High-temperature-oxidation-resistant tin paste and preparation method thereof

Abstract

The invention discloses a high-temperature oxidation resistant solder paste and a preparation method thereof, relates to the technical field of solder paste production and processing, and solves the technical problem of insufficient high-temperature oxidation resistance of the existing solder paste. The solder paste comprises the following components in percentage by mass: 88.0%-92.0% of solder alloy powder and 8.0%-12.0% of soldering flux, the soldering flux comprises a thermal collapse regulating agent, a high-temperature polymerization shielding agent and an antioxidant; the antioxidant comprises a high-temperature antioxidant, a metal chelating antioxidant and a corrosion inhibition antioxidant. According to the invention, the oxidation resistance in a high-temperature environment can be obviously improved, so that the lasting and stable welding activity is ensured, and the generation of welding defects such as grape balls is effectively inhibited.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tin paste production and processing, and relates to an anti-high-temperature-oxidation tin paste and a preparation method thereof. BACKGROUND

[0002] As a key electronic assembly material in surface mount technology (SMT), tin paste is mainly composed of solder alloy powder, flux and rheological modifier, and is widely used in the welding of electronic components on printed circuit boards (PCB). The performance of tin paste directly affects the stability of the welding process, the reliability of the welding point and the quality of the final electronic product. With the development of electronic devices towards miniaturization, high density and high performance, the welding process puts forward more stringent requirements on the performance of tin paste, especially under the trend of lead-free, the welding temperature is generally increased, which poses a severe challenge to the high-temperature stability of tin paste.

[0003] In the reflow welding process, tin paste needs to go through a high-temperature environment. The existing tin paste solder alloy powder (such as SAC305 and other tin-based alloys) is prone to oxidation at high temperatures, and a dense oxide film is generated on the surface. This oxidation process can seriously weaken the welding activity of tin paste, causing its wettability and spreading ability to rapidly decrease during the high-temperature holding stage. Specifically, the solder powder particles or between the pads cannot be fully fused, forming independent and smooth solder balls (i.e., "grape ball" phenomenon, because the activity of the flux is exhausted too early, the oxides on the surface of the metal powder cannot be fully removed, and the molten tin liquid cannot spread smoothly due to the excessive surface tension, but instead gathers into balls), resulting in welding defects such as virtual welding, bridge short circuit; at the same time, the effective solder is consumed and impurities are generated due to oxidation, which directly affects the mechanical strength, electrical conductivity and long-term reliability of the welding point.

[0004] Although the existing technology attempts to alleviate this problem by optimizing the flux formula (such as adding more active reducing agents) or improving the solder powder preparation process (such as reducing the oxygen content), these methods often have limitations. For example, excessive enhancement of the activity of the flux may cause corrosion risk or residue problems, and simple low-oxygen control of the solder powder is also difficult to completely resist oxidation under long-time high-temperature exposure. Therefore, the existing tin paste generally lacks high-temperature oxidation resistance when dealing with continuous high-temperature processes, and it is difficult to maintain long-lasting welding activity, which becomes a technical bottleneck for high-reliability welding, especially in complex process scenarios such as multi-temperature zone, long hot air reflow or the need for secondary reflow.

[0005] Therefore, in order to meet the requirements of modern electronic product manufacturing for high reliability and high yield, it is urgent to develop a new type of tin paste and a preparation method thereof. SUMMARY

[0006] To address the above shortcomings, this invention provides a high-temperature oxidation-resistant solder paste and its preparation method, solving the technical problem of insufficient high-temperature oxidation resistance of existing solder pastes. It significantly improves the solder paste's oxidation resistance under high-temperature environments, thereby ensuring long-term stability of soldering activity and effectively inhibiting the generation of soldering defects such as grape-like inclusions. The specific technical solution is as follows: A high-temperature resistant solder paste, comprising the following components by weight percentage: Solder alloy powder: 88.0%~92.0%; Flux: 8.0%~12.0%; The flux includes a heat slump regulator, a high-temperature polymerization shielding agent, and an antioxidant. The antioxidants include high-temperature antioxidants, metal chelating antioxidants, and corrosion-inhibiting antioxidants; The solder alloy powder comprises, by weight percentage: 0.1%–4.0% Ag, 0.1%–1.5% Cu, 0.01%–0.5% Bi, 0.001%–0.05% P, 0.001%–0.03% Ge, 0.001%–0.02% Ga, and the balance Sn. The solder alloy powder has a particle size distribution of 15–35 μm, a sphericity >0.90, an oxygen content <150 ppm, and the total content of the four elements Bi, P, Ge, and Ga is controlled at 0.02%–0.6%.

[0007] Preferably, the heat collapse regulator is a compound of polyethylene glycol monomethyl ether 300 and propylene glycol phenyl ether, the total amount of which is added accounts for 0.1% to 3.0% of the weight of the flux, and the weight ratio of polyethylene glycol monomethyl ether 300 to propylene glycol phenyl ether is 1:(0.8 to 1.5).

[0008] Preferably, the high-temperature polymeric shielding agent is a compound of polyvinylpyrrolidone (PVP K30) and hydrogenated castor oil, with a weight ratio of polyvinylpyrrolidone (PVP K30) to hydrogenated castor oil of 1:(0.2~1), and its addition amount accounts for 0.1%~3.0% of the flux weight.

