A high-reliability tin-silver-copper alloy, its preparation method and application

Abstract

The present invention relates to a high-reliability tin-silver-copper-based alloy, its preparation method and application. The alloy comprises the following raw materials for preparation by weight percentage: 5-10% of Sn-In-Nd-graphene hybrid material, 5-10% of Cu-Ag core-shell particles, and the balance is Sn-Ag-Sb-Ni alloy; wherein, the Sn-In-Nd-graphene hybrid material comprises the following components by weight percentage: 3-5% of In, 0.5-1% of Nd, and 3-5% of graphene, and the balance is Sn and inevitable impurities; the Sn-Ag-Sb-Ni alloy comprises the following components by weight percentage: 4-7% of Ag, 0.1-0.5% of Sb, and 0.1-0.5% of Ni, and the balance is Sn and inevitable impurities. The alloy of the present invention simultaneously meets the requirements of automotive electronics for high temperature resistance, anti-vibration and long life, and becomes an ideal material for high-performance electronic packaging.

Description

Technical Field

[0001] The present invention relates to the technical field of tin-silver-copper alloys, and specifically relates to a high-reliability tin-silver-copper alloy and its preparation method and application. Background Art

[0002] Traditional tin-lead solders have occupied a wide range of applications in the electronics industry due to their excellent solderability, ductility, electrical conductivity, and corrosion resistance. However, the highly toxic and highly accumulative nature of lead poses a serious threat to the ecological environment and human health. Since the 1990s, a global wave of lead-free substitution has emerged, turning to seek alternatives to tin-lead solders. At present, although lead-free systems such as pure Sn-Ag, Sn-Cu, Sn-Zn, and Sn-Ag-Cu have received extensive attention, they have not been able to completely replace tin-lead solders. The main challenges faced by current lead-free solders are their relatively high melting points and poor mechanical properties.

[0003] The modification strategies of lead-free solders mainly focus on two directions: alloying and the addition of a second phase. Although alloying can improve the solder properties to a certain extent, the effect is limited; while the addition of second-phase particles can not only refine the microstructure but also significantly improve the mechanical properties and wettability of the solder through the dispersion strengthening mechanism. Second-phase particles can be roughly divided into two categories: active particles (such as metal particles like Co, Ni, Cu, Al, etc.) and inactive particles (such as ceramic particles like Al2O3, ZrO2, etc., and carbon materials like graphene, carbon nanotubes, etc.). Active particles can react chemically with the matrix to form good bonding, but they may undergo interdiffusion, dissolution, or coarsening during long-term service, thereby affecting the stability of the solder properties. In contrast, inactive particles, with their high strength and good stability, effectively hinder grain growth and dislocation movement, but have relatively weak bonding with the matrix. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a high-reliability tin-silver-copper alloy and its preparation method and application.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] In the first aspect, the present invention provides a high-reliability tin-silver-copper alloy, comprising the following raw materials for preparation by weight percentage: 5-10% of Sn-In-Nd-graphene mixed material, 5-10% of Cu-Ag core-shell particles, and the balance being Sn-Ag-Sb-Ni alloy;

[0007] Among them, the Sn-In-Nd-graphene mixed material comprises the following components by weight percentage: 3-4% of In, 0.5-1% of Nd, and 3-5% of graphene, and the balance being Sn and inevitable impurities;

[0008] The Sn-Ag-Sb-Ni alloy comprises the following components by weight percentage: Ag 4-7%, Sb 0.1-0.5%, and Ni 0.1-0.5%, with the balance being Sn and inevitable impurities;

[0009] The preparation method of the Sn-In-Nd-graphene hybrid material comprises the following steps:

[0010] (1) Ultrasonically disperse graphene in absolute ethanol to obtain a graphene slurry;

[0011] (2) Ultrasonically disperse Sn powder, In powder, and Nd powder in absolute ethanol to obtain an alloy slurry;

[0012] (3) Mix the graphene slurry and the alloy slurry and then perform ball milling and vacuum drying to obtain a Sn-In-Nd-graphene precursor powder;

[0013] (4) First, melt the Sn-In-Nd-graphene precursor powder at 600-700 °C for 2-3 h, then raise the temperature to 1500-1700 °C and continue melting for 1-2 h, and keep it warm for 5-10 min to obtain the Sn-In-Nd-graphene hybrid material.

