High-precision nano soldering paste

Abstract

The invention relates to a divisional application of which the application number is 2023103425197. The invention relates to the technical field of tin soldering materials. The invention provides high-precision nano soldering paste which is composed of liquid solder, scaling powder, auxiliaries and a solvent, the liquid solder is composed of nano copper-antimony alloy, nano tin, silver, acrylic resin and isophorone diluent, the nano copper-antimony alloy and the nano tin serve as main components of the liquid solder, and the nano tin serves as the main components of the liquid solder. The size specification of a welding spot is further reduced after soldering of the soldering paste is completed, the requirement for high-precision welding of existing electronic equipment is met, and the soldering paste has the advantages of being small in solder particle size, high in anti-oxidation degree, long in quality guarantee period and convenient to popularize and implement.

Description

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

[0002] The invention belongs to the technical field of soldering materials, and in particular relates to a high-precision nano solder paste. Background Art

[0003] Solder paste is a new type of welding material that came into being with SMT. It is a paste-like mixture formed by solder powder, flux, etc. It is mainly used for the welding of electronic components such as resistors, capacitors, ICs, etc. on the surface of PCBs in the SMT industry. The existing solder paste can be divided into 3-8 grades according to the particle size of the tin powder. Among them, grade 8 solder paste refers to solder paste prepared using tin powder with a particle size of 2-8μm. As the precision of electronic devices such as mobile phones has been significantly improved, the existing solder paste particle size grades cannot meet the welding needs of precision electronic components due to the limitations of equipment assembly specifications. The existing nano-metal powder has a larger surface area and is more easily oxidized during the welding process. After welding, there is a lot of welding slag and a high defective rate, which is not convenient for the welding of electronic components. Now there is an urgent need for a high-precision nano-solder with higher precision and high oxidation resistance that can meet the iterative welding needs of electronic components. Summary of the invention

[0004] In order to solve the technical problem that the existing solder paste cannot meet the welding requirements of high-precision electronic components, the present invention proposes a high-precision nano solder paste; The second object of the present invention is to provide a method for preparing high-precision nano solder paste.

[0005] In order to achieve the first purpose, this application adopts the following scheme: High-precision nano solder paste is composed of the following components by weight: 75-82 parts of liquid solder, 10-17 parts of flux, 6-8 parts of solvent, and 1-2 parts of additive; 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 soldering flux is composed of the following components by weight: 5-7 parts of a film former, 2-3 parts of an activator, 1-2 parts of a thixotropic agent, 0.5-1 parts of an etching slowing agent, and 0.5-1 parts of a wetting agent.

[0006] Preferably, the solvent is one or a combination of more than one 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.

[0007] Preferably, the auxiliary agent is composed of the following components by weight: 0.5-1 part of stabilizer and 0.5-1 part of dispersant.

[0008] Preferably, the thixotropic agent is one or more of glyceryl tri-12-hydroxystearate, polyamide, and stearamide, the etchant 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 can significantly improve the expansibility of the solder paste after compounding, so that the spread area of ​​the solder paste and the pad is significantly increased.

[0009] Preferably, the activator is a mixture of oxalic acid, citric acid and triethanolamine in a mass ratio of 1:1:2, which has excellent activity and moderate corrosiveness, can efficiently remove oxides on the surface of the pad, and will not corrode the pad during welding.

[0010] Preferably, the method for preparing the nano copper-antimony alloy comprises the following steps: S101. The copper-antimony alloy block is placed in a crucible at 40-60 ° C and preheated and dried for 5-20 min; S102. The dried copper-antimony alloy is placed in an arc plasma evaporator, evacuated to a vacuum degree of 0.03-0.056 MPa using a vacuum pump, and allowed to stand for 10-20 min; S103. A mixture of hydrogen, argon and helium is introduced into an arc plasma evaporator at 0.05-0.08MPa, and the copper-antimony alloy is evaporated at a cathode current of 580-650A to obtain a coarse nano-copper-antimony alloy having a particle size of 190-410nm after cooling; S104. Passivating and modifying the crude nano copper-antimony alloy obtained in step S103 to obtain a nano copper-antimony alloy.

