Brazing filler metal composition of integrated waveguide LCP and preparation method and application of brazing filler metal composition

Abstract

The invention discloses a brazing filler metal composition of an integrated waveguide LCP (Liquid Crystal Polymer) as well as a preparation method and application of the brazing filler metal composition, and the brazing filler metal composition comprises the following components in percentage by mass: 83.0-92.0% of In, 6.0-8.0% of Sn, 2.0-4.0% of Ag, 0.1-8.0% of M and the balance of inevitable impurities. And M is Al2O3 or Mo. The brazing filler metal alloy composition has high welding binding force and electrocorrosion performance, and a foundation is laid for wide application of the brazing filler metal alloy composition in the field of electronic packaging.

Description

Technical Field

[0001] This invention relates to the field of metal materials technology, and in particular to a solder composition for integrated waveguide LCP, its preparation method and application. Background Technology

[0002] In critical fields such as aerospace, high-reliability electronic packaging (e.g., optoelectronic devices, power devices, RF components), advanced energy systems (e.g., nuclear energy, fusion devices, high-temperature fuel cells), and precision military equipment, reliable connections between devices place extremely stringent requirements on material performance. Indium (In)-based solders, with their excellent physicochemical properties, play a vital role in these fields. Specifically, Indium-based solders typically exhibit excellent low-temperature ductility and plasticity, enabling them to fill and connect complex shapes at lower temperatures, reducing welding thermal stress, and are particularly suitable for heat-sensitive components. Good electrical and thermal conductivity ensures the high efficiency of connection points in electrical signal transmission and heat dissipation, meeting the needs of high-frequency, high-power devices. Inherent corrosion resistance; Indium itself has good chemical stability in various environmental media, helping to improve the long-term environmental tolerance of connection points. Excellent wetting properties; exhibiting good spreadability and interfacial bonding ability to various substrates (e.g., gold, silver, copper, nickel, ceramic metallization layers, etc.), facilitating the formation of dense, defect-free solder joints. Based on the above comprehensive advantages, indium-based solders (such as alloy systems of In, In-Ag, In-Sn, In-Bi, etc.) have become indispensable connection materials in high-end application scenarios such as flip-chip bonding of microelectronic chips, laser / detector packaging, infrared focal plane array interconnection, low-temperature superconducting magnet connectors, and precision component assembly of spacecraft.

[0003] However, as the requirements for device performance, reliability, and service life in these cutting-edge fields continue to increase, the existing indium-based solder system has gradually revealed its inherent limitations, mainly in the following key aspects: insufficient mechanical properties, especially strength and creep resistance under high / low temperature environments; the risk of electrochemical corrosion, accelerated oxidation, or selective corrosion, affecting the electrical performance and structural integrity of the connection points; although the addition of alloying elements (such as Ag, Sn, Bi) can improve strength or lower melting point to some extent, it often comes at the cost of sacrificing its excellent low-temperature ductility, wettability, or conductivity, making it difficult to achieve synergistic optimization of various key properties. Summary of the Invention

[0004] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. Therefore, the object of the present invention is to provide a solder composition for integrated waveguide LCP, a method for preparing the same, and its applications.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] In a first aspect, the present invention provides a brazing alloy composition containing, by weight percentage, 83.0 to 92.0% In, 6.0 to 8.0% Sn, 2.0 to 4.0% Ag, 0.1 to 8.0% M and the balance being unavoidable impurities; M being Al2O3 or Mo.

[0007] In this invention, adding aluminum oxide or molybdenum to the indium tin silver alloy can refine the alloy grains and strengthen the alloy structure, thereby significantly improving the alloy's corrosion resistance and weldability.

[0008] In some embodiments of the present invention, the brazing alloy composition contains, by mass percentage, 84.0–91.0% In, 6.5–7.5% Sn, 2.5–3.5% Ag, 1.0–6.0% M, and the balance being unavoidable impurities; M is Al2O3 or Mo.

[0009] In some embodiments of the present invention, the brazing alloy composition contains, by mass percentage, 85.0–90.0% In, 6.8–7.2% Sn, 2.8–3.2% Ag, 1.0–5.0% M, and the balance being unavoidable impurities; M is Al2O3 or Mo.

[0010] In some embodiments of the present invention, the brazing alloy composition contains, by mass percentage, 86.0–90.0% In, 6.9–7.1% Sn, 2.9–3.1% Ag, 1.0–4.5% M, and the balance being unavoidable impurities; M is Al2O3 or Mo.

[0011] In some embodiments of the present invention, the brazing alloy composition contains, by mass percentage, 86.0-89.0% In, 7.0% Sn, 3.0% Ag, 1.0-4.0% M and the balance being unavoidable impurities; M is Al2O3 or Mo.

[0012] In some embodiments of the present invention, when M is Al2O3, the Al2O3 is dispersed; the dispersed distribution is a physical dispersion. In the present invention, alumina is dispersed in the matrix, acting as a heterogeneous nucleation site, inducing a preferred arrangement of crystal orientations; hindering dislocation movement, pinning grain boundary migration, and preventing recrystallization, thereby refining the grains and improving the strength and hardness of the material.

[0013] In some embodiments of the present invention, the average particle size of the Al2O3 is 10-100 nm, such as 15-80 nm, 20-70 nm, 30-50 nm, etc.

[0014] In some embodiments of the present invention, when M is Mo, Mo forms a MoSn2 phase; the MoSn2 phase is dispersed. In the present invention, Mo forms a high-melting-point MoSn2 phase in the matrix, which can effectively suppress grain boundary migration and nucleation phase coarsening, change the solidification behavior of the solder, refine the microstructure, significantly reduce the grain size of the solder, improve its strength and thermal stability.

