A soldering paste suitable for laser soldering and a method for producing the same

Abstract

The application discloses a soldering paste suitable for laser welding and a preparation method thereof. The soldering paste is prepared by mixing a paste flux with alloy solder powder, wherein the mass ratio of the paste flux is 11.00%-13.00% of the mass of the soldering paste, and the rest is the alloy solder powder; the alloy solder powder is spherical alloy solder powder wrapped by an anti-splashing surface treatment agent, and the mass ratio of the spherical alloy solder powder to the anti-splashing surface treatment agent is (86-87):(1-2). The soldering paste prepared by the application is free of halogen, has high activity, good weldability and is not prone to splashing, and is particularly suitable for high-reliability laser welding scenes.

Description

Technical Field

[0001] This invention belongs to the field of electronic soft soldering materials technology, specifically relating to a solder paste suitable for laser soldering and its preparation method. Background Technology

[0002] As electronic components iterate towards miniaturization, high density, flexibility, and high reliability, traditional integral welding processes such as reflow soldering and wave soldering can no longer meet the requirements of precision welding. This is mainly because these processes adopt a full-area heating mode, which has a large heat-affected zone and strong thermal shock, making it easy to cause thermal damage to thermally sensitive components, flexible substrates, and micro-sized devices. In addition, the welding accuracy is low, making it difficult to adapt to the welding requirements of precision scenarios such as irregular structures, 01005 micro-components, Mini / Micro LEDs, optical modules, and MEMS devices.

[0003] Laser welding, with its advantages of localized instantaneous heating, small heat-affected zone, precise positioning, and non-contact welding, has become a core solution for precision electronic welding. However, conventional solder paste cannot adapt to the millisecond-level rapid heating characteristics of lasers, resulting in several technical defects: the activation rate of conventional solder paste flux does not match the laser heating rate, easily leading to severe solder splattering, solder splashing, and high void rates in solder joints; slow wetting speed and insufficient wetting properties result in poor solder joint formation and low bonding strength, severely restricting the large-scale application of laser welding technology.

[0004] Currently available laser solder pastes generally suffer from shortcomings such as poor anti-spatter effect and low solder joint reliability. There is a significant technological gap in dedicated solder pastes for micro-precision welding and welding of heat-sensitive substrates. To overcome these technical bottlenecks, there is an urgent need to develop a laser solder paste that is adapted to the rapid heating characteristics of lasers and features low spatter, high wettability, low thermal damage, zero halogen, and high reliability to meet the precision welding needs of high-end electronics manufacturing. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a laser solder paste product and its preparation method that is halogen-free, highly active, has good solderability and reliability, and is not prone to splashing.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A solder paste suitable for laser welding, wherein the solder paste is made by mixing a paste flux and an alloy solder powder, wherein the mass percentage of the paste flux is 11.00% to 13.00% of the solder paste mass, and the remainder is alloy solder powder; the alloy solder powder is spherical alloy solder powder coated with an anti-spatter surface treatment agent, and the mass ratio of the spherical alloy solder powder to the anti-spatter surface treatment agent is (86-87):(1-2). The mass content of each component in the paste flux is as follows: activator 6.00%~12.00%, wetting agent 0.10%~0.40%, thixotropic agent 5.00%~10.00%, solvent 40.00%~45.00%, with the balance being film-forming agent; the anti-spatter surface treatment agent is a mixture of diethylene glycol octyl ether, dimethyl silicone oil and 2,4,7,9-tetramethyl-5-decyn-4,7-diol in a mass ratio of (4~6):(2~4):(1~2); The surfactant is a compound of 2-phenylpropionic acid and a polybasic halogen-free organic acid with a boiling point of not less than 300℃ in a mass ratio of (1-2):1; the wetting agent is TEGO510. TEGO510 is an acetylenic diol nonionic surfactant wetting agent. Compared with organosilicon wetting agents and traditional nonionic wetting agents, it can quickly reduce dynamic surface tension, reduce the water absorption and defoaming / suppressing effect of the solder paste system, and reduce spatter.

