A rare earth strengthened anti-electric couple corrosion SAC alloy and a preparation method and application thereof

Abstract

This invention discloses a rare-earth-reinforced SAC alloy resistant to galvanic corrosion, its preparation method, and its applications, belonging to the field of metal matrix composites. This invention utilizes low-boiling-point solvents and straight-chain fatty acids to hydrophobically modify rare-earth oxide nanoparticles; under inert gas protection, the modified powder is added to a molten SAC alloy, followed by ultrasonic dispersion and rapid solidification via water atomization to obtain alloy powder; finally, low-temperature aging treatment is performed. This invention inhibits nanoparticle agglomeration through surface modification, and refines grains through rapid solidification and aging processes, transforming the interfacial IMC layer from a thick and brittle state to a thin and dense continuous layer. Experimental results show that the potential difference between the obtained alloy Sn matrix and the IMC layer is as low as 0.005~0.04 V, significantly enhancing its resistance to galvanic corrosion; the shear strength of the solder joint is increased by more than 28% compared to the unmodified sample, and the fracture mode changes to matrix ductile fracture; the wetting angle is reduced by more than 30%, and the spreadability is excellent. This alloy is suitable for high-end electronic packaging in high-temperature, high-humidity, and high-salt-spray environments.

Description

Technical Field

[0001] This invention belongs to the field of metal matrix composite material preparation technology, specifically relating to a rare earth-reinforced anti-galvanic corrosion SAC alloy, its preparation method, and its application. Background Technology

[0002] In the field of electronic packaging, SAC (Sn-Ag-Cu) tin-silver-copper alloy, as an environmentally friendly alternative to traditional lead-based solder, has been widely used. However, its electrochemical corrosion defects have become a key issue restricting the long-term reliability of electronic devices, and research on the electrochemical corrosion resistance of SAC alloys has therefore attracted much attention. The electrochemical corrosion of SAC alloys is a complex process affected by multiple factors. Its microstructure consists of a β-Sn matrix and intermetallic compound (IMC) particles such as Ag3Sn and Cu6Sn5. The potential difference between different phases easily forms a micro-galvanic cell, which makes the Sn phase, as the anode, preferentially corroded, while the IMC particles, as the cathode, accelerate the electrochemical reaction. Moreover, the coarse and unevenly distributed IMC particles further increase the corrosion rate. At the same time, corrosive media such as humid air and chloride ions, as well as residual halogen-containing flux that is not completely removed after soldering, can also damage the passivation film on the alloy surface, aggravate pitting and electrochemical corrosion, and ultimately lead to solder joint failure.

[0003] However, existing material modification and performance optimization technologies still have many limitations. Regarding the electrochemical corrosion problem of SAC alloys, current improvement methods focus on alloy composition optimization, microstructure control, and surface protection, but they have not fundamentally solved core problems such as the formation of micro-galvanic cells, uneven IMC phase control, and easy intrusion of corrosive media. Therefore, they still cannot meet the long-term corrosion resistance requirements of electronic devices under complex operating conditions. Summary of the Invention

[0004] The purpose of this invention is to provide a rare earth-reinforced SAC alloy resistant to galvanic corrosion, its preparation method, and its application.

[0005] This invention provides a method for preparing a rare-earth-reinforced SAC alloy resistant to galvanic corrosion, characterized by comprising the following steps: S1. Rare earth oxide nanopowder is mixed with a volatile organic solvent and C12~C20 straight-chain fatty acids to obtain a premix. The premix is ​​subjected to solid-liquid separation and solvent removal to obtain surface-modified rare earth oxide nanoparticles. The boiling point of the volatile organic solvent is 50℃~115℃. S2. Melt tin-silver-copper alloy powder under a protective atmosphere to obtain Sn-based melt; S3. The surface-modified rare earth oxide nanoparticles are added to the Sn-based melt for dispersion and compounding to obtain a rare earth-tin-silver-copper alloy mixture. The rare earth-tin-silver-copper alloy mixture is then subjected to atomization and rapid solidification treatment to obtain a Sn-based alloy billet. The amount of surface-modified rare earth oxide nanoparticles added is 0.05~0.10 wt%. S4 and Sn-based alloy billets were subjected to low-temperature artificial aging treatment in a protective atmosphere to obtain rare earth-reinforced SAC alloys resistant to galvanic corrosion.

[0006] Preferably, the C12~C20 straight-chain fatty acids in step S1 are one or more of lauric acid, myristic acid, palmitic acid, stearic acid, and arachidic acid; and the volatile organic solvent is one or more of ethanol, isopropanol, and isobutanol.

[0007] Preferably, the rare earth oxide nanopowder in step S1 is one or a combination of Y2O3 nanopowder and CeO2 nanopowder; when the rare earth oxide nanopowder is a combination of Y2O3 nanopowder and CeO2 nanopowder, the mass ratio of Y2O3 nanopowder to CeO2 nanopowder is 1~3:1.

[0008] Preferably, the mass ratio of the volatile organic solvent, C12~C20 straight-chain fatty acid and rare earth oxide nanopowder in step S1 is 5~10:1~3:1.

[0009] Preferably, the protective atmosphere in steps S2 and S4 is selected from inert gas, reducing gas or a mixture thereof.

[0010] Preferably, in step S3, the dispersion and compounding method is ultrasonic vibration dispersion; the frequency of the ultrasonic vibration is 20~40 kHz, and the power density is 0.5~1.5 W / cm². 2 The duration of ultrasonic vibration is 10-20 minutes.

[0011] Preferably, the rapid solidification treatment in step S3 is water atomization; the cooling rate of the water atomization is not less than 102℃ / s, the atomization pressure is 2~5 MPa, and the atomization medium is deionized water.

[0012] This invention also provides a method for preparing a rare-earth-reinforced SAC alloy resistant to galvanic corrosion, the method further comprising: S5. The rare earth-reinforced anti-galvanic corrosion SAC alloy is cold-pressed and then hot-pressed or hot-extruded at 200~240℃ to obtain rare earth-reinforced anti-galvanic corrosion SAC alloy block.

[0013] The present invention also provides a rare earth-reinforced SAC alloy resistant to galvanic corrosion, which is prepared by the preparation method described in the above technical solution.

[0014] The present invention also provides the application of rare earth-reinforced anti-galvanic corrosion SAC alloy or rare earth-reinforced anti-galvanic corrosion SAC alloy prepared by the preparation method described above in the field of electronic packaging solder; the alloy can be made into solder wire or solder sheet alone, or mixed with flux to make solder paste.

