Flux, and preparation method therefor and use thereof

Abstract

A flux, which comprises an active agent and a carrier, wherein the carrier is at least one alcohol and / or alkane which is solid at the room temperature; the melting point of the alcohol is 40-100°C, and the melting point of the alkane is 45-130°C; and the alcohol does not contain enol. The flux does not need to use any liquid solvent, and the carrier can improve the storage stability, welding wettability, welding bonding force and scratch resistance of the flux, and also reduces the residue content of the flux. The present invention further relates to a preparation method for the flux, a metal-coated component, a preparation method for the metal-coated component, a brazing method, a brazing assembly, and the use of the metal-coated component in the brazing of a battery and a radiator.

Description

A flux, its preparation method and application Technical Field

[0001] This disclosure relates to the field of welding technology, specifically to a 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. A power battery consists of several cells. The manufacturing process of these cells involves various welding processes, among which the welding of the electrolyte filling port is particularly demanding and difficult. The quality and yield of this welding directly affect the overall quality and yield of the cell and the power battery. To ensure the smooth progress of the welding process, flux is typically used to remove oxides from the solder and the surface of the products being welded, achieving the necessary cleanliness of the metal surface and thus improving welding performance.

[0003] In existing technologies, fluxes generally exist in the form of solder paste or suspension. While these fluxes offer good solderability and are low in cost, they have the following drawbacks: First, when pre-formed solder is coated with this flux, uneven coating is prone to occur. Second, to improve the flux's adhesion, it typically contains a large amount of binder. This binder not only causes significant gas decomposition and spattering during soldering due to the vigorous decomposition of organic matter, but also leaves a large amount of black residue on the workpiece surface after soldering. This residue can degrade battery performance; therefore, it must be cleaned. First, it increases production costs, and the cleaning agents commonly used contain prohibited substances such as trioxide and chlorofluorocarbons, which seriously pollute the environment. Second, when welding and sealing the battery filling port, the fluidity of the solder paste can cause its components to seep into the battery. At the same time, during the welding process, a large amount of organic solvents evaporate and organic matter decomposes, leading to various impurities entering the battery and causing a decline in battery performance. Third, the heat dissipation area of ​​the preformed solder is currently large. During welding, the high flux content in the solder paste can easily leave more voids and organic residues at the welding interface, affecting the heat dissipation effect and post-weld reliability.

[0004] 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 that has uniform coating, good soldering performance, and leaves no residue after soldering. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a flux, its preparation method and application.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] In a first aspect, a flux is provided, comprising an activator and a carrier, wherein the flux does not contain a liquid solvent; wherein the carrier comprises at least one alcohol and / or alkane that is solid at room temperature; the melting point of the alcohol is 40-100°C, and the melting point of the alkane is 45-130°C; the alcohol does not contain enols.

[0008] In one embodiment, the alcohol has a melting point of 50-90°C.

[0009] In one embodiment, the alkane has a melting point of 55-95°C.

[0010] In one embodiment, the alcohol is at least one of a monohydric alcohol and a polyhydric alcohol with ≤3 hydroxyl groups.

[0011] In one embodiment, the monohydric alcohol has 16-22 carbon atoms.

[0012] In one embodiment, the number of carbon atoms between adjacent hydroxyl groups of the polyol is >2.

[0013] In one embodiment, the alkane is a straight-chain alkane.

[0014] In one embodiment, the straight-chain alkane has >30 carbon atoms.

[0015] In one embodiment, the activator is a fluoroaluminate.

[0016] In one embodiment, the carrier content is ≥20 wt% based on the total mass of flux.

[0017] In one embodiment, the content of the activator is ≥50 wt% based on the total mass of the flux.

[0018] Secondly, a method for preparing the flux is provided, comprising the following steps: heating and melting the carrier, adding an activator and stirring evenly to obtain the flux.

[0019] 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.

[0020] Fourthly, a method for preparing the metal-coated component is provided, the method comprising coating the flux onto at least a portion of the surface of a metal to obtain the metal-coated component.

[0021] In one embodiment, the flux is applied to at least a portion of the surface of the metal using electrostatic spraying, wherein the flux carrier contains at least 80 wt% alkane.