[0015] In some embodiments of the present invention, the average particle size of the MoSn2 phase is 10-100 nm, such as 15-80 nm, 20-70 nm, 30-50 nm, etc.

[0016] A second aspect of the present invention provides a method for preparing the aforementioned brazing alloy composition, comprising the following steps:

[0017] Indium granules, tin granules, silver powder, and M powder are mixed according to the stated mass percentages to form a solder alloy composition.

[0018] In some embodiments of the present invention, indium granules, tin granules, silver powder and molybdenum powder or alumina powder are mixed, heated to melt, stirred and kept at the temperature, and then cooled to obtain the solder composition.

[0019] In some embodiments of the present invention, the heating temperature for melting is 250–300°C, and the heating time is 10–25 min.

[0020] In some embodiments of the present invention, the stirring rate is 250-350 rpm, and the stirring time is 0.5-5 min, such as 1-3 min.

[0021] In some embodiments of the present invention, the heat preservation time is 1 to 5 minutes, such as 2 to 4 minutes.

[0022] A third aspect of the present invention provides a solder sheet comprising the aforementioned solder alloy composition.

[0023] In some embodiments of the present invention, the average thickness of the solder sheet is 10 to 1000 μm, such as 50 to 500 μm, 80 to 400 μm, 90 to 300 μm, 100 μm, 200 μm, etc.

[0024] A fourth aspect of the present invention provides a method for preparing the aforementioned solder sheet, comprising the following steps:

[0025] The brazing alloy composition is rolled to obtain the brazing filler sheet.

[0026] In some embodiments of the present invention, the rolling process includes multi-pass rolling; the rolling process includes a reduction of 15-25% per pass (e.g., 18-2%, 19%, 20%, 21%).

[0027] A fifth aspect of the invention provides an electrical connection on a device component, comprising the aforementioned solder alloy composition.

[0028] In some embodiments of the present invention, the component includes any one of copper-clad laminate, silver paste glass, and copper foil.

[0029] In some embodiments of the present invention, the device includes any one of a microelectronic chip, a laser, a detector, an infrared focal plane array, a low-temperature superconducting magnet, or a spacecraft.

[0030] The beneficial effects of this invention are:

[0031] The solder alloy composition of the present invention has high welding strength and electro-corrosion performance, laying the foundation for its wide application in the field of electronic packaging.

[0032] The Mo-containing brazing alloy composition of the present invention also has good creep resistance.

[0033] The method for preparing the brazing alloy composition of the present invention is simple and easy to promote. Attached Figure Description

[0034] Figure 1 The image shows a metallographic micrograph of the solder alloy in Embodiment 1 of the present invention; wherein (a), (b), (c), (d), and (e) correspond to In 90 Sn7Ag3, In 89 Sn7Ag3(Al2O3), In 88 Sn7Ag3(Al2O3)2、In 87 Sn7Ag3(Al2O3)3、In 86 Microstructure of Sn7Ag3(Al2O3)4.

[0035] Figure 2 The image shows a scanning electron microscope (SEM) image of the solder alloy in Embodiment 1 of the present invention; wherein, (a) and (b) correspond to In 90 Microscopic images of Sn7Ag3 at 1000× and 5000× scanning electron microscopes; (c) and (d) correspond to In 88 Microscopic images of Sn7Ag3(Al2O3)2 under 1000× and 5000× scanning electron microscopes.

[0036] Figure 3 The above are EDS energy dispersive spectroscopy (EDS) analyses of the solder alloy in Example 1 of this invention; wherein, (a) is a selected area analysis of the solder sheet without alumina, and (b) is the solder sheet with alumina. 88 Selective region analysis of Sn7Ag3(Al2O3)2.

[0037] Figure 4 The above are EBSD analysis diagrams of the solder alloy in Example 1 of this invention; where (a1) and (a2) are the IDF+GB and PH diagrams of the solder without alumina; (b1) and (b2) are the results of the solder with alumina. 88 IDF+GB and PH plots of Sn7Ag3(Al2O3)2.

[0038] Figure 5 The XRD diffraction patterns of the solder alloy in Embodiment 1 of the present invention are shown below; where (a), (b), (c), (d), and (e) correspond to In 90 Sn7Ag3, In 89 Sn7Ag3(Al2O3), In 88 Sn7Ag3(Al2O3)2、In 87 Sn7Ag3(Al2O3)3、In 86 XRD diffraction pattern of Sn7Ag3(Al2O3)4.

[0039] Figure 6 This is a tensile force curve of the solder alloy in Embodiment 1 of the present invention; wherein (a), (b), (c), (d), and (e) correspond to In 90 Sn7Ag3, In 89 Sn7Ag3(Al2O3), In 88 Sn7Ag3(Al2O3)2、In 87 Sn7Ag3(Al2O3)3、In 86 Tensile strength curve of Sn7Ag3(Al2O3)4.

[0040] Figure 7 The results are the electro-corrosion test results of the solder alloy in Example 1 of this invention; where (a), (b), (c), (d), and (e) correspond to In 90 Sn7Ag3, In 89 Sn7Ag3(Al2O3), In 88 Sn7Ag3(Al2O3)2、In 87 Sn7Ag3(Al2O3)3、In 86 Tafel curve of Sn7Ag3(Al2O3)4.

[0041] Figure 8 These are microstructure images of the solder alloy after electrochemical corrosion in Example 1 of this invention; where (a), (b), (c), (d), and (e) correspond to In 90 Sn7Ag3, In 89 Sn7Ag3(Al2O3), In 88 Sn7Ag3(Al2O3)2、In87 Sn7Ag3(Al2O3)3、In 86 Microstructure of Sn7Ag3(Al2O3)4 after etching.

