An amorphous tin alloy solder powder and its preparation method

Abstract

This invention relates to an amorphous tin alloy solder powder and its preparation method, belonging to the field of brazing materials technology. It solves the problems of low amorphous ratio, high oxygen content, poor powder morphology and particle size consistency, complex processing equipment, and high difficulty in mass production of existing tin alloy solders. The preparation method includes: vacuum melting the raw materials of the amorphous tin alloy solder to obtain an alloy melt; dispersing the alloy melt to obtain alloy droplets; using a double-sided liquid-cooled copper template to extrude and cool the alloy droplets to obtain amorphous alloy flakes; and crushing and sieving the amorphous alloy flakes. This invention uses a double-sided liquid-cooled copper template to achieve ultra-high-speed cooling of the alloy droplets, promoting the formation of the amorphous phase; and by adding trace amounts of rare earth elements to broaden the supercooled liquid phase region of the alloy, it achieves synergistic optimization of amorphous formation capability and solder service performance. This method is beneficial for promoting the application of tin alloy solders in high-end electronic packaging.

Description

Technical Field

[0001] This invention relates to the field of brazing materials technology, and in particular to an amorphous tin alloy brazing powder and its preparation method. Background Technology

[0002] With the rapid development of electronic packaging technology towards high power, high density, and high reliability, more stringent requirements are being placed on the high-temperature resistance, creep resistance, and welding reliability of soldering materials. Amorphous solders, due to their long-range disordered and short-range ordered atomic structure, possess high strength, high corrosion resistance, excellent diffusion properties, and creep resistance. Introducing an amorphous structure into tin-based solders can significantly improve the soldering reliability and mechanical properties, making it a core research and development direction in the field of high-end electronic packaging solders.

[0003] However, existing traditional preparation techniques for amorphous solders, such as single-roller spinning, gas atomization, and mechanical alloying, have various problems that limit the application of amorphous tin alloy solders in electronic packaging. Specifically, the single-roller spinning method can only produce amorphous thin strips, which require subsequent crushing and processing, resulting in low powder yield and poor morphology controllability; the gas atomization method typically has a cooling rate of less than 10. 5 K / s makes it difficult to stably form an amorphous phase, and the alloy is easily oxidized during high-temperature atomization; mechanical alloying has a long preparation cycle, easily introduces impurities, and the amorphous phase has insufficient uniformity, making it difficult to mass-produce on a large scale.

[0004] To address the above issues, there are related technologies for optimizing the traditional preparation process of amorphous tin-based solders. However, the performance improvement of amorphous tin-based solders obtained through process optimization is limited. CN117718636A discloses a process for obtaining high-strength and high-toughness nanoparticle tin-based composite solders through stepwise variable-speed cooling. This process obtains nanoparticle-reinforced composite solders by controlling the cooling rate. However, it has shortcomings in controlling the cooling rate and temperature change range, making it difficult to achieve precise control over grain size and distribution, and thus unable to stably prepare high-purity amorphous phase powder. CN114433854A discloses a gas atomization powder preparation device, atomization powder preparation method, and amorphous powder. The combined design of the powder spraying bag and atomization chamber avoids clogging. However, this device still needs improvement in terms of the cooling rate of the powder jet and the formation efficiency of amorphous powder, and cannot break through 10. 6 The cooling rate threshold of K / s results in insufficient stability for amorphous phase formation. CN107900364A discloses an apparatus for preparing amorphous metal powder by ultrasonic atomization and recooling, which improves the amorphous formation capability by combining ultrasonic atomization with secondary cooling. However, the equipment has a complex structure, high operating cost, and difficulty in controlling oxygen content, making it difficult to meet the stringent requirements of high-end electronic packaging for the oxygen content of solder powder.

[0005] Therefore, there is an urgent need for a new amorphous tin alloy brazing powder and its preparation method, which can promote the uniform and stable formation of the amorphous phase in the brazing material, while taking into account service performance, reducing oxygen pollution, simplifying equipment structure, and reducing costs, so as to realize the large-scale production and application of amorphous tin alloy brazing materials. Summary of the Invention

[0006] Based on the above analysis, the present invention aims to provide an amorphous tin alloy solder powder and its preparation method, in order to solve at least one of the problems of low amorphous rate, high oxygen content, poor powder morphology and particle size consistency, complex process equipment, high cost, and difficulty in mass production of tin alloy solder in the prior art.

[0007] On one hand, embodiments of the present invention provide a method for preparing amorphous tin alloy solder powder, the method comprising the following steps: S1 melts the raw materials of the amorphous tin alloy brazing filler to obtain an alloy melt; S2 disperses the alloy melt to obtain alloy droplets; S3 uses a double-sided liquid-cooled copper template to extrude and cool the alloy droplets to obtain amorphous alloy sheets; S4 crushes and sieves the amorphous alloy sheet.

[0008] Furthermore, steps S1-S4 are all performed under an inert atmosphere.

[0009] Furthermore, by mass percentage, the chemical composition of the amorphous tin alloy solder is Sn 93.0%~99.8%, Ag 0.1%~4.5%, Cu 0.1%~1.5%, and rare earth elements 0.1%~0.5%.

[0010] Furthermore, the rare earth element is at least one of Ce, Y, La, and Nb.

[0011] Furthermore, in step S2, the alloy melt is dispersed using a vibration dripping method, with specific conditions including: a melt superheat of 30~80°C, a liquid column height of 30~120 mm, a nozzle orifice diameter of 0.2~1.0 mm, preferably 0.3~0.8 mm, and a vibration frequency of 25~67 kHz, preferably 52~58 kHz.

[0012] Furthermore, in step S2, the diameter of the alloy droplet is 0.5~2.0 mm, and the sphericity is ≥0.90.

[0013] Furthermore, in step S3, the conditions for extruding and cooling the alloy droplets using a double-sided liquid-cooled copper template include: a temperature of -10 to 10 ℃, a pressure of 10 to 50 MPa (preferably 15 to 40 MPa), a mold closing rate of 5 to 12 m / s, a holding time of 1 to 5 ms (preferably 1 to 3 ms), and a mold opening rate of 4 to 8 m / s.

[0014] Furthermore, in step S3, the cooling rate of the extrusion cooling is 1×10⁻⁶. 6 ~1×10 7 K / s.

[0015] Furthermore, in step S3, the thickness of the amorphous alloy sheet is 0.1~0.3 mm.

[0016] On the other hand, embodiments of the present invention also provide an amorphous tin alloy solder powder, which is prepared by the aforementioned preparation method.

[0017] Furthermore, the brazing powder has a particle size ≤50 μm, an amorphous content ≥95%, and an oxygen content <100 ppm.