[0022] Fifthly, a brazing method using the aforementioned metal-coated component is provided, comprising the steps of: assembling at least one of the aforementioned metal-coated components with at least one metal component, and brazing the assembly.

[0023] In a sixth aspect, a brazed assembly is provided, the brazed assembly being obtained by a brazing method using the metal-coated component described above.

[0024] In a seventh aspect, the application of the metal-coated component in the brazing of batteries and heat sinks is provided.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] 1. This disclosure uses at least one alcohol and / or alkane that is solid at room temperature as a carrier medium for flux. Firstly, alcohols and / or alkanes have low density and surface tension, and stable chemical properties, which can effectively encapsulate activators, improve the storage stability of flux, and extend the shelf life of flux. At the same time, during the welding process, the carrier medium almost completely evaporates, effectively reducing organic residues. Secondly, it does not contain liquid solvents under normal temperature and pressure conditions, effectively avoiding the pollution of coating equipment and its surrounding environment caused by solvents when coating liquid, gel, or paste fluxes on metal parts, and also avoiding the corrosion of metal parts by activators dissolved in liquid solvents (especially water). Thirdly, by melting the carrier, adding the activator, stirring evenly, and cooling, a solid form of flux is obtained. The carrier is in liquid form after melting, which can act as a dispersant, allowing the activator to be effectively dispersed in the carrier. The carrier is in solid form after cooling, which can act as a binder, improving the scratch resistance of the flux, as well as improving the welding wettability and welding bonding strength.

[0027] 2. The flux disclosed herein does not require the use of any liquid solvent, thus avoiding flux penetration into the battery interior and affecting battery performance. It also avoids solvent vaporization and violent decomposition of organic matter, reducing flux waste. Attached Figure Description

[0028] Figure 1 shows the appearance of the preformed weld sheets obtained by electrostatic spraying in Examples 17-18. Detailed Implementation

[0029] The advantages and features of this disclosure, as well as the methods for achieving said advantages and features, will be more readily understood by referring to the following detailed description of embodiments. However, this disclosure may be implemented in various other forms and should not be construed as limited to the embodiments set forth herein. The embodiments disclosed herein are provided so that this disclosure will be thorough and complete, and will fully convey the scope of this disclosure to those skilled in the art.

[0030] The terminology used in this specification is intended to describe certain embodiments only and should in no way limit this disclosure. Unless expressly used otherwise, singular expressions include the meaning of plural expressions.

[0031] Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. Any term defined in a comprehensive dictionary shall be interpreted as having the same meaning in the context of the relevant field and, unless expressly defined otherwise, shall not be interpreted as having an idealistic or overly formalistic meaning.

[0032] In a first aspect, this disclosure provides a flux comprising an activator and a carrier, wherein the flux does not contain a liquid solvent; wherein the carrier is at least one alcohol and / or alkane that is solid at room temperature; the melting point of the alcohol is 40-100°C, and the melting point of the alkane is 45-130°C; the alcohol does not contain enols.

[0033] This disclosure uses at least one alcohol and / or alkane, which is solid at room temperature, as a carrier medium for the flux. Firstly, alcohols and / or alkanes have low density and surface tension, are chemically stable, and repel water, effectively encapsulating the activator and improving the flux's storage stability. No sealed storage is required, allowing for long storage time (it can still be used after 2 years of storage). Simultaneously, during the soldering process, the carrier medium almost completely evaporates, effectively reducing organic residue. Secondly, it does not contain liquid solvents under normal temperature and pressure conditions, effectively avoiding the coating of liquids or gels onto metal parts. This invention avoids the pollution of coating equipment and its surrounding environment caused by solvents in solid or paste-like fluxes, and also avoids the corrosion of metal parts caused by activators dissolved in liquid solvents (especially water). Thirdly, by melting the carrier, adding the activator, stirring evenly, and then cooling, a solid form of flux is obtained. The carrier, in liquid form after melting, can act as a dispersant, allowing the activator to be effectively dispersed within the carrier. The carrier, in solid form after cooling, can act as a binder, improving the flux's scratch resistance, as well as its wettability and weld bonding strength. The flux disclosed herein does not require the use of any liquid solvents, preventing flux from penetrating into the battery and affecting battery performance. It also avoids splashing caused by solvent vaporization and violent decomposition of organic matter, reducing flux waste.

