A multi-component tin-indium based lead-free low temperature solder and a method for producing the same

Abstract

The application discloses a multi-component tin-indium series lead-free low-temperature solder and a preparation method thereof, and belongs to the technical field of microelectronic packaging. The multi-component tin-indium series lead-free low-temperature solder comprises the following components in percentage by mass: Bi: 0.5-5%, Ga: 0.1-1.5%, and the balance of Sn25In matrix and an inevitable small amount of impurities. Compared with traditional solder, the multi-component tin-indium series lead-free low-temperature solder has the advantages of good heat conduction performance, good fluidity, small expansion and shrinkage, environmental protection and safety, and the like.

Description

Technical Field

[0001] This invention belongs to the field of microelectronic packaging technology, and particularly relates to a multi-component tin-indium based lead-free low-temperature solder and its preparation method. Background Technology

[0002] With the increasing demand for low-cost and low-temperature soldering processes in the electronic packaging field, currently developed low-temperature solders include pure indium and pure tin solders. Among them, pure indium solder has excellent performance, but indium metal is expensive, resulting in high costs, so there are basically no pure indium solder products on the market; pure tin solder has a melting point of about 232℃, but the casting temperature reaches about 350℃, making it unsuitable for normal application in low-temperature soldering environments.

[0003] Lead-free low-temperature solder alloys have seen rapid development in recent years due to environmental protection requirements and the trend towards miniaturization of electronic devices. Their core advantage lies in their low-temperature soldering characteristics, which can reduce damage to heat-sensitive components and lower energy consumption. Commonly used lead-free low-temperature solder alloys include tin-bismuth and tin-indium alloys. Tin-bismuth alloys, with their low melting point, have achieved large-scale application in the notebook motherboard field; while tin-indium alloys have an even lower melting point and superior wetting properties, making them suitable for biomedical and aerospace low-temperature packaging applications. However, the melting point and performance of tin-indium alloys are related to the proportion of indium in the alloy, and high indium content leads to high costs.

[0004] Chinese patent CN202411113336.9 proposes a full IMC phase Sn-Bi-In-Ag-Zn high-entropy low-temperature solder for chip interconnect and its preparation method. The preparation method includes the following steps: (1) weighing high-purity Sn, In, Bi, and Ag particles according to the design ratio, and covering them with a 1.3:1 KCl and LiCl molten eutectic salt for protection, melting the Sn-In-Bi-Ag quaternary intermediate alloy, and placing Sn, In, Bi, and Ag in sequence with the low-density metal at the bottom and the high-density metal at the top. g. To reduce specific gravity segregation during the smelting process, the material was kept at 850℃ for 2 hours and stirred thoroughly before being directly cast into water for cooling. (2) High-purity Zn particles and Sn-In-Bi-Ag quaternary master alloy were weighed according to the design ratio, and the Sn-In-Bi-Ag quaternary master alloy was placed on the Zn particles for protection. Molten KCl and LiCl eutectic molten salt were poured onto the surface of the metal raw material, kept at 500℃ for 1 hour and stirred thoroughly before being directly cast into water for cooling to obtain Sn-Bi-In-Ag-Zn high-entropy alloy solder. However, the proportion of In element in the solder obtained by this preparation method exceeds 25%, and other precious metals are added, so the cost is still relatively high.

[0005] In summary, developing a lead-free, environmentally friendly, low-cost low-temperature solder with welding performance comparable to high-indium alloys is an urgent problem to be solved in this technical field. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes a multi-component tin-indium based lead-free low-temperature solder and its preparation method. This method significantly reduces costs, is environmentally friendly, and produces a low-temperature solder with excellent thermal conductivity, ductility, and wettability, making it suitable for low-temperature soldering in the field of microelectronic packaging technology.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] One of the objectives of this invention is to provide a multi-component tin-indium-based lead-free low-temperature solder, comprising the following components by mass percentage: Bi: 0.5-5%, Ga: 0.1-1.5%, with the balance being Sn25In matrix and unavoidable small amounts of impurities.

[0009] The multi-component lead-free low-temperature solder provided by this invention is mainly composed of a tin-indium alloy. In has a melting point of only 156.61℃, excellent thermal and electrical conductivity, good fluidity, and low expansion / contraction rate. Adding it to the solder alloy lowers the melting point, and it is lead-free, non-toxic, and environmentally friendly. The solder also contains Bi and Ga. Bi lowers the melting point of the solder alloy, and Bi also has solidification expansion properties, which can offset the stress caused by thermal expansion and contraction during soldering, reducing the risk of solder joint cracking. However, if the Bi content exceeds 7.5%, it can cause filler lifting or cracking at the solder joint. Ga has an ultra-low melting point of only 29.76℃, and Ga also has excellent wettability and fluidity, which can increase the solder alloy's soldering spread area by 15-20%, reducing the risk of cold solder joints.