[0011] Preferably, the preparation method of the copper-antimony alloy comprises the following steps: adding 93wt% copper and 7wt% antimony at a mass fraction into a crucible at the same time and smelting them at a 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.

[0012] Preferably, in step S103, the volume ratio of hydrogen, argon and helium is 1-3:5-8:1.

[0013] During actual use, the copper-antimony alloy is placed in an arc plasma evaporator, and the copper-antimony alloy is evaporated into copper-antimony vapor. After a mixture of hydrogen, argon and helium is introduced, the copper-antimony vapor is activated by hydrogen, collides with helium and argon to form nuclei, and settles to form a coarse nano-copper-antimony alloy. Hydrogen, argon and helium are continuously introduced at a pressure of 0.05-0.08 MPa, so that the copper-antimony vapor is fully activated and fully collides with the inert gas to form nuclei, thereby 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 the traditional method for preparing nano-metal particles, the use of an arc plasma evaporation valve can significantly improve the purity of the metal, reduce the contact between the nano-metal particles and oxygen, and reduce the content of metal oxides, so that the particle size of the nano-copper-antimony alloy is 100-568 nm.

[0014] Preferably, the passivation modification in step S104 comprises the following steps: placing the crude nano copper-antimony alloy obtained in step S103 into a magnetic stirrer containing a modifier, and stirring at 40-55° C. and 1200-1800 rpm for 10-20 min.

[0015] 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.

[0016] During actual use, a mixture of BTA, oxalic acid, anhydrous ethanol and polyethylene glycol is used for modification. On the one hand, the nano-copper-antimony alloy is coated with a reducing medium to improve its antioxidant properties in an aerobic environment and extend 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 improved, the alloy is allowed to settle and aggregate into clusters, and the nanoparticle size distribution is destroyed.

[0017] Preferably, the nano-tin preparation method comprises the following steps: putting tin powder, citric acid and ethanol into an ultrasonic ball mill in sequence, ball milling for 20-48 hours at 200-350 rpm, 25-35° C. and ultrasonic vibration, and filtering and drying to obtain the nano-tin.

[0018] 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.

[0019] In actual use, the tin powder pigment is ultrasonically ball-milled to a particle size of 200-500nm. Nano-tin is the main component of solder. The use of ball milling technology can effectively reduce the cost of solder. Tin is highly active, and the activation process with hydrogen is violent, with a high risk factor. In addition, tin has low hardness. The ball milling process is easy to implement and has a high safety factor.

[0020] Preferably, the preparation method of the liquid solder comprises the following steps: placing nano copper antimony alloy, nano tin, silver, acrylic resin and isophorone diluent in a magnetic stirrer in sequence and stirring for 1-2 hours at 500-1400 rpm and 25-30° C.

[0021] During actual use, the nano-copper-antimony alloy, nano-tin and silver are further coated with acrylic resin to further isolate the nano-copper-antimony alloy, nano-tin and silver from oxygen. After the acrylic resin coating, the metal oxide content is further reduced, the wettability and desire extension rate of the solder paste are significantly improved, and the welding effect is significantly improved. Furthermore, after the nano-copper-antimony alloy, nano-tin and silver are coated with acrylic resin, additives and solvents are used. After the welding is completed, the residual substances on the welding plate are highly hydrophilic, and the soldering residues can be removed after soaking in a 78-90% ethanol solution by mass for 3-5 minutes.

[0022] Preferably, the film-forming agent is one or a combination of two or more of hydrogenated rosin, disproportionated rosin, maleated rosin, and polymerized rosin. More preferably, the film-forming agent is a mixture of hydrogenated rosin and polymerized rosin in a mass ratio of 1:1.

[0023] In order to achieve the second purpose, this application adopts the following technical solution: The preparation method of high-precision nano solder paste comprises the following steps: S201. The film-forming agent, activator, thixotropic agent, slow etching agent and wetting agent are sequentially placed in a stirring kettle and stirred at 40-50°C and 300-420rpm for 20-30min to obtain a soldering flux; S202. Put solder, flux, additive and solvent into a vacuum stirring kettle in sequence and stir at 25-35°C and 400-620rpm for 3-7h to obtain high-precision nano solder paste.