[0009] Preferably, the high-temperature antioxidant is SSORB303, and its addition amount accounts for 0.1% to 1.5% of the flux weight; the metal chelating antioxidant is a complex of propyl gallate (PG) and disodium ethylenediaminetetraacetate (EDTA-2Na) in a weight ratio of (1 to 3):1, and its addition amount accounts for 0.1% to 2.0% of the flux weight; the corrosion inhibitor antioxidant is at least one of benzotriazole, methylbenzotriazole, and 2-mercaptobenzothiazole, and its addition amount accounts for 0.1% to 1.5% of the flux weight.

[0010] Preferably, the flux further includes the following components by weight percentage of the total flux: 40%–70% hydrogenated rosin, 1%–5% organic acid activator, 1%–4% thixotropic agent, 0.1%–2% antioxidant synergist, and the balance being solvent.

[0011] Preferably, the organic acid activator is a compound of organic acid A and organic acid B in a mass ratio of 1:(1-2), wherein organic acid A is at least one of succinic acid, glutaric acid, and adipic acid; and organic acid B is at least one of citric acid, malic acid, and tartaric acid.

[0012] Preferably, the thixotropic agent is at least one of hydrogenated castor oil, modified organobentonite, and polyamide wax; and the solvent is one of dipropylene glycol butyl ether, diethylene glycol butyl ether acetate, and turpentine.

[0013] Preferably, a method for preparing high-temperature resistant solder paste as described above includes the following steps: (1) Preparation of high temperature polymerized shielding agent: dissolve polyvinylpyrrolidone (PVP K30) in part of the solvent, heat to 60-80℃ and stir until completely dissolved, slowly add the melted hydrogenated castor oil under high speed shearing at 600-700 r / min, emulsify and disperse evenly, and cool for later use. (2) Preparation of metal chelate antioxidant: propyl gallate (PG) and disodium ethylenediaminetetraacetate (EDTA-2Na) are ground together in a mortar for 10-20 min to obtain uniform metal chelate antioxidant powder; (3) Preparation of flux: Under nitrogen atmosphere protection, rosin is heated to 120-150℃ and completely melted, then cooled to 60-80℃, and organic acid activator, antioxidant synergist, heat collapse regulator, high temperature polymerization shielding agent, high temperature antioxidant, corrosion inhibitor antioxidant and metal chelate antioxidant powder prepared in step (2) are added in sequence. After stirring evenly, the temperature is cooled to 40-50℃, thixotropic agent and remaining solvent are added, and high speed dispersion and homogenization are carried out until the system is uniform and transparent. Cool to room temperature to obtain uniform flux. (4) Preparation of coarse solder paste: Under nitrogen atmosphere protection, the solder alloy powder and the flux prepared in step (3) are mechanically stirred and mixed to obtain a uniform paste; (5) Grinding and degassing: Under nitrogen atmosphere protection, the paste from step (4) is ground by three rollers, then vacuum degassing is performed, and then it is left to stand and mature at 15-25°C for 12-20 hours to obtain the high-temperature resistant tin oxide paste.

[0014] Preferably, in step (3), the rotation speed of the high-speed dispersion homogenization is 1000-1500 r / min, and the time is 100-180 min.

[0015] Preferably, in step (4), the stirring conditions for mechanical stirring are as follows: under the conditions of a temperature of 25℃±3℃ and a vacuum of -0.01 to -0.08MPa, first turn left at a speed of 5 to 15 r / min for 1 to 3 minutes, then turn right at a speed of 20 to 40 r / min for 2 to 3 minutes, stir for 60 to 90 minutes, then increase the speed to 40 to 50 r / min and turn left for 2 to 4 minutes, then turn right at a speed of 55 to 70 r / min for 3 to 5 minutes, and the total stirring time is 150 to 160 minutes.

[0016] The present invention achieves at least the following beneficial effects: 1. This invention improves solder paste by adding polyethylene glycol monomethyl ether 300 and propylene glycol phenyl ether compound, resulting in good fluxing properties and the potential to increase solder joint spread rate to over 85%, while exhibiting excellent resistance to heat collapse. By adding the high-temperature antioxidant SSORB303, the solder paste's soldering activity and durability are enhanced, the proportion of solder brittle balls is significantly reduced, and the solder paste's resistance to high-temperature oxidation is improved.

[0017] 2. The present invention adds trace amounts of P, Ge, and Ga elements to solder alloy powder. Under high temperature molten state, these elements can preferentially migrate to the alloy surface and form a dense, stable composite oxide film (such as GeO2, P2O5, etc.) that is well bonded to the matrix. This protective film can effectively prevent the main elements such as Sn and Ag inside from being further oxidized, thereby significantly reducing the oxidation weight gain rate of the solder itself during the high temperature holding stage.

[0018] 3. The flux of this invention innovatively uses corrosion inhibitors and antioxidants (such as benzotriazole) to form an adsorption protective film on the surface of the solder powder during the preheating and heating stages of reflow soldering, thus delaying initial oxidation. The corrosion inhibitors and antioxidants are combined with organic acid activators to achieve a stable release of activity, avoiding the loss of protective ability due to premature consumption of active components in the high-temperature zone.