[0042] Figure 9 The image shows a metallographic micrograph of the solder alloy in Embodiment 2 of the present invention; wherein (a), (b), (c), (d), and (e) correspond to In 90 Sn7Ag3, In 89 Sn7Ag3Mo, In 88 Sn7Ag3Mo2, In 87 Sn7Ag3Mo3, In 86 Microstructure of Sn7Ag3Mo4.

[0043] Figure 10 The images shown are scanning electron microscope (SEM) images of the solder alloy in Embodiment 2 of the present invention; wherein, (a) and (b) correspond to In 90 Microscopic images of Sn7Ag3 at 500× and 10000× scanning electron microscopes; (c) and (d) correspond to In 88 Microscopic images of Sn7Ag3Mo2 at 500× and 10000× scanning electron microscopes.

[0044] Figure 11 The above are EDS energy dispersive spectroscopy (EDS) analysis diagrams of the solder alloy in Example 2 of this invention; wherein, (a) is the EDS energy dispersive spectroscopy analysis diagram of the solder sheet without alumina; and (b) is the EDS energy dispersive spectroscopy analysis diagram of the solder sheet with alumina. 88 EDS energy dispersive spectroscopy analysis of Sn7Ag3Mo2.

[0045] Figure 12 The above are EBSD analysis diagrams of the solder alloy in Embodiment 2 of the present invention; wherein, (a) and (b) correspond to In 90 IDF+GB and PH plots of Sn7Ag3; (c) and (d) correspond to In 88 IDF+GB and PH plots of Sn7Ag3Mo2.

[0046] Figures 13 to 18 The In alloy of Embodiment 2 of the present invention is respectively 90 Sn7Ag3, In 89 Sn7Ag3Mo, In 88 Sn7Ag3Mo2, In 87 Sn7Ag3Mo3, In 86 XRD patterns of Sn7Ag3Mo4 and a summary of XRD patterns.

[0047] Figure 19This is a tensile force curve of the solder alloy in Embodiment 2 of the present invention; wherein (a), (b), (c), (d), and (e) correspond to In 90 Sn7Ag3, In 89 Sn7Ag3Mo, In 88 Sn7Ag3Mo2, In 87 Sn7Ag3Mo3, In 86 Tensile strength curve of Sn7Ag3Mo4.

[0048] Figure 20 The results are the electro-corrosion test results of the solder alloy in Example 2 of this invention; where (a), (b), (c), (d), and (e) correspond to In 90 Sn7Ag3, In 89 Sn7Ag3Mo, In 88 Sn7Ag3Mo2, In 87 Sn7Ag3Mo3, In 86 Tafel curve of Sn7Ag3Mo4.

[0049] Figure 21 These are microstructure images of the solder alloy after electrochemical corrosion in Example 2 of this invention; where (a), (b), (c), (d), and (e) correspond to In 90 Sn7Ag3, In 89 Sn7Ag3Mo, In 88 Sn7Ag3Mo2, In 87 Sn7Ag3Mo3, In 86 Microstructure of Sn7Ag3Mo4 after etching. Detailed Implementation

[0050] The present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials, reagents, or apparatus used in the embodiments and comparative examples are all available from conventional commercial sources or can be obtained by existing technical methods. Unless otherwise specified, the test or experimental methods are conventional methods in the art.

[0051] Example 1

[0052] This embodiment prepares an indium-tin-silver alloy solder composition, and the specific process is as follows:

[0053] Using an electronic balance with an accuracy of 0.001g, press In (90-x) Sn7Ag3(Al2O3) x(x = 0, 1, 2, 3, 4 wt.%) Weigh out high-purity metal raw materials (indium granules ≥ 99.99%, tin granules ≥ 99.8%, silver powder 99.5%, alumina powder 99.9%), totaling 10g. Spread 0.1g of rosin powder evenly on the inner wall of a clean and dry quartz crucible as a release agent, then fill it with the mixed raw materials. Cover the surface with a 0.05g rosin protective layer, place it in an argon-protected box-type resistance furnace, set the temperature to 280℃ and hold for 18min. After removing it, mechanically stir it at 300rpm for 1min to ensure uniformity, then return it to the furnace and hold for 2min before pouring it onto an oxygen-free copper plate for rapid cooling. Subsequently, the material was ultrasonically cleaned with ethanol at 40kHz for 10 minutes, and then rolled in multiple passes (20% reduction per pass) through a twin-roll mill (200mm diameter) to a final thickness of 100±5μm. The rolling process was repeated 5-6 times to ensure uniform composition. Finally, the brazing filler sheet was ultrasonically cleaned again and then sealed for storage.

[0054] Experimental Example 1

[0055] This experimental example demonstrates the structural characterization and phase analysis of the solder composition prepared in Example 1. The specific process is as follows:

[0056] Microscopic metallographic analysis of brazing filler metal:

[0057] Nitric acid alcohol (HNO3-C2H5OH, 1:1 / v:v) was used as the etching solution. Etching and imaging were performed after solder polishing, and the resulting microscopic images are shown below. Figure 1 As shown.

[0058] Figure 1 (a), (b), (c), (d), and (e) correspond to In 90 Sn7Ag3, In 89 Sn7Ag3(Al2O3), In 88 Sn7Ag3(Al2O3)2、In 87 Sn7Ag3(Al2O3)3、In 86 Microstructure of Sn7Ag3(Al2O3)4.

