Preparation method of Sn42-In58 alloy preformed soldering lug

Abstract

The invention discloses a preparation method of a Sn42-In58 alloy preformed soldering lug, and belongs to the technical field of microelectronic welding connection material preparation, and the method comprises the following steps: heating tin to 230-250 DEG C for melting, and then adding indium for melting to obtain an alloy solution; casting the alloy solution to obtain an alloy ingot; the alloy cast ingot is subjected to rough rolling, primary finish rolling and secondary finish rolling, and a Sn42-In58 alloy thin strip with the thickness smaller than 0.2 mm is obtained; preparing a soldering flux solution by using ethanol, triethanolamine, nonylphenol polyoxyethylene, phenolic resin and hydrogenated rosin; and punching and slitting the alloy thin strip, immersing the alloy thin strip into the soldering flux solution for 1-3 minutes, taking out the alloy thin strip, and drying the alloy thin strip to obtain the Sn42-In58 alloy preformed soldering lug. According to the Sn42-In58 alloy preformed soldering lug prepared by the method disclosed by the invention, the alloy melting point is low, and the warping degree of a surface-mounted chip and the low welding void rate can be effectively reduced in the welding process.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of microelectronic soldering connection materials, and particularly relates to a method for preparing a Sn42-In58 alloy preform solder sheet. Background Art

[0002] Microelectronic soldering materials are one of the important basic materials in the electronic materials industry and are widely used in the assembly and interconnection of electronic devices. They mainly include solder paste, solder wire, solder bar, solder ball, preform solder sheet, flux, etc. These materials play a key role in multiple industrial links such as the PCBA process, the connection of precision structural parts, and semiconductor packaging.

[0003] A preform solder sheet is a soldering material pre-processed into a specific shape and size and is widely used in multiple fields such as electronics, automotive, aerospace, and medical. It is manufactured through precise die technology and stamping process, which can significantly improve the soldering efficiency and quality. The main feature of the preform solder sheet is that its shape and size can be customized according to the soldering requirements, so as to achieve a more precise soldering effect. Compared with traditional soldering materials, the preform solder sheet can reduce the preparation time and errors during the soldering process, improve the strength and reliability of the solder joints. In addition, the preform solder sheet also has good heat conduction performance, which helps to achieve a more uniform soldering.

[0004] Mounted chips (including chips mounted in ways such as QFN, QFP, DO, LGA, SOP, VQFN, MOSP, etc.) need to be connected to the substrate, and the middle pads and the surrounding pins of the mounted chips need solder for connection. In the past, Sn-Ag-Cu series solders (SAC) were mainly used for connection. As the mounted chips become thinner and thinner, when using Sn-Ag-Cu series solders for connection, the mounted chips will warp. At the same time, due to the increasing requirements for reliability, the requirements for the solder joint void ratio between the mounted chips and the substrate and the surrounding pins of the mounted chips are getting lower and lower, and general solder paste solders are difficult to meet.

[0005] In the field of modern chip mounting manufacturing and packaging technology, as the size of the mounted chip continues to shrink and the thickness gradually decreases, the traditional Sn-Ag-Cu solder gradually exposes serious warping problems when connecting the mounted chip to the substrate and the pins around the mounted chip. This problem not only affects the normal operation of the mounted chip but also poses a threat to the reliability of the entire electronic product. When using Sn-Ag-Cu solder for welding, significant thermal expansion and contraction changes occur during the transformation of the solder from solid state to liquid state and back to solid state. Due to the fragile structure of the mounted chip, it is difficult to withstand the resulting thermal stress. Once the thermal stress exceeds the tolerance threshold of the mounted chip, it will cause the mounted chip to warp. This warping will cause gaps and misalignments in the originally tightly fitting connection interface, and the solder joints cannot transmit electronic signals normally, ultimately leading to connection failure. In addition, warping will trigger a series of chain reactions, such as defects like cracks and delaminations in the package, which not only increase the assembly difficulty but also reduce the reliability and service life of the product.

