A dispersible tin powder, its preparation method, and tin paste

Abstract

This invention relates to the field of solder paste technology, and more particularly to an easily dispersible tin powder, its preparation method, and the solder paste thereof. The easily dispersible tin powder comprises, by weight, 10-20 parts tin powder, 1-2 parts N-aminoethyl-3-aminopropylmethyldimethoxysilane, 1.1-3 parts 3-aminopropyltriethoxysilane, 1-2 parts ascorbic acid, 0.5-1 parts polyvinylpyrrolidone, and 1-2 parts polyethylene glycol-polypropylene glycol-polyethylene glycol block copolymer. The solder paste comprises, by weight, 50-80 parts the easily dispersible tin powder, 10-20 parts rosin, 1-3 parts carboxylated carbon nanotubes, 1-2 parts nano-diatomaceous earth, 1-2 parts antioxidant, 1-5 parts activator, and 10-20 parts solvent. The solder paste obtained by this invention not only has good dispersibility, uniform texture, and strong stability, and is not prone to agglomeration, but also meets the requirements of ultra-fine pitch. Furthermore, due to its good fluidity during printing, it is less likely to clog the nozzle.

Description

Technical Field

[0001] This invention relates to the field of solder paste technology, and in particular to an easily dispersible solder powder, its preparation method, and solder paste. Background Technology

[0002] Solder paste, as a key material for soldering electronic components, directly affects the reliability and precision of electronic assembly. With the rapid miniaturization of electronic components, the requirements for the fineness of solder paste are increasing. Traditional solder paste consists of flux and solder powder, where the particle size of the solder powder directly determines the precision of the soldering. To meet the requirements of ultra-fine pitch soldering, solder powder with even smaller particle sizes must be used.

[0003] However, on the one hand, as the particle size of tin powder decreases, its specific surface area increases significantly, leading to a sharp increase in surface energy. This makes small-particle-size tin powder highly susceptible to oxidation, forming an oxide layer. This not only reduces the activity of the tin powder but also affects the soldering quality. On the other hand, due to the enhanced van der Waals forces between particles, small-particle-size tin powder is more prone to agglomeration, forming larger particle clusters. This makes it extremely difficult to disperse the tin powder in the flux, disrupting the uniformity of the solder paste. Furthermore, agglomeration further exacerbates the settling problem of tin powder, causing stratification of the solder paste during storage and use, severely affecting the stability and consistency of soldering. Moreover, agglomerated tin powder easily clogs nozzles during printing, causing printing defects and further reducing production efficiency.

[0004] Existing technologies mainly disperse tin powder by adding surfactants, but this method has unstable factors during the soldering process, easily generates gas, and produces solder joint voids, failing to fundamentally solve the problems of agglomeration and oxidation.

[0005] Therefore, how to effectively inhibit the oxidation of tin powder, prevent agglomeration, and improve its dispersibility in solder paste has become a pressing technical problem to be solved in the current electronics manufacturing field. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art by proposing an easily dispersible tin powder, its preparation method, and tin paste.

[0007] An easily dispersible tin powder, the raw materials of which, by weight, include: 10-20 parts tin powder, 1-2 parts N-aminoethyl-3-aminopropylmethyldimethoxysilane, 1.1-3 parts 3-aminopropyltriethoxysilane, 1-2 parts ascorbic acid, 0.5-1 parts polyvinylpyrrolidone, and 1-2 parts polyethylene glycol-polypropylene glycol-polyethylene glycol block copolymer.

[0008] Preferably, the easily dispersible tin powder comprises: secondary processed tin powder and a coating layer covering the outer side of the secondary processed tin powder; wherein, the coating layer is formed by heat treatment after embedding the secondary processed tin powder in a coating liquid; the raw materials of the coating liquid include: 3-aminopropyltriethoxysilane, polyvinylpyrrolidone, polyethylene glycol-polypropylene glycol-polyethylene glycol block copolymer and anhydrous ethanol.