[0059] The solder is soft, and during polishing, hard particles (SiC and / or Al2O3) inevitably embed and scratch the alloy, making it difficult to achieve a mirror finish. In the In-Sn-Ag system, the chemical properties of the In-rich phase and the Sn-Ag intermetallic compound (such as Ag3Sn) are relatively similar, and conventional nitric acid alcohol may not be able to effectively distinguish between the phases. At the same time, the poor wettability of Al2O3 with molten In (contact angle >120°) may inhibit the nucleation of the Sn-Ag phase through adsorption, resulting in a dispersed phase distribution.

[0060] SEM-EDS analysis of solder:

[0061] Figure 2 Scanning electron microscope (SEM) images of the brazing filler alloy are shown. (a) and (b) correspond to In... 90 Microscopic images of Sn7Ag3 at 1000× and 5000× scanning electron microscopes; (c) and (d) correspond to In 88 Microscopic images of Sn7Ag3(Al2O3)2 at 1000× and 5000× scanning electron microscopes. It can be seen that after the addition of alumina, the amount of the second phase is reduced, the microstructure becomes more uniform, and the defects are reduced.

[0062] To quantitatively determine the compositional difference between the precipitated second phase and the matrix phase, selected area energy dispersive spectroscopy (EDS) analysis was performed on both. The results are as follows: Figure 3 As shown. (a) is a selected area analysis of the solder sheet without alumina, and (b) is a solder sheet with alumina. 88 Selected area analysis of Sn7Ag3(Al2O3)2 shows that in (a) selected area A, the In content is 65.6 wt.% and the Ag content is 34.4 wt.%; in selected area B, the In content is 95.1 wt.% and the Sn content is 4.9 wt.%. This suggests that Ag and In form compounds that precipitate in a spherical shape in the solder, and these intermetallic compounds may be AgIn2 or Ag3In. Sn and In may form a solid solution or a low-melting-point eutectic structure as the matrix phase. In (b) selected area A, the In content is 64.5 wt.% and the Ag content is 35.3 wt.%; in selected area B, the In content is 93.8 wt.%, the Sn content is 5.9 wt.%, and the Ag content is 0.2 wt.%. The energy dispersive spectroscopy (EDS) spectrum indicates that after the addition of alumina to the solder, a small amount of Ag dissolves in the matrix. Alumina is usually added as a reinforcing phase or grain refiner, which may affect the microstructure of the alloy. As ceramic particles, Al₂O₃ can serve as a heterogeneous nucleation substrate during solidification, refining grains and shortening element diffusion paths. This may hinder Ag from aggregating to form coarse precipitates, resulting in some Ag atoms being confined within the matrix to form solid solutions.

[0063] Electron backscattering diffraction (EBSD) analysis of solder:

[0064] To further determine the orientation of each phase in the experimental solder, EBSD analysis was performed on the solder, yielding IDF+GB (antipolar grain boundary diagram) and PH (phase diagram) data as follows: Figure 4 As shown. (a1) and (a2) are the IDF+GB and PH graphs without alumina solder; (b1) and (b2) are the graphs with alumina solder. 88The IDF+GB and pH diagrams of Sn7Ag3(Al2O3)2 show that in (a1), there is no concentrated color distribution in the same area, indicating no obvious orientation deviation. The uniform color distribution in the IDF diagram suggests random grain orientation without a clear preferred orientation. However, after adding alumina (b1), a clearly visible red-dominated color concentration region is observed, indicating strong... <001> Texture. The IDF plot shows a strong red-dominated pattern. <001> Texture indicates that alumina induces a preferred arrangement of crystal orientations, resulting in heterogeneous nucleation. Alumina particles act as a nucleation substrate, promoting grain growth along specific directions (e.g., ...). <001> Preferential growth. The interfacial energy difference between alumina and the matrix may be reduced. <001> The total energy of the oriented grains promotes their preferential formation. Meanwhile, analysis in Figure (a1) reveals that small-angle grain boundaries (2°–10°) account for approximately 28.2 wt.%, while large-angle grain boundaries (>10°) account for approximately 71.8 wt.%. The high proportion of large-angle grain boundaries reflects coarser grains or the presence of deformed structures with incomplete recrystallization. In Figure (b1), the corresponding proportions after adding alumina become approximately 51.7 wt.% and 48.3 wt.%, respectively. The proportion of small-angle grain boundaries increases to approximately 51.7 wt.%, while the proportion of large-angle grain boundaries decreases to approximately 48.3 wt.%. This change indicates an increase in dislocation density; alumina particles hinder dislocation movement, leading to dislocation accumulation and the formation of small-angle grain boundaries (subgrained structures). Alumina pins grain boundary migration, inhibiting the formation of large-angle grain boundaries and hindering the recrystallization process. The increase in the proportion of small-angle grain boundaries may be accompanied by grain refinement, which can improve material strength.

[0065] Figures (a2) and (b2) show that the main phases of the experimental solder are Ag3In, In3Sn, and AgIn2, with mass percentages of 44.6%, 43.1%, and 12.3%, respectively, and a relatively uniform distribution. After the addition of alumina, the mass percentages become 49.3%, 40%, and 5.8%, respectively, with Al2O3 accounting for 4.9%. Significant aggregation and segregation of the Ag3In phase can be observed. Analysis suggests that the alumina particles hinder the free diffusion of Ag and In atoms, leading to local enrichment of the Ag3In phase.

