InSnBiZnAg high-entropy alloy nanoparticles as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of soft soldering, and particularly relates to InSnBiZnAg high-entropy alloy nanoparticles as well as a preparation method and application thereof. The InSnBiZnAg high-entropy alloy nanoparticles are prepared from the following components in percentage by mass: 20 to 50 percent of In, 20 to 45 percent of Sn, 15 to 35 percent of Bi, 2 to 12 percent of Zn and 1 to 12 percent of Ag. Compared with the prior art, the method at least has the following beneficial effects that the problem of damage of high-temperature welding to a heat-sensitive device is solved, the warping problem caused by thermal stress is reduced, and the method has the advantages of being low in melting point, high in mechanical strength, high in service reliability, high in cost performance and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of soft soldering, and in particular relates to InSnBiZnAg high-entropy alloy nanoparticles and a preparation method and application thereof. Background Art

[0002] With the advancement of flexible conformal integration technology, low-temperature connection materials have become a major bottleneck restricting the development of flexible integration. Existing liquid alloys are mainly based on Ga and In alloys, which have poor mechanical properties and cannot meet the high-reliability service requirements of flexible devices. Low-temperature solders play a crucial role in the packaging of flexible electronic devices. Currently, common flexible substrate materials include polyvinyl alcohol (PVA), polyethylene terephthalate (PET), polyimide (PI), and polyethylene naphthalate (PEN). PET is considered the most promising substrate material for flexible electronic devices due to its low cost, good light transmittance, and bending resistance. However, studies have shown that PET can suffer thermal damage at connection temperatures above 110°C. Therefore, the development and application of low-melting-point solders will help reduce soldering damage to flexible substrate materials. At the same time, with the rapid development and continuous innovation of electronic devices, the requirements for the long-term reliability of low-temperature solders are also increasing. Electronic devices are often required to operate for a long time under various environmental conditions, including high temperature, high humidity, and corrosive liquids such as sweat and seawater. As an important connection material for electronic devices, the corrosion resistance and electrochemical migration of low-temperature solder directly affect the stability of solder joints and the reliability of interconnections.

[0003] Another solder property requiring attention is electrochemical migration resistance. Electrochemical migration refers to the phenomenon in which metal ions in the solder migrate between solder joints under the influence of an electric field. This can cause problems such as short circuits and open circuits in the solder joints, seriously affecting the performance and stability of electronic devices. Electrochemical migration is particularly prominent in harsh environments such as high temperature and high humidity. Summary of the Invention

[0004] The present invention aims to solve the above-mentioned problems and provides InSnBiZnAg high-entropy alloy nanoparticles, their preparation method, and applications. The InSnBiZnAg high-entropy alloy nanoparticles have low melting points and, after soldering, exhibit high strength and high resistance to electrochemical corrosion. They can be used to interconnect electronic devices, thermoelectric materials, and flexible substrates at reflow temperatures below 100°C. Specifically, they include:

[0005] To this end, the first aspect of the present invention provides an InSnBiZnAg high-entropy alloy nanoparticle, wherein the composition of the InSnBiZnAg high-entropy alloy nanoparticle by mass is: In 20-45%, Sn 20-40%, Bi 15-35%, Zn 2-12%, and Ag 1-12%. At this time, the temperature at which the high-entropy alloy nanoparticles are fully melted and uniform is ≤130°C, the melting point is ≤130°C, and the shear strength of the resulting weld is ≥30MPa.

[0006] As a preferred embodiment, the composition of the InSnBiZnAg high-entropy alloy nanoparticles by mass is: In 25-35%, Sn 25-40%, Bi 20-30%, Zn 3-12%, and Ag 1.5-8%. At this time, the temperature at which the high-entropy alloy nanoparticles are fully melted and uniformly is ≤100°C, the melting point is ≤80°C, and the shear strength of the resulting solder joint is ≥30MPa.

