0024] Fig. 3 is an example diagram before and after testing the coating firmness of Example 10;

[0025] Fig. 4 is a result diagram after testing the coating firmness of the flux of Comparative Example 10;

[0026] Fig. 5 is an example diagram before and after testing the coating firmness of the flux of Comparative Example 10.

[0027] DETAILED DESCRIPTION

[0028] In order to facilitate the understanding of the present disclosure, the present disclosure will be described more fully below. However, the present disclosure can be implemented in many different forms, and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure more thorough and comprehensive.

[0029] As used herein, the term:

[0030] "prepared from" is synonymous with "comprising". The terms "comprising", "including", "having" "with" or any other variation thereof, as used herein, are intended to cover a non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that comprises a listed element does not necessarily limit only those elements, but can include other elements not expressly listed or inherent to such composition, step, method, article, or apparatus.

[0031] The conjunctive term "comprising" encompasses the presence of unrecited elements or steps of claim limitations. If used in the claims, the transitional phrase "consisting of" shall be affixed to the end of that claim to mean that the claim is closed and that no materials outside of the claim limitations can be present. The transitional phrase "consisting essentially of" shall be affixed to the end of that claim to mean that the claim is closed and that unrecited materials outside of the claim limitations can be present, provided that the inventive effect of the claimed subject matter is not materially affected by the unrecited materials. When the phrase "consisting of appears in the body of a claim, it defines only the elements that are described in that clause; other elements are not excluded from the claim as a whole.

[0032] When equivalent, concentration, or other value or parameter is expressed in a range, a preferred range, or a series of upper preferred values and lower preferred values, it is to be understood that all ranges formed by any pair of any upper range limit or preferred value and any lower range limit or preferred value, even if the range is not expressly stated, are to be specifically disclosed. For example, if a range "1-5" is disclosed, then the described range is to be construed as including "1-4," "1-3," "1-2," "1-2 and 4-5," "1-3 and 5," etc. When numerical ranges are disclosed, unless otherwise stated, the range is intended to include all integers and fractions within the range.

[0033] In these embodiments, unless otherwise indicated, the parts and percentages are by mass.

[0034] "Mass parts" refers to a basic unit of measurement that represents the proportional relationship of the mass of multiple components, 1 part can represent any unit mass, such as 1 g, 2.689 g, etc. If we say that the mass parts of component A is a parts, and the mass parts of component B is b parts, it means that the mass ratio of component A to component B is a:b. Alternatively, it means that the mass of component A is aK, and the mass of component B is bK (K is an arbitrary number, indicating a multiple factor). It should not be misunderstood that, unlike mass parts, the sum of the mass parts of all components is not limited to 100 parts.

[0035] "and / or" is used to indicate one or both of the stated circumstances can occur, for example, A and / or B includes (A and B) and (A or B).

[0036] The present disclosure provides a flux, comprising 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; the self-crosslinking emulsion comprises a self-crosslinking acrylic emulsion and a self-crosslinking polyurethane emulsion.

[0037] Specifically, the mass ratio of the self-crosslinking emulsion and the active agent 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, 2:100; preferably (1-1.8):100.

[0038] Specifically, the mass ratio of the solvent and the active agent is 0.8-2:1, for example, can be, but is 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, 2:1.

[0039] The present disclosure adds a self-crosslinking emulsion to the flux, in the first aspect, the self-crosslinking emulsion used by the present disclosure replaces the adhesive in the flux, thereby reducing the decomposition and spatter of organic matter in the welding process, so that after welding, there is no need to clean the welding parts, welding equipment and fixtures; in the second aspect, the content of organic matter in the flux of the present disclosure is low, which reduces the content of organic matter in the flux, further reduces the decomposition and smoke amount of organic matter in the welding process, and improves the safety and environmental protection; in the third aspect, the self-crosslinking acrylic emulsion and the self-crosslinking polyurethane emulsion are used as the self-crosslinking emulsion in the present disclosure, the self-crosslinking acrylic is easy to connect with the hydroxyl group in the active agent during the film forming process, forming a coating to cover the metal surface, and the self-crosslinking polyurethane emulsion and the self-crosslinking acrylic emulsion work together to improve the adhesion of the flux to the metal and the welding performance, effectively avoiding the decline of the coating firmness and the welding performance of the flux.