[0015] This invention provides a rare-earth-reinforced anti-galvanic corrosion SAC alloy and its preparation method. Through a synergistic process of hydrophobic modification of nanoparticle surfaces, ultrasonic melt dispersion, and low-temperature artificial aging, the problem of easy agglomeration of nano-oxides in tin-based melts is effectively solved. The modified rare-earth oxide nanoparticles can be uniformly dispersed in the grain boundaries and matrix, pinning the grain boundaries and refining the grains. Simultaneously, low-temperature artificial aging further promotes atomic diffusion at the nanoparticle-matrix interface, forming a thin, dense, continuous, and uniform intermetallic compound (IMC) layer, eliminating the micro-cell effect caused by thick, brittle layered IMCs. Electrochemical testing shows that the potential difference between the Sn matrix and the Cu6Sn5 IMC layer in the alloy solder joints of this invention is as low as 0.005~0.04 V, far lower than the 0.09~0.14 V of traditional unmodified alloys. This significant reduction in potential difference indicates a substantial weakening of the driving force for galvanic corrosion. In a high-salt-spray, high-temperature, and high-humidity simulation experiment involving immersion in a 3.5wt% NaCl solution for 72 h, the alloy surface of this invention exhibited only slight uniform corrosion without pitting, while the standard sample showed severe pitting and interface cracking. The corrosion resistance was significantly improved, making it fully adaptable to harsh working conditions such as high temperature, high humidity, and high salt spray.

[0016] Furthermore, due to the dispersion strengthening effect of nanoparticles and the optimization of the IMC layer morphology, the mechanical properties of the alloy of this invention achieve a qualitative leap, with the solder joint shear strength increasing by 28.7% to 34.6% compared to the unmodified alloy. Tensile / shear test fracture analysis shows that traditional alloys often experience brittle fracture along the IMC layer interface, posing a serious safety hazard. However, the fracture mode of the alloy of this invention is transformed into matrix ductile fracture, completely eliminating the risk of weak interfacial areas acting as crack sources, and significantly improving the reliability and impact resistance of electronic packaging structures. Moreover, the alloy powder and derived solder prepared by this invention exhibit excellent wetting and spreading properties. Droplet testing shows that the wetting angle of the alloy of this invention on Cu substrates is reduced to 30.8 to 33.4°, more than 30% lower than that of ordinary SAC alloys. The low wetting angle allows the solder to spread rapidly and uniformly during reflow soldering, without balling or burrs, forming full and reliable solder joints. This is particularly suitable for high-end microelectronic packaging with extremely small pin pitches, improving production yield.

[0017] Furthermore, the stearic acid surface modification process used in this invention is simple and inexpensive; the smelting process only requires a conventional vacuum induction furnace in conjunction with an ultrasonic vibration device; and the low-temperature artificial aging process has low energy consumption and requires no complex equipment. The entire process is highly compatible with existing lead-free solder production lines, and can achieve large-scale production without large-scale equipment modifications, thus possessing extremely high economic benefits and promotional value. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 Comparison of SEM microstructures of SAC alloys under different rare earth strengthening phase addition conditions; Wherein: (a) is standard SAC305; (b) is standard SAC387; (c) is standard SAC0307; (d) is SAC305 + 0.05wt% Y2O3 nanopowder; (e) is SAC387 + 0.10wt% CeO2 nanopowder; (f) is SAC0307 + 0.05wt% Y2O3 + CeO2 composite nanopowder. Detailed Implementation

[0020] This invention provides a method for preparing a rare-earth-reinforced SAC alloy resistant to galvanic corrosion, comprising the following steps: S1. Rare earth oxide nanopowder is mixed with a volatile organic solvent and C12~C20 straight-chain fatty acids to obtain a premix. The premix is ​​subjected to solid-liquid separation and solvent removal to obtain surface-modified rare earth oxide nanoparticles. The boiling point of the volatile organic solvent is 50℃~115℃. S2. Melt the tin-silver-copper alloy powder under a protective atmosphere to obtain a Sn-based melt; the tin-silver-copper alloy powder is one of SAC305, SAC0307, ​​and SAC387 alloy powders. S3. The surface-modified rare earth oxide nanoparticles are added to the Sn-based melt for dispersion and compounding to obtain a rare earth-tin-silver-copper alloy mixture. The rare earth-tin-silver-copper alloy mixture is then subjected to atomization and rapid solidification treatment to obtain a Sn-based alloy billet. The amount of surface-modified rare earth oxide nanoparticles added is 0.05~0.10 wt%. S4 and Sn-based alloy billets were subjected to low-temperature artificial aging treatment in a protective atmosphere to obtain rare earth-reinforced SAC alloys resistant to galvanic corrosion.

[0021] Unless otherwise specified, all raw materials used in this invention are commercially available products well known in the art.

[0022] This invention, through surface modification treatment in step S1, can effectively improve the dispersibility of rare earth oxide nanoparticles, prevent their agglomeration in Sn-based melt, and enhance the compatibility between rare earth oxides and Sn-based melt, laying the foundation for subsequent composite dispersion; Step S2 uses protective atmosphere melting, which can effectively suppress the oxidation and burn-off of tin-silver-copper alloy powder and ensure the compositional uniformity of Sn-based melt; Step S3, the synergistic effect of dispersion composite and atomization rapid solidification, can uniformly disperse rare earth oxide nanoparticles in the alloy matrix and refine the alloy grains; Step S4, low-temperature artificial aging treatment, can further optimize the alloy microstructure, improve the alloy's resistance to galvanic corrosion and mechanical properties, and finally obtain a rare earth-reinforced galvanic corrosion resistant SAC alloy with excellent comprehensive performance.