[0024] Compared with the prior art, this application has the following beneficial effects: 1. The present application provides a high-precision nano solder paste and a preparation method thereof, which is composed of liquid solder, flux, additives, and solvents, wherein 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 of the solder paste is further reduced, meeting the needs of high-precision soldering of existing electronic equipment. The solder paste has the advantages of small solder particle size, high antioxidant degree, long shelf life, and easy promotion and implementation.

[0025] 2. The present application provides a method for preparing a high-precision nano solder paste, by stirring solder, flux, additives and solvents in a vacuum environment to prepare an environmentally friendly, low-residue, easy-to-clean solder paste, which has the advantages of a wide range of applications, little environmental pollution, simple operation, strong reproducibility and low implementation cost. DETAILED DESCRIPTION

[0026] The present invention is further described below in conjunction with Table 1-2 and specific embodiments 1-3: (1) The method for preparing the copper-antimony alloy comprises the following steps: 93wt% copper and 7wt% antimony are added into a crucible at the same time for high temperature smelting to obtain a liquid copper-antimony alloy. The liquid copper-antimony alloy is poured into a mold and then cooled to room temperature.

[0027] Example 1 The preparation method of nano copper-antimony alloy comprises the following steps: S101. Place the copper-antimony alloy block in a crucible at 42.5°C and preheat and dry for 18 minutes; S102. The dried copper-antimony alloy is placed in an arc plasma evaporator, evacuated to a vacuum degree of 0.037 MPa using a vacuum pump, and allowed to stand for 17 min; S103. A gas 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, and the copper-antimony alloy is evaporated at a cathode current of 625 A, and after cooling, a coarse nano-copper-antimony alloy having an average particle size of 217 nm is obtained; S104. The crude nano copper-antimony alloy obtained in step S103 is placed in 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 at 47° C. and 1325 rpm for 15 min to obtain the nano copper-antimony alloy.

[0028] The method for preparing nano tin comprises the following steps: Tin powder, citric acid and ethanol were sequentially put into an ultrasonic ball mill at a mass ratio of 1:0.5:2, and ball 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 a stainless steel grinding ball with a diameter of 2 mm. The mixture was filtered and dried to obtain nano-tin with an average particle size of 227 nm. According to the weight parts shown in Table 1, the preparation method of liquid solder includes the following steps: Nano copper-antimony alloy, nano tin, silver, acrylic resin and isophorone diluent were sequentially placed into a magnetic stirrer and stirred for 1.2 h at 662 rpm and 27° C.

[0029] According to the weight parts shown in Table 2, the preparation method of high-precision nano solder paste includes the following steps: S201. The film-forming agent, activator, thixotropic agent, slow etching agent and wetting agent are sequentially placed in a stirring tank and stirred at 41.5°C and 381rpm for 25min to obtain a soldering flux; S202. Put the solder, flux, additive and solvent into a vacuum stirring kettle in sequence and stir for 6.2 hours at 26°C, 420 rpm and a vacuum degree of 0.035 MPa to obtain a high-precision nano solder paste.

[0030] Example 2 The preparation method of nano copper-antimony alloy comprises the following steps: S101. Place the copper-antimony alloy block in a crucible at 51.5°C and preheat and dry for 12 minutes; S102. The dried copper-antimony alloy is placed in an arc plasma evaporator, evacuated to a vacuum degree of 0.045 MPa using a vacuum pump, and allowed to stand for 16 min; S103. A mixed gas of hydrogen, argon and helium in a volume ratio of 2:7:1 is introduced into an arc plasma evaporator at 0.06 MPa, and the copper-antimony alloy is evaporated at a cathode current of 611 A, and after cooling, a coarse nano-copper-antimony alloy with a particle size of 320 nm is obtained; S104. The crude nano copper-antimony alloy obtained in step S103 is placed in 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 at 47.5°C and 1477rpm for 16 minutes to obtain the nano copper-antimony alloy.