[0009] Preferably, the secondary-treated tin powder is prepared by the following steps: N-aminoethyl-3-aminopropylmethyldimethoxysilane and 3-aminopropyltriethoxysilane are added to an ethanol aqueous solution and stirred evenly, ultrasonically treated for 10-20 minutes, ascorbic acid is added and stirred evenly, primary-treated tin powder is added under nitrogen protection and stirred for 1-2 hours, the temperature is raised to 50-60℃ and stirred for 20-30 minutes, filtered, washed, and spray-dried.

[0010] More preferably, the mass ratio of 3-aminopropyltriethoxysilane to N-aminoethyl-3-aminopropylmethyldimethoxysilane is 0.1-1:1-2.

[0011] More preferably, the ultrasonic processing frequency is 70-80kHz.

[0012] More preferably, the tin powder is obtained by acid washing, water washing until neutral, and then drying.

[0013] Specifically, the particle size of the tin powder is 1-15 μm.

[0014] Specifically, the pickling process uses hydrochloric acid with a mass fraction of 1-5% for 5-15 minutes.

[0015] Specifically, the drying temperature is 40-50℃.

[0016] The above-mentioned method for preparing easily dispersible tin powder includes the following steps: adding secondary-treated tin powder to a fluidized bed with a bed temperature of 40-50℃, spraying the coating liquid into the fluidized bed while keeping the secondary-treated tin powder in a fluidized state, heat-treating at 50-60℃ for 20-40 minutes, vacuum drying, and passing through a 200-mesh sieve.

[0017] A solder paste, the raw materials of which, by mass, include: 50-80 parts of the above-mentioned easily dispersible tin powder, 10-20 parts of rosin, 1-3 parts of carboxylated carbon nanotubes, 1-2 parts of nano-grade diatomaceous earth, 1-2 parts of antioxidant, 1-5 parts of activator, and 10-20 parts of solvent.

[0018] Preferably, the antioxidant is 2-mercaptobenzimidazole.

[0019] Preferably, the solvent is ethyl acetate.

[0020] Preferably, the active agent includes diisooctyl fumarate, salicylamide, and pyridinecarboxylic acid; the mass ratio of diisooctyl fumarate, salicylamide, and pyridinecarboxylic acid is 1-2:1-2:1.

[0021] The preparation method of the above solder paste includes the following steps: mixing the above easily dispersible tin powder, rosin, carboxylated carbon nanotubes and solvent evenly, stirring at 70-80℃ for 20-30 min, adding nano-sized diatomaceous earth and continuing to stir for 5-15 min, adding antioxidant and activator and continuing to stir for 10-20 min.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] This invention utilizes a compound of N-aminoethyl-3-aminopropylmethyldimethoxysilane and 3-aminopropyltriethoxysilane to significantly improve the surface properties of tin powder and form a cross-linked network on its surface, which can significantly enhance the density of the protective layer. Combined with L-ascorbic acid, a reducing protective layer is formed under nitrogen atmosphere, which effectively inhibits the oxidation of tin powder surface.

[0024] The present invention uses polyvinylpyrrolidone and polyethylene glycol-polypropylene glycol-polyethylene glycol block copolymer to effectively form steric hindrance on the outer layer of tin powder. The 3-aminopropyltriethoxysilane in the coating layer is combined with the carboxylated carbon nanotubes in the solder paste, which significantly improves the dispersibility of tin powder in the solder paste under the action of rosin.

[0025] The solder paste obtained by this invention not only has good dispersibility, uniform texture, and strong stability, and is not easy to agglomerate, but also meets the requirements of ultra-fine pitch. Moreover, due to its good fluidity, it is not easy to clog the nozzle during the printing process. Attached Figure Description

[0026] Figure 1 This is a comparison chart of the oxygen content and dispersibility of the tin powder obtained in Example 5 and Comparative Examples 1-2.

