Halogen-free anti-splashing laser welding solder paste and preparation method thereof

Abstract

The invention discloses halogen-free anti-splashing laser welding solder paste and a preparation method thereof. The welding solder paste comprises, by mass, 80%-90% of Sn 96.5%, Ag 3.0% and Cu 0.5% solder powder, the flux paste comprises the following components in percentage by mass: 40%-60% of rosin, 10%-20% of rosin, 10%-20% of rosin, 10%-20% of rosin and 10%-20% of rosin; the mass content of the organic acid active agent in the flux paste is 3%-10%; the mass content of the thixotropic agent in the flux paste is 3%-10%; the mass content of the additive in the flux paste is 1%-3%; the balance is an organic solvent. According to the solder paste prepared through the method, high reliability of laser welding spots can be achieved, the problems of many residues and yellowing of scaling powder are solved, and the instantaneous high temperature of laser and the release rate of an active agent are synchronous.

Description

Technical Field

[0001] The present invention belongs to the technical field of solder paste materials, and particularly relates to a halogen-free anti-splash laser welding solder paste and a preparation method thereof. Background Art

[0002] In recent years, the rapid development of electronic technology has led to the development of electronic products towards high reliability, multi-function, small size and portability. Microelectronic connection technology plays a crucial role in the production of the electronics industry. Microelectronic welding technology is mainly applied to the interconnection and packaging of microelectronic devices. The core goal is to achieve high-precision and high-reliability electrical connections, while meeting the requirements of miniaturization, high-density integration and low thermal stress. The most common microelectronic welding processes include wave soldering, reflow soldering, thermocompression bonding and laser welding. The above-mentioned welding processes can well adapt to suitable solder joint structures and achieve high-efficiency automated production of products.

[0003] Among them, as an emerging technology, the laser welding process only locally heats the solder joint, which can avoid the overall thermal stress problem; through the direct action of the laser beam, without physical contact, the risk of mechanical damage can be reduced; with a high energy density, it can quickly melt the solder paste and improve the welding efficiency. The laser solder paste welding process uses solder paste as the welding filler metal, and uses a laser source to heat the filler metal. The filler metal melts, spreads and solidifies under the action of the laser heat source, and finally achieves the purpose of microelectronic solder joint connection.

[0004] In the application of laser welding solder paste, halogen compounds are widely used in traditional formulations because of their excellent oxide removal ability. However, halogen ions such as Cl- and Br remaining after welding with halogen-containing solder paste are extremely likely to cause metal electrochemical corrosion, especially in high-humidity, high-temperature and high-voltage working environments, which will significantly reduce the long-term reliability of devices. Therefore, the use of halogens is facing increasingly strict restrictions. - Etc. halogen ions are extremely likely to cause metal electrochemical corrosion, especially in high-humidity, high-temperature and high-voltage working environments, which will significantly reduce the long-term reliability of devices. Therefore, the use of halogens is facing increasingly strict restrictions.

[0005] The existing general-purpose SMT halogen-free solder paste system is prone to decomposition and failure during high-temperature laser welding, and it is necessary to increase the dosage to compensate for the loss of activity, which will in turn lead to an increase in flux residue and solder joint yellowing problems. And due to the instantaneous high temperature of laser welding, the general-purpose SMT halogen-free solder paste system will have problems such as solder explosion, solder ball splash and insufficient wettability due to the mismatch of the active release rate. Summary of the Invention

[0006] Aiming at the deficiencies of the existing technology, the present invention provides a halogen-free anti-splash laser welding solder paste and a preparation method thereof. The solder paste prepared by this method can achieve high reliability of laser solder joints, solve the problems of excessive flux residue and yellowing, and synchronize the laser instantaneous high temperature and the active agent release rate.

[0007] To achieve the above object, the present invention is realized by the following technical solutions: A halogen-free anti-splashing laser soldering paste, the soldering paste comprising:

[0008] Sn96.5Ag3.0Cu0.5 solder powder with a mass content of 80% to 90%;

[0009] Flux with a mass content of 10% to 20%, and the components of the flux are as follows:

[0010] Rosin: with a mass content of 40% to 60% in the flux;

[0011] Organic acid activator: with a mass content of 3% to 10% in the flux;

[0012] Thixotropic agent: with a mass content of 3% to 10% in the flux;

[0013] Additive: with a mass content of 1% to 3% in the flux;

[0014] The balance is organic solvent.

