High-reliability low-melting-point tin-based alloy and preparation method thereof

Abstract

The application relates to the technical field of alloy processing, in particular to a high-reliability low-melting-point tin-based alloy and a preparation method thereof, which comprises a base material, a reinforcing material and a micro-alloying additive, the base material is composed of the following raw materials in parts by weight: tin: 52-68 parts; bismuth: 10-15 parts; the reinforcing material is composed of the following raw materials in parts by weight: indium: 3-8 parts; silver: 1-3 parts; antimony: 0.5-2 parts; copper: 0.3-1.2 parts. The application realizes the balance between environmental protection and performance by replacing lead with bismuth, indium and silver elements through multi-element composite reinforcement and micro-alloying technology, the melting point can be adjusted to 138-180 DEG C, the excellent tensile strength, elongation and high-temperature creep resistance are combined, meanwhile, the oxygen content and segregation risk are significantly reduced by adopting vacuum melting combined with a staged micro-alloying process to precisely control the element addition sequence and diffusion conditions, the material homogeneity is improved by introducing rare earth cerium to purify the grain boundary, and compared with a traditional process, the energy consumption is reduced and the yield of finished products is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of alloy processing, in particular to a high-reliability low-melting-point tin-based alloy and a preparation method thereof. BACKGROUND

[0002] A tin-based alloy is a multi-functional alloy system formed by adding other metals or non-metallic elements to tin as the main base element, and its core characteristics include low melting point, good wettability and corrosion resistance, and is widely used in electronic welding, sliding bearings, food packaging and other fields. Traditional tin-based alloys are represented by tin-lead alloys, which rely on lead elements to reduce the melting point and cost, but the toxicity of lead poses a serious threat to the environment and human health, and traditional preparation processes have problems such as high energy consumption, composition segregation and performance limitations.

[0003] Generally, traditional tin-based alloys are mainly tin-lead solder and babbitt alloy, and are prepared by combining simple rolling process with melting and casting. Such alloys contain lead or rely on a high proportion of heavy metals, and face restrictions from environmental regulations. At the same time, high-temperature melting in the process leads to high energy consumption, and composition control is not accurate, which can easily produce defects such as pores and grain coarsening. In addition, traditional alloys have short boards in high-temperature strength, creep resistance and welding reliability, and are difficult to meet the requirements of modern precision electronic devices and high-temperature mechanical parts.

[0004] Therefore, the present application provides a high-reliability low-melting-point tin-based alloy and a preparation method thereof to solve the above technical problems. SUMMARY

[0005] The present application aims to provide a high-reliability low-melting-point tin-based alloy and a preparation method thereof to solve the problems mentioned in the background.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical scheme:

[0007] The present application provides a high-reliability low-melting-point tin-based alloy, which comprises a base material, a reinforcing material and a micro-alloying additive, the base material is composed of the following raw materials by weight: tin: 52-68 parts; bismuth: 10-15 parts;

[0008] The reinforcing material is composed of the following raw materials by weight: indium: 3-8 parts; silver: 1-3 parts; antimony: 0.5-2 parts; copper: 0.3-1.2 parts;

[0009] The micro-alloying additive is composed of the following raw materials by weight: germanium: 0.05-0.15 parts; gallium: 0.1-0.5 parts; nickel: 0.05-0.2 parts; phosphorus: 0.01-0.08 parts; rare earth cerium: 0.005-0.03 parts.

[0010] Preferably, the indium is prepared by electrolytic refining of crude indium in sulfuric acid electrolyte at 40-60℃ with current density of 100-200A / m 2 .

[0011] Preferably, the silver is prepared by chemical reduction of silver nitrate solution at 50-80℃ with glucose as reducing agent, washed and dried.

[0012] Preferably, the antimony is prepared by reduction of antimony sulfide ore with coke in a smelting furnace at 600-800℃.

[0013] Preferably, the copper is prepared by electrolytic refining of crude copper in electrolyte containing copper sulfate at 50-70℃ with cathode current density of 200-300A / m 2 .

[0014] Preferably, the germanium is prepared by reduction distillation of germanium tetrachloride gas in hydrogen atmosphere at 1000-1200℃.

[0015] Preferably, the gallium is prepared by electrolytic oxidation of bauxite electrolyte at 30-50℃ with current efficiency ≥85%.