[0034] Specifically, the melting point of the alcohol can be, but is not limited to, 40°C, 42°C, 45°C, 48°C, 50°C, 52°C, 55°C, 57°C, 60°C, 63°C, 65°C, 68°C, 70°C, 73°C, 75°C, 78°C, 80°C, 82°C, 85°C, 87°C, 90°C, 92°C, 95°C, 97°C, or 100°C; preferably 50-90°C.

[0035] The melting point of the alkane can be, but is not limited to, 45℃, 48℃, 50℃, 52℃, 55℃, 57℃, 60℃, 63℃, 65℃, 68℃, 70℃, 73℃, 75℃, 78℃, 80℃, 82℃, 85℃, 87℃, 90℃, 92℃, 95℃, 97℃, 100℃, 102℃, 105℃, 107℃, 110℃, 113℃, 115℃, 118℃, 120℃, 122℃, 125℃, 127℃, or 130℃; preferably 55-95℃.

[0036] The melting point of alcohols and / or alkanes affects the performance of flux. Alcohols with a melting point above 100°C and / or alkanes with a melting point above 130°C will result in excessive flux residue, while alcohols with a melting point below 40°C and / or alkanes with a melting point below 45°C will result in poor flux adhesion, thus reducing the flux's scratch resistance and welding adhesion, and also hindering coating, leading to a decrease in flux coating uniformity.

[0037] Specifically, the melting points of alcohols and / or hydrocarbons in this disclosure can be determined using a differential scanning calorimeter (DSC), an example of which is a calorimeter sold by TA Inc. under the name TA-SDTQ600 Thermal Integrated Analyzer.

[0038] The determination procedure is as follows: Alcohol and / or alkane samples are placed in an aluminum flat-bottomed crucible, using an empty aluminum flat-bottomed crucible as a reference. Endothermic scanning measurements are performed, with the temperature increasing from 25℃ to 150℃ at a scan rate of 5℃ / min. N2 is used for purging at a flow rate of 100 mL / min. The melting point of the alcohol and / or alkane is determined from the temperature of the endothermic peak.

[0039] 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.

[0040] Specifically, this disclosure prefers fatty alcohols, which can be, but are not limited to, fatty monohydric alcohols and fatty dihydric alcohols.

[0041] In one embodiment, the alcohol is at least one of a monohydric alcohol and a polyhydric alcohol with ≤3 hydroxyl groups; for example, monohydric alcohols, dihydric alcohols, and trihydric alcohols. Examples of monohydric alcohols include, but are not limited to, pentadecyl alcohol, hexadecyl alcohol, octadecyl alcohol, eicosyl alcohol, dodecyl alcohol, octadecyl alcohol, triacontyl alcohol, cyclododecyl alcohol, and cyclopentadecanyl alcohol. Examples of dihydric alcohols include, but are not limited to, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-dodecanediol, 1,14-tetradecanediol, 1,16-hexadecanediol, and 1,18-octadecanediol.

[0042] In this disclosure, the number of hydroxyl groups in an alcohol affects the stability of the flux. Compared with polyols, monohydric alcohols can not only improve the stability of the flux, but also improve the welding wettability of the flux, reduce weld voids, and thus improve the welding bond strength.

[0043] In one embodiment, the monohydric alcohol has 16-22 carbon atoms, for example, but not limited to 16, 17, 18, 19, 20, 21, and 22. By setting the range of carbon atoms of the monohydric alcohol to this range, the solder wettability of the flux can be further improved and the flux residue content can be reduced.

[0044] In one embodiment, the number of carbon atoms between adjacent hydroxyl groups of the polyol is >2, such as 3-19, specifically but not limited to 3, 5, 7, 9, 11, 13, 15, 17, 19.

[0045] In this disclosure, selecting polyols with more than 2 carbon atoms between adjacent hydroxyl groups can avoid chain-breaking decomposition caused by the dehydration of adjacent hydroxyl groups, reduce the content of flux residues, and improve the welding bonding force of the flux.

[0046] As mentioned in this article, "alkane" refers to organic compounds composed of only carbon and hydrogen elements. Examples of alkanes include, but are not limited to, straight-chain alkanes and cycloalkanes.

