A high-strength high-thermal-stability lead-free solder alloy and a preparation method and use thereof

Abstract

The present application relates to the technical field of lead-free solder alloy component design and preparation, and particularly relates to a high-strength high-thermal-stability lead-free solder alloy and a preparation method and application thereof. The lead-free solder alloy comprises Ag, Cu, Sb, Bi, Ni, Ce, Ti and Sn elements, and the content of each element is 2.0-5.0% of Ag, 0.01-0.7% of Cu, 1.0-4.0% of Sb, 1.0-5.0% of Bi, 0.01-0.5% of Ni, 0.01-1.0% of Ce, 0.005-0.5% of Ti, and the rest is Sn; wherein the Ce or Ti element is one or more than one. The solder alloy belongs to a high-strength high-thermal-stability lead-free soft solder, and is particularly suitable for the connection and packaging of devices with high working temperature, high power and high reliability in high-power semiconductor application scenarios, and can be applied to the fields of automobile electronics, ships, energy, aerospace, etc.

Description

Technical Field

[0001] This invention relates to the field of lead-free solder alloy composition design and preparation technology, specifically to a high-strength, high-thermal-stability lead-free solder alloy, its preparation method, and its applications. Background Technology

[0002] The concept of new energy vehicles first appeared between the 1970s and 1990s, with some research institutions and automakers beginning to develop electric and hybrid vehicles. However, limited by factors such as battery technology and charging infrastructure, new energy vehicles were not widely adopted until recent years, when they entered a period of rapid development. Governments worldwide have successively introduced various incentive policies to promote the rapid development of the new energy vehicle industry chain, leading to a continuous increase in the market share of new energy vehicles. In my country, the related industry chain has become the largest growth point for exports. With the rapid rise of new energy vehicles and the increasing electrification of traditional fuel vehicles, higher requirements have been placed on the strength and thermal stability of automotive electronic solders.

[0003] Solder joints are the connections between electrical signals and mechanical links in electronic systems, playing a crucial role in electronic manufacturing and welding processes, directly affecting the performance, reliability, and safety of electronic equipment. Statistics show that over 60% of quality incidents and failures in electronic products during manufacturing and service life are due to solder joint aging, the root cause of which is defects in welding materials or processes. Under high-density manufacturing processes, the mechanical, electrical, and thermal loads borne by a single solder joint increase exponentially, placing new demands on the temperature resistance of welding materials, solder joint strength, structural stability, and process operability.

[0004] Driven by both the high-density packaging brought about by Moore's Law and the high strength and high thermal stability requirements of power semiconductors, the research and production of high-reliability solders have received widespread attention and investment abroad. As early as the 1990s, mainstream solder companies abroad, represented by Heraeus, Henkel, and Alpha, began research on high-reliability solders for automotive electronics and launched products represented by Inollot. Japanese companies such as Senju have also carried out research and development and market promotion of high-reliability alloys based on SnAgCu series solders. However, existing research and applications show that although existing high-reliability alloys have greatly improved in terms of strength and thermal stability compared to SAC solders, they still have small process windows, poor compatibility with some materials, and their strength and stability still need to be improved to meet the high-reliability requirements of new energy vehicles, power electronics, and other operating environments. Summary of the Invention

[0005] The purpose of this invention is to provide a high-strength, high-thermal-stability lead-free solder alloy, its preparation method, and its applications. This solder alloy belongs to the category of high-strength, high-temperature-operating-temperature lead-free soft solders. This alloy has better strength and thermal stability than the existing SnAgCuSbBiNi hexa-element alloy. It exhibits a low interfacial compound growth rate at temperatures ranging from room temperature to 175°C, demonstrating excellent reliability at high operating temperatures.

[0006] The technical solution of this invention is:

[0007] A high-strength, high-thermal-stability lead-free solder alloy, comprising Ag, Cu, Sb, Bi, Ni, Ce, Ti, and Sn elements, wherein their respective contents by weight percentage are: Ag 2.0–5.0%, Cu 0.01–0.7%, Sb 1.0–4.0%, Bi 1.0–5.0%, Ni 0.01–0.5%, Ce 0.01–1.0%, Ti 0.005–0.5%, with the balance being Sn; wherein Ce or Ti is one or more elements.

[0008] The high-strength, high-thermal-stability lead-free solder alloy also includes a trace amount of wetting balancer, which is one or more of Zn, Fe, Al, In, and Ba, and the total amount added is 0.001 to 0.02% by weight.