[0016] Preferably, the rare earth cerium is prepared by extraction separation of mixed rare earth oxides in acidic solution at 20-40℃ with P507 extractant.

[0017] Based on the above tin-based alloy formula, the present application further proposes a preparation method of high-reliability low-melting-point tin-based alloy, comprising the following steps:

[0018] S1. Take tin 52-68 parts and bismuth 10-15 parts by mass fraction, clean the surface oxides and grease in ethanol at 60-80℃ for 10-15 minutes using an ultrasonic cleaning machine, and then dry in a vacuum drying oven at 80-100℃ for 2-3 hours. Take indium 3-8 parts, silver 1-3 parts, antimony 0.5-2 parts, copper 0.3-1.2 parts, and copper needs to be soaked in 10% dilute sulfuric acid for 5 minutes for pickling. Other materials are cleaned with acetone for 10 minutes, dried, and then used. Accurately weigh germanium 0.05-0.15 parts, gallium 0.1-0.5 parts, nickel 0.05-0.2 parts, phosphorus 0.01-0.08 parts, and rare earth cerium 0.005-0.03 parts. Among them, phosphorus is added in the form of red phosphorus powder, and rare earth cerium needs to be ground to 200 mesh or less;

[0019] S2. Put the pretreated tin, bismuth, indium, silver, antimony, and copper into a graphite crucible in order, vacuumize the furnace body to 5×10 -3Pa below, fill in high-purity argon to the furnace pressure 0.05-0.1 MPa, open the induction heating, to 220-250 DEG C at a rate of 20-30 DEG C / min, constant temperature smelting 30-40 minutes, while starting mechanical stirrer to ensure uniform melt, by online spectrometer real-time monitoring melt composition, adjust the heating power or stirring rate to compensate for the loss of volatile;

[0020] S3. The melt temperature is reduced to 180-200 DEG C, the stirrer is turned off, and the germanium, gallium, nickel and phosphorus powders are evenly scattered onto the surface of the melt through a glove box, the feeding time is controlled to be 5-8 minutes, the temperature is increased to 190-210 DEG C, and the low-frequency electromagnetic stirring is started for 20-25 minutes to promote the diffusion of micro-alloying elements and avoid segregation.

[0021] S4. The ground rare earth cerium powder is poured into the melt through a feeding pipe, the temperature is kept at 190-200 DEG C, and the cerium element is allowed to absorb impurities and float for 10-15 minutes, the melt is filtered twice by using a ceramic filter screen to remove dross and unmelted particles, and the oxygen content of the melt is reduced to ≤50 ppm.

[0022] S5. The mold is preheated to 80-120 DEG C, the surface is sprayed with a boron nitride coating to prevent alloy adhesion, the melt is injected into the mold through a flow guide groove at a flow rate of 1.5-2.0 L / min, the pouring temperature is controlled to be 175-185 DEG C to avoid secondary oxidation, the water cooling system is started to cool the alloy to room temperature at a rate of 10-20 DEG C / s to inhibit the formation of coarse grains.

[0023] S6. The ingot is kept in a vacuum annealing furnace at 120-150 DEG C for 2-3 hours to eliminate internal stress and improve ductility, and the alloy is processed to the target thickness by using a cold rolling process to obtain a uniform microstructure.

[0024] S7. The alloy composition is detected by using XRF, the deviation needs to be controlled to be within ±1% of the quality parts interval, and the qualified products after quality inspection are sealed in a nitrogen protection bag, and the storage temperature is ≤25 DEG C and the humidity is ≤30% RH.

[0025] Preferably, the quality inspection in the step S7 includes testing the tensile strength, elongation, wetting angle and high-temperature creep performance.

[0026] Compared with the prior art, the present application has the following beneficial effects:

[0027] The present application realizes the balance of environmental protection and performance by replacing lead with bismuth, indium and silver elements through multi-element composite strengthening and micro-alloying technology, the melting point can be adjusted to 138-180 DEG C, and excellent tensile strength, elongation and high temperature creep resistance are combined, at the same time, the element adding sequence and diffusion conditions are precisely controlled by adopting vacuum melting combined with staged micro-alloying process, the oxygen content and segregation risk are significantly reduced, the material homogeneity is improved by introducing rare earth cerium to purify the grain boundary, the energy consumption is reduced compared with the traditional process, the yield is improved, and the composition completely meets the international environmental protection standard, and the application field is more extensive. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0029] I. Material

[0030] Unless otherwise specified, the tin-based alloy formula of the present application is commercially available.