[0023] This invention involves mixing rare earth oxide nanopowder with a volatile organic solvent and C12-C20 straight-chain fatty acids to obtain a premix. The premix is ​​then subjected to solid-liquid separation and solvent removal to obtain surface-modified rare earth oxide nanoparticles. In this invention, the rare earth oxide nanopowder in step S1 is one or a mixture of Y2O3 nanopowder and CeO2 nanopowder. When the rare earth oxide nanopowder is a mixture of Y2O3 nanopowder and CeO2 nanopowder, the mass ratio of Y2O3 nanopowder to CeO2 nanopowder is 1-3:1, preferably 2:1. In this invention, the average particle size of the rare earth oxide nanopowder is preferably 25-30 nm, and the purity is ≥99.9%. This invention selects Y2O3 and CeO2 nanopowder as rare earth reinforcing phases, both of which possess excellent chemical stability and surface activity, effectively refining the microstructure of SAC alloys, inhibiting the growth of the interfacial IMC layer, and simultaneously improving the alloy's resistance to galvanic corrosion. When used in combination, Y₂O₃ and CeO₂ produce a synergistic strengthening effect, further optimizing alloy performance. Y₂O₃, acting as a highly efficient heterogeneous nucleation core, combined with the high surface dispersion of CeO₂, refines the β-Sn matrix grain size to below the micrometer level. Simultaneously, the Zener pinning effect suppresses the coarsening of the IMC phase, resulting in a fine and dispersed distribution, thus eliminating the risk of galvanic corrosion from a large cathode-small anode configuration. The segregation of rare earth elements at grain and phase boundaries further alters the growth habit of the IMC, transforming it from a brittle needle-like structure to a corrosion-resistant blocky structure. In corrosive environments, the enriched Y and Ce elements form a dense rare earth hydroxide / oxide composite passivation film in situ. This film exhibits excellent self-healing capabilities and low electronic conductivity, effectively blocking the penetration of corrosive media and the occurrence of electrochemical reactions. Compared to single rare earth oxide modification, the composite system shows a more significant improvement in galvanic corrosion resistance.

[0024] In this invention, the C12-C20 straight-chain fatty acids mentioned in step S1 are preferably one or a mixture of lauric acid, myristic acid, palmitic acid, stearic acid, and arachidic acid, more preferably stearic acid, palmitic acid, or arachidic acid; the volatile organic solvent is preferably an organic solvent with a boiling point of 50℃ to 115℃, more preferably anhydrous ethanol, isopropanol, or isobutanol. In this invention, the C12-C20 straight-chain fatty acids can act as surface modifiers, and their hydrophobic groups can be adsorbed onto the surface of rare earth oxide nanoparticles, reducing the surface energy of the particles and preventing particle aggregation. In this invention, the volatile organic solvent can ensure the fatty acids are fully dissolved and can evaporate quickly during the subsequent drying process, avoiding solvent residue from affecting the modification effect. Anhydrous ethanol, isopropanol, and isobutanol are preferred organic solvents, with moderate evaporation rates and environmental friendliness. In this invention, the mass ratio of the volatile organic solvent, C12-C20 straight-chain fatty acids, and rare earth oxide nanoparticles mentioned in step S1 is preferably 5-10:1-3:1. In this invention, the mass ratio ensures that fatty acids fully encapsulate rare earth oxide nanoparticles, achieving effective surface modification, while avoiding excessive fatty acids leading to subsequent residues or excessive organic solvents increasing drying energy consumption, thus balancing modification effect and preparation efficiency.

[0025] In this invention, the mixing process in step S1 is preferably combined with water bath heating and ultrasonic treatment. The water bath heating temperature is preferably 60-80℃; the ultrasonic treatment conditions are preferably a power of 250-400 W, a frequency of 20-40 kHz, and an ultrasonic time of 30-40 min. In this invention, ultrasonic treatment can fully deagglomerate rare earth oxide nanoparticles in the solvent and allow fatty acid molecules to be uniformly adsorbed on the particle surface. In this invention, the solid-liquid separation method in step S1 is preferably vacuum filtration. This invention does not have special requirements for the specific operating conditions of vacuum filtration, as long as solid-liquid separation and removal of the liquid phase can be achieved. After filtration, it is preferable to wash the filter cake twice with a small amount of cold corresponding organic solvent, with each washing time preferably 1-2 min, to remove unadsorbed free fatty acids. In this invention, the solvent removal method in step S1 is preferably vacuum drying. The vacuum drying temperature is preferably 60-90℃, more preferably 75-90℃, the vacuum degree of vacuum drying is preferably -0.09 MPa, and the vacuum drying time is preferably 4-6 h, until the filter cake reaches a constant weight. In this invention, after vacuum drying, the vacuum-dried product is preferably further ground and passed through a 200-mesh sieve to obtain uniformly dispersed surface-modified rare earth oxide nanoparticles. In this invention, vacuum filtration can quickly achieve solid-liquid separation, reducing the loss of rare earth oxide nanoparticles; vacuum drying can quickly remove solvent at a lower temperature, avoiding oxidation or secondary agglomeration of the rare earth oxide nanoparticles due to excessively high temperatures.

[0026] This invention involves melting tin-silver-copper alloy powder under a protective atmosphere to obtain a Sn-based melt. In this invention, the particle size of the tin-silver-copper alloy powder in step S2 is preferably 50-200 μm, the shape is preferably spherical or near-spherical, and the loose packing density is preferably ≥4.5 g / cm³. 3 In this invention, the tin-silver-copper alloy powder is preferably one of SAC305, SAC0307, ​​and SAC387 alloy powders, wherein the composition of SAC305 alloy powder is Sn-3.0Ag-0.5Cu, the composition of SAC0307 alloy powder is Sn-0.3Ag-0.7Cu, and the composition of SAC387 alloy powder is Sn-3.8Ag-0.7Cu. The method of this invention is also applicable to other variant alloys of the Sn-Ag-Cu system. In this invention, the tin-silver-copper alloy powders are all commonly used tin-silver-copper alloy systems in the field of electronic packaging solders, adapting to the needs of different packaging scenarios. Spherical or near-spherical alloy powders have good fluidity, facilitating composition homogenization during melting; suitable particle size and loose packing density ensure that the alloy powder melts fully, avoiding unmelted particle residue. In this invention, the protective atmosphere in step S2 is preferably selected from an inert gas, a reducing gas, or a mixture thereof, and more preferably an inert gas, specifically one of nitrogen, argon, or helium. In this invention, the protective atmosphere is preferably deoxidized and dried before use. The dynamic flow rate of the protective atmosphere is preferably 0.5~2.0 L / min to maintain a slightly positive pressure environment inside the furnace. The reducing gas further removes trace oxide layers from the surface of the raw materials, improving alloy purity; the inert gas effectively isolates air and inhibits oxidation of the Sn-based melt and Sn-based alloy billet. Using a mixture of hydrogen and inert gas further removes trace oxide layers from the surface of the raw materials, improving alloy purity. In this invention, the melting in step S2 is preferably performed using vacuum induction melting. This invention does not have specific limitations on the equipment used for vacuum induction melting; conventional equipment can be used. The heating temperature for vacuum induction melting is preferably 280~350℃, more preferably 285~350℃, and the heating time is preferably 30~45 min. In a specific embodiment of the present invention, the vacuum induction melting method involves loading tin-silver-copper alloy powder into a graphite crucible, placing it inside a vacuum induction melting furnace, and evacuating the furnace cavity to ≤5×10⁻⁶ vacuum level before melting. -2Pa, then a protective atmosphere is introduced until the furnace pressure is +0.02~+0.03 MPa (gauge pressure). The steps of purging air and introducing a protective atmosphere are repeated 2~4 times to ensure the oxygen content in the furnace drops below 50 ppm, thereby suppressing oxidation loss during the melting process. In this invention, during the melting process, stirring is preferably used to ensure uniform melt composition. The preferred stirring methods are manual stirring every 10 minutes using a magnetic fluid-sealed stirring rod, or continuous stirring at 60 rpm using an electromagnetic stirring or mechanical stirring paddle, ultimately obtaining a Sn-based melt with good fluidity. In this invention, vacuum induction melting provides uniform heating and a rapid temperature rise, enabling rapid and complete melting of tin-silver-copper alloy powder. It also facilitates control of the melting temperature and atmosphere, ensuring the quality of the Sn-based melt. During the melting process in this invention, the dynamic flow rate of the protective atmosphere is preferably 0.5~1.2 L / min, maintaining a dynamic slight positive pressure inside the furnace.