[0014] The alloy matrix of the present invention is the Sn-Ag-Sb-Ni alloy. Sn forms the Ag3Sn strengthening phase with Ag, which can be distributed at the grain boundaries of the Sn matrix, hinder grain sliding, and improve the high-temperature fatigue resistance; Sb acts as a grain refiner to inhibit the dendritic growth of the Sn matrix. At the same time, Sb is dissolved in the Sn matrix (SbSn phase) to enhance the tensile strength; Ni forms a Ni3Sn4 passivation film on the surface of the alloy, significantly enhancing the corrosion resistance of the alloy in sulfur- and chlorine-containing environments. Therefore, the Sn-Ag-Sb-Ni alloy as the matrix can provide good comprehensive properties (such as strength, conductivity, corrosion resistance, etc.), providing a basis for the high reliability of the entire alloy.

[0015] In the present invention, the main body Sn of the Sn-In-Nd-graphene hybrid material and the Sn in the alloy matrix belong to the same source components. Therefore, the hybrid material can reduce the interfacial energy in the Sn-based alloy matrix, improve the uniform distribution of the material, and enhance the bonding property. The graphene therein, as a two-dimensional nano-reinforcement, forms a three-dimensional network structure through ball milling and dispersion, which can significantly improve the strength and toughness of the alloy. The addition of In can reduce the melting point of the alloy and improve the wettability, making it easier to form a dense structure during welding or melting, and reducing the porosity. As a rare earth element, Nd has a strong antioxidant property due to its 4f electron layer structure. It forms a dense Nd2O3 protective film at high temperatures. At the same time, Nd can purify the grain boundaries, reduce the segregation of impurities, and enhance the high-temperature stability of the alloy. The Sn-In-Nd-graphene hybrid material, as the second-phase particles, is uniformly distributed in the Sn-Ag-Sb-Ni alloy matrix, which can effectively improve the alloy's resistance to plastic deformation, inhibit grain coarsening at high temperatures, and enhance the dimensional stability.

[0016] The Cu-Ag core-shell particles of the present invention have Ag as the shell and Cu as the core. Ag forms a dense Ag2O film (melting point 430 °C) in the air, isolating oxygen from contacting the Cu core and avoiding the high-temperature oxidation of Cu. The shell layer Ag can inhibit the excessive diffusion of the Sn matrix to Cu and avoid the excessive formation of brittle intermetallic compounds (such as Cu6Sn5). At the same time, the Ag shell layer in the Cu-Ag core-shell particles serves as a "transition layer" to relieve the difference in thermal expansion coefficients between the Cu core and the Sn matrix and reduce the interfacial stress in the thermal cycle.

[0017] In summary, the Sn-Ag-Sb-Ni alloy, the Sn-In-Nd-graphene hybrid material, and the Cu-Ag core-shell particles all have good compatibility. The three can be uniformly distributed in the alloy to form a stable organizational structure. This uniform and stable structure not only improves the overall performance of the alloy but also reduces the generation of local performance differences and defects, further enhancing the reliability and consistency of the alloy.

[0018] Preferably, in the preparation method of the Sn-In-Nd-graphene hybrid material, the addition amount of absolute ethanol in step (1) is 2-3 times the mass of graphene; the addition amount of absolute ethanol in step (2) is 2-3 times the total mass of Sn powder, In powder, and Nd powder.

[0019] Preferably, in the preparation method of the Sn-In-Nd-graphene hybrid material, the parameters of ultrasonic dispersion in step (1) are: power 500-600 W, time 10-20 min.

[0020] Preferably, in the preparation method of the Sn-In-Nd-graphene hybrid material, the parameters of ultrasonic dispersion in step (2) are: power 500-600 W, time 20-40 min.

[0021] Preferably, in the preparation method of the Sn-In-Nd-graphene hybrid material, the ball-to-material ratio in step (3) is (4-5):1, and the ball-milling time is 2-3 h.

[0022] Preferably, the preparation method of the Cu-Ag core-shell particles includes the following steps:

[0023] S1. Mix nano-copper powder with deionized water, sodium citrate, and sodium hypophosphite to obtain solution A; wherein, the molar ratio of nano-copper powder, sodium citrate, and sodium hypophosphite is 1:(0.5-1):(2-4), and the addition amount of deionized water is 1-2 times the total mass of nano-copper powder, sodium citrate, and sodium hypophosphite;

[0024] S2. Mix sodium citrate, silver sulfate, and deionized water to obtain solution B; wherein, the molar ratio of sodium citrate to silver sulfate is 1:(0.5-1), and the addition amount of deionized water is 1-2 times the total mass of sodium citrate and silver sulfate;

[0025] S3. Drop solution B into solution A and react at 25-30 °C until the solution changes from red to purple and then to grayish brown;

[0026] S4. Centrifuge the reacted solution, wash the precipitate, and dry it to obtain the Cu-Ag core-shell particles.