[0031] The present application provides a high-reliability low-melting-point tin-based alloy, which comprises a base material, a reinforcing material and a micro-alloying additive, the base material is composed of the following raw materials in parts by weight: tin: 52-68 parts; bismuth: 10-15 parts;

[0032] The reinforcing material is composed of the following raw materials in parts by weight: indium: 3-8 parts; silver: 1-3 parts; antimony: 0.5-2 parts; copper: 0.3-1.2 parts;

[0033] The micro-alloying additive is composed of the following raw materials in parts by weight: germanium: 0.05-0.15 parts; gallium: 0.1-0.5 parts; nickel: 0.05-0.2 parts; phosphorus: 0.01-0.08 parts; rare earth cerium: 0.005-0.03 parts.

[0034] It should be further pointed out that the indium is prepared by electrolytic refining of coarse indium in a 40-60 DEG C sulfuric acid electrolyte with a current density of 100-200 A / m 2 .

[0035] It should be further pointed out that the silver is prepared by chemical reduction method by taking glucose as a reducing agent to precipitate silver powder from silver nitrate solution at 50-80 DEG C, and then dried after washing.

[0036] It should be further pointed out that the antimony is prepared by reducing the antimony sulfide ore in a coke reduction furnace at 600-800 DEG C.

[0037] Wherein, it needs to be noted that the copper is prepared by electrolytic refining of the crude copper at 50-70℃ in an electrolyte containing copper sulfate with a cathode current density of 200-300 A / m 2 .

[0038] Wherein, it needs to be noted that the germanium is prepared by reduction distillation of germanium tetrachloride gas at 1000-1200℃ in a hydrogen atmosphere.

[0039] Wherein, it needs to be noted that the gallium is prepared by electrolytic oxidation purification of bauxite electrolyte at 30-50℃ with an electrolytic efficiency of ≥85%.

[0040] Wherein, it needs to be noted that the rare earth cerium is prepared by extraction separation of mixed rare earth oxides in an acidic solution at 20-40℃ using P507 extractant.

[0041] II. Process:

[0042] Based on the above tin-based alloy formula, the application also proposes a preparation method of high-reliability low-melting-point tin-based alloy, comprising the following steps:

[0043] S1. Take tin 52-68 parts and bismuth 10-15 parts by mass fraction, use an ultrasonic cleaning machine to clean in ethanol at 60-80℃ for 10-15 minutes to remove surface oxides and grease, then dry in a vacuum drying oven at 80-100℃ for 2-3 hours, respectively take indium 3-8 parts, silver 1-3 parts, antimony 0.5-2 parts, copper 0.3-1.2 parts, the copper needs to be pre-soaked in 10% dilute sulfuric acid for 5 minutes, the other materials are ultrasonically cleaned in acetone for 10 minutes, and then dried for standby, accurately weigh germanium 0.05-0.15 parts, gallium 0.1-0.5 parts, nickel 0.05-0.2 parts, phosphorus 0.01-0.08 parts, and rare earth cerium 0.005-0.03 parts, wherein the phosphorus is added in the form of red phosphorus powder, and the rare earth cerium needs to be ground to below 200 mesh;

[0044] S2. Put the pretreated tin, bismuth, indium, silver, antimony, and copper into a graphite crucible in order, vacuumize the furnace body to below 5×10 -3 Pa after closing the furnace body, fill high-purity argon to a pressure of 0.05-0.1 MPa in the furnace, turn on the induction heating, heat at a rate of 20-30℃ / min to 220-250℃, and keep the temperature constant for 30-40 minutes, while starting the mechanical stirrer to ensure uniform melting, real-time monitoring of the melt composition by an online spectrometer, and adjusting the heating power or stirring rate to compensate for the loss of volatilization.

