Soldering flux and preparation method and application thereof

Abstract

The invention provides scaling powder and a preparation method and application thereof, and belongs to the technical field of scaling powder. The scaling powder comprises an active agent and a carrier. Wherein the carrier is at least one alcohol and / or alkane which is solid at normal 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. The scaling powder does not need to use any liquid solvent, the carrier can improve the storage stability, the welding wettability, the welding binding force and the scratch resistance of the scaling powder, and meanwhile the residue content of the scaling powder is reduced.

Description

TECHNICAL FIELD

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

[0002] New energy vehicles powered by batteries are now rapidly developed and applied due to the advantages of no greenhouse gas emission, no pollution to the environment, high efficiency and low noise. The power battery is composed of a plurality of battery cells. Various welding is involved in the production and manufacturing process of the battery cell, and the welding requirement for sealing the liquid injection port is very high and difficult. The welding quality and yield directly relate to the quality and yield of the entire battery cell and power battery. In order to ensure the smooth progress of the welding process, a flux is usually used to remove the oxides on the surface of the solder and the welded product to achieve the necessary cleanliness of the metal surface, thereby improving the welding performance.

[0003] In the prior art, the flux generally exists in the form of solder paste or suspension. Although such flux has good weldability and low cost, it has the following shortcomings: first, when the preformed solder is coated with the flux, the coating is not uniform; second, in order to improve the firmness of the flux, the flux usually contains a large amount of adhesive. The adhesive not only causes a large amount of organic matter to decompose violently to generate gas and cause spatter during welding, but also leaves a large amount of black residue on the surface of the welded workpiece after welding. The residue can cause the performance of the battery to decrease, so the residue must be cleaned. This not only increases the production cost, but also the cleaning agent used usually contains trioxymethylene and fluorochlorinated compounds, which are severely polluting and banned; third, when the liquid injection port of the battery is welded and sealed, the flowability of the solder paste can cause the components of the solder paste to penetrate into the battery. In addition, a large amount of organic solvent volatilizes and organic matter decomposes during welding, which can cause various impurities to enter the battery, resulting in a decrease in the performance of the battery; fourth, the preformed solder has a large heat dissipation area. During welding, the solder paste can leave a large number of cavities and organic residue at the welding interface due to the high content of the flux in the solder paste, which affects the heat dissipation effect and the reliability after welding.

[0004] Therefore, in view of the above shortcomings of the prior art, it is urgent to provide a flux that is free of cleaning and residue after welding, has uniform coating, good welding performance and no residue. SUMMARY

[0005] The purpose of the present application is to overcome the shortcomings of the prior art and provide a flux and a preparation method and application thereof.

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

[0007] In a first aspect, a flux is provided, comprising an active agent and a carrier, and the flux does not contain a liquid solvent; wherein the carrier comprises at least one alcohol and / or alkane which 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; and the alcohol does not contain an enol.

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

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

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

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

[0012] In one embodiment, the polyhydric alcohol has a number of carbon atoms between adjacent hydroxyl groups >2.

[0013] In one embodiment, the alkane is a linear alkane.

[0014] In one embodiment, the linear alkane has a number of carbon atoms >30.

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

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

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

[0018] In a second aspect, a preparation method of the flux is provided, comprising the following steps: after the carrier is heated and melted, the active agent is added and stirred uniformly to obtain the flux.

[0019] 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.

[0020] In a fourth aspect, a preparation method of the metal-coated part is provided, comprising coating the flux on at least part of the surface of the metal to obtain the metal-coated part.

[0021] In one embodiment, 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 80wt% of the alkane.

[0022] In a fifth aspect, there is provided a brazing method using the metal coated component, comprising the steps of: assembling at least one of the metal coated components with at least one metal component, and brazing the assembly.

[0023] In a sixth aspect, there is provided a brazed assembly obtained from the brazing method using the metal coated component.

[0024] In a seventh aspect, there is provided the use of the metal coated component in the brazing of a battery and a heat sink.

