A method for preparing a soldering paste by pre-pasting rosin and stepwise low-temperature emulsification

Abstract

The application discloses a method for preparing soldering paste by pre-pasting and step-by-step low-temperature emulsification of rosin, and relates to the technical field of electronic welding materials.The solid-state materials and liquid-state materials are finely grouped as follows: film-forming agent rosin resin is divided into a first solid-state group; blocky or granular active agents, thixotropic agents, antioxidants and corrosion inhibitors are divided into a second solid-state group; powder active agents, thixotropic agents, antioxidants and corrosion inhibitors are divided into a third solid-state group; part of organic solvents are divided into a first solvent group for pre-treating rosin; and the rest of the organic solvents and liquid additives are divided into a second solvent group.The method adopts pre-pasting of rosin combined with a three-step gradient temperature emulsification process, which not only protects the chemical activity of heat-sensitive components, but also solves the problem of difficult dispersion of high-viscosity rosin, and the prepared soldering paste only needs to be finely ground once, the total time consumption is shortened by more than 60% compared with the traditional process, and the dry resistance and expansion rate of the soldering paste are significantly improved.

Description

Technical Field

[0001] This invention relates to the field of electronic soldering materials technology, and more specifically to a method for preparing flux for solder paste. Background Technology

[0002] Solder paste is a key material for soldering electronic components, and flux, as its core component, has a decisive influence on its printing performance and final soldering quality. Solder paste mainly consists of film-forming agents, activators, thixotropic agents, solvents, and various functional additives. Currently, the mainstream flux preparation processes include high-temperature melting and emulsification milling.

[0003] The high-temperature melting method involves weighing rosin resin (a film-forming agent), activators, thixotropic agents, solvents, and various functional additives into a reaction vessel, heating the mixture, and stirring until the materials are completely melted. Heating is then stopped and the mixture is cooled to form solder paste. The heating temperature is typically 160-180℃. While this method achieves good fusion and uniform mixing of the materials, it has significant inherent drawbacks: Firstly, high temperatures easily cause low-melting-point materials (such as some activators, thixotropic agents, and hydrogenated rosin) to undergo thermal decomposition, producing harmful fumes and posing environmental and occupational health risks. Secondly, high temperatures damage the molecular structure of thixotropic agents, impairing their thixotropic properties. Simultaneously, activators lose activity due to thermal decomposition, ultimately affecting product quality.

[0004] The emulsification and milling method involves weighing film-forming agent rosin resin, activator, thixotropic agent, solvent, and various functional additives into an emulsifier according to a predetermined process. The emulsion is then cooled and milled to obtain solder paste. Compared to other methods, this method operates at a lower temperature (80–90°C), mitigating the problem of heat-sensitive component decomposition to some extent. However, this method still has significant limitations: First, high-viscosity resins such as rosin are difficult to effectively break down and disperse under conventional emulsification conditions. Second, the entire emulsification process is time-consuming, and the resulting paste contains large and unevenly distributed solid particles, typically requiring multiple cumbersome milling processes such as coarse grinding, fine grinding, and precision grinding to obtain a qualified product. Furthermore, this method is ineffective at removing impurities originally present in the rosin raw material. These residual residues can easily cause clogging during stencil printing in practical applications, severely affecting the stability and reliability of the welding process.

[0005] Existing technologies (such as CN102513734A) typically involve directly mixing and emulsifying rosin with other components after high-temperature melting, or simply performing a two-step cooling and feeding process. These methods have the following drawbacks: Impurities remain: When rosin is directly added to the whole component emulsification, the high viscosity makes it difficult to break down, and the insoluble residues inherent in the rosin raw material are difficult to remove, which can easily cause blockage in subsequent stencil printing or poor welding.

[0006] The equipment configuration requirements are stringent: ordinary emulsifiers use water and its steam as heating mediums with a maximum temperature of 100℃, while the CN102513734A technology requires stirring and heating rosin and solvents to 150℃, requiring high-boiling-point heat transfer oil as the heating medium. The equipment configuration, such as heat transfer pipes, valves, and sealing rings, requires special heat-resistant materials, which are expensive and difficult to maintain.

[0007] Low process efficiency: Due to the lack of pretreatment, the emulsification process takes a very long time, and the paste is rough after cooling. It must go through multiple processes of "coarse grinding-fine grinding-fine grinding", which is inefficient.

