Low-melting-point high-wettability quinary composite brazing filler metal as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of brazing filler metal, and particularly relates to low-melting-point and high-wettability quinary composite brazing filler metal and a preparation method and application, and the low-melting-point and high-wettability quinary composite brazing filler metal comprises Sn, Bi, In, Zn and Ag; the atomic ratio of Sn to Bi to In to Zn is 1: (0.5-1.5): (0.5-1.5): (0.1-0.3); ag is introduced into the SnBiInZn brazing filler metal, on one hand, strengthening structures such as # imgabs0 # are generated to play a role in strengthening, on the other hand, the situation that Zn is oxidized to form an oxidation film is reduced, the wettability of the brazing filler metal is improved, the brazing filler metal can be smoothly spread during welding, good electrical and mechanical connection is achieved, and the brazing filler metal has good mechanical properties such as ultimate tensile strength; meanwhile, low-temperature welding can be conducted at the temperature of # imgabs 1 #, and the brazing filler metal is excellent in performance; the technical problem that SnBiInZn brazing filler metal is poor in performance can be solved.

Description

Technical Field

[0001] This application belongs to the technical field of solders, and particularly relates to a five - element composite solder with low melting point and high wettability, a preparation method and an application thereof. Background Art

[0002] Traditional fusion welding melts the surfaces of the metal parts to be joined to form a molten pool, and after cooling and solidifying, a weld is formed to join the metal parts; after using a solder, the solder is heated to a certain temperature and melted, filled in the gap between the metal parts to be joined, and after cooling and solidifying, the two metal parts are welded together to achieve electrical and mechanical connections.

[0003] With the requirements in aspects such as environmental protection, human health, and industry development, lead - free solders such as Sn - 0.7Cu solder and Sn - 3.5Ag have been applied. However, the melting points of such lead - free solders are relatively high. For example, the melting point of Sn - 0.7Cu solder is , and the melting point of Sn - 3.5Ag solder is , both of which are above 200°C. This means that a relatively high soldering temperature is required during soldering. The high soldering temperature can damage heat - sensitive packaging materials and temperature - sensitive electronic components, which limits the further application of lead - free solders. In recent years, researchers have turned their attention to solders with lower melting points, such as , , - based solders. Such low - melting - point lead - free solders can be applied at lower soldering temperatures, reducing the thermal impact on the materials being soldered during the soldering process, reducing problems such as material deformation and performance degradation caused by high temperatures, avoiding thermal damage to sensitive electronic devices, minimizing soldering defects such as warping and open soldering generated during the production soldering process, reducing thermal stress, and thus obtaining a higher production qualification rate. In addition, the lower soldering temperature is conducive to reducing energy costs, reducing the requirements for heating equipment, meeting the requirements of sustainable development. The melting and solidification processes of low - melting - point solders are relatively fast, making it easy to control the soldering time and temperature, which makes the soldering process more stable. SnBiInZn - type low - melting - point lead - free solders have shown great application potential and value in the field of the electronics industry.

[0004] However, there is currently little research on SnBiInZn-based low-melting-point lead-free solders at home and abroad. The regulation of the Zn content in SnBiInZn solders remains a problem worthy of attention. This is because Zn has a strong binding ability with O. When the Zn-containing solder melts, Zn easily forms an oxide film on the surface of the solder. The oxide film will hinder the spreading of the solder, reduce the wettability of the solder, lower the solderability of the solder, hinder the good bonding between the solder and the substrate material, and is not conducive to achieving good mechanical and electrical connections. During welding, the use of protective gases such as argon can isolate the solder from the air and reduce the formation of the oxide film. However, this method increases the complexity of welding. Improving the solder itself can solve the problems caused by the oxide film from the source. Summary of the Invention

[0005] In view of this, the present application provides a five-element composite solder with low melting point and high wettability, its preparation method and application, which are used to solve the technical problem of poor performance of SnBiInZn solder.

[0006] The first aspect of the present application provides a five-element composite solder with low melting point and high wettability, which consists of Sn, Bi, In, Zn and Ag;

[0007] The atomic ratio of Sn, Bi, In and Zn is 1: 0.5-1.5: 0.5-1.5: 0.1-0.3.

