High-performance lead-free solder paste and preparation method and application thereof

Abstract

The invention belongs to the technical field of lead-free solder paste, and particularly relates to high-performance lead-free solder paste and a preparation method and application thereof. The high-performance lead-free solder paste comprises lead-free alloy powder, a carbon nano tube compound and scaling powder according to the mass ratio of (12-15): (0.5-1): (84.5-87). The carbon nanotube compound comprises a carbon nanotube, a carbon nanohorn, nano indium tin oxide, a quaternary ammonium salt surfactant and liquid rosin; the scaling powder comprises the following raw materials in percentage by mass: 30-40% of hydrogenated rosin, 5-10% of an activating agent, 4-8% of a thixotropic agent, 1-5% of a stabilizing agent and the balance of a solvent, totaling 100%. The high-performance lead-free solder paste provided by the invention is low in voidage of welding spots, high in shear strength and good in temperature cycle impact resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of lead-free solder paste, and in particular relates to a high-performance lead-free solder paste and a preparation method and application thereof. Background Art

[0002] At present, the solder paste industry is developing in the direction of lead-free, non-toxic and environmentally friendly. Lead-free solder paste is gradually becoming the mainstream of the market due to its low toxicity, low pollution and compliance with environmental protection requirements. With the development trend of miniaturization and high containerization of electronic products, the performance requirements of lead-free solder paste are getting higher and higher. However, compared with lead solder paste, traditional lead-free solder paste is prone to void defects during the welding process, which will lead to a decrease in the mechanical strength of the solder joint and a shortened thermal fatigue life, which seriously threatens the long-term stability of high-reliability electronic equipment (such as aerospace, automotive electronics, and medical equipment).

[0003] The Chinese patent with the authorization publication number CN 118720518 B discloses a lead-free solder paste with low void rate and its preparation method, which is prepared from the following raw materials in parts by weight: 70-90 parts of tin, 1-2 parts of silver, 3-6 parts of copper, 2-5 parts of magnesium fluorosilicate, 3-6 parts of nano carbon powder, 4-5 parts of rare earth oxide and 20-30 parts of flux. The above formula can reduce the void rate in the welding process, improve the wettability of the lead-free solder paste, and improve the quality and reliability of the welding point. However, the void rate of this technical solution is 5.4-15.6%, which cannot meet the requirement of aerospace void rate ≤5%.

[0004] The Chinese patent with publication number CN 118162799 A discloses a formic acid lead-free solder paste and its application. The formic acid lead-free solder paste comprises, by mass percentage, 7-20wt% of flux and 80-93wt% of lead-free alloy powder. The lead-free alloy powder is

[0005] Any one of Sn96.5Ag3Cu0.5, Sn99Ag0.3Cu0.7, Sn89.5Sb10Ni0.5, Sn90Sb10, Sn95Sb5. The formic acid lead-free solder paste of this technical solution uses lead-free alloy powder, which is safe and environmentally friendly; it can be used for automatic printing and dispensing, and reflow through formic acid reducing atmosphere, meeting the ultra-low void rate welding and zero residue requirements of IGBT and automotive-grade power devices, and can completely replace the existing cleaning solder paste and solder sheet process, completely achieving high reliability without cleaning, and greatly reducing costs in process links and materials. However, formic acid lead-free solder paste requires specific formic acid reflow, and the operation is relatively complex: parameters such as temperature, time and solder ratio need to be precisely controlled, the operation requirements are high, and the skills of the operator are required to be high. Summary of the invention

[0006] Based on the defects of the prior art, the purpose of the present invention is to provide a high-performance lead-free solder paste and a preparation method and application thereof. The high-performance lead-free solder paste provided by the present invention has low solder joint void rate, high shear strength and good temperature cycle impact resistance.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0008] The first aspect of the present invention provides a high-performance lead-free solder paste, comprising a lead-free alloy powder, a carbon nanotube composite and a soldering flux in a mass ratio of 12-15:0.5-1:84.5-87;

[0009] The carbon nanotube composite comprises carbon nanotubes, carbon nanohorns, nano indium tin oxide, quaternary ammonium salt surfactant, and liquid rosin;

[0010] The soldering flux comprises, by mass percentage, 30-40% of hydrogenated rosin, 5-10% of activator, 4-8% of thixotropic agent, 1-5% of stabilizer, and the rest of solvent is supplemented to 100%.