[0007] Furthermore, the polybasic halogen-free organic acid with a boiling point of not less than 300°C is one of adipic acid, undecanoic acid, octadecanoic acid, or polydicarboxylic acid.

[0008] Furthermore, the thixotropic agent is CRAYVALLAC SL. This thixotropic agent is suitable for high-temperature production and application, and it possesses water resistance and splash resistance.

[0009] Furthermore, the film-forming agent is a mixture of KE-604 rosin and polymerized rosin 100 in a mass ratio of (1-3):1. This film-forming agent has a high softening point and acid value, good welding performance, and is not prone to spattering.

[0010] Furthermore, the organic solvent is a mixed solvent prepared by diethylene glycol hexyl ether and propylene glycol phenyl ether in a mass ratio of (1-3):1. It has a high boiling point and the solubility of alcohols, ethers and benzene, and can fully and quickly dissolve and homogenize other substances in the flux.

[0011] Furthermore, the alloy solder powder is one of Sn / Ag / Cu-X, Sn / Bi-X, Sn / Sb-X, and Sn / Pb-X alloy solder powders with a particle size of 5μm to 38μm.

[0012] The method for preparing solder paste suitable for laser welding according to the present invention is as follows: (1) Preparation of paste flux, the method is as follows: S1. Place the film-forming agent in the reactor and melt it at a temperature of 155℃~165℃; S2. Slowly add the solvent, surfactant and wetting agent to the molten film-forming agent in sequence, maintain the system temperature at 145℃~155℃, and stir for 8-12 minutes; S3. After cooling the material prepared in step S2 to 125℃~135℃, add the thixotropic agent and stir for 15-25 minutes; S4. After vacuum degassing the material prepared in step S3, cool it to room temperature to obtain a paste-like flux. (2) To prepare an anti-splatter surface treatment agent, diethylene glycol octyl ether and dimethyl silicone oil were added to the reaction vessel in proportion and stirred for 4 to 6 minutes. Then 2,4,7,9-tetramethyl-5-decyn-4,7-diol was added and stirred for 8 to 12 minutes to obtain the anti-splatter surface treatment agent. (3) Mix the alloy solder powder and the anti-spatter surface treatment agent at a mass ratio of (86-87): (1-2) and stir evenly so that the anti-spatter surface treatment agent is evenly coated on the surface of the alloy solder powder to form microcapsule-encapsulated spherical alloy solder powder. (4) Mix the paste flux with the spherical alloy solder powder evenly to obtain a solder paste suitable for laser welding.

[0013] The innovation and beneficial effects of this invention are as follows: This invention employs a method of encapsulating solder powder with anti-spatter agents, and combines a high-boiling-point activator (mainly 2-phenylpropionic acid) with a highly efficient wetting agent, a high-softening-point film-forming agent, and a high-boiling-point solvent to prepare a solder paste suitable for laser welding that features low spatter, high wettability, zero halogen, and high reliability. Firstly, each component in the anti-spatter microcapsule encapsulation agent used in this invention possesses high-temperature resistance and anti-spatter properties. Furthermore, through the weakly hydrophilic + strongly hydrophobic framework of hydroxyl groups and the dual hydrophobic chains + amphiphilic groups in 2,4,7,9-tetramethyl-5-decyn-4,7-diol, a dense monomolecular capsule wall layer is formed. This results in low water absorption and good water resistance in the powder / film layer, reducing spatter. Moreover, its adsorption efficiency is higher and its arrangement is more compact, significantly reducing static and dynamic surface tension and enhancing solderability. Secondly, this invention employs a compound system of high-boiling-point activator mainly composed of 2-phenylpropionic acid and a highly efficient wetting agent. The 2-phenylpropionic acid activator in this system exhibits better activity at high temperatures than commonly used activators, and its solderability is improved through compounding with a small amount of organic acid with a boiling point not lower than 300℃. Simultaneously, the addition of the highly efficient wetting agent TEGO510 not only reduces surface tension and enhances solderability but also reduces the water absorption and defoaming / suppressing effect of the solder paste system, thus reducing spatter.