[0040] In the present disclosure, the mass ratio of the self-crosslinking emulsion and the active agent affects the performance of the flux, if the mass ratio of the self-crosslinking emulsion and the active agent is less than 0.3:100, it will cause the decline of the coating firmness and the welding performance of the flux, in addition, it will also cause the flux to fall off during the coating process; if the mass ratio of the self-crosslinking emulsion and the active agent is greater than 2:100, it will cause the smoke amount generated during the welding process to be large, and the high residual amount of organic matter will cause the decline of the welding performance. The preferred mass ratio of the self-crosslinking emulsion and the active agent is 1-1.7:100, which can obtain a flux with high coating firmness and welding performance, and less welding smoke.

[0041] In the present disclosure, the mass ratio of the solvent and the active agent will also affect the use and performance of the flux, if the mass ratio of the solvent and the active agent is less than 0.8:1, the flux is easy to block the coating equipment during the coating process of the flux; if the mass ratio of the solvent and the active agent is greater than 2:1, it will increase the coating times of the flux, reduce the use efficiency of the flux, and possibly cause the decline of the welding performance of the flux.

[0042] In some embodiments, the mass ratio of the self-crosslinking acrylic emulsion and 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, 9:1.

[0043] In the present disclosure, the mass ratio of the self-crosslinking acrylic emulsion and the self-crosslinking polyurethane emulsion also affects the performance of the flux. Too much or too little content of the self-crosslinking polyurethane emulsion will cause the coating firmness of the flux to decrease.

[0044] In some embodiments, the glass transition temperature of the self-crosslinking acrylic emulsion is ≤30°C, 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, 30°C.

[0045] Specifically, the glass transition temperature of the self-crosslinking acrylic emulsion is determined according to the GB / T 27816 standard.

[0046] In some embodiments, the minimum film formation 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, 0°C.

[0047] When the glass transition temperature of the self-crosslinking acrylic emulsion is greater than 30°C or the minimum film formation temperature of the self-crosslinking polyurethane emulsion is greater than 0°C, the welding void rate will increase.

[0048] Specifically, the minimum film formation temperature of the self-crosslinking polyurethane emulsion is tested according to the GB / T 9267-2008 standard.

[0049] In one embodiment, the active agent is a fluoroaluminate salt, including potassium fluoroaluminate such as KAlF4, K2AlF5, K3AlF6, K2AlF5·H2O, cesium fluoroaluminate such as CsAlF4, Cs2AlF5, Cs3AlF6, cesium potassium fluoroaluminate such as KCs2Al3F 12CsK2AlF6, and alkali metal zinc fluoroaluminate salts such as KZnAlF6, K2ZnAlF7, KZn2AlF8, KZnAl2F9, CsZnAlF6, Cs2ZnAlF7, CsZn2AlF8, and CsZnAl2F9, and the like. Each of the foregoing can be amorphous and / or partially or completely in one or more XRD distinguishable phases. The active agents and their manufacture are generally 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 US 4,428,920, US 4,579,605, and US 5,968,288. US 3,951,328, US 6,221,129, or US 3,971,501 describe fluxes based on KAlF4 and K3AlF6. US 4,689,092 describes a flux based on potassium fluoroaluminate and cesium fluoroaluminate. CN 104822488 A describes a flux based on the general formula K w Zn x Al y F z CsZnAlF6, and alkali metal zinc fluoroaluminate salts such as KZnAlF6, K2ZnAlF7, KZn2AlF8, KZnAl2F9, CsZnAlF6, Cs2ZnAlF7, CsZn2AlF8, and CsZnAl2F9, and the like. Each of the foregoing can be amorphous and / or partially or completely in one or more XRD distinguishable phases. The active agents and their manufacture are generally 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 US 4,428,920, US 4,579,605, and US 5,968,288. US 3,951,328, US 6,221,129, or US 3,971,501 describe fluxes based on KAlF4 and K3AlF6. US 4,689,092 describes a flux based on potassium fluoroaluminate and cesium fluoroaluminate. CN 104822488 A describes a flux based on the general formula K

