A fire-retardant soldering paste, a preparation method thereof and a soldering process

Abstract

The present application relates to the technical field of surface strengthening, and in particular to a fire-retardant brazing paste, a preparation method thereof and a brazing process. According to mass fractions, the raw materials of the fire-retardant brazing paste include: alloy powder 50-55 parts, fire retardant 10-15 parts, diamond micro powder 15-20 parts, solvent 10-15 parts, thixotropic agent 2-4 parts, esterification promoter 0.5-1 part, and flux 7-10 parts; wherein the fire retardant includes hexakis(4-carboxyphenoxy)cyclotriphosphazene. The preparation method includes: dissolving not less than 40wt% of the fire retardant in the solvent, adding the esterification promoter and the diamond micro powder, and heating and stirring; then adding the alloy powder and the remaining fire retardant, and heating and stirring; then adding the thixotropic agent and the flux, stirring and mixing to adjust into a paste, vacuum degassing and aging to obtain the fire-retardant brazing paste. The brazing paste can effectively inhibit the ignition of the coating during the induction heating process, and can avoid the burning loss of the diamond, while keeping the coating with a relatively high bonding strength.

Description

Technical Field

[0001] This invention relates to the field of surface strengthening technology, and more specifically, to a flame-retardant brazing paste, its preparation method, and brazing process. Background Technology

[0002] Induction welding, due to its rapid heating speed, concentrated energy, and high efficiency, has become one of the mainstream processes for brazing and strengthening the surfaces of heavy-duty components. Existing induction welding brazing pastes mainly consist of filler metal, hard phases (diamond, WC, etc.), solvents, and thixotropic agents. Because induction welding heats up very quickly, the organic components in the brazing paste can easily reach their ignition point, causing the coating to ignite and resulting in the hard phase burning off, making it prone to peeling off during use. Furthermore, the high temperature generated by the ignition will exacerbate the oxidation and carbonization of diamond, leading to a significant decrease in the coating's wear resistance.

[0003] Traditional inorganic flame retardants (such as aluminum hydroxide and red phosphorus) have poor compatibility with brazing filler metals and hard phases, lack chemical bonding, and are only physically mixed and filled, resulting in uneven dispersion, poor flame retardant effect, and significant reduction in coating bonding strength. Some flame retardants have low decomposition temperatures, decomposing before reaching the ignition point of organic matter, which cannot match the requirements of induction soldering paste. Furthermore, most existing inorganic flame retardants are in powder form, which can easily change the viscosity and thixotropic smoothness of the brazing paste after addition, leading to uneven coating and sagging, which cannot adapt to the rapid coating-heating process rhythm of induction soldering.

[0004] There are currently no reports on solutions to the flammability of induction welding solder paste.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a flame-retardant soldering paste, its preparation method, and soldering process, so as to overcome the technical defects of existing induction soldering pastes that are prone to ignition and carbonization, and that traditional flame retardants have poor dispersion and reduce the bonding strength of the coating.

[0007] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0008] A flame-retardant soldering paste, wherein the raw materials of the soldering paste, by weight, include: 50-55 parts alloy powder, 10-15 parts flame retardant, 15-20 parts diamond micro powder, 10-15 parts solvent, 2-4 parts thixotropic agent, 0.5-1 part esterification accelerator, and 7-10 parts flux.

[0009] The flame retardant includes hexa(4-carboxyphenoxy)cyclotriphosphazene.

[0010] Preferably, the alloy powder includes nickel-based alloy powder and / or copper-based alloy powder.

[0011] Preferably, the solvent includes at least one of dipropylene glycol methyl ether, diethylene glycol methyl ether, and tripropylene glycol methyl ether.

[0012] Preferably, the thixotropic agent comprises polyamide wax and / or hydrogenated castor oil.

[0013] Preferably, the esterification accelerator includes at least one of p-toluenesulfonic acid, phosphoric acid, and sulfuric acid.

[0014] Preferably, the flux comprises borax and / or boric acid.

[0015] Preferably, the average particle size of the alloy powder is 200-300 mesh.

[0016] Preferably, the average particle size of the diamond micropowder is 30-50 μm.

