A coated solder and its preparation method and preparation device

Abstract

The present invention relates to the field of solder technology, and in particular, to a flux-coated solder and its preparation method and preparation device. The flux-coated solder comprises a solder core and a flux layer coated on the surface of the solder core; wherein the outer surface of the flux layer is coated with modified metal powder; or, the interior of the flux layer is mixed with the modified metal powder. The flux-coated solder provided by the present invention improves the performance of the solder and greatly reduces the difficulty of solder processing by coating the modified metal powder on the outer surface of the solder core. It avoids the problems of easy stratification, uneven composition of the finished solder, and broken cores caused by the large density difference between metal powder and flux powder in the prior art.

Description

Technical Field

[0001] The present invention relates to the technical field of solder, in particular to a coated solder and a preparation method and a preparation device thereof. Background Art

[0002] In some application fields that require high flow rate or toughness of solder, it is usually necessary to add low melting point elements or toughening elements to the solder. Although the addition of these elements will improve the performance of the solder, it will also make the processing of the solder difficult, because the addition of low melting point elements or toughening elements will cause the solder to be brittle and easy to break during processing, making it difficult to draw and reduce the diameter.

[0003] To address these issues, existing technologies employ metal-cored flux-cored brazing filler metals, which are composed of a mixture of metal powder containing a low-melting-point element or a strong element and flux powder, then encapsulated within a brazing filler metal coating. However, flux-cored brazing filler metals are prone to hollow cores or core breakage during the coiling process (e.g., Chinese invention patents CN112059474B and CN111992922B address this issue). Furthermore, the significant density difference between the metal powder and flux powder makes the coiling process more prone to delamination, ultimately leading to uneven composition and core breakage within the finished brazing filler metal.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The first object of the present invention is to provide a flux-coated solder to solve the problems of easy delamination, uneven composition of finished solder and easy core breakage in existing metal powder cored solder.

[0006] The second object of the present invention is to provide a method for preparing a coated solder.

[0007] The third object of the present invention is to provide a device for preparing coated solder.

[0008] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted:

[0009] The present invention provides a coated solder, comprising a solder core and a flux layer coated on the surface of the solder core;

[0010] Wherein, the outer surface of the flux layer is coated with modified metal powder; or, the interior of the flux layer is mixed with the modified metal powder.

[0011] Preferably, the modified metal powder includes at least one of Sn and its alloys, In and its alloys, Cd and its alloys, Ni and its alloys, Mn and its alloys, and Co and its alloys;

[0012] Preferably, the sum of the mass of the Sn element, In element, Cd element, Ni element, Mn element, and Co element in the modified metal powder accounts for more than 2% of the sum of the mass of the solder core and the modified metal powder;

[0013] Preferably, the content of oxygen in the modified metal powder is not greater than 1000 ppm.

[0014] Preferably, the solder core is mainly composed of copper-based solder and / or silver-based solder;

[0015] Preferably, the copper-based solder includes copper-zinc solder and / or copper-phosphorus solder;

[0016] Preferably, the shape of the solder core includes at least one of a filament, a strip, a sheet, a granule, a ring or a spring;

[0017] Preferably, at least one groove is provided on the outer surface of the solder core.

[0018] Preferably, the flux in the flux layer is mainly composed of the following components in parts by mass:

[0019] 50-70 parts of K2[(OH)F4B3O3], 10-20 parts of potassium fluoroborate, 10-20 parts of potassium tetraborate, 10-20 parts of boric acid, 5-20 parts of borax and 0.1-0.5 parts of boron powder.

[0020] Preferably, when the outer surface of the flux layer is coated with modified metal powder, optionally, the surface of the modified metal powder is also coated with a protective film layer;

[0021] Preferably, the protective film layer is mainly composed of boric acid.

[0022] Preferably, when the brazing flux layer is mixed with the modified metal powder, the brazing flux layer mainly consists of the brazing flux and the modified metal powder;

[0023] Preferably, the ratio of the particle size of the flux to the particle size of the modified metal powder is 1.4 to 1.7;

[0024] Preferably, the particle size of the flux is 100 to 170 μm;

[0025] Preferably, the particle size of the modified metal powder is 70-100 μm.

[0026] The present invention also provides a method for preparing the above-mentioned coated solder, comprising the following steps:

[0027] After coating the surface of the solder core with a solder flux, a solder flux layer is formed; after coating the surface of the solder flux layer with modified metal powder, the coated solder is obtained;

[0028] Alternatively, the surface of a brazing filler metal core is coated with a mixture containing the flux and the modified metal powder to obtain the coated brazing filler metal.

[0029] Preferably, after coating the modified metal powder, the method further comprises coating a protective film on the surface of the modified metal powder to form a protective film layer;

[0030] Preferably, in the process of coating the modified metal powder and coating the protective film, the coating includes spraying.

[0031] The present invention also provides a device for preparing the coated solder as described above, comprising a first wire feeding unit, a flux adhering unit, a coating unit, and a second wire feeding unit connected in sequence;

[0032] Wherein, the first wire feeding unit and the second wire feeding unit are used to transmit a continuous solder core;

[0033] The flux attachment unit is used to coat the flux on the surface of the solder core to form a flux layer;

[0034] The coating unit is used to coat the modified metal powder on the outer surface of the flux layer.

