A low-residue quick-drying laser soldering paste and a preparation method thereof

Abstract

This invention relates to the field of solder paste technology, specifically to a low-residue, fast-drying laser solder paste and its preparation method. The low-residue, fast-drying laser solder paste comprises the following raw materials in parts by weight: 80-92 parts alloy powder, 8-20 parts flux, and 1-2 parts silver-loaded titanium dioxide nanoparticles. The low-residue, fast-drying laser solder paste of this invention is highly practical. The prepared low-residue, fast-drying laser solder paste exhibits low post-soldering residue, good insulation and shear resistance, stable quality, and superior overall performance. The preparation method of the low-residue, fast-drying laser solder paste is process-controllable and easy to operate, which is beneficial for large-scale industrial production.

Description

Technical Field

[0001] This invention relates to the field of solder paste technology, specifically to a low-residue, fast-drying laser solder paste and its preparation method. Background Technology

[0002] Traditional SMT (Surface Mount Technology) technology mainly uses wave soldering and reflow soldering, which employs a total heating method. All PCB boards and electronic components must be heated for 3-6 minutes. However, the thermal expansion coefficients of each component are different, and the alternation of hot and cold can easily generate internal stress inside the component. The presence of internal stress reduces the fatigue strength of the solder joints and damages the reliability of electronic components.

[0003] Laser soldering is a relatively new industry that has seen rapid growth in recent years. It boasts advantages such as speed, minimal damage to surrounding components, and strong solder joints. However, because laser soldering can be completed in just a few seconds, the residue cannot dry completely and has no time to evaporate, resulting in a sticky, non-dry residue that is quite abundant. Summary of the Invention

[0004] In order to overcome the shortcomings and deficiencies of the existing technology, the purpose of this invention is to provide a low-residue, fast-drying laser solder paste. This low-residue, fast-drying laser solder paste has the characteristics of low post-soldering residue, as well as good insulation and shear resistance, and is highly practical.

[0005] Another objective of this invention is to provide a method for preparing a low-residue, fast-drying laser solder paste. This method is simple, easy to operate and control, and conducive to large-scale industrial production. The resulting low-residue, fast-drying laser solder paste has the characteristics of low post-soldering residue, as well as good insulation and shear resistance, exhibiting superior overall performance.

[0006] The objective of this invention is achieved through the following technical solution: a low-residue, fast-drying laser solder paste, comprising the following raw materials in parts by weight: 80-92 parts alloy powder, 8-20 parts flux, and 1-2 parts silver-loaded titanium dioxide nanoparticles.

[0007] The low-residue, fast-drying laser solder paste of the present invention is highly practical, can quickly complete soldering, has the characteristics of low post-soldering residue, good insulation and shear resistance, and has a short drying time.

[0008] Furthermore, the preparation method of the silver-loaded titanium dioxide nanoparticles is as follows: S1. Weigh 1-3g of nano titanium dioxide particles, disperse them in 1-2L of ethanol and ultrasonically disperse them evenly. Add 20-30mL of APTES ethanol solution with a volume fraction of 2-3% and 45-55mL of deionized water. Stir at low speed at room temperature for 2-3 hours. Wash the obtained product twice with deionized water and then wash it 3-4 times with ethanol to obtain pretreated titanium dioxide particles. S2. Disperse the pretreated titanium dioxide particles in 20-30 mL of glutaraldehyde dilution, stir and react for 3-4 h, then wash twice with deionized water and ethanol, and disperse in 15-25 mL of ethanol to obtain solution A. S3. Place the A solution system in a water bath at 75-85℃. Add 7-8 mL of silver ammonia solution to the A solution in three batches every 15-25 min. After the last addition is completed, continue the reaction for 18-22 min. After washing three times with ethanol by centrifugation, and screening for particles with a particle size of 20-30 nm, silver-loaded titanium dioxide nanoparticles can be obtained.

[0009] Furthermore, in step S2, the glutaraldehyde diluent is a 5% (v / v) glutaraldehyde diluent, and the diluent is a 0.1 mol / L phosphate buffer solution.

[0010] Furthermore, in step S3, the silver ammonia solution is prepared as follows: dilute ammonia water to a volume fraction of 2% with distilled water, and prepare a 0.2 mol / L zinc chloride solution with deionized water. Take a certain amount of silver chloride solution and pour it into a beaker. While stirring, slowly add the diluted ammonia solution dropwise until the precipitate just disappears.