[0027] Figure 2 This is a comparison chart of the thixotropic index and viscosity change rate of the solder pastes obtained in Example 5 and Comparative Examples 1-2.

[0028] Figure 3 The diagram shows a comparison of the void rate after soldering using the solder paste obtained in Example 5 and Comparative Examples 1-2. Detailed Implementation

[0029] The present invention will be further explained below with reference to specific embodiments.

[0030] All the raw materials used below can be purchased from the market. For example, polyethylene glycol-polypropylene glycol-polyethylene glycol block copolymer (PEG-PPO-PEG) was purchased from Haian Petrochemical Plant in Jiangsu Province.

[0031] Example 1: An easily dispersible tin powder, the raw materials of which include: 100g tin powder, 10g N-aminoethyl-3-aminopropylmethyldimethoxysilane, 11g 3-aminopropyltriethoxysilane, 10g ascorbic acid, 5g PVP K30, and 10g polyethylene glycol-polypropylene glycol-polyethylene glycol block copolymer.

[0032] The preparation method of the above-mentioned easily dispersible tin powder includes the following steps:

[0033] Tin powder with a particle size of 1-15μm was pickled with 1% hydrochloric acid for 10 minutes, washed with deionized water until neutral, and dried at 40℃ to obtain primary treated tin powder.

[0034] N-aminoethyl-3-aminopropylmethyldimethoxysilane and 1g of 3-aminopropyltriethoxysilane were added to 800g of 5% ethanol aqueous solution and stirred until homogeneous. The mixture was then sonicated for 10min at a frequency of 70kHz. Ascorbic acid was added and stirred until homogeneous. Under nitrogen protection, primary treated tin powder was added and stirred at room temperature for 1h at a speed of 100r / min. The mixture was then heated to 50℃ and stirred for another 20min. The mixture was filtered, washed with anhydrous ethanol, and spray-dried at an inlet temperature of 60℃ and an outlet temperature of 40℃ to obtain secondary treated tin powder.

[0035] 10g of 3-aminopropyltriethoxysilane, PVP K30, and polyethylene glycol-polypropylene glycol-polyethylene glycol block copolymer were added to 400g of anhydrous ethanol and stirred until homogeneous to obtain the coating solution.

[0036] The secondary-processed tin powder was added to a fluidized bed at a bed temperature of 40°C. The coating liquid was atomized and sprayed into the fluidized bed while keeping the secondary-processed tin powder in a fluidized state. The mixture was then heat-treated at 50°C for 20 minutes, vacuum dried, and passed through a 200-mesh sieve.

[0037] A solder paste, the raw materials of which include: 50g of the above-mentioned easily dispersible tin powder, 10g of rosin, 1g of carboxylated carbon nanotubes, 1g of nano-sized diatomaceous earth, 1g of 2-mercaptobenzimidazole, 1g of activator, and 10g of ethyl acetate. The activator is composed of diisooctyl fumarate, salicylamide, and pyridinecarboxylic acid in a mass ratio of 1:1:1.

[0038] The preparation method of the above solder paste includes the following steps: the above easily dispersible tin powder, rosin, carboxylated carbon nanotubes and ethyl acetate are mixed evenly, stirred at 70°C for 20 min, nano-sized diatomaceous earth is added and stirred for another 5 min, 2-mercaptobenzimidazole and activator are added and stirred for another 10 min.

[0039] Example 2: An easily dispersible tin powder, the raw materials of which include: 200g tin powder, 20g N-aminoethyl-3-aminopropylmethyldimethoxysilane, 30g 3-aminopropyltriethoxysilane, 20g ascorbic acid, 10g PVP K30, and 20g polyethylene glycol-polypropylene glycol-polyethylene glycol block copolymer.