[0050] In one embodiment, the average particle size of the active agent is preferably 80 pm or less, for example, the average particle size of the active agent can be, but is not limited to, 1 pm, 3 pm, 5 pm, 7 pm, 10 pm, 12 pm, 15 pm, 17 pm, 20 pm, 23 pm, 25 pm, 28 pm, 30 pm, 32 pm, 35 pm, 37 pm, 40 pm, 43 pm, 45 pm, 48 pm, 50 pm, 52 pm, 55 pm, 57 pm, 60 pm, 63 pm, 65 pm, 68 pm, 70 pm, 72 pm, 75 pm, 78 pm, preferably 1 to 50 pm, and particularly preferably 1-20 pm. When the average particle size of the active agent is within the above range, the active agent shows high reactivity with aluminum alloy, and the inhibition effect of the chemical reaction with oxygen is improved; the soldering wettability of the flux is improved, thereby improving the soldering bonding force.

[0051] Specifically, the average particle size of the active agent is tested according to the GB / T 19077-2016 standard.

[0052] In one embodiment, the flux can further comprise an auxiliary agent, and the mass percentage of the auxiliary agent in the flux is not more than 0.5wt%, preferably, the mass percentage of the auxiliary agent in the flux is not more than 0.2wt%; more preferably, the flux does not contain the auxiliary agent.

[0053] In one embodiment, the fluxing agent includes a binder, a thickening agent, a thixotropic agent, a solder metal, a solder metal alloy, or the like, which can be used alone or in combination.

[0054] The fluxing agent can be added to the flux by mechanical mixing. If the content of the fluxing agent is too high, the overall performance of the flux can be degraded.

[0055] Examples of suitable binders include, but are not limited to, polyalkane, polyurethane, polymethacrylate, butyl rubber.

[0056] Examples of suitable thickening agents include, but are not limited to, different types of cellulose ethers or different hydrolysis degrees of polyvinyl alcohol. Different types of cellulose ethers are referred to as methyl cellulose if they are substituted by methyl groups, as hydroxyethyl cellulose if they are substituted by hydroxyethyl groups, and as hydroxypropyl cellulose if they are substituted by hydroxypropyl groups.

[0057] The components of the solder metal and / or solder metal alloy are not particularly limited. That is, the flux of the present disclosure does not impair the generation of solder voids and solder balls regardless of the components of the solder metal and / or solder metal alloy used, and can ensure the uniformity of the flux coating, as well as low flux residue, solder wettability, and scratch resistance.

[0058] Examples of components that can be used in the solder metal and / or solder metal alloy 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, Si.

[0059] The use of the flux containing the solder metal and / or solder metal alloy described above can suppress the cracking of the solder joint even in an environment with a large temperature difference and a severe vibration load.

[0060] In some embodiments, the solvent is at least one of water, an alcohol, and an ether.

[0061] As referred to herein, an "alcohol" refers to a compound in which a hydrogen atom in a fatty alkane, an aliphatic cyclic alkane, or an aromatic alkane side chain is replaced by a hydroxyl group, and the general structure is that a hydroxyl group is connected to one saturated sp3 hybridized carbon atom.

[0062] Specifically, the present disclosure preferably uses a fatty alcohol, which can be, but is not limited to, a fatty monohydric alcohol or a fatty dihydric alcohol.

[0063] In one embodiment, the alcohol is a fatty monohydric alcohol, and the number of carbon atoms in the fatty monohydric alcohol is ≤ 12. Specific examples of the fatty monohydric alcohol can be methanol, ethanol, n-propanol, isopropanol, n-butanol, and isobutanol. The present disclosure preferably uses n-propanol as the fatty monohydric alcohol.

[0064] In one embodiment, the alcohol is a fatty dihydric alcohol, and the number of carbon atoms in the fatty dihydric alcohol is ≤ 6, and specific examples of the fatty dihydric alcohol can be ethylene glycol, propylene glycol, trimethylethylene glycol, 1,3-butanediol, 2,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol; the present disclosure preferably propylene glycol as the fatty dihydric alcohol.

[0065] In one embodiment, the ether is at least one of propylene glycol monobutyl ether, ethylene glycol monobutyl ether, propylene glycol methyl ether, ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, dipropylene glycol dimethyl ether.