[0019] 4. This invention utilizes a high-temperature polymeric shielding agent formed by the compounding of polyvinylpyrrolidone (PVP K30) and hydrogenated castor oil. This agent constructs a dense, thermally stable, viscoelastic protective film on the surface of the solder powder, effectively blocking oxygen and delaying the initiation of oxidation. Simultaneously, a metal-chelating antioxidant (a complex of propyl gallate and disodium EDTA) strongly chelates catalytic metal ions dissolved from the solder, eliminating the catalyst for the oxidation reaction. This results in extremely low oxidation of the solder powder after the solder paste undergoes high-temperature processes at 180°C and above, effectively preserving the active components of the flux. This achieves sustained and stable soldering activity, with a stable solder joint spread rate exceeding 88%, significantly reducing cold solder joints and bush-balling caused by high-temperature deactivation. Therefore, this invention fundamentally improves the stability of solder paste in the high-temperature environment of reflow soldering through a dual synergistic mechanism of "physical shielding" and "chemical removal / chelation."

[0020] 5. The solder paste prepared by this invention exhibits excellent printability and adhesion, and maintains stable performance during long-term storage or use. The introduction of PG and EDTA-2Na further reduces the potential corrosiveness of post-soldering residues. Furthermore, PVP can decompose or carbonize at certain high temperatures, preventing the introduction of difficult-to-remove insulating residues, thus improving the long-term electrical reliability and environmental stability of the solder joints. The solder paste prepared by this invention exhibits good resistance to thermal collapse at 180℃. After heat treatment at 180℃ for 10 minutes, the minimum non-bridging pitch is ≤0.05mm, and the solder joint spread rate is ≥88%, meeting the soldering requirements under ultra-fine pitch conditions. Soldering using the solder paste of this invention results in smooth, full solder joints with a small wetting angle and uniform spread, effectively suppressing defects such as solder balls, bridging, and cold solder joints. The mechanical strength (e.g., shear resistance) and conductivity of the solder joints are improved due to low oxidation and good metallurgical bonding. Detailed Implementation

[0021] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. Unless otherwise defined, all technical terms used below have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of the present invention. Unless otherwise specifically stated, all raw materials, reagents, instruments, and equipment used in the present invention are commercially available or can be prepared by existing methods.

[0022] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0023] Example 1 A high-temperature oxidation resistant solder paste, comprising the following components by weight percentage: solder alloy powder: 88.0%, flux: 12.0%; The flux contains the following components by weight percentage: 0.1% heat slump modifier, 3.0% high-temperature polymerization shielding agent, 0.1% high-temperature antioxidant (SSORB303), 2.0% metal chelating antioxidant, 0.1% corrosion inhibitor antioxidant, 40% hydrogenated rosin, 5% organic acid activator, 4% thixotropic agent, 2% antioxidant synergist, and the balance being dipropylene glycol butyl ether.

[0024] Specifically, the heat collapse regulator is a compound of polyethylene glycol monomethyl ether 300 and propylene glycol phenyl ether, with a weight ratio of 1:0.8; the high-temperature polymerization shielding agent is a compound of polyvinylpyrrolidone (PVPK30) and hydrogenated castor oil, with a weight ratio of 1:0.2; the metal chelating antioxidant is a compound of propyl gallate (PG) and disodium ethylenediaminetetraacetate (EDTA-2Na), with a weight ratio of 1:1; and the corrosion inhibitor and antioxidant are benzotriazole and methylbenzotriazole in a mass ratio of 2:1. More specifically, the composition of the solder alloy powder by weight percentage is: 0.1% Ag, 1.5% Cu, 0.01% Bi, 0.05% P, 0.001% Ge, 0.02% Ga and the balance Sn. The solder alloy powder has a particle size distribution of 15 μm, a sphericity > 0.90 and an oxygen content < 150 ppm.

[0025] More specifically, the organic acid activator is a compound of organic acid A and organic acid B in a 1:1 mass ratio; organic acid A is succinic acid and glutaric acid in a 1:1 mass ratio; organic acid B is citric acid and malic acid in a 2:1 mass ratio; and the thixotropic agent is hydrogenated castor oil and modified organic bentonite in a 1:1 mass ratio.

[0026] A method for preparing the high-temperature resistant solder paste as described above includes the following steps: (1) Preparation of high temperature polymerized shielding agent: dissolve polyvinylpyrrolidone (PVP K30) in a portion of dipropylene glycol butyl ether (one-quarter of the total amount), heat to 60°C and stir until completely dissolved. Under high-speed shearing at 600 r / min, slowly add the melted hydrogenated castor oil, emulsify and disperse evenly, and cool for later use. (2) Preparation of metal chelate antioxidant: propyl gallate (PG) and disodium ethylenediaminetetraacetate (EDTA-2Na) were ground together in a mortar for 10 min to obtain a uniform metal chelate antioxidant powder; (3) Preparation of flux: Under nitrogen atmosphere protection, hydrogenated rosin is heated to 120°C and completely melted, then cooled to 60°C, and organic acid activator, antioxidant synergist, heat collapse regulator, high temperature polymerization shielding agent obtained in step (1), high temperature antioxidant, corrosion inhibitor antioxidant and metal chelate antioxidant powder obtained in step (2) are added in sequence. After stirring evenly, the temperature is cooled to 40°C, thixotropic agent and remaining dipropylene glycol butyl ether are added, and high speed dispersion and homogenization are carried out at 1000 r / min for 100 min to make the system uniform and transparent. After cooling to room temperature, a uniform flux is obtained. (4) Preparation of coarse solder paste: Under nitrogen atmosphere protection, the solder alloy powder and the flux prepared in step (3) are mechanically stirred and mixed to obtain a uniform paste; The stirring conditions for mechanical mixing are as follows: at a temperature of 22℃ and a vacuum of -0.01MPa, first rotate to the left at a speed of 5r / min for 3min, then rotate to the right at a speed of 20r / min for 3min, and stir for 90min. Then increase the speed to 40r / min and rotate to the left for 4min, then rotate to the right at a speed of 55r / min for 5min. The total stirring time is 160min. (5) Grinding and degassing: Under nitrogen atmosphere protection, the paste from step (4) is ground by three rollers, then vacuum degassing is performed, and it is left to stand and mature at 15°C for 20 hours to obtain the high-temperature oxidizing solder paste.