[0066] XRD analysis of solder: To further determine the composition of each phase in the solder, XRD phase analysis was performed on the solder alloy. The results are as follows: Figure 5 As shown. Among them, (a), (b), (c), (d), and (e) correspond to In. 90 Sn7Ag3, In 89 Sn7Ag3(Al2O3), In 88 Sn7Ag3(Al2O3)2、In 87 Sn7Ag3(Al2O3)3、In 86XRD diffraction pattern of Sn7Ag3(Al2O3)4. The XRD diffraction pattern shows that the addition of Al2O3 has a certain influence on the phase composition of the solder. Due to the low Al2O3 addition (x=0~4), the diffraction peak intensity of Al2O3 is relatively weak and is masked by the strong metal matrix peaks. Furthermore, the added alumina exists in the form of nanoparticles. Because the grain size is less than 100nm, the peak broadening is obvious under the Scherrer formula effect, making it difficult to clearly distinguish. In addition, Al2O3 does not chemically react with the matrix (In-Sn-Ag), and no new phase is formed; it exists only in a physically dispersed form, which mostly appears as background noise or weak peaks in the XRD pattern. Regarding the preparation process, Al2O3 may partially agglomerate or segregate during melting, resulting in insufficient local concentration and further reducing the diffraction signal. For metallic phases, Al₂O₃ has a high melting point and stable chemical properties, making it an effective nucleation substrate. The addition of Al₂O₃ provides numerous heterogeneous nucleation sites, reducing the required supercooling for nucleation and thus promoting the formation of more nuclei. This results in more fine grains during solidification, as demonstrated by the aforementioned EBSD results. Grain refinement occurs because the increased number of nuclei reduces the space for growth of each nucleus, leading to smaller grain sizes. Simultaneously, the structural and chemical stability of Al₂O₃ particles ensures their stability in the melt, effectively promoting the nucleation process. The addition of Al₂O₃ refines the Ag₃In and In₃Sn grains through heterogeneous nucleation. Calculations using the Scherrer formula show that the reduced grain size leads to broadened diffraction peaks, but without significant peak position shift. Related studies have found that the formation of AgIn₂ is related to the Ag / In ratio and cooling rate. Al₂O₃ may inhibit AgIn₂ formation by adsorbing Ag atoms, thus causing the AgIn₂ peak intensity to decrease with increasing Al₂O₃ content. Ag3In, as a high-hardness intermetallic compound, disperses as a reinforcing second phase, effectively improving alloy strength and creep resistance, but may reduce alloy plasticity to some extent. In3Sn, as a low-melting-point eutectic matrix phase (approximately 118℃), dominates the alloy's melting characteristics and plays a decisive role in solder wettability, but excessive presence may increase interfacial brittleness. AgIn2 is a metastable phase with poor high-temperature stability and is prone to coarsening; excessive content can cause stress concentration and reduce solder joint reliability. When fine and dispersed second-phase particles exist within the material, dislocations encounter these non-deformable particles as they move through the matrix. Due to the high hardness and good bonding with the matrix, dislocations cannot directly cut through the particles and can only continue moving by "bypassing" them. During this process, dislocation lines bend around the particles and eventually detach, leaving dislocation loops around the particles. Bypassing the particles requires additional energy, thereby improving the material's resistance to plastic deformation and strengthening the matrix.Al2O3, as an inert ceramic particle, strengthens the matrix by pinning dislocations and hindering grain boundary migration, which not only improves hardness but also inhibits the growth of the IMC layer.

[0068] Experimental Example 2

[0069] This experimental example tests the performance of the solder composition prepared in Example 1. The specific process is as follows:

[0070] Welding bond strength test: The oxide layer on the surface of the silver paste glass is removed using a special steel brush. Two prepared solder sheets are placed between the polished silver paste glass and the terminal. Heating is performed using a hot air gun at 300℃ for 20 seconds. During welding, both ends of the terminal must be subjected to force simultaneously to avoid internal stress. Pressure is continuously applied for 10 seconds during the cooling period. Three samples are prepared for each component. When performing the welding bond strength test, the samples must be kept parallel vertically to ensure the specimen is only subjected to parallel vertical forces. The testing rate is 1 mm / min. -1 .

[0071] After welding, a universal tensile testing machine was used to perform a tensile test, and different tensile force curves were obtained, such as... Figure 6 As shown in Table 1, and analyzed. Figure 6 In the diagram, (a), (b), (c), (d), and (e) correspond to In. 90 Sn7Ag3, In 89 Sn7Ag3(Al2O3), In 88 Sn7Ag3(Al2O3)2、In 87 Sn7Ag3(Al2O3)3、In 86 Tensile strength curve of Sn7Ag3(Al2O3)4.

[0072] Table 1 Bonding strength of brazing filler metals with different alumina contents

[0073]

[0074] Analysis of the curves reveals a significant stage-like characteristic in the change of bonding strength with Al2O3 content: Without alumina, the bonding strength is lowest at 126 N. At this point, the alloy strengthening mechanism is singular, relying solely on intermetallic compounds such as Ag3In and In3Sn, lacking ceramic phase support and resulting in insufficient strength. Adding Al2O3 improves the bonding strength. Especially when the Al2O3 content increases to 1–2.0 wt.%, the bonding strength significantly improves, reaching 217 N at 1.0 wt.% and 208 N at 2.0 wt.%. This is mainly attributed to the multiple strengthening effects of nano-sized Al2O3 particles. These particles, through dispersion strengthening, hinder dislocation movement and simultaneously act as heterogeneous nucleation sites, refining the intermetallic compound grains and reducing stress concentration.