[0035] Preferably, the coating unit includes a powder spraying device;

[0036] Preferably, a protective film coating unit is further provided between the coating unit and the second wire feeding unit, and the protective film coating unit is used to coat a protective film on the surface of the modified metal powder to form a protective film layer;

[0037] Preferably, the protective film coating unit includes an atomizing coating device;

[0038] Preferably, a first drying unit is further provided between the coating unit and the protective film coating unit, and the first drying unit is used to fix the modified metal powder on the surface of the flux layer; and / or a second drying unit is further provided between the protective film coating unit and the second wire feeding unit, and the second drying unit is used to dry the protective film on the modified metal powder;

[0039] Preferably, a vibration unit and a recovery unit are further provided between the first drying unit and the protective film coating unit, wherein the vibration unit is used to separate the modified metal powder floating on the surface of the flux layer, and the recovery unit is used to recover the modified metal powder separated by the vibration unit; wherein the vibration unit is provided above the recovery unit, more preferably directly above the recovery unit;

[0040] Preferably, a shaping and sizing unit is further provided between the flux attachment unit and the coating unit, and the shaping and sizing unit is used to shape the flux layer formed after the flux coating;

[0041] Preferably, the first wire feeding unit is further connected to a wire drawing and reducing unit, and the wire drawing and reducing unit is used to reduce the diameter of the solder core.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] (1) The coated solder provided by the present invention, by coating the outer surface of the solder core with modified metal powder, not only improves the solder performance but also greatly reduces the difficulty of solder processing. This avoids the problems of easy delamination, uneven composition, and core breakage in the finished solder caused by the large density difference between the metal powder and the flux powder in the prior art.

[0044] (2) The coating solder provided by the present invention is modified by adding metal elements, wherein Sn, In, and Cd can reduce the melting point of the solder and improve the fluidity of the solder; Ni, Mn, and Co can improve the strength of the solder.

[0045] (3) The coated solder provided by the present invention can improve the adhesion strength of the solder and the modified metal powder by providing at least one groove, and can also increase the content of the solder and the modified metal powder in the solder, so as to facilitate the adjustment of the composition according to different usage requirements.

[0046] (4) The coated solder provided by the present invention can protect the modified metal powder by providing a protective film layer on the surface of the modified metal powder, prevent the modified metal powder from being oxidized, and also prevent the modified metal powder from falling off from the solder surface, thereby ensuring the stability of the modified metal powder content.

[0047] (5) The coated solder prepared by the method for preparing the coated solder provided by the present invention is not prone to delamination, uneven composition, and core breakage. Furthermore, the method has the advantages of simple operation, low processing difficulty, mild conditions, a short process flow, and suitability for mass production.

[0048] (6) The device for preparing the coated solder provided by the present invention has a simple structure and low processing difficulty, and can realize large-scale and continuous production of the coated solder. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0050] Figure 1 A schematic cross-sectional view of the coated solder provided by the present invention;

[0051] Figure 2 Another schematic cross-sectional view of the coating solder provided by the present invention;

[0052] Figure 3 Another schematic cross-sectional view of the coated solder provided by the present invention;

[0053] Figure 4 A schematic structural diagram of a device for preparing a coated solder provided by the present invention;

[0054] Figure 5 This is a schematic cross-sectional view of the solder core provided by the present invention.

[0055] Reference numerals:

[0056] 1- solder core; 2- flux layer; 3- modified metal powder; 4- protective film layer;

[0057] 100-wire drawing and reducing unit; 201-first wire feeding unit; 300-flux attachment unit; 400-shaping and sizing unit; 500-coating unit; 601-first drying unit; 700-vibration unit; 800-recovery unit; 900-protective film coating unit; 602-second drying unit; 202-second wire feeding unit. DETAILED DESCRIPTION

[0058] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. Those who do not specify specific conditions in the embodiments are carried out according to normal conditions or the conditions recommended by the manufacturer. Those whose reagents or instruments are not specified by the manufacturer are conventional products that can be purchased commercially.

[0059] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and therefore should not be construed as limitations on the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0060] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0061] In a first aspect, the present invention provides a coated solder, comprising a solder core 1 and a flux layer 2 coated on the surface (outer surface) of the solder core 1. The solder core 1 is made of solder, and the flux layer 2 is made of flux.

[0062] The outer surface of the flux layer 2 is coated (attached) with modified metal powder 3, such as Figure 1 or Figure 2 That is, the coating solder includes a solder core 1, a flux layer 2 and a modified metal powder 3 from the inside to the outside.

[0063] Alternatively, the interior of the flux layer 2 is mixed with the modified metal powder 3, such as Figure 3 That is, the coating solder comprises, from the inside to the outside, a solder core 1 and a flux layer 2 mainly composed of flux and modified metal powder 3.

[0064] The coated solder provided by the present invention, by coating the outer surface of the solder core 1 with modified metal powder 3, not only improves the solder's performance but also significantly reduces its processing difficulty. This avoids the problems of delamination, uneven composition, and core breakage in the finished solder caused by the large density difference between the metal powder and the flux powder in the prior art.

[0065] Preferably, the modified metal powder 3 includes at least one of Sn and its alloys, In and its alloys, Cd and its alloys, Ni and its alloys, Mn and its alloys, and Co and its alloys.

[0066] The modified metal powder 3 refers to metal powder or alloy powder containing a modifying element, and the modifying element includes at least one of Sn, In, Cd, Ni, Mn, and Co.