[0008] Limited operability: The emulsifier and its supporting control system are large-scale equipment with lifting functions, occupying a large area. When heated to 150℃, they will inevitably produce a large amount of toxic and harmful fumes, making it difficult to collect and discharge the exhaust gas, which is detrimental to the occupational health of operators.

[0009] In summary, existing technologies struggle to effectively protect the activity of heat-sensitive components while efficiently and uniformly dispersing high-viscosity resins, and to balance production efficiency with the overall performance of the final product. Summary of the Invention

[0010] The purpose of this invention is to solve the problems existing in the prior art and provide a new method for preparing solder paste that can protect the activity of heat-sensitive components, achieve efficient and uniform dispersion of high-viscosity materials such as rosin, and has a simple and efficient overall process.

[0011] The objective of this invention is achieved through the following technical solution: A method for preparing solder paste by rosin pre-greasing and stepwise low-temperature emulsification includes the following steps: (1) Fine grouping of materials: Solid materials are grouped as follows: rosin resin, a film-forming agent, is classified into the first solid group; activators, thixotropic agents, antioxidants, and corrosion inhibitors in block or granular form are classified into the second solid group; and activators, thixotropic agents, antioxidants, and corrosion inhibitors in powder form are classified into the third solid group. Grouping of liquid materials: A portion of the solvent is divided into the first solvent group for pretreatment of rosin; the remaining solvent and other liquid additives are mixed and divided into the second solvent group. (2) Pre-made rosin paste: The first solid component and the first solvent component are mixed and heated and stirred at 120℃~140℃ until the solid material is completely melted. After filtration and cooling, rosin paste is obtained. (3) Stepwise low-temperature emulsification: Step 1 Emulsification: The second solid component and the second solvent component are mixed and emulsified by stirring at 60℃~80℃ to obtain a suspension; The second step is emulsification: the suspension is cooled to 40℃~50℃, the third solid component is added, and the mixture is stirred and emulsified to obtain the basic emulsion. Third step emulsification: Add the rosin paste obtained in step (2) to the base emulsion, keep warm and stir to emulsify, and form a homogeneous paste; (4) Grinding the finished product: After cooling the homogenized cream to room temperature, it is finely ground once to obtain the flux paste.

[0012] Furthermore, in step (2), the filtration is carried out using a stainless steel screen with a mesh size of 200 to 325.

[0013] Furthermore, in step (3): The process parameters for the first step of emulsification are: emulsification dispersion head speed 1800-2000 rpm, stirring paddle speed 30-50 rpm, and emulsification time 30-45 minutes; The process parameters for the second step of emulsification are: emulsification dispersion head speed 2500-3000 rpm, stirring paddle speed 50-60 rpm, and emulsification time 30 minutes; The process parameters for the third step of emulsification are: emulsification dispersion head speed of 1500-3000 rpm, stirring paddle speed of 30-60 rpm, emulsification time of 30 minutes, and the speed of the emulsification dispersion head and stirring paddle are adjusted from slow to fast.

[0014] Furthermore, in step (4), a three-roll mill is used for a first fine grinding, with a fine grinding pressure of 25-35N, a rotation speed of 300-400rpm, and a roller temperature of 20-23℃.

[0015] The core of this invention lies in the rational grouping of materials with different properties and the use of appropriate processes for processing, specifically embodied in: The first solid group (rosin) is processed separately: the most refractory and viscous rosin is pre-made into a paste using the first solvent group at a medium temperature (120-140℃), and the residue is thoroughly removed by filtration, eliminating the risk of residue clogging the filter from the source.

[0016] Second solid component (blocks or granules) medium-temperature treatment: Blocks or granules are first emulsified with the second solvent component at 60-80℃. The viscosity is appropriately reduced by the temperature, which is conducive to the crushing of large particles.

[0017] The third solid group (powder) low-temperature protection: Powder materials are very easy to disperse but highly sensitive to heat. They are specially added at a low temperature of 40-50℃ to maximize the protection of their chemical activity from being destroyed.

[0018] One-step fine grinding: Since the first three steps have already processed the components to a micron-level dispersion state, only one fine grinding is required in the end. This grinds up the coarse crystal structure that is formed during the cooling process and meets the standard, eliminating the need for multiple grinding steps in traditional processes. The beneficial effects of this invention are as follows: It can protect the activity of heat-sensitive components, achieve efficient and uniform dispersion of high-viscosity materials such as rosin, and the overall process is simple and efficient. 1. Extremely high efficiency: The total preparation time is controlled at around 150 minutes, which is more than 60% shorter than the traditional emulsification and milling method (about 560 minutes).