[0009] The high-strength, high-thermal-stability lead-free solder alloy preferably contains Ag 2.5–4.0%, Cu 0.03–0.6%, Sb 2.0–3.5%, Bi 2.0–4.0%, Ni 0.01–0.2%, Ce 0.01–0.5%, Ti 0.005–0.2%, a trace amount of wetting balancer 0.001–0.005%, and the balance being Sn.

[0010] The method for preparing the high-strength, high-thermal-stability lead-free solder alloy involves melting and mixing the elemental metals or intermediate alloys according to the alloy ratio, and then casting the mixture to obtain the lead-free solder alloy.

[0011] In the preparation method of the high-strength and high-thermal-stability lead-free solder alloy, Sn and Bi elements are introduced as metallic elements during smelting, and Ag, Cu, Sb, Ni, Ce, and Ti elements are introduced as Sn-Ag alloy, Sn-Cu alloy, Sn-Sb alloy, Sn-Ni alloy, Sn-Ce alloy, and Sn-Ti alloy, respectively.

[0012] The preparation method of the high-strength and high-thermal-stability lead-free solder alloy involves adding elemental metals Sn, Sn-Cu alloy, Sn-Ag alloy, elemental metals Bi, Sn-Sb alloy, Sn-Ni alloy, Sn-Ce alloy, and Sn-Ti alloy in sequence during smelting, and finally adding nanoparticles of wetting balancer.

[0013] The method for preparing the high-strength, high-thermal-stability lead-free solder alloy involves using a vacuum melting method, where the melting furnace is evacuated to a pressure of 4 × 10⁻⁶. -3 ~6×10 -3 Pa.

[0014] The method for preparing the high-strength, high-thermal-stability lead-free solder alloy involves melting and mixing the elemental metals or intermediate alloys at a temperature of 400–600°C, maintaining the temperature and stirring for 30–60 minutes, and then reducing the temperature to 300°C. During the melting process, the surface is covered with an anti-oxidation flux.

[0015] The high-strength, high-thermal-stability lead-free solder alloy is used as a solder for electronic devices operating under high-temperature and high-reliability conditions.

[0016] The advantages and beneficial effects of this invention are:

[0017] 1. For the SnAgCuSbBiNi hexa-element alloy system, this invention adds one or more of Ce and Ti elements in addition to a wetting balancer to improve the thermodynamic and mechanical properties of the alloy, enhance solder joint reliability, and obtain a high-strength, high-temperature-resistant lead-free solder alloy. This invention prepares a multi-component, high-reliability solder alloy through a wetting balancer and added elements. This alloy features good processability and can be used at relatively high ambient temperatures.

[0018] 2. The solder alloy of this invention is a high-strength, high-thermal-stability lead-free soft solder, which is particularly suitable for the connection and packaging of devices with high operating temperature, high power and high reliability requirements in high-power semiconductor application scenarios. It can be applied in automotive electronics, shipbuilding, energy, aerospace and other fields. Attached Figure Description

[0019] Figure 1 This is the differential thermal analysis (DSC) curve of the SBNC solder alloy. In the figure, the horizontal axis represents temperature (°C), and the vertical axis represents heat flow rate (mW / mg).

[0020] Figure 2 The morphology of intermetallic compounds (IMCs) at the interface of the SBNC and SAC305 solder joint after aging at 175℃ for 0h, 72h, 168h, 336h, and 672h is shown. (ae) represents SBNC; (fj) represents SAC305. Detailed Implementation

[0021] In its specific implementation, the first aspect of this invention provides a high-strength, high-thermal-stability lead-free solder alloy, which comprises the following elements by weight percentage:

[0022] Ag 2.0–5.0%, Cu 0.01–0.7%, Sb 1.0–4.0%, Bi 1.0–5.0%, Ni 0.01–0.5%, Ce 0.01–1.0%, Ti 0.005–0.5%, trace wetting balancer 0.001–0.02%, balance Sn.

[0023] Furthermore, the lead-free solder alloy also contains Ag and Cu elements. Adding Ag and Cu elements to the solder forms a soldering material based on the SnAgCu system, which has a relatively low melting point. Further, when the solder contains Ag and Cu elements, their respective contents by weight percentage are: Ag 2.0–5.0%, Cu 0.01–0.7%; preferably, Ag 2.5–4.0%, Cu 0.03–0.6%.