[0007] As a further preferred embodiment, the composition of the InSnBiZnAg high-entropy alloy nanoparticles by mass is: In 28.6-32%, Sn 33-35.3%, Bi 21.7-25.9%, Zn 4-12%, and Ag 1.8-6.2%. At this time, the temperature at which the high-entropy alloy nanoparticles are fully melted and uniform is ≤80°C, the melting point is ≤60°C, and the shear strength of the resulting weld is ≥30 MPa.

[0008] To further enhance the shear strength of solder joints made with InSnBiZnAg high-entropy alloy nanoparticles, the mass percentage of Ag in the InSnBiZnAg high-entropy alloy nanoparticles can be appropriately increased. When the mass composition of the InSnBiZnAg high-entropy alloy nanoparticles satisfies the following: In 20-45%, Sn 20-40%, Bi 15-35%, Zn 2-12%, and Ag 4-12%, the resulting solder joints exhibit a shear strength of ≥40 MPa.

[0009] Ag, a high-melting-point element, enhances the strength of high-entropy alloys, but it also forms large Ag2In phases within the alloy. Therefore, the addition of Zn is necessary to effectively refine the microstructure. Furthermore, Ag in the alloy has a stronger affinity with Zn, forming relatively stable Ag-Zn-In dispersion-strengthened particles. Because Zn has a good affinity with Cu, adding a small amount of Zn to the solder alloy increases the wettability of the solder on the Cu substrate. However, due to Zn's susceptibility to oxidation, excessive Zn content in the solder alloy negatively impacts its wettability. After reflow, the solder tends to shrink toward the center of the solder joint, resulting in a reduced wetted area. Therefore, the Zn content must be controlled.

[0010] Furthermore, the InSnBiZnAg alloy exhibits excellent resistance to chemical corrosion, forming a passivation layer on its surface that makes it difficult for charges to pass through, resulting in higher resistance to corrosion. Initially, a rapid corrosion reaction occurs on the alloy's surface, forming a passivation layer (In2O3). Subsequently, the passivation layer's barrier and the alloy's internal multicomponents' suppression of material diffusion slow the spread of corrosion into the metal, resulting in a relatively slow second stage of the corrosion process.

[0011] According to the present invention, the average particle size of the above-mentioned InSnBiZnAg high entropy alloy nanoparticles is 30 to 100 nm.

[0012] A second aspect of the present invention provides a method for preparing InSnBiZnAg high entropy alloy nanoparticles. The preparation method comprises:

[0013] 1) The raw material metals are loaded into a crucible (which may be a non-metallic crucible, such as an Al2O3 crucible), and the order in which the raw material metals are loaded into the crucible is high melting point first and low melting point last, that is, the order of addition is Ag-Zn-Bi-Sn-In, and the position relationship of the raw material metals in the crucible from bottom to top is Ag-Zn-Bi-Sn-In;

[0014] 2) Melting under vacuum, cooling and forming to obtain an ingot;

[0015] 3) Repeat step 2) for a total number of smelting times ≥ 2 to obtain an InSnBiZnAg high entropy alloy ingot;

[0016] The first melting is carried out under vacuum state, and the ingot is obtained after cooling and forming;

[0017] 3) The obtained InSnBiZnAg high entropy alloy ingot is placed in an organic dispersant and subjected to heating-ultrasonic oscillation until the alloy ingot disappears, and then water-cooled, formed, washed, centrifuged to obtain a solid precipitate, and freeze-dried to obtain InSnBiZnAg high entropy alloy nanoparticles.

[0018] As a preferred embodiment, before step 1), the process further includes: cleaning the raw metal particles to remove surface oxides and contaminants. The cleaning process may include: using a 5-10% hydrochloric acid-ethanol solution to clean the raw metal particles to remove surface oxides and contaminants, applying ultrasound during the cleaning process for 3-5 minutes. After acid cleaning, the particles are rinsed twice with anhydrous ethanol and dried for later use.