[0027] More preferably, the average particle size of the nano-copper powder is 50 nm, but it is not limited to 50 nm.

[0028] Preferably, the preparation method of the Sn-Ag-Sb-Ni alloy includes the following steps:

[0029] Under a nitrogen atmosphere, melt elemental Sn, elemental Ag, elemental Sb, and elemental Ni at 1000-1200 °C to obtain the Sn-Ag-Sb-Ni alloy.

[0030] During the alloy melting and casting process, metals such as Sn and Ag are prone to react with oxygen to form oxides such as SnO2 and Ag2O. By melting in a nitrogen atmosphere, oxygen contact can be isolated, and the formation of oxides can be reduced.

[0031] In a second aspect, the present invention provides the preparation method of the high-reliability tin-silver-copper-based alloy, including the following steps:

[0032] Ball-mill the Sn-In-Nd-graphene hybrid material and the Cu-Ag core-shell particles to obtain a mixture; melt the mixture with the Sn-Ag-Sb-Ni alloy to obtain the high-reliability tin-silver-copper-based alloy.

[0033] Preferably, the ratio of balls to materials is (2 - 3):1, and the ball milling time is 20 - 40 min.

[0034] Preferably, the melting temperature is 300 - 400 °C, and the melting time is 1 - 2 h.

[0035] In a third aspect, the present invention provides the application of the high - reliability tin - silver - copper - based alloy in the preparation of high - reliability solder paste. After grinding the high - reliability tin - silver - copper - based alloy into powder with a particle size of 15 - 40 μm, it is then mixed with a flux to form solder paste.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] The main components of the alloy in the present invention are Sn - Ag - Sb - Ni alloy, Sn - In - Nd - graphene hybrid material, and Cu - Ag core - shell particles. Among them, the Sn - Ag - Sb - Ni alloy serves as the alloy matrix, which can absorb energy through plastic deformation to avoid brittle fracture. At the same time, the multi - component elements in the alloy can form a variety of stable precipitation phases, and the multi - component precipitation phases contained therein can improve the high - temperature stability; the Sn - In - Nd - graphene hybrid material serves as the reinforcing phase, bearing the main mechanical load, dispersing stress through nano - reinforcement and intermetallic compounds, and because it contains Sn, it has good bonding with the alloy matrix; the Cu - Ag core - shell particles serve as the stress - buffering medium, coordinating the thermal expansion difference between the alloy matrix and the reinforcing phase, and suppressing the interfacial reaction through the Ag shell; the combined action of the three makes the stress distribution of the alloy more uniform under tensile, bending and other loads, avoiding local overload failure, so that the alloy has high reliability. The alloy of the present invention simultaneously meets the requirements of automotive electronics for high temperature resistance, vibration resistance, and long life, as well as the requirements of the AI field for ultra - high thermal conductivity, high - precision connection, and anti - electromigration, and becomes an ideal material for high - performance electronic packaging. Specific Embodiments

[0038] To better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0039] Other materials, reagents, etc. used in the examples and comparative examples can be obtained from commercial channels without special instructions.

[0040] Example 1

[0041] A high - reliability tin - silver - copper - based alloy, comprising the following raw materials for preparation in weight percentage: 8% of Sn - In - Nd - graphene hybrid material, 6% of Cu - Ag core - shell particles, and the balance is Sn - Ag - Sb - Ni alloy;

[0042] Among them, the Sn-In-Nd-graphene hybrid material comprises the following components by weight percentage: In 3.5%, Nd 0.6%, and graphene 4%, with the balance being Sn and inevitable impurities;

[0043] The Sn-Ag-Sb-Ni alloy comprises the following components by weight percentage: Ag 5%, Sb 0.33%, and Ni 0.3%, with the balance being Sn and inevitable impurities;

[0044] The preparation method of the Sn-In-Nd-graphene hybrid material comprises the following steps:

[0045] (1) Ultrasonically disperse graphene in absolute ethanol to obtain a graphene slurry; wherein, the addition amount of absolute ethanol is 2 times the mass of graphene, the ultrasonic power is 550 W, and the ultrasonic dispersion time is 15 min;

[0046] (2) Ultrasonically disperse Sn powder, In powder, and Nd powder in absolute ethanol to obtain an alloy slurry; wherein, the addition amount of absolute ethanol is 2 times the total mass of Sn powder, In powder, and Nd powder, the ultrasonic power is 550 W, and the ultrasonic dispersion time is 30 min;

[0047] (3) Mix the graphene slurry and the alloy slurry and then carry out ball milling and vacuum drying to obtain a Sn-In-Nd-graphene precursor powder; wherein, the ball-to-material ratio of ball milling is 4:1, and the ball milling time is 3 h;