[0018] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects: 1. Unlike existing technologies for preparing amorphous brazing fillers, this invention combines alloy droplet dispersion technology, extrusion cooling technology, and rare earth element micro-alloying modification technology. This not only enables ultra-high-speed cooling of alloy droplets and promotes the formation of amorphous phases, but also, with the aid of an inert preparation atmosphere and a crushing process, results in tin alloy brazing materials with high amorphous content (≥95%) and low oxygen content (<100 ppm), and uniform and controllable particle size (D50 of 25~40 μm) and morphology (regular spherical shape).

[0019] 2. By controlling the type and content of rare earth elements added, this invention utilizes the surface activity of rare earth elements to effectively suppress the precipitation of brittle metal phases (such as Sn-Cu) and significantly broaden the supercooled liquid phase region of the alloy, thereby greatly improving the amorphous forming ability of the alloy. At the same time, it can achieve synergistic optimization of amorphous forming ability and brazing filler metal service performance without damaging the welding performance and electrical and thermal conductivity of the filler metal.

[0020] 3. This invention, by adjusting the alloy melt dispersion process and conditions, can control the size and sphericity of the alloy droplets; combined with the adjustment of the extrusion cooling process and conditions, the cooling rate can be stably achieved to ≥10. 6K / s, breaking through the upper limit of cooling rate in traditional processes, enables alloy droplets to cool to below the glass transition temperature in a very short time (1~5 ms), thereby promoting the uniform and stable formation of the amorphous phase; at the same time, it can precisely control the size (such as thickness) of the amorphous alloy sheet, and in conjunction with subsequent crushing and sieving processes, improve the consistency of particle size distribution and morphology of the final brazing powder, and realize the controllability of brazing powder particle size.

[0021] 4. Compared with traditional preparation methods, the present invention adopts a modular double-sided liquid-cooled copper template extrusion device. The core component is a modular liquid-cooled copper template. It does not require the high-precision nozzles and high-pressure gas source system of the traditional atomization method, nor the high-speed rotating roller system of the single-roller spinning method. The equipment structure is greatly simplified, the operation and maintenance costs are significantly reduced, and the process has strong continuity and high production efficiency. It can be adapted to industrial-scale production, achieving a balance between high performance and low cost. It is conducive to promoting the large-scale production of tin alloy solder and its application in high-end electronic packaging.

[0022] 5. The amorphous tin alloy solder powder prepared by the method of this invention has a high amorphous content (≥95%) and a low oxygen content (<100 ppm), with uniform and controllable particle size (D50 of 25~40 μm), and a steady-state creep rate of less than 1×10⁻⁶ under 150℃ / 10MPa conditions. -7 s - ¹; The shear strength retention rate under 200℃ / 1000h conditions is greater than 70%, and the creep resistance and high temperature resistance are far superior to conventional crystalline Sn-3.0Ag-0.5Cu solder.

[0023] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0024] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0025] Figure 1 is a process flow diagram of the preparation process of the amorphous tin alloy solder powder of the present invention; Figure 2 This invention relates to a system for preparing amorphous tin alloy solder powder. Figure 3 A photograph of the amorphous alloy sheet obtained by this invention; Figure 4This is an electron microscope image of the amorphous tin alloy solder powder prepared according to the present invention; Figure 5 This is a particle size distribution curve of the amorphous tin alloy solder powder prepared according to the present invention; Figure 6 The XRD pattern of the amorphous tin alloy solder powder prepared in this invention; Figure 7 The image shows the DSC thermal analysis curve of the amorphous tin alloy solder powder prepared in this invention. Figure 8 The TEM-HRTEM selected area electron diffraction pattern of the amorphous tin alloy solder powder prepared in this invention; Figure label: 1-Medium frequency induction heat preservation crucible; 2-Sn alloy melt; 3-Vacuum pressure-resistant shell; 4-Vibration dripping device; 5-Liquid-cooled copper template; 6-Servo hydraulic mold closing drive cylinder; 7-Amorphous sheet collection tank; 8-Argon cylinder; 9-Chiller unit; 10-Vacuum unit; 11-Electrical control system. Detailed Implementation

[0026] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0027] Traditional crystalline tin-based solders and copper-based composite amorphous powders have insufficient interconnect performance and creep resistance under high-temperature service environments, which can no longer meet the application requirements of high-end electronic packaging. Amorphous solders, on the other hand, have high strength, high corrosion resistance, excellent diffusion performance and creep resistance due to their long-range disordered and short-range ordered atomic structure. Introducing amorphous structures into tin-based solders can significantly improve the soldering reliability and mechanical properties of the solders, making it a core research and development direction in the field of high-end electronic packaging solders.

[0028] However, existing traditional preparation methods and optimized processes for amorphous solders, such as single-roller spinning, gas atomization, and mechanical alloying, suffer from problems such as low amorphous ratio, high oxygen content, inability to precisely control particle size and morphology, complex preparation equipment, high cost, and difficulty in large-scale production. As a result, amorphous tin alloy solders cannot be widely used in high-end electronic packaging.

[0029] Therefore, this invention provides a method for preparing amorphous tin alloy solder powder, the specific preparation process of which is as follows: Figure 1 As shown, it includes the following steps: S1 melts the raw materials of the amorphous tin alloy brazing filler to obtain an alloy melt; S2 disperses the alloy melt to obtain alloy droplets; S3 uses a double-sided liquid-cooled copper template to extrude and cool the alloy droplets to obtain amorphous alloy sheets; S4 crushes and sieves the amorphous alloy sheet.

[0030] It should be noted that tin alloys are highly susceptible to oxidation during high-temperature smelting and powdering processes, which leads to a significant decrease in the wettability and interfacial bonding strength of the brazing filler metal, directly affecting welding performance and connection reliability. Therefore, it is necessary to isolate oxygen during the preparation process of the amorphous tin alloy brazing filler metal.

[0031] Specifically, since tin alloys are subject to oxidation risks throughout the entire process, including high-temperature (500~600℃) melting, high-temperature droplet extrusion cooling, and sheet crushing, steps S1-S4 of this invention are all carried out under an inert atmosphere.

[0032] More specifically, in the preparation process of the amorphous tin alloy brazing filler, the present invention constructs a full-process inert atmosphere or inert atmosphere + low-temperature environment protection system. The vacuum melting and the dispersion of the melt are both protected by high-purity argon gas to avoid oxidation of the high-temperature melt and alloy droplets. The extrusion cooling step is carried out in a closed inert atmosphere device, combined with a low-temperature silicone oil cooling medium, to isolate oxygen and reduce the risk of high-temperature oxidation. The crushing step is carried out in a low-temperature, inert environment to avoid oxidation of the surface of the newly formed powder during the crushing process. Finally, the oxygen content of the finished powder is stably controlled below 100 ppm, thereby improving the welding performance of the brazing filler.

[0033] It should be noted that existing Sn-Ag-Cu solders have a narrow supercooled liquid phase region and weak amorphous phase formation ability. During preparation, brittle Sn-Cu phases easily precipitate, severely affecting the solder's service performance and amorphous phase stability. This invention optimizes the alloy composition to improve the alloy's amorphous phase formation ability without compromising its soldering performance, electrical conductivity, or thermal conductivity.