[0006] The alloy composition of the solder is the core factor determining its comprehensive performance. Its physical properties (such as melting point, density, thermal conductivity, resistivity), mechanical properties (such as tensile strength, hardness, elongation, compressive strength), and process characteristics (such as wettability, recrystallization temperature, coefficient of thermal expansion) are all directly related to the element ratio. Therefore, when preparing the alloy preform solder sheet, the composition of the alloy must be considered as a key point. The comprehensive performance of the solder alloy affects the preparation method of the preform solder sheet in various aspects. For example, the melting point affects the temperature and method of alloy melting, the recrystallization temperature affects whether to adopt hot rolling or cold rolling process, the hardness and elongation affect how to set the rolling force and tension, and the wettability affects the selection of flux.

[0007] Some methods for preparing alloy preform solder sheets are disclosed in the prior art. For example, a gold-tin preform solder sheet and its preparation method with the publication number CN118023765A, a process for producing an ultra-thin gold-tin preform solder sheet with the publication number CN116673637A, a method for preparing a difficult-to-deform tin-bismuth alloy preform solder sheet with the publication number CN109513747A, a preparation method of a Sn-Ag-Cu alloy preform solder sheet with the publication number CN110512102A, etc. These are all preparation methods for preform solder sheets of specific solder alloys with different performances, such as gold-tin alloy, tin-bismuth alloy, and Sn-Ag-Cu alloy. Due to different alloy compositions, the adopted preparation methods are also different, and these methods are not applicable to the preparation of Sn42-In58 alloy preform solder sheets. Summary of the Invention

[0008] The purpose of the present invention is to provide a preparation method for Sn42-In58 alloy preform solder sheets, which can effectively reduce the warpage degree and void ratio of the mounted chip.

[0009] The technical solution adopted by the present invention is as follows: A preparation method of a Sn42-In58 alloy preformed solder sheet, wherein the components and mass percentages of the Sn42-In58 alloy are In 52±0.5%, and the balance is Sn; the preparation method is as follows: (1) Add tin into a crucible, heat it to 230-250°C to melt the tin, keep it warm for 10-30 minutes, then add indium and melt all the indium, raise the furnace temperature to 180-200°C, and keep it warm for 10 minutes - 30 minutes to obtain an alloy solution; (2) Pour the alloy solution into an ingot mold to obtain a Sn42-In58 alloy ingot with a casting thickness of 50-80 mm; (3) Rough roll the obtained Sn42-In58 alloy ingot, with the reduction per pass maintained at 2-10 mm and the rolling speed at 1.5-2 m / min; after multiple passes of rolling, obtain a Sn42-In58 alloy rough rolled strip with a thickness of 2 mm - 8 mm; (4) Conduct the first precision rolling on the Sn42-In58 alloy rough rolled strip, control the tension at the unwinding end to be 100N - 150N, the tension at the winding end to be 150N - 200N, the rolling speed to be 0.6 - 0.8 m / min, and the reduction per pass to be maintained at 0.1 - 0.3 mm; after multiple passes of rolling, obtain a Sn42-In58 alloy thick strip with a thickness of less than 1 mm, and then blank and slit the alloy thick strip; (5) Conduct the second precision rolling on the blanked and slit Sn42-In58 alloy thick strip, control the tension at the unwinding end to be 10N - 30N, the tension at the winding end to be 30N - 50N, the rolling speed to be 0.4 - 0.6 m / min, and the reduction per pass to be maintained at 0.02 - 0.1 mm. After multiple passes of rolling, obtain a Sn42-In58 alloy thin strip with a thickness <0.2 mm, and then blank and slit the alloy thin strip; (6) Put ethanol, triethanolamine, nonylphenol polyoxyethylene, phenolic resin, and hydrogenated rosin into a heating container, heat and stir, with the heating temperature being 40-60°C, to obtain a soldering flux solution; (7) Immerse the blanked Sn42-In58 alloy thin strip in the soldering flux solution for 1-3 minutes and then take it out, place it in an oven for drying, with the oven temperature being 60-80°C and the drying time being 20-50 minutes, to obtain a Sn42-In58 alloy preformed solder sheet.

[0010] Furthermore, the components and mass percentages of the soldering flux solution are ethanol 85-90%, triethanolamine 0.5-1%, nonylphenol polyoxyethylene ether 0.2-1%, phenolic resin 3%-8%, and hydrogenated rosin 2%-7%.