[0067] Among them, the addition of Sn, In, and Cd elements can lower the melting point of the solder and improve the fluidity of the solder; the addition of Ni, Mn, and Co elements can improve the strength of the solder.

[0068] In some specific embodiments of the present invention, the modified metal powder 3 can be any alloy containing Sn, In, Cd, Ni, Mn, Co that is commonly used in the prior art or can be purchased and has an elemental composition similar to that of the solder, such as CuSn alloy, AgSn alloy, CuIn alloy, AgIn alloy, CuCd alloy, AgCd alloy, CuNi alloy, AgNi alloy, CuMn alloy, AgMn alloy, CuCo alloy, AgCo alloy, etc., but is not limited thereto.

[0069] The modified metal powder 3 may also be made of a single metal such as at least one of metal Sn, metal In, metal Cd, metal Ni, metal Mn and metal Co.

[0070] Preferably, the sum of the masses of the Sn element, In element, Cd element, Ni element, Mn element, and Co element in the modified metal powder 3 accounts for more than 2% of the sum of the masses of the solder core 1 and the modified metal powder 3, including but not limited to any one of 2.1%, 2.5%, 2.8%, 3%, 3.5%, 4%, 4.5%, 5%, 6%, 7%, 8%, 9%, 10%, 12%, 15%, 18%, 20%, 25%, and 30%, or the range value between any two of them.

[0071] That is, the mass of the modifying elements (Sn, In, Cd, Ni, Mn, Co) in the modified metal powder 3 accounts for 2% or more of the total mass of the modified metal powder 3 and the brazing material core 1 .

[0072] In the prior art, when the metal powder content in the solder exceeds 2%, the solder becomes difficult to process due to its brittleness. The present invention addresses this problem by coating the outer surface of the solder core 1 with modified metal powder 3, enabling the processing of solders with high Sn and Ni contents. In other words, the Sn and Ni contents in the coated solder provided by the present invention are not subject to any restrictions and can be adjusted according to actual needs, broadening the range of solders available.

[0073] Preferably, the oxygen content in the modified metal powder 3 is not greater than 1000 ppm, including but not limited to any one of 900 ppm, 800 ppm, 700 ppm, 600 ppm, 500 ppm, 400 ppm, 300 ppm, 200 ppm, 100 ppm, 50 ppm, 30 ppm, 10 ppm, 5 ppm, and 1 ppm, or a range between any two of them.

[0074] The present invention can avoid the problem of increased oxide inclusions in the brazing seam and reduced bonding strength caused by excessively high oxygen content by controlling the oxygen content in the modified metal powder 3 .

[0075] Preferably, the solder core 1 is mainly composed of copper-based solder and / or silver-based solder.

[0076] Preferably, the copper-based solder includes copper-zinc solder and / or copper-phosphorus solder.

[0077] In some specific embodiments of the present invention, the shape of the solder core 1 can be any shape.

[0078] In order to facilitate processing and use, the present invention optimizes the shape of the solder core 1. Preferably, the shape of the solder core 1 includes at least one of a filament, a strip, a sheet, a granular, a ring or a spring.

[0079] In some specific embodiments of the present invention, the copper-zinc solder includes at least one of BCu60Zn, BCu60ZnSn, and BCu54Zn; the copper-phosphorus solder includes at least one of BCu92P, BCu94P, and BCu88PAg.

[0080] In some specific embodiments of the present invention, the silver-based solder includes at least one of BAg35CuZn, BAg40CuZn, BAg45CuZn, BAg40CuZnSn, BAg35CuZnSn, BAg30CuZnSn, BAg25CuZnSn, BAg18CuZnSn, BAg20CuZnCd, BAg25CuZnCd, BAg40CuZnNi, and BAg25CuZnNiMn.

[0081] Preferably, at least one groove is provided on the outer surface of the solder core 1, such as Figure 5 As shown, the number of the grooves includes but is not limited to any one of 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 40, 50 point values ​​or any range value between two of them.

[0082] The present invention is beneficial to improving the adhesion firmness of the brazing agent and the modified metal powder 3 by providing at least one groove. At the same time, the content of the brazing agent and the modified metal powder 3 in the brazing material can be increased, so that the composition can be adjusted according to different usage requirements.

[0083] In some specific embodiments of the present invention, the ratio of the depth of the groove to the radius of the solder core 1 is 1:(3-6). Too large a groove depth may make it difficult to form the solder wire.

[0084] Preferably, the flux in the flux layer 2 is mainly composed of the following components in parts by mass: 50-70 parts of K2[(OH)F4B3O3], 10-20 parts of potassium fluoroborate, 10-20 parts of potassium tetraborate, 10-20 parts of boric acid, 5-20 parts of borax and 0.1-0.5 parts of boron powder.

[0085] The brazing flux provided by the present invention has a specific composition and specific ratio, which not only has a good brazing effect, but also is not easy to absorb moisture and generates less smoke. By increasing the component content of K2[(OH)F4B3O3], the moisture absorption effect caused by the use of potassium bifluoride can be avoided. By reducing the component content of potassium fluoroborate, the amount of smoke generated during the brazing process can be effectively reduced. The addition of boric acid, a low-melting-point component, is beneficial to preventing the low-melting-point modified metal powder from being oxidized.