[0008] Preferably, in the five-element composite solder with low melting point and high wettability, the mass ratio of the sum of the masses of Sn, Bi, In and Zn to Ag is 100: 0.5-10.

[0009] Preferably, in the five-element composite solder with low melting point and high wettability, the mass ratio of the sum of the masses of Sn, Bi, In and Zn to Ag is 100: 3-6.

[0010] The second aspect of the present application provides a preparation method of a five-element composite solder with low melting point and high wettability, which can prepare the five-element composite solder with low melting point and high wettability described in the first aspect. The preparation method includes the following steps:

[0011] Step S1: Add tin micro-particles, bismuth micro-particles, indium micro-particles, zinc micro-particles and silver micro-particles into molten molten salt to obtain five-element metal micro-particles covered with a molten molten salt layer;

[0012] Step S2: Smelt, cool and remelt and remove impurities from the five-element metal micro-particles covered with a molten molten salt layer to obtain a five-element composite solder.

[0013] Preferably, in step S1, the temperature of the molten molten salt is ;

[0014] A molten salt of KCl and a molten salt of LiCl with a mass ratio of 1 to 2.

[0015] Preferably, in step S1, the particle size of the tin particles is 50 to 70 microns;

[0016] The particle size of the bismuth micron particles is 50 to 70 microns;

[0017] The particle size of the indium micron particles is 50 to 70 microns;

[0018] The particle size of the zinc micron particles is 50 to 70 microns;

[0019] The particle size of the silver micron particles is 1 to 5 microns.

[0020] Preferably, in step S2, the smelting process includes: heating the molten salt containing the five - element metal at a heating rate of to

[0021] for smelting for 2 to 5 hours, stirring at intervals of 0.5 to 1 hour, to obtain a molten five - element composite solder.

[0022] Preferably, in step S2, the cooling process includes: pouring the molten five - element composite solder after smelting onto a stainless - steel plate for cooling to obtain a rough five - element composite solder product.

[0022] Preferably, in step S2, the remelting and impurity - removing process includes: remelting the rough five - element composite solder 1 to 5 times at for impurity removal to obtain a five - element composite solder.

[0023] The third aspect of the present application provides an application of the five - element composite solder with low melting point and high wettability described in the first aspect in the field of welding.

[0024] Preferably, the application specifically includes: heating the five - element composite solder with low melting point and high wettability described in the first aspect to for welding.

[0025] Compared with the prior art, the five - element composite solder with low melting point and high wettability provided by the present application has at least the following beneficial effects:

[0026] 1. For the five - element composite solder with low melting point and high wettability provided by the present application, by introducing Ag into the SnBiInZn solder, Ag can react with easily - oxidized Zn to form compounds such as AgZn3. On the one hand, it plays a strengthening role, and on the other hand, it reduces the occurrence of Zn oxidation to form an oxide film, improves the wettability of the solder, enables its smooth spreading during welding, and realizes good electrical and mechanical connections.

[0027] 2. The five - element composite solder with low melting point and high wettability provided by this application has improved the doping amount of introduced Ag. When the Ag doping amount is 3 - 6 wt%, it has good wettability and mechanical properties such as good ultimate tensile strength.

[0028] 3. The five - element composite solder with low melting point and high wettability provided by this application has a melting point around and can achieve soldering near . It is suitable for soldering heat - sensitive electronic components, expanding the application range of the solder to be tested. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following - described drawings are only some embodiments of this application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0030] Figure 1 It is the melting temperature result diagram of the solders provided in Examples 1 - 4 and Comparative Example 1 of this application;

[0031] Figure 2 It is the schematic diagram of the wetting angle and spreading rate test of the solders provided in Examples 1 - 4 and Comparative Example 1 of this application;

[0032] Figure 3 It is the test result diagram of the wetting angle and spreading rate of the solders provided in Examples 1 - 4 and Comparative Example 1 of this application;

[0033] Figure 4 It is the SEM image of the internal microstructure after soldering of the solders provided in Examples 1 - 4 and Comparative Example 1 of this application;