[0075] Electrochemical Corrosion Test: In this test, the corrosion resistance of the solder was determined using a CHI760E electrochemical workstation. All test samples were rectangular thin films measuring 15mm × 15mm × 0.2mm. The test environment was a 3.5wt.% NaCl solution, and a three-electrode system consisting of a calomel electrode, a platinum electrode, and a working electrode was used. First, the open-circuit potential of the sample was measured. Then, based on the measured open-circuit potential, the potential scan range of the polarization curve (OCP ± 0.5V) was set, with a scan rate of 1mV·s. -1 The corrosion rate is then calculated by using the Tafel extrapolation method to determine the corrosion current density.

[0076] The results are as follows Figure 7 As shown. Figure 7 In the diagram, (a), (b), (c), (d), and (e) correspond to In. 90 Sn7Ag3, In 89 Sn7Ag3(Al2O3), In 88 Sn7Ag3(Al2O3)2、In 87 Sn7Ag3(Al2O3)3、In 86 Tafel curve of Sn7Ag3(Al2O3)4.

[0077] The obtained Tafel curves were analyzed and processed to obtain the corrosion potential E. corr The corrosion current density i can be calculated using the Tafel extrapolation method. corr The results are shown in Table 2.

[0078] Table 2 Corrosion potential and corrosion current density of solders with different alumina contents

[0079]

[0080] From the corrosion potential perspective, when the alumina content increased from 0 wt.% to 1 wt.%, the corrosion potential significantly increased (from -1.05 V to -0.59 V), indicating improved thermodynamic stability and enhanced corrosion resistance. Further increasing the alumina content to 2 wt.% resulted in a decrease in the corrosion potential to -0.67 V, subsequently stabilizing at -0.68 V at 3 wt.% and 4 wt.%. This shows that the addition of alumina at 1 wt.% significantly improved the corrosion potential; beyond 1 wt.%, although the potential decreased and tended to stabilize, it remained higher than the sample without alumina, indicating that the addition of alumina generally improved the material's corrosion resistance. Appropriate amounts of alumina may have formed a dense oxide film or refined grains, hindering the penetration of corrosive media. Analysis of the corrosion current density revealed a high corrosion current density (5.75 × 10⁻⁶) at 0 wt.% alumina content. -5 A / cm 2This indicates a rapid corrosion rate and poor corrosion resistance. Adding alumina significantly reduced the alloy's corrosion current density and markedly improved its corrosion resistance. In particular, when the alumina content increased to 1%, the corrosion current density dropped sharply to 2.18 × 10⁻⁶. -8 A / cm 2 This indicates that the corrosion rate has decreased significantly and the corrosion resistance has been greatly improved.

[0081] After completing the electrochemical corrosion test, the tested brazing filler metal sheet was observed using a metallographic microscope. 100× microscopic metallographic images were taken to observe and analyze the number of pitting corrosion pits. The results are as follows: Figure 8 As shown. Among them, (a), (b), (c), (d), and (e) correspond to In. 90 Sn7Ag3, In 89 Sn7Ag3(Al2O3), In 88 Sn7Ag3(Al2O3)2、In 87 Sn7Ag3(Al2O3)3、In 86 Microstructure of Sn7Ag3(Al2O3)4 after corrosion. It can be seen that the number of pits is significantly reduced, and the size of the pits is also smaller, after the addition of alumina. This means that the corrosion resistance of the brazing filler metal is indeed significantly improved after the addition of alumina.

[0082] Example 2

[0083] This embodiment prepares an indium-tin-silver alloy solder composition, and the specific process is as follows:

[0084] Using an electronic balance with an accuracy of 0.001g, press In (90-x) Sn7Ag3Mo x (x = 0, 1, 2, 3, 4 wt.%) Weigh out 10g of high-purity metal raw materials (indium granules ≥ 99.99%, tin granules ≥ 99.8%, silver powder 99.5%, molybdenum powder 99.9%). Evenly sprinkle 0.1g of rosin powder as a release agent on the inner wall of a clean and dried quartz crucible, then fill it with the mixed raw materials. Cover the surface with a 0.05g rosin protective layer and place it in an argon-protected box-type resistance furnace at 280℃ for 18 minutes. After removal, mechanically stir at 300rpm for 1 minute to ensure homogeneity, then return to the furnace for 2 minutes and pour onto an oxygen-free copper plate for rapid cooling. Subsequently, clean with 40kHz ultrasonic ethanol for 10 minutes, and roll multiple times (20% reduction per pass) using a twin-roll mill (200mm diameter) to a final thickness of 100±5μm. Repeat the rolling process 5-6 times to ensure uniform composition. Finally, ultrasonically clean the solder sheet again and seal it for later use.

[0085] Experimental Example 3

[0086] This experimental example describes the structural characterization and phase analysis of the solder composition prepared in Example 2. The specific process is as follows:

[0087] Figure 9 Microstructures of indium-tin-silver alloys with different Mo contents are shown. (a), (b), (c), (d), and (e) correspond to In... 90 Sn7Ag3, In 89 Sn7Ag3Mo, In 88 Sn7Ag3Mo2, In 87 Sn7Ag3Mo3, In 86 Microstructure of Sn7Ag3Mo4. In solder without added Mo, such as... Figure 9 In (a), the microstructure mainly consists of Sn-In solid solution and dispersed Ag phase, with large and unevenly distributed grains. When the Mo content increases to 1 wt.%, Figure 9 In (b) of the sample, slight grain refinement was observed, which may be due to the addition of Mo promoting the formation of fine intermetallic compounds, thereby inhibiting grain growth. At a Mo content of 2 wt.%, Figure 9 In the middle (c) stage, the microstructure of the solder is more uniform, and the size of the second phase (such as Ag-Sn or Mo-Sn compounds) is smaller and the distribution is more dispersed, indicating that the addition of Mo at this time has a good effect on refining and strengthening the microstructure. When the Mo content is further increased to 3 wt.%, Figure 9 In the middle (d) stage, more Mo-rich phases begin to appear in the microstructure, and these hard phases may improve the strength of the solder. When the Mo content reaches 4 wt.%, Figure 9 In the middle (e) stage, Mo causes the intermetallic compounds to coarsen and agglomerate, resulting in a decrease in the uniformity of the microstructure.