[0011] Further, for the preparation of the soldering flux solution, ethanol, triethanolamine, nonylphenol polyoxyethylene ether, phenolic resin, and hydrogenated rosin are placed in a heating container and then heated and stirred on a magnetic heating stirring device at a magnetic stirring speed of 50 - 200 rpm / min. After heating to 40 - 60 °C, keep warm and continue stirring for half an hour.

[0012] Further, before the first finish rolling and the second finish rolling, the alloy rough rolling strip and the alloy thick strip are respectively etched with 1% dilute hydrochloric acid by mass concentration for the surface oxide layer, and then washed with clean water and dried.

[0013] Further, the remaining scraps after blanking in the above steps (4) and (5) are remelted and recycled.

[0014] The Sn42-In58 alloy preformed solder sheet prepared by the method of the present invention has an alloy melting point of 139 °C, which is much lower than the melting point of the Sn-Ag-Cu solder system (217 °C), and can effectively reduce the warpage and void ratio of the mounted chip.

[0015] The Sn42-In58 alloy preformed solder sheet prepared by the method of the present invention has accurate composition, stable performance, and is easy to store and transport. The preformed solder sheet has a complete shape, high dimensional accuracy, uniform distribution of the soldering flux on the surface of the solder sheet, and the production method is simple and efficient, with high production efficiency, suitable for mass production. Description of the Drawings

[0016] Figure 1 It is a photo of the welding test result for Comparative Example 1; Figure 2 It is a photo of the welding test result for Comparative Example 2; Figure 3 It is a photo of the welding test result for Comparative Example 3; Figure 4 It is a photo of the welding test result for Comparative Example 4; Figure 5 It is a photo of the welding test result for Example 1; Figure 6 It is a photo of the welding test result for Example 2; Figure 7 It is a photo of the welding test result for Example 3; Figure 8 It is a photo of the welding test result for Example 4. Detailed Embodiments

[0017] The content of the present invention will be further described below in conjunction with embodiments. Example 1

[0018] A preparation method of an Sn42-In58 alloy preformed solder sheet is as follows: (1) Weigh 294 g of Sn and 406 g of In, with the purity of both Sn and In being 99.99%. Add Sn into a crucible, place it in an intermediate frequency furnace, raise the furnace temperature to 250 °C, melt all the tin, keep it warm for 30 min, then add indium, melt all the indium, raise the furnace temperature to 200 °C, and keep it warm for 30 min to obtain an alloy solution; (2) Pour the alloy solution into an ingot mold to obtain a Sn42-In58 alloy ingot with a length of 200 mm, a thickness of 80 mm, and a width of 6 mm; (3) Rough roll the obtained Sn42-In58 alloy ingot using a hot rolling mill. The reduction per pass for rough rolling is maintained at 2 - 10 mm, and the rolling speed is 2 m / min. After multiple passes of rolling (the thickness after each pass is successively 70 mm, 60 mm, 50 mm, 40 mm, 35 mm, 30 mm, 25 mm, 20 mm, 18 mm, 16 mm, 14 mm, 12 mm, 10 mm, 8 mm, 6 mm, 4 mm, 2 mm), a Sn42-In58 alloy rough rolled strip with a thickness of 2 mm is obtained; (4) First, corrode the surface oxide layer of the Sn42-In58 alloy rough rolled sheet obtained from primary rolling with dilute hydrochloric acid with a mass concentration of 1%, then wash it with clean water and dry it. Then, conduct the first precision rolling using a hot rolling mill. Control the tension at the unwind end of the hot rolling mill to be 150 N, the tension at the rewind end to be 200 N, the rolling speed to be 0.8 m / min, and the reduction per pass to be maintained at 0.1 mm. After multiple passes of rolling (the thickness after each pass is successively 1.9 mm, 1.8 mm, 1.7 mm, 1.6 mm, 1.5 mm, 1.4 mm, 1.3 mm, 1.2 mm, 1.1 mm, 1.0 mm, 0.9 mm, 0.8 mm, 0.7 mm, 0.6 mm, 0.5 mm), a Sn42-In58 alloy thick strip with a thickness of 0.5 mm is obtained, and then use a blanking device to blank the alloy thick strip into thick sheets with a width of 5 mm; (5) First, corrode the surface oxide layer of the cut thick sheets with dilute hydrochloric acid with a mass concentration of 1%, then wash it with clean water and dry it. Then, conduct the second precision rolling using a hot rolling mill. Control the tension at the unwind end of the hot rolling mill to be 30 N, the tension at the rewind end to be 50 N, the rolling speed to be 0.4 m / min, and the reduction per pass to be maintained at 0.02 - 0.1 mm. After multiple passes of rolling (the thickness after each pass is successively 0.45 m, 0.40 mm, 0.3 mm, 0.25 mm, 0.2 mm, 0.18 mm, 0.16 mm, 0.14 mm, 0.12 mm, 0.10 mm), a Sn42-In58 alloy thin strip with a thickness of 0.10 mm is obtained, and use a blanking device to cut the alloy thin strip into thin sheets with a width of 2 mm; (6) Blanch the thin sheet material into an annular thin sheet with an outer diameter of φ(1 ± 0.01) mm, an inner diameter of φ(0.5 ± 0.01) mm, and a thickness of (0.1 ± 0.01) mm. The remaining scraps after blanking are recycled and remelted for subsequent processing; (7) Weigh 90 g of ethanol, 1 g of triethanolamine, 0.5 g of nonylphenol polyoxyethylene ether, 6 g of phenolic resin, and 2.5 g of hydrogenated rosin. Put the above raw materials into a beaker, place it on a magnetic heating and stirring device, set the magnetic stirring speed to 100 rpm / min, heat to 50 °C, keep warm and stir for half an hour to obtain a soldering flux solution; (8) Immerse the annular thin sheet in the soldering flux solution for 2 min, then take it out and place it in an oven for drying. The oven temperature is 70 °C and the drying time is 30 min to obtain the required Sn42-In58 alloy preform solder sheet. Example 2