[0010] Furthermore, the multi-component tin-indium-based lead-free low-temperature solder comprises the following components by mass percentage: Bi: 0.99-2%, Ga: 0.1-1%, with the balance being Sn25In matrix and unavoidable small amounts of impurities.

[0011] Furthermore, the multi-component tin-indium-based lead-free low-temperature solder comprises the following raw material components by mass percentage: Bi (bismuth): 2%, Ga (gallium): 1%, with the balance being Sn25In matrix and unavoidable impurities.

[0012] Furthermore, in the Sn25In matrix, the mass ratio of Sn to In is (72.75-74.18):(24.25-24.73).

[0013] The second objective of this invention is to provide a method for preparing a multi-component tin-indium based lead-free low-temperature solder, comprising the following steps:

[0014] Preparation of Sn25In matrix;

[0015] Bi, Ga and Sn25In matrix are weighed in proportion and mixed to obtain a mixture. The mixture is added to a lead-free graphite heating furnace, an antioxidant is added, and a second heating is carried out under a nitrogen atmosphere until the material melts. Then, a second constant temperature stirring is carried out and the mixture is cast into a mold to obtain a multi-component tin-indium lead-free low-temperature solder.

[0016] Furthermore, the preparation method of the Sn25In matrix includes the following steps: Sn raw material is added to a lead-free graphite heating furnace for a first heating until the material melts, then In raw material is added, and heating continues until melting, followed by a first constant temperature stirring to obtain the Sn25In matrix.

[0017] Furthermore, the temperature of the first heating is 300-350°C; and / or,

[0018] The specific operating steps for the first constant temperature stirring are as follows: stir at 300-350℃ for 30 minutes.

[0019] Furthermore, the amount of antioxidant added is sufficient to fully cover the surface; the antioxidant is rosin.

[0020] Furthermore, the temperature of the second heating is 300-350°C; and / or,

[0021] The specific steps for the second constant temperature stirring are as follows: stir at 300-350℃ for 30 minutes and then keep warm for 30 minutes to ensure that the various elements are mixed evenly.

[0022] Furthermore, the mold is made of graphite.

[0023] The third objective of this invention is to provide an application of a multi-component tin-indium-based lead-free low-temperature solder in the field of low-temperature soldering for microelectronic packaging.

[0024] Compared with the prior art, the present invention has the following advantages and technical effects:

[0025] 1. Suppressing low-temperature phase transitions and preventing "tin poisoning": Tin is prone to allotropic transformation (β-tin → α-tin) at low temperatures, known as "tin poisoning," which can lead to material pulverization and failure. Adding bismuth can effectively suppress this phenomenon, improve the low-temperature stability of solder, and allow it to maintain its structural integrity in low-temperature environments. This characteristic is particularly important for electronic devices that need to operate in low-temperature environments for extended periods.

[0026] 2. Enhanced oxidation resistance and soldering quality: The addition of bismuth and gallium can reduce the oxidation tendency of solder and significantly improve the oxidation resistance of solder. If nanoparticles are further added to the solder, the mechanical properties caused by the addition of gallium can be compensated, making the solder a lead-free low-temperature solder with excellent performance in low-temperature characteristics, wetting properties, mechanical properties and other aspects.

[0027] 3. Optimized Mechanical Properties and Reliability: The addition of bismuth improves the alloy's ductility and fatigue resistance, while gallium's liquid wetting properties help form a more uniform weld structure. After adding bismuth, the solder forms a fine-grained structure during solidification, thereby reducing cracking tendency and increasing joint strength. Furthermore, gallium's fluidity enhances the solder's ability to cover complex surfaces, improving welding reliability.

[0028] 4. Expanding application scenarios: Tin-indium solder containing bismuth and gallium is not only suitable for traditional electronic packaging, but also for special welding in low-temperature environments (such as aerospace equipment), high-precision sputtering target bonding, and connection of heat-sensitive components.