[0040] The preparation method of the above-mentioned easily dispersible tin powder includes the following steps:

[0041] Tin powder with a particle size of 1-15μm was pickled with 5% hydrochloric acid for 20 minutes, washed with deionized water until neutral, and dried at 50℃ to obtain primary treated tin powder.

[0042] N-aminoethyl-3-aminopropylmethyldimethoxysilane and 10g of 3-aminopropyltriethoxysilane were added to 1000g of 15% ethanol aqueous solution and stirred until homogeneous. The mixture was then sonicated for 20min at a frequency of 80kHz. Ascorbic acid was added and stirred until homogeneous. Under nitrogen protection, primary treated tin powder was added and stirred at room temperature at 300r / min for 2h. The mixture was then heated to 60℃ and stirred for another 30min. The mixture was filtered, washed with anhydrous ethanol, and spray-dried to obtain secondary treated tin powder.

[0043] 20g of 3-aminopropyltriethoxysilane, PVP K30, and polyethylene glycol-polypropylene glycol-polyethylene glycol block copolymer were added to 700g of anhydrous ethanol and stirred until homogeneous to obtain the coating solution.

[0044] The secondary-processed tin powder was added to a fluidized bed at a bed temperature of 50°C. The coating liquid was atomized and sprayed into the fluidized bed while keeping the secondary-processed tin powder in a fluidized state. The mixture was then heat-treated at 60°C for 40 minutes, vacuum dried, and passed through a 200-mesh sieve.

[0045] A solder paste, the raw materials of which include: 80g of the above-mentioned easily dispersible tin powder, 20g of rosin, 3g of carboxylated carbon nanotubes, 2g of nano-grade diatomaceous earth, 2g of 2-mercaptobenzimidazole, 5g of activator, and 20g of ethyl acetate. The activator is composed of diisooctyl fumarate, salicylamide, and pyridinecarboxylic acid in a mass ratio of 2:2:1.

[0046] The preparation method of the above solder paste includes the following steps: the above easily dispersible tin powder, rosin, carboxylated carbon nanotubes and ethyl acetate are mixed evenly, stirred at 80℃ for 30 min, nano-sized diatomaceous earth is added and stirred for 15 min, 2-mercaptobenzimidazole and activator are added and stirred for 20 min.

[0047] Example 3: An easily dispersible tin powder, the raw materials of which include: 120g tin powder, 18g N-aminoethyl-3-aminopropylmethyldimethoxysilane, 21g 3-aminopropyltriethoxysilane, 12g ascorbic acid, 9g PVP K30, and 12g polyethylene glycol-polypropylene glycol-polyethylene glycol block copolymer.

[0048] The preparation method of the above-mentioned easily dispersible tin powder includes the following steps:

[0049] Tin powder with a particle size of 1-15μm was pickled with 4% hydrochloric acid for 12 minutes, washed with deionized water until neutral, and dried at 48℃ to obtain primary treated tin powder.

[0050] N-aminoethyl-3-aminopropylmethyldimethoxysilane and 3g of 3-aminopropyltriethoxysilane were added to 950g of 8% ethanol aqueous solution and stirred until homogeneous. The mixture was ultrasonically treated for 18min at a frequency of 72kHz. Ascorbic acid was added and stirred until homogeneous. Under nitrogen protection, the primary treated tin powder was added and stirred at room temperature at 250r / min for 80min. The temperature was raised to 58℃ and stirring was continued for 22min. The mixture was filtered, washed with anhydrous ethanol, and spray-dried to obtain secondary treated tin powder.

[0051] 18g of 3-aminopropyltriethoxysilane, PVP K30, and polyethylene glycol-polypropylene glycol-polyethylene glycol block copolymer were added to 500g of anhydrous ethanol and stirred until homogeneous to obtain the coating solution.

[0052] The secondary-processed tin powder was added to a fluidized bed at a bed temperature of 48°C. The coating liquid was atomized and sprayed into the fluidized bed while keeping the secondary-processed tin powder in a fluidized state. The mixture was then heat-treated at 52°C for 35 minutes, vacuum dried, and passed through a 200-mesh sieve.