[0066] Specifically, the present disclosure preferably water as the solvent, and water has better solubility and dispersibility for the active agent and the self-crosslinking emulsion compared with alcohol and / or ether, in addition, water is inorganic, non-toxic, environmentally friendly and safe, and has lower cost.

[0067] In a second aspect, a preparation method of the flux is provided, which comprises the following steps: firstly, stirring the active agent and the solvent uniformly, and then adding the self-crosslinking emulsion and stirring uniformly to obtain the flux.

[0068] In the preparation process of the flux of the present disclosure, the self-crosslinking emulsion and the active agent cannot be mixed first or simultaneously, if the self-crosslinking emulsion and the active agent are mixed first or simultaneously, the active agent will absorb the solvent in the self-crosslinking emulsion, which leads to that the self-crosslinking emulsion cannot be self-crosslinked or the degree of self-crosslinking of the self-crosslinking emulsion is reduced, thereby leading to that the firmness and the welding performance of the flux are reduced.

[0069] Specifically, the stirring time is not specifically limited, as long as the components can be stirred uniformly, in order to improve the uniformity of the components, the stirring time is greater than 5 min after each component is added; in order to further improve the preparation efficiency of the flux, the present disclosure preferably that the stirring time is 6-20 min, for example, but not limited to, 6 min, 8 min, 10 min, 12 min, 14 min, 16 min, 18 min, 20 min.

[0070] Specifically, the stirring speed is not specifically limited, as long as the components can be stirred uniformly, in order to improve the uniformity of the components, the stirring speed is not less than 60 r / min, in order to avoid splashing of the components during stirring, the present disclosure preferably that the stirring speed is 70-200 r / min, for example, but not limited to, 70 r / min, 90 r / min, 110 r / min, 130 r / min, 150 r / min, 170 r / min, 200 r / min.

[0071] In a third aspect, a metal coated part is provided, which comprises a metal, and the flux coated on at least part of the surface of the metal.

[0072] In some embodiments, the preparation method comprises applying the flux to at least part of the surface of the metal to obtain a flux-coated metal part.

[0073] Specifically, the flux can be applied to the metal in any manner known to those skilled in the art, such as thermal spraying or electrostatic spraying.

[0074] 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 can 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℃, 130℃.

[0075] Specifically, the voltage of the electrostatic spraying is known to those skilled in the art, for example, the voltage can be 40-135kV, and can be, but is 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, 135kV.

[0076] In some embodiments, the flux is applied to at least part of the surface of the metal by simultaneous spraying and baking.

[0077] The present disclosure solves the problem that when the content of organic matter in the flux is low, the flux liquid gathers into drops after being sprayed onto the surface of the metal, resulting in uneven application of the flux.

[0078] In addition, the flux-coated metal part can be made in one of the following forms: a strip, a wire, a gasket, a rod, a ring, a sheet, and other preformed parts.

[0079] In a fourth aspect, a brazing method using the flux-coated metal part prepared is provided, comprising the following steps: assembling at least one flux-coated metal part prepared with at least one metal part, and brazing the assembly.

[0080] As noted above, the metal-coated component can be used in brazing, which is a joining process in which two or more metal articles are joined together by melting and flowing a braze material (which can be a metal or metal alloy) into a joint defined between the metal articles. More specifically, brazing is performed by heating the metal-coated component and the metal component in an appropriately assembled manner with respect to temperature at which the metal or metal alloy in the metal-coated component (referred to herein as "braze material") melts while the metal articles to be joined to be joined remain un-melted. Upon subsequent cooling, the braze material forms a braze fillet that bonds the metal components together at their faying surfaces.

[0081] Depending on the particular materials of the metal components to be brazed together, the braze material in the metal-coated component can include any conventional braze material. In embodiments, the braze material includes a silicon-containing material as the braze material, such as an alloy of silicon and a metal. In one embodiment, the metal-coated component is used to braze aluminum articles together, and the braze material includes an Al-Si alloy or a precursor thereof as the braze material. The Al-Si alloy can 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. One example of a suitable braze material for joining aluminum articles is an Al-Si eutectic composition, which melts at about 577 °C.