[0019] A preparation method of an Sn42-In58 alloy preform solder sheet is as follows: (1) Weigh 420 g of Sn and 580 g of In. The purities of Sn and In are both 99.99%. Add Sn to the crucible, place it in an intermediate frequency furnace, raise the furnace temperature to 230 °C, melt all the tin, keep warm for 20 min, then add indium, melt all the indium, raise the furnace temperature to 180 °C, and keep warm for 10 min to obtain an alloy solution; (2) Pour the alloy solution into an ingot mold to obtain an Sn42-In58 alloy ingot with a length of 200 mm, a thickness of 50 mm, and a width of 10 mm; (3) Rough roll the obtained Sn42-In58 alloy ingot. The reduction per pass of rough rolling is kept at 2 - 10 mm, and the rolling speed is 1.5 m / min. After multiple passes of rolling, an Sn42-In58 alloy rough rolled strip with a thickness of 8 mm is obtained; (4) Conduct the first precision rolling on the Sn42-In58 alloy rough rolled sheet obtained from the initial rolling. Control the tension at the unwinding end to be 100 N, the tension at the winding end to be 150 N, the rolling speed to be 0.7 m / min, and the reduction per pass to be kept at 0.1 mm - 0.3 mm. After multiple passes of rolling, an Sn42-In58 alloy thick strip with a thickness of 1.0 mm is obtained, and then the alloy thick strip is blanked into thick sheets with a width of 10 mm; (5) Conduct the second precision rolling on the cut thick sheets. Control the tension at the unwinding end to be 20 N, the tension at the winding end to be 40 N, the rolling speed to be 0.5 m / min, and the reduction per pass to be kept at 0.02 - 0.1 mm. After multiple passes of rolling, an Sn42-In58 alloy thin strip with a thickness of 0.16 mm is obtained, and the alloy thin strip is cut into thin sheets with a width of 2 mm; (6) Cut the thin sheet into a square annular thin sheet with an outer length and width of (5 ± 0.01) mm × (5 ± 0.01) mm, an inner length and width of (2 ± 0.01) mm × (2 ± 0.01) mm, and a thickness of 0.16 ± 0.001 mm. The remaining scraps after blanking are recycled and remelted for subsequent processing; (7) Weigh 85 g of ethanol, 1 g of triethanolamine, 1 g of nonylphenol polyoxyethylene ether, 8 g of phenolic resin, and 5 g of hydrogenated rosin. Put the above raw materials into a beaker, place it on a magnetic heating and stirring device, set the magnetic stirring speed to 200 rpm / min, heat to 40 °C, keep warm and stir for half an hour to obtain a soldering flux solution; (8) Immerse the square annular thin sheet in the soldering flux solution for 3 min, then take it out and place it in an oven for drying. The oven temperature is 60 °C and the drying time is 50 min to obtain the required Sn42-In58 alloy preform solder sheet. Example 3