[0025] Compared with the prior art, the present application has the following advantages:

[0026] 1. The present disclosure uses at least one alcohol and / or alkane which is solid at room temperature as a carrier medium for the flux, the alcohol and / or alkane has small density and surface tension, and stable chemical properties, can effectively wrap the active agent, improve the storage stability of the flux, and prolong the shelf life of the flux, while in the welding process, the carrier medium is almost completely volatilized, effectively reducing the organic residue; secondly, it does not contain liquid solvent at room temperature and normal pressure, effectively avoiding the pollution of the solvent to the coating equipment and its surrounding environment when coating the liquid, gel or paste flux on the metal component, and avoiding the corrosion of the active agent dissolved in the liquid solvent (especially water) to the metal component; thirdly, by melting the carrier and adding the active agent, stirring uniformly, and obtaining the flux in solid form after cooling, the carrier is in liquid form after melting, which can act as a dispersant, so that the active agent can be effectively dispersed in the carrier, and the carrier is in solid form after cooling, which can act as a binder, improving the scratch resistance of the flux, and improving the welding wettability and welding bonding force.

[0027] 2. The flux of the present disclosure does not need to use any liquid solvent, avoiding the penetration of the flux into the battery, affecting the performance of the battery, and also avoiding the vaporization of the solvent and the severe decomposition of the organic matter, reducing the waste of the flux. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 Appearance of the preformed soldering sheet obtained by electrostatic spraying for Examples 17-18. DETAILED DESCRIPTION

[0029] The advantages and features of the present disclosure and the method of achieving the same will be more readily understood by referring to the following detailed description of the embodiments with reference to the accompanying drawings. However, the present disclosure can be implemented in various other forms, and should not be interpreted as being limited to the embodiments set forth herein. The embodiments disclosed herein are provided so that the disclosure of the present disclosure will be thorough and complete, and will fully convey the scope of the present disclosure to those skilled in the art.

[0030] The terminology used in the specification is for the purpose of describing certain embodiments only and is in no way intended to limit the present disclosure. Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Any term that is defined in a general dictionary should be interpreted to have the same meaning in the context of the relevant art, and, unless explicitly defined otherwise, should not be interpreted to have an idealistic or overly formalistic meaning.

[0031] Unless otherwise defined, all terms used herein, including technical and scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. Any term that is defined in a general dictionary should be interpreted to have the same meaning in the context of the relevant art, and, unless explicitly defined otherwise, should not be interpreted to have an idealistic or overly formalistic meaning.

[0032] In a first aspect, the present disclosure provides a flux, comprising an active agent and a carrier, and 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℃, and the melting point of the alkane is 45-130℃; the alcohol does not contain an enol.

[0033] The present disclosure uses at least one alcohol and / or alkane that is solid at room temperature as a carrier medium for the flux. In a first aspect, the alcohol and / or alkane has a small density and surface tension, and is chemically stable and repels water, can effectively encapsulate the active agent, improve the storage stability of the flux, does not need to be stored in a sealed container, has a long storage time (can still be used after 2 years of storage), and at the same time, the carrier medium is almost completely volatilized during welding, effectively reducing the organic residue; in a second aspect, the flux does not contain a liquid solvent at room temperature and atmospheric pressure, effectively avoiding the pollution of the solvent to the coating equipment and its surrounding environment when the flux in the form of liquid, gel or paste is coated on the metal part, and at the same time, avoiding the corrosion of the metal part caused by the dissolution of the active agent in the liquid solvent (especially water); in a third aspect, by melting the carrier, adding the active agent, stirring uniformly, and then cooling to obtain the flux in solid form, the carrier is in liquid form after melting, can be used as a dispersant, so that the active agent can be effectively dispersed in the carrier, and the carrier is in solid form after cooling, can be used as an adhesive, improving the scratch resistance of the flux, and at the same time, improving the welding wettability and welding bonding force. The flux of the present disclosure does not need to use any liquid solvent, avoids the penetration of the flux into the battery, affects the performance of the battery, and at the same time, avoids the splash caused by the vaporization of the solvent and the violent decomposition of the organic matter, reduces the waste of the flux.