[0034] Figure 5 It is the SEM image of the intermetallic compound after soldering of the solders provided in Examples 1 - 4 and Comparative Example 1 of this application;

[0035] Figure 6 It is the schematic diagram of the non - standard tensile specimen made of the solders provided in Examples 1 - 4 and Comparative Example 1 of this application;

[0036] Figure 7 It is the test result diagram of the ultimate tensile strength and elongation of the non - standard tensile specimen made of the solders provided in Examples 1 - 4 and Comparative Example 1 of this application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] In order to make the invention purpose, features, and advantages of this application more obvious and understandable, the following will clearly and completely describe the technical solutions in the embodiments of this application with reference to the accompanying drawings in the embodiments of this application. Obviously, the embodiments described below are only a part of the embodiments of this application, rather than all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of this application.

[0038] In view of the fact that currently, SnBiInZn-based low-melting-point lead-free solders are prone to form oxide films during welding, resulting in performance defects such as poor wettability of SnBiInZn solders; this technical solution provides a five-element composite solder with a low melting point and high wettability. The composition of the five-element composite solder includes Bi, In, Zn, and Ag; among them, the atomic ratio of Sn, Bi, In, and Zn is 1:0.5~1.5:0.5~1.5:0.1~0.3.

[0039] The general formula of the five-element composite solder with a low melting point and high wettability provided by this application can be , where y = 0.5~1.5, z = 0.5~1.5, w = 0.1~0.3. Further preferably, y = 1, z = 1, w = 0.2; in this technical solution of this application, silver Ag is introduced into the SnBiInZn-based low-melting-point lead-free solder. The introduction of Ag in the solder can react with the easily oxidized element Zn to form compounds such as , on the one hand, this can be dispersed in the solder matrix, playing a role in heterogeneous nucleation, which is beneficial to the refinement of the microstructure and plays a strengthening role. On the other hand, it reduces the occurrence of Zn oxidation to form an oxide film. This makes the five-element composite solder provided by this technical solution of this application have good wettability, can spread well, and can be smoothly filled into the gap, and can form a good bond with the metal parts to be connected. The solder joint has high bonding strength, small contact resistance of the solder joint, and can maintain stable signal transmission after welding electronic components, realizing good electrical and mechanical connections, thereby overcoming the performance defects such as poor wettability of SnBiInZn solders and improving the performance of the solder.

[0040] Preferably, in the quinary composite solder provided by the technical solution of the present application, the doping amount of Ag can be 0.5-10 wt%, more preferably the Ag doping amount can be 1.5-6 wt%, and still more preferably the Ag doping amount can be 3-6 wt%; for example, after mixing Sn, Bi, In and Zn according to an atomic ratio of 1:1:1:0.2, and then doping 0.5-10 g of Ag into every 100 g of the mixed particles of Sn, Bi, In and Zn; however, when the Ag doping amount is 1.5 wt%, the mechanical properties such as the ultimate tensile strength of the solder decrease significantly, while when the Ag doping amount is 3 wt%, the mechanical properties such as the ultimate tensile strength of the solder are better, with a small wetting angle and a high spreading rate, and can form excellent electrical and mechanical connections for the metal components to be connected.

[0041] Correspondingly, the present application also provides a preparation method of the above quinary composite solder. The preparation method adopts a molten salt smelting method, which avoids the oxidation of raw materials such as Zn; the process of the molten salt smelting method is that after melting KCl and LiCl molten salts, Sn particles, Bi particles, In particles, Zn particles and Ag particles are added to the molten molten salts. Due to factors such as gravity and density, metal particles such as Sn particles will deposit on the lower layer of the molten molten salts, obtaining quinary metal micron particles covered with a molten salt layer on the surface, isolating oxygen for smelting, and after smelting, remelting can remove impurities such as molten salts to obtain the quinary composite solder.