[0034] Specifically, by mass percentage, the chemical composition of the amorphous tin alloy solder is Sn 93.0%~99.8%, Ag 0.1%~4.5%, Cu 0.1%~1.5%, and rare earth elements 0.1%~0.5%.

[0035] More specifically, the rare earth element is at least one of Ce, Y, La, and Nb, and can be Ce, Y, La, Nb, Ce and Y, Ce and La, Ce and Nb, preferably Ce and Y. Utilizing the surface activity of rare earth elements, the precipitation of the brittle Sn-Cu phase is effectively suppressed. Simultaneously, taking advantage of the larger atomic radii of rare earth elements, the disorder of the alloy components is increased, long-range atomic diffusion and crystallization are suppressed, the alloy's Tx (crystallization temperature) is increased, the supercooled liquid phase region ΔT of the alloy is significantly widened, and the amorphous forming ability of the alloy is greatly improved without compromising the solder's welding performance and electrical and thermal conductivity, thus achieving synergistic optimization of amorphous forming ability and solder service performance.

[0036] More specifically, the rare earth element content in the alloy can be 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5% by mass percentage. If the rare earth element content is too high, it will have limited effect on improving the amorphous ratio of the alloy and will easily lead to the formation of microcrystals / nanocrystals, which are prone to local crystallization during powder cooling, resulting in uneven microstructure. If the content is too high, hard and brittle rare earth-tin phase (RE-Sn) such as LaSn3, Y5Sn3, and CeSn2 will easily precipitate, cutting the matrix and becoming crack sources. Excessive RE atom segregation and promotion of heterogeneous nucleation will actually reduce the amorphous ratio and lead to a decrease in the crystallization temperature Tx.

[0037] It should be noted that, in order to improve the amorphous ratio and purity of the brazing filler metal and reduce impurities, this invention uses high-purity Sn, Ag, and Cu with a purity ≥99.9% as base raw materials, and adds rare earth elements Ce or Y with a purity ≥99.99% as modification raw materials as needed. Sn, Ag, and Cu are used as base raw materials, and are precisely weighed and mixed according to the target mass ratio. The weighed raw materials are then placed in a vacuum induction furnace at a vacuum degree ≥1.0 × 10⁻⁶. - Pretreatment is carried out at ³Pa for 30-45 minutes to remove the oxide film and adsorbed gas on the surface of the raw material.

[0038] The present invention involves melting pretreated raw materials in a vacuum induction furnace under an inert gas atmosphere to prepare a uniform tin alloy melt. The inert atmosphere can be at least one of argon, neon, and helium.

[0039] According to some preferred embodiments of the present invention, the melting specifically includes: filling high-purity argon (purity ≥ 99.999%) into a vacuum induction furnace until the furnace pressure reaches 0.1 - 0.2 MPa, heating at a heating rate of 20 - 25 °C / min to 500 - 600 °C, preferably 530 - 580 °C, which is about 100 - 150 °C higher than the Sn-Ag-Cu eutectic temperature, heating at a constant speed throughout the process to avoid local overheating, and holding for 15 - 35 min; and during the holding process, using the alternating magnetic field of the vacuum induction furnace to generate induced eddy currents in the melt, forming forced convection, and controlling by adjusting the current of the induction coil, with the appearance of uniform circular ripples on the melt surface as the criterion, to achieve rapid and uniform mixing of the internal components of the melt.

[0040] More specifically, the present invention limits the addition order of the main elements, gradually dissolving the high-melting-point components (Cu, Ag) into the low-melting-point Sn matrix to avoid local composition segregation.

[0041] It should be noted that in order to reduce the burning loss and oxidation of rare earth elements during the melting process of raw materials and ensure their uniform distribution in the melt, the present invention adds rare earth elements later.

[0042] Specifically, after the raw material metals Sn, Ag, and Cu are completely melted and held for 10 - 20 min, the rare earth elements wrapped in pure tin foil are quickly put into the center of the melt, and then held for 10 - 20 min until completely dissolved.

[0043] The optimal addition order of the raw materials of the present invention is Sn → Cu → Ag → rare earth elements. First, melt the low-melting-point Sn, then add the high-melting-point Cu and Ag to gradually melt them, forming a Sn-Cu-Ag-based melt, and finally add the rare earth elements that are easy to oxidize and burn out to reduce their contact time with air. An incorrect addition order will cause a large amount of burning loss of rare earth elements, unable to effectively broaden the supercooled liquid phase region, and ultimately reduce the amorphous rate of the product.

[0044] After the melting and holding of the alloy raw materials are completed, 6 - 8 samples are taken from three different depths (upper, middle, and lower) of the melt and four positions (center and edge of the furnace body), and quickly quenched and solidified with water. The mass fractions of Sn, Ag, Cu, and rare earth elements are accurately measured by inductively coupled plasma optical emission spectrometry (ICP-OES), and the micro-area composition distribution is analyzed by energy dispersive spectrometer (EDS) as an auxiliary. It is qualified that the deviation of the content of each element in all samples from the target composition is ≤ ±0.1%, and the composition deviation between samples at different positions is ≤ ±0.05%.

[0045] It should be noted that the present invention uses existing technology to disperse the alloy melt into droplets, which can be gas / water fluid impact atomization, mechanical centrifugal atomization, ultrasonic vibration atomization, pulse micro-orifice injection, or electrostatic atomization. In order to improve the monodispersity and sphericity of the alloy droplets, accurately control the particle size of the alloy droplets, simplify the equipment, and reduce oxygen pollution and cost, the present invention preferably uses ultrasonic vibration atomization technology to disperse the alloy melt.

[0046] Specifically, in step S2, the alloy melt is dispersed using a vibration dripping method.

[0047] More specifically, in step S2, the superheat range of the alloy melt to be dispersed is 30~80℃, which can be 30℃, 35℃, 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, or 80℃. The lower the superheat, the higher the melt viscosity and the faster the droplet solidification speed, requiring a higher mold closing rate to complete the extrusion before the droplet solidifies. However, the superheat cannot be too low, otherwise the viscosity of the tin alloy melt will increase exponentially with decreasing temperature, the electromagnetic stirring effect will decrease significantly, the high melting point Cu and Ag components will not dissolve sufficiently, and local component segregation will occur. This leads to increased surface tension, resulting in excessively high surface tension in the liquid column. Vibrational energy is unable to overcome this surface tension, causing regular necking and easily producing long tails, connected droplets, and dumbbell-shaped droplets. Higher superheat results in better melt flowability and slower solidification, allowing for lower mold closing rates. However, the superheat cannot be too high, otherwise the reaction rate between tin and oxygen at high temperatures will increase exponentially. Even under high-purity argon protection, the formation rate of the oxide film on the melt surface will be accelerated by 3 to 5 times, and the oxygen content of the finished powder will be >200ppm, which does not meet the requirement of <100ppm. In addition, excessively high superheat will also cause the burning of rare earth elements such as Ce and Y, resulting in a decrease in amorphous ratio.