[0027] Example 2 A high-temperature oxidation resistant solder paste, comprising the following components by weight percentage: 92.0% solder alloy powder and 8.0% flux; The flux contains the following components by weight percentage: 3.0% heat slump modifier, 0.1% high-temperature polymerization shielding agent, 1.5% high-temperature antioxidant (SSORB303), 0.1% metal chelating antioxidant, 1.5% corrosion inhibitor antioxidant, 70% hydrogenated rosin, 1% organic acid activator, 1% thixotropic agent, 0.1% antioxidant synergist, and the balance is diethylene glycol butyl ether acetate.

[0028] Specifically, the heat collapse regulator is a compound of polyethylene glycol monomethyl ether 300 and propylene glycol phenyl ether, with a weight ratio of 1:1.5; the high-temperature polymerization shielding agent is a compound of polyvinylpyrrolidone (PVPK30) and hydrogenated castor oil, with a weight ratio of 1:1; the metal chelating antioxidant is a compound of propyl gallate (PG) and disodium ethylenediaminetetraacetate (EDTA-2Na), with a weight ratio of 3:1; and the corrosion inhibitor and antioxidant are benzotriazole and 2-mercaptobenzothiazole in a mass ratio of 1:1. More specifically, the composition of the solder alloy powder by weight percentage is: 4.0% Ag, 0.1% Cu, 0.5% Bi, 0.001% P, 0.03% Ge, 0.001% Ga and the balance Sn. The solder alloy powder has a particle size distribution of 35 μm, a sphericity > 0.90 and an oxygen content < 150 ppm.

[0029] More specifically, the organic acid activator is a compound of organic acid A and organic acid B in a mass ratio of 1:2; organic acid A is glutaric acid and adipic acid in a mass ratio of 1:1; organic acid B is citric acid and tartaric acid in a mass ratio of 2:1; and the thixotropic agent is hydrogenated castor oil and polyamide wax in a mass ratio of 2:1.

[0030] A method for preparing the high-temperature resistant solder paste as described above includes the following steps: (1) Preparation of high temperature polymerized shielding agent: dissolve polyvinylpyrrolidone (PVP K30) in a portion of diethylene glycol butyl ether acetate (one-fifth of the total amount), heat to 80°C and stir until completely dissolved, slowly add molten hydrogenated castor oil under high-speed shearing at 700 r / min, emulsify and disperse evenly, and cool for later use. (2) Preparation of metal chelate antioxidant: propyl gallate (PG) and disodium ethylenediaminetetraacetate (EDTA-2Na) were ground together in a mortar for 20 min to obtain a uniform metal chelate antioxidant powder; (3) Preparation of flux: Under nitrogen atmosphere protection, hydrogenated rosin is heated to 150°C and completely melted, then cooled to 80°C, and organic acid activator, antioxidant synergist, heat collapse regulator, high temperature polymerization shielding agent obtained in step (1), high temperature antioxidant, corrosion inhibitor antioxidant and metal chelate antioxidant powder obtained in step (2) are added in sequence. After stirring evenly, the temperature is cooled to 50°C, thixotropic agent and remaining diethylene glycol butyl ether acetate are added, and high speed dispersion and homogenization are carried out at 1500 r / min for 180 min to make the system uniform and transparent. After cooling to room temperature, a uniform flux is obtained. (4) Preparation of coarse solder paste: Under nitrogen atmosphere protection, the solder alloy powder and the flux prepared in step (3) are mechanically stirred and mixed to obtain a uniform paste; The stirring conditions for mechanical mixing are as follows: at a temperature of 28℃ and a vacuum of -0.08MPa, first rotate to the left at a speed of 15r / min for 1min, then rotate to the right at a speed of 40r / min for 2min, and stir for 60min. Then increase the speed to 50r / min and rotate to the left for 2min, then rotate to the right at a speed of 70r / min for 3min. The total stirring time is 150min. (5) Grinding and degassing: Under nitrogen atmosphere protection, the paste from step (4) is ground by three rollers, then vacuum degassing is performed, and it is left to stand and mature at 25°C for 12 hours to obtain the high-temperature oxidizing solder paste.