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

[0035] The melting point of the alkane can be, but is not limited to, 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, 100°C, 102°C, 105°C, 107°C, 110°C, 113°C, 115°C, 118°C, 120°C, 122°C, 125°C, 127°C, 130°C; preferably 55-95°C.

[0036] The melting point of the alcohol and / or alkane affects the performance of the flux. Alcohol with a melting point higher than 100°C and / or alkane with a melting point higher than 130°C can result in excessive residue of the flux, while alcohol with a melting point lower than 40°C and / or alkane with a melting point lower than 45°C can result in poor bonding of the flux, thus leading to poor scratch resistance and bonding of the flux, and meanwhile, it is not conducive to coating, thus leading to poor uniformity of the flux.

[0037] Specifically, the melting point of the alcohol and / or alkane in the present disclosure can be determined by using a differential scanning calorimeter (DSC), one example of which is a calorimeter sold by TA Instruments USA under the name TA-SDTQ600 Thermal Comprehensive Analyzer.

[0038] The determination scheme is as follows: place the alcohol and / or alkane sample in an aluminum flat-bottomed crucible, use an empty aluminum flat-bottomed crucible as a reference, perform an endothermic scanning measurement, the temperature is raised from 25°C to 150°C, the scanning rate is 5°C / min, use N2purging, the N2flow rate is 100 mL / min. The melting point of the alcohol and / or alkane is determined by the temperature of the endothermic peak.

[0039] As referred to herein, "alcohol" refers to a compound in which a hydrogen atom in a fatty alkane, alicyclic alkane or 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.

[0040] Specifically, the present disclosure preferably uses a fatty alcohol, which can be, but is not limited to, a fatty monohydric alcohol, a fatty dihydric alcohol.

[0041] In one embodiment, the alcohol is at least one of a monohydric alcohol, a polyhydric alcohol with a number of hydroxyl groups ≤3; for example, monohydric alcohol, dihydric alcohol and trihydric alcohol, as examples of monohydric alcohol include, but are not limited to, pentadecanol, hexadecanol, octadecanol, eicosanol, docosanol, tetracosanol, octacosanol, triacontanol, cyclododecanol, cyclotetradecanol; as examples of dihydric alcohol include, but are not limited to, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,12-dodecanediol, 1,14-tetradecanediol, 1,16-hexadecanediol, 1,18-octadecanediol.

[0042] In the present disclosure, the number of hydroxyl groups of the alcohol affects the stability of the flux. Compared with polyhydric alcohol, monohydric alcohol can not only improve the stability of the flux, but also improve the solder wetting property of the flux, reduce the solder voids, and further improve the solder joint strength.

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

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

[0045] In the present disclosure, the polyhydric alcohol with the number of carbon atoms between adjacent hydroxyl groups >2 can avoid the chain breaking decomposition caused by the dehydration of adjacent hydroxyl groups, reduce the content of the flux residue, and improve the solder joint strength of the flux.

[0046] As mentioned herein, "alkane" refers to an organic compound composed of only carbon and hydrogen elements. Examples of alkane include, but are not limited to, straight-chain alkane, cycloalkane.

[0047] Examples of alkane include, but are not limited to, docosane, tetracosane, hexacosane, octacosane, triacontane, dotriacontane, tetratriacontane, hexatriacontane, octatriacontane, pentacontane, hexacontane, heptacontane, nonadecylcyclohexane, cyclododecane, cyclopentadecane, cubane.

[0048] In an embodiment, the alkane is straight-chain alkane. Straight-chain alkane has high surface resistance, can effectively wrap the active agent, achieve electrostatic coating, and ensure no flux residue after soldering.

[0049] In an embodiment, the number of carbon atoms of the straight-chain alkane is >30, for example, but not limited to, 31, 32, 35, 37, 40, 42, 44, 46, 48, 50, and preferably 32-50. By setting the number of carbon atoms of the straight-chain alkane in this range, the coating uniformity and solder wetting property of the flux can be further improved during electrostatic coating, and the content of the flux residue can be reduced. When the number of carbon atoms of the straight-chain alkane is >50, the content of the flux residue can be increased.