[0024] Furthermore, the lead-free solder alloy also contains Bi. The most significant effect of adding Bi to the solder is to lower the melting point of the alloy and increase wettability. In addition, the dispersed Bi element can also play a certain strengthening role. Further, when the solder contains Bi, its content, by weight percentage, is: Bi 1.0–5.0%; preferably, Bi 2.0–4.0%.

[0025] Furthermore, the lead-free solder alloy also contains Sb. Adding Sb to the solder lowers the alloy's melting point and strengthens the solder joint through solid solution reinforcement. More specifically, when the solder contains Sb, its content, by weight percentage, is: Sb 1.0–4.0%; preferably, Sb 2.0–3.5%.

[0026] Furthermore, the lead-free solder alloy also contains Ni. Adding Ni to the solder can improve the mechanical properties of the solder joint by forming intermetallic compounds with Sn and Cu, thus enhancing the solder joint's properties. Simultaneously, Ni can also form intermetallic compounds (IMCs) at the interface, improving the thermal stability of the solder joint by reducing the IMC growth rate. Further, when the lead-free solder alloy contains Ni, its content, by weight percentage, is: Ni 0.01–0.5%; preferably, Ni 0.01–0.2%.

[0027] Furthermore, the lead-free solder alloy also contains one or both of Ce and Ti elements. Adding Ce to the solder improves its high-temperature resistance, allowing it to maintain stability under high-temperature conditions and reducing the risk of oxidation and deterioration during soldering. Adding Ti to the alloy increases the solder's strength, giving the solder joint better mechanical properties. Further, when the solder contains Ce and Ti elements, their content, by weight percentage, is: Ce 0.01–1.0%, Ti 0.005–0.5%; preferably, Ce 0.01–0.5%, Ti 0.005–0.2%.

[0028] Furthermore, the lead-free solder alloy also contains trace amounts of a wetting balancer. Adding a wetting balancer to the solder allows for adjustments to the alloy's wetting properties, viscosity after melting, and flowability, depending on the type and quantity of the added elements, thereby reducing the difficulty of alloy melting and improving solderability. Furthermore, when the solder contains a wetting balancer, it may include, but is not limited to, nanoparticles such as Zn, Fe, Al, In, and Ba, with a total addition amount of 0.001–0.02% by weight, preferably 0.001–0.005%.

[0029] The second aspect of the present invention provides a method for preparing a multi-component high-reliability lead-free solder alloy, the specific technical route of which is as follows:

[0030] The above-mentioned method for preparing lead-free solder alloy includes the following steps:

[0031] The multi-component lead-free solder alloy is obtained by melting and mixing the elemental metals or intermediate alloys of each element according to a certain alloy ratio and then casting it; wherein:

[0032] During alloy smelting, Sn is introduced as a metallic element;

[0033] During alloy smelting, Bi is introduced as a metallic element;

[0034] During alloy smelting, Ag element is introduced as a Sn-Ag master alloy;

[0035] During alloy smelting, Cu element is introduced as a Sn-Cu master alloy;

[0036] During alloy smelting, Ni is introduced as a Sn-Ni master alloy;

[0037] During alloy smelting, Sb element is introduced as a Sn-Sb master alloy;

[0038] During alloy smelting, Ce element is introduced as a Sn-Ce master alloy;

[0039] During alloy smelting, Ti element is introduced as a Sn-Ti master alloy.

[0040] During smelting, the elemental metals Sn, Sn-Cu alloy, Sn-Ag alloy, elemental metal Bi, Sn-Sb alloy, Sn-Ni alloy, Sn-Ce alloy, and Sn-Ti alloy are added in sequence, along with a wetting balance agent.

[0041] Furthermore, the intermediate alloy is prepared by vacuum melting; wherein, the melting furnace is evacuated to a pressure of (4-6)×10⁻⁶. -3 Pa.

[0042] Furthermore, the melting temperature of the metallic elements or alloys is 400-600℃, and the mixture is kept at this temperature and stirred for 30-60 minutes, then cooled to 300℃; during the melting process, the surface is covered with an anti-oxidation flux.

[0043] Furthermore, the surface oxide residue is removed, and the mixture is poured into a mold to form a multi-component solder alloy ingot.

[0044] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited to the content described.

[0045] Example 1

[0046] In this embodiment, a lead-free solder alloy SnAgCuSbBiNiCe (SBNC) has the following composition by weight percentage: Ag 3.0%, Cu 0.5%, Sb 3.0%, Bi 3.2%, Ni 0.01%, Ce 0.05%, wetting balance agents are Zn, Al, and In with a content of 0.001% each, and the balance is Sn.