[0019] 2. Excellent performance: The solder paste produced has an expansion rate of over 80%, a drying resistance of up to 72 hours, and thermal collapse performance that is superior to that of the high-temperature melting method.

[0020] 3. Environmental protection and safety: The maximum processing temperature does not exceed 140℃, avoiding the smog and harmful gases produced by temperatures above 160℃. Detailed Implementation

[0021] The invention will be further described below with reference to specific embodiments. Example 1

[0022] A method for preparing solder paste by rosin pre-greasing and stepwise low-temperature emulsification includes the following steps: (1) Raw material preparation and fine grouping of materials: To prepare 5 kg of solder paste, the following raw materials are prepared by weight percentage: KE604 rosin 18%, AX-E rosin 10%, P-105 rosin grease 6%, succinic acid activator 5% (powder), teicosuccinic acid activator 10% (block), ITOHWAX J-530 thixotropic agent 3% (granular), SUPER polyamide wax thixotropic agent 3% (powder), polyisobutylene additive 5% (liquid), 2-ethylimidazolium activator 5% (granular), benzotriazole 0.5% corrosion inhibitor (powder), methylbenzotriazole corrosion inhibitor 1.5% (granular), and tripropylene glycol butyl ether 33% (solvent).

[0023] Solid material grouping: First solid group (rosin resin): KE604 rosin + AX-E rosin + P-105 rosin resin; Second solid group (block and granular materials): Activator teicosinate (block) + thixotropic agent ITOHWAX J-530 (granular) + Activator 2-ethylimidazole (granular) + corrosion inhibitor methylbenzotriazole (granular); The third solid group (powdered material): succinic acid (powder) activator + SUPER polyamide wax (powder) thixotropic agent + benzotriazole (powder) corrosion inhibitor; Grouping of liquid materials: First solvent group: approximately 1 / 2 of the tripropylene glycol butyl ether solvent is used for pretreatment of rosin; Second solvent group: The remaining 1 / 2 tripropylene glycol butyl ether solvent + liquid polyisobutylene additive are mixed for emulsification and dispersion.

[0024] (2) Pre-prepared rosin paste: The first solid component (all rosin resin) and the first solvent component (tripropylene glycol butyl ether solvent) are added to the reaction vessel. The mixture is heated to 135°C and stirred until the rosin is completely melted into a transparent solution. The solution is then filtered through a 250-mesh stainless steel sieve. The filtrate is allowed to cool naturally to room temperature to obtain a uniform rosin paste.

[0025] (3) Stepwise low-temperature emulsification: Step 1: Emulsification: The second solvent group (a mixture of tripropylene glycol butyl ether solvent and liquid polyisobutylene additive) and the second solid group (activator icosanoic acid, thixotropic agent ITOHWAX J-530, activator 2-ethylimidazole, and corrosion inhibitor methylbenzotriazole) are added to the emulsification tank. The emulsification dispersion head speed is set to 1800 rpm, the stirring paddle speed is set to 30 rpm, the temperature is raised to 75℃, and after stirring and emulsifying for 35 minutes, the temperature is lowered.

[0026] The second step is emulsification: the temperature is lowered to 45℃, the third solid component (surfactant succinic acid, thixotropic agent SUPER polyamide wax, corrosion inhibitor benzotriazole) is added, the speed of the emulsification dispersion head is 3000 rpm, the speed of the stirring paddle is adjusted to 50 rpm, and the emulsification is continued for 30 minutes to obtain the basic emulsion.

[0027] The third step is emulsification: The rosin paste obtained in step (2) is added to the base emulsion for further emulsification. The speed of the emulsification dispersion head is adjusted to 3000 rpm and the speed of the stirring paddle is adjusted to 50 rpm. After emulsification for 30 minutes, a uniform cream is obtained, and the cream is naturally cooled to room temperature.