[0047] Examples of alkanes include, but are not limited to, docosane, hexadecane, octadecane, triadecane, dodecane, tetradecane, hexadecane, octadecane, tetradecane, pentadecane, heptane, nonadecane, cyclohexane, cyclododecane, cyclopentadecane, and cubicane.

[0048] In one embodiment, the alkane is a straight-chain alkane, which has high surface resistance, can effectively encapsulate the activator, achieve electrostatic coating, and ensure that there is no flux residue after welding.

[0049] In one embodiment, the straight-chain alkane has a carbon number >30, for example, but not limited to 31, 32, 35, 37, 40, 42, 44, 46, 48, and 50, preferably 32-50. By setting the carbon number of the straight-chain alkane within this range, the uniformity of flux coating and solder wettability can be further improved during electrostatic coating, as well as the flux residue content can be reduced. When the carbon number of the straight-chain alkane is >50, the flux residue content may increase.

[0050] In one embodiment, the carrier content is ≥20wt%, such as 20wt%-50wt%, based on the total mass of the flux.

[0051] Specifically, based on the total mass of flux, the carrier content can be, but is not limited to, 20wt%, 22wt%, 25wt%, 27wt%, 30wt%, 33wt%, 35wt%, 40wt%, 42wt%, 45wt%, 47wt%, and 50wt%.

[0052] Based on the total mass of flux, when the carrier mass is 20wt%-50wt%, the carrier can improve the flux activity, enhance the flux's wettability and scratch resistance, and reduce flux residue. When the carrier mass is less than 20wt%, the flux is unevenly dispersed during the coating process, resulting in uneven coating, insufficient flux adhesion, and inadequate scratch resistance, leading to problems such as transportation difficulties, clogging of the pick-up tube during automatic feeding, and other issues. When the carrier mass exceeds 50wt%, it not only leads to a decrease in flux welding performance but may also increase flux residue.

[0053] In one embodiment, the flux is free of detectable water. As used herein, “free of” means that the components cited are not intended to be included in the composition but may be present in trace amounts (such as in amounts below the detection limit using conventional diagnostic methods).

[0054] In one embodiment, the content is ≥50wt% based on the total mass of flux, such as 50wt%-80wt%.

[0055] Specifically, based on the total mass of the flux, the content of the activator can be, but is not limited to, 50wt%, 53wt%, 55wt%, 58wt%, 60wt%, 62wt%, 65wt%, 67wt%, 70wt%, 73wt%, 75wt%, 78wt%, or 80wt%.

[0056] Based on the total mass of flux, when the mass of activator is 50wt%-80wt%, it can suppress void formation and provide good solder wettability.

[0057] Specifically, the alkane content in the carrier is selected based on the flux coating method.

[0058] The flux is applied to at least a portion of the surface of the metal using electrostatic spraying, wherein the flux carrier contains at least 80 wt% alkane, for example 80 wt%, 82 wt%, 85 wt%, 87 wt%, 90 wt%, 93 wt%, 95 wt%, 98 wt%, or 100 wt%.

[0059] When flux is applied to at least part of the surface of a metal using electrostatic spraying, if the alkane content in the flux is too low, it cannot effectively encapsulate the activator, and the stability of the flux deteriorates, resulting in a significant decrease in the uniformity of flux coating.

[0060] 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. 12 CsK2AlF6, 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.

[0061] 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.

[0062] Specifically, the average particle size of the active agent is obtained by laser particle size analyzer testing.

[0063] In one embodiment, the flux may further include additives, wherein the additives constitute no more than 2 wt% of the flux by mass, preferably no more than 0.5 wt% of the flux by mass; more preferably, the flux does not contain additives.

[0064] In one embodiment, the additives include binders, thickeners, thixotropic agents, solder metals, solder metal alloys, etc., which can be used alone or in combination.

[0065] 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.

[0066] Examples of suitable adhesives include, but are not limited to, polyolefins, polyurethanes, polymethacrylates, and butyl rubber.

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] Secondly, a method for preparing the flux is provided, comprising the following steps: heating and melting the carrier, adding an activator and stirring evenly to obtain the flux.

[0072] Specifically, the heating temperature of the carrier is above the melting point of the carrier, enough to completely melt the carrier. For example, it can be 80-160℃. Examples of heating temperatures include, but are not limited to, 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, 130℃, 135℃, 140℃, 145℃, 155℃, and 160℃.