[0082] It will be appreciated that in other embodiments, different alloys can be employed in place of the silicon-containing material, such as but not limited to alloys of any combination of zinc, aluminum, tin, silver, copper, or nickel, depending on the conventional braze material chemistry.

[0083] The components can also be joined by laser brazing. Such a method is described in US 2003 / 0178399. It is preferred that laser brazing is not performed, but that the components to be brazed are heated according to the CAB method (controlled atmosphere brazing). This method is performed in a closed device which can prevent an undesired atmosphere, such as air, from coming into contact with the components during the brazing process and for a desired period of time before and after the brazing.

[0084] The components can also be joined by induction brazing, such as the methods described in CN 102909449A, CN 102985207A.

[0085] The brazing is performed at a temperature above the melting point of the flux and of the brazing metal and sufficiently high to form a solid joint. 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 especially preferred the brazing temperature is equal to or lower than 630°C. In case of vacuum brazing, these temperatures can even be lower compared to brazing in the presence of a gas.

[0086] In a fifth aspect, a brazed brazing assembly is provided, obtained by the brazing method using the metal coated part. For example, assembled parts made of parts of aluminium (including aluminium alloys) and parts of copper (including copper alloys), wherein the parts of aluminium and copper are connected to each other by brazing in the presence of a flux or metal coated part. Such parts are obtainable according to the method described above. The term "assembled parts" includes sandwich structures useful for the construction of machines, vehicles or buildings. For example, parts made of aluminium and copper can be applied in the shipbuilding industry, the offshore industry, space transportation systems and devices and machines for the medical industry. Parts made of aluminium and copper can be used for the manufacture of, for example, heat exchangers, such as car radiators, IGBT module heat sinks, and air conditioners (for example in stationary refrigerators, like cold rooms), and especially for mobile air conditioners. Brazed parts of aluminium and copper can also be used for purposes where contact with aggressive chemicals occurs, for example in tanks for chemicals, or pipes or devices for the chemical industry, for example reactors for chemical reactions.

[0087] In a sixth aspect, the use of the metal coated part described for the brazing of power and energy storage cells is provided; such as the welding of liquid cooling plates, liquid injection ports, tab, pole, electrode terminals, cover plates of power and energy storage cells.

[0088] In order to further understand the present application, the present application of a flux and the preparation method and application thereof will be further described in detail below in conjunction with specific examples. The raw materials involved in the present application, unless otherwise specified, can be obtained by commercial purchase.

[0089] The raw materials used in the examples and comparative examples are described as follows, but are not limited to these materials:

[0090] Table 1

[0091] Examples and comparative examples

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

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

[0094] The active agent, the self-crosslinking acrylic emulsion, the self-crosslinking polyurethane emulsion and the solvent were weighed according to the parts by weight in Table 2; the self-crosslinking acrylic emulsion, the self-crosslinking polyurethane emulsion and the solvent were stirred at a rotation speed of 100 r / min for 10 min, then the active agent was added, and stirred at a rotation speed of 60 r / min for 10 min to obtain the flux.

[0095] Table 2

[0096] Example 14

[0097] The flux of the present example is different from the flux of Example 6 only in that the self-crosslinking acrylic emulsion 2 is used to replace the self-crosslinking acrylic emulsion 1, and the other components and amounts are the same as those of Example 6.

[0098] Example 15

[0099] The flux of the present example is different from the flux of Example 6 only in that the self-crosslinking acrylic emulsion 3 is used to replace the self-crosslinking acrylic emulsion 1, and the other components and amounts are the same as those of Example 6.

[0100] Example 16

[0101] The flux of the present example is different from the flux of Example 6 only in that the self-crosslinking polyurethane emulsion 2 is used to replace the self-crosslinking polyurethane emulsion 1, and the other components and amounts are the same as those of Example 6.

[0102] Example 17

[0103] The flux of the present example is different from the flux of Example 6 only in that the self-crosslinking polyurethane emulsion 3 is used to replace the self-crosslinking polyurethane emulsion 1, and the other components and amounts are the same as those of Example 6.