[0011] Furthermore, the average particle size of the nano-titanium dioxide particles is 10-25 nm.

[0012] Furthermore, the alloy powder is specifically one or a combination of SnAgCu, SnBi, SnAg, SnCu, SnBiCu, SnBiAg, SnBiAgSb, and SnSb.

[0013] Furthermore, each portion of the flux contains the following raw materials in parts by weight: 5-15 parts rosin, 2-8 parts thixotropic agent, 3-6 parts organic acid activator, 1-3 parts organic amine activator, 20-45 parts organic solvent, 15-30 parts solid alkane, and 10-25 parts solid alcohol solvent.

[0014] Furthermore, the rosin is compounded from rosin A and rosin B in a weight ratio of 10:3-4. Rosin A is one or more of polymerized rosin, hydrogenated rosin, acidified rosin, hydrogenated rosin glycerol ester, and hydrogenated rosin ester. Rosin B is oleic acid modified rosin.

[0015] Furthermore, the preparation method of the oleic acid modified rosin is as follows: A1. Pulverize the aquamarine and put the pulverized aquamarine into a reactor. Add hydroquinone and stir evenly to obtain mixture B. A2. Under nitrogen protection, heat to 180-220℃, gradually add oleic acid dropwise to mixture B, and complete the addition within 1-2 hours. Continue to raise the system temperature to 225-235℃ and react for 4-5 hours. Then slowly lower the system temperature to about 170-180℃ to obtain oleic acid modified rosin.

[0016] Furthermore, the molar ratio of the aqueous rosin to oleic acid is 4-6:1, and the amount of hydroquinone used is 2.8-3.6% of the total amount of aqueous rosin and oleic acid.

[0017] Furthermore, the water-white rosin used is water-white rosin with a softening point of 105℃.

[0018] Furthermore, the thixotropic agent is at least one of hydrogenated castor oil, modified hydrogenated castor oil, or stearamide.

[0019] Furthermore, the organic acid activator is at least one selected from formic acid, acetic acid, propionic acid, benzoic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, or adipic acid.

[0020] Furthermore, the organic amine activator is at least one selected from dimethylamine, diethylamine, diisobutylamine, 1,5-dimethylhexylamine, ethanolamine, diethanolamine, triethanolamine, or triisopropanolamine.

[0021] Furthermore, the organic solvent is at least one selected from ethylene glycol monooctyl ether, glycerol, diethylene glycol monobutyl ether or diethylene glycol dibutyl ether, and 2-ethyl-1,3-hexanediol.

[0022] Furthermore, the solid alkane is at least one of trimethylolpropane, trimethylolethane, or trimethylolpropane.

[0023] Furthermore, the solid alcohol solvent is at least one of 1,2-octanediol or 2,5-dimethyl-2,5-hexanediol.

[0024] Furthermore, the method for preparing the low-residue, fast-drying laser solder paste includes the following steps: F1. Place rosin, thixotropic agent, organic acid, organic amine and organic solvent into an emulsification reactor, heat to 100-140℃, and stir under vacuum for 30-60 minutes to obtain mixture A; F2. Reduce the system temperature to 65-75℃, add solid alkane and solid alcohol solvent to mixture A and stir until dissolved, then cool to 25-35℃, pour out and place in a 1-10℃ cold storage to cool for more than 24 hours to obtain flux. F3. Weigh the prepared flux into a double planetary mixer according to the weight ratio, then weigh in the tin powder and silver-loaded titanium dioxide nanoparticles, vacuum stir for 8-12 minutes, then fill with nitrogen and stir for 30-40 minutes, then vacuum to -85 to -95 kPa and stir for 8-12 minutes to obtain a low-residue, fast-drying laser solder paste.