[0086] In some specific embodiments of the present invention, the mass fraction of K2[(OH)F4B3O3] includes but is not limited to any one of 52 parts, 54 parts, 55 parts, 57 parts, 59 parts, 60 parts, 63 parts, 65 parts, and 68 parts or a range between any two of them; the mass fraction of potassium fluoroborate includes but is not limited to any one of 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, and 19 parts or a range between any two of them; the mass fraction of potassium tetraborate includes but is not limited to 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, and 19 parts or a range between any two of them. The mass fraction of the boric acid includes but is not limited to the point value of any one of 11 parts, 12 parts, 13 parts, 14 parts, 15 parts, 16 parts, 17 parts, 18 parts, and 19 parts, or the range value between any two of them; the mass fraction of the borax includes but is not limited to the point value of any one of 7 parts, 9 parts, 10 parts, 12 parts, 14 parts, 15 parts, 17 parts, and 19 parts, or the range value between any two of them; the mass fraction of the boron powder includes but is not limited to the point value of any one of 0.2 parts, 0.3 parts, 0.4 parts, and 0.45 parts, or the range value between any two of them.

[0087] Preferably, when the outer surface of the flux layer 2 is coated with the modified metal powder 3, optionally (optional), the surface of the modified metal powder 3 is also coated with a protective film layer 4; see Figure 1 and Figure 2 .

[0088] In some specific embodiments of the present invention, the melting point of the material used for the protective film layer 4 is lower than the melting point of the flux.

[0089] During brazing, the protective film melts first, releasing the modified metal powder 3 particles as the brazing flux melts. The protective film protects the modified metal powder 3, preventing oxidation. It also helps prevent the modified metal powder 3 from falling off the flux surface, ensuring the stability of the modified metal powder 3 content.

[0090] Preferably, the protective film layer 4 is mainly composed of boric acid.

[0091] Preferably, when the modified metal powder 3 is mixed inside the flux layer 2 , the flux layer 2 mainly consists of the flux and the modified metal powder 3 .

[0092] Preferably, the ratio of the particle size of the flux to the particle size of the modified metal powder 3 is 1.4-1.7, including but not limited to any one of 1.42, 1.45, 1.5, 1.55, 1.6, 1.65, 1.68, or a range between any two of them.

[0093] Assuming that R1 is the particle size of the modified metal powder 3 and R2 is the particle size of the flux (powder), then R2 = (1.4 to 1.7) R1.

[0094] The present invention solves the problem of uneven mixing caused by the large difference in density between metal powder and non-metallic flux powder by setting the ratio of the particle size of the flux to the particle size of the modified metal powder 3 to 1.4-1.7.

[0095] Specifically, assume that the mass of a single metal powder (m1) is the same as the mass of the flux powder (m2), i.e., m1 = m2. m = ρv, i.e., ρ1v1 = ρ2v2. Furthermore, since the volume of a sphere (both the metal powder and the flux powder are spherical or nearly spherical) is V = 4πR 3 , so ρ1R1 3 =ρ2R2 3 Since the density of metal powder is usually 7-9g / cm 3 The density of flux powder is usually 1.8~2.5g / cm 3 , so R2=(1.4~1.7)R1. In the above formula, the subscript 1 is the parameter of the metal powder, and the subscript 2 is the parameter of the flux powder.

[0096] To comprehensively consider the difficulty of preparation and mixing, as well as the avoidance of agglomeration, the present application optimizes the particle size of the flux and the particle size of the modified metal powder 3. Preferably, the flux particle size is 100-170 μm, including but not limited to any one of 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, and 160 μm, or any range therebetween.

[0097] Preferably, the particle size of the modified metal powder 3 is 70-100 μm, including but not limited to any one of 72 μm, 75 μm, 78 μm, 80 μm, 82 μm, 85 μm, 88 μm, 90 μm, 93 μm, 95 μm, and 98 μm, or a range between any two of them.

[0098] The flux and modified metal powder 3 within the above-mentioned particle size range are easy to prepare and will not agglomerate (particle size that is too small is not only difficult to prepare but also prone to agglomeration), and the flux and modified metal powder 3 are easy to mix.

[0099] In a second aspect, the present invention provides a method for preparing the coated solder as described above, comprising the following steps:

[0100] After the surface of the solder core 1 is coated with solder, a solder layer 2 is formed; after the surface of the solder layer 2 is coated with modified metal powder 3, the coated solder (referred to as the first coated solder) is obtained.

[0101] Alternatively, the surface of the brazing filler metal core 1 is coated with a mixture containing the flux and the modified metal powder 3 to obtain the coated brazing filler metal (referred to as the second coated brazing filler metal).

[0102] The coated solder prepared by this method is less prone to delamination, uneven composition, and core breakage. Furthermore, the method has the advantages of simple operation, low processing difficulty, mild conditions, a short process flow, and suitability for mass production.

[0103] Preferably, after coating the modified metal powder 3 , the method further includes coating a protective film on the surface of the modified metal powder 3 to form a protective film layer 4 .

[0104] In some specific embodiments of the present invention, the process of preparing the first coating solder further includes a drying step after coating the modified metal powder 3 and before coating the protective film. Preferably, the drying step includes oven drying.

[0105] In some specific embodiments of the present invention, the process of preparing the first coating solder further includes shaping the flux layer 2 after coating the flux and before coating the modified metal powder 3 .

[0106] In some specific embodiments of the present invention, during the process of preparing the second coating solder, the flux and the modified metal powder 3 are evenly mixed to obtain the mixture containing the flux and the modified metal powder 3 .