[0045] S3. Reduce the melt temperature to 180-200℃, turn off the stirrer, evenly sprinkle the germanium, gallium, nickel, and phosphorus powders onto the surface of the melt through the glove box, control the feeding time to be 5-8 minutes, increase the temperature to 190-210℃, turn on the low-frequency electromagnetic stirring for 20-25 minutes to promote the diffusion of the micro-alloying elements and avoid segregation;

[0046] S4. Pour the ground rare earth cerium powder into the melt through the feeding pipe, maintain the temperature at 190-200℃, and let it stand for 10-15 minutes to allow the cerium element to adsorb impurities and float up. Use a ceramic filter screen to filter the melt twice to remove the dross and unmelted particles, and reduce the oxygen content of the melt to ≤50ppm;

[0047] S5. Preheat the mold to 80-120℃, spray a boron nitride coating on the surface to prevent alloy adhesion, and pour the melt into the mold through the flow guide at a flow rate of 1.5-2.0 L / min, with a pouring temperature controlled at 175-185℃ to avoid secondary oxidation. Start the water cooling system to cool the alloy to room temperature at a rate of 10-20℃ / s to inhibit the formation of coarse grains;

[0048] S6. Anneal the ingot in a vacuum annealing furnace at 120-150℃ for 2-3 hours to eliminate internal stress and improve ductility. Use cold rolling process to process the alloy to the target thickness to obtain a uniform microstructure;

[0049] S7. Use XRF to detect the alloy composition, with a deviation controlled within ±1% of the formula mass fraction range. Seal the qualified products in a nitrogen protective bag after quality inspection, store at a temperature ≤25℃ and humidity ≤30% RH.

[0050] It should be noted that the quality inspection in step S7 includes testing tensile strength, elongation, wetting angle, and high-temperature creep performance.

[0051] In this embodiment, a method for preparing a high-reliability low-melting-point tin-based alloy is provided, which comprises the following steps:

[0052] S1. Raw material pretreatment: weigh tin 60 parts, bismuth 12 parts, and ethanol ultrasonic cleaning (70℃, 12 minutes), and vacuum drying (90℃, 2.5 hours); weigh indium 5 parts, silver 2 parts, antimony 1 part, and copper 0.8 parts (copper pickling for 5 minutes), and dry after acetone ultrasonic cleaning; accurately weigh germanium 0.1 parts, gallium 0.3 parts, nickel 0.1 parts, phosphorus 0.05 parts (red phosphorus powder), and rare earth cerium 0.02 parts (ground to 200 mesh);

[0053] S2. Vacuum melting: After charging, vacuum extraction to 5x10-3Pa, argon filling to 0.08 MPa; induction heating to 235℃ (rate 25℃ / min), melting for 35 minutes, mechanical stirring (65 rpm); on-line spectrometer monitoring, adjusting volatile loss (tin loss 0.3%, indium loss 0.2%);

[0054] S3. Micro-alloying: cooling to 190℃, adding germanium, gallium, nickel, phosphorus powder (charging time 6 minutes); heating to 200℃, electromagnetic stirring (12 Hz, 0.8T) for 22 minutes;

[0055] S4. Rare earth treatment: adding rare earth cerium powder, standing for 12 minutes, ceramic filtering twice (oxygen content ≤45 ppm);

[0056] S5. Pouring cooling: mold preheating 100℃, boron nitride spraying (15 μm); pouring temperature 180℃, flow rate 1.8 L / min, water cooling rate 15℃ / s;

[0057] S6. Post-treatment: annealing at 135℃ for 2.5 hours; cold rolling to 0.3 mm (rate 0.8 m / min, reduction 12%);

[0058] Example 2: In this example, tin is 55 parts, bismuth is 15 parts, indium is 3 parts, silver is 1 part, antimony is 0.5 part, copper is 0.3 part, and other process parameters are the same as in Example 1.

[0059] Example 3: In this example, tin is 65 parts, bismuth is 10 parts, indium is 8 parts, silver is 3 parts, antimony is 2 parts, copper is 1.2 parts, and other process parameters are the same as in Example 1.

[0060] Example 4: In this example, tin is 58 parts, bismuth is 14 parts, indium is 6 parts, phosphorus is 0.03 parts, and other process parameters are the same as in Example 1.

[0061] Example 5: In this example, tin is 68 parts, bismuth is 10 parts, nickel is 0.08 parts, rare earth cerium is 0.025 parts, and other process parameters are the same as in Example 1.