[0048] (4) First melt the Sn-In-Nd-graphene precursor powder at 650 °C for 2 h, then raise the temperature to 1600 °C and continue melting for 1.5 h, and keep it warm for 10 min to obtain the Sn-In-Nd-graphene hybrid material;

[0049] The preparation method of the Cu-Ag core-shell particles comprises the following steps:

[0050] S1. Mix nano copper powder with deionized water, sodium citrate, and sodium hypophosphite to obtain solution A; wherein, the molar ratio of nano copper powder, sodium citrate, and sodium hypophosphite is 1:0.8:3, and the addition amount of deionized water is 1.5 times the total mass of nano copper powder, sodium citrate, and sodium hypophosphite; the average particle size of the nano copper powder is 50 nm;

[0051] S2. Mix sodium citrate, silver sulfate, and deionized water to obtain solution B; wherein, the molar ratio of sodium citrate to silver sulfate is 1:0.6, and the addition amount of deionized water is 1.5 times the total mass of sodium citrate and silver sulfate;

[0052] S3. Drop solution B into solution A and carry out the reaction at 25 °C until the solution changes from red to purple and then to grayish brown;

[0053] S4. Centrifuge the reacted solution, wash the precipitate, and dry it to obtain the Cu-Ag core-shell particles.

[0054] The preparation method of the Sn-Ag-Sb-Ni alloy includes the following steps:

[0055] Under a nitrogen atmosphere, melt Sn powder, Ag powder, Sb powder, and Ni powder at 1100 °C to obtain the Sn-Ag-Sb-Ni alloy;

[0056] The preparation method of the high-reliability tin-silver-copper-based alloy includes the following steps:

[0057] Ball-mill the Sn-In-Nd-graphene hybrid material and the Cu-Ag core-shell particles for 30 min under the condition that the ball-to-material ratio is 2.5:1 to obtain a mixture; melt the mixture and the Sn-Ag-Sb-Ni alloy at 350 °C for 1.5 h to obtain the high-reliability tin-silver-copper-based alloy.

[0058] Example 2

[0059] A high-reliability tin-silver-copper-based alloy includes the following raw materials for preparation by weight percentage: 5% of the Sn-In-Nd-graphene hybrid material, 5% of the Cu-Ag core-shell particles, and the balance is the Sn-Ag-Sb-Ni alloy; wherein, the Sn-In-Nd-graphene hybrid material includes the following components by weight percentage: 3% of In, 0.5% of Nd, and 3% of graphene, and the balance is Sn and inevitable impurities;

[0060] The Sn-Ag-Sb-Ni alloy includes the following components by weight percentage: 4% of Ag, 0.1% of Sb, and 0.1% of Ni, and the balance is Sn and inevitable impurities;

[0061] The preparation method of the Sn-In-Nd-graphene hybrid material includes the following steps:

[0062] (1) Ultrasonically disperse graphene in absolute ethanol to obtain a graphene slurry; wherein, the addition amount of absolute ethanol is 2 times the mass of graphene, the ultrasonic power is 500 W, and the ultrasonic dispersion time is 20 min;

[0063] (2) Ultrasonically disperse Sn powder, In powder, and Nd powder in absolute ethanol to obtain an alloy slurry; wherein, the addition amount of absolute ethanol is 2 times the total mass of Sn powder, In powder, and Nd powder, the ultrasonic power is 500 W, and the ultrasonic dispersion time is 40 min;

[0064] (3) Mix the graphene slurry and the alloy slurry and then perform ball milling and vacuum drying to obtain the Sn-In-Nd-graphene precursor powder; wherein, the ball-to-material ratio for ball milling is 4:1, and the ball milling time is 3 h;

[0065] (4) First, melt the Sn-In-Nd-graphene precursor powder at 600 °C for 3 h, then raise the temperature to 1500 °C and continue melting for 2 h, and keep the temperature for 10 min to obtain the Sn-In-Nd-graphene hybrid material;

[0066] The preparation method of the Cu-Ag core-shell particles includes the following steps:

[0067] S1. Mix nano copper powder with deionized water, sodium citrate, and sodium hypophosphite to obtain solution A; among them, the molar ratio of nano copper powder, sodium citrate, and sodium hypophosphite is 1:0.5:2, and the addition amount of deionized water is 1 time the total mass of nano copper powder, sodium citrate, and sodium hypophosphite; the average particle size of nano copper powder is 50 nm;

[0068] S2. Mix sodium citrate, silver sulfate, and deionized water to obtain solution B; among them, the molar ratio of sodium citrate to silver sulfate is 1:0.5, and the addition amount of deionized water is 1 time the total mass of sodium citrate and silver sulfate;

[0069] S3. Drop solution B into solution A and react at 25 °C until the solution changes from red to purple and then to grayish brown;

[0070] S4. Centrifuge the reacted solution, wash the precipitate, and dry it to obtain the Cu-Ag core-shell particles.