[0028] Finished product grinding: A hydraulic three-roll mill is used for grinding, with the following process parameters: pressure 25N, speed 380rpm, and roller temperature 23℃. The finished flux paste can be obtained in one fine grinding process. Example 2

[0029] A method for preparing solder paste by rosin pre-greasing and stepwise low-temperature emulsification includes the following steps: (1) Raw material preparation and fine grouping of materials: To prepare 5 kg of solder paste, the following raw materials are prepared by weight percentage: TSR-610 rosin 15%, 125 rosin 13%, KE-100 rosin resin 5%, activator adipic acid 8% (powder), activator teicosuccinic acid 8% (block), activator dibromobutenediol 0.2% (powder), thixotropic agent hydrogenated castor oil 8% (flakes), thixotropic agent 6650 amide wax 5% (powder), additive polyisobutylene 3% (liquid), activator 2-ethylimidazole 3% (flakes), corrosion inhibitor benzotriazole 0.8% (powder), corrosion inhibitor methylbenzotriazole 1.0% (granules), solvent tripropylene glycol butyl ether 16%, solvent diethylene glycol butyl ether 14%.

[0030] First solid group (rosin resin): TSR-610 rosin + 125 rosin + KE-100 rosin resin; Second solid group (block and granular materials): Activator teicosinate (block) + thixotropic agent hydrogenated castor oil (flake) + Activator 2-ethylimidazole (flake) + corrosion inhibitor methylbenzotriazole (granules). The third solid group (powdered material): activator adipic acid (powder) + activator dibromobutenediol (powder) + thixotropic agent 6650 amide wax (powder) + corrosion inhibitor benzotriazole (powder); First solvent group: diethylene glycol butyl ether; Second solvent group: tripropylene glycol butyl ether + additive liquid polyisobutylene.

[0031] (2) Pre-prepared rosin paste: The first solid component (all rosin resin) and diethylene glycol butyl ether are added to the reactor. The mixture is heated to 140°C and stirred until the rosin is completely melted into a transparent solution. The solution is then filtered through a 200-mesh stainless steel sieve. The filtrate is allowed to cool naturally to room temperature to obtain a homogeneous rosin paste.

[0032] (3) Stepwise low-temperature emulsification: Step 1: Emulsification: The second solvent group (a mixture of tripropylene glycol butyl ether and additive liquid polyisobutylene) and the second solid group (activator icosanoic acid, thixotropic agent hydrogenated castor oil, activator 2-ethylimidazole, and corrosion inhibitor methylbenzotriazole) are added to the emulsification tank. The emulsification dispersion head is set to 2000 rpm, the stirring paddle to 30 rpm, the temperature is raised to 85℃, and after stirring and emulsifying for 45 minutes, the temperature is lowered.

[0033] The second step is emulsification: the temperature is lowered to 45℃, the third solid component (activator dibromobutenediol, thixotropic agent 6650 amide wax, corrosion inhibitor benzotriazole) is added, the speed of the emulsification dispersing head is 1800 rpm, the speed of the stirring paddle is adjusted to 55 rpm, and the emulsification is continued for 30 minutes to obtain the basic emulsion.

[0034] The third step is emulsification: The rosin paste obtained in step (2) is added to the base emulsion for further emulsification. The speed of the emulsification dispersion head is adjusted to 2500 rpm and the speed of the stirring paddle is adjusted to 60 rpm. After emulsification for 30 minutes, a uniform cream is obtained, and the cream is naturally cooled to room temperature.

[0035] (4) Grinding the finished product: A hydraulic three-roll mill is used for grinding. The process parameters are: pressure 35N, speed 320rpm, and roller temperature 23℃. The finished flux can be obtained by grinding the paste in one step. Example 3

[0036] A method for preparing solder paste by rosin pre-greasing and stepwise low-temperature emulsification includes the following steps: (1) Raw material preparation and fine grouping of materials: To prepare 5 kg of solder paste, the following raw materials are prepared by weight percentage: KE604 rosin 11%, 685 rosin 22%, P-105 rosin resin 8%, sebacic acid 5% (granules), salicylic acid 4% (powder), tetrahydroxypropyl ethylenediamine 2% (liquid), hydrogenated castor oil 6% (flakes), ethylene bis-stearamide 6% (powder), and benzotriazole 1% (powder). Antioxidant 2,6-di-tert-butyl-p-cresol (BHT) 2% (granules), solvents diethylene glycol hexyl ether 15% and diethylene glycol butyl ether 18%.

[0037] First solid group (rosin resin): KE604 rosin + 685 rosin + P-105 rosin resin; Second solid group (lump and granular materials): Activator sebacic acid (granules) + thixotropic agent hydrogenated castor oil (flakes) + antioxidant 2,6-di-tert-butyl-p-cresol (BHT) (granules); The third solid group (powdered material): surfactant salicylic acid (powder) + corrosion inhibitor benzotriazole (powder) + thixotropic agent ethylene bis-stearamide (powder). First solvent group: diethylene glycol hexyl ether; Second solvent group: diethylene glycol butyl ether + additive liquid tetrahydroxypropyl ethylenediamine.