[0062] The component parameters in Example 1 to Example 5 are shown in Table 1:

[0063] Table 1: Material composition table of examples

[0064] Component Example 1 Example 2 Example 3 Example 4 Example 5 Tin 60 55 65 58 68 Bismuth 12 15 10 14 10 Indium 5 3 8 6 4 Silver 2 1 3 2 1.5

[0065] Component Example 1 Example 2 Example 3 Example 4 Example 5 Antimony 1 0.5 2 1.2 0.8 Copper 0.8 0.3 1.2 0.5 1.0 Germanium 0.1 0.05 0.15 0.08 0.12 Gallium 0.3 0.1 0.5 0.2 0.4 Nickel 0.1 0.05 0.2 0.15 0.08 Phosphorus 0.05 0.01 0.08 0.03 0.06 Rare earth cerium 0.02 0.005 0.03 0.015 0.025

[0066] Comparative Example 1: In this comparative example, tin is 70 parts (upper limit of the interval), and other process parameters are the same as in Example 1.

[0067] Comparative Example 2: In this comparative example, the amount of tin was 50 parts (beyond the lower limit of the range), and other process parameters were the same as in Example 1;

[0068] Comparative Example 3: In this comparative example, bismuth was 8 parts (beyond the lower limit of the range), and other process parameters were the same as in Example 1;

[0069] Comparative Example 4: In this comparative example, indium was used in 2 parts (beyond the lower limit of the range), and other process parameters were the same as in Example 1;

[0070] Comparative Example 5: In this comparative example, the amount of silver was 0.2 parts (beyond the lower limit of the range), and other process parameters were the same as in Example 1;

[0071] The component parameters of Comparative Examples 1 to 5 are shown in Table 12:

[0072] Table 2: Comparative Example Material Composition Table

[0073] Component Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Tin 70 50 60 60 60 Bismuth 12 12 8 12 12 Indium 5 5 5 2 5 Silver 2 2 2 2 0.2 Antimony 1 1 1 1 1 Copper 0.8 0.8 0.8 0.8 0.8 Germanium 0.1 0.1 0.1 0.1 0.1 Gallium 0.3 0.3 0.3 0.3 0.3 Nickel 0.1 0.1 0.1 0.1 0.1 Phosphorus 0.05 0.05 0.05 0.05 0.05 Rare earth cerium 0.02 0.02 0.02 0.02 0.02

[0074] III. Performance Testing:

[0075] Tin-based alloy samples were prepared according to Examples 1-5 and Comparative Examples 1-5, and the performance of the samples was tested. The steps were as follows:

[0076] a. Tensile strength and elongation test:

[0077] Standard basis: ASTM E8 / E8M;

[0078] The alloy is cold-rolled into plates with a thickness of 0.5 to 1.0 mm and cut into standard dumbbell-shaped specimens (gauge length 25 mm, width 6 mm);

[0079] Parameter settings: Clamping speed: 1mm / min (elastic stage) → 5mm / min (plastic stage);

[0080] Temperature: 25±2℃ (room temperature);

[0081] a1. Clamp the sample and preload it to 5N to eliminate gaps;

[0082] a2. Start the testing machine and record the load-displacement curve until the specimen breaks;

[0083] Result determination: Tensile strength is taken as the peak value of the stress-strain curve;

[0084] The elongation rate needs to be tested three times and the average value should be taken, with a deviation of <5%;

[0085] b. Wetting angle test:

[0086] Standard based on: ISO 27448 (Wettability assessment);

[0087] b1. Substrate preparation: Selecting oxygen-free copper plate (10mm x 10mm x 1mm), ultrasonic cleaning with ethanol and nitrogen blowing dry;

[0088] b2. Alloy droplet formation: Cutting the alloy into 5mg small balls and placing them in the center of the copper plate; heating to the melting point of the alloy + 20℃ (142℃ alloy heated to 162℃), melting under argon protection;

[0089] b3. Image acquisition: After the droplet is stable, take the side profile by high-resolution camera (2000fps); use Young-Laplace equation to fit the droplet edge and calculate the wetting angle;

[0090] Result determination: Take the average value of the wetting angle of the droplet at 3 different positions, single point deviation <1°;

[0091] c. High temperature creep performance test:

[0092] Standard basis: ASTM E139 (creep test standard);

[0093] Sample preparation: Processed into cylindrical samples with a diameter of 5mm and a gauge length of 50mm, the surface is polished to Ra≤0.8μm;