[0031] Example 3 A high-temperature oxidation resistant solder paste, comprising the following components by weight percentage: 89.0% solder alloy powder and 11.0% flux; The flux contains the following components by weight percentage: 1.0% heat slump modifier, 1.0% high-temperature polymerization shielding agent, 0.5% high-temperature antioxidant (SSORB303), 0.5% metal chelating antioxidant, 0.5% corrosion inhibitor antioxidant, 50% hydrogenated rosin, 4% organic acid activator, 3% thixotropic agent, 1.5% antioxidant synergist, and the balance turpentine.

[0032] Specifically, the heat collapse regulator is a compound of polyethylene glycol monomethyl ether 300 and propylene glycol phenyl ether, with a weight ratio of 1:1; the high-temperature polymerization shielding agent is a compound of polyvinylpyrrolidone (PVP K30) and hydrogenated castor oil, with a weight ratio of 1:0.3; the metal chelating antioxidant is a compound of propyl gallate (PG) and disodium ethylenediaminetetraacetate (EDTA-2Na), with a weight ratio of 1.5:1; and the corrosion inhibitor and antioxidant are benzotriazole and 2-mercaptobenzothiazole in a mass ratio of 1:1. More specifically, the composition of the solder alloy powder by weight percentage is: 1.0% Ag, 0.5% Cu, 0.1% Bi, 0.01% P, 0.01% Ge, 0.005% Ga and the balance Sn. The solder alloy powder has a particle size distribution of 20 μm, a sphericity > 0.90 and an oxygen content < 150 ppm.

[0033] More specifically, the organic acid activator is a compound of organic acid A and organic acid B in a mass ratio of 1:1.2; organic acid A is succinic acid and adipic acid in a mass ratio of 2:1; organic acid B is citric acid, malic acid and tartaric acid in a mass ratio of 1:2:1; and the thixotropic agent is hydrogenated castor oil, modified organic bentonite and polyamide wax in a mass ratio of 2:1:1.

[0034] A method for preparing the high-temperature resistant solder paste as described above includes the following steps: (1) Preparation of high temperature polymerized shielding agent: dissolve polyvinylpyrrolidone (PVP K30) in a portion of turpentine oil (one-sixth of the total amount), heat to 65°C and stir until completely dissolved. Under high-speed shearing at 620 r / min, slowly add the melted hydrogenated castor oil, emulsify and disperse evenly, and cool for later use. (2) Preparation of metal chelate antioxidant: propyl gallate (PG) and disodium ethylenediaminetetraacetate (EDTA-2Na) were ground together in a mortar for 12 min to obtain a uniform metal chelate antioxidant powder; (3) Preparation of flux: Under nitrogen atmosphere protection, hydrogenated rosin is heated to 130°C and completely melted, then cooled to 65°C, and organic acid activator, antioxidant synergist, heat slump regulator, high temperature polymerization shielding agent obtained in step (1), high temperature antioxidant, corrosion inhibitor antioxidant and metal chelate antioxidant powder obtained in step (2) are added in sequence. After stirring evenly, the temperature is cooled to 42°C, thixotropic agent and remaining turpentine are added, and high speed dispersion and homogenization are carried out at 1100 r / min for 120 min to make the system uniform and transparent. After cooling to room temperature, a uniform flux is obtained. (4) Preparation of coarse solder paste: Under nitrogen atmosphere protection, the solder alloy powder and the flux prepared in step (3) are mechanically stirred and mixed to obtain a uniform paste; The stirring conditions for mechanical stirring are as follows: at a temperature of 23℃ and a vacuum of -0.02MPa, the stirring is first turned to the left at a speed of 7r / min for 3min, then turned to the right at a speed of 25r / min for 3min, and stirred for 80min. Then, the speed is increased to 42r / min and the stirring is turned to the left for 4min, then turned to the right at a speed of 60r / min for 5min. The total stirring time is 158min. (5) Grinding and degassing: Under nitrogen atmosphere protection, the paste from step (4) is ground by three rollers, then vacuum degassing is performed, and it is left to stand and mature at 18°C ​​for 19 hours to obtain the high-temperature oxidizing solder paste.

[0035] Example 4 A high-temperature oxidation resistant solder paste, comprising the following components by weight percentage: 91.0% solder alloy powder and 9.0% flux; The flux comprises the following components by weight percentage: 2.0% heat slump modifier, 2.0% high-temperature polymerization shielding agent, 1.0% high-temperature antioxidant (SSORB303), 1.5% metal chelating antioxidant, 1.0% corrosion inhibitor antioxidant, 60% hydrogenated rosin, 2% organic acid activator, 2% thixotropic agent, 1.5% antioxidant synergist, and the balance being diethylene glycol butyl ether acetate; Specifically, the heat collapse regulator is a compound of polyethylene glycol monomethyl ether 300 and propylene glycol phenyl ether, with a weight ratio of 1:1.3; the high-temperature polymerization shielding agent is a compound of polyvinylpyrrolidone (PVPK30) and hydrogenated castor oil, with a weight ratio of 1:0.9; the metal chelating antioxidant is a compound of propyl gallate (PG) and disodium ethylenediaminetetraacetate (EDTA-2Na), with a weight ratio of 2.5:1; and the corrosion inhibitor and antioxidant are benzotriazole, methylbenzotriazole, and 2-mercaptobenzothiazole in a mass ratio of 1:1:1.