[0011] As some preferred solutions, the lead-free alloy powder is selected from

[0012] At least one of SnBi, SnBiAg, SnBiCu, SnBiIn, and SnBiZn.

[0013] As some preferred solutions, the particle size model of the lead-free alloy powder is at least one of 3# (diameter: 25-45μm), 4# (diameter: 20-38μm), 5# (diameter: 15-25μm), and 6# (diameter: 5-15μm).

[0014] In a preferred embodiment, the lead-free alloy powder is SnBi58, particle size model 5#, purchased from Yunnan Tin Industry Tin Materials Co., Ltd.

[0015] In a preferred embodiment, the carbon nanotubes are single-walled carbon nanotubes.

[0016] In a preferred embodiment, the single-walled carbon nanotube has a diameter of 1-2 nm and a length of 5-30 μm, and is purchased from Beijing Dekedaojin Technology Co., Ltd., model: CNT100.

[0017] In a preferred embodiment, the carbon nanohorns have a diameter of 2-5 nm and a length of 10-20 nm, and are purchased from Beijing Dekedaojin Technology Co., Ltd.

[0018] As some preferred solutions, the nano indium tin oxide contains 90-95wt% indium oxide and 5-10wt% tin oxide.

[0019] As some preferred solutions, the particle size of the nano-indium tin oxide is 20-50nm.

[0020] In a preferred embodiment, the nano indium tin oxide contains 90wt% indium oxide and 10wt% tin oxide, has a particle size of 20-30nm, and is purchased from Beijing Dekedaojin Technology Co., Ltd.

[0021] As some preferred solutions, the quaternary ammonium salt surfactant is selected from at least one of rosin-based monoquaternary ammonium salt, rosin-based diquaternary ammonium salt and rosin-based triquaternary ammonium salt.

[0022] In a preferred embodiment, the quaternary ammonium salt surfactant is a rosin-based diquaternary ammonium salt purchased from Henan Daochun New Material Technology Co., Ltd.

[0023] As some preferred solutions, the liquid rosin is selected from at least one of hydrogenated rosin methyl ester, hydrogenated rosin diglycol ester and hydrogenated rosin triglycol.

[0024] In a preferred embodiment, the liquid rosin is hydrogenated rosin methyl ester, purchased from Guangxi Wuzhou Richeng Forest Products Chemical Co., Ltd., model: M-HDR.

[0025] As some preferred solutions, the method for preparing the carbon nanotube composite comprises the following steps:

[0026] (1) Evenly mix nano indium tin oxide, quaternary ammonium salt surfactant and water, stir, filter and dry to obtain a first intermediate product; (2) Evenly mix the first intermediate product, carbon nanotubes, carbon nanohorns and water, let stand, filter and dry to obtain a second intermediate product; (3) Stir the second intermediate product and liquid rosin to obtain a carbon nanotube composite.

[0027] As some preferred solutions, the mass ratio of the nano indium tin oxide, the quaternary ammonium salt surfactant and water is 8-10:1:30-50.

[0028] As some preferred solutions, the mass ratio of the first intermediate product, carbon nanotubes, carbon nanohorns and water is 1:3-5:0.01-0.03:15-25.

[0029] As some preferred solutions, the mass ratio of the second intermediate product to liquid rosin is 1:8-10.

[0030] As some preferred solutions, the stirring speed in step (1) is 4000-6000 rpm, and the stirring time is 20-30 min.

[0031] As some preferred solutions, the standing time in step (2) is 20-40 minutes.

[0032] As some preferred solutions, the stirring speed in step (3) is 1000-2000 rpm, and the stirring time is 10-20 min.

[0033] The carbon nanotube composite of the present invention can significantly reduce the void rate of solder joints, improve the shear strength of solder joints, and also has excellent temperature cycle impact resistance, especially the presence of carbon nanohorns and nano indium tin oxide: the nanoscale pore structure of the carbon nanohorns can be used as a microchannel for the flow of liquid solder, accelerate the diffusion and filling of molten metal, reduce the voids formed due to the obstruction of gas escape, and form a composite structure with the carbon nanotubes, thereby reducing the void rate of solder joints and improving the shear strength of solder joints; the nano indium tin oxide is uniformly dispersed on the solder interface to form a continuous intermetallic compound layer, inhibiting the aggregation of bubbles while achieving alloy grain refinement through the heterogeneous nucleation effect, reducing the size and segregation tendency of the interface brittle phase; the carbon nanotubes, carbon nanohorns and nano indium tin oxide work together to obtain a lead-free solder paste with low void rate, high shear strength and good temperature cycle impact resistance.