[0094] Parameter setting: Test temperature: 100±1℃;

[0095] Loading stress: 30% of tensile strength (tensile strength 48MPa, then load 14.4MPa);

[0096] c1. After clamping the sample, heat it to the target temperature and keep it constant for 30 minutes;

[0097] c2. Apply constant load and record the displacement-time curve;

[0098] c3. Continue testing until the sample breaks or reaches the preset time (200h);

[0099] Result determination:

[0100] Creep rupture time: the total length from loading to rupture;

[0101] Steady-state creep rate: take the slope of the linear deformation stage;

[0102] Through the above standardized test process, the influence of different components on performance is clear, specifically:

[0103] Tensile strength: The content and distribution of strengthening phases (Ag3Sn, Cu6Sn5) dominate the strength;

[0104] Wetting angle: The lower the content of low surface tension elements (gallium, indium), the larger the wetting angle;

[0105] High temperature creep: the higher the proportion of grain boundary strengthening elements (rare earth cerium, nickel), the stronger the creep resistance.

[0106] The performance parameters of the samples prepared in Examples 1-5 are recorded in Table 3:

[0107] Table 3: Example performance data

[0108] Index Example 1 Example 2 Example 3 Example 4 Example 5 Melting point (°C) 142 138 148 140 145 Tensile strength (MPa) 48 42 51 46 47 Elongation (%) Wettability angle (°) 28 25 26 27 24 High temperature creep time (h) 23 25 24 22 26 Index 220 180 240 200 210

[0109] The performance parameters of the samples prepared in Examples 1-5 are recorded in Table 4:

[0110] Table 4: Comparative Example Performance Data

[0111] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Melting point (°C) Tensile strength (MPa) 155 130 135 145 150 Index 38 35 34 40 32

[0112] Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Elongation (%) Wettability angle (°) High temperature creep time (h) 18 20 19 15 16 ​ 35 28 30 38 40 ​ 120 100 90 110 85

[0113] Four, analysis conclusion:

[0114] According to the data in Tables 1-4, the tensile strength of the examples (42-51 MPa) is significantly higher than that of the comparative examples (32-40 MPa), the high temperature creep time of the examples (180-240 h) is better than that of the comparative examples (85-120 h), the wetting angle of the examples (22-26°) is lower than that of the comparative examples (28-40°), and the gallium and germanium optimize the surface tension;

[0115] In addition, in Example 1, tin (60 parts) and bismuth (12 parts) form a stable eutectic, indium (5 parts) and silver (2 parts) synergistically improve ductility and electrical conductivity, rare earth cerium (0.02 parts) and phosphorus (0.05 parts) refine the grain size, the tensile strength (48 MPa) and elongation (28%) reach the optimal balance, the melting temperature (235°C) and cooling rate (15°C / s) match the component characteristics, suppress segregation and porosity, and in combination with Table 3, the components of the examples achieve the best overall performance, therefore, Example 1 is the best embodiment of the present application.

[0116] In summary, by strictly limiting the component interval and process parameters, the present application achieves the synergistic optimization of low melting point, high reliability and environmental protection, and Example 1 is the preferred scheme due to the best matching of components and process.

[0117] In the description of the specification, reference to "one embodiment", "an example", "a specific example" or the like means that a particular feature, structure, material or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the application. The appearances of the phrases "in one embodiment", "an example", "a specific example" or the like in various places in the specification are not necessarily referring to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples.

[0118] The preferred embodiments of the application disclosed above are only to help explain the application. The preferred embodiments do not describe all the details of the application and limit the application to the specific embodiments described. Obviously, many modifications and variations can be made in light of the contents of the specification. The specification selects and specifically describes these embodiments in order to better explain the principles and practical application of the application, so that those skilled in the art can well understand and utilize the application. The application is limited only by the claims and their full scope and equivalents.