[0073] Specifically, there is no specific limit to the stirring time, as long as the active agent and the carrier are stirred evenly. For example, it can be 10-30 minutes. Examples of stirring times include, but are not limited to, 10 minutes, 12 minutes, 14 minutes, 16 minutes, 18 minutes, 20 minutes, 22 minutes, 24 minutes, 26 minutes, 28 minutes, and 30 minutes.

[0074] Specifically, there is no specific limit to the stirring speed, as long as the surfactant and carrier are stirred evenly. For example, it can be 50-200 r / min. Specific examples of stirring speeds include, but are not limited to, 50 r / min, 70 r / min, 90 r / min, 110 r / min, 130 r / min, 150 r / min, 170 r / min, and 200 r / min.

[0075] The flux disclosed herein is well-suited for use in a method for pre-melting components intended for brazing. In this pre-melting method, aluminum or aluminum alloy components and / or components made of steel, copper, or copper to be brazed are coated with a flux article containing a carrier. These components can then be stored (if desired) for an extended period before brazing or transported to the place of use; these components may be, for example, fins or tubes to be assembled into a heat exchanger, or coils intended to be converted into fins or tubes. The flux coating obtained by applying the flux article of the present invention adheres very well to the surface of these components.

[0076] Therefore, in a third aspect, 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.

[0077] Fourthly, a method for preparing the metal-coated component is provided, the method comprising coating the flux onto at least a portion of the surface of a metal to obtain the metal-coated component.

[0078] 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.

[0079] 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℃.

[0080] In one embodiment, the flux is applied to at least a portion of the surface of the metal using electrostatic spraying, wherein the flux carrier contains at least 80 wt% alkanes, such as 83 wt%, 85 wt%, 88 wt%, 90 wt%, 92 wt%, 95 wt%, 97 wt%, 99 wt%, or 100 wt% alkanes.

[0081] When flux is applied to at least part of the surface of a metal using electrostatic spraying, if the alkane content in the flux is too low, it cannot effectively encapsulate the activator, and the stability of the flux deteriorates, resulting in a significant decrease in the uniformity of flux coating.

[0082] 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.

[0083] In addition, metal-coated parts can be made into one of the following forms: strips, bands, wires, washers, bars, rings, sheets and other shapes of preformed solder.

[0084] Fifthly, a brazing method using the aforementioned metal-coated component is provided, comprising the steps of: assembling at least one of the aforementioned metal-coated components with at least one metal component, and brazing the assembly.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] These components can also be connected by induction brazing, for example, by the induction brazing methods described in CN102909449A and CN102985207A.

[0090] 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.

[0091] Sixthly, 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 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.

[0092] The seventh aspect provides the application of the aforementioned metal-coated components in the brazing of batteries and radiators. Examples of batteries include the welding of liquid cooling plates, filling ports, tabs, terminals, electrode terminals, and cover plates of power batteries and energy storage batteries. Examples of radiators include the welding of automotive radiators and IGBT module radiators.

[0093] 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.

[0094] Examples and Comparative Examples

[0095] The components and weight parts of the fluxes described in the examples and comparative examples are shown in Table 1.

[0096] The flux preparation method described in the examples and comparative examples includes the following steps:

[0097] Weigh the activator, alcohol and / or alkanes according to the weight proportions in Table 1; melt the alcohol and / or alkanes into a liquid state at a temperature of 80-160℃, add the activator, and stir at a speed of 100r / min for 30min to obtain the flux.

[0098] Table 1

[0099] In Example 8, the acrylic resin was Mitsubishi's thermoplastic acrylic resin granules BR-116 with a Tg of 50°C. In Comparative Example 7, the polyethylene was ExxonMobil's linear low-density polyethylene granules LL-1002 with a melting point of 120°C. In Comparative Example 8, the Fischer-Tropsch wax was Lu'an Group's white flaky granules LA-W70 with a melting point of 65°C.

[0100] Performance testing

[0101] 1. Scratch resistance and 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 the coated sheet was placed in the same position in the vibratory feeder; the sheet was fed 12 times under the same parameters, and the mass of the coated sheet after 12 feedings was weighed, and the powder shedding rate of the coated sheet was calculated. The formula for calculating the powder shedding rate of the coated sheet is: Powder shedding rate of the coated sheet = (Fluoride coating amount before feeding - Fluoride coating amount after feeding) ÷ Fluoride coating amount before feeding; The smaller the powder shedding rate of the coated sheet, the better the scratch resistance and adhesion of the coated sheet.