[0107] In some specific embodiments of the present invention, the process of preparing the second coating solder further includes a drying step after coating the surface of the solder core 1 with the mixture containing the flux and the modified metal powder 3. Preferably, the drying step includes oven drying.

[0108] In some specific embodiments of the present invention, during the process of coating the modified metal powder 3 and coating the protective film, the coating method may be any conventional coating method, such as spray coating, spin coating, or brush coating.

[0109] Preferably, during the process of applying the modified metal powder 3 and the protective film, the coating includes spraying. Powder spraying is preferably performed using a powder spraying device, which can provide the metal powder with a certain speed, thereby achieving better adhesion of the metal powder to the surface of the undried flux layer and a more uniform layer thickness of the metal powder. Furthermore, it is not necessary to use a brush or the like to contact the flux layer, thereby preventing unevenness of the flux layer.

[0110] In some specific embodiments of the present invention, the protective film layer 4 is formed using boric acid. Preferably, during the protective film coating process, boric acid is dissolved in water to form a boric acid solution, which is then sprayed onto the modified metal powder 3 through atomization. The boric acid solution has a mass fraction of 23% to 38% and a temperature of 80°C to 100°C.

[0111] The use of the boric acid solution with the above mass fraction and temperature is beneficial to ensuring the protective effect of the protective film layer 4, and is also beneficial to improving the coating efficiency without the need for repeated coating.

[0112] In some specific embodiments of the present invention, the solder core 1 is subjected to a diameter reducing treatment before cladding.

[0113] In a third aspect, the present invention provides a device for preparing the coated solder as described above, which is suitable for a coated solder (i.e., a first coated solder) comprising a solder core 1 and a flux layer 2 coated on the surface of the solder core 1, wherein the outer surface of the flux layer 2 is coated with a modified metal powder 3. Figure 4 As shown, the device for preparing the coated solder comprises a first wire feeding unit 201, a flux adhering unit 300, a coating unit 500 and a second wire feeding unit 202 which are connected in sequence.

[0114] The first wire feeding unit 201 and the second wire feeding unit 202 are used to transmit the continuous solder core 1 .

[0115] The flux adhering unit 300 is used to coat (adhere) the flux on the surface of the solder core 1 to form a flux layer 2 .

[0116] The coating unit 500 is used to coat the modified metal powder 3 on the outer surface of the flux layer 2 .

[0117] The device for preparing the coated solder provided by the present invention has a simple structure and low processing difficulty, and can realize large-scale and continuous production of the coated solder.

[0118] Preferably, the coating unit 500 includes a powder spraying device.

[0119] Preferably, a protective film coating unit 900 is further connected between the coating unit 500 and the second wire feeding unit 202 , and the protective film coating unit 900 is used to coat a protective film on the surface of the modified metal powder 3 to form a protective film layer 4 .

[0120] Preferably, the protective film coating unit 900 includes an atomizing coating device.

[0121] The atomizing coating device can spray and coat the protective film (boric acid solution) on the modified metal powder 3 by atomizing. By adopting atomizing instead of direct spraying, the present invention can reduce the impact of the spraying liquid on the modified metal powder 3 and prevent the modified metal powder 3 from being washed away.

[0122] Preferably, a first drying unit 601 is connected between the coating unit 500 and the protective film coating unit 900, and the first drying unit 601 is used to fix the modified metal powder 3 on the surface of the flux layer 2; and / or, a second drying unit 602 is provided between the protective film coating unit 900 and the second wire feeding unit 202, and the second drying unit 602 is used to dry the protective film on the modified metal powder 3.

[0123] In some specific embodiments of the present invention, both the first drying unit 601 and the second drying unit 602 are drying devices.

[0124] In some specific embodiments of the present invention, the drying temperature of the first drying unit 601 is 80° C. to 120° C. Low-temperature drying is beneficial to preventing the modified metal powder 3 from being oxidized.

[0125] Preferably, a vibration unit 700 and a recovery unit 800 are further provided between the first drying unit 601 and the protective film coating unit 900 , wherein the vibration unit 700 is respectively connected to the first drying unit 601 and the protective film coating unit 900 , and the recovery unit 800 is provided below the vibration unit 700 .

[0126] The vibration unit 700 is used to separate the modified metal powder 3 floating on the surface of the flux layer 2 , and the recovery unit 800 is used to recover the modified metal powder 3 separated by the vibration unit 700 .

[0127] The vibration unit 700 is disposed above the recovery unit 800 , more preferably directly above it.

[0128] Preferably, a shaping and sizing unit 400 is further connected between the flux attachment unit 300 and the coating unit 500 , and the shaping and sizing unit 400 is used to shape the flux layer 2 formed after the flux coating.

[0129] Preferably, the first wire feeding unit 201 is further connected to a wire drawing and reducing unit 100 , and the wire drawing and reducing unit 100 is used to reduce the diameter of the solder core 1 .

[0130] In some specific embodiments of the present invention, the device for preparing coated solder includes a wire drawing and reducing unit 100, a first wire feeding unit 201, a flux attachment unit 300, a shaping and sizing unit 400, a coating unit 500 (a powder spraying device), a first drying unit 601 (drying device), a vibration unit 700, a protective film coating unit 900 (atomization coating device), a second drying unit 602 (drying device), and a second wire feeding unit 202, which are connected in sequence. A recovery unit 800 is also provided directly below the vibration unit 700.