[0036] More specifically, the composition of the solder alloy powder by weight percentage is: 3.0% Ag, 1.0% Cu, 0.4% Bi, 0.04% P, 0.02% Ge, 0.015% Ga and the balance Sn. The solder alloy powder has a particle size distribution of 30 μm, a sphericity > 0.90 and an oxygen content < 150 ppm.

[0037] More specifically, the organic acid activator is a compound of organic acid A and organic acid B in a mass ratio of 1:1.8; organic acid A is succinic acid and adipic acid in a mass ratio of 2:1; organic acid B is malic acid and tartaric acid in a mass ratio of 1:1; and the thixotropic agent is hydrogenated castor oil, modified organic bentonite, and polyamide wax in a mass ratio of 1:1:1.

[0038] A method for preparing the high-temperature resistant solder paste as described above includes the following steps: (1) Preparation of high temperature polymerized shielding agent: dissolve polyvinylpyrrolidone (PVP K30) in a portion of diethylene glycol butyl ether acetate (one-fifth of the total amount), heat to 75°C and stir until completely dissolved. Under high-speed shearing at a speed of 680 r / min, slowly add the melted hydrogenated castor oil, emulsify and disperse evenly, and cool for later use. (2) Preparation of metal chelate antioxidant: propyl gallate (PG) and disodium ethylenediaminetetraacetate (EDTA-2Na) were ground together in a mortar for 18 min to obtain a uniform metal chelate antioxidant powder; (3) Preparation of flux: Under nitrogen atmosphere protection, hydrogenated rosin is heated to 140°C and completely melted, then cooled to 75°C, and organic acid activator, antioxidant synergist, heat collapse regulator, high temperature polymerization shielding agent obtained in step (1), high temperature antioxidant, corrosion inhibitor antioxidant and metal chelate antioxidant powder obtained in step (2) are added in sequence. After stirring evenly, the temperature is cooled to 48°C, thixotropic agent and remaining diethylene glycol butyl ether acetate are added, and high speed dispersion and homogenization are carried out at 1400 r / min for 160 min to make the system uniform and transparent. After cooling to room temperature, a uniform flux is obtained. (4) Preparation of coarse solder paste: Under nitrogen atmosphere protection, the solder alloy powder and the flux prepared in step (3) are mechanically stirred and mixed to obtain a uniform paste; The stirring conditions for mechanical mixing are as follows: at a temperature of 27℃ and a vacuum of -0.07MPa, the stirring speed is first turned to the left for 1 minute at 13 r / min, then turned to the right for 2 minutes at 35 r / min. After stirring for 70 minutes, the speed is increased to 48 r / min and turned to the left for 2 minutes, then turned to the right for 3 minutes at 65 r / min. The total stirring time is 153 minutes. (5) Grinding and degassing: Under nitrogen atmosphere protection, the paste from step (4) is ground by three rollers, then vacuum degassing is performed, and it is left to stand and mature at 23°C for 14 hours to obtain the high-temperature oxidizing solder paste.

[0039] Example 5 A high-temperature oxidation resistant solder paste, comprising the following components by weight percentage: 90.0% solder alloy powder and 10.0% flux; The flux contains the following components by weight percentage: 2.0% heat slump modifier, 2.0% high-temperature polymerization shielding agent, 1.0% high-temperature antioxidant (SSORB303), 1.0% metal chelating antioxidant, 0.8% corrosion inhibitor antioxidant, 55% hydrogenated rosin, 3% organic acid activator, 2.5% thixotropic agent, 1.0% antioxidant synergist, and the balance turpentine.

[0040] Specifically, the heat collapse regulator is a compound of polyethylene glycol monomethyl ether 300 and propylene glycol phenyl ether, with a weight ratio of 1:1.1; the high-temperature polymerization shielding agent is a compound of polyvinylpyrrolidone (PVPK30) and hydrogenated castor oil, with a weight ratio of 1:0.6; the metal chelating antioxidant is a compound of propyl gallate (PG) and disodium ethylenediaminetetraacetate (EDTA-2Na), with a weight ratio of 2:1; and the corrosion inhibitor and antioxidant are methylbenzotriazole and 2-mercaptobenzothiazole in a mass ratio of 1:1.

[0041] More specifically, the composition of the solder alloy powder by weight percentage is: 2.0% Ag, 0.8% Cu, 0.3% Bi, 0.03% P, 0.02% Ge, 0.01% Ga and the balance Sn. The solder alloy powder has a particle size distribution of 25 μm, a sphericity > 0.90 and an oxygen content < 150 ppm.

[0042] More specifically, the organic acid activator is a compound of organic acid A and organic acid B in a mass ratio of 1:1.5; organic acid A is succinic acid, glutaric acid, and adipic acid in a mass ratio of 1:1:1; organic acid B is citric acid and malic acid in a mass ratio of 1:1; and the thixotropic agent is hydrogenated castor oil and modified organobentonite in a mass ratio of 1:1.