[0019] As a preferred embodiment, in the above-mentioned method for preparing InSnBiZnAg high entropy alloy nanoparticles, step 2) satisfies at least one of the following conditions:

[0020] The melting was carried out under an argon atmosphere;

[0021] The holding temperature of smelting is 800-900℃;

[0022] The holding time for smelting is 20 to 50 minutes;

[0023] The heating rate of smelting is 0.8~1.2℃ / s;

[0024] The heating process of melting is accompanied by electromagnetic stirring.

[0025] According to the present invention, in a specific embodiment, the smelting step in step 2) includes: after the furnace chamber is sealed, the vacuum pump is turned on to extract the gas in the chamber to a vacuum degree of 1.3×10 -4 Pa, turn off the vacuum pump, and introduce Ar gas as a protective gas to positive pressure. Repeat the above steps 3 times to complete the purge; open the exhaust valve of the furnace chamber to maintain the Ar gas atmosphere in the cavity. Set the heating curve, where the heating rate is 1°C / s. Heat with electromagnetic stirring for 20-50 minutes to 850°C. After keeping at 850°C for 30 minutes, let the molten metal cool with the furnace to below 400°C, remove it and water cool it; water cool it for rapid molding to obtain an ingot.

[0026] As a preferred solution, step 4) satisfies at least one of the following conditions:

[0027] The holding temperature of ultrasonic oscillation is 80-120℃;

[0028] The holding time of ultrasonic oscillation is 10 to 40 minutes;

[0029] The frequency of ultrasonic oscillation is 40-80KHz;

[0030] Cold water cooling molding uses a 0℃ ice-water mixture or 0-5℃ pure water;

[0031] Wash with ethylene glycol and deionized water.

[0032] In step 4), the organic dispersant may be a mixture of water and ethylene glycol in a volume ratio of 1:1, the mixture further comprising 0.3 g / L sodium dodecylbenzenesulfonate, 1 g / L sulfosalicylic acid, and 0.1 g / L fatty acid polyethylene glycol ester. The organic dispersant may also be a solution containing 6-10 g polyethylene glycol and 0.1-0.8 g polyvinyl pyrrolidone per 100 mL of ethylene glycol.

[0033] In the present invention, the burnout rate of the raw metals must be considered. At 800-900°C, the burnout rate of raw material In is approximately 8%; the burnout rate of raw material Sn is approximately 5%; the burnout rate of raw material Bi is approximately 3%; the burnout rate of raw material Zn is 2%; and the burnout rate of raw material Ag is not considered. Those skilled in the art can determine the burnout rate of each raw metal at the corresponding temperature based on common knowledge in the art.

[0034] A third aspect of the present invention provides application of the above-mentioned InSnBiZnAg high entropy alloy nanoparticles in the field of low-temperature welding ≤100°C.

[0035] According to the present invention, the aforementioned InSnBiZnAg high-entropy alloy nanoparticles are mixed with a commercial low-temperature flux in a paste mixer to produce an InSnBiZnAg high-entropy alloy nanosolder. Depending on the alloy composition, solder joints can be obtained at a pressureless reflow temperature of 60°C-120°C. Soldering targets include, but are not limited to, copper plates, copper-clad ceramic substrates, memory alloy structures, thermoelectric alloys, and organic flexible substrates. In a specific embodiment, when the InSnBiZnAg high-entropy alloy nanoparticles are composed of 30In33Sn25Bi-4Ag4Zn, they are mixed with an ethanol-based low-temperature flux at a mass ratio of 12:3.6-5.6. In the field of electronic packaging, the resulting InSnBiZnAg high-entropy alloy nanosolder can interconnect electronic device solder joints at extremely low soldering temperatures as low as 80°C.