[0027] In this invention, the surface-modified rare earth oxide nanoparticles are added to the Sn-based melt for dispersion and composite processing to obtain a rare earth-tin-silver-copper alloy mixture. The rare earth-tin-silver-copper alloy mixture is then subjected to atomization and rapid solidification treatment to obtain a Sn-based alloy billet. In this invention, the dispersion and composite process in step S3 is preferably ultrasonic vibration dispersion, with the preferred ultrasonic vibration frequency being 20-40 kHz and the preferred power density being 0.5-1.5 W / cm³. 2The ultrasonic vibration time is preferably 10-20 min. In a specific embodiment of the present invention, a high-temperature resistant stone ultrasonic amplitude transformer is inserted into the molten liquid to a depth of about 2 cm, and ultrasonic vibration is activated. In the present invention, the cavitation effect generated by ultrasonic vibration can effectively break the secondary agglomeration of rare earth oxide nanoparticles in Sn-based molten liquid, so that the particles are uniformly dispersed in the molten liquid, while promoting the full composite of rare earth elements and Sn-based molten liquid, avoiding local enrichment. Different ultrasonic parameters can be adapted to different amounts and types of rare earth oxide nanoparticles to ensure dispersion effect. In the present invention, based on the mass of Sn-based molten liquid, the amount of surface-modified rare earth oxide nanoparticles added in step S3 is 0.05-0.10 wt%. In the present invention, if the amount of surface-modified rare earth oxide nanoparticles added is too low, the strengthening and anti-corrosion effects of rare earth oxides cannot be fully utilized; if the amount added is too high, it is easy to cause agglomeration of rare earth oxide nanoparticles, which will reduce the mechanical properties and anti-corrosion properties of the alloy. This range of addition can achieve the optimal balance between rare earth strengthening effect and dispersion. When adding, it is preferable to first load the surface-modified rare earth oxide nanoparticles into the sealed chamber of the feeding funnel, and then perform three corresponding protective atmosphere replacements on the sealed chamber to further prevent oxidation. During feeding, it is preferable to maintain the protective atmosphere flow rate in the melting furnace at a stable 0.5~1.0 L / min, and slowly sprinkle the powder onto the surface of the Sn-based melt. In this invention, the rapid solidification treatment in step S3 is preferably water atomization; before atomization, it is preferable to introduce the rare earth-tin-silver-copper alloy mixture into the funnel in the middle of the atomization tower, control the superheat temperature to 20°C, and pre-purge the atomization system with the corresponding protective atmosphere to ensure that no air is mixed in during the atomization process. The cooling rate of the water atomization is preferably not less than 10. 2 The atomization pressure is preferably 2-5 MPa, and the atomization medium is preferably deionized water. In this invention, water atomization rapid solidification has the advantages of fast cooling rate, high production efficiency, and low cost. Rapid cooling can inhibit alloy grain growth, refine the microstructure, and simultaneously fix the dispersion state of rare earth oxide nanoparticles, preventing them from agglomerating or segregating during solidification. Using deionized water as the atomization medium can avoid the introduction of impurity ions, ensuring alloy purity. Reasonable control of the atomization pressure and cooling rate can ensure the acquisition of Sn-based alloy billets with uniform particle size and regular morphology. After the rapid atomization solidification, the process preferably includes collecting the settled alloy powder, dehydrating it, and drying it to obtain a dry Sn-based alloy billet.

[0028] This invention involves low-temperature artificial aging of Sn-based alloy billets in a protective atmosphere to obtain rare-earth-strengthened, galvanic corrosion-resistant SAC alloys. In this invention, the low-temperature artificial aging treatment in step S4 is preferably carried out in a protective atmosphere furnace, and more preferably, the furnace air is first purged by introducing a corresponding protective atmosphere. The purging flow rate is preferably 0.8~2.0 L / min, and the purging time is 30~45 min, until the oxygen content detected at the furnace tail exhaust port is below 50 ppm. After the purging is completed, the exhaust valve is closed, preferably maintaining a slight positive pressure (+0.01 MPa) inside the furnace. In this invention, the low-temperature artificial aging process parameters are preferably: heating to 80~100℃ at a heating rate of 2~3℃ / min, holding at that temperature for 48~72 h, and then cooling to room temperature with the furnace. In this invention, low-temperature artificial aging treatment can further eliminate internal stress in Sn-based alloy billets, optimize microstructure, promote uniform distribution of rare earth elements at grain boundaries, further refine the interfacial IMC layer, improve the alloy's resistance to galvanic corrosion and mechanical properties, and prevent cracks from occurring during subsequent processing.