[0038] (2) Pre-prepared rosin paste: The first solid component (all rosin resin) and diethylene glycol hexyl ether are added to the reactor. The mixture is heated to 140°C and stirred until the rosin is completely melted into a transparent solution. The solution is then filtered through a 200-mesh stainless steel sieve. The filtrate is allowed to cool naturally to room temperature to obtain a homogeneous rosin paste.

[0039] (3) Stepwise low-temperature emulsification: Step 1: Emulsification: The second solvent group (a mixture of tripropylene glycol butyl ether and liquid tetrahydroxypropyl ethylenediamine) and the second solid group (surfactant sebacic acid, thixotropic agent hydrogenated castor oil, and antioxidant 2,6-di-tert-butyl-p-cresol BHT) were added to the emulsification tank. The emulsification dispersion head was set to 1800 rpm, the stirring paddle to 40 rpm, the temperature was raised to 85°C, and the mixture was stirred and emulsified for 38 minutes before cooling.

[0040] The second step is emulsification: the temperature is lowered to 45℃, the third solid component (surfactant salicylic acid, corrosion inhibitor benzotriazole, thixotropic agent ethylene bis-stearamide) is added, the speed of the emulsification dispersion head is 2800 rpm, the speed of the agitator is adjusted to 60 rpm, and the emulsification is continued for 30 minutes to obtain the basic emulsion.

[0041] Step 3: Emulsification: The rosin paste obtained in step (2) is added to the base emulsion for further emulsification. The speed of the emulsification dispersing head is adjusted to 1600 rpm, and the speed of the stirring paddle is adjusted to 60 rpm. After emulsification for 30 minutes, a homogeneous emulsion is obtained. Apply the cream and allow it to cool naturally to room temperature.

[0042] (4) Grinding the finished product: A hydraulic three-roll mill is used for grinding. The process parameters are: pressure 25N, speed 400rpm, and roller temperature 20℃. The finished flux can be obtained by grinding the paste in one step.

[0043] All raw materials with the same formula as those in Examples 1, 2, and 3 were used to obtain Comparative Example 1A, Comparative Example 1B, Comparative Example 2A, Comparative Example 2B, Comparative Example 3A, and Comparative Example 3B flux pastes by using the traditional emulsification and milling method and the high-temperature melting method, respectively.

[0044] Example and Comparative Examples and Performance Comparison: The fluxes prepared in Examples 1, 2, and 3, and Comparative Examples 1A, 1B, 2A, 2B, 3A, and 3B were respectively mixed with tin powder (Sn96.5Ag3.0Cu0.5) of the same alloy composition at a mass ratio of 11%:89% to prepare solder paste. The preparation time and the amount of fumes generated by organic decomposition are summarized in Table 1. The key properties of the solder paste, including high-temperature drying resistance, solder spread rate, and thermal collapse performance, are tested and are shown in Table 2.

[0045] Table 1 Comparison of flux preparation efficiency between examples and comparisons

[0046]

[0047] Table 2. Comparison of solder paste performance between the flux pastes of the examples and the comparative examples.

[0048]

[0049] Analyzing the above data, Table 1 (comparison of preparation efficiency) shows that the total preparation time for the three embodiments of the present invention is approximately 180-185 minutes, which is much shorter than that of the traditional emulsification method (560-565 minutes). Although it is longer than that of the high-temperature melting method (55-56 minutes), it is significantly more environmentally friendly (the present invention and the traditional emulsification method produce "very little" organic fumes, while the high-temperature melting method produces "a lot"). The overall evaluation is "relatively environmentally friendly and with suitable preparation time". Table 2 (comparison of solder paste performance) shows that the embodiments of the present invention perform better or on par with the embodiments of the present invention in terms of dryness resistance (no drying after 72 hours, which is better than the 36-48 hours of drying of the traditional emulsification method), solder expansion rate (81%-83%, which is higher than the 71% of the high-temperature melting method and the 77%-78% of the traditional emulsification grinding method), and thermal collapse resistance (bridging spacing of 0.06-0.10 mm, which is better than the 0.30-0.35 mm of the high-temperature melting method and comparable to the 0.06-0.10 mm of the traditional emulsification method).