[0017] The method for preparing the flame-retardant solder paste according to any one of the foregoing embodiments includes the following steps:

[0018] S1. Dissolve not less than 40 wt% of flame retardant in a solvent, add esterification accelerator and diamond powder, heat and stir to obtain the first material;

[0019] S2. Add the alloy powder and the remaining flame retardant to the first material, heat and stir to obtain the second material;

[0020] S3. Add thixotropic agent and flux to the second material, stir and mix to form a paste, then perform vacuum degassing and aging to obtain the flame-retardant solder paste.

[0021] Preferably, in step S1, before adding the diamond micro powder, the step further includes washing and drying the diamond micro powder with alcohol; and / or, the heating temperature is 60-80°C and the time is 1-3 hours.

[0022] Preferably, the process includes a step of drying the alloy powder before step S2; and / or, the heating temperature in step S2 is 60-80°C and the heating time is 1-3 hours.

[0023] A solder coating process includes the following steps:

[0024] (1) Clean the substrate before pretreatment;

[0025] (2) Apply soldering paste to the surface of the substrate and allow it to dry;

[0026] (3) The coated substrate is induction heated to the soldering temperature, kept at that temperature, and then cooled.

[0027] Wherein, the brazing compound is the flame-retardant brazing compound of any one of the foregoing embodiments or the flame-retardant brazing compound prepared by any one of the foregoing embodiments.

[0028] Preferably, in step (2), the coating thickness of the brazing paste is 1.0-2.5 mm.

[0029] Preferably, in step (3), during the induction heating process, ultrasonic vibration is applied to the substrate with a power of 150-200W.

[0030] Preferably, in step (3), the power of the induction heating is 15-25kW.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] This invention uses hexa(4-carboxyphenoxy)cyclotriphosphazene as a flame retardant. The carboxyl group (-COOH) in its molecule reacts with the hydroxyl groups on the diamond surface to encapsulate the diamond, thus providing both flame retardancy and protection against high-temperature burning. Simultaneously, the carboxyl group in the hexa(4-carboxyphenoxy)cyclotriphosphazene molecule reacts with the hydroxyl groups on the alloy powder surface to further encapsulate the alloy powder, ensuring its thorough dispersion. Utilizing the synergistic phosphorus-nitrogen flame retardant effect of hexa(4-carboxyphenoxy)cyclotriphosphazene, it can suppress coating ignition during induction rapid heating. Furthermore, its molecular-level encapsulation structure offers superior dispersibility compared to traditional inorganic flame retardants, without reducing coating bonding strength. The resulting brazing paste is suitable for induction welding rapid coating-heating processes, ensuring a synergistic improvement in coating wear resistance, flame retardancy, and mechanical properties. Attached Figure Description

[0033] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0034] Figure 1 This is a morphology diagram of the diamond in the coating of Application Example 1 of the present invention;

[0035] Figure 2 This is a morphology diagram of the diamond in the coating of Application Example 2 of the present invention;

[0036] Figure 3 This is a morphology diagram of the diamond in the coating of Comparative Example 1 of the present invention. Detailed Implementation

[0037] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0038] The first aspect of the present invention provides a flame-retardant soldering paste, wherein the raw materials of the soldering paste, by weight, include: 50-55 parts of alloy powder, 10-15 parts of flame retardant, 15-20 parts of diamond micro powder, 10-15 parts of solvent, 2-4 parts of thixotropic agent, 0.5-1 part of esterification accelerator, and 7-10 parts of flux.

[0039] Among them, the flame retardant includes hexa(4-carboxyphenoxy)cyclotriphosphazene.

[0040] This invention uses hexa(4-carboxyphenoxy)cyclotriphosphazene as a flame retardant component. Through the synergistic flame retardancy of nitrogen and phosphorus, in the gas phase, the PO· free radicals released during its decomposition can capture H· and HO· free radicals in the combustion reaction, interrupting the combustion chain reaction. At the same time, it releases inert gases such as nitrogen, diluting the concentration of combustible gases and oxygen. In the condensed phase, substances such as phosphoric acid and polyphosphoric acid generated by high-temperature decomposition can promote the early decomposition of the polymer matrix and accelerate carbonization through their dehydration properties, forming a dense carbon layer that effectively isolates heat and oxygen. This achieves a synergistic dual flame retardant mechanism, effectively inhibiting the ignition of the coating.