[0104] Example 18

[0105] The flux of the present example includes the following components in parts by weight: 100 parts of active agent, 120 parts of water, 1.5 parts of self-crosslinking acrylic emulsion 1, 0.5 parts of self-crosslinking polyurethane emulsion 1, and 0.4 parts of diethanolamine.

[0106] The preparation method of the flux of the present example is the same as that of Example 6.

[0107] Performance test

[0108] The performance of the fluxes obtained in the test examples and the comparative examples was tested, and the test method of each performance was as follows:

[0109] 1. Coating firmness: The fluxes obtained in the examples and comparative examples were coated on AlSi12 preformed solder pieces with dimensions of 10 mm*25 mm*0.2 mm in the same way, and the coating amount of the flux was 10%±1%, to obtain coated pieces; 50g±0.2g of the coated pieces were placed in the same position in a vibrating disc; the coated pieces were fed 12 times under the same parameters, the mass of the coated pieces after feeding 12 times was weighed, and the powder loss rate of the coated pieces was calculated, the calculation formula of the powder loss rate of the coated pieces was: powder loss rate of the coated pieces=(coating amount of the flux before feeding-coating amount of the flux after feeding) / coating amount of the flux before feeding; the smaller the powder loss rate of the coated pieces, the better the scratch resistance and adhesion of the coated pieces.

[0110] 2. Welding performance, welding smoke amount and black residue

[0111] The fluxes obtained in the examples and comparative examples were coated on ZnAl10 preformed solder pieces with dimensions of 11 mm*11 mm*0.2 mm, and the coating amount of the flux was 8%±0.5%, to obtain coated pieces.

[0112] The coated pieces were heated at a temperature 40°C higher than the melting point of the active agent for 5s, and pure copper and 3003 aluminum pieces were welded, five for each coated piece, and then an ultrasonic scanner was used to detect the welding cavity rate, and the average cavity rate of the five samples was recorded as the welding cavity rate.

[0113] During welding, an explosion-proof dust meter was used to measure the smoke size 10 cm above the solder piece, and each flux was measured five times to take the average value; the average smoke concentration generated by the active agent alone was taken as the reference value, and the average smoke concentration of each flux / reference value was the welding smoke amount, i.e. the relative size of the smoke.

[0114] Five coated pieces were placed on a pure copper plate without other objects on top, and heated at a temperature 40°C higher than the melting point of the active agent for 5s, and whether there was black residue was observed.

[0115] 3. Number of times of gun blockage

[0116] Under the same parameters, a spray gun with a nozzle diameter of 1.2 mm was used for continuous spraying, and the number of times of gun blockage was recorded, i.e. gun blockage once within 30 minutes from the start of spraying, then the spray gun and pipeline were cleaned and sprayed again, and the process was repeated three times; if there was no gun blockage and the spraying was continuous for 1.5 hours, the number of times of gun blockage was 0.

[0117] 4. Number of times of spraying

[0118] Under the same parameters, one spraying was defined as one scan of the spray gun on the solder piece, and the number of times of spraying required to coat the ZnAl10 preformed solder pieces to a content of 8% was recorded.

[0119] The test results are shown in Table 3.

[0120] Table 3

[0121] From the experimental data of Table 3, the powder falling rate of the soldering flux coated sheet of the present disclosure is less than 4%, the welding cavity rate is less than 36.5%, and the welding smoke amount is less than 1.55, indicating that the present disclosure has high soldering flux coating firmness and welding performance and low smoke amount.

[0122] From Comparative Examples 1-4 and Comparative Examples 1-2, it can be seen that a small amount of solvent in the soldering flux will cause the soldering flux to block the gun during spraying and cannot be sprayed; if the soldering flux contains a large amount of solvent, the spraying frequency and the welding cavity rate will increase.

[0123] From Comparative Examples 4-6 and Comparative Examples 3-4, it can be seen that when the mass ratio of the self-crosslinking acrylic emulsion and the self-crosslinking polyurethane emulsion in the soldering flux is 1.5-9, the soldering flux obtained has a powder falling rate of less than 0.3% and a welding cavity rate of less than 28.5%, indicating that the soldering flux of the present disclosure has higher coating firmness and welding performance in this range.