[0088] Figure 10 Showing In 90 Scanning electron microscope (SEM) images of the Sn7Ag3 solder before and after the addition of Mo. (a) and (b) correspond to In... 90 Microscopic images of Sn7Ag3 at 500× and 10000× scanning electron microscopes; (c) and (d) correspond to In 88 Microscopic images of Sn7Ag3Mo2 at 500× and 10000× scanning electron microscopes. Figure 11 Showing In 90 EDS energy dispersive spectroscopy (EDS) images of Sn7Ag3 solder before and after the addition of Mo. (a) shows the EDS image of the solder sheet without alumina; (b) shows the EDS image of the solder sheet with alumina. 88 EDS energy dispersive spectroscopy analysis of Sn7Ag3Mo2.

[0089] In solder without added Mo ( Figure 10 In (a) and (b), the microstructure exhibits a typical Sn-In solid solution matrix, combined with... Figure 11 The result at point A in (a) shows an Ag-rich phase (Ag 34.5 wt.%, In 65.5 wt.%). Ag and In form compounds that precipitate in clusters within the solder. Ag and In may form intermetallic compounds, such as AgIn2 or Ag3In, which are typically brittle and prone to cluster precipitation. Therefore, the larger intermetallic compounds should be the AgIn2 phase. In and Sn may form solid solutions or low-melting-point eutectic structures, making them more readily soluble in the matrix. This can be seen from... Figure 11 The results showing an In-rich phase at detection point B in (a) are confirmed. High-magnification observation shows ( Figure 10 In (b), the second phases AgIn2 mostly exhibit blocky or short rod-like morphologies, are well-bonded to the matrix, and show size inhomogeneity and local agglomeration. This microstructure may lead to anisotropic mechanical properties in the material. After adding Mo ( Figure 10 In (c) and (d), the microstructure of the solder underwent significant changes. Low-magnification observation ( Figure 10 As shown in (c)), fine phases appeared in the tissue, while the larger AgIn2 phases, such as clumps, were significantly reduced and more evenly distributed. According to... Figure 11 The data in (b) show that the fine phase is MoSn2, and this conclusion is supported by high-magnification analysis. Figure 10 (d) This can be further confirmed. The MoSn2 phase is dispersed in the matrix in the form of nano-sized particles, forming a well-coordinated distribution structure with the AgIn2 phase. This change in microstructure is mainly attributed to two factors: firstly, the high-melting-point MoSn2 phase effectively inhibits grain boundary migration and phase coarsening processes; secondly, the addition of Mo alters the solidification behavior of the solder, promoting microstructure refinement. Comparative analysis suggests that the addition of Mo reduces the grain size of the solder by approximately 30–50%. This significant refinement effect is expected to bring about a significant grain-refining strengthening effect. Simultaneously, the uniformly distributed second-phase structure not only improves the strength of the solder but may also enhance its thermal stability.

[0090] Figure 12 The EBSD analysis results of the solder composition are shown, where (a) and (b) correspond to In 90 IDF+GB and PH plots of Sn7Ag3; (c) and (d) correspond to In 88 IDF+GB and PH plots of Sn7Ag3Mo2.

[0091] analyze Figure 12From (a) and (c), we can see that the solder sample without added Mo mainly exhibits <001> Oriented Ag3In phase and <111> Oriented In3Sn phase. Grain boundary distribution is as follows: small-angle grain boundaries (2-10°) account for 28.2 wt.%, large-angle grain boundaries (>10°) account for 71.8 wt.%, and there is a significant (010)

[001] cubic texture component. The solder sample with added Mo has added new <0001> The orientation of the MoSn2 phase changed, with the proportion of small-angle grain boundaries significantly increasing to 64.4 wt.% and large-angle grain boundaries decreasing to 35.6 wt.%. Simultaneously, a new (110)

[001] Gaussian texture composition appeared in the Ag3In phase. Figure 12 In (b) and (d), it can be observed that the phase compositions of the two phases are different (Table 3). The addition of Mo seems to inhibit the formation of the AgIn2 phase, and the distribution of the MoSn2 phase is more uniform.

[0092] Table 3 Comparison of phase content in solder samples with and without added Mo

[0093]

[0094] Figures 13 to 18 They respectively showed In 90 Sn7Ag3, In 89 Sn7Ag3Mo, In 88 Sn7Ag3Mo2, In 87 Sn7Ag3Mo3, In 86 XRD patterns of Sn7Ag3Mo4 and a summary of XRD patterns.