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

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

[0052] When the mass of the carrier is 20wt%-50wt% based on the total mass of the flux, the carrier can improve the activity of the flux, improve the solder wetting and scratch resistance of the flux, and can reduce the residue content of the flux. When the mass of the carrier is less than 20wt%, the flux is not uniformly dispersed during the coating process, resulting in uneven coating, insufficient firmness of the coated flux, insufficient scratch resistance, and problems such as difficulty in transportation, automatic feeding, and clogging of the pickup tube during pickup; when the mass of the carrier exceeds 50wt%, not only will it cause the soldering performance of the flux to decrease, but it may also increase the residue of the flux.

[0053] In one embodiment, the flux does not contain detectable water. As used herein, the term "does not contain" means that the component referred to is not intended to be included in the composition, but can be present in trace amounts, such as in an amount below the detection limit using conventional diagnostic methods.

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

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

[0056] When the mass of the active agent is 50wt%-80wt% based on the total mass of the flux, the generation of voids can be inhibited and good solder wetting can be achieved.

[0057] Specifically, the content of the alkane in the carrier is selected according to the coating method of the flux.

[0058] 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 80wt% of alkane, such as 80wt%, 82wt%, 85wt%, 87wt%, 90wt%, 93wt%, 95wt%, 98wt%, 100wt%.

[0059] When the flux is applied to at least a part of the surface of the metal using electrostatic spraying, if the content of the alkane in the flux is too low, the active agent cannot be effectively coated, and the stability of the flux becomes poor, so that the uniformity of the flux coating is significantly reduced.

[0060] 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 12 , CsK2AlF6, and alkali metal zinc fluoroaluminate salts including 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. Typically the active agent and its 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 in, for example, 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 104822488A describes a flux based on alkali metal zinc fluoroaluminate of general formula K w Zn x Al y F z , wherein 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 active agent is preferably 80 μm or less, for example, the average particle size of the active agent 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 1-20 μm. When the average particle size of the active agent is within the above range, the active agent shows high reactivity with aluminum alloy, and improves the inhibition effect of the chemical reaction with oxygen; improves the solder wettability of the flux, thereby improving the soldering bonding force.

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

[0063] In one embodiment, the flux further comprises an auxiliary agent, the mass percentage of the auxiliary agent in the flux is not more than 2wt%, preferably, the mass percentage of the auxiliary agent in the flux is not more than 0.5wt%; more preferably, the flux does not contain the auxiliary agent.

[0064] In one embodiment, the auxiliary agent comprises adhesives, thickeners, thixotropic agents, solder metals, solder metal alloys, etc., which can be used alone or in combination.

[0065] The auxiliary agent can be added to the flux by mechanical mixing. Excessive content of the auxiliary agent can cause the overall performance of the flux to decline.

[0066] Examples of suitable adhesives include, but are not limited to, polyalkane, polyurethane, polymethacrylate, butyl rubber.

[0067] Examples of suitable thickeners include, but are not limited to, different varieties of cellulose ethers or different hydrolysis degrees of polyvinyl alcohol. Different varieties of cellulose ethers are, for example, referred to as methyl cellulose if they are methyl-substituted, as hydroxyethyl cellulose if they are hydroxyethyl-substituted, and as hydroxypropyl cellulose if they are hydroxypropyl-substituted.

[0068] The composition of the solder metal and / or solder metal alloy is not specifically limited, i.e. the flux of the present disclosure does not impair the generation of solderability voids and solder balls regardless of the composition of the solder metal and / or solder metal alloy used, and is able to ensure the uniformity of the flux coating, as well as to balance the low flux residue, solder wettability and scratch resistance.

[0069] 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.

[0070] The flux containing the solder metal and / or solder metal alloy described above is able to inhibit the cracking of the solder joint even in an environment with severe vibration load due to cold and warm differences.

[0071] In a second aspect, a preparation method of the flux is provided, comprising the following steps: heating and melting the carrier, then adding the active agent and stirring uniformly to obtain the flux.

[0072] Specifically, the temperature of the carrier heating is above the melting point of the carrier, so that the carrier is completely melted, such as can be 80-160℃, examples of the heating temperature include but are not limited to 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, 130℃, 135℃, 140℃, 145℃, 155℃, 160℃.