[0014] The solder paste prepared by this invention is halogen-free, highly active, has good solderability, and is not prone to spattering, making it particularly suitable for high-reliability laser welding scenarios. Detailed Implementation

[0015] The present invention will be further illustrated below with reference to specific embodiments. These embodiments are merely typical implementations of the present invention and are not intended to limit the scope of protection of the present invention.

[0016] The solder paste suitable for laser welding described in this invention is made by mixing a paste flux and alloy solder powder, wherein the mass percentage of the paste flux is 11.00% to 13.00% of the solder paste mass, and the remainder is alloy solder powder; the alloy solder powder is spherical alloy solder powder coated with an anti-spatter surface treatment agent, and the mass ratio of the spherical alloy solder powder to the anti-spatter surface treatment agent is (86-87):(1-2); The mass content of each component in the paste flux is as follows: activator 6.00%~12.00%, wetting agent 0.10%~0.40%, thixotropic agent 5.00%~10.00%, solvent 40.00%~45.00%, with the balance being film-forming agent; the anti-spatter surface treatment agent is a mixture of diethylene glycol octyl ether, dimethyl silicone oil and 2,4,7,9-tetramethyl-5-decyn-4,7-diol in a mass ratio of (4~6):(2~4):(1~2); The activator is a compound of 2-phenylpropionic acid and a polybasic halogen-free organic acid with a boiling point of not less than 300°C in a mass ratio of (1-2):1; the wetting agent is TEGO510.

[0017] The polybasic halogen-free organic acid with a boiling point of not less than 300℃ is one of adipic acid, undecanoic acid, octadecanoic acid, polydicarboxylic acid, etc.

[0018] The thixotropic agent is CRAYVALLAC SL.

[0019] The film-forming agent is a mixture of KE-604 rosin and polymerized rosin 100 in a mass ratio of (1-3):1.

[0020] The organic solvent is a mixed solvent prepared by diethylene glycol hexyl ether and propylene glycol phenyl ether in a mass ratio of (1-3):1.

[0021] The alloy solder powder is one of Sn / Ag / Cu-X, Sn / Bi-X, Sn / Sb-X, and Sn / Pb-X alloy solder powders with a particle size of 5μm to 38μm.

[0022] The raw materials used in this invention, such as 2-phenylpropionic acid, adipic acid, undecanoic acid, octadecanoic acid, polydiic acid, TEGO 510, CRAYVALLAC SL, KE-604 rosin, polymeric rosin 100, diethylene glycol hexyl ether, propylene glycol phenyl ether, diethylene glycol octyl ether, dimethyl silicone oil, and 2,4,7,9-tetramethyl-5-decyn-4,7-diol, are all commercially available. Sn / Ag / Cu-X, Sn / Bi-X, Sn / Sb-X, and Sn / Pb-X alloy solder powders can all be prepared using existing technologies. Example 1

[0023] Prepare the paste flux raw materials according to the following mass ratio: 2-Phenylacetic acid 3.00%; Adipic acid 3.00%; TEGO510 0.10%; CRAYVALLAC SL 10.00%; Diethylene glycol hexyl ether 20.00%; Propylene glycol phenyl ether 20.00%; KE-604 rosin 21.95%; Polymerized rosin 100 21.95%.