[0053] A solder paste, comprising the following raw materials: 60g of the above-mentioned easily dispersible tin powder, 18g of rosin, 1.5g of carboxylated carbon nanotubes, 1.8g of nano-sized diatomaceous earth, 1.2g of 2-mercaptobenzimidazole, 4g of activator, and 12g of ethyl acetate. The activator is composed of diisooctyl fumarate, salicylamide, and pyridinecarboxylic acid in a mass ratio of 1.8:1.3:1.

[0054] The preparation method of the above solder paste includes the following steps: the above easily dispersible tin powder, rosin, carboxylated carbon nanotubes and ethyl acetate are mixed evenly, stirred at 77°C for 22 min, nano-sized diatomaceous earth is added and stirred for 12 min, 2-mercaptobenzimidazole and activator are added and stirred for 12 min.

[0055] Example 4: An easily dispersible tin powder, the raw materials of which include: 180g tin powder, 12g N-aminoethyl-3-aminopropylmethyldimethoxysilane, 19g 3-aminopropyltriethoxysilane, 18g ascorbic acid, 7g PVP K30, and 18g polyethylene glycol-polypropylene glycol-polyethylene glycol block copolymer.

[0056] The preparation method of the above-mentioned easily dispersible tin powder includes the following steps:

[0057] Tin powder with a particle size of 1-15μm was pickled with 2% hydrochloric acid for 18 minutes, washed with deionized water until neutral, and dried at 42℃ to obtain primary treated tin powder.

[0058] N-aminoethyl-3-aminopropylmethyldimethoxysilane and 7g of 3-aminopropyltriethoxysilane were added to 850g of 12% ethanol aqueous solution and stirred until homogeneous. The mixture was then sonicated for 12min at a frequency of 78kHz. Ascorbic acid was added and stirred until homogeneous. Under nitrogen protection, the primary treated tin powder was added and stirred at 150r / min at room temperature for 100min. The mixture was then heated to 52℃ and stirred for another 28min. The mixture was filtered, washed with anhydrous ethanol, and spray-dried to obtain the secondary treated tin powder.

[0059] 12g of 3-aminopropyltriethoxysilane, PVP K30, and polyethylene glycol-polypropylene glycol-polyethylene glycol block copolymer were added to 600g of anhydrous ethanol and stirred until homogeneous to obtain the coating solution.

[0060] The secondary-processed tin powder was added to a fluidized bed at a bed temperature of 42°C. The coating liquid was atomized and sprayed into the fluidized bed while keeping the secondary-processed tin powder in a fluidized state. The mixture was then heat-treated at 58°C for 25 minutes, vacuum dried, and passed through a 200-mesh sieve.

[0061] A solder paste comprising the following raw materials: 70g of the above-mentioned easily dispersible tin powder, 12g of rosin, 2.5g of carboxylated carbon nanotubes, 1.2g of nano-sized diatomaceous earth, 1.8g of 2-mercaptobenzimidazole, 2g of activator, and 18g of ethyl acetate. The activator is composed of diisooctyl fumarate, salicylamide, and pyridinecarboxylic acid in a mass ratio of 1.2:1.7:1.

[0062] The preparation method of the above solder paste includes the following steps: the above easily dispersible tin powder, rosin, carboxylated carbon nanotubes and ethyl acetate are mixed evenly, stirred at 73°C for 28 min, nano-sized diatomaceous earth is added and stirred for another 8 min, 2-mercaptobenzimidazole and activator are added and stirred for another 18 min.

[0063] Example 5: An easily dispersible tin powder, the raw materials of which include: 150g tin powder, 15g N-aminoethyl-3-aminopropylmethyldimethoxysilane, 20g 3-aminopropyltriethoxysilane, 15g ascorbic acid, 8g PVP K30, and 15g polyethylene glycol-polypropylene glycol-polyethylene glycol block copolymer.