[0042] Preferably, the present application also provides the application of the above quinary composite solder. Taking the copper plate commonly used in electronic components as an example in the application process; select the copper sheet as the substrate, place the above low-melting-point and high-wetting quinary composite solder and flux at the position where the copper sheet needs to be welded, and use a reflow soldering machine for reflow soldering. During the reflow soldering process, due to the low-melting-point and high-wetting quinary composite solder provided by the present application, the melting point is at about, and the reflow soldering temperature is usually higher than the melting point , so the reflow soldering temperature can be controlled at nearby; This temperature has little influence on the metal components to be welded, so the quinary composite solder provided by the present application is suitable for welding heat-sensitive electronic components and has a wide application range; when the doping amount of silver in the quinary composite solder is not high, for example, when 3 wt% of silver is doped, the reflow soldering temperature can be controlled at around 112-125 °C, and when the doping amount of silver in the quinary composite solder is not high, for example, when 6 wt% of silver is doped, the reflow soldering temperature can be controlled at nearby.

[0043] The following will specifically describe a low-melting-point and high-wetting quinary composite solder provided by the present application in combination with examples and experimental examples.

[0044] Example 1

[0045] This embodiment provides a preparation method of a five - element composite solder with low melting point and high wettability. The preparation method includes the steps of raw material preparation, adding raw materials into molten molten salt, and smelting.

[0046] The step of raw material preparation includes: weighing Sn particles (50 - 70 μm), Bi particles (50 - 70 μm), In particles (50 - 70 μm), and Zn particles (50 - 70 μm) according to the atomic ratio of 1:1:1:0.2, and then weighing Ag particles (1 - 5 μm) according to the mass ratio of the sum of the masses of Sn particles, Bi particles, In particles, and Zn particles to the mass of Ag being 100:1.5. That is, approximately 118.71 g of Sn particles, 208.98 g of Bi particles, 114.82 g of In particles, 13.08 g of Zn particles, and 6.83 g of Ag particles are weighed. Then, the Sn particles, Bi particles, In particles, Zn particles, and Ag particles are mechanically mixed for 1 hour to obtain mixed five - element metal micron particles.

[0047] The step of adding raw materials into molten molten salt: Weigh KCl and LiCl molten salts according to the mass ratio of 1.3:1, mix them evenly and pour them into a crucible, then put it into a KSL - 1400X type muffle furnace, and heat it from room temperature to After the molten salt melts into a liquid state, take it out, then pour the five - element metal micron particles into the molten salt and stir quickly so that the surface of the five - element metal micron particles in the crucible is covered with a molten molten salt layer.

[0048] The smelting step includes: placing the crucible in the muffle furnace and heating it at at a heating rate to Keep it warm for 3 h for smelting, and stir it once every 1 h. After smelting is completed, take out the crucible and pour the molten alloy onto a stainless - steel plate for rapid cooling. Then, remelt it 3 times at to remove molten salt impurities, obtaining a five - element composite solder with low melting point and high wettability. The doping amount of Ag is 1.5 wt%, named solder alloy.

[0049] Example 2

[0050] This embodiment provides a preparation method of a five - element composite solder with low melting point and high wettability. The difference between the preparation method and that of Example 1 is the adjustment of the doping amount of Ag particles. It includes the steps of raw material preparation, adding raw materials into molten molten salt, and smelting.

[0051] The steps of raw material preparation include: weighing Sn particles (50 - 70 μm), Bi particles (50 - 70 μm), In particles (50 - 70 μm), and Zn particles (50 - 70 μm) according to the atomic ratio of 1:1:1:0.2, and then weighing Ag particles (1 - 5 μm) according to the mass ratio of the sum of the masses of Sn particles, Bi particles, In particles, and Zn particles to the mass of Ag being 100:3; approximately 118.71 g of Sn particles, 208.98 g of Bi particles, 114.82 g of In particles, 13.08 g of Zn particles, and 13.67 g of Ag particles can be weighed. Then, the Sn particles, Bi particles, In particles, Zn particles, and Ag particles are mechanically mixed for 1 hour to obtain mixed five - element metal micron particles.

[0052] The step of adding raw materials to molten molten salt: Weigh KCl and LiCl molten salts according to the mass ratio of 1.3:1, mix them thoroughly and pour them into a crucible, then put it into a KSL - 1400X type muffle furnace, heat it from room temperature to 600 °C, take it out after the molten salt melts into a liquid state, and then pour the five - element metal micron particles into the molten salt and stir quickly to make the surface of the five - element metal micron particles in the crucible covered with a molten molten salt layer.