[0041] Furthermore, the carboxyl group in the hexa(4-carboxyphenoxy)cyclotriphosphazene molecule can react with the hydroxyl groups on the surface of diamond and alloy powder, achieving coating of diamond and alloy powder. Compared with the physical mixing of traditional inorganic flame retardants, the dispersibility of the flame retardant in the brazing paste of this invention is greatly improved, and the chemical bonding avoids the interfacial gap between the flame retardant and the matrix. Diamond, as a hard phase, provides ultra-high hardness. However, in traditional brazing, diamond is easily burned off, leading to a decrease in the wear resistance of the coating. In this invention, the flame retardant is coated on the surface of diamond, which can also protect diamond, reduce the burning rate of diamond, strengthen the metallurgical bond between diamond and matrix, and retain the ultra-high hardness of diamond. Ultimately, it achieves a synergistic improvement of "flame retardant protection, uniform dispersion, strength maintenance, and wear resistance enhancement".

[0042] In some embodiments, typically but not limitingly, for example, in the solder paste raw material, the mass fraction of alloy powder can be any one value or a range of any two values ​​from 50 parts, 52 parts, 54 parts, and 55 parts; the mass fraction of flame retardant can be any one value or a range of any two values ​​from 10 parts, 12 parts, 14 parts, and 15 parts; the mass fraction of diamond micron powder can be any one value or a range of any two values ​​from 15 parts, 16 parts, 18 parts, and 20 parts; the mass fraction of solvent can be... The mass fraction of the thixotropic agent can be any one value or a range of any two values ​​from 10, 12, 14, and 15 parts; the mass fraction of the esterification accelerator can be any one value or a range of any two values ​​from 2, 2.5, 3, 3.5, and 4 parts; the mass fraction of the esterification accelerator can be any one value or a range of any two values ​​from 0.5, 0.6, 0.8, and 1 part; and the mass fraction of the flux can be any one value or a range of any two values ​​from 7, 8, 9, and 10 parts.

[0043] In some specific embodiments of the present invention, the alloy powder includes nickel-based alloy powder and / or copper-based alloy powder, and the role of the alloy powder is to form a coating matrix and provide a metallurgical bonding basis.

[0044] In some specific embodiments of the present invention, the solvent includes at least one of dipropylene glycol methyl ether, diethylene glycol methyl ether, and tripropylene glycol methyl ether, which serves to dissolve the flame retardant and thixotropic agent and adjust the viscosity of the paste.

[0045] In some specific embodiments of the present invention, the thixotropic agent includes polyamide wax and / or hydrogenated castor oil, which serves to impart thixotropic properties to the paste and prevent coating sagging and storage sedimentation.

[0046] In some specific embodiments of the present invention, the esterification accelerator includes at least one of p-toluenesulfonic acid, phosphoric acid, and sulfuric acid, and its function is to promote the esterification reaction of carboxyl and hydroxyl groups, thereby improving the coating efficiency and stability.

[0047] In some specific embodiments of the present invention, the flux includes borax and / or boric acid.

[0048] In some specific embodiments of the present invention, the average particle size of the alloy powder is 200-300 mesh, for example, it can be any one value or a range of any two values ​​among 200 mesh, 220 mesh, 250 mesh, 280 mesh, and 300 mesh.

[0049] In some specific embodiments of the present invention, the average particle size of the diamond micro powder is 30-50 μm. For example, it can be any single value or a range of any two values ​​among 30 μm, 35 μm, 40 μm, 45 μm, and 50 μm.

[0050] A second aspect of the present invention provides a method for preparing the flame-retardant soldering paste described in any of the foregoing embodiments, comprising the following steps:

[0051] S1. Dissolve not less than 40 wt% of flame retardant in a solvent, add esterification accelerator and diamond micro powder, heat and stir to allow the carboxyl groups on the flame retardant to undergo esterification reaction with the hydroxyl groups on the diamond surface to form a coating layer, and obtain the first material.