[0034] In the process of preparing carbon nanotube composites, quaternary ammonium salt surfactants are used to modify nano-indium tin oxide to obtain positively charged nano-indium tin oxide, which is then combined with negatively charged carbon nanotubes and carbon nanohorns through electrostatic adsorption. It is unexpectedly found that when using traditional alkyl quaternary ammonium salts, the void rate of the solder joints is large, the shear strength of the solder joints is low, and the temperature cycle impact resistance is poor; when using rosin-based quaternary ammonium salt surfactants, the rosin-based quaternary ammonium salt molecules contain rosin derivatives, and their benzene ring structure forms a π-π conjugation with liquid rosin, which significantly improves the compatibility of the composite with the flux, thereby reducing the void rate of the solder joints and improving the shear strength and temperature cycle impact resistance of the solder joints.

[0035] As some preferred solutions, the hydrogenated rosin has a tetrahydroresin acid content of ≥30%, a abietic acid content of ≤1%, and a dehydroabietic acid content of ≤8%.

[0036] In a preferred embodiment, the hydrogenated rosin has a tetrahydroresin acid content of ≥30%, a abietic acid content of ≤0.5%, and a dehydroabietic acid content of ≤8%, and is purchased from Guangxi Wuzhou Richeng Forest Products Chemical Co., Ltd., model: Special Grade X.

[0037] In the art, although the prior art discloses a variety of rosin types and models, in the actual selection process, no technical indicators for rosin selection are given. The inventors unexpectedly discovered that in the present invention, when hydrogenated rosin with a tetrahydroresin acid content of ≥30%, abietic acid content of ≤1%, and a dehydroabietic acid content of ≤8% is selected, under the action of the carbon nanotube composite, the void rate of the solder joint can be less than 5%, the shear strength of the solder joint can be greater than 35 MPa, and the solder joint has no cracking phenomenon after 1000 cycles of the temperature cycle impact test, and the shear strength is still greater than 31 MPa; when the indicators of rosin or hydrogenated rosin are not within the above range, the performance of the obtained lead-free solder paste is poor.

[0038] As some preferred solutions, the activator includes an organic acid and cyclohexylamine hydrochloride in a mass ratio of 5-8:1.

[0039] As some preferred embodiments, the organic acid is selected from at least one of glutaric acid, adipic acid, azelaic acid and glycolic acid.

[0040] As some preferred solutions, the organic acid is glutaric acid and phenylsuccinic acid in a mass ratio of 3-6:1-2.

[0041] In a preferred embodiment, the organic acid is glutaric acid and phenylsuccinic acid in a mass ratio of 4:2.

[0042] As some preferred solutions, the thixotropic agent is selected from at least one of castor oil, polyamide wax, microcrystalline wax and beeswax.

[0043] In a preferred embodiment, the thixotropic agent is castor oil.

[0044] As some preferred solutions, the castor oil is selected from at least one of hydrogenated castor oil, methyl hydrogenated castor oil and polyamide-modified hydrogenated castor oil.

[0045] In a preferred embodiment, the castor oil is polyamide-modified hydrogenated castor oil purchased from Shenzhen Jintenglong Industrial Co., Ltd., model: CRAYVALLAC SF.

[0046] As some preferred solutions, the stabilizer is at least one selected from 2,6-di-tert-butyl-4-methylphenol, dilauryl thiodipropionate, butylated hydroxyanisole and butylated hydroxytoluene.

[0047] In a preferred embodiment, the stabilizer is butylated hydroxyanisole.

[0048] As some preferred solutions, the solvent is selected from at least one of triethylene glycol, tripropylene glycol, butylene glycol, 2-ethyl-1,3-hexanediol, 2-hexyl-1-decanol, diethylene glycol hexyl ether, diethylene glycol butyl ether, diethylene glycol ethyl ether and tripropylene glycol butyl ether.