[0102] 2. Organic matter residue rate:

[0103] Take 0.1g of the flux obtained in the examples and comparative examples and place it on a 6063 aluminum plate with a size of 5cm×5cm×0.1mm. Heat it for 5s at a temperature 40°C higher than the melting point of the activator. Observe whether there is black residue on the 6063 aluminum plate. Record the amount of flux mass reduction before and after each heating. Each set of data was tested 10 times and the average value was taken.

[0104] Take 0.6g of surfactant and place it on a 6063 aluminum plate with dimensions of 5cm×5cm×0.1mm. Heat it for 5s at a temperature 40℃ higher than the melting point of the surfactant. Observe whether there is black residue on the 6063 aluminum plate. Record the amount of mass reduction of surfactant before and after each heating. Each set of data was tested 10 times and the average value was taken.

[0105] The formula for calculating the organic residue rate is: Organic residue rate = Organic residue amount / Organic mass × 100%, where the organic mass refers to the mass of carbon-containing organic matter in the flux, and the organic residue amount = Organic mass - Flux mass reduction - Activator mass reduction.

[0106] 3. Coating uniformity:

[0107] 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.

[0108] 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 plate. Five of each type of coated sheet were welded. Then, the weld void rate was detected by an ultrasonic scanner, and the average void rate of the five samples was recorded as the weld void rate.

[0109] Ten pieces of each type of coated sheet were placed in a constant temperature and humidity chamber at 85% relative humidity and 85°C for 7 days. Five of the sheets were cleaned of the flux coating and the corrosion was observed to assess the storage capacity. The other five sheets were welded according to the welding conditions described above, and the average void rate was recorded as the void rate after storage.

[0110] In the above performance tests, the coating methods were divided into thermal spraying and electrostatic coating. The temperature for thermal spraying was 130℃, and the voltage for electrostatic coating was 135kV. Under the same conditions, uneven coating is more likely to lead to a higher weld void rate.

[0111] In the above performance tests, the formula for calculating the amount of flux applied is: Flux application amount = (Weight of alloy after coating - Weight of alloy before coating) / Weight of alloy before coating.

[0112] The performance test results are shown in Tables 2 and 3.

[0113] Table 2 Performance test results of thermal spraying

[0114] Table 3 Performance test results of electrostatic coating

[0115] The alcohol content in the carriers of Examples 18-29 and Comparative Examples 2-4 was too high, resulting in noticeable unevenness visible to the naked eye during electrostatic coating; therefore, no performance testing was conducted. The flux obtained in Comparative Example 1 also showed noticeable unevenness visible to the naked eye during electrostatic coating; therefore, no performance testing was conducted.

[0116] As shown in Tables 2 and 3, the flux of this disclosure has a coating powder shedding rate of <6%, an organic residue rate of <2.5%, a welding void rate of <32%, and a void rate of ≤35% after storage. This indicates that the flux of this disclosure has good scratch resistance, welding bond strength, coating uniformity, and no organic residue.

[0117] Comparative examples 3-7 show that, based on the total mass of flux, the carrier content is ≥20wt%, the activator content is ≥50wt%, the resulting flux coating has a powder shedding rate of <0.5%, an organic residue rate of <1.5%, a welding void rate of <20%, and a void rate of <20% after storage. This indicates that the flux disclosed herein has better scratch resistance, welding bond strength, coating uniformity, and no organic residue.

[0118] Comparing Examples 5 and 8, it can be seen that when the flux contains other additives, the overall performance of the flux will decrease to a certain extent.

[0119] Comparing Examples 5 and 9-15, it can be seen that when the melting point of alkane is 55-95℃, the resulting flux coating has a powder shedding rate of <0.4%, an organic residue rate of <1.7%, a weld void rate of <15%, and a void rate of <15% after storage. This indicates that the flux disclosed herein has better scratch resistance, weld bonding strength, coating uniformity, and no organic residue.

[0120] Comparing Examples 5 and 16-18, it can be seen that when the alkane content in the carrier is less than 80% during electrostatic coating, the flux coating is uneven and welding cannot be performed.