[0025] The preparation method of the low-residue, fast-drying laser solder paste of the present invention is controllable and easy to operate, which is conducive to large-scale industrial production. The low-residue, fast-drying laser solder paste has the characteristics of low post-soldering residue, good insulation and shear resistance, stable quality, and excellent comprehensive performance. The beneficial effects of this invention are as follows: the low-residue, fast-drying laser solder paste of this invention is highly practical. The resulting low-residue, fast-drying laser solder paste exhibits minimal post-soldering residue, excellent insulation and shear resistance, stable quality, and superior overall performance. The preparation method of the low-residue, fast-drying laser solder paste is simple, easy to control, and conducive to large-scale industrial production. Attached Figure Description

[0026] Figure 1 A schematic diagram of the improved lap-shear model; Figure 2 The appearance of the solder joint after laser soldering with low residue and fast drying laser solder paste in Example 1; Figure 3 The appearance of the solder joints after laser soldering is shown in Comparative Example 1. Figure 4 It is a comb-shaped circuit board. Detailed Implementation

[0027] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to embodiments. The content mentioned in the embodiments is not intended to limit the present invention.

[0028] Example 1 A low-residue, fast-drying laser solder paste comprises the following raw materials in parts by weight: 88 parts alloy powder, 11 parts flux, and 1 part silver-loaded titanium dioxide nanoparticles.

[0029] Furthermore, the preparation method of the silver-loaded titanium dioxide nanoparticles is as follows: S1. Weigh 1.5g of nano titanium dioxide particles, disperse them in 2L of ethanol and ultrasonically disperse them evenly. Add 25mL of 2% APTES ethanol solution and 50mL of deionized water, stir at low speed for 2.5 hours at room temperature, wash the obtained product twice with deionized water and then wash it three times with ethanol to obtain pretreated titanium dioxide particles. S2. Disperse the pretreated titanium dioxide particles in 25 mL of glutaraldehyde dilution solution, stir and react for 3.5 h, then wash twice with deionized water and ethanol, and disperse in 20 mL of ethanol to obtain solution A. S3. Place the A solution system in an 80℃ water bath. Add 7mL of silver ammonia solution to the A solution in three batches every 20min. After the last addition is completed, continue the reaction for 20min. After washing three times with ethanol by centrifugation, and screening for particles with a particle size of 20-30nm, silver-loaded titanium dioxide nanoparticles can be obtained.

[0030] Furthermore, in step S2, the glutaraldehyde diluent is a 5% (v / v) glutaraldehyde diluent, and the diluent is a 0.1 mol / L phosphate buffer solution.

[0031] Furthermore, in step S3, the silver ammonia solution is prepared as follows: dilute ammonia water to a volume fraction of 2% with distilled water, and prepare a 0.2 mol / L zinc chloride solution with deionized water. Take a certain amount of silver chloride solution and pour it into a beaker. While stirring, slowly add the diluted ammonia solution dropwise until the precipitate just disappears.

[0032] Furthermore, the average particle size of the nano-titanium dioxide particles is 10-25 nm.

[0033] Furthermore, the alloy powder is SnAgCu.

[0034] Furthermore, each portion of the flux contains the following raw materials in parts by weight: 5 parts rosin, 3 parts thixotropic agent, 4 parts organic acid activator, 3 parts organic amine activator, 30 parts organic solvent, 30 parts solid alkane, and 20 parts solid alcohol solvent.

[0035] Furthermore, the rosin is a compound of rosin A and rosin B in a weight ratio of 10:4, wherein rosin A is hydrogenated rosin and rosin B is oleic acid modified rosin.

[0036] Furthermore, the hydrogenated rosin is a hydrogenated rosin with a softening point of 100°C.

[0037] Furthermore, the preparation method of the oleic acid modified rosin is as follows: A1. Pulverize the aquamarine and put the pulverized aquamarine into a reactor. Add hydroquinone and stir evenly to obtain mixture B. A2. Under nitrogen protection, heat to 200℃, gradually add oleic acid dropwise to mixture B, and complete the addition within 1.5h. Continue to raise the system temperature to 230℃, react for 4.5h, and then slowly lower the system temperature to about 175℃ to obtain oleic acid modified rosin.

[0038] Furthermore, the molar ratio of the aqueous rosin to oleic acid is 5:1, and the amount of hydroquinone used is 3.1% of the total mass of the aqueous rosin and oleic acid.

[0039] Furthermore, the water-white rosin used is water-white rosin with a softening point of 105℃.

[0040] Furthermore, the thixotropic agent is stearamide.

[0041] Furthermore, the organic acid activator is glutaric acid.

[0042] Furthermore, the organic amine activator is triethanolamine.

[0043] Furthermore, the organic solvent is 2-ethyl-1,3-hexanediol.