[0047] The preparation method of this lead-free solder alloy includes the following steps:

[0048] (1) Preparation of master alloy: Sn and Ag with a purity of 99.99 wt% were added to a medium-frequency induction melting furnace according to the required alloy ratio and melted. During melting, the vacuum was evacuated to a pressure of 5 × 10⁻⁶. -3 The Sn-Ag master alloy was prepared by heating to 1100℃ and holding for 1 hour, then cooling to 400℃ and pouring into a mold. The Sn-Cu master alloy was prepared by melting in a medium-frequency induction furnace at 1150℃ and holding for 1 hour, then cooling to 400℃ and pouring into a mold. The Sn-Sb master alloy was prepared by melting in a vacuum resistance furnace, with the vacuum level set to 4×10⁻⁶. -3 The smelting temperature was 660℃, with holding and stirring for 1 hour, and the casting temperature was 400℃. The Sn-Ni master alloy was smelted in a medium-frequency induction furnace, with a vacuum pressure of 5×10⁻⁶ during melting. -3Pa, heated to 1250℃ and held for 1 hour, then cooled to 400℃ and cast. The Sn-Ce master alloy was melted in a vacuum resistance furnace, with the vacuum leveled to 6×10⁻⁶. -3 Pa, smelting temperature is 1050℃, heat holding and stirring for 1 hour, casting temperature is 400℃.

[0049] (2) Preparation of SnAgCuSbBiNiCe solder alloy ingot: The elemental metals Sn, Bi and the intermediate alloys Sn-Ag, Sn-Cu, Sn-Sb, Sn-Ce and Sn-Ni obtained in step (1) are added to the melting furnace in the order of elemental metal Sn, intermediate alloy Sn-Ag, intermediate alloy Sn-Cu, elemental metal Bi, intermediate alloy Sn-Sb, intermediate alloy Sn-Ni and intermediate alloy Sn-Co according to the required alloy ratio. Wetting balance agents Zn, Al and In nano powders are added. During the melting process, rosin is covered on the surface. The temperature is raised to 400℃, kept warm and stirred for 40 min. Then the surface covering and oxide slag are removed, the temperature is lowered to 300℃, and the ingot is poured into a mold to prepare the SnAgCuSbBiNiCe solder alloy ingot.

[0050] (3) The smelted alloy was subjected to DSC testing, and the melting point was 210.16℃. The results are shown in [see attached table]. Figure 1 The alloy has a tensile strength of 57.4 MPa, which is more than 70% higher than that of SAC305.

[0051] (4) Sandwich-structured weld joints were prepared using the smelted alloy, and the weld joints were aged at 175℃ for 0h, 72h, 168h, 336h, and 672h. Using SAC305 as a reference group, samples with different aging times were mounted with resin, ground, polished, and then the weld joint microstructure was observed under a scanning electron microscope. Figure 2 As shown, the IMC morphology at the interface of the SnAgCuSbBiNiCe and SAC305 solder joints aged at 175℃ for 0h, 72h, 168h, 336h, and 672h shows that the interfacial compound layer of the SnAgCuSbBiNiCe alloy solder joint is thinner and relatively flatter than that of SAC305. By fitting the relationship between IMC thickness and time, it can be seen that the growth rate of IMC in the SnAgCuSbBiNiCe alloy solder is lower than that in SAC305, indicating better thermal stability.

[0052] The methods for preparing lead-free high-reliability solder in Examples 2 to 8 are the same as in Example 1, except that the weight ratios of each element are different. In step (1), the intermediate alloy melting steps are the same. In step (2), the corresponding proportions of Bi elemental alloy, Sn-Sb, Sn-Ce intermediate alloy, other components, and pure Sn are weighed and melted according to the final designed composition. Among them:

[0053] Example 2

[0054] In this embodiment, the weight percentage composition of the lead-free solder alloy is: Ag 5.0%, Cu 0.5%, Sb 2.0%, Bi 1.0%, Ni 0.1%, Ce 0.01%, with the balance being Sn. During the preparation of this lead-free solder alloy, the metallic elements or alloys of each element are melted and mixed at a melting temperature of 500°C, held at this temperature and stirred for 60 minutes. Afterwards, the surface coating and oxide slag are removed, the temperature is lowered to 300°C, and the mixture is poured into a mold to obtain a SnAgCuSbBiNiCe solder alloy ingot. This lead-free solder alloy has a melting temperature of 223.2°C and a tensile strength of 52.1 MPa.