[0048] More specifically, in step S2, during the dispersion of the alloy melt by vibration dripping, the height of the melt column is 30-120 mm, which can be 30 mm, 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, 100 mm, 110 mm, or 120 mm, preferably 60-80 mm. If the column is too low, it will lead to insufficient pressure, unstable dripping frequency, and large particle size fluctuations; if the column is too high, it will lead to excessive static pressure, column dispersion, vibration failure, and severe splashing. Appropriately adjusting the column height ensures stable melt flow and prevents fluctuations.

[0049] More specifically, in step S2, the nozzle orifice diameter used during the vibratory dripping process determines the basic particle size and flow rate of the dispersed alloy droplets. In this invention, the nozzle orifice diameter is 0.2~1.0 mm. The nozzle orifice diameter can be 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, or 1.0mm. A larger nozzle orifice diameter results in a larger droplet diameter, greater mass, stronger falling kinetic energy, and faster spreading speed, requiring a higher mold closing rate to complete extrusion before droplet spreading. However, the nozzle orifice diameter cannot be too large, as this leads to excessively large droplets, insufficient cooling rate, easy crystallization, and poor dimensional uniformity. Conversely, a smaller nozzle orifice diameter results in a smaller droplet diameter, allowing for a lower mold closing rate. However, it cannot be too small either, as excessively small orifices are prone to clogging, unstable flow, and difficulty in controlling droplet breakage. Small-aperture melts are not easily broken by vibration, easily forming continuous thin streams, stringing, and numerous satellite droplets. Excessively small droplets cool rapidly, easily leading to over-cooling before contact with the mold plate, poor spreading, uneven cooling rate, localized crystallization, high equipment load requirements, and reduced efficiency. The nozzle orifice diameter described in this invention is preferably 0.3~0.8 mm.

[0050] More specifically, in step S2, the vibration frequency during the vibration dripping process determines the droplet size and yield. The vibration frequency of this invention is 25~67 kHz, which can be 25kHz, 28kHz, 30kHz, 32kHz, 35kHz, 38kHz, 41kHz, 44kHz, 47kHz, 50kHz, 52kHz, 55kHz, 58kHz, 61kHz, 64kHz, or 67kHz. The higher the vibration frequency, the shorter the droplet falling interval, the shorter the required mold closing cycle, and the mold closing rate needs to be increased synchronously. However, the vibration frequency cannot be too high, as this will result in droplets that are too small and many satellite droplets, which can easily lead to over-cooling before contacting the template, poor spreading, uneven cooling rate, local crystallization, high equipment load requirements, and low efficiency. The lower the vibration frequency, the longer the droplet falling interval, which can be adapted to a lower mold closing rate. However, it cannot be too low, as this can easily lead to a long droplet break cycle, excessively large droplets, or continuous flow, resulting in uncontrolled particle size, slow spreading on the double-sided liquid-cooled template, thick melt pool, and easy crystallization. The preferred kHz range is 52~58kHz.

[0051] More specifically, in step S2, the amplitude during the vibration dripping process affects the uniformity of fracture. The amplitude during the dripping process in this invention is 0.02~0.06 mm, which can be 0.02 mm, 0.03 mm, 0.04 mm, 0.05 mm, or 0.06 mm, preferably 0.03~0.05 mm. If the amplitude is too small, the vibration excitation energy will be insufficient, and the melt jet will not be able to form a regular necking. It will only break naturally by gravity and surface tension, resulting in incomplete droplet breakage, long tails, connected droplets, wide particle size distribution, uneven particle size, and decreased sphericity. If the amplitude is too large, it will easily lead to excessive stretching of the liquid column. When the main droplet separates, the tail will be torn off, generating a large number of satellite droplets. The particle size will show a bimodal distribution, the liquid column will splash and impact the template, resulting in insufficient spreading, and at the same time, it will deteriorate the amorphous structure and equipment life.

[0052] By controlling the process parameters during the vibration dripping process, this invention can obtain uniform alloy droplets with uniform size and high sphericity, and drop them at a uniform speed between the left and right double-sided liquid-cooled copper molds. This ensures that the morphology and size of the amorphous sheet (e.g., Φ3.2mm×0.1mm) can be precisely controlled through the subsequent extrusion cooling process, thus ensuring the uniformity of the sheet.

[0053] Specifically, in step S2, the alloy droplets obtained after dispersing the alloy molten material have a diameter of 0.5~2.0 mm and a sphericity of ≥0.90.

[0054] It should be noted that the distance from the nozzle outlet to the working surface of the double-sided liquid-cooled copper template, i.e. the distance the alloy droplet falls freely, determines the size and uniformity of the alloy droplet to be extruded and cooled, and directly affects the droplet cooling rate and amorphous formation capability.

[0055] Specifically, the height of the free fall of the alloy droplets is controlled to be 80~150 mm, which can be 80 mm, 85 mm, 90 mm, 95 mm, 100 mm, 105 mm, 110 mm, 115 mm, 120 mm, 125 mm, 130 mm, 135 mm, 140 mm, 145 mm, or 150 mm. The greater the drop height, the longer the total droplet descent time, and the larger the tolerance range for the mold closing rate, allowing for the adaptation to lower mold closing rates. However, the drop height cannot be too high, as this would result in a long droplet flight time, excessive pre-cooling, insufficient superheating upon impact with the template, a thin melt pool, a cooling rate drop below the critical value, low amorphous ratio, and the droplet is prone to tailing. The tail after vibration and necking is also prone to breakage, generating a large number of satellite droplets (<50 μm) with poor sphericity. Conversely, the smaller the drop height, the shorter the total droplet descent time, requiring a higher mold closing rate to complete mold closing before the droplet solidifies prematurely upon contact with the template. However, the drop height cannot be too small, as this would result in insufficient pre-cooling in the air, high droplet superheat, large local temperature peaks and excessively high heat flux density after impact, leading to localized ablation, deformation, and shortened lifespan of the template.

[0056] It should be noted that the cooling rate of traditional amorphous solder fabrication technology is generally lower than 10. 5 K / s is insufficient to reach the critical cooling rate for the formation of amorphous tin-based alloys, making it even more difficult to stably prepare high-purity amorphous phases, resulting in a low amorphous rate.

[0057] In order to break through the upper limit of cooling rate of traditional processes and achieve ≥10 6 Ultra-high-speed cooling at K / s ensures the uniformity of the alloy melt cooling process, avoids local crystallization, and guarantees the stable and efficient formation of the amorphous phase. This invention employs a high-speed extrusion-forced heat exchange technology using a double-sided liquid-cooled copper template with embedded microchannels to extrude and cool the alloy droplets at ultra-high speed. During the cooling process, the contact area between the alloy droplets and the cooling template is increased by 5-10 times through extrusion, greatly enhancing the heat exchange efficiency.