[0053] The steps of smelting include: placing the crucible in a muffle furnace and heating it at the heating rate to , holding for 3 h for smelting, and stirring once every 1 h; after smelting is completed, take out the crucible and pour the molten alloy onto a stainless steel plate for rapid cooling, and then remelt it 3 times to remove molten salt impurities, obtaining a low - melting - point and high - wettability five - element composite solder with the doping amount of Ag being 3 wt%, named solder alloy.

[0054] Example 3

[0055] This example provides a preparation method of a low - melting - point and high - wettability five - element composite solder. The difference between the preparation method and that of Example 1 lies in adjusting the doping amount of Ag particles, including the steps of raw material preparation, adding raw materials to molten molten salt, and smelting.

[0056] The steps of raw material preparation include: weighing Sn particles (50 - 70 μm), Bi particles (50 - 70 μm), In particles (50 - 70 μm), and Zn particles (50 - 70 μm) in an atomic ratio of 1:1:1:0.2, and then weighing Ag particles (1 - 5 μm) according to the ratio that the sum of the masses of Sn particles, Bi particles, In particles, and Zn particles to the mass of Ag is 100:4.5; approximately 118.71 g of Sn particles, 208.98 g of Bi particles, 114.82 g of In particles, 13.08 g of Zn particles, and 20.50 g of Ag particles can be weighed. Then, the Sn particles, Bi particles, In particles, Zn particles, and Ag particles are mechanically mixed for 1 hour to obtain mixed five - element metal micron particles.

[0057] The step of adding raw materials into the molten molten salt: Weigh KCl and LiCl molten salts according to a mass ratio of 1.3:1, mix them evenly and pour them into a crucible, then place it in a KSL - 1400X type muffle furnace and heat it from room temperature to , take it out after the molten salt melts into a liquid state, then pour the five - element metal micron particles into the molten salt and stir quickly so that the surface of the five - element metal micron particles in the crucible is covered with a molten molten salt layer.

[0058] The steps of smelting include: Place the crucible in the muffle furnace and heat it at a heating rate to , keep it warm for 3 h for smelting, and stir it once every 1 h; After smelting is completed, take out the crucible and pour the molten alloy onto a stainless steel plate for rapid cooling, and then remelt it 3 times at to remove molten salt impurities, obtaining a low - melting - point and high - wettability five - element composite solder. The doping amount of Ag is 4.5 wt%, named solder alloy.

[0059] Example 4

[0060] This example provides a preparation method of a low - melting - point and high - wettability five - element composite solder. The difference between the preparation method and that of Example 1 is the adjustment of the doping amount of Ag particles, including the steps of raw material preparation, adding raw materials into the molten molten salt, and smelting.

[0061] The steps of raw material preparation include: weighing Sn particles (50 - 70 μm), Bi particles (50 - 70 μm), In particles (50 - 70 μm), and Zn particles (50 - 70 μm) according to the atomic ratio of 1:1:1:0.2, and then weighing Ag particles (1 - 5 μm) according to the mass ratio of the sum of the masses of Sn particles, Bi particles, In particles, and Zn particles to the mass of Ag being 100:6; approximately 118.71 g of Sn particles, 208.98 g of Bi particles, 114.82 g of In particles, 13.08 g of Zn particles, and 27.34 g of Ag particles can be weighed. Then, the Sn particles, Bi particles, In particles, Zn particles, and Ag particles are mechanically mixed for 1 hour to obtain mixed five - element metal micron particles.

[0062] The step of adding raw materials to molten molten salt: Weigh KCl and LiCl molten salts according to the mass ratio of 1.3:1, fully mix them evenly and pour them into a crucible, then put it into a KSL - 1400X type muffle furnace and heat it from room temperature to , take it out after the molten salt melts into a liquid state, then pour the five - element metal micron particles into the molten salt and stir quickly so that the surface of the five - element metal micron particles in the crucible is covered with a molten molten salt layer.