[0029] In this invention, the preparation method preferably further includes step S5: cold-pressing the rare-earth-reinforced anti-galvanic corrosion SAC alloy, followed by hot-pressing sintering or hot extrusion at 200-240°C to obtain a rare-earth-reinforced anti-galvanic corrosion SAC alloy block. The cold-pressing pressure is preferably 80-400 MPa, and the holding time is preferably 5-15 min. In this invention, hot-pressing sintering or hot extrusion can further improve the density of the alloy block (density ≥ 99.5%), eliminate porosity defects, and enhance the mechanical properties of the alloy block, enabling it to meet the requirements of solder sheets, solder blocks, and other product forms in electronic packaging solders. In one specific embodiment of the present invention, rare earth-reinforced anti-galvanic corrosion SAC alloy powder is mixed with halogen-free flux (rosin-based) at a mass ratio of 90:10 and then ground by a three-roll mill to form a no-clean solder paste; in another specific embodiment of the present invention, rare earth-reinforced anti-galvanic corrosion SAC alloy powder is extruded and drawn to form solder wire with a diameter of 0.5 mm, both of which are suitable for the needs of different electronic packaging scenarios.

[0030] This invention also discloses a rare earth-reinforced SAC alloy resistant to galvanic corrosion, which is prepared by the method described in the above technical solution.

[0031] This invention also discloses the application of the rare earth-reinforced anti-galvanic corrosion SAC alloy prepared by the above preparation method or the rare earth-reinforced anti-galvanic corrosion SAC alloy described in the above technical solution in the field of electronic packaging solder; the alloy can be made into solder wire or solder sheet alone, or mixed with flux to make solder paste.

[0032] To further illustrate the present invention, the following detailed description, in conjunction with the accompanying drawings and embodiments, provides a rare-earth-reinforced anti-galvanic corrosion SAC alloy, its preparation method, and its applications. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0033] Example 1: Y2O3 Rare Earth Reinforced Anti-galvanic Corrosion SAC305 Alloy This embodiment provides a method for preparing a rare-earth-reinforced SAC305 alloy resistant to galvanic corrosion, specifically: 10.0 g of Y₂O₃ nanoparticles with an average particle size of 30 nm were weighed, along with 60.0 g of anhydrous ethanol with a boiling point of 78.4 °C and 20.0 g of stearic acid. These three raw materials were added to a beaker equipped with a mechanical stirrer and an ultrasonic probe. The mixture was heated in a water bath to 60 °C with magnetic stirring. After the stearic acid was completely dissolved, an ultrasonic cell disruptor was turned on, set to 300 W power and 20 kHz frequency, and ultrasonically treated for 30 min to allow the Y₂O₃ nanoparticles to fully deagglomerate in the solvent and for stearic acid molecules to be uniformly adsorbed onto the particle surface. The resulting suspension was then immediately vacuum filtered. The filter cake was washed twice with a small amount of cold ethanol to remove free fatty acids. The filter cake was then transferred to a vacuum drying oven and dried at 80 °C and a vacuum of -0.09 MPa for 4 h until constant weight was achieved. The dried particles were then ground through a 200-mesh sieve to obtain hydrophobically modified Y₂O₃ particles.

[0034] Weigh 500.0 g of SAC305 (Sn-3.0Ag-0.5Cu) alloy powder and place it in a graphite crucible. Put the crucible into a vacuum induction melting furnace and start the mechanical vacuum pump to evacuate the furnace chamber to 5×10⁻⁶. -2 The pressure was increased to 0.02 MPa (gauge pressure) to remove adsorbed air and moisture. Then, high-purity argon gas (99.999%) was introduced until the furnace pressure reached +0.02 MPa. This process was repeated three times to ensure the oxygen content in the furnace dropped below 10 ppm. Under dynamic micro-positive pressure protection with an argon flow rate of 0.5 L / min, the temperature was programmed to rise to 300℃ and held for 40 min. During this period, the melt was manually stirred every 10 min using a magnetic fluid sealed stirring rod to ensure uniform melt composition and obtain a Sn-based melt with good flowability.

[0035] Weigh 0.378 g of hydrophobically modified Y₂O₃ granules and place them into the sealed chamber of the feeding funnel. First, purge the sealed chamber three times with argon gas to ensure no air is introduced during the feeding process. While maintaining a stable argon flow rate of 0.8 L / min in the melting furnace, open the valve and slowly sprinkle the powder onto the surface of the Sn-based molten metal. Simultaneously, insert a high-temperature resistant shale ultrasonic amplitude transformer into the molten metal to a depth of approximately 2 cm, and activate ultrasonic vibration, setting the frequency to 25 kHz and the power density to 1.0 W / cm². 2The processing time was 15 minutes, utilizing cavitation to break up the secondary agglomeration of nanoparticles in the melt. The composite melt was then introduced into a funnel in the center of an atomization tower, with the superheat temperature controlled at 20°C. A high-pressure water pump was activated, using deionized water as the atomization medium, and the atomization pressure was set at 3.5 MPa. The melt stream was broken into tiny droplets under the impact of the water jet, with a measured cooling rate of approximately 150°C / s. The settled alloy powder was collected, dehydrated, and dried to obtain a Sn-based alloy billet.

[0036] Sn-based alloy powder was evenly spread in a shallow alumina dish and placed in a protective atmosphere furnace. The furnace inlet valve was opened, and high-purity nitrogen (99.999%) was introduced at a flow rate of 2.0 L / min, continuously purging for 30 min to replace the air in the furnace until the oxygen content detected at the furnace exhaust port was below 50 ppm. The exhaust valve was then closed, maintaining a slight positive pressure (+0.01 MPa) in the furnace, and the temperature was programmed to rise to 90°C at a rate of 2.5°C / min, and held at 90°C for 60 h. After cooling to room temperature with the furnace, the gas supply was stopped, yielding the rare-earth-reinforced, galvanically resistant SAC305 alloy powder of this embodiment. The obtained powder was cold-pressed in a mold at 400 MPa, and then hot-pressed and sintered in a vacuum sintering furnace at 220°C for 2 h to obtain a dense alloy block for subsequent testing.