[0015] Preferably, the rosin is one or a combination of hydrogenated rosin, disproportionated rosin, polymerized rosin, water-white rosin, acrylic acid-modified rosin resin, maleic acid rosin resin;

[0016] The organic acid activator is one or a combination of succinic acid, adipic acid, methanedicarboxylic acid, glycolic acid, itaconic acid, malic acid, 1,3-propanedicarboxylic acid, sebacic acid, glycolic acid, diglycolic acid;

[0017] The thixotropic agent is one or a combination of hydrogenated castor oil, modified hydrogenated castor oil, cetylamide, stearamide, fatty acid polyamide, methylene stearamide, vinyl bisstearamide;

[0018] The organic solvent is one or a combination of diethylene glycol monoethyl ether, methoxydiethylene glycol, tripropylene glycol butyl ether, diethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monohexyl ether, diethylene glycol dibutyl ether, 1,2,6-hexanetriol;

[0019] The additive is one or a combination of benzotriazole, 2,6-di-tert-butyl-p-cresol, antioxidant 264, imidazole, methylimidazole, ethylimidazole, 2-ethylimidazole, benzimidazole, 2-pyridinecarboxylic acid.

[0020] The present invention also provides a preparation method of the halogen-free anti-splashing laser soldering paste, comprising the following steps:

[0021] Step (1): Add rosin and organic solvent into a reaction kettle, heat to 150 - 180 °C, stir until the rosin is completely dissolved to obtain a uniform rosin solution; stop heating, cool the temperature of the rosin solution to 100 - 130 °C, quickly add organic acid activators to the rosin solution, and continue to stir until the organic acid activators are fully dispersed and dissolved to form a mixture. Then transfer the above mixture to a sealed container and freeze and stand for 24 hours under the condition of -15 ± 5 °C.

[0022] Step (2): After the freezing is completed, take out the sealed container and let it stand and warm up at room temperature. After the sealed container warms up to room temperature, add a thixotropic agent and additives to the sealed container, and grind with a three-roll mill at least three times to obtain a soldering paste.

[0023] Step (3): Under normal temperature and pressure, add the alloy powder of Sn96.5Ag3.0Cu0.5 and the soldering paste prepared in Step (2) to a solder paste mixer according to a weight ratio of 20 - 10%:80 - 90%. After pre-stirring for 5 minutes, evacuate, and continue to stir for 35 minutes to obtain a halogen-free anti-splash laser welding solder paste.

[0024] Preferably, in Step (2), the roller spacings of the three rollers of the three-roll mill are 50 μm, 20 μm, and 5 μm in sequence, and the soldering paste with a fineness less than 10 μm is obtained after grinding.

[0025] Preferably, the preparation method of the halogen-free anti-splash laser welding solder paste includes the following steps:

[0026] Step A: Add 21.00 g of acrylic acid-modified rosin resin, 21.00 g of hydrogenated rosin, 15.00 g of polymerized rosin, 8.00 g of organic solvent diethylene glycol dibutyl ether, and 20.90 g of tetraethylene glycol dimethyl ether into a reaction kettle, heat to 150 - 180 °C, stir until part of the rosin is completely dissolved to obtain a uniform rosin solution; stop heating, cool the temperature of the rosin solution to 100 - 130 °C, quickly add 2.00 g of fatty acid, 1.50 g of succinic acid, and 2.00 g of diglycolic acid as organic acid activators to the rosin solution, and continue to stir until the organic acid activators are fully dispersed and dissolved to form a mixture. Transfer the above mixture to a sealed container and freeze and stand for 24 hours under the condition of -15 ± 5 °C;

[0027] Step B: After the freezing is completed, take out the sealed container and let it stand and warm up at room temperature. After the sealed container warms up to room temperature, add 4.50 g of thixotropic agent methylene stearic acid amide and 0.10 g of additive benzotriazole, 1.00 g of benzimidazole, and 3.00 g of 2-pyridinecarboxylic acid to the sealed container, and grind with a three-roll mill three times. The roller spacings of the three rollers of the three-roll mill are 50 μm, 20 μm, and 5 μm in sequence, and finally obtain a soldering paste with a fineness less than 10 μm;

[0028] Step C: At normal temperature and pressure, add the alloy powder of Sn96.5Ag3.0Cu0.5 and the soldering paste into a solder paste mixer according to a weight ratio of 13.50:86.50. After pre-stirring for 5 minutes, evacuate the air, and continue stirring for 35 minutes to obtain a halogen-free anti-splash laser welding solder paste.