[0050] As can be seen from Tables 1 and 2, the preparation method of the present invention significantly shortens the production time while taking into account environmental protection. At the same time, the key properties of the solder paste, such as dryness resistance and solder spread rate, are significantly improved. It solves the contradiction of "poor environmental protection" or "low efficiency and weak performance" of traditional processes, realizes the synergistic optimization of preparation efficiency and product performance, and obtains a flux product with the best comprehensive performance.

[0051] The equipment and devices used in the method of this invention, such as reaction kettles, emulsification cylinders, and three-roll mills, are all existing technology devices, and the raw materials involved are all commercially available raw materials.

[0052] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the corresponding technical solutions to depart from the protection scope of the present invention.

[0053] The core technology of this invention lies in the rational grouping of materials with different properties and the application of suitable processes, rather than the specific use of any particular rosin resin, activator, thixotropic agent, antioxidant, corrosion inhibitor, solvent, or liquid additive. The materials mentioned in this invention, such as film-forming rosin resin, block or granular activators, thixotropic agents, antioxidants, corrosion inhibitors, and powdered activators, thixotropic agents, antioxidants, corrosion inhibitors, solvents, and liquid additives, are not limited to the specific materials described in the above embodiments. Any rosin resin, activator, thixotropic agent, antioxidant, corrosion inhibitor, solvent, or liquid additive that can be used to prepare flux paste, regardless of its type, is divided into a first solid group, a second solid group, a third solid group, a first solvent group, and a second solvent group according to the fine grouping method of this invention. Rosin paste is then pre-prepared according to the method of this invention, followed by stepwise low-temperature emulsification, and finally milling to obtain the finished product. For those skilled in the art, determining the specific material composition for preparing flux paste and finely grouping the materials according to the method of this invention is not technically difficult.

[0054] Unless otherwise stated, all percentages mentioned in this invention are percentages by mass.

Claims

1. A method for preparing solder paste by rosin pre-grouting and stepwise low-temperature emulsification, characterized in that, Includes the following steps: (1) Fine grouping of materials: Solid materials are grouped as follows: rosin resin, a film-forming agent, is classified into the first solid group; activators, thixotropic agents, antioxidants, and corrosion inhibitors in block or granular form are classified into the second solid group; and activators, thixotropic agents, antioxidants, and corrosion inhibitors in powder form are classified into the third solid group. Grouping of liquid materials: A portion of the solvent is divided into the first solvent group for pretreatment of rosin; the remaining solvent and other liquid additives are mixed and divided into the second solvent group. (2) Pre-made rosin paste: The first solid component and the first solvent component are mixed and heated and stirred at 120℃~140℃ until the solid material is completely melted. After filtration and cooling, rosin paste is obtained. (3) Stepwise low-temperature emulsification: Step 1 Emulsification: The second solid component and the second solvent component are mixed and emulsified by stirring at 60℃~80℃ to obtain a suspension; The second step is emulsification: the suspension is cooled to 40℃~50℃, the third solid component is added, and the mixture is stirred and emulsified to obtain the basic emulsion. Third step emulsification: Add the rosin paste obtained in step (2) to the base emulsion, keep warm and stir to emulsify, and form a homogeneous paste; (4) Grinding the finished product: After cooling the homogenized cream to room temperature, it is finely ground once to obtain the flux paste.

2. The method for preparing solder paste by rosin pre-grouting and stepwise low-temperature emulsification according to claim 1, characterized in that, In step (2), the filtration is carried out using a stainless steel screen with a mesh size of 200 to 325.

3. The method for preparing solder paste by rosin pre-grouting and stepwise low-temperature emulsification according to claim 1, characterized in that, In step (3): The process parameters for the first step of emulsification are: emulsification dispersion head speed 1800-2000 rpm, stirring paddle speed 30-50 rpm, and emulsification time 30-45 minutes; The process parameters for the second step of emulsification are: emulsification dispersion head speed 2500-3000 rpm, stirring paddle speed 50-60 rpm, and emulsification time 30 minutes; The process parameters for the third step of emulsification are: emulsification dispersion head speed of 1500-3000 rpm, stirring paddle speed of 30-60 rpm, emulsification time of 30 minutes, and the speed of the emulsification dispersion head and stirring paddle are adjusted from slow to fast.

4. The method for preparing solder paste by rosin pre-grouting and stepwise low-temperature emulsification according to claim 1, characterized in that, In step (4), a three-roll mill is used for a first fine grinding, with a grinding pressure of 25-35N, a rotation speed of 300-400rpm, and a roller temperature of 20-23℃.

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