[0124] From Comparative Example 6, Examples 8-11 and Comparative Examples 5-7, it can be seen that when the mass ratio of the self-crosslinking acrylic emulsion and the active agent is 0.3-2, the soldering flux obtained has a powder falling rate of less than 2%, a welding cavity rate of less than 28.5%, and a welding smoke amount of less than 1.4, indicating that the soldering flux has good comprehensive performance in terms of coating firmness, welding performance and welding smoke amount; when the mass ratio of the self-crosslinking acrylic emulsion and the active agent is less than 0.3, the powder falling rate of the coated sheet is 11.315%, and the coating firmness is reduced; when the mass ratio of the self-crosslinking acrylic emulsion and the active agent is greater than 2, the welding cavity rate of the soldering flux obtained is greater than or equal to 49.5%, and the welding smoke amount is greater than or equal to 1.45, and the welding performance is reduced while the smoke amount increases.

[0125] When the mass ratio of the self-crosslinking acrylic emulsion and the active agent is 1-1.8, the soldering flux obtained has a welding cavity rate of less than 20% and a powder falling rate of less than 1%, and the soldering flux has better comprehensive performance in terms of coating firmness, welding performance and welding smoke amount.

[0126] From Comparative Example 6 and Examples 12-13, it can be seen that compared with water, alcohol / ether as a solvent will reduce the coating firmness.

[0127] From Comparative Example 6 and Comparative Examples 8-9, it can be seen that compared with conventional adhesives, the self-crosslinking emulsion selected as the adhesive of the present disclosure can further improve the coating firmness, welding performance of the soldering flux and reduce the welding smoke amount of the soldering flux.

[0128] Finally, it should be noted that the above examples are used to illustrate the technical solutions of the present disclosure and not to limit the protection scope of the present disclosure. Although the present disclosure has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present disclosure can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present disclosure.

Claims

A fluxing agent characterized in that, The active agent, the self-crosslinking emulsion and the solvent are mixed together. 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. The self-crosslinking emulsion comprises a self-crosslinking acrylic emulsion and a self-crosslinking polyurethane emulsion. The flux according to claim 1, wherein The mass ratio of the self-crosslinking emulsion and the active agent is (1-1.7):

100. The flux according to claim 1, wherein The mass ratio of the self-crosslinking acrylic emulsion and the self-crosslinking polyurethane emulsion is (1.5-9):

1. The flux according to claim 1, wherein The glass transition temperature of the self-crosslinking acrylic emulsion is ≤30℃. The flux according to claim 1, wherein The minimum film formation temperature of the self-crosslinking polyurethane emulsion is ≤0℃. The flux according to claim 1, wherein The active agent is a fluoroaluminate. The flux according to claim 1, wherein The solvent is at least one of water, alcohol, and ether. The flux according to claim 7, wherein The alcohol is at least one of ethanol, n-propanol, and propylene glycol. The ether is at least one of propylene glycol monobutyl ether, ethylene glycol monobutyl ether, propylene glycol methyl ether, ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, and dipropylene glycol dimethyl ether. The method of producing a flux according to any one of claims 1 to 8, characterized in that, The method comprises the following steps: firstly, stirring the active agent and the solvent uniformly, and then adding the self-crosslinking emulsion and stirring uniformly to obtain the flux. A metal coated component characterized in that, The metal coated component comprises a metal, and the flux as claimed in any one of claims 1-8 coated on at least part of the surface of the metal. The method of claim 10, wherein the metal coated part is prepared by The preparation method comprises coating the flux as claimed in any one of claims 1-8 on at least part of the surface of the metal to obtain a metal coated component. The production method as claimed in claim 11, characterized in that The flux is coated on at least part of the surface of the metal by simultaneous spraying and baking. A brazing method using the metal coated component as claimed in claim 10 or the metal coated component as prepared in any one of claims 11 to 12, characterized in that The method comprises the following steps: assembling at least one metal coated component with at least one metal component, and brazing the assembly; the metal coated component is the metal coated component as claimed in claim 10, or is the metal coated component prepared by the method as claimed in any one of claims 11-12. A brazed assembly, characterized in that The brazed assembly is obtained by the method as claimed in claim 13. The metal coated component as claimed in claim 10 is applied in brazing of power batteries, energy storage batteries, automobile radiators, and IGBT module radiators.

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