[0020] A preparation method of an Sn42-In58 alloy preform solder sheet is as follows: (1) Weigh 378 g of Sn and 522 g of In, and the purities of Sn and In are both 99.99%. Add Sn to the crucible, place it in an intermediate frequency furnace, raise the furnace temperature to 240 °C, melt all the tin, keep warm for 10 min, then add indium, melt all the indium, raise the furnace temperature to 190 °C, and keep warm for 20 min to obtain an alloy solution; (2) Pour the alloy solution into an ingot mold to obtain an Sn42-In58 alloy ingot with a length of 200 mm, a thickness of 60 mm, and a width of 15 mm; (3) Rough roll the obtained Sn42-In58 alloy ingot. The reduction per pass of rough rolling is kept at 2 - 10 mm and the rolling speed is 1.8 m / min. After multiple passes of rolling, an Sn42-In58 alloy rough rolled strip with a thickness of 5 mm is obtained; (4) First, corrode the surface oxide layer of the Sn42-In58 alloy rough rolled sheet obtained by primary rolling with 1% mass concentration of dilute hydrochloric acid, then wash it with clean water and dry it. Conduct the first finish rolling, control the tension at the unwind end to be 120 N, the tension at the rewind end to be 180 N, the rolling speed to be 0.6 m / min, and the reduction per pass to be kept at 0.1 mm - 0.3 mm. After multiple passes of rolling, an Sn42-In58 alloy thick strip with a thickness of 1.0 mm is obtained, and then the alloy thick strip is blanked into a thick sheet with a width of 10 mm; (5) The cut thick sheet is subjected to a second precision rolling. The tension at the unwinding end is controlled at 10 N, the tension at the winding end is 30 N, the rolling speed is 0.6 m / min, and the reduction per pass is maintained at 0.02 - 0.1 mm. After multiple passes of rolling, an Sn42-In58 alloy thin strip with a thickness of 0.12 mm is obtained. The alloy thin strip is cut into thin sheets with a width of 2 mm; (6) The thin sheet is blanked into circular thin sheets with a diameter of 1 mm and a thickness of 0.12 ± 0.001 mm. The remaining scraps after blanking are recycled and remelted for subsequent processing; (7) Weigh 89 g of ethanol, 0.5 g of triethanolamine, 0.2 g of nonylphenol polyoxyethylene ether, 3.3 g of phenolic resin, and 7 g of hydrogenated rosin. Put the above raw materials into a beaker, place it on a magnetic heating and stirring device, set the magnetic stirring speed at 50 rpm / min, heat to 60 °C, keep warm and stir for half an hour to obtain a flux solution; (8) Immerse the circular thin sheet in the flux solution for 1 min, then take it out and place it in an oven for drying. The oven temperature is 80 °C and the drying time is 20 min to obtain the required Sn42-In58 alloy preformed solder sheet. Example 4