[0073] Specifically, the stirring time is not specifically limited, as long as the active agent and the carrier can be stirred uniformly, for example, can be 10-30min, examples of the stirring time include but are not limited to 10min, 12min, 14min, 16min, 18min, 20min, 22min, 24min, 26min, 28min, 30min.

[0074] Specifically, the stirring speed is not specifically limited, as long as the active agent and the carrier can be stirred uniformly, for example, can be 50-200r / min, specific examples of the stirring speed include but are not limited to 50r / min, 70r / min, 90r / min, 110r / min, 130r / min, 150r / min, 170r / min, 200r / min.

[0075] The flux of the present disclosure is very suitable for use in a method of pre-fluxing components intended for brazing. In such a pre-fluxing method, aluminium or aluminium alloy components and / or components to be brazed made of steel, copper or copper are coated with a carrier-containing flux article. These components, which can be, for example, fins or tubes to be assembled to form a heat exchanger or a coil intended to be converted into fins or tubes, can then be stored for a long period of time before brazing, if desired, or transported to the site of use. The flux coating obtained by applying the flux article of the present invention adheres very well to the surfaces of these components.

[0076] Accordingly, in a third aspect, there is provided a metal coated component, comprising a metal, the flux coated on at least part of the surface of the metal.

[0077] In a fourth aspect, there is provided a method of preparing the metal coated component, comprising coating the flux on at least part of the surface of the metal to obtain the metal coated component.

[0078] Specifically, the coating method of the flux is not specifically limited, as long as the flux can be uniformly coated on 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℃, specifically can be but not limited to 80℃, 82℃, 85℃, 87℃, 90℃, 93℃, 95℃, 98℃, 100℃, 103℃, 105℃, 107℃, 110℃, 112℃, 115℃, 118℃, 120℃, 123℃, 125℃, 128℃, 130℃.

[0080] In one embodiment, the flux is coated on at least part of the surface of the metal by electrostatic spraying, the carrier of the flux contains at least 80wt% of alkanes, such as 83wt%, 85wt%, 88wt%, 90wt%, 92wt%, 95wt%, 97wt%, 99wt%, 100wt% of alkanes.

[0081] When the flux is coated on at least part of the surface of the metal by electrostatic spraying, if the content of alkanes in the flux is too low, the active agent cannot be effectively wrapped, and the stability of the flux is poor, so that the uniformity of the coating of the flux is significantly reduced.

[0082] Specifically, the voltage of the electrostatic coating is known to those skilled in the art, for example, can be 40-135kV, specifically can be 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, 135kV.

[0083] In addition, the metal coated component can be made in one of the following forms: strip, tape, wire, gasket, rod, ring, sheet and other shapes of preformed solder.

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

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] The components can also be joined by induction brazing, such as the methods described in CN 102909449A, CN 102985207A.

[0090] The brazing is carried out 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 the case of vacuum brazing, these temperatures can even be lower compared to brazing in the presence of a gas.

[0091] In a sixth aspect, a brazed brazing assembly is provided, which is obtained using the brazing method of the metal coated part. For example, an assembled part made of parts of aluminum (including aluminum alloys) and parts of copper (including copper alloys), wherein the parts of aluminum 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 part" includes sandwich structures useful for the construction of machines, vehicles or buildings. For example, parts made of aluminum 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 aluminum and copper can be used for the manufacture of, for example, heat exchangers, such as air conditioners (for example in stationary refrigerators, like cold rooms), and especially for mobile air conditioners. Brazed parts of aluminum and copper can also be used for purposes in which contact with aggressive chemicals occurs, for example in tanks for chemical substances, or pipes or devices for the chemical industry, for example reactors for chemical reactions.

[0092] In a seventh aspect, the use of the metal coated part in the brazing of batteries and heat sinks is provided. Batteries that can be listed are the welding of liquid cooling plates, liquid injection ports, pole tabs, pole columns, electrode terminals, cover plates of power batteries and energy storage batteries; heat sinks that can be listed are the welding of automobile heat sinks, IGBT module heat sinks.