[0049] As some preferred solutions, the solvent includes tripropylene glycol and diethylene glycol hexyl ether in a mass ratio of 1:2-4.

[0050] In a preferred embodiment, the solvent comprises tripropylene glycol and diethylene glycol hexyl ether in a mass ratio of 1:3.

[0051] The second aspect of the present invention provides a method for preparing the above-mentioned high-performance lead-free solder paste, comprising the following steps: uniformly mixing hydrogenated rosin, an activator, a thixotropic agent, a stabilizer and a solvent to obtain a flux, and uniformly mixing the flux, a lead-free alloy powder and a carbon nanotube composite to obtain a high-performance lead-free solder paste.

[0052] A third aspect of the present invention provides the use of the high-performance lead-free solder paste in the welding of electronic components.

[0053] Compared with the prior art, the present invention has the following beneficial effects:

[0054] The present invention uses a quaternary ammonium salt surfactant to form a carbon nanotube composite from carbon nanotubes, carbon nanohorns and nano indium tin oxide. The three work together to obtain a lead-free solder paste with low solder joint void rate, high shear strength and good temperature cycle impact resistance. At the same time, a specific hydrogenated rosin is used. Under the action of the carbon nanotube composite, the high-performance lead-free solder paste has a solder joint void rate of less than 5%, a solder joint shear strength of greater than 35MPa, no solder joint cracking after 1000 cycles of a temperature cycle impact test, and a shear strength still greater than 31MPa. DETAILED DESCRIPTION

[0055] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, a specific implementation scheme is now described in detail.

[0056] The present invention is further described below in conjunction with the examples, but the present invention is not limited to the following examples. The implementation conditions used in the examples can be further adjusted according to the different requirements of specific use, and the implementation conditions not specified are conventional conditions in the industry. The technical features involved in each embodiment of the present invention can be combined with each other as long as they do not conflict with each other.

[0057] In the following examples and comparative examples, unless otherwise specified, all raw materials used were commercially available or prepared by conventional methods in the art.

[0058] Example 1

[0059] A high-performance lead-free solder paste consisting of lead-free alloy powder, carbon nanotube composite and flux in a mass ratio of 12:1:87.

[0060] The lead-free alloy powder is SnBi58, with a particle size of 5#, purchased from Yunnan Tin Industry Tin Materials Co., Ltd.

[0061] The carbon nanotube composite consists of carbon nanotubes, carbon nanohorns, nano indium tin oxide, quaternary ammonium salt surfactant and liquid rosin.

[0062] The carbon nanotubes are single-walled carbon nanotubes with a diameter of 1-2 nm and a length of 5-30 μm. They are purchased from Beijing Dekedaojin Technology Co., Ltd., model: CNT100.

[0063] The carbon nanohorns have a diameter of 2-5 nm and a length of 10-20 nm, and are purchased from Beijing Dekedaojin Technology Co., Ltd.

[0064] The nano indium tin oxide contains 90 wt% indium oxide and 10 wt% tin oxide, has a particle size of 20-30 nm, and is purchased from Beijing Dekedaojin Technology Co., Ltd.

[0065] The quaternary ammonium salt surfactant is a rosin-based diquaternary ammonium salt, which was purchased from Henan Daochun New Material Technology Co., Ltd.

[0066] The liquid rosin is hydrogenated rosin methyl ester, purchased from Guangxi Wuzhou Richeng Forest Products Chemical Co., Ltd., model: M-HDR.

[0067] The preparation method of the carbon nanotube composite is as follows: (1) uniformly mixing nano indium tin oxide, a quaternary ammonium salt surfactant and water, stirring, filtering and drying to obtain a first intermediate product; (2) uniformly mixing the first intermediate product, carbon nanotubes, carbon nanohorns and water, standing, filtering and drying to obtain a second intermediate product; and (3) mixing the second intermediate product and liquid rosin and stirring to obtain a carbon nanotube composite.

[0068] The mass ratio of the nano indium tin oxide, the quaternary ammonium salt surfactant and water is 9:1:40.

[0069] The mass ratio of the first intermediate product, carbon nanotubes, carbon nanohorns and water is 1:4:0.02:20.

[0070] The mass ratio of the second intermediate product to the liquid rosin is 1:9.