[0037] Table 1. Y2O3 Rare Earth Reinforced Anti-galvanic Corrosion SAC305 Alloy

[0038] Example 2: CeO2 Rare Earth Reinforced Anti-galvanic Corrosion SAC387 Alloy This embodiment provides a method for preparing a rare-earth-reinforced SAC387 alloy resistant to galvanic corrosion, specifically: 10.0 g of CeO2 nanoparticles with an average particle size of 25 nm, 100.0 g of isobutanol with a boiling point of 108℃, and 30.0 g of arachidic acid were weighed. These three raw materials were added to a beaker equipped with a mechanical stirrer and an ultrasonic probe. The mixture was heated to 80℃ in a water bath with strong magnetic stirring. After the arachidic acid was completely dissolved, an ultrasonic cell disruptor was turned on, set to 400 W power and 40 kHz frequency, and ultrasonically treated for 30 min to allow the CeO2 nanoparticles to fully deagglomerate in the solvent and for the arachidic acid molecules to be uniformly adsorbed onto the particle surface. The resulting suspension was then immediately vacuum filtered. The filter cake was washed twice with a small amount of cold isobutanol to remove free fatty acids. The filter cake was then transferred to a vacuum drying oven and dried at 90℃ and a vacuum of -0.09 MPa for 6 h until constant weight was achieved, ensuring complete evaporation of the high-boiling-point solvent. The powder was then ground through a 200-mesh sieve to obtain hydrophobically modified CeO2 nanoparticles. Particles.

[0039] Weigh 500.0 g of SAC387 (Sn-3.8Ag-0.7Cu) alloy powder and place it in a graphite crucible. Put the crucible into a vacuum induction melting furnace and start the mechanical vacuum pump to evacuate the furnace chamber to 1×10⁻⁶. -2 To remove adsorbed air and moisture, high-purity helium (99.999%) was introduced until the furnace pressure reached +0.03 MPa (gauge pressure). This process was repeated three times to ensure the oxygen content in the furnace dropped below 10 ppm. Under dynamic micro-positive pressure protection with a helium flow rate of 1.2 L / min, the temperature was programmed to rise to 350℃ and held for 30 min. During this time, electromagnetic stirring was used to fully homogenize the melt, resulting in a Sn-based melt with good flowability. 0.502 g of hydrophobically modified CeO2 particles were weighed and placed into the sealed chamber of the feeding funnel in a helium-protected glove box (oxygen content <10 ppm) to ensure no air was introduced during the feeding process. While maintaining a stable helium flow rate of 1.0 L / min in the melting furnace, the valve was opened to slowly sprinkle the powder onto the surface of the Sn-based melt. While feeding the material, the high-temperature resistant stone ultrasonic amplitude transformer was inserted into the molten liquid to a depth of about 2 cm, and ultrasonic vibration was activated, with the frequency set to 40 kHz and the power density to 1.5 W / cm³. 2 The processing time was 10 minutes. High-intensity ultrasound was used to break down the high-concentration added nanoparticles in a short time. The composite melt was then introduced into a funnel in the center of the atomization tower, with the superheat temperature controlled at 20°C. The atomization system was pre-purged with helium to remove air from the pipes. A high-pressure water pump was turned on, and deionized water was used as the atomization medium. The atomization pressure was set at 5.0 MPa. The melt stream was broken into tiny droplets under the impact of the water jet, and the measured cooling rate was approximately 200°C / s. The settled alloy powder was collected, dehydrated, and dried to obtain a Sn-based alloy billet.

[0040] Sn-based alloy powder was spread evenly in a shallow alumina dish and placed in an atmosphere-protected furnace. The furnace inlet valve was opened, and high-purity helium (99.999%) was introduced at a flow rate of 0.8 L / min. The furnace was continuously purged for 30 minutes to replace the air inside. Due to the small size and high permeability of helium molecules, the furnace seal was carefully checked until the oxygen content detected at the furnace exhaust port was below 30 ppm. The exhaust valve was then closed, maintaining a slight positive pressure (+0.01 MPa) inside the furnace. The temperature was increased to 100°C at a programmed rate of 3.0°C / min and held at this temperature for 48 hours under continuous helium flow protection. After cooling to room temperature with the furnace, the gas supply was stopped, yielding the rare-earth-reinforced, galvanically resistant SAC387 alloy powder of this embodiment. The obtained powder was mixed with halogen-free flux (rosin-based) at a mass ratio of 90:10 and milled using a three-roll mill to prepare a no-clean solder paste.

[0041] Table 2 CeO2 Rare Earth Reinforced Anti-galvanic Corrosion SAC387 Alloy

[0042] Example 3: Y2O3-CeO2 rare earth reinforced anti-galvanic corrosion SAC0307 alloy This embodiment provides a method for preparing a rare-earth-reinforced SAC0307 alloy resistant to galvanic corrosion, specifically: Weigh out 6.67 g of Y₂O₃ nanoparticles (average particle size 30 nm) and 3.33 g of CeO₂ nanoparticles (average particle size 30 nm), mix them thoroughly, measure out 50.0 g of isopropanol with a boiling point of 82.6℃, and weigh out 15.0 g of palmitic acid. Add the above three raw materials to a beaker equipped with a mechanical stirrer and an ultrasonic probe, turn on the water bath to heat to 65℃ and start magnetic stirring. After the palmitic acid is completely dissolved, turn on the ultrasonic cell disruptor, set the power to 250 W and the frequency to 20 kHz, and sonicate for 40 min to fully deagglomerate the composite rare earth oxide nanoparticles in the solvent and allow palmitic acid molecules to be uniformly adsorbed on the particle surface. The resulting suspension was then immediately vacuum filtered, and the filter cake was washed twice with a small amount of cold isopropanol to remove free fatty acids. The filter cake was then transferred to a vacuum drying oven and dried at 75°C and a vacuum of -0.09 MPa for 5 h until constant weight was achieved. The mixture was then ground through a 200-mesh sieve to obtain hydrophobically modified Y2O3-CeO2 composite particles.

[0043] Weigh 500.0 g of SAC0307 (Sn-0.3Ag-0.7Cu) alloy powder and place it in a graphite crucible. Put the crucible into a vacuum induction melting furnace and start the mechanical vacuum pump to evacuate the furnace chamber to 5 × 10⁻⁶ ppm. -2 The pressure was increased to +0.02 MPa (gauge pressure) to remove adsorbed air and moisture. Then, high-purity nitrogen (99.999% purity, purified by a deoxygenating column, dew point below -40℃) was introduced until the furnace pressure reached 0.02 MPa. This process was repeated four times to ensure the oxygen content in the furnace dropped below 20 ppm. Under dynamic micro-positive pressure protection with a nitrogen flow rate of 1.0 L / min, the temperature was programmed to rise to 285℃ and held for 45 min. During this time, continuous stirring at 60 rpm was used to ensure uniform melt composition, resulting in a Sn-based melt with good flowability.