[0071] The preparation method of the Sn-Ag-Sb-Ni alloy includes the following steps:

[0072] Under a nitrogen atmosphere, melt Sn powder, Ag powder, Sb powder, and Ni powder at 1000 °C to obtain the Sn-Ag-Sb-Ni alloy;

[0073] The preparation method of the high-reliability tin-silver-copper-based alloy includes the following steps:

[0074] Ball-mill the Sn-In-Nd-graphene hybrid material and the Cu-Ag core-shell particles for 40 min under the condition of a ball-to-material ratio of 2:1 to obtain a mixture; melt the mixture and the Sn-Ag-Sb-Ni alloy at 300 °C for 2 h to obtain the high-reliability tin-silver-copper-based alloy.

[0075] Example 3

[0076] A high-reliability tin-silver-copper alloy system, comprising preparation raw materials in the following weight percentages: 10% of Sn-In-Nd-graphene hybrid material, 10% of Cu-Ag core-shell particles, and the balance being Sn-Ag-Sb-Ni alloy; wherein, the Sn-In-Nd-graphene hybrid material comprises components in the following weight percentages: 4% of In, 1% of Nd, and 5% of graphene, and the balance being Sn and inevitable impurities;

[0077] The Sn-Ag-Sb-Ni alloy comprises components in the following weight percentages: 7% of Ag, 0.5% of Sb, and 0.5% of Ni, and the balance being Sn and inevitable impurities;

[0078] The preparation method of the Sn-In-Nd-graphene hybrid material comprises the following steps:

[0079] (1) Ultrasonically disperse graphene in absolute ethanol to obtain a graphene slurry; wherein, the addition amount of absolute ethanol is 3 times the mass of graphene, the ultrasonic power is 600 W, and the ultrasonic dispersion time is 10 min;

[0080] (2) Ultrasonically disperse Sn powder, In powder, and Nd powder in absolute ethanol to obtain an alloy slurry; wherein, the addition amount of absolute ethanol is 3 times the total mass of Sn powder, In powder, and Nd powder, the ultrasonic power is 600 W, and the ultrasonic dispersion time is 20 min;

[0081] (3) Mix the graphene slurry and the alloy slurry, then perform ball milling and vacuum drying to obtain Sn-In-Nd-graphene precursor powder; wherein, the ball-to-material ratio of ball milling is 5:1, and the ball milling time is 2 h;

[0082] (4) First melt the Sn-In-Nd-graphene precursor powder at 700 °C for 2 h, then raise the temperature to 1700 °C and continue melting for 1 h, and keep it warm for 5 min to obtain the Sn-In-Nd-graphene hybrid material.

[0083] The preparation method of the Cu-Ag core-shell particles comprises the following steps:

[0084] S1. Mix nano copper powder with deionized water, sodium citrate, and sodium hypophosphite to obtain solution A; wherein, the molar ratio of nano copper powder, sodium citrate, and sodium hypophosphite is 1:1:4, and the addition amount of deionized water is 2 times the total mass of nano copper powder, sodium citrate, and sodium hypophosphite; the average particle size of nano copper powder is 50 nm;

[0085] S2. Mix sodium citrate, silver sulfate, and deionized water to obtain solution B; wherein, the molar ratio of sodium citrate and silver sulfate is 1:1, and the addition amount of deionized water is 2 times the total mass of sodium citrate and silver sulfate;

[0086] S3. Add solution B dropwise to solution A and carry out the reaction at 30 °C until the solution changes from red to purple and then to grayish brown;

[0087] S4. Centrifuge the reacted solution, wash the precipitate, and dry it to obtain the Cu-Ag core-shell particles.

[0088] The preparation method of the Sn-Ag-Sb-Ni alloy includes the following steps:

[0089] Under a nitrogen atmosphere, melt Sn powder, Ag powder, Sb powder and Ni powder at 1200 °C to obtain the Sn-Ag-Sb-Ni alloy;

[0090] The preparation method of the high-reliability tin-silver-copper-based alloy includes the following steps:

[0091] Ball-mill the Sn-In-Nd-graphene hybrid material and the Cu-Ag core-shell particles for 20 min under the condition that the ball-to-material ratio is 3:1 to obtain a mixture; melt the mixture and the Sn-Ag-Sb-Ni alloy at 400 °C for 1-2 h to obtain the high-reliability tin-silver-copper-based alloy.