[0029] Preferably, the preparation method of the halogen-free anti-splash laser welding solder paste includes the following steps:

[0030] Step A: Add 21.00 g of acrylic acid-modified rosin resin, 21.00 g of hydrogenated rosin, 15.00 g of polymerized rosin, 8.00 g of the organic solvent diethylene glycol dibutyl ether, and 20.90 g of 1,2,6-hexanetriol into a reaction kettle, heat to 150 - 180 °C, and stir until the rosin part is completely dissolved to obtain a uniform rosin solution; stop heating, cool the temperature of the rosin solution to 100 - 130 °C, quickly add 2.00 g of the organic acid activator adipic acid, 1.50 g of succinic acid, and 2.00 g of diglycolic acid to the rosin solution, and continue stirring until the organic acid activator is fully dispersed and dissolved to form a mixture. Transfer the above mixture to a sealed container and freeze and stand at -15 ± 5 °C for 24 hours;

[0031] Step B: After the freezing is completed, take out the sealed container and let it stand at room temperature to return to room temperature. After the sealed container returns to normal temperature, add 4.50 g of the thixotropic agent methylene stearic acid amide, 0.10 g of the additive benzotriazole, 1.00 g of benzimidazole, and 3.00 g of 2-pyridinecarboxylic acid to the sealed container, and grind it three times with a three-roll mill. The roller spacing of the three rollers of the three-roll mill is 50 μm, 20 μm, and 5 μm in sequence, and finally obtain a solder paste with a fineness of less than 10 μm;

[0032] Step C: At normal temperature and pressure, add the alloy powder of Sn96.5Ag3.0Cu0.5 and the solder paste into a solder paste mixer according to a weight ratio of 13.50:86.50. After pre-stirring for 5 minutes, evacuate the air, and continue stirring for 35 minutes to obtain a halogen-free anti-splash laser welding solder paste.

[0033] Preferably, the preparation method of the halogen-free anti-splash laser welding solder paste includes the following steps:

[0034] Step A: Add 21.00 g of acrylic modified rosin resin, 21.00 g of hydrogenated rosin, 15.00 g of polymerized rosin, 8.00 g of organic solvent diethylene glycol dibutyl ether, and 20.90 g of 1,2,6 - hexanetriol into a reaction kettle, heat to 150 - 180 °C, stir until the rosin part is completely dissolved to obtain a uniform rosin solution; stop heating, cool the temperature of the rosin solution to 100 - 130 °C, quickly add 2.00 g of organic acid activator oleic acid and 1.50 g of succinic acid to the rosin solution, and continue to stir until the organic acid activator is fully dispersed and dissolved to form a mixed solution. Transfer the above - mentioned mixed solution to a sealed container and freeze - stand at - 15 ± 5 °C for 24 hours;

[0035] Step B: After the freezing is completed, take out the sealed container and let it stand at room temperature to return to room temperature. After the sealed container returns to room temperature, add 4.50 g of thixotropic agent methylene stearic acid amide, 0.10 g of additive benzotriazole, 1.00 g of benzimidazole, and 5.00 g of 2 - picolinic acid to the sealed container, and grind it three times with a three - roll mill. The adjacent roller spacings of the three rollers of the three - roll mill are 50 μm, 20 μm, and 5 μm in sequence, and finally obtain a soldering paste with a fineness less than 10 μm;

[0036] Step C: For the soldering paste prepared in Step B, at normal temperature and pressure, add the alloy powder of Sn96.5Ag3.0Cu0.5 and the soldering paste into a solder paste mixer according to a weight ratio of 13.50:86.50, pre - stir for 5 minutes and then evacuate, and continue to stir for 35 minutes to obtain a halogen - free anti - splash laser - welding solder paste.