[0043] A method for preparing the high-temperature resistant solder paste as described above includes the following steps: (1) Preparation of high temperature polymerized shielding agent: dissolve polyvinylpyrrolidone (PVP K30) in a portion of turpentine oil (one-sixth of the total amount), heat to 70°C and stir until completely dissolved. Under high-speed shearing at a speed of 650 r / min, slowly add the melted hydrogenated castor oil, emulsify and disperse evenly, and cool for later use. (2) Preparation of metal chelate antioxidant: propyl gallate (PG) and disodium ethylenediaminetetraacetate (EDTA-2Na) were ground together in a mortar for 15 min to obtain a uniform metal chelate antioxidant powder; (3) Preparation of flux: Under nitrogen atmosphere protection, hydrogenated rosin is heated to 135°C and completely melted, then cooled to 70°C, and organic acid activator, antioxidant synergist, heat collapse regulator, high temperature polymerization shielding agent obtained in step (1), high temperature antioxidant, corrosion inhibitor antioxidant and metal chelate antioxidant powder obtained in step (2) are added in sequence. After stirring evenly, the temperature is cooled to 45°C, thixotropic agent and remaining turpentine are added, and high speed dispersion and homogenization is carried out at 1300 r / min for 140 min to make the system uniform and transparent. After cooling to room temperature, a uniform flux is obtained. (4) Preparation of coarse solder paste: Under nitrogen atmosphere protection, the solder alloy powder and the flux prepared in step (3) are mechanically stirred and mixed to obtain a uniform paste; The stirring conditions for mechanical mixing are as follows: at a temperature of 25℃ and a vacuum of -0.04MPa, first rotate to the left at a speed of 10r / min for 2min, then rotate to the right at a speed of 30r / min for 3min, and stir for 75min. Then increase the speed to 45r / min and rotate to the left for 3min, then rotate to the right at a speed of 63r / min for 4min. The total stirring time is 155min. (5) Grinding and degassing: Under nitrogen atmosphere protection, the paste from step (4) is ground by three rollers, then vacuum degassing is performed, and it is left to stand and mature at 20°C for 16 hours to obtain the high-temperature oxidizing solder paste.

[0044] Comparative Example 1 The difference from Example 5 is that only polyethylene glycol monomethyl ether 300 was used as the heat collapse regulator, while other conditions remained the same.

[0045] Comparative Example 2 The difference from Example 5 is that the total amount of heat slump regulator added accounts for 5.0% of the flux weight, while other conditions remain unchanged.

[0046] Comparative Example 3 The difference from Example 5 is that no metal chelating antioxidant is added, while other conditions remain the same.

[0047] Comparative Example 4 The difference from Example 5 is that no corrosion inhibitor or antioxidant is added, while other conditions remain the same.

[0048] Comparative Example 5 The difference from Example 5 is that polyvinylpyrrolidone is not added to the high-temperature polymerized shielding agent, while other conditions remain the same.

[0049] Comparative Example 6 The difference from Example 5 is that the solder alloy powder used contains 0.01% Ge and 0.06% Ga, while other conditions remain the same.

[0050] Comparative Example 7 The difference from Example 5 is that Ge and Ga are not added to the solder alloy powder, while other conditions remain the same.

[0051] Comparative Example 8 The difference from Example 5 is that in step (3) of the preparation process, when preparing the flux, all materials are heated to 135°C and then simply mixed evenly, while other conditions remain unchanged.

[0052] Comparative Example 9 The difference from Example 5 is that in step (1) of the preparation process, when preparing the high-temperature polymerized shielding agent, polyvinylpyrrolidone (PVP K30) and hydrogenated castor oil are mixed evenly and heated to 70°C, while other conditions remain unchanged.

[0053] Comparative Example 10 The difference from Example 5 is that in step (4) of the preparation process, the mechanical stirring is carried out at a speed of 200 r / min for 155 min, while other conditions remain unchanged.

[0054] The solder paste products prepared in Examples 1-5 and Comparative Examples 1-10 were subjected to performance tests. The products were observed to see whether they collapsed and the minimum non-bridging gap after heat treatment at 180°C for 10 minutes. The viscosity was also observed after heat treatment at 60°C for 60 hours. The results are shown in Table 1 below.

[0055] Table 1. Solder paste performance test results of Examples 1-5 and Comparative Examples 1-10 In summary, the solder paste prepared by this invention exhibits excellent printability and adhesion, and maintains stable performance during long-term storage or use. The introduction of PG and EDTA-2Na further reduces the potential corrosiveness of post-soldering residues. Furthermore, PVP can decompose or carbonize at certain high temperatures, preventing the introduction of difficult-to-remove insulating residues, thus improving the long-term electrical reliability and environmental stability of solder joints. The solder paste prepared by this invention demonstrates good resistance to thermal collapse at 180°C. After heat treatment at 180°C for 10 minutes, the minimum non-bridging pitch is ≤0.05mm, and the solder joint spread rate is ≥88%, meeting the soldering requirements under ultra-fine pitch conditions. Soldering using the solder paste of this invention results in smooth, full solder joints with a small wetting angle and uniform spread, effectively suppressing defects such as solder balls, bridging, and cold solder joints. The mechanical strength (e.g., shear resistance) and conductivity of the solder joints are improved due to low oxidation and good metallurgical bonding.