[0029] 5. Low cost: Compared with traditional tin-indium solder formulations, the solder formulation of this invention significantly reduces the amount of metallic In, thereby achieving low cost. Attached Figure Description

[0030] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0031] Figure 1 The melting characteristic curve of the multi-component tin-indium-based lead-free low-temperature solder prepared in Example 1 of this invention;

[0032] Figure 2 The melting characteristic curve of the multi-component tin-indium-based lead-free low-temperature solder prepared in Example 2 of the present invention;

[0033] Figure 3 The melting characteristic curve of the multi-component tin-indium-based lead-free low-temperature solder prepared in Example 3 of the present invention;

[0034] Figure 4 The melting characteristic curve of the multi-component tin-indium-based lead-free low-temperature solder prepared in Example 4 of this invention;

[0035] Figure 5 The melting characteristic curve of the solder prepared in Comparative Example 1 of this invention;

[0036] Figure 6 The melting characteristic curve of the solder prepared in Comparative Example 2 of this invention;

[0037] Figure 7 The melting characteristic curve of the solder prepared in Comparative Example 3 of this invention;

[0038] Figure 8 This is a comparison diagram of the tensile strength of the solders prepared in Examples 1, 2, 3, 4 and Comparative Example 1 of the present invention;

[0039] Figure 9 The crystal phase diagrams are those of the solders prepared in Examples 1, 2, 3, 4 and Comparative Example 1 of the present invention; wherein, a) Example 1, b) Example 2, c) Example 3, d) Example 4, and e) Comparative Example 1. Detailed Implementation

[0040] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0041] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0042] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0043] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0044] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0045] The lead-free low-temperature solder described in this invention is mainly composed of tin-indium solder. The added metal Bi has solidification expansion characteristics; the added metal Ga has excellent wettability and fluidity; no metal Pb is added in this invention. Compared with traditional solders, this multi-component tin-indium lead-free low-temperature solder has advantages such as good thermal conductivity, good fluidity, low expansion and contraction rate, and environmental safety.

[0046] This invention provides a multi-component tin-indium-based lead-free low-temperature solder, comprising the following components by mass percentage: Bi: 0.5-5%, Ga: 0.1-1.5%, with the balance being a Sn25In matrix and unavoidable trace impurities. Preferably, the multi-component tin-indium-based lead-free low-temperature solder comprises the following components by mass percentage: Bi: 0.99-2%, Ga: 0.1-1%, with the balance being a Sn25In matrix and unavoidable trace impurities.

[0047] In the following optional embodiments of the present invention, the mass ratio of Sn to In in the Sn25In matrix is ​​(72.75-74.18):(24.25-24.73). Exemplarily, in the following preferred embodiments of the present invention, the mass ratio of Sn to In is 73.5:24.5, 72.75:24.25, 74.18:24.73, or 74.11:24.7.

[0048] This invention also provides a method for preparing a multi-component tin-indium based lead-free low-temperature solder, comprising the following steps:

[0049] (1) Preparation of Sn25In matrix: Sn raw material is added to lead-free graphite heating furnace and heated until melted, then In raw material is added and heated until melted. Stirring at constant temperature to obtain Sn25In matrix;

[0050] (2) Weigh Bi, Ga and Sn25In matrix in proportion and mix them to obtain a mixture. Add the mixture to a lead-free graphite heating furnace, add an antioxidant, heat to melt under a nitrogen atmosphere, stir at a constant temperature, and cast into a mold to obtain a multi-component tin-indium lead-free low-temperature solder.

[0051] In the following optional embodiments of the present invention, the heating temperature in step (1) is 300-350°C. Exemplarily, in the following preferred embodiments of the present invention, the heating temperature is 350°C.

[0052] In the following optional embodiments of the present invention, the specific operation steps of the constant temperature stirring in step (1) are: stirring at 300-350°C for 30 minutes. For example, in the following preferred embodiments of the present invention, the specific operation steps of the constant temperature stirring are: stirring at 350°C for 30 minutes.

[0053] In the following optional embodiments of the present invention, in step (2), the antioxidant is rosin. It is applied by uniformly covering the surface and isolating it from air.

[0054] In the following optional embodiments of the present invention, the heating temperature in step (2) is 300-350°C. Exemplarily, in the following preferred embodiments of the present invention, the heating temperature is 350°C.

[0055] In the following optional embodiments of the present invention, the specific operation steps of the constant temperature stirring in step (2) are as follows: stirring at 300-350°C for 30 minutes and then keeping warm for 30 minutes to ensure uniform mixing of various elements. For example, in the following preferred embodiments of the present invention, the specific operation steps of the constant temperature stirring are as follows: stirring at 350°C for 30 minutes and then keeping warm for 30 minutes.