[0055] Example 3

[0056] In this embodiment, the weight percentage composition of the lead-free solder alloy is: Ag 2.0%, Cu 0.7%, Sb 2.0%, Bi 4.0%, Ni 0.5%, Ce 0.5%, with the balance being Sn. During the preparation of this lead-free solder alloy, the metallic elements or alloys of each element are melted and mixed at a melting temperature of 400°C, held at this temperature and stirred for 50 minutes. Afterwards, the surface coating and oxide slag are removed, the temperature is lowered to 300°C, and the mixture is poured into a mold to obtain a SnAgCuSbBiNiCe solder alloy ingot. This lead-free solder alloy has a melting temperature of 216.4°C and a tensile strength of 47.1 MPa.

[0057] Example 4

[0058] In this embodiment, the lead-free solder alloy composition by weight percentage is: Ag 3.0%, Cu 0.5%, Sb 4.0%, Bi 2.8%, Ni 0.05%, Ce 0.01%, with the balance being Sn. During the preparation of this lead-free solder alloy, the metallic elements or alloys of each element are melted and mixed at a melting temperature of 600°C, held at this temperature and stirred for 40 minutes. Afterwards, the surface coating and oxide slag are removed, the temperature is lowered to 300°C, and the mixture is poured into a mold to prepare the SnAgCuSbBiNiCe solder alloy ingot. This lead-free solder alloy has a melting temperature of 219.1°C and a tensile strength of 52.3 MPa.

[0059] Example 5

[0060] In this embodiment, the lead-free solder alloy composition by weight percentage is: Ag 3.0%, Cu 0.5%, Sb 2.0%, Ni 0.05%, Bi 3.0%, Ce 0.03%, with the balance being Sn. During preparation, the metallic elements or alloys of each element are melted and mixed at a melting temperature of 400°C, held at this temperature and stirred for 40 minutes. Afterward, the surface coating and oxide slag are removed, the temperature is lowered to 300°C, and the mixture is poured into a mold to obtain the SnAgCuSbBiNiCe solder alloy ingot. This lead-free solder alloy has a melting temperature of 217.6°C and a tensile strength of 54.6 MPa.

[0061] Example 6

[0062] In this embodiment, the weight percentage of the lead-free solder alloy composition is as follows: The method for preparing lead-free high-reliability solder is the same as in Embodiment 1, except that Ti is added. The alloy, by weight percentage, contains Ag 3.0%, Cu 0.5%, Sb 2.0%, Bi 3.0%, Ni 0.05%, Ce 0.02%, Ti 0.005%, and wetting balance agents are Ba and In (added in nanoparticle form) with contents of 0.001% respectively, with the balance being Sn. In the preparation of this lead-free solder alloy, the intermediate alloy melting step in step (1) is the same, and the melting of Sn-Ti intermediate alloy is added in step (2): the Sn-Ti intermediate alloy and other components and pure Sn in the corresponding proportion are weighed and melted according to the final design composition. The Sn-Ti intermediate alloy is melted in a vacuum resistance furnace, and the vacuum is drawn to a pressure of 4×10 -3 A Sn-Ti master alloy was prepared by smelting at 1100℃, holding and stirring for 1 hour, and casting at 400℃. The metallic elements or alloys of each element were smelted and mixed at a melting temperature of 600℃, held and stirred for 60 minutes, then the surface coating and oxide slag were removed, and the mixture was cooled to 300℃ and poured into a mold to prepare a SnAgCuSbBiNiCeTi solder alloy ingot. This lead-free solder alloy had a melting temperature of 219.7℃ and a tensile strength of 71.2 MPa.

[0063] Example 7

[0064] In this embodiment, the weight percentage composition of the lead-free solder alloy is: Ag 3.0%, Cu 0.5%, Sb 2.0%, Bi 3.0%, Ni 0.05%, Ce 0.05%, Ti 0.01%, with the balance being Sn. During the preparation of this lead-free solder alloy, the metallic elements or alloys of each element are melted and mixed at a melting temperature of 600°C, held at this temperature and stirred for 60 minutes. Afterwards, the surface coating and oxide slag are removed, the temperature is lowered to 300°C, and the mixture is poured into a mold to prepare the SnAgCuSbBiNiCeTi solder alloy ingot. The melting temperature of this lead-free solder alloy is 221.3°C, and its tensile strength reaches 77.5 MPa.