[0031] The method for preparing nano tin comprises the following steps: Tin powder, citric acid and ethanol were sequentially put into an ultrasonic ball mill at a mass ratio of 1:0.5:2, and ball 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 a stainless steel grinding ball with a diameter of 1.7 mm. The mixture was filtered and dried to obtain nano-tin with an average particle size of 485 nm. According to the weight parts shown in Table 1, the preparation method of liquid solder includes the following steps: Nano copper-antimony alloy, nano tin, silver, acrylic resin and isophorone diluent were sequentially placed into a magnetic stirrer and stirred for 1.5 hours at 856 rpm and 27.2° C. to obtain the mixture.

[0032] According to the weight parts shown in Table 2, the preparation method of high-precision nano solder paste includes the following steps: S201. The film-forming agent, activator, thixotropic agent, slow etching agent and wetting agent are sequentially placed in a stirring kettle and stirred at 45.5°C and 401rpm for 26min to obtain a soldering flux; S202. Put the solder, flux, additive and solvent into a vacuum stirring kettle in sequence and stir for 5.6 hours at 29.5°C, 544rpm and a vacuum degree of 0.035MPa to obtain a high-precision nano solder paste.

[0033] Example 3 The preparation method of nano copper-antimony alloy comprises the following steps: S101. The copper-antimony alloy block was placed in a crucible at 42°C and preheated and dried for 19 minutes; S102. The dried copper-antimony alloy is placed in an arc plasma evaporator, evacuated to a vacuum degree of 0.055 MPa using a vacuum pump, and allowed to stand for 18 min; S103. A gas mixture of hydrogen, argon and helium in a volume ratio of 3:8:1 is introduced into an arc plasma evaporator at 0.05 MPa, and the copper-antimony alloy is evaporated at a cathode current of 589 A, and after cooling, a coarse nano-copper-antimony alloy with a particle size of 215 nm is obtained; S104. The crude nano copper-antimony alloy obtained in step S103 is placed in 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 at 42.5°C and 1288rpm for 20min to obtain the nano copper-antimony alloy.

[0034] The method for preparing nano tin comprises the following steps: Tin powder, citric acid and ethanol were put into an ultrasonic ball mill in sequence, and 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 a stainless steel grinding ball with a diameter of 1.8 mm. The nano-tin with a particle size of 402 nm was obtained by filtration and drying. According to the weight parts shown in Table 1, the preparation method of liquid solder includes the following steps: Nano copper-antimony alloy, nano tin, silver, acrylic resin and isophorone diluent were sequentially placed into a magnetic stirrer and stirred for 1.2 hours at 1100 rpm and 28° C.

[0035] According to the weight parts shown in Table 2, the preparation method of high-precision nano solder paste includes the following steps: S201. The film-forming agent, activator, thixotropic agent, slow etching agent and wetting agent are sequentially placed in a stirring kettle and stirred at 42°C and 411 rpm for 28 min to obtain a soldering flux; S202. Put solder, flux, additive and solvent into a vacuum stirring kettle in sequence and stir for 6.3 hours at 25-35°C, 541rpm and a vacuum degree of 0.035MPa to obtain a high-precision nano solder paste.

[0036] Table 1 Composition by weight of liquid solder of Examples 1-3

[0037] Table 2 Composition of solder paste by weight in Examples 1-3

[0038] 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-6502.4.34.31:1995, 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.