[0024] Prepare solder paste suitable for laser welding using the following method: (1) Preparation of paste flux, the method is as follows: S1. Place KE-604 rosin and polymerized rosin 100 in a reactor and melt them at 160°C to obtain a film-forming agent; S2. In sequence, slowly add the solvent (diethylene glycol hexyl ether + propylene glycol phenyl ether), surfactant (2-phenylpropionic acid + adipic acid) and wetting agent (TEGO510) to the molten film-forming agent, maintain the system temperature at 150°C, and stir for 10 minutes. S3. After cooling the material prepared in step S2 to 130°C, add the thixotropic agent (CRAYVALLAC SL) and stir for 20 minutes; S4. After vacuum degassing the material prepared in step S3 (the production equipment has its own vacuum pump for degassing), cool it to room temperature to obtain a paste-like flux. (2) To prepare an anti-splatter surface treatment agent, add diethylene glycol octyl ether and dimethyl silicone oil to the reaction vessel in a weight ratio of 4:2:1, stir for 5 minutes, and then add 2,4,7,9-tetramethyl-5-decyn-4,7-diol and stir for 10 minutes to obtain the anti-splatter surface treatment agent. (3) Mix SnAg3.0Cu0.5 alloy solder powder with a particle size of 5μm to 15μm with an anti-spatter surface treatment agent at a weight ratio of 86:1 and stir evenly so that the anti-spatter surface treatment agent is evenly coated on the surface of the alloy solder powder to form microcapsule-encapsulated spherical alloy solder powder. (4) Mix the surface-treated spherical alloy solder powder and the paste flux at a weight ratio of 87:13 and stir evenly to obtain a solder paste suitable for laser welding. Example 2

[0025] Prepare the paste flux raw materials according to the following mass ratio: 2-Phenylacetic acid 5.00%; Undecanedioic acid 3.00%; TEGO510 0.20%; CRAYVALLAC SL 7.50%; Diethylene glycol hexyl ether 27.00%; Propylene glycol phenyl ether 13.50%; KE-604 rosin 29.20%; Polymerized rosin 100 14.60%.

[0026] Prepare solder paste suitable for laser welding using the following method: (1) Preparation of paste flux, the method is as follows: S1. Place KE-604 rosin and polymerized rosin 100 in a reactor and melt them at 165°C to obtain a film-forming agent; S2. In sequence, slowly add the solvent (diethylene glycol hexyl ether + propylene glycol phenyl ether), surfactant (2-phenylpropionic acid + undecanoic acid) and wetting agent (TEGO510) to the molten film-forming agent, maintain the system temperature at 155°C, and stir for 8 minutes. S3. After cooling the material prepared in step S2 to 135°C, add the thixotropic agent (CRAYVALLAC SL) and stir for 15 minutes; S4. After vacuum degassing the material prepared in step S3, cool it to room temperature to obtain a paste-like flux. (2) To prepare an anti-splatter surface treatment agent, add diethylene glycol octyl ether and dimethyl silicone oil to the reaction vessel in a weight ratio of 3:2:1, stir for 6 minutes, and then add 2,4,7,9-tetramethyl-5-decyn-4,7-diol and stir for 8 minutes to obtain the anti-splatter surface treatment agent. (3) Mix Sn42Bi58 alloy solder powder with a particle size of 25μm to 38μm with an anti-spatter surface treatment agent at a weight ratio of 86:2 and stir evenly so that the anti-spatter surface treatment agent is evenly coated on the surface of the alloy solder powder to form a microcapsule-encapsulated spherical alloy solder powder. (4) Mix the surface-treated spherical alloy solder powder and the paste flux at a weight ratio of 88:12 and stir evenly to obtain a solder paste suitable for laser welding. Example 3