[0044] Furthermore, the solid alkane is trihydroxymethyl alkane.

[0045] Furthermore, the solid alcohol solvent is 1,2-octanediol.

[0046] Furthermore, the method for preparing the low-residue, fast-drying laser solder paste includes the following steps: F1. Place rosin, stearamide, glutaric acid, triethanolamine and 2-ethyl-1,3-hexanediol into an emulsification reactor, heat to 140°C, and stir under vacuum for 50 min to obtain mixture A. F2. Reduce the system temperature to 70°C, add trimethylolpropane and 1,2-octanediol to mixture A and stir until dissolved, then reduce the temperature to 30°C, pour out and place in a 2°C cold storage to cool for more than 24 hours to obtain flux. F3. Weigh the prepared flux into a double planetary mixer according to the weight ratio, then weigh in the tin powder SnAgCu and silver-loaded titanium dioxide nanoparticles, vacuum stir for 10 minutes, then fill with nitrogen and stir for 40 minutes, then vacuum to -95Kpa and stir for 10 minutes to obtain a low-residue, fast-drying laser solder paste.

[0047] Example 2 In this embodiment, rosin A is polymerized rosin.

[0048] Furthermore, the polymerized rosin is a polymerized rosin with a softening point of 95°C.

[0049] Furthermore, the thixotropic agent is hydrogenated castor oil.

[0050] Furthermore, the method for preparing the low-residue, fast-drying laser solder paste includes the following steps: F1. Place rosin, stearamide, glutaric acid, triethanolamine and 2-ethyl-1,3-hexanediol into an emulsification reactor, heat to 140°C, and stir under vacuum for 50 min to obtain mixture A. F2. Reduce the system temperature to 70°C, add trimethylolpropane and 1,2-octanediol to mixture A and stir until dissolved, then reduce the temperature to 30°C, pour out and place in a 2°C cold storage to cool for more than 24 hours to obtain flux. F3. Weigh the prepared flux into a double planetary mixer according to the weight ratio, then weigh in the tin powder SnAgCu and silver-loaded titanium dioxide nanoparticles, vacuum stir for 10 minutes, then fill with nitrogen and stir for 40 minutes, then vacuum to -95Kpa and stir for 10 minutes to obtain a low-residue, fast-drying laser solder paste.

[0051] The rest of this embodiment is the same as that in Embodiment 1.

[0052] Example 3 In this embodiment, the thixotropic agent is modified hydrogenated castor oil.

[0053] Furthermore, the modified hydrogenated castor oil is ST modified hydrogenated castor oil.

[0054] Furthermore, the solid alkane is trimethylolpropane.

[0055] Furthermore, the solid alcohol solvent is 2,5-dimethyl-2,5-hexanediol.

[0056] Furthermore, the method for preparing the low-residue, fast-drying laser solder paste includes the following steps: F1. Place rosin, modified hydrogenated castor oil, glutaric acid, triethanolamine and 2-ethyl-1,3-hexanediol into an emulsification reactor, heat to 140°C, and stir under vacuum for 50 min to obtain mixture A. F2. Reduce the system temperature to 70°C, add trimethylolpropane and 2,5-dimethyl-2,5-hexanediol to mixture A and stir until dissolved, then reduce the temperature to 30°C, pour out and place in a 2°C cold storage to cool for more than 24 hours to obtain flux. F3. Weigh the prepared flux into a double planetary mixer according to the weight ratio, then weigh in the tin powder SnAgCu and silver-loaded titanium dioxide nanoparticles, vacuum stir for 10 minutes, then fill with nitrogen and stir for 40 minutes, then vacuum to -95Kpa and stir for 10 minutes to obtain a low-residue, fast-drying laser solder paste.

[0057] The rest of this embodiment is the same as that in Embodiment 1.

[0058] Comparative Example 1 In this comparative example, unlike Example 1, the laser solder paste of this comparative example uses an equal amount of rosin to replace solid alkanes and solid alcohol solvents.