[0056] In the following optional embodiments of the present invention, in step (2), the mold is made of graphite.

[0057] The multi-component tin-indium-based lead-free low-temperature solder can be used in the field of low-temperature soldering for microelectronic packaging.

[0058] For example, in the following embodiments of the present invention, the multi-component tin-indium-based lead-free low-temperature solder comprises the following components by mass percentage: Bi: 0.99-2% (for example, Bi is 0.99% or 2%), Ga: 0.1-1% (for example, Ga is 0.1%, 0.19%, or 1%), Sn: 72.75-74.18% (for example, Sn is 72.75%, 73.5%, 74.11%, or 74.18%), In: 24.25-24.73% (for example, In is 24.25%, 24.5%, 24.7%, or 24.73%).

[0059] Unless otherwise specified, "room temperature" in this invention refers to 20-30℃.

[0060] All raw materials used in this invention were purchased from the market.

[0061] The technical solution of the present invention will be further illustrated by the following embodiments.

[0062] Example 1

[0063] A multi-component tin-indium-based lead-free low-temperature solder comprises the following components by mass percentage: Bi (bismuth): 1%, Ga (gallium): 1%, Sn (tin): 73.5%, and In (indium): 24.5%.

[0064] A method for preparing a multi-component tin-indium based lead-free low-temperature solder includes the following steps:

[0065] (1) Preparation of Sn25In matrix: Sn is added to a lead-free graphite heating furnace and heated to 350°C until melted. Then In is added and heated to 350°C until melted. After melting, the mixture is stirred and kept warm for 30 minutes to obtain Sn25In matrix.

[0066] (2) Weigh Bi, Ga and Sn25In matrix in proportion and mix them to obtain a mixture. Add the mixture to a lead-free graphite heating furnace and cover the surface of the mixture with antioxidant rosin (the amount of antioxidant added should be enough to evenly cover the surface of the mixture to achieve the effect of isolating air, the same below). Heat at 350°C in a nitrogen atmosphere until it melts. After melting, stir at a constant temperature for 30 minutes and then keep warm for 30 minutes to make it evenly mixed. Cast it into a graphite mold to obtain a multi-component tin-indium lead-free low-temperature solder.

[0067] Example 2

[0068] A multi-component tin-indium-based lead-free low-temperature solder comprises the following components by mass percentage: Bi (bismuth): 2%, Ga (gallium): 1%, Sn (tin): 72.75%, and In (indium): 24.25%.

[0069] A method for preparing a multi-component tin-indium based lead-free low-temperature solder includes the following steps:

[0070] (1) Preparation of Sn25In matrix: Sn is added to a lead-free graphite heating furnace and heated to 350°C until melted. Then In is added and heated to 350°C until melted. After melting, the mixture is stirred and kept warm for 30 minutes to obtain Sn25In matrix.

[0071] (2) Weigh Bi, Ga and Sn25In matrix in proportion and mix them to obtain a mixture. Add the mixture to a lead-free graphite heating furnace, cover the surface of the mixture with antioxidant rosin, heat it to 350°C under nitrogen atmosphere until it melts, stir it at a constant temperature for 30 minutes after melting, and then keep it at a constant temperature for 30 minutes to make it evenly mixed. Cast it into a graphite mold to obtain a multi-component tin-indium lead-free low-temperature solder.

[0072] Example 3

[0073] A multi-component tin-indium-based lead-free low-temperature solder comprises the following components by mass percentage: Bi (bismuth): 0.99%, Ga (gallium): 0.1%, Sn (tin): 74.18%, and In (indium): 24.73%.

[0074] A method for preparing a multi-component tin-indium based lead-free low-temperature solder includes the following steps:

[0075] (1) Preparation of Sn25In matrix: Sn is added to a lead-free graphite heating furnace and heated to 350°C until melted. Then In is added and heated to 350°C until melted. After melting, the mixture is stirred and kept warm for 30 minutes to obtain Sn25In matrix.

[0076] (2) Weigh Bi, Ga and Sn25In matrix in proportion and mix them to obtain a mixture. Add the mixture to a lead-free graphite heating furnace, cover the surface of the mixture with antioxidant rosin, heat it to 350°C under nitrogen atmosphere until it melts, stir it at a constant temperature for 30 minutes after melting, and then keep it at a constant temperature for 30 minutes to make it evenly mixed. Cast it into a graphite mold to obtain a multi-component tin-indium lead-free low-temperature solder.