[0021] A method for preparing an Sn42-In58 alloy preformed solder sheet is as follows: (1) Weigh 210 g of Sn and 290 g of In. The purities of Sn and In are both 99.99%. Add Sn to a crucible, place it in an intermediate frequency furnace, raise the furnace temperature to 250 °C, melt all the tin, keep warm for 25 min, then add indium, melt all the indium, raise the furnace temperature to 200 °C, and keep warm for 25 min to obtain an alloy solution; (2) Pour the alloy solution into an ingot mold to obtain an Sn42-In58 alloy ingot with a length of 200 mm, a thickness of 70 mm, and a width of 10 mm; (3) The obtained Sn42-In58 alloy ingot is subjected to rough rolling. The reduction per pass in rough rolling is maintained at 2 - 10 mm and the rolling speed is 2 m / min. After multiple passes of rolling, an Sn42-In58 alloy rough rolled strip with a thickness of 3 mm is obtained; (4) The Sn42-In58 alloy rough rolled sheet obtained from the initial rolling is subjected to the first precision rolling. Control the tension at the unwinding end at 150 N, the tension at the winding end at 180 N, the rolling speed at 0.6 m / min, and the reduction per pass at 0.1 mm - 0.3 mm. After multiple passes of rolling, an Sn42-In58 alloy thick strip with a thickness of 0.8 mm is obtained, and then the alloy thick strip is blanked into thick sheets with a width of 10 mm; (5) The cut thick sheet is first subjected to surface oxide layer corrosion with 1% (by mass concentration) dilute hydrochloric acid, then washed with clean water and dried. Then, the second precision rolling is carried out, with the tension at the unwinding end controlled at 20 N, the tension at the winding end at 30 N, the rolling speed at 0.6 m / min, and the reduction per pass maintained at 0.02 - 0.1 mm. After multiple passes of rolling, a Sn42-In58 alloy thin strip with a thickness of 0.1 mm is obtained, and the alloy thin strip is cut into thin sheets with a width of 2 mm; (6) The thin sheets are blanked into long strip-shaped thin sheets with a length of 1 mm, a width of 0.8 mm, and a thickness of 0.12 ± 0.001 mm. The remaining scraps after blanking are recycled and remelted for subsequent processing; (7) Weigh 90 g of ethanol, 0.8 g of triethanolamine, 0.8 g of nonylphenol polyoxyethylene ether, 3 g of phenolic resin, and 5.4 g of hydrogenated rosin. Put the above raw materials into a beaker, place it on a magnetic heating and stirring device, set the magnetic stirring speed at 50 rpm / min, heat to 60 °C, keep warm and stir for half an hour to obtain a flux solution; (8) Immerse the long strip-shaped thin sheets in the flux solution for 2 min, then take them out and place them in an oven for drying. The oven temperature is 70 °C and the drying time is 30 min to obtain the required Sn42-In58 alloy preformed solder pads.

[0022] The Sn42-In58 alloy preformed solder pads prepared in the above Examples 1 - 4 are used for chip mounting welding tests. The welding test method is as follows: ① Ensure that the welding surface is clean and there are no impurities affecting the welding quality; ② Use a pick-and-place machine to mount the tin-indium solder pads on the PCB; ③ Use a pick-and-place machine to mount the chip on the PCB; ④ Send it into a reflow soldering equipment for reflow soldering. The reflow soldering temperature is shown in Table 1; ⑤ After welding, perform point-by-point scanning through a laser scanning profiler to obtain the warpage; ⑥ After welding, use an x-ray detection device to obtain the void ratio.

[0023] As a control, the welding tests of SAC305 solder paste for chip mounting were repeated 4 times. The methods of the four welding tests are the same, and the interval positions of the PCB boards and the chip positions on the PCB boards are the same as those in the above tin-indium solder pad chip mounting welding test. The welding test method is as follows: ① Ensure that the welding surface is clean and there are no impurities affecting the welding quality; ② Print the solder paste on the PCB; ③ Use a pick-and-place machine to mount the chip on the PCB; ④ Send it into a reflow soldering equipment for reflow soldering. The reflow soldering temperature is shown in Table 2; ⑤ After welding, perform point-by-point scanning through a laser scanning profiler to obtain the warpage; ⑥ After welding, use an x-ray detection device to obtain the void ratio.

[0024] Table 1 Reflow Soldering Temperature Table for Tin-Indium Solder Pads

[0025] Table 2 Reflow Soldering Temperature Table of Sn-Ag-Cu Solder Paste

[0026] The chip warpage and void ratio of the examples and the control example are shown in Table 3 below Table 3 Chip Warpage and Void Ratio

[0027] The results show that: compared with the Sn-Ag-Cu solder, the Sn42-In58 alloy preform effectively reduces the warpage of the mounted chip and the void ratio of the solder joint

[0028] In the method of the present invention, the equipment and devices used, such as intermediate frequency furnaces, hot rolling mills, blanking equipment, magnetic heating stirring equipment, ovens, etc. are all prior art equipment. The raw materials used, such as tin, indium, ethanol, triethanolamine, nonylphenol polyoxyethylene ether, phenolic resin, hydrogenated rosin, etc. can all be commercially available