[0131] The method for using the above-mentioned coated solder preparation device includes: the solder core 1 is reduced in diameter by the wire drawing and reducing unit 100, and then conveyed by the first wire feeding unit 201 to the flux attachment unit 300, where the flux is coated (attached) on the surface of the solder core 1 to form a flux layer 2. After being shaped by the shaping and sizing unit 400, the flux layer 2 enters the coating unit 500 (powder spraying device), where modified metal powder 3 is sprayed on the outer surface of the flux layer 2. The flux layer 2 then enters the first drying unit 601 (drying device) for drying, thereby fixing the modified metal powder 3 to the surface of the flux layer 2. The flux layer 2 then enters the vibration unit 700, where it is vibrated to shake off excess modified metal powder 3 floating on the surface of the flux layer 2 (to remove floating powder). The shaken-off modified metal powder 3 enters the recovery unit 800 for recovery. After the floating powder is removed, the composite solder enters the protective film coating unit 900 (atomizing coating device), is atomized and sprayed on the surface of the modified metal powder 3 and coated with a protective film to form a protective film layer 4, and then enters the second drying unit 602 (drying device) for drying, and is then transmitted out by the second wire feeding unit 202 to obtain the finished coated solder.

[0132] The embodiments of the present invention will be described in detail below with reference to the examples, but it will be understood by those skilled in the art that the following examples are merely illustrative of the present invention and should not be construed as limiting the scope of the invention. Where specific conditions are not specified in the examples, the methods were performed according to conventional conditions or the conditions recommended by the manufacturer. Where the manufacturers of the reagents or instruments are not specified, they are all commercially available conventional products.

[0133] Example 1

[0134] The coated solder provided in this embodiment includes a solder core 1 and a flux layer 2 coated on the surface of the solder core 1 ; the outer surface of the flux layer 2 is coated with modified metal powder 3 .

[0135] The solder core 1 is made of BAg30CuZn solder and is in a filamentous shape. A groove is provided on the outer surface of the solder core 1. The ratio of the groove depth to the radius of the solder core 1 is 1:5.

[0136] The flux layer 2 is composed of a flux, which is composed of the following components in parts by mass: 60 parts of K2[(OH)F4B3O3], 15 parts of potassium fluoroborate, 10 parts of potassium tetraborate, 15 parts of boric acid, 10 parts of borax and 0.2 parts of boron powder.

[0137] The modified metal powder 3 is metal Sn powder.

[0138] The modified metal powder 3 and the flux together account for 20% of the total mass of the coating solder, with a mass ratio of 2:8. That is, the mass of the Sn element in the modified metal powder 3 accounts for 4.8% of the combined mass of the solder core 1 and the modified metal powder 3.

[0139] The method for preparing the coated solder provided in this embodiment comprises the following steps: coating the surface of the solder core 1 with a flux to form a flux layer 2; shaping the flux layer 2, and then spraying modified metal powder 3 on the surface thereof to obtain the coated solder.

[0140] Example 2

[0141] The coated solder provided in this embodiment includes a solder core 1 and a flux layer 2 coated on the surface of the solder core 1 ; the outer surface of the flux layer 2 is coated with modified metal powder 3 .

[0142] The solder core 1 is made of BCu54Zn solder and is in the shape of a strip. Three grooves are provided on the outer surface of the solder core 1. The ratio of the groove depth to the radius of the solder core 1 is 1:4.

[0143] The flux layer 2 is composed of a flux, which is composed of the following components in parts by mass: 70 parts of K2[(OH)F4B3O3], 10 parts of potassium fluoroborate, 15 parts of potassium tetraborate, 20 parts of boric acid, 20 parts of borax and 0.1 parts of boron powder.

[0144] The modified metal powder 3 is metal In powder.

[0145] The modified metal powder 3 and the flux together account for 35% of the total mass of the coating solder, with a mass ratio of 2:5. That is, the mass of the Sn element in the modified metal powder 3 accounts for 13.3% of the total mass of the solder core 1 and the modified metal powder 3.

[0146] The preparation method of the coated solder provided in this embodiment is the same as that in Example 1.

[0147] Example 3

[0148] The coated solder provided in this embodiment includes a solder core 1 and a flux layer 2 coated on the surface of the solder core 1 ; the outer surface of the flux layer 2 is coated with modified metal powder 3 .

[0149] The solder core 1 is made of BAg40CuZn solder and is in the shape of a sheet. Eight grooves are provided on the outer surface of the solder core 1. The ratio of the groove depth to the radius of the solder core 1 is 1:4.

[0150] The flux layer 2 is composed of a flux, which is composed of the following components in parts by mass: 50 parts of K2[(OH)F4B3O3], 20 parts of potassium fluoroborate, 20 parts of potassium tetraborate, 10 parts of boric acid, 5 parts of borax and 0.5 parts of boron powder.

[0151] The modified metal powder 3 is metal Cd powder.

[0152] The modified metal powder 3 and the flux together account for 25% of the total mass of the coating solder, with a mass ratio of 1:4. That is, the mass of the Cd element in the modified metal powder 3 accounts for 6.3% of the combined mass of the solder core 1 and the modified metal powder 3.

[0153] The preparation method of the coated solder provided in this embodiment is the same as that in Example 1.

[0154] Example 4

[0155] The structure and composition of the coating solder provided in this embodiment are substantially the same as those in embodiment 1, except that the surface of the modified metal powder 3 is further coated with a protective film layer 4 composed of boric acid. Figure 1 .