[0095] It can be seen that In without Mo 90 Sn7Ag3 solder is mainly composed of γ-InSn4 phase, β-In3Sn phase, and AgIn2 phase. The XRD pattern of the solder changes significantly with increasing Mo content. Figure 14 The XRD pattern of the solder with 1.0 wt.% Mo shows the presence of the Mo phase with the (110) crystal plane in the solder. Figure 15 , 16XRD patterns of solders with 2.0 wt.%, 3.0 wt.%, and 4.0 wt.% Mo added, respectively. With further increases in Mo content (2.0 wt.%, 3.0 wt.%, and 4.0 wt.%), Mo gradually dissolved into the matrix and existed in the solder as the MoSn2 phase with the (203) crystal plane. The formation of the MoSn2 phase improved the solder's resistance to coarsening at high temperatures, allowing it to maintain a good microstructure even under high-temperature operating conditions. The addition of Mo also caused a slight shift in the main diffraction peak, indicating that the introduction of Mo affected the crystal structure of the solder. Furthermore, the addition of Mo promoted the refinement of the γ-InSn4 phase, resulting in a more uniform solder microstructure. As the Mo content increases, the peak intensity of the Ag3In phase also changes. In particular, the peak intensity of the Ag3In phase is significantly enhanced in solders with Mo contents of 3.0 wt.% and 4.0 wt.%, indicating that the addition of Mo may affect the distribution of Ag elements and the formation of the phase.

[0096] Test Example 4

[0097] This test example demonstrates the performance testing of the solder composition prepared in Example 2, and the specific testing method is the same as in Example 2.

[0098] Figure 19 Table 4 shows the pull force curves and bonding strength of the solders with different Mo contents. Figure 19 In the diagram, (a), (b), (c), (d), and (e) correspond to In. 90 Sn7Ag3, In 89 Sn7Ag3Mo, In 88 Sn7Ag3Mo2, In 87 Sn7Ag3Mo3, In 86 Tensile strength curve of Sn7Ag3Mo4.

[0099] Table 4 Bonding strength of solders with different Mo contents

[0100]

[0101] When the Mo content is 0%, the bonding strength is the lowest, only 188 N. The intermetallic compound formed by Ag and In alone cannot provide much strength. The addition of Mo significantly improves the welding bonding strength of the solder, especially when the Mo content is 2 wt.%, the bonding strength reaches as high as 269 N. This is mainly attributed to the refining effect of Mo, the pinning effect of MoSn2 nanoparticles, and the synergistic effect of solid solution strengthening.

[0102] Figure 20 Tafel curves of solders with different Mo contents are shown. (a), (b), (c), (d), and (e) correspond to In... 90Sn7Ag3, In 89 Sn7Ag3Mo, In 88 Sn7Ag3Mo2, In 87 Sn7Ag3Mo3, In 86 Tafel curve of Sn7Ag3Mo4.

[0103] Analysis of the Tafel curves yields the self-corrosion potential E. corr Then, the self-corrosion current density i is calculated using the Tafel extrapolation method. corr As shown in Table 5:

[0104] Table 5. Self-corrosion potential E of solder samples with different Mo contents corr and self-corrosion current density i corr

[0105]

[0106] It can be seen that the addition of Mo affects the self-corrosion potential E of the solder. corr The improvement is significant, especially when the Mo content reaches 2-4 wt.%, showing a stable increase of approximately 0.4 V compared to 0% addition. This is presumably due to the higher electrode potential of Mo compared to In and Sn, and the formation of a passivation film during corrosion. Regarding the self-corrosion current density i... corr The corrosion rate is minimized when the Mo content is 3 wt.%, meaning the corrosion rate is the slowest, while the effect is second best when the content is 2 wt.%.

[0107] Further, after completing the electrochemical corrosion test, a metallographic microscope was used to observe and record the surface of the corroded solder sample. The results are as follows: Figure 21 As shown. Among them, (a), (b), (c), (d), and (e) correspond to In. 90 Sn7Ag3, In 89 Sn7Ag3Mo, In 88 Sn7Ag3Mo2, In 87 Sn7Ag3Mo3, In 86 Microstructure of Sn7Ag3Mo4 after etching.

[0108] It can be seen that after etching, solder samples with different Mo contents have pits of varying sizes distributed on their surfaces. Figure 21 The solder surfaces with Mo contents of 2.0 wt.% and 3.0 wt.% (c) and (d) respectively showed significantly smaller and fewer pits. This indicates that the addition of Mo can improve the electro-corrosion performance of the solder.

[0109] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A brazing filler alloy composition, characterized in that: It contains, by mass percentage, 83.0–92.0% In, 6.0–8.0% Sn, 2.0–4.0% Ag, 0.1–8.0% M, and the balance being unavoidable impurities; M is Al2O3 or Mo.

2. The brazing alloy composition according to claim 1, characterized in that: The brazing alloy composition contains, by mass percentage, 85.0–90.0% In, 6.8–7.2% Sn, 2.8–3.2% Ag, 1.0–5.0% M, and the balance being unavoidable impurities; M is Al2O3 or Mo.

3. The brazing alloy composition according to claim 1, characterized in that: When M is Al2O3, the Al2O3 is diffusely distributed.

4. The brazing alloy composition according to claim 1, characterized in that: The average particle size of the Al2O3 is 10–100 nm.

5. The brazing alloy composition according to claim 1, characterized in that: When M is Mo, Mo forms the MoSn2 phase; the MoSn2 phase is diffusely distributed.

6. The brazing alloy composition according to claim 5, characterized in that: The average particle size of the MoSn2 phase is 10–100 nm.

7. A method for preparing the brazing alloy composition according to any one of claims 1 to 6, characterized in that: Includes the following steps: Indium granules, tin granules, silver powder, and M powder are mixed according to the stated mass percentages to form a solder alloy composition.

8. A solder sheet, characterized in that: Includes the brazing alloy composition according to any one of claims 1 to 6.

9. A method for preparing the solder sheet according to claim 8, characterized in that: Includes the following steps: The brazing alloy composition according to any one of claims 1 to 6 is rolled to obtain the brazing sheet.

10. An electrical connection on a device component, characterized in that: Includes the brazing alloy composition according to any one of claims 1 to 6.

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