[0063] The steps of smelting include: placing the crucible in a muffle furnace and heating it at a heating rate to , keeping it warm for 3 h for smelting and stirring once every 1 h; after smelting is completed, take out the crucible and pour the molten alloy on a stainless steel plate for rapid cooling, and then remelt it three times to remove molten salt impurities to obtain a low - melting - point and high - wettability five - element composite solder. The doping amount of Ag is 6 wt%, named solder alloy.

[0064] Comparative Example 1

[0065] This comparative example provides a preparation method of a composite solder, including the steps of raw material preparation, adding raw materials to molten molten salt, and smelting.

[0066] The steps of raw material preparation include: weighing Sn particles (50 - 70 μm), Bi particles (50 - 70 μm), In particles (50 - 70 μm), and Zn particles (50 - 70 μm) according to the atomic ratio of 1:1:1:0.2; approximately 118.71 g of Sn particles, 208.98 g of Bi particles, 114.82 g of In particles, and 13.08 g of Zn particles can be weighed. Then, the Sn particles, Bi particles, In particles, and Zn particles are mechanically mixed for 1 hour to obtain mixed metal micron particles.

[0067] The steps of adding raw materials to molten molten salt are as follows: Weigh KCl and LiCl molten salts according to a mass ratio of 1.3:1, pour them into a crucible after fully mixing and homogenizing, then place the crucible in a KSL-1400X type muffle furnace, heat it from room temperature to 600 °C, take it out after the molten salt melts into a liquid state, and then pour the metal micron particles into the molten salt and stir quickly to make the surface of the metal micron particles in the crucible covered with a molten molten salt layer.

[0068] The steps of smelting include: placing the crucible in a muffle furnace and heating it at a heating rate of to , holding for 3 h for smelting, and stirring once every 1 h; after smelting is completed, take out the crucible and pour the molten alloy on a stainless steel plate for rapid cooling, and then remelt it times at

[0069] Experimental Example 1

[0070] In this experimental example, the solders provided in Examples 1-4 and Comparative Example 1 were subjected to performance tests. The performance tests included melting temperature tests, wetting angle and spreading rate tests, internal microstructure and intermetallic compound tests, and ultimate tensile strength and elongation tests.

[0071] Among them, the process of the melting temperature test included: using a TA DSC25 type differential scanning calorimeter (DSC) to determine the melting characteristics of the solders provided in Examples 1-4 and Comparative Example 1. Take 5-10 mg of the solder alloy and test it in a nitrogen atmosphere. The test temperature range is , and the heating rate is .

[0072] From Figure 1 the test results shown, it can be seen that the melting temperatures of the solders provided in Examples 1-4 and Comparative Example 1 of the present application are not very different, both around , indicating that the solders provided in Examples 1-4 of the present application can meet the requirements of low-temperature welding, and the welding temperature can be controlled around .

[0073] The process of the wetting angle and spreading rate test included: using a copper sheet with a size of as the substrate, grinding it with SiC sandpaper to 2000 mesh, cleaning and drying it with anhydrous ethanol for standby, then weighing about 0.23 mg of the solders provided in Examples 1-4 and Comparative Example 1 and an appropriate amount of flux (Shanghai Jinji solder paste) and putting them into a crucible and heating on a D15 environmental protection constant temperature platform. With the action of tension, it automatically aggregates into a spherical shape, and after solidification, take it out and measure the diameter D. The wetting angle and spreading rate of the solder are tested as Figures 2 - 3as shown; and placed together with the soldering flux in the center of the copper sheet, and then put it into a PuHui T-962 type reflow soldering machine for reflow soldering, with the highest temperature being , the heating time being 5 min, to obtain solder joints. The internal microstructure of the solder joints after soldering and the SEM images of the intermetallic compounds are as shown in Figures 4 - 5 .

[0074] From Figures 2 - 5 , it can be seen that compared with the solder provided in Comparative Example 1, the solders provided in Examples 1-4 of the present invention can reduce the wetting angle of the zinc-containing solder to , and improve the spreading rate. This shows that the solders provided in Examples 1-4 of the present invention can react with the easily oxidized element Zn by introducing Ag to form compounds such as . On the one hand, it plays a strengthening role, and on the other hand, it reduces the occurrence of Zn oxidation to form an oxide film, improves the wettability of the solder, enables it to spread smoothly during soldering, and realizes good electrical and mechanical connections.