[0052] S2. Add the alloy powder and the remaining flame retardant to the first material, heat and stir, so that the carboxyl groups on the flame retardant react with the hydroxyl groups on the surface of the alloy powder to form a coating layer, and obtain the second material;

[0053] S3. Add thixotropic agent and flux to the second material, stir and mix to form a paste, then perform vacuum degassing and aging to obtain flame-retardant solder paste.

[0054] The method of this invention first mixes a certain amount of flame retardant with solvent, esterification accelerator, and diamond micron powder to preferentially coat the diamond, forming a protective layer on the diamond surface. This avoids or reduces diamond burn-off during the brazing process. Then, alloy powder is added. The carboxyl groups in the flame retardant react with the hydroxyl groups on the surface of the alloy powder to form bonds. Compared with the physical mixing of traditional inorganic flame retardants, the dispersibility is greatly improved, and the chemical bonding avoids interfacial gaps between the flame retardant and the substrate. It does not reduce the coating bonding strength and overcomes the problem of coating performance degradation caused by traditional inorganic flame retardants. Furthermore, the method of this invention is simple and easy to implement for industrial production.

[0055] As an example, the amount of flame retardant added in step S1 can be any value among 40wt%, 60wt%, 80wt%, and 100wt% of the total amount of flame retardant, or a range of any two values. The purpose of adding no less than 40wt% of flame retardant in this step is to ensure that the diamond is fully coated. When the amount of flame retardant added in step S1 is 100%, the amount of flame retardant added in step S2 is 0, and the alloy powder can be added directly. The flame retardant that has not fully reacted in step S1 continues to react with the alloy powder.

[0056] In some specific embodiments of the present invention, step S1, before adding diamond micro powder, further includes a step of washing and drying the diamond micro powder with alcohol, the purpose of which is to ensure that the hydroxyl groups on the diamond surface are fully exposed; and / or, the heating temperature in step S1 is 60-80°C, for example, it can be any one value or a range of any two values ​​among 60°C, 65°C, 70°C, 75°C, and 80°C; the time is 1-3h, for example, it can be any one value or a range of any two values ​​among 1h, 1.5h, 2h, 2.5h, and 3h.

[0057] In some specific embodiments of the present invention, a step of drying the alloy powder is included before step S2, the purpose of which is to remove the adsorbed moisture and retain the natural hydroxyl groups on the surface; and / or, the heating temperature in step S2 is 60-80°C, for example, it can be any one value or a range of any two values ​​among 60°C, 65°C, 70°C, 75°C, and 80°C; the time is 1-3h, for example, it can be any one value or a range of any two values ​​among 1h, 1.5h, 2h, 2.5h, and 3h.

[0058] A third aspect of the present invention provides a soldering process comprising the following steps:

[0059] (1) Clean the substrate to remove surface oxide scale and oil stains;

[0060] (2) Apply brazing paste to the wear-resistant surface of the substrate and allow it to dry;

[0061] (3) Induction heat the coated substrate to the brazing temperature, keep it at that temperature, and then cool it.

[0062] Wherein, the brazing paste is the flame-retardant brazing paste of any one of the aforementioned embodiments or the flame-retardant brazing paste prepared by any one of the aforementioned embodiments; the brazing temperature in step (3) is determined according to the type of alloy powder in the brazing paste used; as an example, when the alloy powder is BNi-2, the brazing temperature is 1000-1050℃ and the holding time is 3-5min.

[0063] When brazing with the flame-retardant brazing paste provided by this invention, no fire will occur during induction heating, the diamond is not easily burned, and it will not have a negative impact on the bonding strength of the coating, resulting in good wear resistance of the coating.

[0064] In some specific embodiments of the present invention, the cleaning pretreatment in step (1) includes sandblasting and / or ultrasonic cleaning, with the aim of ensuring that the substrate surface is free of oxide scale and oil stains.

[0065] In some specific embodiments of the present invention, in step (2), the coating thickness of the brazing paste is 1.0-2.5 mm. For example, it can be any one value or a range of any two values ​​among 1.0 mm, 1.5 mm, 2.0 mm, and 2.5 mm.