[0058] Specifically, in step S3, the conditions for extruding and cooling the alloy droplets using a double-sided liquid-cooled copper template include: a temperature of -10 to 10 ℃, a pressure of 10 to 50 MPa (preferably 15 to 40 MPa), a mold closing rate of 5 to 12 m / s, a holding time of 1 to 5 ms (preferably 1 to 3 ms), and a mold opening rate of 4 to 8 m / s. By controlling the cooling temperature and extrusion pressure during the extrusion cooling process, this invention enables the alloy droplets to cool from the liquid phase to below the glass brick transition temperature in a short time (1 to 5 ms), with a stable cooling rate ≥10. 6 K / s, breaking through the upper limit of cooling rate in traditional processes.

[0059] More specifically, this invention uses a low-temperature medium, such as low-temperature silicone oil, anhydrous ethanol, or ethylene glycol aqueous solution, as a circulating cooling medium by introducing a low-temperature medium into the embedded microchannels of the double-sided liquid-cooled copper template. The cooling temperature is controlled within the range of -10 to 10°C, which can be -10°C, -5°C, 0°C, 5°C, or 10°C. The lower the cooling temperature, the lower the surface temperature of the template, which improves the overall heat exchange capacity and further increases the cooling rate. This is beneficial for improving the amorphous formation ability and increasing the proportion of amorphous phase. However, the temperature cannot be too low. If the cooling temperature is too low, the cooling intensity is too high, resulting in local overcooling. The surface layer of the melt solidifies rapidly, and the internal fluidity deteriorates, causing molding defects.

[0060] It should be noted that during the extrusion cooling process of the alloy droplets, the alloy droplets are made ultrathin through mechanical extrusion, which greatly increases the heat exchange area. Combined with double-sided liquid cooling, bidirectional forced heat exchange is achieved, breaking through the upper limit of heat exchange efficiency of traditional unidirectional cooling.

[0061] Specifically, in step S3, the extrusion pressure used in the extrusion cooling process is 10~50 MPa, which can be 10MPa, 15MPa, 20MPa, 25MPa, 30MPa, 35MPa, 40MPa, 45MPa, or 50MPa, preferably 15~40 MPa. If the extrusion pressure is too low, it will lead to poor contact between the droplet and the copper plate, high interfacial thermal resistance, a sharp drop in cooling rate, a significant decrease in amorphous ratio, and substandard thickness of the amorphous sheet after cooling and forming, affecting uniformity. If the extrusion pressure is too high, it will lead to excessive droplet extension, edge flash, and excessively thin thickness, causing droplet splashing and sheet breakage. The melt is also prone to sticking to the mold, causing tearing. In addition, the copper plate is subjected to excessive thermomechanical stress, which can easily cause warping, microcracks, and shorten its lifespan. An appropriate extrusion pressure can drastically reduce the thickness of the alloy droplet to 0.1~0.3 mm, increasing the contact area between the droplet and the cooling template by 5~10 times, greatly enhancing the heat exchange efficiency.

[0062] It should be noted that, in order to ensure that the alloy droplets can be completely cooled and solidified, and to prevent excessive internal stress or even brittle cracking of the sheet caused by over-cooling of the droplets, the present invention needs to limit the holding time of extrusion cooling.

[0063] Specifically, in step S3, the holding time of the alloy droplet at a temperature of -10~10℃ and a pressure of 10~50 MPa is 1~5ms, which can be 1ms, 2ms, 3ms, 4ms, or 5ms, preferably 1~3ms. If the holding time is too short, the droplet will not solidify completely, the thickness of the central liquid rebound will be uneven, the edges will warp, and the surface will have pits / wrinkles, resulting in a decrease in amorphous rate, an increase in crystalline phase, and easy sticking to the mold, causing tearing. If the holding time is too long, the copper mold will accumulate heat, the working surface temperature will continue to rise, the droplet will be over-cooled, the internal stress will be too high, it will be easy to crack brittlely, and the production efficiency will be reduced.

[0064] It should be noted that during the extrusion cooling of the alloy droplets using a double-sided liquid-cooled copper template, in addition to the cooling temperature, extrusion pressure, and holding time affecting the cooling rate and the amorphous ratio of the sheet, the mold closing rate and mold opening and resetting rate of the double-sided liquid-cooled copper template also affect the cooled amorphous sheet.

[0065] Specifically, in step S3, the closing rate of the double-sided liquid-cooled copper template is 5~12 m / s, which can be 5m / s, 6m / s, 7m / s, 8m / s, 9m / s, 10m / s, 11m / s, or 12 m / s, preferably 7~10 m / s. If the closing rate is too high, the melt will splash violently around the template, forming a large number of irregular flashes and fragments, reducing the yield of the finished sheet by more than 30%, and the cooling rate at the flashes will be uneven, easily leading to local crystallization. If the closing rate is too low, a crystalline hard shell will first form on the surface of the droplet, which will break during subsequent extrusion, causing the unsolidified melt inside to overflow, forming irregular protrusions and depressions, resulting in extremely poor sheet flatness; the prolonged closing time will reduce the overall cooling rate of the droplet to 10 m / s. 6 Below K / s, the precipitation of Sn-Cu brittle intermetallic compounds cannot be suppressed, and the amorphous rate of the finished product will drop sharply to below 60%, completely losing the performance advantages of amorphous solder.

[0066] Specifically, in step S3, the mold opening and resetting rate of the double-sided liquid-cooled copper template is 4~8 m / s, which can be 4m / s, 4.5m / s, 5m / s, 5.5m / s, 6m / s, 6.5m / s, 7m / s, 7.5m / s, or 8 m / s, preferably 5.5~6.5 m / s. If the mold opening and resetting rate is too high, the sheet will tear from the template, forming a large number of edge cracks, missing corners, and fragments; in severe cases, the sheet will shatter into dozens of small pieces, and the yield of the finished product will decrease by more than 40%. If the mold opening and resetting rate is too low, the contact time between the amorphous sheet and the high-temperature copper template will exceed 5ms, and the heat accumulation on the template surface will cause the sheet temperature to rise back to above the glass transition temperature (Tg≈120℃), triggering the crystallization transformation of the amorphous phase. The amorphous rate of the finished product will plummet to below 70%, and the crystallized phase will mainly be brittle Sn-Cu intermetallic compounds, which will severely degrade the creep resistance of the solder.

[0067] It should be noted that, by adjusting the extrusion cooling process and conditions, the present invention achieves a stable cooling rate of ≥10. 6 K / s, breaking through the upper limit of cooling rate in traditional processes, enables alloy droplets to be cooled to below the glass transition temperature in a very short time (1~5 ms) to promote the uniform and stable formation of the amorphous phase; and enables precise control of the size (such as thickness) of the amorphous alloy sheet produced.