[0071] The stirring speed in step (1) is 5000 rpm and the stirring time is 30 min.

[0072] The standing time in step (2) is 30 minutes.

[0073] The stirring speed in step (3) is 2000 rpm, and the stirring time is 20 min.

[0074] The soldering flux is composed of the following raw materials by mass percentage: 30% hydrogenated rosin, 5% activator, 4% thixotropic agent, 2% stabilizer, and the rest of the solvent is supplemented to 100%.

[0075] The hydrogenated rosin has a tetrahydroresin acid content of ≥30%, abietic acid content of ≤0.5%, and a dehydroabietic acid content of ≤8%, and is purchased from Guangxi Wuzhou Richeng Forest Products and Chemical Co., Ltd., model: special grade X.

[0076] The activator comprises an organic acid and cyclohexylamine hydrochloride (CAS: 4998-76-9) in a mass ratio of 6:1.

[0077] The organic acid is glutaric acid (CAS: 110-94-1) and phenylsuccinic acid (CAS: 635-51-8) in a mass ratio of 4:2.

[0078] The thixotropic agent is polyamide-modified hydrogenated castor oil, which was purchased from Shenzhen Jintenglong Industrial Co., Ltd., model: CRAYVALLAC SF.

[0079] The stabilizer is butylated hydroxyanisole (CAS: 25013-16-5).

[0080] The solvent includes tripropylene glycol (CAS: 24800-44-0) and diethylene glycol hexyl ether (CAS: 112-59-4) in a mass ratio of 1:3.

[0081] The preparation method of the high-performance lead-free solder paste is as follows: hydrogenated rosin, activator, thixotropic agent, stabilizer and solvent are mixed evenly to obtain flux, and the flux, lead-free alloy powder and carbon nanotube composite are mixed evenly to obtain high-performance lead-free solder paste.

[0082] Example 2

[0083] The only difference from Example 1 is that the high-performance lead-free solder paste is composed of lead-free alloy powder, carbon nanotube composite and flux in a mass ratio of 13:0.8:86.2; the rest are the same.

[0084] The preparation method of the high performance lead-free solder paste is the same as that of Example 1.

[0085] Example 3

[0086] The only difference from Example 1 is that the high-performance lead-free solder paste is composed of lead-free alloy powder, carbon nanotube composite and flux in a mass ratio of 15:0.5:84.5; the rest are the same.

[0087] The preparation method of the high performance lead-free solder paste is the same as that of Example 1.

[0088] Example 4

[0089] The only difference from Example 1 is that the soldering flux, by mass percentage, has the following raw material composition: 35% hydrogenated rosin, 8% activator, 6% thixotropic agent, 3% stabilizer, and the solvent is added to make up the balance to 100%; the rest are the same.

[0090] The preparation method of the high performance lead-free solder paste is the same as that of Example 1.

[0091] Example 5

[0092] The only difference from Example 1 is that the soldering flux, by mass percentage, comprises the following raw materials: 40% hydrogenated rosin, 10% activator, 8% thixotropic agent, 5% stabilizer, and the solvent is added to make up the balance to 100%; the rest are the same.

[0093] The preparation method of the high performance lead-free solder paste is the same as that of Example 1.

[0094] Comparative Example 1

[0095] The only difference from Example 1 is that there are no carbon nanohorns. The preparation method of the carbon nanotube composite is: (1) nano indium tin oxide, quaternary ammonium salt surfactant and water are mixed evenly, stirred, filtered and dried to obtain a first intermediate product; (2) the first intermediate product, carbon nanotubes, carbon and water are mixed evenly, allowed to stand, filtered and dried to obtain a second intermediate product; (3) the second intermediate product and liquid rosin are stirred to obtain a carbon nanotube composite; the mass ratio of the first intermediate product, carbon nanotubes and water is 1:4:20; the rest are the same.

[0096] The preparation method of the high performance lead-free solder paste is the same as that of Example 1.