[0093] In order to further understand the present application, the present application of a flux and a 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 can be obtained by commercial purchase, unless otherwise specified.

[0094] Examples and comparative examples

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

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

[0097] The active agent, alcohol and / or alkane are weighed according to the weight parts in Table 1; after the alcohol and / or alkane is melted into a liquid state at a temperature of 80-160℃, the active agent is added, and stirred at a speed of 100 r / min for 30 min to obtain the flux.

[0098] Table 1

[0099]

[0100]

[0101]

[0102] The acrylic resin in Example 8 is a thermoplastic acrylic resin particle BR-116 of Mitsubishi, with a Tg of 50℃; the polyethylene in Comparative Example 7 is a linear low-density polyethylene particle LL-1002 of ExxonMobil, with a melting point of 120℃; and the Fischer-Tropsch wax in Comparative Example 8 is a white flaky particle LA-W70 of Lu'an Group, with a melting point of 65℃.

[0103] Performance test

[0104] 1. Scratch resistance and adhesion: the fluxes obtained in the examples and comparative examples are coated on AlSi12 preformed welding pieces with a size of 10mm*25mm*0.2mm in the same way, and the coating amount of the flux is 10%±1%, to obtain coated pieces; 50g±0.2g of the coated pieces are placed in a vibration disc at the same position; the feeding is carried out 12 times under the same parameters, the mass of the coated pieces after feeding is weighed, and the powder loss rate of the coated pieces is calculated, the calculation formula of the powder loss rate of the coated pieces is: 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.

[0105] 2. Organic matter residual rate:

[0106] 0.1g of the fluxes obtained in the examples and comparative examples are respectively placed on 6063 aluminum plates with a size of 5cm*5cm*0.1mm, heated at a temperature 40℃ higher than the melting point of the active agent for 5s, and whether there is black residue on the 6063 aluminum plate is observed; the mass reduction of the flux before and after each heating is recorded, each group of data is tested 10 times, and the average value is taken;

[0107] 0.6g of the active agent is respectively placed on 6063 aluminum plates with a size of 5cm*5cm*0.1mm, heated at a temperature 40℃ higher than the melting point of the active agent for 5s, and whether there is black residue on the 6063 aluminum plate is observed; the mass reduction of the active agent before and after each heating is recorded, each group of data is tested 10 times, and the average value is taken;

[0108] The residual rate of the organic matter was calculated according to the formula: residual rate of organic matter = residual amount of organic matter / mass of organic matter x 100%, wherein the mass of the organic matter refers to the mass of the carbon-containing organic matter in the flux, and the residual amount of the organic matter = mass of the organic matter - mass reduction of the flux - mass reduction of the active agent.

[0109] 3. Coating uniformity:

[0110] The fluxes obtained in the examples and comparative examples were coated on ZnAl10 preformed soldering sheets with a size of 11 mm x 11 mm x 0.2 mm, and the coating amount of the flux was 8% ± 0.5%, to obtain coated sheets;

[0111] The coated sheets were heated at a temperature 40°C higher than the melting point of the active agent for 5s, and pure copper and 3003 aluminum plates were welded, five for each coated sheet, and then the welding cavity rate was detected by an ultrasonic scanner, and the average cavity rate of the five samples was recorded as the welding cavity rate.

[0112] Ten pieces of each coated sheet were placed in a constant temperature and humidity chamber with a relative humidity of 85% and a temperature of 85°C, and after being placed for 7 days, 5 pieces were cleaned to remove the surface-coated flux, and the corrosion was observed to evaluate the storage capacity; the other 5 pieces were welded according to the welding conditions as described above, and the average cavity rate was recorded as the cavity rate after storage.

[0113] In the above performance tests, the coating methods were thermal spraying and electrostatic coating, the temperature of thermal spraying was 130°C, and the voltage of electrostatic coating was 135kV. Under the same conditions, uneven coating can easily lead to a larger welding cavity rate.