[0068] Specifically, in step S3, the cooling rate of the extrusion cooling is 1×10⁻⁶. 6 ~1×10 7 K / s, can be 1×10 6 K / s, 1.5×10 6 K / s, 2×10 6 K / s, 2.5×10 6 K / s, 3×106 K / s, 3.5×10 6 K / s, 4×10 6 K / s, 4.5×10 6 K / s, 5×10 6 K / s, 5.5×10 6 K / s, 6×10 6 K / s, 6.5×10 6 K / s, 7.5×10 6 K / s, 8×10 6 K / s, 8.5×10 6 K / s, 9×10 6 K / s, 9.5×10 6 K / s, 1×10 7 K / s, the optimal range for industrial mass production is 2×10 6 ~5×10 6 K / s. If the cooling rate is too fast (greater than the upper limit of 1×10⁻⁶), it will be within the maximum range. 7 When the droplet solidifies prematurely on one side upon contact with the template (K / s), uniform ultra-thin extrusion cannot be achieved, resulting in problems such as sheet breakage, edge defects, and severe thickness unevenness, leading to a significant decrease in yield. Furthermore, if the extrusion cooling rate of this invention falls below the critical threshold for the formation of amorphous tin-based alloys (<10 K / s), it will cause further problems. 6 The cooling time was too long (K / s), which could not suppress the precipitation of the brittle Sn-Cu phase. The amorphous rate of the finished product dropped significantly, and local crystallization and crystalline residue in the core appeared, which could not meet the performance requirements of high-end packaging at all.

[0069] Specifically, in step S3, the thickness of the amorphous alloy sheet obtained by extrusion cooling is 0.1~0.3 mm, which can be 0.1 mm, 0.15 mm, 0.20 mm, 0.25 mm, or 0.30 mm. This ultra-thin thickness range of 0.1~0.3 mm, combined with double-sided liquid cooling forced heat exchange, allows the cooling rate to be stably controlled at 2×10⁻⁶. 6 ~5×10 6 The industrial optimal range of K / s satisfies the critical cooling rate (≥1×10⁻⁶) for the amorphous formation of Sn-Ag-Cu-RE alloys. 6 This design achieves the required K / s temperature while avoiding the defects caused by extreme cooling. At this thickness, the temperature gradient from the surface to the center of the sheet is <50℃ / mm, enabling uniform amorphization across the entire cross-section with a stable amorphous ratio ≥95%, preventing residual crystalline phase in the core. If the thickness of the amorphous alloy sheet is <0.1 mm, the cooling rate will exceed 1×10⁻⁶. 7At the process limit of K / s, a dense crystalline shell forms the instantaneously upon droplet contact with the template (<0.1ms). During subsequent die-clamping and extrusion, the shell cannot spread evenly, resulting in brittle fracture. Unsolidified melt overflows from the cracks, forming severe burrs and fragments in a petal-like pattern, causing the sheet yield to plummet to below 20%. When the thickness is >0.3mm, the cooling rate of the sheet core drops below 1×10⁻⁶. 6 At the critical value of K / s, atoms have enough time for long-range diffusion, precipitating brittle Sn-Cu intermetallic compounds (such as Cu6Sn5). This forms a shell-core structure with an amorphous surface and a crystalline core, reducing the overall amorphous rate to below 60%, completely losing the creep resistance and high-temperature resistance advantages of amorphous solders.

[0070] It should be noted that, in order to obtain amorphous powder with the target particle size, the present invention requires the amorphous flakes to be crushed and graded.

[0071] Specifically, in step S4, the amorphous alloy sheet is crushed and sieved; to avoid oxidation of the surface of the newly formed powder during the crushing process, the crushing step is carried out in a liquid nitrogen low-temperature environment.

[0072] More specifically, the prepared amorphous thin sheets are placed in a high-energy ball mill and subjected to low-temperature ball milling in a liquid nitrogen environment. The ball-to-material mass ratio is controlled at 10:1 to 15:1, the rotation speed is 300 to 320 rpm, and the ball milling time is 2 to 2.5 h, so that the amorphous thin sheets are fully broken into powder.

[0073] According to some preferred embodiments of the present invention, the grinding balls of the present invention are YG8 tungsten cobalt cemented carbide grinding balls, which have high hardness, extremely strong wear resistance, no brittle cracking under liquid nitrogen low temperature environment, extremely low wear, and will not introduce harmful impurities such as Fe and Cu. They perfectly match the high purity, low oxygen, and low impurity requirements of electronic grade solders, and are the optimal choice of the present invention.

[0074] According to some preferred embodiments of the present invention, the ball-to-material mass ratio in the grinding process can be any value within the range of 10:1 to 15:1, such as 10:1, 11:1, 12:1, 13:1, 14:1, 15:1. Within this range, a balance between the impact crushing and fine grinding effects of the grinding balls can be achieved. Within a specified time of 2 to 2.5 hours, thin flakes can be stably crushed to a target particle size of ≤50μm, with a narrow particle size distribution and no over-grinding. Simultaneously, it avoids the introduction of impurities and temperature rise crystallization caused by empty ball impacts. Combined with a liquid nitrogen environment, it can stably maintain the desired particle size. The amorphous content of the product is ≥95%. If the ball-to-material ratio is too large (>15:1), there are too many grinding balls and insufficient material filling, which intensifies the empty collision of grinding balls, causes a surge in wear and introduces a large number of impurities, resulting in severe over-grinding. The proportion of ultrafine powder (<5μm) exceeds 30%, the powder has extremely poor flowability, cannot be adapted to electronic packaging printing processes, and energy consumption increases significantly. If the ball-to-material ratio is too small (<10:1), there are not enough grinding balls, the crushing capacity is severely insufficient, and fine grinding cannot be completed within the specified time. The proportion of coarse particles >50μm is high, the powder yield is inefficient, material accumulation leads to uneven grinding, and the particle size distribution is extremely wide with poor consistency.

[0075] According to some preferred embodiments of the present invention, the ball mill rotation speed can be any value within the range of 300~320 rpm, such as 300 rpm, 305 rpm, 310 rpm, 315 rpm, and 320 rpm. Rotation speeds within this range ensure sufficient crushing force without causing the grinding balls to stick to the wall due to centrifugal force and spin idly. Combined with the liquid nitrogen environment, there is no significant temperature rise, completely avoiding amorphous phase crystallization, and the powder particle size uniformity is good. If the rotation speed is too high (>320 rpm), the grinding balls will stick to the wall and rotate with the cylinder due to centrifugal force, losing their impact crushing effect, resulting in a sharp drop in crushing efficiency. The friction between the grinding balls and the cylinder wall will cause a significant temperature rise, leading to amorphous phase crystallization, increased oxygen content, severe equipment vibration, and a significantly increased failure rate. If the rotation speed is too low (<300 rpm), the grinding balls will not rise sufficiently, only sliding without effective impact, resulting in severely insufficient crushing capacity. The target particle size cannot be reached within the specified time, leading to excessive coarse particles; the material will be ground unevenly, resulting in extremely poor batch consistency.

