High-precision nano solder paste

Abstract

This application is a divisional application of application number 2023103425197. The present invention relates to the field of soldering materials technology. The present invention provides a high-precision nano-solder paste, which is composed of liquid solder, flux, additives, and solvent. The liquid solder is composed of nano-copper-antimony alloy, nano-tin, silver, acrylic resin, and isophorone diluent. By using nano-copper-antimony alloy and nano-tin as the main components of the liquid solder, the size of the solder joints after soldering is further reduced, meeting the high-precision soldering requirements of existing electronic devices. It has the advantages of small solder particle size, high oxidation resistance, long shelf life, and ease of promotion and implementation.

Description

[0001] This application is a divisional application. The original application has the application number 2023103425197, the application date is April 3, 2023, and the invention title is "High-precision nano solder paste and its preparation method". Technical Field

[0002] This invention belongs to the field of soldering materials technology, specifically relating to a high-precision nano solder paste. Background Technology

[0003] Solder paste is a new type of welding material that emerged with the development of surface mount technology (SMT). It is a paste-like mixture of solder powder, flux, etc. It is mainly used for soldering electronic components such as resistors, capacitors, and ICs on the PCB surface in the SMT industry. According to the particle size of the solder powder, solder paste can be divided into 3-8 grades. Among them, grade 8 solder paste refers to solder paste prepared using solder powder with a particle size of 2-8μm. With the significant increase in the precision of electronic devices such as mobile phones, the particle size of existing solder paste cannot meet the welding requirements of precision electronic components due to the limitations of equipment assembly specifications. Existing nano-metal powders have a large specific surface area, are more prone to oxidation during the welding process, and produce more solder slag and a high defect rate after welding, which is not conducive to the welding of electronic components. There is an urgent need for a high-precision nano-solder with higher precision and high oxidation resistance to meet the needs of iterative welding of electronic components. Summary of the Invention

[0004] To address the technical problem that existing solder pastes cannot meet the welding requirements of high-precision electronic components, this invention proposes a high-precision nano solder paste.

[0005] The second objective of this invention is to provide a method for preparing high-precision nano solder paste.

[0006] To achieve the first objective, this application adopts the following approach:

[0007] The high-precision nano solder paste is composed of the following components by weight: 75-82 parts liquid solder, 10-17 parts flux, 6-8 parts solvent, and 1-2 parts additives.

[0008] The liquid solder is composed of the following components by weight: 3-5 parts of nano copper-antimony alloy, 28-35 parts of nano tin, 1-3 parts of silver, 12-18 parts of acrylic resin, and 28-33 parts of isophorone diluent.

[0009] The flux is composed of the following components by weight: 5-7 parts film-forming agent, 2-3 parts activator, 1-2 parts thixotropic agent, 0.5-1 part etching inhibitor, and 0.5-1 part wetting agent.

[0010] Preferably, the solvent is one or more of ethanol, ethyl acetate, butyl acetate, and acetone; more preferably, the solvent is a mixture of ethanol, ethyl acetate, and acetone in a mass ratio of 1:3:0.5.

[0011] Preferably, the additive is composed of the following components in parts by weight: 0.5-1 parts of stabilizer and 0.5-1 parts of dispersant.

[0012] Preferably, the thixotropic agent is one or more of glyceryl tri-12-hydroxystearate, polyamide, and stearamide, the etching inhibitor is benzotriazole, and the wetting agent is OP-10. More preferably, the thixotropic agent is a 1:1 mixture of polyamide and stearamide. The film-forming agent, activator, and thixotropic agent, when combined, can significantly improve the spreadability of solder paste, thereby significantly increasing the coverage area of ​​solder paste on the pads.

[0013] Preferably, the activator is a mixture of oxalic acid, citric acid, and triethanolamine in a mass ratio of 1:1:2. It has excellent activity and moderate corrosivity, can efficiently remove oxides from the surface of the solder pads, and will not corrode the solder pads during the soldering process.

[0014] Preferably, the preparation method of the nano-copper-antimony alloy includes the following steps:

[0015] S101. Place the copper-antimony alloy block in a crucible and preheat and dry it at 40-60℃ for 5-20 minutes;

[0016] S102. Place the dried copper-antimony alloy in an electric arc plasma evaporator, use a vacuum pump to evacuate to a vacuum level of 0.03-0.056 MPa, and let it stand for 10-20 minutes.