[0075] The process of testing the ultimate tensile strength and elongation includes: melting the solders provided in Examples 1-4 and Comparative Example 1 at into a liquid state, pouring them into a specific mold, cooling and forming, and then taking out the non-standard tensile specimens with the dimensions as shown in Figure 6 . Use SiC sandpaper to polish the surface of the specimens to 2000# to reduce stress concentration, and use an MTS Exceed E44 type electronic universal testing machine to stretch at room temperature, with a stretching rate of 1 mm / min. To reduce errors, three specimens are taken for each group of tests and their average values are calculated.

[0076] The test results are as shown in Figure 7 . Compared with the solder provided in Comparative Example 1, the solders provided in Examples 1-4 of the present invention can also reach an ultimate tensile strength of 50.13 MPa and an elongation of 36.15% after introducing silver, which can meet most application occasions; further combining the test results of the wetting angle and spreading rate, ultimate tensile strength and elongation shown in Figure 3 , 7 , it can be seen that when the doping amount of silver in the solders provided in Examples 1-4 of the present invention is 3-6 wt%, the wetting performance is excellent, and the mechanical properties such as the ultimate tensile strength remain good.

[0077] The above-described embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A low melting point and high wettability five-element composite solder, characterized in that: The composition includes Sn, Bi, In, Zn and Ag; The atomic ratio of Sn, Bi, In and Zn is 1:0.5~1.5:0.5~1.5:0.1~0.

3.

2. A low melting point and high wettability five-element composite solder according to claim 1, characterized in that: In the low-melting-point and high-wetting five-element composite solder, the mass ratio of the sum of the masses of Sn, Bi, In and Zn to Ag is 100:0.5-10.

3. A method for preparing a low melting point and high wettability five-component composite solder according to any one of claims 1 to 2, characterized in that: The following steps are involved: Step S1, adding tin micron particles, bismuth micron particles, indium micron particles, zinc micron particles and silver micron particles into molten salt to obtain five-element metal micron particles with a molten salt layer covering the surface; Step S2, smelting, cooling, remelting and removing impurities of the five-element metal micron particles whose surfaces are covered with a molten salt layer to obtain a five-element composite solder.

4. The method for preparing a low melting point and high wettability five-component composite solder according to claim 3, characterized in that: In step S1, the particle size of the tin micron particles is 50-70 microns; The particle size of the bismuth micron particles is 50 to 70 microns; The particle size of the indium micron particles is 50 to 70 microns; The particle size of the zinc micron particles is 50 to 70 microns; The particle size of the silver micron particles is 1 to 5 microns.

5. A method for preparing a low melting point and high wettability five-component composite solder according to claim 3, It is characterized in that In step S1, the temperature of the molten salt is , the composition is KCl molten salt and LiCl molten salt in a mass ratio of 1~2:

1.

6. The method for preparing a low melting point and high wettability five-component composite solder according to claim 3, characterized in that: In step S2, the smelting process includes: melting the molten salt containing the five element metals with Heating rate to The smelting is performed for 2 to 5 hours with stirring at intervals of 0.5 to 1 hour to obtain a molten five-element composite solder.

7. The method for preparing a low melting point and high wettability five-component composite solder according to claim 3, characterized in that: In step S2, the cooling process includes: pouring the molten five-component composite solder onto a stainless steel plate and cooling it to obtain a crude five-component composite solder.

8. The method for preparing a low melting point and high wettability five-component composite solder according to claim 3, characterized in that: In step S2, the remelting and impurity removal process includes: remelting the crude five-component composite solder material at 80-200° C. for 1-5 times to remove impurities, thereby obtaining the five-component composite solder material.

9. Application of the low melting point and high wettability five-component composite solder according to any one of claims 1 to 2 in the field of welding.

10. The use according to claim 9, characterized in that: The application specifically comprises: heating a low melting point and high wettability five-element composite solder according to any one of claims 1 to 2 to Perform welding.

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