[0037] The halogen - free anti - splash laser - welding solder paste and its preparation method provided by the present invention have the following beneficial effects:

[0038] The solder paste prepared by the method of the present invention can achieve high reliability of laser solder joints, solve the problems of excessive flux residue and yellowing, and synchronize the laser instantaneous high temperature and the release rate of the activator. Brief Description of the Drawings

[0039] Figure 1 It is a process flow chart of the preparation method of the halogen - free anti - splash laser - welding solder paste of the present invention. Detailed Embodiments

[0040] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0041] The present invention provides a technical solution: a halogen - free anti - splash laser - welding solder paste, and the welding solder paste includes:

[0042] Sn96.5Ag3.0Cu0.5 solder powder with a mass content of 80% to 90%;

[0043] Soldering paste with a mass content of 10% to 20%, and the components of the soldering paste are as follows:

[0044] Rosin: the mass content in the soldering paste is 40% to 60%;

[0045] Organic acid activator: the mass content in the soldering paste is 3% to 10%;

[0046] Thixotropic agent: the mass content in the soldering paste is 3% to 10%;

[0047] Additive: the mass content in the soldering paste is 1% to 3%;

[0048] The balance is organic solvent.[[ID=——]]

[0049] Preferably, the rosin is one or a combination of hydrogenated rosin, disproportionated rosin, polymerized rosin, water-white rosin, acrylic acid-modified rosin resin, maleic acid rosin resin;

[0050] The organic acid activator is one or a combination of succinic acid, adipic acid, methanedicarboxylic acid, glycolic acid, itaconic acid, malic acid, 1,3-propanedicarboxylic acid, sebacic acid, glycolic acid, diglycolic acid;

[0051] The thixotropic agent is one or a combination of hydrogenated castor oil, modified hydrogenated castor oil, cetylamide, stearamide, fatty acid polyamide, methylene stearamide, vinyl bis-stearamide;

[0052] The organic solvent is one or a combination of diethylene glycol monoethyl ether, methoxy dipropylene glycol, tripropylene glycol butyl ether, diethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monohexyl ether, diethylene glycol dibutyl ether, 1,2,6-hexanetriol;

[0053] The additive is one or a combination of benzotriazole, 2,6-di-tert-butyl-p-cresol, antioxidant 264, imidazole, methylimidazole, ethylimidazole, 2-ethylimidazole, benzimidazole, 2-pyridinecarboxylic acid.

[0054] The halogen-free anti-splash laser soldering paste of the present invention does not contain traditional halogen-based activators and is applicable to application scenarios with strict long-term reliability requirements such as new energy vehicle controllers, communication equipment, and high-end industrial electronics.

[0055] The present invention also provides a preparation method of the halogen-free anti-splash laser soldering paste, as Figure 1 shown, including the following steps:

[0056] Step (1): Add rosin and an organic solvent into a reaction kettle, heat to 150 - 180 °C, stir until the rosin is completely dissolved to obtain a uniform rosin solution; stop heating, cool the temperature of the rosin solution to 100 - 130 °C, quickly add an organic acid activator to the rosin solution, and continue stirring until the organic acid activator is fully dispersed and dissolved to form a mixture. Then transfer the above mixture to a sealed container and freeze and stand for 24 hours at -15 ± 5 °C.

[0057] Step (2): After the freezing is completed, take out the sealed container and let it stand and warm up at room temperature. After the sealed container warms up to room temperature, add a thixotropic agent and additives to the sealed container, and grind with a three-roll grinder at least three times to obtain a soldering paste.

[0058] Step (3): Under normal temperature and pressure, add the alloy powder of Sn96.5Ag3.0Cu0.5 and the soldering paste into a solder paste mixer according to a weight ratio of 20 - 10%:80 - 90%, pre-stir for 5 minutes and then evacuate, and continue stirring for 35 minutes to obtain a halogen-free anti-splash laser welding solder paste.