[0017] S103. A mixture of hydrogen, argon and helium is introduced into an arc plasma evaporator at a pressure of 0.05-0.08 MPa. The copper-antimony alloy is evaporated at a cathode current of 580-650 A. After cooling, coarse nano-copper-antimony alloy with a particle size of 190-410 nm is obtained.

[0018] S104. Passivate the crude nano-copper-antimony alloy obtained in step S103 to obtain the nano-copper-antimony alloy.

[0019] Preferably, the preparation method of the copper-antimony alloy includes the following steps: adding 93 wt% copper and 7 wt% antimony to a crucible and melting at high temperature to obtain a liquid copper-antimony alloy; pouring the liquid copper-antimony alloy into a mold and cooling it to room temperature to obtain the copper-antimony alloy.

[0020] Preferably, the volume ratio of hydrogen, argon, and helium in step S103 is 1-3:5-8:1.

[0021] In practical applications, the copper-antimony alloy is placed in an arc plasma evaporator to evaporate it into copper-antimony vapor. A mixture of hydrogen, argon, and helium is then introduced, activating the copper-antimony vapor. This vapor then collides with the helium and argon to form nuclei, which settle to form coarse nano-sized copper-antimony alloys. The mixture is continuously introduced at a pressure of 0.05-0.08 MPa to ensure the copper-antimony vapor is fully activated and undergoes sufficient collisions with the inert gas to form nuclei, preventing incomplete reactions. After the reaction is complete, the nano-sized copper-antimony alloys are continuously protected from oxidation. Compared to traditional methods for preparing nano-metal particles, using an arc plasma evaporator significantly improves metal purity, reduces contact between nano-metal particles and oxygen, and lowers the content of metal oxides, resulting in nano-sized copper-antimony alloys with particle sizes of 100-568 nm.

[0022] Preferably, the passivation modification in step S104 includes the following steps: putting the coarse nano copper-antimony alloy obtained in step S103 into a magnetic stirrer containing a modifier, and stirring for 10-20 minutes at 40-55°C and 1200-1800 rpm.

[0023] Preferably, the modifier is a mixture of BTA, oxalic acid, anhydrous ethanol and polyethylene glycol in a mass ratio of 1-3:1:2-3:1.

[0024] In practical applications, the modification using a mixture of BTA, oxalic acid, anhydrous ethanol, and polyethylene glycol serves two purposes. First, by using a reducing medium to coat the nano-copper-antimony alloy, the oxidation resistance in an aerobic environment is enhanced, extending the shelf life of the solder paste. Second, after coating with a reducing medium, the compatibility of the nano-copper-antimony alloy with other components in the flux is improved, the degree of dispersion is enhanced, and sedimentation and agglomeration are prevented, thus disrupting the nanoparticle size distribution.

[0025] Preferably, the method for preparing nano-tin includes the following steps: tin powder, citric acid, and ethanol are sequentially added into an ultrasonic ball mill and ball-milled for 20-48 hours at 200-350 rpm and 25-35°C under ultrasonic vibration conditions, followed by filtration and drying to obtain the final product.

[0026] Preferably, the ball-to-material ratio of the ultrasonic ball mill is 100-150:1, the ultrasonic vibration frequency is 15-30kHz, and the power is 200-400W. More preferably, the grinding balls of the ultrasonic ball mill are stainless steel grinding balls with a diameter of 1.5-2mm.

[0027] In practical applications, tin powder pigments are ultrasonically ball-milled to a particle size of 200-500nm. Nano-tin is the main component of solder. Using ball milling can effectively reduce the cost of solder. Tin has high activity and is highly volatile when activated with hydrogen, which poses a high risk factor. In addition, tin has low hardness. Ball milling is easy to implement and has a high safety factor.

[0028] Preferably, the preparation method of the liquid solder includes the following steps: nano-copper-antimony alloy, nano-tin, silver, acrylic resin, and isophorone diluent are sequentially added to a magnetic stirrer and stirred for 1-2 hours at 500-1400 rpm and 25-30°C.

