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A kind of sn-bi series low-silver lead-free solder alloy and preparation method thereof

A lead-free solder and alloy technology, used in metal processing equipment, welding equipment, manufacturing tools, etc., can solve the problem of reducing the shear strength of solder joints and the life of anti-drop impact, the safety hazards of electronic product service reliability, and the lubrication of solder. Wet spreadability, reduced mechanical properties, etc., to achieve the effects of excellent wet spreadability, solidification segregation inhibition, and high microhardness

Active Publication Date: 2021-07-20
SOUTH CHINA UNIV OF TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, the brittleness of the Bi phase, the coarsening of the Bi phase during the service of the Sn-Bi solder, and the segregation of the Bi element at the solder joint interface have seriously reduced the shear strength and drop impact life of the solder joint. , which brings great potential safety hazards to the service reliability of electronic products
However, in the current research, there are still few research results that can comprehensively improve the comprehensive performance of Sn-Bi based solder alloys.
For example, a low-melting-point lead-free solder disclosed in Chinese patent CN106695151A improves the wettability and comprehensive mechanical properties of the solder by reducing the Bi content to 16-18%, adding alloy elements such as Ag and Fe, but the alloy The melting point is 178-192°C, and the Bi content is far from the eutectic point, making it easier for the molten solder to form Bi segregation during the cooling process; the solder disclosed in Chinese patent CN101380700A is based on Sn-Bi-Cu Adding 0.05-0.5% Zn on the top can inhibit the segregation of Bi element during the welding solidification process. However, it has been reported that the addition of Zn element can reduce the wettability and mechanical properties of the solder.

Method used

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  • A kind of sn-bi series low-silver lead-free solder alloy and preparation method thereof
  • A kind of sn-bi series low-silver lead-free solder alloy and preparation method thereof

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0031] Take by weighing pure Sn (99.95%) and pure Bi (99.9%) and Sn-20Ag, Sn-20Cu alloy according to the proportion that the bismuth content is 40%, the silver content is 0.5%, the copper content is 0.5%, and the remainder is tin. Melted in a crucible in a resistance furnace. The feeding sequence during smelting is as follows: first put pure Sn into the crucible, then put pure Bi particles into the crucible after complete melting, and finally put Sn-20Ag and Sn-20Cu alloys. Configure 100g of each solder alloy according to the composition in Table 1, the melting temperature is 350°C, stir evenly after all the raw materials are melted, keep warm for 30 minutes, stir once every 10 minutes during the heat preservation process, add a small amount of rosin to the solder solution before casting, and remove the scale The residue was finally cast to obtain the solder alloy of this embodiment.

Embodiment 2

[0033] Take by weighing pure Sn (99.95%) and pure Bi (99.9%) and Sn-20Ag, Sn-20Cu alloy according to the proportion that the bismuth content is 40%, the silver content is 0.5%, the copper content is 1.5%, and the remainder is tin. Melted in a crucible in a resistance furnace. The feeding sequence during smelting is as follows: first put pure Sn into the crucible, then put pure Bi particles into the crucible after complete melting, and finally put Sn-20Ag and Sn-20Cu alloys. Configure 100g of each solder alloy according to the composition in Table 1, the melting temperature is 350°C, stir evenly after all the raw materials are melted, keep warm for 30 minutes, stir once every 10 minutes during the heat preservation process, add a small amount of rosin to the solder solution before casting, and remove the scale The residue was finally cast to obtain the solder alloy of this embodiment.

[0034] Table 1 Solder alloy chemical composition (wt.%)

[0035]

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Abstract

The invention belongs to the field of solder alloys, and discloses a Sn-Bi low-silver lead-free solder alloy and a preparation method thereof. The solder alloy is composed of Sn, Bi, Ag and Cu, and the components in the solder alloy are calculated by mass percentage: Bi 40%, Ag 0.5%, 0.5%≤Cu≤1.5%, and the balance is tin. Its preparation method is as follows: after pure Sn is completely melted, add pure Bi grains to stir and smelt, then add Sn-20Ag and Sn-20Cu alloys to stir and smelt evenly, add rosin after heat preservation to remove scale residues, and cast to obtain Sn-Bi low-silver Lead-free solder alloy. The invention significantly reduces the melting range of the brazing filler metal by simultaneously adding two alloying elements, Ag and Cu, on the basis of the Sn-40Bi alloy, and greatly improves the wettability and microhardness of the brazing filler metal.

Description

technical field [0001] The invention belongs to the field of solder alloys, in particular to a Sn-Bi low-silver lead-free solder alloy and a preparation method thereof. Background technique [0002] For a long time, Sn-Pb series alloy solder has been widely used in the fields of automobile industry, electronics industry and so on because of its advantages of low cost, good mechanical properties, strong electrical conductivity and good processability. With the implementation of EU RoHS and WEEE directives, lead-free electronic products have become a global trend. In the process of seeking Sn-Pb solder substitutes, the most used lead-free solders are mainly SnAg alloys. Sn-3.5Ag binary eutectic solder alloy has high mechanical properties, but its melting point is as high as 221℃. The crystal temperature is 34°C, which greatly increases the assembly temperature, which means that a series of systematic projects such as the corresponding welding equipment, process, electronic c...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): B23K35/26B23K35/14
CPCB23K35/0222B23K35/262
Inventor 李继平卫国强韦静敏
Owner SOUTH CHINA UNIV OF TECH
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