[0027] Prepare the paste flux raw materials according to the following mass ratio: 2-Phenylacetic acid 6.00%; Octadecanedioic acid 3.00%; TEGO510 0.30%; CRAYVALLAC SL 10.00%; Diethylene glycol hexyl ether 33.75%; Propylene glycol phenyl ether 11.25%; KE-604 rosin 25.00%; Polymerized rosin 100% 10.70%; Prepare solder paste suitable for laser welding using the following method: (1) Preparation of paste flux, the method is as follows: S1. Place KE-604 rosin and polymerized rosin 100 in a reactor and melt them at 155°C to obtain a film-forming agent; S2. In sequence, slowly add the solvent (diethylene glycol hexyl ether + propylene glycol phenyl ether), surfactant (2-phenylpropionic acid + octadecanoic acid) and wetting agent (TEGO510) to the molten film-forming agent, maintain the system temperature at 145°C, and stir for 12 minutes. S3. After cooling the material prepared in step S2 to 125°C, add the thixotropic agent (CRAYVALLAC SL) and stir for 25 minutes; S4. After vacuum degassing the material prepared in step S3, cool it to room temperature to obtain a paste-like flux. (2) To prepare an anti-splatter surface treatment agent, add diethylene glycol octyl ether and dimethyl silicone oil to the reaction vessel in a weight ratio of 6:2:1, stir for 4 minutes, then add 2,4,7,9-tetramethyl-5-decyn-4,7-diol, stir for 12 minutes to obtain the anti-splatter surface treatment agent. (3) Mix SnSb5 alloy solder powder with a particle size of 20μm to 30μm with an anti-spatter surface treatment agent at a weight ratio of 87:1 and stir evenly so that the anti-spatter surface treatment agent is evenly coated on the surface of the alloy solder powder to form microcapsule-encapsulated spherical alloy solder powder. (4) Mix the surface-treated spherical alloy solder powder and the paste flux at a weight ratio of 88:12 and stir evenly to obtain a solder paste suitable for laser welding. Example 4

[0028] Prepare the paste flux raw materials according to the following mass ratio: 2-Phenylacetic acid 7.00%; Polydicarboxylic acid 5.00%; TEGO510 0.40%; CRAYVALLAC SL 5.00%; Diethylene glycol hexyl ether 30.00%; Propylene glycol phenyl ether 10.00%; KE-604 31.95%; Polymerized rosin 100% 10.65%; Prepare solder paste suitable for laser welding using the following method: (1) Preparation of paste flux, the method is as follows: S1. Place KE-604 rosin and polymerized rosin 100 in a reactor and melt them at a temperature of about 158°C to obtain a film-forming agent; S2. In sequence, slowly add the solvent (diethylene glycol hexyl ether + propylene glycol phenyl ether), surfactant (2-phenylpropionic acid + polydicarboxylic acid) and wetting agent (TEGO510) to the molten film-forming agent, maintain the system temperature at 150°C, and stir for 10 minutes. S3. After cooling the material prepared in step S2 to 130°C, add the thixotropic agent (CRAYVALLAC SL) and stir for 20 minutes; S4. After vacuum degassing the material prepared in step S3, cool it to room temperature to obtain a paste-like flux. (2) To prepare an anti-splatter surface treatment agent, diethylene glycol octyl ether and dimethyl silicone oil were added to the reaction vessel in a weight ratio of 2:1:1 and stirred for 5 minutes. Then 2,4,7,9-tetramethyl-5-decyn-4,7-diol was added and stirred for 10 minutes to obtain the anti-splatter surface treatment agent. (3) Mix Sn63Pb37 alloy solder powder with a particle size of 15μm to 25μm with an anti-spatter surface treatment agent at a weight ratio of 87:2 and stir evenly so that the anti-spatter surface treatment agent is evenly coated on the surface of the alloy solder powder to form microcapsule-encapsulated spherical alloy solder powder. (4) Mix the surface-treated spherical alloy solder powder and the paste flux at a weight ratio of 89:11 and stir evenly to obtain a solder paste suitable for laser welding.

[0029] The solder pastes prepared in Examples 1-4 were tested for performance indicators such as halogen content, spread rate, copper plate corrosion, and spatter. The test standards and results are shown in Table 1.