[0066] In some specific embodiments of the present invention, in step (3), during the induction heating process, an ultrasonic transducer is arranged below the substrate to apply ultrasonic vibration to the substrate. The power is 150-200W, for example, it can be any one value or a range of any two values ​​among 150W, 160W, 180W, and 200W. During the heating process, the flame retardant decomposes to form a flame retardant barrier. Applying ultrasonic vibration to the substrate can accelerate the discharge of decomposition gas, reduce coating pores, and ensure the wear resistance of the coating.

[0067] In some specific embodiments of the present invention, in step (3), the power of induction heating is 15-25kW, for example, it can be any one value or a range of any two values ​​among 15kW, 18kW, 20kW, 22kW, and 25kW.

[0068] The following detailed description of some embodiments of the present invention is provided in conjunction with specific application examples. Unless otherwise specified, all raw materials used in the embodiments can be obtained commercially available.

[0069] Example 1

[0070] This embodiment provides a flame-retardant soldering paste, the raw material composition of which is as follows, by weight parts:

[0071] 52 parts of BNi-2 solder powder (200 mesh);

[0072] 12 parts of hexa(4-carboxyphenoxy)cyclotriphosphazene;

[0073] Diamond micron powder (30μm, purity ≥99.9%), 18 parts;

[0074] 13 parts of dipropylene glycol methyl ether;

[0075] 4 parts polyamide wax;

[0076] 1 part of p-toluenesulfonic acid;

[0077] 8 parts flux (a mixture of borax and boric acid in a 1:1 mass ratio).

[0078] The preparation process of flame-retardant solder paste is as follows:

[0079] (1) Activation of diamond surface: Add diamond micro powder to anhydrous ethanol, ultrasonically disperse for 30 minutes (150W, 40kHz), and vacuum dry at 80℃ for 2 hours to ensure that the surface hydroxyl groups are fully exposed;

[0080] (2) Alloy powder pretreatment: BNi-2 brazing filler powder is dried at 80℃ for 2 hours to remove adsorbed moisture and retain the natural hydroxyl groups on the surface;

[0081] (3) Flame retardant coated diamond: Add 40 wt% of hexa(4-carboxyphenoxy)cyclotriphosphazene to dipropylene glycol methyl ether, stir to dissolve, then add p-toluenesulfonic acid and stir for 30 minutes; add activated diamond micro powder, stir at 80℃ and 100 r / min for 2 hours, so that the carboxyl groups on the flame retardant react with the hydroxyl groups on the diamond surface to form a coating layer, and obtain the first material;

[0082] (4) Flame retardant coated alloy powder: The remaining 60wt% hexa(4-carboxyphenoxy)cyclotriphosphazene and the BNi-2 brazing filler powder after drying in step (2) are added to the above system and stirred for 2 hours at 80℃ and 100r / min to allow the carboxyl groups on the flame retardant to undergo esterification with the hydroxyl groups on the surface of the alloy powder to form a coating layer and obtain the second material;

[0083] (5) Preparation, degassing and aging: Add polyamide wax and flux, stir at 50℃ and 200r / min for 1 hour to adjust into paste; put it into a vacuum degassing tank (vacuum -0.095MPa) for 30 minutes to remove internal air bubbles; seal and age at room temperature for 12 hours until the paste structure is stable, and the flame retardant soldering paste is obtained.

[0084] Example 2

[0085] This embodiment provides a flame-retardant soldering paste, the raw material composition of which is as follows, by weight parts:

[0086] 50 parts of BNi-2 brazing filler metal powder (300 mesh);

[0087] 15 parts of hexa(4-carboxyphenoxy)cyclotriphosphazene;

[0088] Diamond micron powder (50μm, purity ≥99.9%) 20 parts;

[0089] 12 parts of dipropylene glycol methyl ether;

[0090] 2 parts polyamide wax;

[0091] 1 part of p-toluenesulfonic acid;

[0092] 8 parts flux (a mixture of borax and boric acid in a 1:1 mass ratio).

[0093] The preparation process of the flame-retardant solder paste is similar to that of Example 1, except that the raw material components are different.