[0076] According to some preferred embodiments of the present invention, the ball milling time can be any value within 2 to 2.5 hours. Within this time range, the ball-to-material ratio and rotation speed can be adjusted to completely crush the flakes to the target particle size, stably control the D50 at 25 to 40 μm, and remove any coarse particles. At the same time, it avoids the temperature rise, crystallization, oxidation, and impurity introduction caused by long-term ball milling, and stably ensures that the amorphous rate of the finished product is ≥95% and the oxygen content is ≤100ppm. Excessive grinding time (>2.5h) results in severe over-grinding, excessive ultrafine powder content, deteriorated powder flowability, and cumulative temperature rise during ball milling. Even in a liquid nitrogen environment, localized amorphous phase crystallization can occur, leading to increased ball wear, excessive impurities and oxygen content, and wasted energy. For example, a large amount of ultrafine powder with a diameter <5μm can be produced, accounting for more than 35%. The specific surface area of ​​ultrafine powder is 5 to 10 times that of normal powder, making it extremely easy to oxidize, causing the oxygen content of the finished product to soar to over 150ppm. Insufficient grinding time (<2h) results in insufficient crushing, with a large number of thin flakes not being fully refined, excessive coarse particles, extremely low powder yield, and a wide particle size distribution. For example, the proportion of coarse particles >50μm exceeds 40%, and D50 will deviate from the target range (25~40 μm) to 50~70μm. The wide particle size distribution range, with a width >1.8mm, far exceeds the qualified width value <1.2mm, which cannot meet the requirements of electronic packaging processes. Secondary screening is required, resulting in a significant decrease in production efficiency.

[0077] The ball milling process of this invention utilizes a low-temperature liquid nitrogen environment (full immersion in liquid nitrogen, material temperature ≤ -196℃), which keeps the amorphous alloy sheets in a brittle state, making them easy to break upon impact and preventing cold welding agglomeration caused by plastic deformation. The consistently low temperature completely suppresses the temperature rise during ball milling, preventing the crystallization of the amorphous phase. Simultaneously, it isolates oxygen, preventing oxidation of the newly formed surface after breakage, which is the core guarantee for low-oxygen, high amorphous ratio control. If the temperature is too high (insufficient liquid nitrogen, material temperature > -100℃), the toughness of the alloy sheets increases, making breakage more difficult and easily leading to cold welding agglomeration and the formation of large particles; frictional temperature rise causes the amorphous phase to crystallize, significantly reducing the amorphous ratio; and oxidation of the newly formed surface intensifies, resulting in excessive oxygen content.

[0078] This invention employs a double-sided liquid-cooled copper template for ultra-high-speed forced heat exchange of alloy droplets, achieving rapid cooling and overcoming the technical bottlenecks of traditional processes. This promotes the uniform and stable formation of the amorphous phase, increasing the amorphous ratio of the brazing filler metal. The entire preparation process utilizes inert protection to achieve low-oxygen control, ensuring the oxygen content in the resulting amorphous tin alloy brazing filler metal is <100 ppm. Trace rare-earth modification ensures that while enhancing amorphous formation capability, it also prevents a decrease in the brazing performance and electrical and thermal conductivity of the brazing filler metal. Furthermore, the modular design of this invention simplifies the preparation process, eliminating the need for high-precision, high-cost specialized equipment used in traditional processes. This significantly simplifies the equipment structure, reducing equipment investment and maintenance costs by more than 40% compared to traditional gas atomization methods. The process also boasts strong continuity, high production efficiency, and is easily scalable for large-scale industrial production. This invention enables the stable and reliable preparation of a high-amorphous-ratio, low-oxygen-content, controllable-particle-size, low-cost, and mass-producible amorphous tin alloy brazing filler metal powder.

[0079] The present invention also provides an amorphous tin alloy solder powder, wherein the solder powder is prepared by the preparation method described above.

[0080] Specifically, by mass percentage, the chemical composition of the amorphous tin alloy solder is Sn 93.0%~99.8%, Ag 0.1%~4.5%, Cu 0.1%~1.5%, and rare earth elements 0.1%~0.5%.

[0081] More specifically, the rare earth element is at least one of Ce, Y, La, and Nb. It can be Ce, Y, La, Nb, Ce and Y, Ce and La, Ce and Nb, preferably Ce and Y.

[0082] More specifically, the solder powder has a particle size ≤50 μm, preferably D50 of 25~40 μm, an amorphous content ≥95%, and an oxygen content <100 ppm. The amorphous tin alloy solder of this invention has a high amorphous content, up to 97.5%, fully meeting the performance requirements of high-end electronic packaging for amorphous solders; the oxygen content of the finished powder can be stably controlled below 100 ppm, significantly improving the wettability and interfacial bonding strength of the solder, greatly enhancing welding reliability and connection performance; trace rare earth element doping enhances the solder's creep resistance and high-temperature resistance, benefiting its long-term service stability; the narrow particle size distribution and good morphological consistency can meet the differentiated requirements of solder powder characteristics for different high-end electronic packaging scenarios; the preparation process and equipment are simple, the cost is low, and it is conducive to large-scale industrial mass production.

[0083] The technical solution of the present invention will be further explained and illustrated below through specific embodiments and comparative examples.

[0084] The purity of the metal raw materials is ≥99.99%.

[0085] Example 1 A method for preparing amorphous tin alloy Sn 96.5%-3.0%Ag-0.5%Cu (numerical expression of mass percentage content) solder powder includes the following steps: S1 is prepared by weighing high-purity metals Sn, Ag, and Cu (purity ≥ 99.99%) according to the mass ratio of Sn 96.5% - 3.0% Ag - 0.5% Cu, and mixing them; the mixed raw materials are then subjected to a vacuum of 1.0 × 10⁻⁶. - Pre-treat the raw material under an argon atmosphere (gas purity ≥ 99.999%, pressure 0.1 MPa) for 30 min; then heat the pre-treated raw material to 520℃ in an induction heating furnace at a heating rate of 20℃ / min under an argon atmosphere (gas purity ≥ 99.999%, pressure 0.1 MPa), and hold for 30 min to obtain a uniform alloy melt. S2 disperses the alloy melt under the following conditions: a melt superheat of 50°C (570°C), a liquid column height of 70 mm, a nozzle orifice diameter of 0.5 mm, a vibration frequency of 50 kHz, and an amplitude of 0.04 mm, resulting in alloy droplets with a diameter of 1.0 ~ 1.2 mm and a sphericity of 92%. S3 uses a double-sided liquid-cooled copper template to extrude and cool the alloy droplets obtained in step S2. The conditions include: using a low-temperature silicone oil medium to control the cooling temperature of the liquid-cooled copper template to -5℃; a mold closing pressure of 30MPa; a mold closing speed of 5.5m / s; a holding time of 2ms; and a mold opening rate of 5.5m / s. The cooling rate is monitored in real time, and the measured cooling rate is 2.5×10⁻⁶. 6 K / s, the alloy droplet cools to below the glass transition temperature within 3ms, forming an amorphous sheet with a thickness of 0.2mm; S4 involves low-temperature ball milling of the amorphous thin film obtained in step S3, with the following conditions: immersing the amorphous thin film in liquid nitrogen, controlling the ball-to-material mass ratio at 10:1, the rotation speed at 300 rpm, and the ball milling time at 2 h, so that the amorphous thin film is fully broken into powder and passed through a 200-mesh standard sieve to obtain amorphous tin alloy Sn-3.0Ag-0.5Cu solder powder.