[0029] In practical applications, the nano-copper-antimony alloy, nano-tin, and silver are further coated with acrylic resin to further isolate them from oxygen. After coating with acrylic resin, the content of metal oxides is further reduced, the wettability and spread rate of the solder paste are significantly improved, and the soldering effect is significantly enhanced. Furthermore, after coating the nano-copper-antimony alloy, nano-tin, and silver with acrylic resin, and with the addition of additives and solvents, the residual substances on the solder plate after soldering are highly hydrophilic. The solder residue can be removed by soaking in a 78-90% ethanol solution for 3-5 minutes.

[0030] Preferably, the film-forming agent is one or more of hydrogenated rosin, disproportionated rosin, maleic rosin, and polymerized rosin; more preferably, the film-forming agent is a mixture of hydrogenated rosin and polymerized rosin in a 1:1 mass ratio.

[0031] To achieve the second objective, this application adopts the following technical solution:

[0032] A method for preparing high-precision nano solder paste includes the following steps:

[0033] S201. Add the film-forming agent, activator, thixotropic agent, etching inhibitor and wetting agent into the mixing tank in sequence and stir for 20-30 minutes at 40-50℃ and 300-420rpm to obtain the flux.

[0034] S202. Solder, flux, additives and solvent are sequentially added to a vacuum mixing vessel and stirred for 3-7 hours at 25-35℃ and 400-620rpm to obtain high-precision nano solder paste.

[0035] Compared with the prior art, this application has the following beneficial effects:

[0036] 1. This application provides a high-precision nano solder paste and its preparation method, which is composed of liquid solder, flux, additives, and solvent. The liquid solder is composed of nano copper-antimony alloy, nano tin, silver, acrylic resin, and isophorone diluent. By using nano copper-antimony alloy and nano tin as the main components of the liquid solder, the size of the solder joints after soldering is further reduced, which meets the high-precision soldering requirements of existing electronic devices. It has the advantages of small solder particle size, high oxidation resistance, long shelf life, and easy promotion and implementation.

[0037] 2. This application provides a method for preparing high-precision nano solder paste. By stirring solder, flux, additives and solvent in a vacuum environment, an environmentally friendly, low-residue and easy-to-clean solder paste is prepared. It has the advantages of wide application range, low environmental pollution, simple operation, strong reproducibility and low implementation cost. Detailed Implementation

[0038] The present invention will be further described below with reference to Tables 1-2 and specific embodiments 1-3:

[0039] (1) The preparation method of copper-antimony alloy includes the following steps:

[0040] 93 wt% copper and 7 wt% antimony were simultaneously added to a crucible and smelted at high temperature to obtain a liquid copper-antimony alloy. The liquid copper-antimony alloy was then poured into a mold and cooled to room temperature to obtain the final product.

[0041] Example 1

[0042] The preparation method of nano-copper-antimony alloy includes the following steps:

[0043] S101. Place the copper-antimony alloy block in a crucible and preheat and dry it at 42.5℃ for 18 min;

[0044] S102. Place the dried copper-antimony alloy in an electric arc plasma evaporator, use a vacuum pump to evacuate to a vacuum level of 0.037 MPa, and let it stand for 17 minutes.

[0045] S103. A mixture of hydrogen, argon and helium in a volume ratio of 1:5:1 is introduced into an arc plasma evaporator at 0.07 MPa. The copper-antimony alloy is evaporated at a cathode current of 625 A. After cooling, coarse nano-copper-antimony alloy with an average particle size of 217 nm is obtained.

[0046] S104. The crude nano-copper-antimony alloy obtained in step S103 is put into a magnetic stirrer containing a mixture of BTA, oxalic acid, anhydrous ethanol and polyethylene glycol in a mass ratio of 1:1:2:1, and stirred for 15 minutes at 47°C and 1325 rpm to obtain the nano-copper-antimony alloy.

[0047] The preparation method of nano-tin includes the following steps:

[0048] Tin powder, citric acid, and ethanol were added to an ultrasonic ball mill in a mass ratio of 1:0.5:2. The mixture was milled for 48 hours at 330 rpm, 35°C, a ball-to-material ratio of 145:1, an ultrasonic vibration frequency of 27 kHz, a power of 380 W, and stainless steel grinding balls with a diameter of 2 mm. After filtration and drying, nano-tin with an average particle size of 227 nm was obtained.