[0121] Comparative Examples 19-25 show that when the melting point of the alcohol is 50-90°C, the resulting flux coating has a powder shedding rate of <1.2%, an organic residue rate of <1%, a weld void rate of <15%, and a void rate of <15.5% after storage. This indicates that the flux disclosed herein has better scratch resistance, weld bonding strength, coating uniformity, and no organic residue.

[0122] Comparing Examples 21 and 26, it can be seen that, compared with diols, when monools are used as carriers, the resulting flux has better scratch resistance, better welding bond strength and coating uniformity, and less organic residue.

[0123] Comparative Examples 26-29 show that when the number of carbon atoms between adjacent hydroxyl groups in the polyol is 6-10, the resulting flux has better scratch resistance, welding bond strength, coating uniformity, and less organic residue.

[0124] Comparing Examples 1-29 with Comparative Example 1, it can be seen that the flux of Comparative Example 1 was unevenly coated during electrostatic spraying; during thermal spraying, the flux coating had a powder shedding rate of 14.265%, an organic residue rate of 36.3%, a welding void rate of 40.5%, and a void rate of 60.4% after storage, and there was also obvious corrosion. This indicates that using liquid solvent as a carrier for flux will significantly reduce the overall performance of flux.

[0125] Figure 1 shows the appearance of the preformed weld sheets obtained by electrostatic spraying in Examples 17-18, where the right figure is Example 17 and the left figure is Example 18. As can be seen from Figure 1, the flux coating on the surface of the preformed weld sheet in the left figure is uneven and cannot be used for welding.

[0126] Finally, it should be noted that the above embodiments are used to illustrate the technical solutions of the present invention and not to limit the scope of protection of the present invention. Although the present invention 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 the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A fluxing agent characterized by, The flux includes an active agent and a carrier, and the flux does not contain a liquid solvent; wherein the carrier includes at least one alcohol and / or alkane which is solid at room temperature; the melting point of the alcohol is 40-100 DEG C, and the melting point of the alkane is 45-130 DEG C; the alcohol does not contain an enol.

2. The flux according to claim 1, wherein The melting point of the alcohol is 50-90 DEG C.

3. The flux according to claim 1, wherein The melting point of the alkane is 55-95 DEG C.

4. The flux according to claim 1, wherein The alcohol is at least one of a monohydric alcohol and a polyhydric alcohol having ≤3 hydroxyl groups.

5. The flux according to claim 4, wherein the flux is characterized by The monohydric alcohol has 16-22 carbon atoms.

6. The flux according to claim 4, wherein The polyhydric alcohol has >2 carbon atoms between adjacent hydroxyl groups.

7. The flux according to claim 1, wherein The alkane is a linear alkane.

8. The flux according to claim 7, wherein The linear alkane has >30 carbon atoms.

9. The flux according to claim 1, wherein The active agent is a fluoroaluminate.

10. The flux according to claim 1, wherein The content of the carrier is ≥20 wt% based on the total mass of the flux.

11. The flux according to claim 1 or 10, wherein The content of the active agent is ≥50 wt% based on the total mass of the flux.

12. A method of producing the flux according to any one of claims 1 to 11, characterized by, The preparation method includes the following steps: heating and melting the carrier, then adding the active agent and stirring until uniform, to obtain the flux.

13. A metal coated part characterized by, The metal-coated component includes a metal, and a flux as claimed in any one of claims 1-11 coated on at least part of the surface of the metal.

14. The method of making a metal-coated component of claim 13, wherein, The preparation method includes coating a flux as claimed in any one of claims 1-11 on at least part of the surface of a metal, to obtain a metal-coated component.

15. The production method according to claim 14, wherein The flux is coated on at least part of the surface of the metal by electrostatic spraying, and the carrier of the flux contains at least 80 wt% of an alkane.

16. A brazing method using the metal coated part produced according to claim 13 or 14, characterized in that, The method includes the following steps: assembling at least one metal-coated component prepared by the method of claim 13 or 14 with at least one metal component, and brazing the assembly.

17. A brazed brazing assembly characterized by, The brazed assembly is obtained by the method of claim 16.

18. Use of the metal-coated component of claim 13 in brazing of batteries and heat sinks.

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