[0077] Example 4

[0078] A multi-component tin-indium-based lead-free low-temperature solder comprises the following components by mass percentage: Bi (bismuth): 0.99%, Ga (gallium): 0.2%, Sn (tin): 74.11%, and In (indium): 24.7%.

[0079] A method for preparing a multi-component tin-indium based lead-free low-temperature solder includes the following steps:

[0080] (1) Preparation of Sn25In matrix: Sn is added to a lead-free graphite heating furnace and heated to 350°C until melted. Then In is added and heated to 350°C until melted. After melting, the mixture is stirred and kept warm for 30 minutes to obtain Sn25In matrix.

[0081] (2) Weigh Bi, Ga and Sn25In matrix in proportion and mix them to obtain a mixture. Add the mixture to a lead-free graphite heating furnace, cover the surface of the mixture with antioxidant rosin, heat it to 350°C under nitrogen atmosphere until it melts, stir it at a constant temperature for 30 minutes after melting, and then keep it at a constant temperature for 30 minutes to make it evenly mixed. Cast it into a graphite mold to obtain a multi-component tin-indium lead-free low-temperature solder.

[0082] Comparative Example 1

[0083] A Sn25In solder comprises the following components in weight percentages: Sn (tin): 75%, In (indium): 25%.

[0084] A method for preparing Sn25In solder includes the following steps: Sn is added to a lead-free graphite heating furnace and heated to 350°C until melted, then In is added and the mixture is heated to 350°C until melted. After melting, the mixture is stirred and kept at the temperature for 30 minutes to obtain Sn25In solder.

[0085] Comparative Example 2

[0086] Same as Example 1, except that the composition is changed to Bi (bismuth): 2%, Ga (gallium): 0%, Sn (tin): 73.5%, In (indium): 24.5%.

[0087] The results showed that the melting point was slightly higher than that of Examples 1-4, and the melting performance was average.

[0088] Comparative Example 3

[0089] Same as Example 1, except that the composition is changed to Bi (bismuth): 0.5%, Ga (gallium): 0.05%, Sn (tin): 74.5875%, In (indium): 24.8625%.

[0090] The results showed that the melting point was much higher than that of Examples 1-4, and the melting performance was very poor.

[0091] Performance testing:

[0092] 1. For welding materials, melting characteristics are an important aspect of their weldability. The melting points of the samples prepared in the examples and comparative examples were determined using a differential thermal analyzer at an acceleration rate of 5°C / min under nitrogen conditions. The results are as follows: Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 As shown.

[0093] Figure 1 The melting characteristic curve of the multi-component tin-indium-based lead-free low-temperature solder prepared in Example 1 of this invention is shown below. Figure 1 As can be seen, the melting temperature is 118.2℃.

[0094] Figure 2 The melting characteristic curve of the multi-component tin-indium-based lead-free low-temperature solder prepared in Example 2 of this invention is shown below. Figure 2 As can be seen, the melting temperature is 115.9℃.

[0095] Figure 3 The melting characteristic curve of the multi-component tin-indium-based lead-free low-temperature solder prepared in Example 3 of this invention is shown below. Figure 3 As can be seen, the melting temperature is 115.6℃.

[0096] Figure 4 The melting characteristic curve of the multi-component tin-indium-based lead-free low-temperature solder prepared in Example 4 of this invention is shown below. Figure 4 As can be seen from this, the melting temperature is 114.4℃.

[0097] Figure 5 The melting characteristic curve of the solder prepared in Comparative Example 1 of this invention is shown below. Figure 5 As can be seen, the melting temperature is 141.12℃.

[0098] Figure 6 The melting characteristic curve of the solder prepared in Comparative Example 2 of this invention is shown below. Figure 6 As can be seen, the melting temperature is 121.2℃;

[0099] Figure 7 The melting characteristic curve of the solder prepared in Comparative Example 3 of this invention is shown below. Figure 7 As can be seen, the melting temperature is 140.69℃.

[0100] By comparison Figures 1-7 It can be seen that the melting point of the multi-component tin-indium-based lead-free low-temperature solder prepared in Examples 1-4 is lower than that of Comparative Examples 1, 2, and 3, indicating that the multi-component tin-indium-based lead-free low-temperature solder prepared in Examples 1-4 of the present invention has a better low-temperature melting effect.