[0092] Comparative Example 1

[0093] The difference from Example 1 is that: the Sn-In-Nd-graphene hybrid material is not added, and the missing amount is supplemented with Cu-Ag core-shell particles and Sn-Ag-Sb-Ni alloy with a mass ratio of 6:86.

[0094] Comparative Example 2

[0095] The difference from Example 1 is that: the Cu-Ag core-shell particles are not added, and the missing amount is supplemented with Sn-In-Nd-graphene hybrid material and Sn-Ag-Sb-Ni alloy with a mass ratio of 8:86.

[0096] Comparative Example 3

[0097] The difference from Example 1 is that: the addition amount of the Sn-In-Nd-graphene hybrid material remains unchanged, and the Sn-In-Nd-graphene hybrid material includes the following components by weight percentage: In 0.6%, Nd 3.5% and graphene 4%, and the balance is Sn and inevitable impurities.

[0098] Comparative Example 4

[0099] The difference from Example 1 is that: the addition amount of the Sn-In-Nd-graphene hybrid material remains unchanged, and the Sn-In-Nd-graphene hybrid material includes the following components by weight percentage: In 3.5%, Nd 4% and graphene 0.6%, and the balance is Sn and inevitable impurities.

[0100] Comparative Example 5

[0101] The difference from Example 1 is that In in the Sn-In-Nd-graphene hybrid material is moved to the Sn-Ag-Sb-Ni alloy to obtain an Sn-Ag-Sb-Ni-In alloy.

[0102] Performance Test

[0103] 1. Mechanical Property Test of the Alloy

[0104] The hardness of the alloys in Examples 1-3 and Comparative Examples 1-5 was tested respectively by the standard method of GB / T 231.1-2018 "Metallic materials - Brinell hardness test - Part 1: Test method", and the elongation and tensile strength were tested by GB / T 228.1-2010 "Metallic materials - Tensile testing - Part 1: Method of test at room temperature". The specific data are shown in Table 1.

[0105] 2. Test of High Stability of the Solder Paste

[0106] The alloys in each group were ground into powders with a particle size of 15-40 μm, and the alloy powders were made into solder paste. The specific steps are as follows: 84 wt% alloy powder and 16 wt% water-soluble lead-free soldering flux were placed in a disperser and stirred at a stirring speed of 20 r / min for 10 min, then evacuated to 0.06 Mpa for 10 min, and stirring continued during evacuation. As a result, a solder paste with a viscosity of 50 Pa·s was obtained. Among them, the raw materials and preparation method of the water-soluble lead-free soldering flux refer to Example 1 of CN112589318B.

[0107] The prepared solder paste was tested as follows: the surface insulation resistance was tested by GB / T 31474-2015, the dielectric loss (1 MHz) was tested by IPC-TM-650 2.5.5.9, the corrosion resistance was tested by IPC-TM-650 2.6.15, and the spread rate was tested by IPC-TM-650 2.4.35. The specific results are shown in Table 2.

[0108] Table 1 Test Results of Mechanical Properties of Alloy Samples in Each Group

[0109] Group Hardness / HB Elongation / % Tensile strength / MPa Example 1 32.7 23.3 122.1 Example 2 30.4 20.8 112.2 Example 3 31.8 21.6 121.5 Comparative Example 1 16.0 12.7 71.9 Comparative Example 2 18.3 14.4 73.7 Comparative Example 3 26.2 16.1 81.6 Comparative Example 4 26.0 15.2 85.3 Comparative Example 5 28.2 17.7 86.3

[0110] As shown in Table 1, combined with the data of Examples 1-3 and Comparative Examples 1-2, it can be seen that in Comparative Example 1, no Sn-In-Nd-graphene mixed material is added, and its mechanical properties are significantly reduced compared with Example 1. This may be because after the lack of Sn-In-Nd-graphene mixed material, the stress cannot be effectively dispersed through the graphene skeleton, resulting in a significant decrease in the mechanical strength of the alloy. At the same time, the lack of In leads to a decrease in the porosity of the alloy, and the lack of Nd causes the alloy to be unable to form a dense Nd2O3 protective film at high temperatures, and the high-temperature stability of the alloy is reduced. In Comparative Example 2, no Cu-Ag core-shell particles are added, and its mechanical properties are significantly reduced compared with Example 1. This may be because the Cu-Ag core-shell particles can coordinate the deformation of the soft / hard areas through the core-shell structure, while maintaining plasticity while improving strength, and the lack of Cu-Ag core-shell particles may destroy the strength-ductility balance, and plasticity may be reduced due to the simplification of the strengthening mechanism. Therefore, the Sn-In-Nd-graphene hybrid material, Cu-Ag core-shell particles and Sn-Ag-Sb-Ni alloy have synergistic alloy mechanical properties.