[0036] Among them, ethanol-based low-temperature fluxes include salicylic acid, benzotriazole derivatives, isopropyl alcohol, etc., which can be selected according to needs.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] First, the technical solution of the present invention is based on the In-Sn-Bi low-temperature alloy system, introducing Ag and Zn to form a five-element high-entropy low-temperature alloy. The high-entropy alloy adopts a multi-component alloy design, in which the raw materials of Sn, Bi and Zn are low in price, which can well balance the overall cost of alloy solder manufacturing and has a certain cost-effectiveness. In addition, the solder of the technical solution of the present invention can be used for solder joint interconnection of electronic devices at a reflow temperature of less than 100°C, solving the problem of damage to heat-sensitive devices caused by high-temperature welding and reducing the warping problem caused by thermal stress. It has the advantages of low melting point, high mechanical strength, high service reliability and high cost-effectiveness. The solder joints prepared using this low-temperature solder have stable structure, small performance changes after long-term service, and have the advantage of high reliability.

[0039] Second, the technical solution of the present invention uses simple process technology, easy-to-obtain raw materials, and is highly practical. It can fill the market gap in the current electronic device packaging field for commercial ultra-low temperature solder (melting point below 100°C) and solve the packaging and connection problems of flexible electronic devices and heat-sensitive devices.

[0040] Third, the technical solution of the present invention can efficiently obtain high-entropy alloy nanoparticles, opening up new ideas and new processes for low-temperature high-entropy alloy nanomaterials, and has high innovative value.

[0041] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are specifically listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a morphology image of InSnBiZnAg high entropy alloy nanoparticles obtained in Example 1 of the present invention;

[0043] Figure 2 Schematic diagram of nano-sizing during the preparation process of InSnBiZnAg high entropy alloy nanoparticles of the present invention;

[0044] Figure 3 This is a DSC test result diagram of Example 1 of the present invention;

[0045] Figure 4 This is a schematic diagram of EDX scanning components in Example 1 of the present invention;

[0046] Figure 5 This is a SEM characterization of the cross-sectional morphology of the solder joint obtained in Example 1 of the present invention. DETAILED DESCRIPTION

[0047] The preferred embodiments of the present invention are described in further detail below.

[0048] In the following description, a number of specific details are provided to provide a more thorough understanding of the technical solutions provided by the present invention. However, it is obvious to those skilled in the art that the technical solutions provided by the present invention can be implemented without one or more of these details.

[0049] In the present embodiment, the raw material for In is a metal ingot with a purity of 99.9%; the raw material for Sn is a metal powder with a purity of 99.9%; the raw material for Bi is a metal pellet with a purity of 99.9%; the raw material for Zn is a metal pellet with a purity of 99.9%; and the raw material for Ag is a metal pellet with a purity of 99.9%. All raw materials are commercially available.

[0050] In an embodiment of the present invention, the organic dispersant is a mixture of water and ethylene glycol, the volume ratio of water to ethylene glycol is 1:1, and the mixture further contains 0.3 g / L sodium dodecylbenzenesulfonate, 1 g / L sulfosalicylic acid, and 0.1 g / L fatty acid polyethylene glycol ester.

[0051] Examples 1-6

[0052] This embodiment provides six types of InSnBiZnAg high-entropy alloy nanoparticles and preparation methods thereof.

[0053] The target sample was prepared according to the mass composition of InSnBiZnAg high entropy alloy nanoparticles in Table 1.

[0054] Table 1

[0055]

[0056] Among them, the raw material In considers about 8% of the burnout; the raw material Sn considers about 5% of the burnout; the raw material Bi considers about 3% of the burnout; the raw material Zn considers 2% of the burnout; the raw material Ag does not consider the burnout. The preparation method is as follows:

[0057] 1) Weigh and proportion the raw metals, and use a 5% hydrochloric acid ethanol solution to clean and remove surface oxides and contaminants from the raw metals. Apply ultrasound during the process for 3 to 5 minutes. After acid cleaning, rinse twice with anhydrous ethanol and dry for later use;