[0030] Table 1 Performance testing results of liquid flux

[0031] As can be seen from Table 1, the solder paste of the present invention has excellent properties such as zero halogen, high activity, good solderability, and low spatter, and is suitable for high-reliability laser welding scenarios.

Claims

1. A solder paste suitable for laser welding, characterized in that, The solder paste is made by mixing a paste flux and an alloy solder powder, wherein the mass percentage of the paste flux is 11.00% to 13.00% of the solder paste mass, and the remainder is alloy solder powder; the alloy solder powder is spherical alloy solder powder coated with an anti-spatter surface treatment agent, and the mass ratio of the spherical alloy solder powder to the anti-spatter surface treatment agent is (86-87):(1-2). The mass content of each component in the paste flux is as follows: activator 6.00%~12.00%, wetting agent 0.10%~0.40%, thixotropic agent 5.00%~10.00%, solvent 40.00%~45.00%, with the balance being film-forming agent; the anti-spatter surface treatment agent is a mixture of diethylene glycol octyl ether, dimethyl silicone oil and 2,4,7,9-tetramethyl-5-decyn-4,7-diol in a mass ratio of (4~6):(2~4):(1~2); The activator is a compound of 2-phenylpropionic acid and a polybasic halogen-free organic acid with a boiling point of not less than 300°C in a mass ratio of (1-2):1; the wetting agent is TEGO510.

2. The solder paste suitable for laser welding according to claim 1, characterized in that, The polybasic halogen-free organic acid with a boiling point of not less than 300℃ is one of adipic acid, undecanoic acid, octadecanoic acid, or polydicarboxylic acid.

3. The solder paste suitable for laser welding according to claim 1, characterized in that, The thixotropic agent is CRAYVALLAC SL.

4. The solder paste suitable for laser welding according to claim 1, characterized in that, The film-forming agent is a mixture of KE-604 rosin and polymerized rosin 100 in a mass ratio of (1-3):

1.

5. The solder paste suitable for laser welding according to claim 1, characterized in that, The organic solvent is a mixed solvent prepared by diethylene glycol hexyl ether and propylene glycol phenyl ether in a mass ratio of (1-3):

1.

6. A solder paste suitable for laser welding according to claim 1, 2, 3, 4, or 5, characterized in that, The alloy solder powder is one of Sn / Ag / Cu-X, Sn / Bi-X, Sn / Sb-X, and Sn / Pb-X alloy solder powders with a particle size of 5μm to 38μm.

7. A method for preparing solder paste suitable for laser welding as described in any one of claims 1-6, characterized in that, The method is as follows: (1) Preparation of paste flux, the method is as follows: S1. Place the film-forming agent in the reactor and melt it at a temperature of 155℃~165℃; S2. Slowly add the solvent, surfactant and wetting agent to the molten film-forming agent in sequence, maintain the system temperature at 145℃~155℃, and stir for 8-12 minutes; S3. After cooling the material prepared in step S2 to 125℃~135℃, add the thixotropic agent and stir for 15-25 minutes; S4. After vacuum degassing the material prepared in step S3, cool it to room temperature to obtain a paste-like flux. (2) To prepare an anti-splatter surface treatment agent, diethylene glycol octyl ether and dimethyl silicone oil were added to the reaction vessel in proportion and stirred for 4 to 6 minutes. Then 2,4,7,9-tetramethyl-5-decyn-4,7-diol was added and stirred for 8 to 12 minutes to obtain the anti-splatter surface treatment agent. (3) Mix the alloy solder powder and the anti-spatter surface treatment agent at a mass ratio of (86-87): (1-2) and stir evenly so that the anti-spatter surface treatment agent is evenly coated on the surface of the alloy solder powder to form microcapsule-encapsulated spherical alloy solder powder. (4) Mix the paste flux with the spherical alloy solder powder that has been treated with anti-spatter surface to obtain a solder paste suitable for laser welding.

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