[0111] Combined with the data of Example 1 and Comparative Examples 3-4, it can be seen that in the Sn-In-Nd-graphene mixed material, if the graphene addition is less than 3%, the mechanical properties of the alloy are significantly reduced. This may be because the graphene content is too low to form an effective three-dimensional reinforcement network, the load transfer efficiency is reduced, and the inhibition of graphene on grain boundary sliding is weakened, and the plasticity is reduced. Similarly, if the In addition is less than 3%, it is difficult for the alloy to form a dense structure during welding or smelting, and the porosity is increased, thereby reducing the alloy performance. When the Nd content is higher than 1%, excessive Nd may form more coarse Nd compounds in the alloy, and these coarse compounds will split the matrix and destroy the continuity of the alloy, thereby affecting the mechanical properties of the alloy. Therefore, when the Sn-In-Nd-graphene mixed material includes the following weight percentage components: In 3-4%, Nd 0.5-1% and graphene 3-5%, the balance is Sn and unavoidable impurities, the performance of its alloy is at a better level.

[0112] Combining the data of Example 1 and Comparative Example 5, it can be seen that the mechanical properties of the alloy of Comparative Example 5 are significantly lower than those of Example 1. This may be because In and Nd in the graphene hybrid material Sn-In-Nd system can form nano-scale InNd intermetallic compounds (IMC), pinning the grain boundaries to inhibit grain coarsening, and when In migrates, Nd in the Sn-In-Nd system cannot effectively form IMC, resulting in grain coarsening and reducing the mechanical properties of the alloy. After the Sn-Ag-Sb-Ni-In alloy is formed, In and Ni form a brittle NiIn3 phase, further reducing the mechanical properties of the alloy, so it is explained that the addition position of In is also an important parameter affecting the mechanical properties of the alloy, such as hardness, elongation and tensile strength.

[0113] Table 2 Reliability test data of solder pastes for each group

[0114] Group Surface insulation impedance Dielectric loss (1 MHz) Corrosion resistance Expansion rate / % Example 1 <![CDATA[2.8×10 12 > 0.0115 No penetration 92.6 Example 2 <![CDATA[2.1×10 12 > 0.0130 No penetration 88.1 Example 3 <![CDATA[2.6×10 12 > 0.0118 No penetration 91.3 Comparative Example 1 <![CDATA[2.7×10 10 > 0.0857 Local penetration 75.0 Comparative Example 2 <![CDATA[3.2×10 10 > 0.0816 Local penetration 74.3 Comparative Example 3 <![CDATA[6.2×10 11 > 0.0408 Local penetration 85.6 Comparative Example 4 <![CDATA[6.9×10 11 > 0.0369 No penetration 86.0 Comparative Example 5 <![CDATA[6.5×10 11 > 0.0611 Local penetration 88.4

[0115] As can be seen from Table 2, combining the data of Example 1 and Comparative Examples 1-2, the reliability test data of Example 1 are significantly better than those of Comparative Examples 1-2. This may be because the synergistic strengthening and antioxidant effects of the Sn-In-Nd-graphene hybrid material are missing, resulting in significant deterioration in thermomechanical reliability, drop resistance and long-term stability. The wetting regulation and mechanical strengthening effects of the Cu-Ag core-shell particles are missing, and there are obvious shortcomings in welding quality, interface stability and electromigration resistance. Therefore, the absence of any component of the alloy of the present invention will lead to a sharp increase in interface defects and cannot meet the stringent requirements of new energy vehicle electronics and AI chip packaging for highly reliable solder pastes.

[0116] Combining the data of Example 1 and Comparative Examples 3-4, it can be seen that in the Sn-In-Nd-graphene hybrid material, the mass ratio of each component is also an important parameter affecting the reliability of the solder paste. If the components are too much or too little, it will be difficult to form a uniform graphene / metal interface bond in the hybrid material, and the oxidation of the Sn matrix surface not covered by graphene will be aggravated, thereby reducing the reliability of the solder paste.

[0117] Combining the data of Example 1 and Comparative Example 5, it can be seen that the position of In will affect the reliability of the solder paste. This may be because In does not play the role of refining grains and improving wettability in the Sn-In-Nd-graphene hybrid material, resulting in coarse alloy structure, affecting the fluidity and wettability of the solder paste, reducing the spread rate, and affecting the welding quality. Therefore, the present invention sets In in the graphene hybrid material system to ensure its synergistic effects on graphene dispersion, grain refinement and interface strengthening, and to avoid reliability deterioration caused by improper distribution or abnormal content.