[0058] 2) adding the processed raw metals into an Al2O3 crucible, with the raw metals being added in the order of high melting point first and low melting point last, i.e., the order of addition is Ag-Zn-Bi-Sn-In, and the position relationship of the raw metals in the crucible from bottom to top is Ag-Zn-Bi-Sn-In;

[0059] 3) Place the crucible in the induction heating melting furnace, seal the furnace cavity, and start the vacuum pump to extract the gas in the cavity until the vacuum degree is 1.3×10 -4 Pa, turn off the vacuum pump, and introduce pure Ar gas as a protective gas until the chamber reaches a positive pressure of 0.04 Pa. Repeat the above steps 3 times to complete the gas washing;

[0060] 4) Open the exhaust valve of the furnace chamber to maintain an Ar gas atmosphere in the chamber. Set the heating curve and perform rapid heating and melting by electromagnetic induction heating. The induction current is 14.2A, the heating rate is 1°C / s, the heating process is accompanied by electromagnetic stirring, the holding temperature is 850°C, and the holding time is 60 minutes. After melting, the metal is cooled to room temperature with the furnace at a cooling rate of 2°C / min. Repeat the melting process for ≥3 times;

[0061] 5) After completing the above smelting step, the crucible is removed from the smelting furnace, and the liquid alloy is water-cooled and rapidly formed to obtain an InSnBiZnAg high-entropy alloy ingot;

[0062] 6) Place the InSnBiZnAg high-entropy alloy ingot into a crucible containing an organic dispersant until the liquid level covers the ingot. Place the crucible in an ultrasonic oscillator set to 90°C and a frequency of 60 kHz until the ingot disappears. The oscillation and holding time are 30 minutes. The mixture is quickly poured into a 0°C ice-water mixture. The obtained dispersed nanoparticles are washed with ethanol and deionized water respectively. The solid precipitate is obtained by centrifugation and freeze-dried to obtain InSnBiZnAg high-entropy alloy nanoparticles.

[0063] 7) InSnBiZnAg high-entropy nanoparticles and ethanol-based flux were mixed in a paste mixer at a mass ratio of 12:3.5 to prepare a low-temperature solder paste, which was screen-printed on the surface of a copper plate and then reflowed with another copper plate at 80°C for five minutes to obtain a solder joint.

[0064] The parameters of each InSnBiZnAg high entropy nanoparticle sample are shown in Table 2.

[0065] Table 2

[0066]

[0067] Figure 1 The morphology of the InSnBiZnAg high entropy alloy nanoparticles obtained in Example 1 of the present invention is shown in FIG. Figure 1 It can be seen that the particles have good crystallinity.

[0068] Figure 2 Schematic diagram of nano-sizing during the preparation process of InSnBiZnAg high entropy alloy nanoparticles of the present invention.

[0069] Figure 3 This is a DSC test result diagram of Example 1 of the present invention, used to illustrate the low-temperature welding characteristics. Figure 3 In the formula, Nanoparticles refers to nanoparticles; First Reflow refers to the first reflow; Second Reflow refers to the second reflow; Second Order Phase Transition refers to the second order phase transition; Cooling refers to cooling; Heating refers to heating; Melt point refers to melting point. Figure 3 The reflow melting and solidification behavior of the nanoparticles can be seen, confirming that welding is possible at a melting point of 100°C.

[0070] Figure 4 This is a schematic diagram of EDX scanning components of Example 1 of the present invention, Figure 4It can be seen that the five components are evenly distributed in the particles. Figure 4 In the table, Element represents the element symbol; Family represents the element classification; Atomic Fraction (%) represents the atomic percentage content of the element in the selected area; Atomic Error (%) represents the measurement error of the atomic percentage; Mass Fraction (%) represents the mass percentage content of the element in the selected area; Mass Error (%) represents the measurement error of the mass percentage; Fit Error (%) represents the element fitting error; Integrated Spectra represents integrated spectrum; Spectrum From Area represents a specific area; Energy represents energy; and intensity represents intensity.