Claims

1. A high reliability low melting point tin based alloy comprising a base material, a strengthening material and a micro-alloying additive, characterized in that, The base material is composed of the following raw materials by weight: tin: 52-68 parts; bismuth: 10-15 parts; The reinforcing material is composed of the following raw materials by weight: indium: 3-8 parts; silver: 1-3 parts; antimony: 0.5-2 parts; copper: 0.3-1.2 parts; The micro-alloying additive is composed of the following raw materials by weight: germanium: 0.05-0.15 parts; gallium: 0.1-0.5 parts; nickel: 0.05-0.2 parts; phosphorus: 0.01-0.08 parts; rare earth cerium: 0.005-0.03 parts; The preparation method of the high-reliability low-melting-point tin-based alloy comprises the following steps: S1. The tin 52-68 parts and bismuth 10-15 parts are weighed according to the mass fraction interval, cleaned in ethanol at 60-80°C for 10-15 minutes using an ultrasonic cleaning machine to remove surface oxides and grease, and then dried in a vacuum drying oven at 80-100°C for 2-3 hours. Indium 3-8 parts, silver 1-3 parts, antimony 0.5-2 parts, and copper 0.3-1.2 parts are weighed, and the copper needs to be pre-soaked in 10% dilute sulfuric acid for 5 minutes for pickling. The other materials are ultrasonically cleaned in acetone for 10 minutes and dried for standby. Germanium 0.05-0.15 parts, gallium 0.1-0.5 parts, nickel 0.05-0.2 parts, phosphorus 0.01-0.08 parts, and rare earth cerium 0.005-0.03 parts are accurately weighed. The phosphorus is added in the form of red phosphorus powder, and the rare earth cerium needs to be ground to 200 mesh or less; S2. The pretreated tin, bismuth, indium, silver, antimony, copper is loaded into a graphite crucible in order, and after the furnace body is closed, vacuum is extracted to 5x10 -3 Pa, high-purity argon is filled to a furnace pressure of 0.05-0.1 MPa, induction heating is started, and the temperature is raised to 220-250°C at a rate of 20-30°C / min, and constant temperature melting is carried out for 30-40 minutes, while a mechanical stirrer is started to ensure uniformity of the melt, the melt composition is monitored in real time by an online spectrometer, and the heating power or stirring rate is adjusted to compensate for volatilization loss; S3. The melt temperature is reduced to 180-200°C, the stirrer is turned off, and the germanium, gallium, nickel, and phosphorus powders are uniformly scattered onto the surface of the melt through a glove box. The feeding time is controlled within 5-8 minutes. The temperature is raised to 190-210°C, and the low-frequency electromagnetic stirring is started for 20-25 minutes to promote the diffusion of micro-alloying elements and avoid segregation; S4. The ground rare earth cerium powder is poured into the melt through the feeding pipe, and the temperature is maintained at 190-200°C. After standing for 10-15 minutes, the cerium element adsorbs impurities and floats up. The melt is filtered twice using a ceramic filter screen to remove dross and un-melted particles, and the oxygen content of the melt is reduced to ≤50 ppm; S5. The mold is preheated to 80-120°C, and the surface is sprayed with boron nitride coating to prevent alloy adhesion. The melt is injected into the mold through a flow guide at a flow rate of 1.5-2.0 L / min. The pouring temperature is controlled at 175-185°C to avoid secondary oxidation. The water cooling system is started to cool the alloy to room temperature at a rate of 10-20°C / s to inhibit the formation of coarse grains; S6. The ingot is annealed in a vacuum annealing furnace at 120-150°C for 2-3 hours to eliminate internal stress and improve ductility. The alloy is processed to the target thickness using a cold rolling process to obtain a uniform microstructure; S7. The alloy composition is detected using XRF, and the deviation needs to be controlled within ±1% of the mass fraction interval. The qualified products after quality inspection are sealed in a nitrogen protection bag, and stored at a temperature ≤25°C and humidity ≤30% RH.

2. The high-reliability low-melting-point tin-based alloy according to claim 1, characterized by, The indium is prepared by electrolytic refining of crude indium in a 40-60°C sulfuric acid electrolyte at a current density of 100-200 A / m².

3. The high-reliability low-melting-point tin-based alloy according to claim 2, characterized by, The silver is prepared by precipitating silver powder from silver nitrate solution at 50-80℃ by chemical reduction method with glucose as reducing agent, drying after washing.

4. The high-reliability low-melting-point tin-based alloy according to claim 1, characterized by, The antimony is prepared by reducing antimony sulfide ore in coke at 600-800℃.

5. A high-reliability low-melting-point tin-based alloy according to claim 4, characterized in that, The copper is prepared by electrolytic refining of crude copper at 50-70℃ in electrolyte containing copper sulfate with cathode current density of 200-300A / m².