[0118] In summary, the alloy of the present invention makes the stress distribution of the alloy more uniform under loads such as tension and bending through the combined action of the Sn-In-Nd-graphene hybrid material, the Cu-Ag core-shell particles and the Sn-Ag-Sb-Ni alloy, avoiding local overload failure and making the alloy have high reliability.

[0119] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A high-reliability tin-silver-copper alloy, characterized in that, The preparation raw materials include the following by weight percentage: 5-10% of Sn-In-Nd-graphene hybrid material, 5-10% of Cu-Ag core-shell particles, and the balance is Sn-Ag-Sb-Ni alloy; Among them, the Sn-In-Nd-graphene hybrid material includes the following components by weight percentage: 3-4% of In, 0.5-1% of Nd, and 3-5% of graphene, and the balance is Sn and inevitable impurities; The Sn-Ag-Sb-Ni alloy includes the following components by weight percentage: 4-7% of Ag, 0.1-0.5% of Sb, and 0.1-0.5% of Ni, and the balance is Sn and inevitable impurities; The preparation method of the Sn-In-Nd-graphene hybrid material includes the following steps: (1) Ultrasonically disperse graphene in absolute ethanol to obtain a graphene slurry; (2) Ultrasonically disperse Sn powder, In powder, and Nd powder in absolute ethanol to obtain an alloy slurry; (3) Mix the graphene slurry and the alloy slurry, then carry out ball milling and vacuum drying to obtain Sn-In-Nd-graphene precursor powder; (4) First melt the Sn-In-Nd-graphene precursor powder at 600-700 °C for 2-3 h, then raise the temperature to 1500-1700 °C and continue melting for 1-2 h, and keep the temperature for 5-10 min to obtain the Sn-In-Nd-graphene hybrid material.

2. The high-reliability tin-silver-copper-based alloy according to claim 1, characterized in that, In the step (1), the addition amount of absolute ethanol is 2-3 times the mass of graphene; in the step (2), the addition amount of absolute ethanol is 2-3 times the total mass of Sn powder, In powder, and Nd powder.

3. The high-reliability tin-silver-copper-based alloy according to claim 1, wherein In the step (3), the ball-to-material ratio of ball milling is (4-5):1, and the ball milling time is 2-3 h.

4. The high-reliability tin-silver-copper alloy according to claim 1, characterized in that, The preparation method of the Cu-Ag core-shell particles includes the following steps: S1. Mix nano copper powder with deionized water, sodium citrate, and sodium hypophosphite to obtain solution A; among them, the molar ratio of nano copper powder, sodium citrate, and sodium hypophosphite is 1:(0.5-1):(2-4), and the addition amount of deionized water is 1-2 times the total mass of nano copper powder, sodium citrate, and sodium hypophosphite; S2. Mix sodium citrate, silver sulfate, and deionized water to obtain solution B; among them, the molar ratio of sodium citrate to silver sulfate is 1:(0.5-1), and the addition amount of deionized water is 1-2 times the total mass of sodium citrate and silver sulfate; S3. Drop solution B into solution A and react at 25-30 °C until the solution changes from red to purple and then to grayish brown; S4. Centrifuge the reacted solution, wash the precipitate, and dry it to obtain the Cu-Ag core-shell particles.

5. The high-reliability tin-silver-copper alloy according to claim 4, characterized in that, The average particle size of the nano copper powder is 50 nm.

6. The high-reliability tin-silver-copper-based alloy according to claim 1, wherein The preparation method of the Sn-Ag-Sb-Ni alloy includes the following steps: Under a nitrogen atmosphere, melt Sn powder, Ag powder, Sb powder, and Ni powder at 1000-1200 °C to obtain the Sn-Ag-Sb-Ni alloy.

7. The preparation method of the high-reliability tin-silver-copper alloy according to any one of claims 1-6, characterized in that, Include the following steps: The Sn-In-Nd-graphene hybrid material and Cu-Ag core-shell particles are ball-milled to obtain a mixture; the mixture is smelted with a Sn-Ag-Sb-Ni alloy to obtain the high-reliability tin-silver-copper-based alloy.

8. The preparation method of the high-reliability tin-silver-copper-based alloy according to claim 7, characterized in that, The ball-to-material ratio is (2-3):1, and the ball-milling time is 20-40 min; and / or, the smelting temperature is 300-400 °C, and the smelting time is 1-2 h.

9. Use of the high-reliability tin-silver-copper-based alloy according to any one of claims 1-8 in the preparation of solder paste.