[0071] Figure 5 This is a SEM characterization of the cross-sectional morphology of the solder joint obtained in Example 1 of the present invention. Figure 5 The morphology of the solder joints formed after welding can be seen.

[0072] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. An InSnBiZnAg high entropy alloy nanoparticle, characterized in that: The InSnBiZnAg high entropy alloy nanoparticles have the following composition by mass: In 20-45%, Sn 20-40%, Bi 15-35%, Zn 2-12%, and Ag 1-12%.

2. The InSnBiZnAg high entropy alloy nanoparticles according to claim 1, characterized in that The composition of the InSnBiZnAg high entropy alloy nanoparticles by mass is: In 25~35%, Sn 25~40%, Bi 20~30%, Zn 3~12%, Ag 1.5~8%.

3. The InSnBiZnAg high entropy alloy nanoparticles according to claim 1, characterized in that: The composition of the InSnBiZnAg high entropy alloy nanoparticles by mass is: In 28.6~32%, Sn 33~35.3%, Bi 21.7~25.9%, Zn 4~12%, Ag 1.8~6.2%.

4. The InSnBiZnAg high entropy alloy nanoparticles according to claim 1, characterized in that The composition of the InSnBiZnAg high entropy alloy nanoparticles by mass is: In 20~45%, Sn 20~40%, Bi 15~35%, Zn 2~12%, Ag 4~12%.

5. The InSnBiZnAg high entropy alloy nanoparticles according to any one of claims 1 to 4, characterized in that: The average particle size of the InSnBiZnAg high entropy alloy nanoparticles is 30-100 nm.

6. The method for preparing InSnBiZnAg high entropy alloy nanoparticles according to any one of claims 1 to 5, characterized in that: The preparation method comprises: 1) Adding raw metals into a crucible, wherein the order of adding the raw metals into the crucible is Ag-Zn-Bi-Sn-In, and the position relationship of the raw metals in the crucible from bottom to top is Ag-Zn-Bi-Sn-In; 2) Melting under vacuum, cooling and forming to obtain an ingot; 3) Repeat step 2) for a total number of smelting times ≥ 2 to obtain an InSnBiZnAg high entropy alloy ingot; 4) The obtained InSnBiZnAg high entropy alloy ingot is placed in an organic dispersant for heating-ultrasonic oscillation until the alloy ingot disappears, and then cooled with cold water to form, washed, centrifuged to obtain a solid precipitate, and freeze-dried to obtain InSnBiZnAg high entropy alloy nanoparticles.

7. The method for preparing InSnBiZnAg high entropy alloy nanoparticles according to claim 6, characterized in that: Before performing step 1), the process also includes cleaning and removing surface oxides and contaminants from the raw material metal.

8. The method for preparing InSnBiZnAg high entropy alloy nanoparticles according to claim 6, characterized in that: Step 2) satisfies at least one of the following conditions: The melting was carried out under an argon atmosphere; The holding temperature of smelting is 800-900℃; The holding time for smelting is 20 to 50 minutes; The heating rate of smelting is 0.8~1.2℃ / s; The heating process of melting is accompanied by electromagnetic stirring.

9. The method for preparing InSnBiZnAg high entropy alloy nanoparticles according to claim 6, characterized in that: Step 4) satisfies at least one of the following conditions: The holding temperature of ultrasonic oscillation is 80-120℃; The holding time of ultrasonic oscillation is 10 to 40 minutes; The frequency of ultrasonic oscillation is 40-80KHz; Cold water cooling molding uses a 0℃ ice-water mixture or 0-5℃ pure water; Wash with ethylene glycol and deionized water.

10. Use of the InSnBiZnAg high entropy alloy nanoparticles according to any one of claims 1 to 5 in the field of low-temperature welding at ≤100°C.

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