[0059] Example 1:

[0060] Step A: Add 21.00 g of acrylic acid modified rosin resin, 21.00 g of hydrogenated rosin, 15.00 g of polymerized rosin, 8.00 g of the organic solvent diethylene glycol dibutyl ether, and 20.90 g of tetraethylene glycol dimethyl ether into a reaction kettle, heat to 150 - 180 °C, stir until part of the rosin is completely dissolved to obtain a uniform rosin solution; stop heating, cool the temperature of the rosin solution to 100 - 130 °C, quickly add 2.00 g of fatty acid, 1.50 g of succinic acid, and 2.00 g of diglycolic acid as organic acid activators to the rosin solution, and continue stirring until the organic acid activators are fully dispersed and dissolved to form a mixture. Transfer the above mixture to a sealed container and freeze and stand for 24 hours at -15 ± 5 °C;

[0061] Step B: After the freezing is completed, take out the sealed container and let it stand and warm up at room temperature. After the sealed container warms up to room temperature, add 4.50 g of methylene stearic acid amide as a thixotropic agent, 0.10 g of benzotriazole, 1.00 g of benzimidazole, and 3.00 g of 2-pyridinecarboxylic acid as additives to the sealed container, and grind with a three-roll grinder three times. The roller spacings of the three rollers of the three-roll grinder are 50 μm, 20 μm, and 5 μm in sequence, and finally obtain a soldering paste with a fineness of less than 10 μm;

[0062] Step C: Add the solder paste prepared in step B to a solder paste mixer at a weight ratio of 13.50:86.50, add the Sn96.5Ag3.0Cu0.5 alloy powder and the solder paste at room temperature and pressure, pre-stir for 5 minutes, then evacuate and continue stirring for 35 minutes to obtain a halogen-free, anti-splash laser welding solder paste.

[0063] Example 2:

[0064] Step A: adding 21.00 g of acrylic acid-modified rosin resin, 21.00 g of hydrogenated rosin, 15.00 g of polymerized rosin, 8.00 g of diethylene glycol dibutyl ether, and 20.90 g of 1,2,6-hexanetriol into a reaction kettle, heating to 150-180° C., and stirring until the rosin is completely dissolved to obtain a uniform rosin solution; stopping heating, cooling the rosin solution to 100-130° C., and rapidly adding organic acid activators such as adipic acid 2.00 g, succinic acid 1.50 g, and diglycolic acid 2.00 g to the rosin solution, and continuing stirring until the organic acid activator is fully dispersed and dissolved to form a mixed solution, transferring the mixed solution into a sealed container, and freezing and standing at -15±5° C. for 24 hours;

[0065] Step B: After the freezing is completed, the sealed container is taken out and allowed to stand at room temperature to return to normal temperature. After the sealed container returns to room temperature, 4.50 g of a thixotropic agent, methylene stearamide, and additives, 0.10 g of benzotriazole, 1.00 g of benzimidazole, and 3.00 g of 2-pyridinecarboxylic acid, are added to the sealed container, and the mixture is ground three times using a three-roll mill with the roller spacing of the three rollers of the three-roll mill being 50 μm, 20 μm, and 5 μm, to finally obtain a solder paste with a fineness of less than 10 μm;

[0066] Step C: Add the solder paste prepared in step B to a solder paste mixer at a weight ratio of 13.50:86.50, using Sn96.5Ag3.0Cu0.5 alloy powder and solder paste at room temperature and pressure. Pre-stir for 5 minutes and then evacuate. Continue stirring for 35 minutes to obtain a halogen-free, anti-spatter laser welding solder paste.

[0067] Example 3:

[0068] Step A: Add 21.00 g of acrylic modified rosin resin, 21.00 g of hydrogenated rosin, 15.00 g of polymerized rosin, 8.00 g of organic solvent diethylene glycol dibutyl ether, and 20.90 g of 1,2,6 - hexanetriol into a reaction kettle, heat to 150 - 180 °C, stir until part of the rosin is completely dissolved to obtain a uniform rosin solution; stop heating, cool the temperature of the rosin solution to 100 - 130 °C, quickly add 2.00 g of organic acid activator oleic acid and 1.50 g of succinic acid, and continue to stir until the organic acid activator is fully dispersed and dissolved to form a mixture. Transfer the above mixture to a sealed container and freeze - stand at - 15 ± 5 °C for 24 hours;