[0156] The preparation method of the coated solder provided in this embodiment is basically the same as that of Example 1, except that, after spraying the modified metal powder 3, the method further includes the following steps: drying, then coating a protective film on the surface of the modified metal powder 3 to form a protective film layer 4, and then drying again.

[0157] Example 5

[0158] The coated solder provided in this embodiment includes a solder core 1 and a flux layer 2 coated on the surface of the solder core 1. The flux layer 2 is mixed with modified metal powder 3. Specifically, the flux layer 2 is composed of the flux and the modified metal powder 3. The flux has a particle size of 100 to 170 μm; the modified metal powder 3 has a particle size of 70 to 100 μm.

[0159] The solder core 1 is made of BAg25CuZnNiMn solder and is in a filamentous shape. A groove is provided on the outer surface of the solder core 1. The ratio of the groove depth to the radius of the solder core 1 is 1:5.

[0160] The flux consists of the following components in parts by mass: 65 parts of K2[(OH)F4B3O3], 15 parts of potassium fluoroborate, 15 parts of potassium tetraborate, 10 parts of boric acid, 15 parts of borax and 0.3 parts of boron powder.

[0161] The modified metal powder 3 is metal Ni powder.

[0162] The modified metal powder 3 and the flux together account for 30% of the total mass of the coating solder, with a mass ratio of 1:5. That is, the mass of the Ni element in the modified metal powder 3 accounts for 6.7% of the total mass of the solder core 1 and the modified metal powder 3.

[0163] The method for preparing the coated solder provided in this embodiment comprises the following steps:

[0164] The brazing agent and the modified metal powder 3 are mixed evenly to obtain a mixture; the mixture is coated on the surface of the brazing material core 1 and then dried to obtain a coating brazing material.

[0165] Example 6

[0166] The structure of the coating solder provided in this embodiment is the same as that in embodiment 5.

[0167] The composition of the coating solder provided in this embodiment is substantially the same as that of embodiment 5, except that:

[0168] First, the modified metal powder 3 is replaced with CuNi alloy powder. The oxygen content in the modified metal powder 3 is 600 ppm, and the mass fraction of the Ni element in the modified metal powder 3 is 35%.

[0169] Second, the particle size of the flux is changed to 100 μm; the particle size of the modified metal powder 3 is changed to 70 μm, that is, the ratio of the particle size of the flux to the particle size of the modified metal powder 3 is 1.43.

[0170] According to calculation, in Example 6, the mass of the Ni element in the modified metal powder 3 accounts for 2.3% of the total mass of the solder core 1 and the modified metal powder 3 .

[0171] The preparation method of the coated solder provided in this embodiment is the same as that in Example 5.

[0172] Comparative Example 1

[0173] The composition of the metal powder cored flux-cored brazing filler metal provided in this comparative example is the same as that of Example 1, but its structure and preparation method are different from those of Example 1.

[0174] In this comparative example 1, the preparation method of the metal powder-cored flux-cored brazing filler metal includes the following steps: uniformly mixing a flux and a modified metal powder 3 to obtain a mixture; and wrapping the mixture with a brazing filler metal sheath and rolling the mixture to obtain the metal powder-cored flux-cored brazing filler metal. Specifically, the metal powder-cored flux-cored brazing filler metal includes the mixture and the brazing filler metal sheath coating the mixture.

[0175] Comparative Example 2

[0176] The solder provided in this comparative example consists of a solder core 1 and a flux layer 2 coated on the surface of the solder core 1 (ie, no modified metal powder 3 is added).

[0177] The composition and amount of the solder core 1 and the flux layer 2 are the same as those in Example 1.

[0178] The preparation method of the solder provided in this comparative example comprises the following steps: coating a solder flux on the surface of a solder core 1 to form a solder flux layer 2 .

[0179] Experimental Example 1

[0180] The wetting properties of Example 1, Example 4, Comparative Example 1 and Comparative Example 2 on steel plates were tested (the same mass of solder was used in each group, and each group was tested 5 times). The spreading areas are shown in Table 1 below:

[0181] Table 1 Spreading area results of each solder

[0182]

[0183]

[0184] According to Table 1 above, it can be seen that the solder provided in Example 1 not only has better flow performance (average value of 334.49 mm 2 ), and the flow performance is more stable (the difference between the maximum and minimum values ​​is only 13.54 / mm 2 The reason is that, compared with the metal powder cored flux cored brazing material of Comparative Example 1, the brazing material of Example 1 does not have the problems of uneven powder core composition and broken core, so the content of modified metal Sn powder is relatively stable, so the flow laying performance is relatively good and stable.

[0185] Experimental Example 2

[0186] The shear strength of the brazed joints obtained by brazing with the brazing materials of Example 5, Comparative Example 1, and Comparative Example 2 was tested respectively. The results are shown in Table 2 below.

[0187] Table 2 Shear strength results of each brazed joint

[0188]

[0189]

[0190] As can be seen from Table 2, the brazing joint provided by the brazing filler metal in Example 5 not only has high shear strength (average value of 319 MPa), but also has more stable shear strength (the difference between the maximum and minimum values ​​is only 13 MPa). Compared with the metal powder cored flux cored brazing filler metal in Comparative Example 1, the brazing filler metal in Example 1 does not have the problems of uneven powder core composition and core breakage. Therefore, the content of modified metal Ni powder is relatively stable, so the improvement of the shear strength performance of the joint is also relatively stable.