[0086] Testing revealed that the Sn-3.0Ag-0.5Cu brazing filler powder had a particle size of less than 50 μm, a D50 of 28 μm, an amorphous content of 96.2%, and an oxygen content of 82 ppm, determined using inert gas fusion-infrared absorption spectrometry. The powder obtained in Example 1 was characterized structurally: XRD (Cu-Kα, 40 kV, 40 mA, 2θ = 10°~90°) spectra (e.g., ...). Figure 6The DSC (10 K / min, N2) curve (as shown in Figure 7) did not show sharp Bragg diffraction peaks for Sn, Ag3Sn, Cu6Sn5, etc. Only a broadened diffuse scattering pattern (bun peak) near 2θ≈30° was observed. Quantitative calculation using full-spectrum fitting showed that the crystalline phase ratio was ≤4.8%, i.e., the amorphous rate was ≥95.2%. The glass transition step Tg≈388 K and the subsequent exothermic crystallization peak Tx≈426 K were identifiable in the supercooled liquid phase region. x ≈38 K further confirms its amorphous nature. TEM-HRTEM observation results (e.g.) Figure 8 As shown, no regular lattice fringes were observed, and SAED showed continuous halos, consistent with the XRD findings.

[0087] Comparative Example 1 Sn-3.0Ag-0.5Cu solder powder was prepared using a conventional gas atomization method, comprising: S1 uses the same process steps as step S1 in Example 1 to prepare the alloy melt; S2 uses conventional gas atomization powder making equipment, and performs atomization powder making under argon protection. The atomization pressure is 8MPa and the melt superheat is 50℃. S3 employs a high-pressure, high-purity argon counter-current quenching cooling process to cool atomized powder, with a cooling rate of 8×10⁻⁶. 4 K / s, sieve, collect powder products with a particle size of less than 50μm.

[0088] The brazing filler powder prepared in Comparative Document 1 has an amorphous content of 12.3%, is predominantly crystalline, and has an oxygen content of 320 ppm; the finished powder collected by sieving has a nominal particle size of <50 μm and a median volume diameter D. 50 The particle size is 35 μm, and the overall particle size is slightly coarser than that of Example 1 (D). 50 =28 μm); The XRD pattern (Cu-Kα, 40 kV, 40 mA, 2θ=10°~90°) of Comparative Example 1 shows typical characteristics of crystalline alloy; Under the test conditions of 10 K / min and high-purity N2 protection, the DSC curve of Comparative Example 1 does not have a clear and identifiable glass transition step (Tg) - because the proportion of amorphous phase is too low, the heat capacity change signal corresponding to the glass transition is completely covered by a large amount of crystalline matrix, and the characteristic step cannot be identified. The overall thermal behavior is not significantly different from that of ordinary crystalline tin-based solder; High-resolution transmission electron microscopy (HRTEM) observation shows that the microstructure of Comparative Example 1 is dominated by crystalline phase.

[0089] Examples 2-9, Comparative Examples 2-13 The same preparation method as in Example 1 was used, except that the process conditions were changed to address key factors affecting the amorphous content, oxygen content, and powder particle size / morphology of the final brazing alloy. These included the amount and type of rare earth elements added, vibration dripping process conditions (such as superheat, frequency, and nozzle orifice diameter to change the alloy droplet size, uniformity, and sphericity), extrusion cooling process conditions (such as cooling temperature, pressure, and holding time to change the cooling rate and sheet thickness), and low-temperature crushing conditions. When these changes were made within the protected range, Examples 2-9 were established, and the products obtained met the requirements. When the changes were made outside the protected range, Comparative Examples 2-13 were established, and the products obtained did not meet the requirements. The preparation process conditions and product performance are shown in Tables 1 and 2, respectively.

[0090] Table 1. Preparation process conditions of Examples 1-9 and Comparative Examples 1-13

[0091] Table 2 Product performance of Examples 1-9 and Comparative Examples 1-13

[0092] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing amorphous tin alloy solder powder, characterized in that, Includes the following steps: S1 melts the raw materials of the amorphous tin alloy brazing filler to obtain an alloy melt; S2 disperses the alloy melt to obtain alloy droplets; S3 uses a double-sided liquid-cooled copper template to extrude and cool the alloy droplets to obtain amorphous alloy sheets; S4 crushes and sieves the amorphous alloy sheet; Steps S1-S4 are all performed under an inert atmosphere.

2. The preparation method according to claim 1, characterized in that, The chemical composition of the amorphous tin alloy solder, by mass percentage, is Sn 93.0%~99.8%, Ag 0.1%~4.5%, Cu 0.1%~1.5%, and rare earth elements 0.1%~0.5%.

3. The preparation method according to claim 2, characterized in that, The rare earth element is at least one of Ce, Y, La, and Nb.

4. The preparation method according to claim 1, characterized in that, In step S2, the alloy melt is dispersed using a vibration dripping method. Specific conditions include: a melt superheat of 30-80°C, a liquid column height of 30-120 mm, a nozzle orifice diameter of 0.2-1.0 mm, and a vibration frequency of 25-67 kHz.

5. The preparation method according to claim 1, characterized in that, In step S2, the diameter of the alloy droplet is 0.5~2.0 mm and the sphericity is ≥0.

90.

6. The preparation method according to claim 1, characterized in that, In step S3, the conditions for extruding and cooling the alloy droplets using a double-sided liquid-cooled copper template include: a temperature of -10 to 10 ℃, a pressure of 10 to 50 MPa, a mold closing rate of 5 to 12 m / s, a holding time of 1 to 5 ms, and a mold opening rate of 4 to 8 m / s.

7. The preparation method according to claim 1, characterized in that, In step S3, the cooling rate of the extrusion cooling is 1×10⁻⁶. 6 ~1×10 7 K / s.

8. The preparation method according to claim 1, characterized in that, In step S3, the thickness of the amorphous alloy sheet is 0.1~0.3 mm.

9. An amorphous tin alloy solder powder, characterized in that, The brazing powder is prepared by the preparation method according to any one of claims 1-8.

10. The brazing powder according to claim 9, characterized in that, The brazing filler powder has a particle size ≤50 μm, an amorphous content ≥95%, and an oxygen content <100ppm.

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