[0069] Step B: After the freezing is completed, take out the sealed container and let it stand at room temperature to return to room temperature. After the sealed container returns to room temperature, add 4.50 g of thixotropic agent methylene stearic acid amide, 0.10 g of additive benzotriazole, 1.00 g of benzimidazole, and 5.00 g of 2 - picolinic acid, and grind three times with a three - roll mill. The adjacent roll spacings of the three rolls of the three - roll mill are 50 μm, 20 μm, and 5 μm in sequence, and finally obtain a soldering paste with a fineness less than 10 μm;

[0070] Step C: For the soldering paste prepared in Step B, at normal temperature and pressure, add the alloy powder of Sn96.5Ag3.0Cu0.5 and the soldering paste into a solder paste mixer according to a weight ratio of 13.50:86.50, pre - stir for 5 minutes and then evacuate, and continue to stir for 35 minutes to obtain a halogen - free anti - splash laser - welding solder paste.

[0071] Example 4:

[0072] Step A: Add 21.00 g of acrylic modified rosin resin, 21.00 g of hydrogenated rosin, 15.00 g of polymerized rosin, 8.00 g of organic solvent diethylene glycol dibutyl ether, and 20.90 g of 1,2,6 - hexanetriol into a reaction kettle, heat to 150 - 180 °C, stir until part of the rosin is completely dissolved to obtain a uniform rosin solution; stop heating, cool the temperature of the rosin solution to 100 - 130 °C, quickly add 2.00 g of organic acid activator oleic acid, 1.50 g of succinic acid, and 5.00 g of diglycolic acid, and continue to stir until the organic acid activator is fully dispersed and dissolved; transfer the above mixture to a sealed container and freeze - stand at - 15 ± 5 °C for 24 hours;

[0073] Step B: After the freezing is completed, take out the sealed container and let it stand at room temperature to return to room temperature. After returning to room temperature, add 4.50 g of thixotropic agent methylene stearic acid amide, 0.10 g of additive benzotriazole, and 1.00 g of benzimidazole, and grind three times with a three - roll mill. The roll spacings are 50 μm, 20 μm, and 5 μm in sequence, and finally obtain a soldering paste with a fineness less than 10 μm;

[0074] Step C: For the soldering paste prepared in Step B, at normal temperature and pressure, alloy powder of Sn96.5Ag3.0Cu0.5 and the soldering paste are added to a solder paste mixer according to a weight ratio of 13.50:86.50. After pre-stirring for 5 minutes, vacuum is pumped, and after continuous stirring for 35 minutes, a halogen-free anti-splash laser welding solder paste is obtained.

[0075] The present invention uses diglycolic acid and imidazole compounds to replace traditional halogen-based activators. On the basis of meeting the requirement that the halogen content is less than 1500 ppm, it can still ensure excellent welding performance, and is applicable to application scenarios with strict long-term reliability requirements such as new energy vehicle controllers, communication equipment, and high-end industrial electronics.

[0076] The diglycolic acid molecule structure contains carboxyl and hydroxyl bifunctional groups, which can quickly release activity under the condition of instantaneous laser heating and quickly remove the metal surface oxide film. The imidazole compound has a heterocyclic aromatic structure and better thermal stability than traditional halogen-free organic acids, and can stably exist under the instantaneous high temperature generated by laser welding, avoiding premature decomposition and failure of the activator, and ensuring the continuous reduction ability during the entire wetting process. The synergistic effect of the two effectively solves the problem of increasing the dosage of the activator in the general-purpose SMT halogen-free solder paste system, and further solves the problems of increasing solder flux residue and yellowing.

[0077] Through the low-temperature freezing and segmented three-roll grinding process, the particle size in the soldering paste is controlled to below 10 μm, significantly improving the uniform dispersion and microscopic compatibility of each component, making the release of soldering activity more synchronous, further reducing the boiling explosion risk in the laser spot hot spot, and improving the stability and consistency of laser welding.

[0078] In summary, without using halogen active components, the present invention realizes high reliability of laser solder joints by synergistically combining an organic acid system and an imidazole-based activator with stable structure, supplemented by reasonable process design; solves the problems of more solder flux residue and yellowing; and achieves synchronization of the instantaneous high temperature of the laser and the release rate of the activator.