[0191] Although the present invention has been illustrated and described using specific embodiments, it should be appreciated that the above embodiments are merely intended to illustrate the technical solutions of the present invention rather than to limit them. Those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced by equivalents, without departing from the spirit and scope of the present invention. However, these modifications or replacements do not deviate from the essence of the corresponding technical solutions within the scope of the technical solutions of the embodiments of the present invention. Therefore, this means that all such replacements and modifications within the scope of the present invention are included in the appended claims.

Claims

1. A coated solder, characterized in that: It comprises a solder core and a flux layer coated on the surface of the solder core; Wherein, the outer surface of the flux layer is coated with modified metal powder; or the interior of the flux layer is mixed with the modified metal powder; The modified metal powder includes at least one of Sn and its alloys, In and its alloys, Cd and its alloys, Ni and its alloys, Mn and its alloys, and Co and its alloys; The total mass of the Sn element, In element, Cd element, Ni element, Mn element, and Co element in the modified metal powder accounts for more than 2% of the total mass of the solder core and the modified metal powder; When the brazing flux layer is mixed with the modified metal powder, the brazing flux layer is mainly composed of the brazing flux and the modified metal powder; the ratio of the particle size of the brazing flux to the particle size of the modified metal powder is 1.4 to 1.

7.

2. The coated solder according to claim 1, characterized in that The content of oxygen in the modified metal powder is no more than 1000 ppm.

3. The coated solder according to claim 1, characterized in that The solder core is mainly composed of copper-based solder and / or silver-based solder.

4. The coated solder according to claim 3, characterized in that The copper-based solder includes copper-zinc solder and / or copper-phosphorus solder.

5. The coated solder according to claim 1, characterized in that The solder core has a shape of at least one of a wire, a strip, a sheet, a granule, a ring or a spring.

6. The coated solder according to claim 1, characterized in that: At least one groove is provided on the outer surface of the solder core.

7. The coated solder according to claim 1, characterized in that: The flux in the flux layer mainly consists of the following components in parts by mass: composition: 50-70 parts of K2[(OH)F4B3O3], 10-20 parts of potassium fluoroborate, 10-20 parts of potassium tetraborate, 10-20 parts of boric acid, 5-20 parts of borax and 0.1-0.5 parts of boron powder.

8. The coated solder according to claim 1, characterized in that When the outer surface of the flux layer is coated with modified metal powder, the surface of the modified metal powder is also coated with a protective film layer; The protective film layer is mainly composed of boric acid.

9. The coated solder according to claim 1, characterized in that The particle size of the flux is 100 to 170 μm; The particle size of the modified metal powder is 70 to 100 μm.

10. The method for preparing the coated solder according to any one of claims 1 to 9, characterized in that: The steps include: After coating the surface of the solder core with a solder flux, a solder flux layer is formed; after coating the surface of the solder flux layer with modified metal powder, the coated solder is obtained; Alternatively, the surface of a brazing filler metal core is coated with a mixture containing the flux and the modified metal powder to obtain the coated brazing filler metal.

11. The method for preparing the coated solder according to claim 10, characterized in that: After coating the modified metal powder, the method further includes coating a protective film on the surface of the modified metal powder to form a protective film layer.

12. The method for preparing the coated solder according to claim 11, characterized in that: In the process of coating the modified metal powder and coating the protective film, the coating includes spraying.

13. The device for preparing coated solder according to any one of claims 1 to 9, characterized in that: It comprises a first wire feeding unit, a flux adhering unit, a coating unit and a second wire feeding unit which are connected in sequence; Wherein, the first wire feeding unit and the second wire feeding unit are used to transmit a continuous solder core; The flux attachment unit is used to coat the flux on the surface of the solder core to form a flux layer; The coating unit is used to coat the modified metal powder on the outer surface of the flux layer; The coating unit includes a powder spraying device.

14. The device for preparing coated solder according to claim 13, characterized in that: A protective film coating unit is further provided between the coating unit and the second wire feeding unit, and the protective film coating unit is used to coat a protective film on the surface of the modified metal powder to form a protective film layer.

15. The device for preparing coated solder according to claim 14, characterized in that: The protective film coating unit includes an atomizing coating device.

16. The device for preparing coated solder according to claim 14, characterized in that: A first drying unit is further provided between the coating unit and the protective film coating unit, and the first drying unit is used to fix the modified metal powder on the surface of the flux layer; and / or a second drying unit is further provided between the protective film coating unit and the second wire feeding unit, and the second drying unit is used to dry the protective film on the modified metal powder.

17. The device for preparing coated solder according to claim 16, characterized in that: A vibration unit and a recovery unit are also provided between the first drying unit and the protective film coating unit. The vibration unit is used to separate the modified metal powder floating on the surface of the flux layer, and the recovery unit is used to recover the modified metal powder separated by the vibration unit; wherein the vibration unit is provided above the recovery unit.

18. The device for preparing coated solder according to claim 17, characterized in that: The vibration unit is arranged directly above the recovery unit.

19. The device for preparing coated solder according to claim 13, characterized in that: A shaping and sizing unit is further provided between the flux attachment unit and the coating unit, and the shaping and sizing unit is used to shape the flux layer formed after the flux is coated.

20. The device for preparing coated solder according to claim 13, characterized in that: The first wire feeding unit is further connected to a wire drawing and reducing unit, and the wire drawing and reducing unit is used to reduce the diameter of the solder core.

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