[0064] The preparation method of the above-mentioned easily dispersible tin powder includes the following steps:

[0065] Tin powder with a particle size of 1-15μm was pickled with 3% hydrochloric acid for 15 minutes, washed with deionized water until neutral, and dried at 45℃ to obtain primary treated tin powder.

[0066] N-aminoethyl-3-aminopropylmethyldimethoxysilane and 5g of 3-aminopropyltriethoxysilane were added to 900g of a 10% (w / w) aqueous ethanol solution and stirred until homogeneous. The mixture was then sonicated for 15 min at a frequency of 75 kHz. Ascorbic acid was added and stirred until homogeneous. Under nitrogen protection, primary treated tin powder was added and stirred at 200 r / min at room temperature for 90 min. The mixture was then heated to 55℃ and stirred for another 25 min. The mixture was filtered, washed with anhydrous ethanol, and spray-dried at an inlet temperature of 70℃ and an outlet temperature of 50℃ to obtain secondary treated tin powder.

[0067] 15g of 3-aminopropyltriethoxysilane, PVP K30, and polyethylene glycol-polypropylene glycol-polyethylene glycol block copolymer were added to 550g of anhydrous ethanol and stirred until homogeneous to obtain the coating solution.

[0068] The secondary-processed tin powder was added to a fluidized bed at a bed temperature of 45°C. The coating liquid was atomized and sprayed into the fluidized bed while keeping the secondary-processed tin powder in a fluidized state. The mixture was then heat-treated at 55°C for 30 minutes, vacuum dried, and passed through a 200-mesh sieve.

[0069] A solder paste, comprising the following raw materials: 65g of the above-mentioned easily dispersible tin powder, 15g of rosin, 2g of carboxylated carbon nanotubes, 1.5g of nano-grade diatomaceous earth, 1.5g of 2-mercaptobenzimidazole, 3g of activator, and 15g of ethyl acetate. The activator is composed of diisooctyl fumarate, salicylamide, and pyridinecarboxylic acid in a mass ratio of 1.5:1.5:1.

[0070] The preparation method of the above solder paste includes the following steps: the above easily dispersible tin powder, rosin, carboxylated carbon nanotubes and ethyl acetate are mixed evenly, stirred at 75°C for 25 min, nano-sized diatomaceous earth is added and stirred for 10 min, 2-mercaptobenzimidazole and activator are added and stirred for 15 min.

[0071] Comparative Example 1: An easily dispersible tin powder, the raw materials of which include: 150g tin powder, 20g 3-aminopropyltriethoxysilane, 13g PVP K30, and 40g polyethylene glycol-polypropylene glycol-polyethylene glycol block copolymer.

[0072] The preparation method of the above-mentioned easily dispersible tin powder includes the following steps:

[0073] Tin powder with a particle size of 1-15μm was pickled with 3% hydrochloric acid for 15 minutes, washed with deionized water until neutral, and dried at 45℃ to obtain primary treated tin powder.

[0074] 3-aminopropyltriethoxysilane, PVP K30, and polyethylene glycol-polypropylene glycol-polyethylene glycol block copolymer were added to 550g of anhydrous ethanol and stirred until homogeneous to obtain a coating solution.

[0075] The primary tin powder was added to a fluidized bed at a bed temperature of 45°C. The coating liquid was atomized and sprayed into the fluidized bed while keeping the primary tin powder in a fluidized state. The mixture was then heat-treated at 55°C for 30 minutes, vacuum dried, and passed through a 200-mesh sieve.

[0076] A solder paste, comprising the following raw materials: 65g of the above-mentioned easily dispersible tin powder, 15g of rosin, 2g of carboxylated carbon nanotubes, 1.5g of nano-grade diatomaceous earth, 1.5g of 2-mercaptobenzimidazole, 3g of activator, and 15g of ethyl acetate. The activator is composed of diisooctyl fumarate, salicylamide, and pyridinecarboxylic acid in a mass ratio of 1.5:1.5:1.