[0056] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A high-temperature oxidation-resistant tin paste, characterized by, By mass percentage, the following components are included: Solder alloy powder: 88.0%~92.0%; Soldering flux: 8.0%~12.0%; The soldering flux includes a thermal collapse regulator, a high-temperature polymerization shielding agent, and an antioxidant; The antioxidant includes a high-temperature antioxidant, a metal chelate antioxidant, and a corrosion-inhibiting antioxidant; The components of the solder alloy powder by weight percentage are: 0.1%~4.0% Ag, 0.1%~1.5% Cu, 0.01%~0.5% Bi, 0.001%~0.05% P, 0.001%~0.03% Ge, 0.001%~0.02% Ga, and the balance of Sn. The solder alloy powder has a particle size distribution of 15~35 μm, a sphericity of >0.90, an oxygen content of <150 ppm, and a total content of Bi, P, Ge, and Ga of 0.02%~0.6%.

2. The high-temperature oxidation-resistant solder paste of claim 1, wherein, The thermal collapse regulator is a compound of polyethylene glycol monomethyl ether 300 and propylene glycol phenyl ether, with a total addition amount of 0.1%~3.0% of the weight of the soldering flux, and a weight ratio of polyethylene glycol monomethyl ether 300 to propylene glycol phenyl ether of 1:(0.8~1.5).

3. The high-temperature oxidation resistant solder paste of claim 1, wherein, The high-temperature polymerization shielding agent is compounded by polyvinyl pyrrolidone and hydrogenated castor oil, with a weight ratio of polyvinyl pyrrolidone to hydrogenated castor oil of 1:(0.2~1), and an addition amount of 0.1%~3.0% of the weight of the soldering flux.

4. The high-temperature oxidation resistant solder paste of claim 1, wherein, The high-temperature antioxidant is SSORB303, with an addition amount of 0.1%~1.5% of the weight of the soldering flux; the metal chelate antioxidant is a compound of propyl gallate and disodium ethylenediaminetetraacetate, with a weight ratio of 1~3:1, and an addition amount of 0.1%~2.0% of the weight of the soldering flux; the corrosion-inhibiting antioxidant is at least one of benzotriazole, methylbenzotriazole, and 2-mercaptobenzothiazole, with an addition amount of 0.1%~1.5% of the weight of the soldering flux.

5. The high-temperature oxidation resistant solder paste of claim 1, wherein, The soldering flux further includes the following components by percentage of the total weight of the soldering flux: hydrogenated rosin 40%~70%, organic acid activator 1%~5%, thixotropic agent 1%~4%, antioxidant synergist 0.1%~2%, and the balance of solvent.

6. The high-temperature oxidation resistant solder paste of claim 5, wherein, The organic acid activator is compounded by organic acid A and organic acid B in a mass ratio of 1:(1~2), the organic acid A is at least one of succinic acid, glutaric acid, and adipic acid; and the organic acid B is at least one of citric acid, malic acid, and tartaric acid.

7. The high-temperature oxidation resistant solder paste of claim 5, wherein, The thixotropic agent is at least one of hydrogenated castor oil, modified organic bentonite, and polyamide wax; and the solvent is one of dipropylene glycol butyl ether, diethylene glycol butyl ether acetate, and turpentine oil.

8. A method of producing the high-temperature oxidation resistant tin paste according to any one of claims 1 to 7, characterized by, The method includes the following steps: (1) Preparation of a high-temperature polymerization shielding agent: dissolve polyvinyl pyrrolidone in part of the solvent, heat to 60~80℃, and stir until completely dissolved. Under high-speed shearing at a speed of 600~700 r / min, slowly add the melted hydrogenated castor oil, emulsify and disperse uniformly, and cool for standby use. (2) Preparation of metal chelated antioxidant: propyl gallate and disodium ethylenediaminetetraacetate are ground together in a mortar for 10-20 min to obtain a uniform metal chelated antioxidant powder; (3) Preparation of flux: under nitrogen atmosphere, rosin is heated to 120-150°C and completely dissolved, then cooled to 60-80°C, and then organic acid activator, antioxidant synergist, thermal collapse control agent, high-temperature polymerization shielding agent prepared in step (1), high-temperature antioxidant, corrosion and oxidation inhibitor, and metal chelated antioxidant powder prepared in step (2) are added in sequence, stirred uniformly, cooled to 40-50°C, and then thixotropic agent and remaining solvent are added, and high-speed dispersion homogenization is performed until the system is uniformly transparent, and then cooled to room temperature to obtain a uniform and consistent flux; (4) Preparation of rough tin paste: under nitrogen atmosphere, solder alloy powder is mechanically stirred and mixed with the flux prepared in step (3) to obtain a uniform paste; (5) Grinding and defoaming: under nitrogen atmosphere, the paste of step (4) is subjected to three-roll grinding, followed by vacuum defoaming treatment, and then placed at 15-25°C for 12-20h for maturation to obtain the high-temperature oxidation resistant tin paste.

9. The production method according to claim 8, characterized by, In step (3), the rotation speed of high-speed dispersion homogenization is 1000-1500r / min, and the time is 100-180min.

10. The preparation method according to claim 8, characterized in that, In step (4), the stirring conditions of mechanical stirring and mixing are as follows: under the conditions of temperature 25°C±3°C and vacuum degree -0.01 to -0.08MPa, first rotate left at a speed of 5-15r / min for 1-3min, then rotate right at a speed of 20-40r / min for 2-3min, stir for 60-90min, then increase the rotation speed to 40-50r / min and rotate left for 2-4min, then rotate right at a speed of 55-70r / min for 3-5min, and the total stirring time is 150-160min.

Images