[0114] In the above performance tests, the coating amount of the flux was calculated according to the formula: coating amount of the flux = (weight of the alloy after coating - weight of the alloy before coating) / weight of the alloy before coating.

[0115] The performance test results are shown in Tables 2 and 3.

[0116] Table 2 Performance test results of thermal spraying

[0117]

[0118]

[0119] Table 3 Performance test results of electrostatic coating

[0120]

[0121] The alcohol content in the carriers of Examples 18-29 and Comparative Examples 2-4 was too high, and obvious unevenness was visible to the naked eye during electrostatic coating, so no performance test was performed. The flux obtained in Comparative Example 1 was obviously uneven to the naked eye during electrostatic coating, so no performance test was performed.

[0122] As can be seen from Table 2 and Table 3, the powder dropping rate of the coated sheet of the flux of the present disclosure is <6%, the organic residue rate is <2.5%, the welding cavity rate is <32%, and the cavity rate after storage is ≤35%, indicating that the flux of the present disclosure has good scratch resistance, welding bonding force, coating uniformity, and no organic residue.

[0123] As can be seen from Comparative Examples 3-7, the content of the carrier is ≥20wt% and the content of the active agent is ≥50wt% based on the total mass of the flux, the powder dropping rate of the coated sheet of the obtained flux is <0.5%, the organic residue rate is <1.5%, the welding cavity rate is <20%, and the cavity rate after storage is <20%, indicating that the flux of the present disclosure has better scratch resistance, welding bonding force, coating uniformity, and no organic residue.

[0124] As can be seen from Comparative Example 5 and Example 8, when other auxiliary agents are contained in the flux, the overall performance of the flux will decrease to a certain extent.

[0125] As can be seen from Comparative Example 5, 9-15, when the melting point of the alkane is 55-95℃, the powder dropping rate of the coated sheet of the obtained flux is <0.4%, the organic residue rate is <1.7%, the welding cavity rate is <15%, and the cavity rate after storage is <15%, indicating that the flux of the present disclosure has better scratch resistance, welding bonding force, coating uniformity, and no organic residue.

[0126] As can be seen from Comparative Example 5 and Examples 16-18, when the content of the alkane in the carrier is less than 80% during electrostatic coating, the obtained flux is not coated uniformly and cannot be welded.

[0127] As can be seen from Comparative Example 19-25, when the melting point of the alcohol is 50-90℃, the powder dropping rate of the coated sheet of the obtained flux is <1.2%, the organic residue rate is <1%, the welding cavity rate is <15%, and the cavity rate after storage is <15.5%, indicating that the flux of the present disclosure has better scratch resistance, welding bonding force, coating uniformity, and no organic residue.

[0128] As can be seen from Comparative Example 21 and Example 26, compared with dihydric alcohol, monohydric alcohol as the carrier, the obtained flux has better scratch resistance, welding bonding force, coating uniformity, and less organic residue.

[0129] As can be seen from Comparative Example 26-29, when the number of carbon atoms between adjacent hydroxyl groups in the polyhydric alcohol is 6-10, the obtained flux has better scratch resistance, welding bonding force, coating uniformity, and less organic residue.

[0130] From Comparative Examples 1-29 and Comparative Example 1, it can be seen that the flux of Comparative Example 1 is not uniformly coated when electrostatically sprayed, and when thermally sprayed, the coating sheet of the obtained flux has a powder drop rate of 14.265%, an organic matter residue rate of 36.3%, a welding cavity rate of 40.5%, a cavity rate after storage of 60.4%, and obvious corrosion, indicating that using a liquid solvent as a carrier of the flux can significantly degrade the overall performance of the flux.

[0131] Figure 1 The appearance of the preformed soldering sheet electrostatically sprayed for Examples 17-18 is shown in the figure, wherein the right figure is Example 17 and the left figure is Example 18. From the figure, it can be seen that the surface of the preformed soldering sheet of the left figure is not uniformly coated with flux, and cannot be used for soldering. Figure 1

[0132] Finally, it should be noted that the above examples are used to illustrate the technical solutions of the present application, and are not intended to limit the scope of protection of the present application. Although the present application 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 application can be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the present application.​

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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