[0029] Unless otherwise specified, the percentages described in the present invention are all mass percentages

[0030] The above embodiments are only partial embodiments of the present invention and do not limit the protection scope of the present invention. Embodiments obtained by those skilled in the art through data modification within the scope defined by the claims of the present invention all fall within the protection scope of the present invention

Claims

1. A preparation method of a Sn42-In58 alloy preform solder slice, the components and mass percentages of the Sn42-In58 alloy being In 52 ± 0.5%, with the balance being Sn and unavoidable impurities; characterized in that, The preparation method is as follows: (1) Add tin into a crucible, heat it to 230 - 250 °C to melt the tin, keep it warm for 10 - 30 min, then add indium and melt all of the indium. Raise the furnace temperature to 180 - 200 °C and keep it warm for 10 min - 30 min to obtain an alloy solution; (2) Pour the alloy solution into an ingot mold to obtain a Sn42 - In58 alloy ingot with a casting thickness of 50 - 80 mm; (3) Rough - roll the obtained Sn42 - In58 alloy ingot. The reduction per pass of rough rolling is kept at 2 - 10 mm and the rolling speed is 1.5 - 2 m / min. After multiple passes of rolling, a Sn42 - In58 alloy rough - rolled strip with a thickness of 2 mm - 8 mm is obtained; (4) Conduct the first precision rolling on the Sn42 - In58 alloy rough - rolled strip. Control the tension at the unwinding end to be 100 N - 150 N, the tension at the winding end to be 150 N - 200 N, the rolling speed to be 0.6 - 0.8 m / min, and the reduction per pass to be kept at 0.1 - 0.3 mm. After multiple passes of rolling, a Sn42 - In58 alloy thick strip with a thickness of less than 1 mm is obtained, and then the alloy thick strip is blanked and cut; (5) Conduct the second precision rolling on the blanked and cut Sn42 - In58 alloy thick strip. Control the tension at the unwinding end to be 10 N - 30 N, the tension at the winding end to be 30 N - 50 N, the rolling speed to be 0.4 - 0.6 m / min, and the reduction per pass to be kept at 0.02 - 0.1 mm. After multiple passes of rolling, a Sn42 - In58 alloy thin strip with a thickness of < 0.2 mm is obtained, and then the alloy thin strip is blanked and cut; (6) Put ethanol, triethanolamine, nonylphenol polyoxyethylene ether, phenolic resin, and hydrogenated rosin into a heating container, heat and stir. The heating temperature is 40 - 60 °C to obtain a flux solution; (7) Immerse the blanked Sn42 - In58 alloy thin strip into the flux solution for 1 - 3 min and then take it out, place it in an oven to dry. The oven temperature is 60 - 80 °C and the drying time is 20 - 50 min to obtain a Sn42 - In58 alloy pre - formed solder sheet.

2. The preparation method of a Sn42-In58 alloy preformed solder sheet according to claim 1, characterized in that, The components and mass percentages of the flux solution are 85 - 90% ethanol, 0.5 - 1% triethanolamine, 0.2 - 1% nonylphenol polyoxyethylene ether, 3% - 8% phenolic resin, and 2% - 5% hydrogenated rosin.

3. The preparation method of a Sn42-In58 alloy preformed solder sheet according to claim 1 or 2, characterized in that, For the preparation of the flux solution, after putting ethanol, triethanolamine, nonylphenol polyoxyethylene ether, phenolic resin, and hydrogenated rosin into a heating container, place it on a magnetic heating and stirring device to heat and stir. The magnetic stirring speed is 50 - 200 rpm / min. After heating to 40 - 60 °C, keep it warm and continue to stir for half an hour.

4. The preparation method of a Sn42-In58 alloy preformed solder sheet according to claim 1 or 2, characterized in that, Before the first precision rolling and the second precision rolling, respectively, corrode the surface oxide layer of the alloy rough - rolled strip and the alloy thick strip with 1% mass - concentration dilute hydrochloric acid, then wash it with clean water and dry it.

5. The preparation method of a Sn42-In58 alloy preformed solder sheet according to claim 1, characterized in that, Remelt and recycle the remaining materials after blanking in the above steps (4) and (5).

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