[0094] Application Example 1

[0095] The flame-retardant solder paste prepared in Example 1 was used for soldering, and the steps are as follows:

[0096] (1) Substrate pretreatment: Select 42CrMo carbon steel substrate, perform sandblasting (sandblasting pressure 0.4MPa), ultrasonic cleaning with anhydrous ethanol for 15 minutes, and dry with forced air at 80℃ for 30 minutes to ensure that the surface is free of oxide scale and oil stains;

[0097] (2) Paste coating: Apply the solder paste evenly to the wear-resistant surface of the substrate by scraping. The coating thickness is controlled to be 1.0 mm. After coating, dry at 100℃ for 10 minutes to remove some of the solvent.

[0098] (3) Rapid induction heating and ultrasonic synergy: The coated substrate is placed in an induction heating device, and an induction coil (power 15kW) is set around the substrate. At the same time, an ultrasonic transducer (power 180W) is arranged below the substrate. The temperature is raised to 1050℃ at a rapid heating rate of 8℃ / s and held for 5 minutes.

[0099] (4) Cooling and post-treatment: Turn off the induction heating and cool to room temperature; take out the workpiece and lightly polish the coating surface to remove a small amount of residual carbon layer on the surface to obtain a wear-resistant coating.

[0100] In this application example, there was no ignition during the induction heating process.

[0101] Application Example 2

[0102] The flame-retardant brazing paste prepared in Example 2 was used for brazing. The brazing steps were similar to those in Application Example 1, except that the coating thickness of the brazing paste in step (2) was 2.5 mm. All other conditions were the same as in Application Example 1.

[0103] In this application example, there was no ignition during the induction heating process.

[0104] Comparative Example 1

[0105] Raw materials for brazing compound: similar to those in Example 1, except that hexa(4-carboxyphenoxy)cyclotriphosphazene was not added, and the mass fractions of the remaining components were the same as in Example 1;

[0106] Preparation of brazing paste: Similar to Example 1, except that flame retardant was not added in steps (3) and (4), and the other process conditions were the same as in Example 1;

[0107] Brazing process: Similar to Application Example 1, except that the brazing paste prepared in this comparative example is used for brazing, and all other process conditions are the same as in Application Example 1.

[0108] In this comparative example, the flame ignited clearly when heated to 200°C, and the flame lasted for 2 minutes.

[0109] Comparative Example 2

[0110] Raw materials for brazing compound: similar to those in Example 1, except that hexa(4-carboxyphenoxy)cyclotriphosphazene is replaced with an equal amount of conventional inorganic flame retardant aluminum hydroxide;

[0111] Preparation of brazing paste: Similar to Example 1, except that in steps (3) and (4), hexa(4-carboxyphenoxy)cyclotriphosphazene is replaced with an equal amount of traditional inorganic flame retardant aluminum hydroxide, and the remaining process parameters are the same as in Example 1;

[0112] Brazing process: Similar to Application Example 1, except that the brazing paste prepared in this comparative example is used for brazing, and all other process conditions are the same as in Application Example 1.

[0113] In this comparative example, a slight fire was ignited when heated to 250°C, and the flame lasted for 1 minute.

[0114] Test case

[0115] The bonding strength, diamond burn-off rate, and wear amount of the wear-resistant coating were tested in each application example and comparative example.

[0116] 1. Bonding strength: Using a thrust tester, a 2mm thick coating is pressed against it, and the strength at the moment when the coating shows obvious peeling is calculated.

[0117] 2. Wear amount: The wear resistance of the coating was tested using an MML-1G dry sand semi-free abrasive wear tester. The test load was 50 N, the rotation speed was 300 r / min, the abrasive was corundum sand with an average particle size of 60 mesh, the wear time was 30 min, and the weight loss was measured before and after the test.

[0118] The test results are shown in Table 1.

[0119] Table 1

[0120]

[0121] The comparison shows that the flame retardant properties, bonding strength, wear resistance, and diamond protection effect of the brazing pastes in Examples 1 and 2 of this invention are significantly better than those of the two comparative examples. No ignition occurred during heating with the brazing pastes in Examples 1 and 2, primarily due to the synergistic flame retardancy of phosphorus and nitrogen and the protection of a dense char layer. The bonding strength is significantly improved compared to traditional inorganic flame retardant coatings (Comparative Example 2), mainly due to the chemical bonding and uniform dispersion achieved by esterification coating, avoiding the interface defects of physical mixing in traditional inorganic flame retardants. Diamond burn-off is significantly improved, indicating that the flame retardant coating layer protects the diamond. Compared to Comparative Example 2, the wear in the application example is significantly reduced, thanks to the improved uniformity of flame retardant dispersion and enhanced coating density, solving the problem of coating performance degradation caused by traditional flame retardants. The flame-retardant brazing paste provided by this invention can simultaneously achieve flame retardant protection, uniform dispersion, and strength maintenance.