[0049] The preparation method of liquid solder according to the weight proportions shown in Table 1 includes the following steps:

[0050] The nano-copper-antimony alloy, nano-tin, silver, acrylic resin, and isophorone diluent are sequentially added to a magnetic stirrer and stirred at 662 rpm and 27°C for 1.2 hours to obtain the final product.

[0051] The preparation method of high-precision nano solder paste according to the weight parts shown in Table 2 includes the following steps:

[0052] S201. The film-forming agent, activator, thixotropic agent, etching inhibitor and wetting agent are added to the mixing tank in sequence and stirred at 41.5℃ and 381rpm for 25min to obtain the flux.

[0053] S202. Solder, flux, additives and solvent are sequentially added to a vacuum mixing vessel and stirred for 6.2 hours at 26°C, 420 rpm and a vacuum of 0.035 MPa to obtain high-precision nano solder paste.

[0054] Example 2

[0055] The preparation method of nano-copper-antimony alloy includes the following steps:

[0056] S101. Place the copper-antimony alloy block in a crucible and preheat and dry it at 51.5℃ for 12 min;

[0057] S102. Place the dried copper-antimony alloy in an electric arc plasma evaporator, use a vacuum pump to evacuate to a vacuum level of 0.045 MPa, and let it stand for 16 minutes.

[0058] S103. A mixture of hydrogen, argon and helium in a volume ratio of 2:7:1 is introduced into an arc plasma evaporator at 0.06 MPa. The copper-antimony alloy is evaporated at a cathode current of 611 A. After cooling, coarse nano-copper-antimony alloy with a particle size of 320 nm is obtained.

[0059] S104. The crude nano-copper-antimony alloy obtained in step S103 is put into a magnetic stirrer containing a mixture of BTA, oxalic acid, anhydrous ethanol and polyethylene glycol in a mass ratio of 2:1:2:1, and stirred for 16 minutes at 47.5°C and 1477 rpm to obtain the nano-copper-antimony alloy.

[0060] The preparation method of nano-tin includes the following steps:

[0061] Tin powder, citric acid, and ethanol were added to an ultrasonic ball mill in a mass ratio of 1:0.5:2. The mixture was milled for 37 hours at 311 rpm, 30°C, a ball-to-material ratio of 127:1, an ultrasonic vibration frequency of 21 kHz, a power of 333 W, and using stainless steel grinding balls with a diameter of 1.7 mm. After filtration and drying, nano-tin with an average particle size of 485 nm was obtained.

[0062] The preparation method of liquid solder according to the weight proportions shown in Table 1 includes the following steps:

[0063] The nano-copper-antimony alloy, nano-tin, silver, acrylic resin, and isophorone diluent are sequentially added to a magnetic stirrer and stirred at 856 rpm and 27.2°C for 1.5 hours to obtain the final product.

[0064] The preparation method of high-precision nano solder paste according to the weight parts shown in Table 2 includes the following steps:

[0065] S201. The film-forming agent, activator, thixotropic agent, etching inhibitor and wetting agent are added to the mixing tank in sequence and stirred at 45.5℃ and 401rpm for 26min to obtain the flux.

[0066] S202. Solder, flux, additives and solvent are sequentially added to a vacuum mixing vessel and stirred for 5.6 hours at 29.5℃, 544 rpm and a vacuum degree of 0.035 MPa to obtain high-precision nano solder paste.

[0067] Example 3

[0068] The preparation method of nano-copper-antimony alloy includes the following steps:

[0069] S101. Place the copper-antimony alloy block in a crucible and preheat and dry it at 42°C for 19 min;

[0070] S102. Place the dried copper-antimony alloy in an electric arc plasma evaporator, use a vacuum pump to evacuate to a vacuum level of 0.055 MPa, and let it stand for 18 minutes.

[0071] S103. A mixture of hydrogen, argon and helium in a volume ratio of 3:8:1 is introduced into an arc plasma evaporator at a pressure of 0.05 MPa. The copper-antimony alloy is evaporated at a cathode current of 589 A. After cooling, coarse nano-copper-antimony alloy with a particle size of 215 nm is obtained.