[0077] The preparation method of the above solder paste includes the following steps: the above easily dispersible tin powder, rosin, carboxylated carbon nanotubes and ethyl acetate are mixed evenly, stirred at 75°C for 25 min, nano-sized diatomaceous earth is added and stirred for 10 min, 2-mercaptobenzimidazole and activator are added and stirred for 15 min.

[0078] Comparative Example 2: An easily dispersible tin powder, the raw materials of which include: 150g tin powder, 30g N-aminoethyl-3-aminopropylmethyldimethoxysilane, 20g 3-aminopropyltriethoxysilane, and 23g ascorbic acid.

[0079] The preparation method of the above-mentioned easily dispersible tin powder includes the following steps:

[0080] Tin powder with a particle size of 1-15μm was pickled with 3% hydrochloric acid for 15 minutes, washed with deionized water until neutral, and dried at 45℃ to obtain primary treated tin powder.

[0081] N-aminoethyl-3-aminopropylmethyldimethoxysilane and 5g of 3-aminopropyltriethoxysilane were added to 900g of a 10% (w / w) aqueous ethanol solution and stirred until homogeneous. The mixture was then sonicated for 15 min at a frequency of 75 kHz. Ascorbic acid was added and stirred until homogeneous. Under nitrogen protection, tin powder that had undergone primary treatment was added and stirred at 200 r / min at room temperature for 90 min. The mixture was then heated to 55℃ and stirred for another 25 min. The mixture was filtered, washed with anhydrous ethanol, and spray-dried at an inlet temperature of 70℃ and an outlet temperature of 50℃.

[0082] A solder paste, comprising the following raw materials: 65g of the above-mentioned easily dispersible tin powder, 15g of rosin, 2g of carboxylated carbon nanotubes, 1.5g of nano-grade diatomaceous earth, 1.5g of 2-mercaptobenzimidazole, 3g of activator, and 15g of ethyl acetate. The activator is composed of diisooctyl fumarate, salicylamide, and pyridinecarboxylic acid in a mass ratio of 1.5:1.5:1.

[0083] The preparation method of the above solder paste includes the following steps: the above easily dispersible tin powder, rosin, carboxylated carbon nanotubes and ethyl acetate are mixed evenly, stirred at 75°C for 25 min, nano-sized diatomaceous earth is added and stirred for 10 min, 2-mercaptobenzimidazole and activator are added and stirred for 15 min.

[0084] The oxygen content and dispersibility of the tin powder obtained in Example 5 and Comparative Examples 1-2 were determined as follows: (1) Each group of tin powder was placed in a drying oven at 35°C for 48 hours, and the oxygen content was tested by an oxygen and nitrogen tester; (2) The same mass of tin powder particles were poured into the test solution, stirred, and the clear liquid above was taken as the test sample and its absorbance was tested to characterize the dispersibility of the tin powder.

[0085] A higher oxygen content indicates a less than ideal coating effect of the adhesive layer, failing to completely prevent the tin powder from being oxidized. Lower absorbance indicates more severe agglomeration of the sample, shorter suspension time in solution, and poorer dispersion.

[0086] like Figure 1 As shown, the tin powder obtained in Example 5 has the lowest oxygen content and the highest absorbance, which is significantly better than that of Comparative Examples 1-2.

[0087] The thixotropic index and viscosity change rate of the solder pastes obtained in Example 5 and Comparative Examples 1-2 were tested as follows: (3) The thixotropic index of each group of solder pastes was measured at 25°C and 10 rpm using a viscometer; (4) Each group of solder pastes was placed in a constant temperature oven at 30°C for one week, and the viscosity change of each group of samples was measured.

[0088] A large change in viscosity indicates that the sample has a more serious aggregation problem during storage.