[0122] like Figure 1 and Figure 2 As shown, in the coating formed by the solder paste of the present invention, there is no significant burn-off of diamond; while... Figure 3 It can be seen that in the brazing coating formed by the soldering paste without flame retardant (Comparative Example 1), the diamond burn-off is obvious; indicating that the hexa(4-carboxyphenoxy)cyclotriphosphazene in the soldering paste of the present invention can not only act as a flame retardant to prevent the coating from igniting and burning during the rapid heating process of induction heating, but also protect the diamond by binding its carboxyl groups to the diamond surface and prevent the diamond from burning off.

[0123] Although the present invention has been illustrated and described with specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and scope of the present invention; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention; therefore, this means that all such substitutions and modifications that fall within the scope of the present invention are included in the appended claims.

Claims

1. A flame-retardant soldering compound, characterized in that, The raw materials of the soldering paste, by weight, include: 50-55 parts alloy powder, 10-15 parts flame retardant, 15-20 parts diamond micro powder, 10-15 parts solvent, 2-4 parts thixotropic agent, 0.5-1 part esterification accelerator, and 7-10 parts flux. The flame retardant includes hexa(4-carboxyphenoxy)cyclotriphosphazene; The preparation method of the flame-retardant soldering paste includes the following steps: S1. Dissolve not less than 40 wt% of the flame retardant in the solvent, add the esterification accelerator and the diamond powder, heat and stir to obtain the first material; S2. Add the alloy powder and the remaining flame retardant to the first material, heat and stir to obtain the second material; S3. Add the thixotropic agent and the flux to the second material, stir and mix to form a paste, then perform vacuum degassing and aging to obtain the flame-retardant solder paste.

2. The flame-retardant soldering paste according to claim 1, characterized in that, It meets at least one of the following characteristics: (1) The alloy powder includes nickel-based alloy powder and / or copper-based alloy powder; (2) The solvent includes at least one of dipropylene glycol methyl ether, diethylene glycol methyl ether, and tripropylene glycol methyl ether; (3) The thixotropic agent includes polyamide wax and / or hydrogenated castor oil; (4) The esterification accelerator includes at least one of p-toluenesulfonic acid, phosphoric acid, and sulfuric acid; (5) The flux includes borax and / or boric acid.

3. The flame-retardant solder paste according to claim 1, characterized in that, The average particle size of the alloy powder is 200-300 mesh.

4. The flame-retardant solder paste according to claim 1, characterized in that, The average particle size of the diamond micro powder is 30-50 μm.

5. The flame-retardant soldering paste according to claim 1, characterized in that, In step S1, before adding the diamond micro powder, the step further includes washing and drying the diamond micro powder with alcohol; and / or, the heating temperature is 60-80℃ and the time is 1-3h.

6. The flame-retardant soldering paste according to claim 1 or 5, characterized in that, The process includes drying the alloy powder before step S2; and / or, the heating temperature in step S2 is 60-80°C and the heating time is 1-3 hours.

7. A soldering process, characterized in that, Includes the following steps: (1) Clean the substrate before pretreatment; (2) Apply soldering paste to the surface of the substrate and allow it to dry; (3) The coated substrate is induction heated to the soldering temperature, kept at that temperature, and then cooled. Wherein, the brazing compound is the flame-retardant brazing compound according to any one of claims 1-6.

8. The brazing process according to claim 7, characterized in that, In step (2), the coating thickness of the brazing paste is 1.0-2.5 mm.

9. The brazing process according to claim 7 or 8, characterized in that, In step (3), at least one of the following characteristics must be satisfied: (1) During the induction heating process, ultrasonic vibration is applied to the substrate with a power of 150-200W; (2) The power of the induction heating is 15-25kW.

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