[0072] S104. The crude nano-copper-antimony alloy obtained in step S103 is put into a magnetic stirrer containing a mixture of BTA, oxalic acid, anhydrous ethanol and polyethylene glycol in a mass ratio of 1:1:3:1, and stirred for 20 minutes at 42.5°C and 1288 rpm to obtain the nano-copper-antimony alloy.

[0073] The preparation method of nano-tin includes the following steps:

[0074] Tin powder, citric acid, and ethanol were sequentially added into an ultrasonic ball mill. The mixture was milled for 33 hours at 315 rpm, 29°C, a ball-to-material ratio of 110:1, an ultrasonic vibration frequency of 25 kHz, a power of 350 W, and stainless steel grinding balls with a diameter of 1.8 mm. After filtration and drying, nano-tin with a particle size of 402 nm was obtained.

[0075] The preparation method of liquid solder according to the weight proportions shown in Table 1 includes the following steps:

[0076] The nano-copper-antimony alloy, nano-tin, silver, acrylic resin, and isophorone diluent are sequentially added to a magnetic stirrer and stirred at 1100 rpm and 28°C for 1.2 hours to obtain the final product.

[0077] The preparation method of high-precision nano solder paste according to the weight parts shown in Table 2 includes the following steps:

[0078] S201. The film-forming agent, activator, thixotropic agent, etching inhibitor and wetting agent are added to the mixing tank in sequence and stirred at 42°C and 411 rpm for 28 min to obtain the flux.

[0079] S202. Solder, flux, additives and solvent are sequentially added to a vacuum mixing vessel and stirred for 6.3 hours at 25-35℃, 541 rpm and a vacuum degree of 0.035 MPa to obtain high-precision nano solder paste.

[0080] Table 1. Composition of liquid solder by weight in Examples 1-3

[0081]

[0082] Table 2. Composition of solder paste by weight in Examples 1-3

[0083]

[0084] The solder paste performance of Examples 1-3 was tested according to IPC-TM-650 2.6.3.7:2007, IPC J-STD-004B, IPC-TM-6502.4.34.3l:1995, IPC-TM-650 2.4.45:1995, JIS-Z-31976.6.1, IPC-TM-650 2.3.32D:2004, IPC-TM-650 2.4.46A:2004, IEC 62149-2-21, IPC-TM-650 2.3.13:2004, and IPC-TM-6502.2.14.1:1995 standards. The test results are shown in Table 3 below.

[0085] Table 3 Test Results of Examples 1-3

[0086]

[0087] As shown in Table 3, in actual use, the copper-antimony alloy is placed in an arc plasma evaporator and evaporated into copper-antimony vapor. After passing through a mixture of hydrogen, argon, and helium, the copper-antimony vapor is activated by hydrogen and nucleates upon collision with helium and argon, settling to form coarse nano-copper-antimony alloy. Continuous passage of the mixture of hydrogen, argon, and helium ensures that the copper-antimony vapor is fully activated and fully collides with the inert gas to form nuclei, avoiding incomplete reaction of the copper-antimony alloy. After the reaction is complete, the nano-copper-antimony alloy is continuously protected from oxidation. Compared with traditional methods for preparing nano-metal particles, the use of an arc plasma evaporator can significantly improve the purity of the metal, reduce the contact between nano-metal particles and oxygen, and reduce the content of metal oxides. During the welding process, nano-tin and nano-copper-antimony alloys will not oxidize prematurely. The actual performance meets industry standards and can satisfy the needs of high-precision electronic equipment and nano-level welding.

[0088] In practical applications, a mixture of BTA, oxalic acid, anhydrous ethanol, and polyethylene glycol is used for modification. On the one hand, a reducing medium is used to coat the nano-copper-antimony alloy, which enhances its antioxidant properties in an aerobic environment and extends the shelf life of the solder paste. On the other hand, after coating with a reducing medium, the compatibility of the nano-copper-antimony alloy with other components in the flux is improved, the degree of dispersion is enhanced, and the agglomeration and aggregation of the nano-particles are prevented, thus disrupting the nano-particle size distribution.

[0089] In practical applications, nano-tin is the main component of solder. Ball milling can effectively reduce the cost of solder. Tin has high activity and is violently activated by hydrogen, which has a high risk factor. In addition, tin has low hardness. Ball milling is easy to implement and has a high safety factor.