[0059] Furthermore, the preparation method of laser solder paste includes the following: F1. Place rosin, stearamide, glutaric acid, triethanolamine and 2-ethyl-1,3-hexanediol into an emulsification reactor, heat to 140°C, vacuum stir for 50 min, then lower the system temperature to 30°C, pour out and place in a 2°C cold storage to cool for more than 24 h to obtain flux. F2. Weigh the prepared flux into a double planetary mixer according to the weight ratio, then weigh in the tin powder SnAgCu and silver-loaded titanium dioxide nanoparticles, vacuum stir for 10 minutes, then fill with nitrogen and stir for 40 minutes, then vacuum to -95Kpa and stir for 10 minutes to obtain laser solder paste.

[0060] Comparative Example 2 In this comparative example, unlike Example 1, the laser solder paste of this comparative example uses an equal amount of nano-titanium dioxide particles to replace an equal amount of silver-loaded titanium dioxide nanoparticles. The average particle size of the nano-titanium dioxide particles is 20-30 nm.

[0061] Furthermore, the preparation method of laser solder paste includes the following: F1. Place rosin, stearamide, glutaric acid, triethanolamine and 2-ethyl-1,3-hexanediol into an emulsification reactor, heat to 140°C, and stir under vacuum for 50 min to obtain mixture A. F2. Reduce the system temperature to 70°C, add trimethylolpropane and 1,2-octanediol to mixture A and stir until dissolved, then reduce the temperature to 30°C, pour out and place in a 2°C cold storage to cool for more than 24 hours to obtain flux. F3. Weigh the prepared flux into a double planetary mixer according to the weight ratio, then weigh in SnAgCu and nano titanium dioxide particles, vacuum stir for 10 minutes, then fill with nitrogen and stir for 40 minutes, then vacuum to -95Kpa and stir for 10 minutes to obtain laser solder paste.

[0062] Comparative Example 3 In this comparative example, unlike Example 1, the laser solder paste of this comparative example uses an equal amount of rosin A to replace rosin B, that is, the rosin is rosin A, which is hydrogenated rosin.

[0063] Furthermore, the preparation method of laser solder paste includes the following: F1. Hydrogenated rosin, stearamide, glutaric acid, triethanolamine and 2-ethyl-1,3-hexanediol are placed in an emulsification reactor, heated to 140°C, and stirred under vacuum for 50 min to obtain mixture A. F2. Reduce the system temperature to 70°C, add trimethylolpropane and 1,2-octanediol to mixture A and stir until dissolved, then reduce the temperature to 30°C, pour out and place in a 2°C cold storage to cool for more than 24 hours to obtain flux. F3. Weigh the prepared flux into a double planetary mixer according to the weight ratio, then weigh in the tin powder SnAgCu and silver-loaded titanium dioxide nanoparticles, vacuum stir for 10 minutes, then fill with nitrogen and stir for 40 minutes, then vacuum to -95Kpa and stir for 10 minutes to obtain laser solder paste.

[0064] Performance testing The performance of the low-residue, fast-drying laser solder pastes prepared in Examples 1-3 and Comparative Examples 1-3 was tested. The tests included whether there was flux residue at the solder joints after laser soldering, the solder joint spreading area, and the post-soldering shear resistance. The test data are shown in Table 1 below: Table 1

[0065] Among them, the residual percentage test of flux paste: Take a 15mm×15mm×1mm single-sided copper-clad board after surface grinding and wiping, and use a stainless steel template with a thickness of 0.25mm and an opening of Ф6.5mm to print solder paste on the center of the substrate. Then weigh the mass of the Cu substrate and the total mass of the solder joint and the substrate before and after soldering. Calculate the residual percentage (η) after soldering according to the following formula (1).

[0066] η=(m1-m2) / α (m1-m0)(1) In formula (1), m1 is the mass of the substrate after the solder paste is printed, g; m2 is the total mass of the substrate and solder joint after soldering, g; α is the mass fraction of the flux; and m0 is the mass of the Cu substrate, g.

[0067] Insulation resistance test: Take a comb-shaped circuit board with a line width of 0.4 mm and a spacing of 0.5 mm. Remove the oxide film with a 1:2 volume ratio hydrochloric acid solution, wash with water, and dry with ethanol. Use a stencil (0.15 mm thick) to evenly print solder paste onto the comb-shaped circuit board. Place the printed solder paste-covered circuit board in a dryer set at 150℃ for 2 minutes, then melt it on a heating plate at 265℃ for 30 seconds. Remove and cool. The test sample is now complete. Connect the electrodes with a coaxial cable and apply a 50V-DC bias voltage. The sample should be installed in a clean, constant temperature and humidity test chamber at 85℃ and 85% for 168 hours of damp heat test, and the resistance value after 168 hours of damp heat test should be measured.