[0101] 2. The tensile strength of the solder is one of the important indicators for evaluating the quality of welding.

[0102] Figure 8 This is a comparison chart of the tensile strength of the solders prepared in Examples 1, 2, 3, 4, and Comparative Example 1 of the present invention. Figure 8 As shown, the tensile strength of Examples 1-4 is significantly improved compared with Comparative Example 1 because the added bismuth metal forms a solid solution or intermetallic compound with tin, which significantly improves the hardness and tensile strength of the solder. Although the added gallium metal will gradually reduce the tensile strength, it is still improved overall compared with the comparative example.

[0103] Figure 9 The crystal phase diagrams of the solders prepared in Examples 1, 2, 3, 4 and Comparative Example 1 of this invention are shown below. Figure 9 As can be seen, the microcracks in Comparative Example 1 are significantly wider than those in the other four examples, indicating that the solidification expansion characteristics of Bi effectively offset the welding stress, and the low melting point of Ga improves the melt fluidity, forming a dense and continuous gradient phase distribution. The addition of Bi element inhibits the formation of brittle phases (such as Sn3In4) in the Sn-In alloy and avoids the segregation of brittle networks at grain boundaries, while the wettability of Ga optimizes the bonding interface between the liquid metal and the matrix. No needle-like or blocky brittle phases were observed in the crystal phase diagram, only Sn-In solid solution and a small amount of uniformly dispersed second-phase particles were present.

[0104] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations 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. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A multi-component tin-indium based lead-free low-temperature solder, characterized in that, The raw material composition includes the following percentages by mass: Bi: 0.99-2%, Ga: 0.1-1%, with the balance being Sn25In matrix and unavoidable impurities; The preparation method of the multi-component tin-indium based lead-free low-temperature solder includes the following steps: Preparation of Sn25In matrix; Bi, Ga and Sn25In matrix are weighed in proportion and mixed to obtain a mixture. The mixture is added to a lead-free graphite heating furnace, an antioxidant is added, and a second heating is carried out under a nitrogen atmosphere until the material melts. Then, a second constant temperature stirring is carried out and the mixture is poured into a mold to obtain a multi-component tin-indium lead-free low-temperature solder. The preparation method of the Sn25In matrix includes the following steps: Sn raw material is added to a lead-free graphite heating furnace for a first heating until the material melts, then In raw material is added and heating is continued until it melts, and a first constant temperature stirring is performed to obtain the Sn25In matrix; The temperature of the first heating is 300-350℃; The specific operating steps for the first constant temperature stirring are: stirring at 300-350℃ for 30 minutes; The second heating temperature is 300-350℃; The specific operating steps for the second constant temperature stirring are as follows: stir at 300-350℃ for 30 minutes and then keep warm for 30 minutes.

2. The multi-component tin-indium based lead-free low-temperature solder according to claim 1, characterized in that, The raw material composition includes the following percentages by mass: Bi: 2%, Ga: 1%, with the balance being Sn25In matrix and unavoidable impurities.

3. A method for preparing a multi-component tin-indium based lead-free low-temperature solder as described in any one of claims 1-2, characterized in that, Includes the following steps: Preparation of Sn25In matrix; Bi, Ga and Sn25In matrix are weighed in proportion and mixed to obtain a mixture. The mixture is added to a lead-free graphite heating furnace, an antioxidant is added, and a second heating is carried out under a nitrogen atmosphere until the material melts. Then, a second constant temperature stirring is carried out and the mixture is poured into a mold to obtain a multi-component tin-indium lead-free low-temperature solder. The preparation method of the Sn25In matrix includes the following steps: Sn raw material is added to a lead-free graphite heating furnace for a first heating until the material melts, then In raw material is added and heating is continued until it melts, and a first constant temperature stirring is performed to obtain the Sn25In matrix; The temperature of the first heating is 300-350℃; The specific operating steps for the first constant temperature stirring are: stirring at 300-350℃ for 30 minutes; The second heating temperature is 300-350℃; The specific operating steps for the second constant temperature stirring are as follows: stir at 300-350℃ for 30 minutes and then keep warm for 30 minutes.

4. The preparation method according to claim 3, characterized in that, The antioxidant is rosin.

5. The preparation method according to claim 3, characterized in that, The mold is made of graphite.

6. The application of a multi-component tin-indium-based lead-free low-temperature solder as described in any one of claims 1-2 in the field of low-temperature soldering for microelectronic packaging.

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