[0090] In practical applications, the nano-copper-antimony alloy, nano-tin, and silver are further coated with acrylic resin to further isolate them from oxygen. After coating with acrylic resin, the content of metal oxides is further reduced, the wettability and spread rate of the solder paste are significantly improved, and the soldering effect is significantly enhanced. Furthermore, after coating the nano-copper-antimony alloy, nano-tin, and silver with acrylic resin, and with the addition of additives and solvents, the residual substances on the solder plate after soldering are highly hydrophilic. The solder residue can be removed by soaking in a 78-90% ethanol solution for 3-5 minutes.

[0091] This application provides a high-precision nano solder paste and its preparation method, which is composed of liquid solder, flux, additives, and solvent. The liquid solder is composed of nano copper-antimony alloy, nano tin, silver, acrylic resin, and isophorone diluent. By using nano copper-antimony alloy and nano tin as the main components of the liquid solder, the size of the solder joints after soldering is further reduced, which meets the high-precision soldering requirements of existing electronic devices. It has the advantages of small solder particle size, high oxidation resistance, long shelf life, and easy promotion and implementation.

[0092] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-precision nano solder paste, characterized in that, The components are composed of the following parts by weight: 75-82 parts liquid solder, 10-17 parts flux, 6-8 parts solvent, and 1-2 parts additives. The liquid solder is composed of the following components by weight: 3-5 parts of nano copper-antimony alloy, 28-35 parts of nano tin, 1-3 parts of silver, 12-18 parts of acrylic resin, and 28-33 parts of isophorone diluent. The flux is composed of the following components by weight: 5-7 parts film-forming agent, 2-3 parts activator, 1-2 parts thixotropic agent, 0.5-1 part etching inhibitor, and 0.5-1 part wetting agent. The preparation method of the nano-copper-antimony alloy includes the following steps: S101. Place the copper-antimony alloy block in a crucible and preheat and dry it at 40-60℃ for 5-20 minutes. S102. Place the dried copper-antimony alloy in an electric arc plasma evaporator, use a vacuum pump to evacuate to a vacuum level of 0.03-0.056 MPa, and let it stand for 10-20 minutes. S103. A mixture of hydrogen, argon and helium is introduced into an arc plasma evaporator at a pressure of 0.05-0.08 MPa. The copper-antimony alloy is evaporated at a cathode current of 580-650 A. After cooling, a coarse nano-copper-antimony alloy is obtained. S104. Passivate the crude nano-copper-antimony alloy obtained in step S103 to obtain the nano-copper-antimony alloy. The passivation modification in step S104 includes the following steps: The coarse nano-copper-antimony alloy obtained in step S103 is put into a magnetic stirrer containing a modifier and stirred for 10-20 minutes at 40-55°C and 1200-1800 rpm. The modifier is a mixture of BTA, oxalic acid, anhydrous ethanol and polyethylene glycol in a mass ratio of 1-3:1:2-3:1; The preparation method of the nano-tin includes the following steps: tin powder, citric acid and ethanol are sequentially added into an ultrasonic ball mill and ball milled for 20-48 hours at 200-350 rpm and 25-35℃ under ultrasonic vibration conditions, and then filtered and dried to obtain the nano-tin. The grinding balls in the ultrasonic ball mill are stainless steel grinding balls with a diameter of 1.5-2 mm; The nano-tin has a particle size of 200-500 nm.

2. The high-precision nano solder paste according to claim 1, characterized in that, In step S103, the volume ratio of hydrogen, argon, and helium is 1-3:5-8:

1.

3. The high-precision nano solder paste according to claim 1, characterized in that, The ball-to-material ratio of the ultrasonic ball mill is 100-150:1, and the ultrasonic vibration frequency is 15-30kHz.

4. The high-precision nano solder paste according to claim 1, characterized in that, The preparation method of the liquid solder includes the following steps: nano copper-antimony alloy, nano tin, silver, acrylic resin and isophorone diluent are sequentially added into a magnetic stirrer and stirred for 1-2 hours at 500-1400 rpm and 25-30℃.

5. The high-precision nano solder paste according to claim 1, characterized in that, The film-forming agent is one or more of hydrogenated rosin, disproportionated rosin, maleic rosin, and polymerized rosin.

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