[0044] Weigh 0.251 g of hydrophobically modified Y₂O₃-CeO₂ composite granular powder and place it into the sealed chamber of the feeding funnel. First, purge the sealed chamber with nitrogen three times to ensure no air is introduced during the feeding process. While maintaining a stable nitrogen flow rate of 0.6 L / min in the melting furnace, open the valve and slowly sprinkle the powder onto the surface of the Sn-based molten metal. Simultaneously, insert a high-temperature resistant shale ultrasonic amplitude transformer into the molten metal to a depth of approximately 2 cm, and activate ultrasonic vibration, setting the frequency to 20 kHz and the power density to 0.8 W / cm². 2The processing time was 20 min, utilizing cavitation to break up the secondary agglomeration of nanoparticles in the melt. The composite melt was then introduced into a funnel in the center of the atomization tower, with the superheat temperature controlled at 20°C. The atomization system pipeline was pre-purged with nitrogen for 10 min, and a high-pressure water pump was turned on. Deionized water was used as the atomization medium, and the atomization pressure was set at 2.5 MPa. The melt stream was broken into tiny droplets under the impact of the water jet, with a measured cooling rate of approximately 120°C / s. The settled alloy powder was collected, dehydrated, and dried to obtain a Sn-based alloy billet.

[0045] Sn-based alloy powder was spread evenly in a shallow alumina dish and placed in an atmosphere-protected furnace. The furnace inlet valve was opened, and high-purity nitrogen gas (99.999% purity, dried with molecular sieves) was introduced at a flow rate of 1.5 L / min. This was continuously purged for 45 minutes to replace the air in the furnace until the oxygen content detected at the furnace exhaust port was below 50 ppm. The exhaust valve was then closed, maintaining a slight positive pressure (+0.01 MPa) in the furnace. The temperature was increased to 80°C at a programmed rate of 2.0°C / min and held at this temperature for 72 hours under continuous nitrogen flow (0.5 L / min). After cooling to room temperature with the furnace, the gas supply was stopped, yielding the rare-earth-reinforced, galvanically resistant SAC0307 alloy powder of this embodiment. The obtained powder was extruded and drawn into solder wires with a diameter of 0.5 mm.

[0046] Table 3. Y2O3-CeO2 Rare Earth Reinforced Anti-galvanic Corrosion SAC0307 Alloy

[0047] Comparative Example 1 The difference between this comparative example and Example 1 is that it directly uses unmodified raw Y2O3 nanoparticles. 0.378 g of raw Y2O3 nanoparticles with an average particle size of 30 nm were weighed, placed in a sealed chamber of a feeding funnel, and purged with argon gas. This powder was then directly sprinkled into the SAC305 melt prepared according to the method in Example 1, followed by ultrasonic dispersion, water atomization powdering, and subsequent low-temperature aging treatment. All other raw material ratios, melting process parameters (temperature, time, gas flow rate, and purity), ultrasonic parameters, atomization conditions, and aging regime were the same as in Example 1.

[0048] Comparative Example 2 The difference between this comparative example and Example 1 is that the low-temperature aging treatment step is omitted. After completing the rare earth particle surface modification, alloy smelting, nanocomposite ultrasonic dispersion, and water atomization powder preparation according to the method of Example 1 to obtain Sn-based alloy billet powder, the powder was directly cooled to room temperature in air without undergoing the 90℃ / 60h nitrogen-protected low-temperature aging treatment, and then immediately subjected to cold pressing and hot pressing sintering. The remaining raw material ratios, surface modification processes, and gas protection parameters (purity, flow rate, number of replacements) during smelting and atomization were the same as in Example 1.

[0049] Application Example 1: Corrosion Resistance Testing Alloy blocks, solder paste, and solder wire from Examples 1-3 were used to prepare standard Cu substrate solder joints (soldering temperature 260°C, holding time 2 s, soldering pressure 0.5 MPa). Standard alloys SAC305, SAC387, and SAC0307, ​​as well as alloy products prepared in Comparative Examples 1 and 2, were also prepared. A simulated high-salt-spray, high-temperature, and high-humidity corrosion environment was induced by immersion in a 3.5 wt% NaCl solution, followed by placement in a constant temperature and humidity test chamber. The chamber temperature was set to 85°C, and the relative humidity was maintained at 85%RH by controlling the solution state. After 72 hours of continuous treatment, the samples were removed, cleaned with deionized water to remove residual salt, and dried in a 60°C oven for 2 hours for SEM observation. Simultaneously, uncorroded solder joint samples were prepared for potential difference detection.

[0050] SEM observation was performed using a scanning electron microscope (SEM) at 5000x magnification to observe the microstructure of the solder joints, the distribution of corrosion points, and the morphology and thickness of the IMC layer. Figure 1 As can be seen, Examples 1-3 of this invention refined the SAC alloy grains, transforming the IMC layer from a thick, brittle layer to a thin, dense, continuous layer, fundamentally optimizing the interface structure. Specifically, Example 1 exhibits significantly refined microstructure with fine, uniform grains and no obvious dendrites. The interface IMC layer is noticeably thinner, denser, and continuous, without layered cracking. After corrosion testing, there was virtually no pitting corrosion, only slight, uniform surface corrosion, significantly improving resistance to galvanic corrosion. Example 2 shows an even denser and more uniform microstructure with further refined grains and a thin, flat IMC layer. The sample showed almost no corrosion marks, demonstrating a significant overall passivation effect. Example 3 exhibits the most uniform microstructure, the finest grains, and the thinnest and densest interface IMC layer. Fine, dispersed rare-earth-Sn-based IMC particles are formed within the matrix, achieving overall passivation with no pitting corrosion and optimal corrosion resistance. The microstructure of standard SAC305, SAC387, and SAC0307 exhibits coarse dendritic morphology, with a thick and continuous brittle IMC layer at the interface, resulting in obvious pitting corrosion at the interface after corrosion. Figure 1 The area circled in white shows severe corrosion at the grain boundaries and phase interfaces, which is a typical characteristic of large cathodic-small anodic galvanic corrosion.