[0097] Comparative Example 2

[0098] The only difference from Example 1 is that nano indium tin oxide is replaced by nano cerium oxide of equal mass with an average particle size of 20 nm purchased from Beijing Dekedaojin Technology Co., Ltd.; the preparation method of the carbon nanotube composite is as follows: (1) nano cerium oxide, quaternary ammonium salt surfactant and water are mixed evenly, stirred, filtered and dried to obtain a first intermediate product; (2) the first intermediate product, carbon nanotubes, carbon nanohorns and water are mixed evenly, allowed to stand, filtered and dried to obtain a second intermediate product; (3) the second intermediate product and liquid rosin are stirred to obtain a carbon nanotube composite; the mass ratio of nano cerium oxide, quaternary ammonium salt surfactant and water is 9:1:40; the rest are the same.

[0099] The preparation method of the high performance lead-free solder paste is the same as that of Example 1.

[0100] Comparative Example 3

[0101] The only difference from Example 1 is that the rosin-based diquaternary ammonium salt is replaced by dodecyltrimethylammonium chloride (CAS No.: 112-00-5) of the same mass; the rest are the same.

[0102] The preparation method of the high performance lead-free solder paste is the same as that of Example 1.

[0103] Comparative Example 4

[0104] The only difference from Example 1 is that the hydrogenated rosin has tetrahydroresin acid ≥30%, abietic acid ≤1%, and dehydroabietic acid ≤10%, and is purchased from Guangxi Wuzhou Richeng Forest Products Chemical Co., Ltd., model: Grade 1 WW; the rest are the same.

[0105] The preparation method of the high performance lead-free solder paste is the same as that of Example 1.

[0106] Comparative Example 5

[0107] The only difference from Example 1 is that the hydrogenated rosin has tetrahydroabietic acid ≤30%, abietic acid ≤2%, and dehydroabietic acid ≤10%, and is purchased from Guangxi Dinghong Resin Co., Ltd., model: DH-HR; the rest are the same.

[0108] The preparation method of the high performance lead-free solder paste is the same as that of Example 1.

[0109] Comparative Example 6

[0110] The only difference from Example 1 is that the hydrogenated rosin is replaced by KE604 rosin from Arakawa, Japan; the rest is the same.

[0111] The preparation method of the high performance lead-free solder paste is the same as that of Example 1.

[0112] In order to verify the performance of the high-performance lead-free solder paste of the present invention, the lead-free solder paste prepared in Examples 1-5 and Comparative Examples 1-6 was subjected to the following performance tests:

[0113] (1) Void rate test: The pads are copper-plated nickel and gold pads, the nickel layer thickness is 6 mm, the gold layer thickness is 0.02 mm, the reflow temperature is 180°C, the reflow time is 90 seconds, and a solder joint with a diameter of 0.8 mm is formed. The void rate of the solder joint is detected using X-ray detection equipment;

[0114] (2) Shear strength: The pads are copper-plated nickel and gold pads. The nickel layer thickness is 6 mm and the gold layer thickness is 0.02 mm. The reflow temperature is 180°C and the reflow time is 90 s. A solder joint with a diameter of 0.8 mm is formed. The shear strength test of the solder joint is performed at a shear speed of 50 mm / min.

[0115] (3) Temperature cycle shock test: The pad is a copper-plated nickel and gold pad, the nickel layer thickness is 6 mm, the gold layer thickness is 0.02 mm, the reflow temperature is 180 ° C, the reflow time is 90 s, and a solder joint with a diameter of 0.8 mm is formed. The pad is subjected to a temperature cycle shock test. The temperature cycle shock test is as follows:

[0116] -40℃×10min, 125℃×10min is one cycle. After 1000 cycles, observe whether the solder joint has cracking phenomenon and test the shear strength of the solder joint. The shear speed is 50mm / min.

[0117] Table 1

[0118]

[0119]