[0039] Table 3 Test results of Examples 1-3

[0040] As shown in Table 3, in actual use, the copper-antimony alloy is placed in an arc plasma evaporator, and the copper-antimony alloy is evaporated into copper-antimony vapor. After the hydrogen, argon and helium mixed gas is introduced, the copper-antimony vapor is activated by hydrogen, collides with helium and argon to form nuclei, and settles to form a coarse nano copper-antimony alloy. The hydrogen, argon and helium mixed gas are continuously introduced, but 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, and continuously protecting the nano copper-antimony alloy from oxidation after the reaction is complete. Compared with the traditional method for preparing nano metal particles, the use of an arc plasma evaporation valve can significantly improve the purity of the metal, reduce the contact between nano metal particles and oxygen, and reduce the content of metal oxides. Nano tin and nano copper-antimony alloy will not oxidize prematurely during welding. The actual performance meets the industry standards and can meet the needs of high-precision electronic equipment and nano-level welding. In actual use, a mixture of BTA, oxalic acid, anhydrous ethanol and polyethylene glycol is used for modification. On the one hand, the nano copper-antimony alloy is coated with a reducing medium to improve the oxidation resistance in an aerobic environment and extend the shelf life of the solder paste. On the other hand, after being coated 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 improved, and the nanoparticle size distribution is destroyed by sedimentation and aggregation. In actual use, nano-tin is the main component of solder. The use of ball milling process can effectively reduce the cost of solder. Tin has high activity, and the activation process with hydrogen is violent, with a high risk factor. In addition, tin has low hardness. The ball milling process is easy to implement and has a high safety factor. During actual use, the nano-copper-antimony alloy, nano-tin and silver are further coated with acrylic resin to further isolate the nano-copper-antimony alloy, nano-tin and silver from oxygen. After the acrylic resin coating, the metal oxide content is further reduced, the wettability and desire extension rate of the solder paste are significantly improved, and the welding effect is significantly improved. Furthermore, after the nano-copper-antimony alloy, nano-tin and silver are coated with acrylic resin, additives and solvents are used. After the welding is completed, the residual substances on the welding plate are highly hydrophilic, and the soldering residues can be removed after soaking in a 78-90% ethanol solution by mass for 3-5 minutes.

[0041] The present application provides a high-precision nano solder paste and a preparation method thereof, which consists of liquid solder, flux, additives, and solvents, wherein the liquid solder consists 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 of the solder paste is further reduced, meeting the needs of high-precision soldering of existing electronic equipment. The solder paste has the advantages of small solder particle size, high oxidation resistance, long shelf life, and easy promotion and implementation.

[0042] 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 in the protection scope of the present invention.

Claims

1. High-precision nano solder paste, characterized in that: The composition is composed of the following components by weight: 75-82 parts of liquid solder, 10-17 parts of flux, 6-8 parts of solvent, and 1-2 parts of auxiliary agent; 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 soldering flux is composed of the following components by weight: 5-7 parts of film former, 2-3 parts of activator, 1-2 parts of thixotropic agent, 0.5-1 parts of slow etching agent, and 0.5-1 parts of wetting agent; The preparation method of the nano copper-antimony alloy comprises the following steps: S101. The copper-antimony alloy block is placed in a crucible at 40-60 ° C and preheated and dried for 5-20 min; S102. The dried copper-antimony alloy is placed in an arc plasma evaporator, evacuated to a vacuum degree of 0.03-0.056 MPa using a vacuum pump, and allowed to stand for 10-20 min; S103. A mixture of hydrogen, argon and helium is introduced into an arc plasma evaporator at 0.05-0.08MPa, and the copper-antimony alloy is evaporated at a cathode current of 580-650A, and a coarse nano-copper-antimony alloy is obtained after cooling; S104. Passivating and modifying the crude nano-copper-antimony alloy obtained in step S103 to obtain a nano-copper-antimony alloy; The passivation modification in step S104 includes the following steps: The crude nano copper-antimony alloy obtained in step S103 is placed in a magnetic stirrer containing a modifier, and stirred at 40-55° C. and 1200-1800 rpm for 10-20 minutes; 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 nano-tin preparation method comprises the following steps: putting tin powder, citric acid and ethanol into an ultrasonic ball mill in sequence, ball milling for 20-48 hours at 200-350 rpm, 25-35° C. and ultrasonic vibration, and filtering and drying to obtain the nano-tin; The grinding balls of the ultrasonic ball mill are stainless steel grinding balls with a diameter of 1.5-2 mm.

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 comprises the following steps: placing nano copper-antimony alloy, nano tin, silver, acrylic resin and isophorone diluent into a magnetic stirrer in sequence and stirring for 1-2 hours at 500-1400 rpm and 25-30° C. to obtain the liquid solder.

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

6. The high-precision nano solder paste according to claim 1, characterized in that: The particle size of the nano tin is 200-500nm.

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