[0051] Potential difference detection was performed using an electrochemical workstation with a saturated calomel electrode as the reference electrode and a platinum electrode as the auxiliary electrode. The potential difference between the Sn substrate and the Cu6Sn5 IMC layer in the solder joint was measured. The smaller the potential difference, the weaker the tendency for galvanic corrosion. As shown in Table 4, the Sn-IMC potential difference in Examples 1-3 was ≤0.04 V, significantly lower than that in Comparative Examples 1-2 (0.09-0.14 V). In Example 3, the potential difference was only 0.005 V, indicating a substantial improvement in resistance to galvanic corrosion. Examples 1-3 of this invention can significantly suppress galvanic corrosion and are fully adaptable to harsh operating conditions such as high temperature, high humidity, high salt spray, and strong vibration.

[0052] Table 4 Sn matrix and Cu6Sn5 Potential difference test results

[0053] Application Example 2: Mechanical Strength and Wetness Testing For the bulk material samples (Example 1, Comparative Examples 1-2), the shear strength of the solder joints (shear rate 1 mm / min) and the compressive strength of the alloy bulk material (compression rate 2 mm / min) were tested using a universal testing machine. For the solder wire / solder paste samples (Examples 2-3), the shear strength of the solder joints was tested. Five samples were tested in each group, and the average value was taken. As shown in Table 5, the shear strength of the solder joint in Comparative Example 1 was only 28.6 MPa, and the fracture mode was brittle fracture at the interface, with cracks propagating along the thick and brittle IMC layer, resulting in poor reliability. The strength of Comparative Example 2 was slightly improved, but the fracture mode was still mainly at the interface, and the improvement was limited. Examples 1-3 of this invention improved the fracture mode from brittle fracture at the interface to ductile fracture in the matrix by refining the grains with rare earth elements and thinning and densifying the interface IMC layer, thus eliminating the weak fracture source at the interface: the shear strength of the solder joints was increased by 28.7% to 34.6% compared with Comparative Example 1; the compressive strength of the bulk material in Example 1 was increased by 16.3% compared with Comparative Example 1 and by 7.95% compared with Example 2, with significantly enhanced mechanical properties, and could withstand higher stress and vibration loads.

[0054] Table 5. Results of weld joint shear strength test

[0055] Wettability was tested using the droplet method. The solder / solder paste was heated to 260°C on a Cu substrate, melted, and spread. The wetting angle was measured; a smaller wetting angle indicates better wettability. Table 6 shows that Comparative Example 1 had a wetting angle of 48.3°, indicating only average spreadability and a tendency to develop soldering defects such as balling and burrs. Comparative Example 2 showed a slightly lower wetting angle, but still did not meet the requirements for high-end packaging. In Examples 1-3 of this invention, the rare earth oxides, after being modified with fatty acids for hydrophobicity, exhibited significantly reduced melt surface tension, resulting in a wetting angle more than 30% lower than Comparative Example 1. The spread was uniform, without balling or burrs, fully meeting the process requirements for high-precision, high-density electronic packaging.

[0056] Table 6 Results of wetting angle test

[0057] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a rare earth-reinforced SAC alloy resistant to galvanic corrosion, characterized in that, Includes the following steps: S1. Rare earth oxide nanopowder is mixed with a volatile organic solvent and C12~C20 straight-chain fatty acids to obtain a premix. The premix is ​​subjected to solid-liquid separation and solvent removal to obtain surface-modified rare earth oxide nanoparticles. The boiling point of the volatile organic solvent is 50℃~115℃. S2. Melt tin-silver-copper alloy powder under a protective atmosphere to obtain Sn-based melt; S3. The surface-modified rare earth oxide nanoparticles are added to the Sn-based melt for dispersion and compounding to obtain a rare earth-tin-silver-copper alloy mixture. The rare earth-tin-silver-copper alloy mixture is then subjected to atomization and rapid solidification treatment to obtain a Sn-based alloy billet. The amount of surface-modified rare earth oxide nanoparticles added is 0.05~0.10 wt%. S4 and Sn-based alloy billets were subjected to low-temperature artificial aging treatment in a protective atmosphere to obtain rare earth-reinforced SAC alloys resistant to galvanic corrosion.

2. The preparation method according to claim 1, characterized in that, The C12~C20 straight-chain fatty acids mentioned in step S1 are one or more of lauric acid, myristic acid, palmitic acid, stearic acid, and arachidic acid; the volatile organic solvent is one or more of ethanol, isopropanol, and isobutanol.

3. The preparation method according to claim 1, characterized in that, The rare earth oxide nanopowder in step S1 is one or a combination of Y2O3 nanopowder and CeO2 nanopowder; when the rare earth oxide nanopowder is a combination of Y2O3 nanopowder and CeO2 nanopowder, the mass ratio of Y2O3 nanopowder to CeO2 nanopowder is 1~3:

1.

4. The preparation method according to claim 1, characterized in that, The mass ratio of the volatile organic solvent, C12~C20 straight-chain fatty acid and rare earth oxide nanopowder in step S1 is 5~10:1~3:

1.

5. The preparation method according to claim 1, characterized in that, The protective atmosphere described in steps S2 and S4 is selected from inert gas, reducing gas, or a mixture thereof.

6. The preparation method according to claim 1, characterized in that, In step S3, the dispersion and recombination method is ultrasonic vibration dispersion; the frequency of the ultrasonic vibration is 20~40 kHz, and the power density is 0.5~1.5 W / cm². 2 The duration of ultrasonic vibration is 10-20 minutes.

7. The preparation method according to claim 1, characterized in that, The rapid solidification atomization process in step S3 is water atomization; the cooling rate of the water atomization is not less than 10. 2 ℃ / s, atomization pressure is 2~5 MPa, and the atomization medium is deionized water.

8. The preparation method according to any one of claims 1 to 7, characterized in that, The method also includes: S5. The rare earth-reinforced anti-galvanic corrosion SAC alloy is cold-pressed and then hot-pressed or hot-extruded at 200~240℃ to obtain rare earth-reinforced anti-galvanic corrosion SAC alloy block.

9. A rare earth-reinforced SAC alloy resistant to galvanic corrosion, characterized in that, The alloy is prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the rare earth-reinforced anti-galvanic corrosion SAC alloy prepared by the preparation method according to any one of claims 1 to 8 or the rare earth-reinforced anti-galvanic corrosion SAC alloy according to claim 9 in the field of electronic packaging solder; the alloy can be made into solder wire or solder sheet alone, or mixed with flux to make solder paste.

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