[0079] The halogen-free anti-splash laser welding solder paste prepared in the above four examples was tested to obtain the performance data of the halogen-free anti-splash laser welding solder paste prepared in different examples, as shown in the following table:

[0080]

[0081] Remarks: ○: The number of solder balls is 0 - 5, ○: The number of solder balls is 6 - 10, L: No penetrative corrosion of the copper film, M: Penetrative corrosion not greater than 50%

[0082] ND means not detected, below the method detection limit.

[0083] As can be seen from the above table, the soldering paste prepared by the method of the present invention has advantages over the traditional preparation method in terms of corrosion resistance, solder joint reliability, etc.

[0084] The above is only the preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, making equivalent substitutions or changes, should be covered within the protection scope of the present invention.

Claims

1. A halogen-free anti-splash laser soldering paste, characterized in that The solder paste includes: Sn96.5Ag3.0Cu0.5 solder powder with a mass content of 80% - 90%; Flux with a mass content of 10% - 20%, and the components of the flux are as follows: Rosin: with a mass content of 40% - 60% in the flux; Organic acid activator: with a mass content of 3% - 10% in the flux; Thixotropic agent: with a mass content of 3% - 10% in the flux; Additive: with a mass content of 1% - 3% in the flux; The balance is organic solvent.

2. The halogen-free anti-splash laser soldering paste according to claim 1, wherein: The rosin is one or a combination of hydrogenated rosin, disproportionated rosin, polymerized rosin, water-white rosin, acrylic acid-modified rosin resin, maleic acid rosin resin, etc.; The organic acid activator is one or a combination of succinic acid, adipic acid, methanedicarboxylic acid, glycolic acid, itaconic acid, malic acid, 1,3-propanedicarboxylic acid, sebacic acid, hydroxyacetic acid, diglycolic acid, etc.; The thixotropic agent is one or a combination of hydrogenated castor oil, modified hydrogenated castor oil, cetylamide, stearamide, fatty acid polyamide, methylene stearamide, vinyl bisstearamide, etc.; The organic solvent is one or a combination of diethylene glycol monoethyl ether, methoxydiethylene glycol, tripropylene glycol butyl ether, diethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monohexyl ether, diethylene glycol dibutyl ether, 1,2,6-hexanetriol, etc.; The additive is one or a combination of benzotriazole, 2,6-di-tert-butyl-p-cresol, antioxidant 264, imidazole, methylimidazole, ethylimidazole, 2-ethylimidazole, benzimidazole, 2-pyridinecarboxylic acid, etc.

3. A method for preparing a halogen-free anti-splash laser soldering paste according to any one of claims 1 to 2, characterized in that: It includes the following steps: Step (1): Add rosin and organic solvent into a reaction kettle together, heat to 150 - 180 °C, stir until the rosin is completely dissolved to obtain a uniform rosin solution; stop heating, cool the temperature of the rosin solution to 100 - 130 °C, quickly add the organic acid activator to the rosin solution, and continue to stir until the organic acid activator is fully dispersed and dissolved to form a mixture, then transfer the above mixture to a sealed container and freeze and stand at -15 ± 5 °C for 24 hours; Step (2): After the freezing is completed, take out the sealed container, let it stand and warm up at room temperature. After the sealed container warms up to room temperature, add the thixotropic agent and additive to the sealed container, and grind with a three-roll grinder at least three times to obtain the flux; Step (3): Under normal temperature and pressure, add the alloy powder of Sn96.5Ag3.0Cu0.5 and the flux to a solder paste mixer according to the weight ratio for the flux prepared in Step (2), pre-stir for 5 minutes and then evacuate, and continue to stir for 35 minutes to obtain a halogen-free anti-splash laser welding solder paste.

4. The preparation method of the halogen-free anti-splash laser soldering paste according to claim 3, characterized in that: In Step (2), the roller spacings of the three rollers of the three-roll grinder are 50 μm, 20 μm, and 5 μm in sequence, and the flux with a fineness less than 10 μm is obtained after grinding.