[0120] It can be seen from Table 1 that the void rate of the solder joints of the lead-free solder pastes of Examples 1 to 5 is less than 5%, the shear strength is greater than 35 MPa, the solder joints do not crack after the temperature cycle impact test, and the shear strength is greater than 30 MPa; in Comparative Example 1, there is no carbon nanohorn, the void rate of the solder joints of the obtained lead-free solder paste is greater than 5%, the shear strength is less than 30 MPa, the solder joints crack after the temperature cycle impact test, and the shear strength is less than 25 MPa; in Comparative Example 2, nano-indium tin oxide is replaced with nano-cerium oxide of equal mass, the void rate of the solder joints of the obtained lead-free solder paste is greater than 5%, the shear strength is less than 35 MPa, the solder joints do not crack after the temperature cycle impact test, and the shear strength is less than 30 MPa; in Comparative Example 3, rosin-based diquaternary ammonium salt is replaced with dodecyltrimethylammonium chloride of equal mass, the void rate of the solder joints of the obtained lead-free solder paste is greater than 5%, The shear strength is less than 30MPa, the solder joints crack after the temperature cycle impact test, and the shear strength is less than 25MPa; the contents of tetrahydroresin acid, abietic acid and dehydroabietic acid in the hydrogenated rosin of Comparative Examples 4-5 change, wherein the voiding rate of the solder joints of the lead-free solder paste obtained in Comparative Example 4 is greater than 5%, the shear strength is less than 35MPa, the solder joints do not crack after the temperature cycle impact test, and the shear strength is less than 30MPa; the voiding rate of the solder joints of the lead-free solder paste obtained in Comparative Example 5 is greater than 5%, the shear strength is less than 30MPa, the solder joints crack after the temperature cycle impact test, and the shear strength is less than 25MPa; Comparative Example 6 replaces hydrogenated rosin with rosin, and the voiding rate of the solder joints of the lead-free solder paste obtained is greater than 5%, the shear strength is less than 30MPa, the solder joints do not crack after the temperature cycle impact test, and the shear strength is less than 25MPa.

[0121] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions of the technical solution of the present invention by ordinary technicians in this field do not deviate from the essence and scope of the technical solution of the present invention.

Claims

1. A high performance lead-free solder paste, characterized in that: Includes a mass ratio of 12-15: 0.5-1: 84.5-87 lead-free alloy powder, carbon nanotube composite and flux; The carbon nanotube composite comprises carbon nanotubes, carbon nanohorns, nano indium tin oxide, quaternary ammonium salt surfactant, and liquid rosin; The soldering flux comprises, by mass percentage, 30-40% of hydrogenated rosin, 5-10% of activator, 4-8% of thixotropic agent, 1-5% of stabilizer, and the rest of solvent is supplemented to 100%.

2. The high performance lead-free solder paste according to claim 1, characterized in that: The carbon nanotubes are single-walled carbon nanotubes; the diameter of the single-walled carbon nanotubes is 1-2 nm and the length is 5-30 μm.

3. The high performance lead-free solder paste according to claim 2, characterized in that: The diameter of the carbon nanohorn is 2-5 nm, and the length is 10-20 nm.

4. The high performance lead-free solder paste according to claim 3, characterized in that: The nano indium tin oxide contains 90-95wt% of indium oxide and 5-10wt% of tin oxide.

5. The high performance lead-free solder paste according to claim 5, characterized in that: The quaternary ammonium salt surfactant is selected from at least one of rosin-based monoquaternary ammonium salt, rosin-based diquaternary ammonium salt and rosin-based triquaternary ammonium salt.

6. The high performance lead-free solder paste according to any one of claim 5, characterized in that: The liquid rosin is selected from at least one of hydrogenated rosin methyl ester, hydrogenated rosin diglycol ester and hydrogenated rosin triglycol.

7. The high performance lead-free solder paste according to any one of claims 1 to 6, characterized in that: The preparation method of the carbon nanotube composite comprises the following steps: (1) uniformly mixing nano indium tin oxide, a quaternary ammonium salt surfactant and water, stirring, filtering and drying to obtain a first intermediate product; (2) uniformly mixing the first intermediate product, carbon nanotubes, carbon nanohorns and water, standing, filtering and drying to obtain a second intermediate product; and (3) mixing the second intermediate product and liquid rosin and stirring to obtain a carbon nanotube composite.

8. The high performance lead-free solder paste according to claim 1, characterized in that: The content of tetrahydroresin acid in the hydrogenated rosin is ≥30%, the content of abietic acid is ≤1%, and the content of dehydroabietic acid is ≤8%.

9. The method for preparing a high performance lead-free solder paste according to any one of claims 1 to 8, characterized in that: The following steps are involved: The hydrogenated rosin, activator, thixotropic agent, stabilizer and solvent are uniformly mixed to obtain solder flux, and the solder flux, lead-free alloy powder and carbon nanotube composite are uniformly mixed to obtain high-performance lead-free solder paste.

10. Use of the high performance lead-free solder paste according to any one of claims 1 to 8 in soldering of electronic components.

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