6. A high-reliability low-melting-point tin-based alloy according to claim 4, characterized by The germanium is prepared by reduction distillation of germanium tetrachloride gas at 1000-1200℃ in hydrogen atmosphere.

7. The high-reliability low-melting-point tin-based alloy according to claim 1, characterized by, The gallium is prepared by electrolytic oxidation purification of bauxite electrolyte at 30-50℃ with current efficiency ≥85%.

8. The high-reliability low-melting-point tin-based alloy according to claim 1, characterized by, The rare earth cerium is prepared by extraction separation of mixed rare earth oxides in acidic solution at 20-40℃ with P507 extractant.

9. A method for preparing a high-reliability, low-melting-point tin-based alloy as described in any one of claims 1 to 8, characterized in that, The method comprises the following steps: S1. Take tin 52-68 parts and bismuth 10-15 parts by mass fraction, clean the surface oxides and grease in ethanol at 60-80℃ for 10-15 minutes using an ultrasonic cleaner, then dry in a vacuum drying oven at 80-100℃ for 2-3 hours, respectively take indium 3-8 parts, silver 1-3 parts, antimony 0.5-2 parts, copper 0.3-1.2 parts, the copper needs to be soaked in 10% dilute sulfuric acid for 5 minutes, the other materials are cleaned by ultrasonic washing in acetone for 10 minutes, and then dried for standby, accurately weigh germanium 0.05-0.15 parts, gallium 0.1-0.5 parts, nickel 0.05-0.2 parts, phosphorus 0.01-0.08 parts, and rare earth cerium 0.005-0.03 parts, wherein the phosphorus is added in the form of red phosphorus powder, and the rare earth cerium needs to be ground to 200 mesh or less; S2. The pretreated tin, bismuth, indium, silver, antimony, copper is loaded into a graphite crucible in order, and after the furnace body is closed, vacuum is extracted to 5x10 -3 Pa, high-purity argon is filled to a furnace pressure of 0.05-0.1 MPa, induction heating is started, and the temperature is raised to 220-250°C at a rate of 20-30°C / min, and constant temperature melting is carried out for 30-40 minutes, while a mechanical stirrer is started to ensure uniformity of the melt, the melt composition is monitored in real time by an online spectrometer, and the heating power or stirring rate is adjusted to compensate for volatilization loss; S3. Reduce the melt temperature to 180-200℃, turn off the stirrer, and evenly sprinkle germanium, gallium, nickel, and phosphorus powder on the surface of the melt through a glove box, the feeding time is controlled within 5-8 minutes, the temperature is raised to 190-210℃, and the low-frequency electromagnetic stirring is started for 20-25 minutes to promote the diffusion of micro-alloying elements and avoid segregation; S4. Put the ground rare earth cerium powder into the melt through the feeding pipe, keep the temperature at 190-200℃, and stand for 10-15 minutes to make the cerium element adsorb impurities and float up, filter the melt twice with a ceramic filter screen to remove dross and un-melted particles, and reduce the oxygen content of the melt to ≤50ppm; S5. Preheat the mold to 80-120℃, spray boron nitride coating on the surface to prevent alloy adhesion, and pour the melt into the mold through the flow channel at a flow rate of 1.5-2.0L / min, the pouring temperature is controlled at 175-185℃ to avoid secondary oxidation, start the water cooling system to cool the alloy to room temperature at a rate of 10-20℃ / s to inhibit the formation of coarse grains; S6. Heat the ingot in a vacuum annealing furnace at 120-150℃ for 2-3 hours to eliminate internal stress and improve ductility, use cold rolling process to process the alloy to the target thickness to obtain uniform microstructure; S7. Use XRF to detect the alloy composition, the deviation needs to be controlled within ±1% of the mass fraction range, and the qualified products after quality inspection are sealed in a nitrogen protection bag, stored at a temperature of ≤25℃ and a humidity of ≤30%RH.

10. The method of claim 9, wherein the high-reliability low-melting-point tin-based alloy is prepared by the steps of: preparing a tin-based alloy by mixing a tin-based alloy powder with a fluxing agent; and performing a vacuum degassing process on the tin-based alloy prepared in the step of preparing a tin-based alloy. The quality inspection in the step S7 includes testing tensile strength, elongation, wetting angle and high temperature creep performance.