[0065] Example 8

[0066] In this embodiment, the weight percentage composition of the lead-free solder alloy is: Ag 3.0%, Cu 0.5%, Sb 2.0%, Bi 3.0%, Ni 0.05%, Ce 0.05%, Ti 0.2%, with the balance being Sn. During the preparation of this lead-free solder alloy, the metallic elements or alloys of each element are melted and mixed at a melting temperature of 600°C, held at this temperature and stirred for 60 minutes. Afterwards, the surface coating and oxide slag are removed, the temperature is lowered to 300°C, and the mixture is poured into a mold to prepare the SnAgCuSbBiNiCeTi solder alloy ingot. The melting temperature of this lead-free solder alloy is 224.5°C, and its tensile strength reaches 65.3 MPa.

[0067] As can be seen from the above embodiments, the solder alloy of the present invention is a high-strength, high-thermal-stability lead-free solder, with a melting temperature of 210–225°C and a tensile strength of 45–80 MPa. It is particularly suitable for the connection and packaging of devices with high operating temperatures, high power, and high reliability requirements in high-power semiconductor applications, and can be applied in automotive electronics, marine engineering, power electronics, aerospace, and other fields.

Claims

1. A method for preparing a high-strength, high-thermal-stability lead-free solder alloy, characterized in that, The lead-free solder alloy composition by weight percentage is: Ag 3.0%, Cu 0.5%, Sb 2.0%, Bi 3.0%, Ni 0.05%, Ce 0.02%, Ti 0.005%, wetting balancer is Ba and In added in nano powder form with a content of 0.001% each, and the balance is Sn; The preparation method of this lead-free solder alloy includes the following steps: (1) Preparation of intermediate alloy: Sn and Ag with a purity of 99.99 wt% were added to a medium-frequency induction melting furnace according to the required alloy ratio and melted. During melting, the vacuum was evacuated to a pressure of 5 × 10⁻⁶. -3 The Sn-Ag master alloy was prepared by heating to 1100℃ and holding for 1 hour, then cooling to 400℃ and pouring into a mold; the Sn-Cu master alloy was prepared by melting in a medium-frequency induction furnace at 1150℃ and holding for 1 hour, then cooling to 400℃ and pouring into a mold; the Sn-Sb master alloy was prepared by melting in a vacuum resistance furnace, with the vacuum leveled to 4×10⁻⁶. -3 The smelting temperature was 660℃, with holding and stirring for 1 hour, and the casting temperature was 400℃. The Sn-Ni master alloy was smelted in a medium-frequency induction furnace, with a vacuum pressure of 5×10⁻⁶ during melting. -3 Pa, heated to 1250℃ and held for 1 hour, then cooled to 400℃ and cast; the Sn-Ce master alloy was melted in a vacuum resistance furnace, with the vacuum leveled to 6×10⁻⁶. -3 The smelting temperature was 1050℃, with holding and stirring for 1 hour, and the casting temperature was 400℃. The Sn-Ti master alloy was smelted in a vacuum resistance furnace, with the vacuum level set to 4×10⁻⁶. -3 Pa, smelting temperature is 1100℃, heat holding and stirring for 1 hour, casting temperature is 400℃; (2) Preparation of SnAgCuSbBiNiCeTi solder alloy ingot: The elemental metals Sn, Bi and the intermediate alloys Sn-Ag, Sn-Cu, Sn-Sb, Sn-Ni, Sn-Ce and Sn-Ti obtained in step (1) are added to the melting furnace in the order of elemental metal Sn, intermediate alloy Sn-Ag, intermediate alloy Sn-Cu, elemental metal Bi, intermediate alloy Sn-Sb, intermediate alloy Sn-Ni, intermediate alloy Sn-Ce and intermediate alloy Sn-Ti according to the required alloy ratio. Wetting balance agent Ba and In nano powder are added. Rosin is covered on the surface during the melting process. The melting temperature of the elemental metals or alloys is 600℃. The mixture is kept warm and stirred for 60 minutes. Then the surface covering and oxide slag are removed, the temperature is lowered to 300℃, and the mixture is poured into a mold to prepare the SnAgCuSbBiNiCeTi solder alloy ingot.

2. The use of a high-strength, high-thermal-stability lead-free solder alloy prepared by the method of claim 1 as a solder for electronic devices under high operating temperature and high reliability conditions.

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