[0089] like Figure 2 As shown, the solder paste obtained in Example 5 has the highest thixotropic index and the lowest viscosity change rate, which is significantly better than Comparative Examples 1-2.

[0090] After normal soldering using the solder pastes obtained in Example 5 and Comparative Examples 1-2, the void phenomenon of the products after butt welding was detected by X-ray, and the void rate was calculated.

[0091] like Figure 3 As shown, the solder paste obtained using Example 5 has the lowest void ratio, which is significantly better than that of Comparative Examples 1-2.

[0092] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A readily dispersible tin powder, characterized in that, The raw materials thereof include, by mass fraction: tin powder 10-20 parts, N-aminoethyl-3-aminopropylmethyldimethoxysilane 1-2 parts, 3-aminopropyltriethoxysilane 1.1-3 parts, ascorbic acid 1-2 parts, polyvinylpyrrolidone 0.5-1 part, polyethylene glycol-polypropylene glycol-polyethylene glycol block copolymer 1-2 parts; The easily dispersible tin powder comprises: secondary treated tin powder and a coating layer coated on the outer side of the secondary treated tin powder; wherein the coating layer is formed by heat treatment after the secondary treated tin powder is embedded by a coating liquid; the raw materials of the coating liquid include: 3-aminopropyltriethoxysilane, polyvinylpyrrolidone, polyethylene glycol-polypropylene glycol-polyethylene glycol block copolymer and anhydrous ethanol; The secondary treated tin powder is prepared by the following steps: uniformly stirring N-aminoethyl-3-aminopropylmethyldimethoxysilane and 3-aminopropyltriethoxysilane in an ethanol aqueous solution, ultrasonic treatment for 10-20 min, uniformly stirring ascorbic acid added thereto, stirring for 1-2 h under nitrogen protection after adding primary treated tin powder, continuously stirring for 20-30 min after heating to 50-60℃, filtering, washing, and spray drying. The primary treated tin powder is obtained by acid washing and then water washing to neutral and drying after the tin powder is acid washed.

2. The readily dispersible tin powder according to claim 1, wherein In the preparation process of the secondary treated tin powder, the mass ratio of 3-aminopropyltriethoxysilane to N-aminoethyl-3-aminopropylmethyldimethoxysilane is 0.1-1:1-2.

3. The readily dispersible tin powder according to claim 1, wherein In the preparation process of the primary treated tin powder, the particle size of the tin powder is 1-15 μm; the acid washing is acid washing with 1-5% hydrochloric acid; and the drying temperature is 40-50℃.

4. A process for the production of the readily dispersible tin powder as claimed in any one of claims 1 to 3, characterized in that, The method comprises the following steps: adding the secondary treated tin powder into a fluidized bed with a bed temperature of 40-50℃, atomizing and spraying the coating liquid into the fluidized bed while keeping the secondary treated tin powder in a fluidized state, heat treating at 50-60℃ for 20-40 min, vacuum drying, and passing through a 200-mesh sieve.

5. A tin paste, characterized by, The raw materials thereof include, by mass fraction: the easily dispersible tin powder according to any one of claims 1-3 50-80 parts, rosin 10-20 parts, carboxylated carbon nanotube 1-3 parts, nano-sized diatomite 1-2 parts, antioxidant 1-2 parts, active agent 1-5 parts, and solvent 10-20 parts.

6. The solder paste of claim 5, wherein, The antioxidant is 2-mercaptobenzimidazole; and the solvent is ethyl acetate.

7. A method of producing the solder paste as claimed in claim 5 or 6, characterized by, The method comprises the following steps: uniformly mixing the easily dispersible tin powder according to any one of claims 1-3, rosin, carboxylated carbon nanotube and solvent, stirring at 70-80℃ for 20-30 min, continuously stirring for 5-15 min after adding nano-sized diatomite, and continuously stirring for 10-20 min after adding the antioxidant and active agent.

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