[0068] Shear resistance test: such as Figure 1 As shown, an improved lap-shear model was used, with a copper strip measuring 30×5×1mm as the base material. Small copper blocks measuring 20*5*1mm were added to both sides of the original lap-shear model to ensure that the tensile specimen was subjected to parallel shear forces. During the soldering process, a 5*5*0.2mm opening stencil was used to print solder paste onto the surface of the copper sheet, ensuring consistent solder paste usage for each soldering attempt. Finally, laser soldering was used to complete the soldering. The shear properties of the solder joints were then tested using an electronic universal testing machine with a 0-9mm seamless chuck and a tensile rate of 1mm / min.

[0069] like Figure 2-3 As shown, Figure 2 The appearance of the solder joints after laser soldering with low residue and fast drying laser solder paste in Example 1 is shown. The area around the solder joints formed by the solder paste in Example 1 is relatively clean, with no black residue.

[0070] and Figure 3 The appearance of the solder joints after laser soldering is shown in Comparative Example 1. The solder joints formed by the solder paste in Comparative Example 1 contain black substances.

[0071] The above embodiments are preferred implementations of the present invention. In addition, the present invention can be implemented in other ways. Any obvious substitutions without departing from the concept of the present invention are within the protection scope of the present invention.

Claims

1. A low-residue, fast-drying laser solder paste, characterized in that, The raw materials include the following parts by weight: 80-92 parts alloy powder, 8-20 parts flux, and 1-2 parts silver-loaded titanium dioxide nanoparticles; each part of the flux contains the following parts by weight: 5-15 parts rosin, 2-8 parts thixotropic agent, 3-6 parts organic acid activator, 1-3 parts organic amine activator, 20-45 parts organic solvent, 15-30 parts solid alkane, and 10-25 parts solid alcohol solvent; the rosin is a compound of rosin A and rosin B in a weight ratio of 10:3-4, wherein rosin A is at least one of polymerized rosin, hydrogenated rosin, acidified rosin, hydrogenated rosin glycerol ester, and hydrogenated rosin ester, and rosin B is oleic acid modified rosin; The alloy powder is specifically one or more combinations of SnAgCu, SnBi, SnAg, SnCu, SnBiCu, SnBiAg, SnBiAgSb, and SnSb; The thixotropic agent is at least one of hydrogenated castor oil, modified hydrogenated castor oil, or stearamide. The organic acid activator is at least one of formic acid, acetic acid, propionic acid, radical acid, oxalic acid, malonic acid, succinic acid, glutaric acid, or adipic acid. The organic amine activator is at least one selected from dimethylamine, diethylamine, diisobutylamine, 1,5-dimethylhexylamine, ethanolamine, diethanolamine, triethanolamine, or triisopropanolamine; The organic solvent is at least one of ethylene glycol monooctyl ether, glycerol, diethylene glycol monobutyl ether, diethylene glycol dibutyl ether, or 2-ethyl-1,3-hexanediol; The solid alkane is at least one of trimethylolpropane, trimethylolethane, or trimethylolpropane. The solid alcohol solvent is at least one of 1,2-octanediol or 2,5-dimethyl-2,5-hexanediol.

2. A method for preparing the low-residue, fast-drying laser solder paste according to claim 1, characterized in that: The preparation method includes the following: F1. Place rosin, thixotropic agent, organic acid, organic amine and organic solvent into an emulsification reactor, heat to 100-140℃, and stir under vacuum for 30-60 minutes to obtain mixture A; F2. Reduce the system temperature to 70℃, add solid alkane and solid alcohol solvent to mixture A and stir until dissolved, then cool to 25-35℃, pour out and place in a 1-10℃ cold storage to cool for more than 24 hours to obtain flux. F3. Weigh the prepared flux into a double planetary mixer according to the weight ratio, then weigh in the tin powder and silver-loaded titanium dioxide nanoparticles, vacuum stir for 8-12 minutes, then fill with nitrogen and stir for 30-40 minutes, then vacuum to -85 to -95 kPa and stir for 8-12 minutes to obtain a low-residue, fast-drying laser solder paste.

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