5. The preparation method of the halogen-free anti-splash laser soldering paste according to claim 3, characterized in that: It includes the following steps: Step A: Add 21.00 g of acrylic modified rosin resin, 21.00 g of hydrogenated rosin, 15.00 g of polymerized rosin, 8.00 g of organic solvent diethylene glycol dibutyl ether, and 20.90 g of tetraethylene glycol dimethyl ether into a reaction kettle, heat to 150 - 180 °C, stir until part of the rosin is completely dissolved to obtain a uniform rosin solution; stop heating, cool the temperature of the rosin solution to 100 - 130 °C, quickly add 2.00 g of organic acid activator oleic acid, 1.50 g of succinic acid, and 2.00 g of diglycolic acid to the rosin solution, and continue to stir until the organic acid activator is fully dispersed and dissolved to form a mixture. Transfer the above mixture to a sealed container and freeze and stand for 24 hours at -15 ± 5 °C; Step B: After the freezing is completed, take out the sealed container and let it stand at room temperature to return to room temperature. After the sealed container returns to room temperature, add 4.50 g of thixotropic agent methylene stearic acid amide, 0.10 g of additive benzotriazole, 1.00 g of benzimidazole, and 3.00 g of 2-pyridinecarboxylic acid to the sealed container, and grind three times with a three-roll mill. The roll spacings of the three rolls of the three-roll mill are 50 μm, 20 μm, and 5 μm in sequence, and finally obtain a soldering paste with a fineness less than 10 μm; Step C: Under normal temperature and pressure, add the alloy powder of Sn96.5Ag3.0Cu0.5 and the soldering paste prepared in Step B to a solder paste mixer according to a weight ratio of 13.50:86.50, pre-stir for 5 minutes and then evacuate, and continue to stir for 35 minutes to obtain a halogen-free anti-splash laser welding solder paste.

6. The preparation method of the halogen-free anti-splash laser soldering paste according to claim 3, characterized in that: It includes the following steps: Step A: Add 21.00 g of acrylic modified rosin resin, 21.00 g of hydrogenated rosin, 15.00 g of polymerized rosin, 8.00 g of organic solvent diethylene glycol dibutyl ether, and 20.90 g of 1,2,6-hexanetriol into a reaction kettle, heat to 150 - 180 °C, stir until part of the rosin is completely dissolved to obtain a uniform rosin solution; stop heating, cool the temperature of the rosin solution to 100 - 130 °C, quickly add 2. ​ Step C: Add the solder paste prepared in Step B, the alloy powder of Sn96.5Ag3.0Cu0.5 and the solder paste into a solder paste mixer according to the weight ratio of 13.50:86.50 under normal temperature and pressure. After pre-stirring for 5 minutes, evacuate the air, and continue to stir for 35 minutes to obtain a halogen-free anti-splash laser welding solder paste.

7. The preparation method of the halogen-free anti-splash laser soldering paste according to claim 3, characterized in that: The method includes the following steps: Step A: Add 21.00 g of acrylic acid modified rosin resin, 21.00 g of hydrogenated rosin, 15.00 g of polymerized rosin, 8.00 g of organic solvent diethylene glycol dibutyl ether, and 20.90 g of 1,2,6-hexanetriol into a reaction kettle, heat to 150 - 180 °C, stir until the rosin part is completely dissolved to obtain a uniform rosin solution; stop heating, cool the temperature of the rosin solution to 100 - 130 °C, quickly add 2.00 g of organic acid activator adipic acid and 1.50 g of succinic acid to the rosin solution, and continue to stir until the organic acid activator is fully dispersed and dissolved to form a mixed solution. Transfer the above mixed solution to a sealed container and freeze and stand at -15 ± 5 °C for 24 hours; Step B: After the freezing is completed, take out the sealed container and let it stand at room temperature to return to room temperature. After the sealed container returns to normal temperature, add 4.50 g of thixotropic agent methylene stearic acid amide, 0.10 g of additive benzotriazole, 1.00 g of benzimidazole, and 5.00 g of 2-pyridinecarboxylic acid to the sealed container, and grind it three times with a three-roll mill. The adjacent roll spacings of the three rolls of the three-roll mill are 50 μm, 20 μm, and 5 μm in sequence, and finally obtain a solder paste with a fineness of less than 10 μm; Step C: Add the solder paste prepared in Step B, the alloy powder of Sn96.5Ag3.0Cu0.5 and the solder paste into a solder paste mixer according to the weight ratio of 13.50:86.50 under normal temperature and pressure. After pre-stirring for 5 minutes, evacuate the air, and continue to stir for 35 minutes to obtain a halogen-free anti-splash laser welding solder paste.

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