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Method for refining eutectic structure of Sn-Bi alloy

A eutectic structure and alloy technology, applied in metal processing equipment, welding media, welding/cutting media/materials, etc., can solve the problems of easy roughening and reduced welding reliability, achieve good refining effect and hinder crystal grains The effect of growing up and shortening time

Inactive Publication Date: 2017-10-20
UNIV OF JINAN
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

In addition, Sn-Bi solder is very easy to coarsen during service, resulting in a significant decrease in soldering reliability. Therefore, how to improve the high temperature stability of Sn-Bi alloy is also one of the key issues for the wide application of Sn-Bi solder.

Method used

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  • Method for refining eutectic structure of Sn-Bi alloy
  • Method for refining eutectic structure of Sn-Bi alloy
  • Method for refining eutectic structure of Sn-Bi alloy

Examples

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Embodiment 1

[0029] The atomic percentage composition of the alloy of the embodiment of the present invention is 56.4 at.% tin, 42.5 at.% bismuth, 1.0 at.% lanthanum and unavoidable impurities.

[0030] Take the following steps to make:

[0031] (1) Completely melt metal tin (Sn) and bismuth (Bi), and keep it at 250°C for 10 minutes to ensure that the melt is a uniform single liquid phase;

[0032] (2) Add Sn-La rare earth additives and keep warm at 400°C for 20 minutes to ensure full melting of rare earth elements and uniform distribution of elements in the melt;

[0033] (3) The alloy melt is poured into a mold to obtain a Sn-Bi cast alloy.

[0034] figure 1 Components, rare earth additives, phase composition, layer spacing and mechanical properties of the samples of the comparative example and each embodiment of the present invention. Depend on figure 1 It can be seen that the lamellar spacing of the eutectic structure of the alloy in this example is 4.5 μm, the hardness is 420.3 MP...

Embodiment 2

[0036] The atomic percentage composition of the alloy of the embodiment of the present invention is 55.8 at.% tin, 42.1 at.% bismuth, 2.0 at.% lanthanum and unavoidable impurities.

[0037] Take the following steps to make:

[0038] (1) Completely melt metal tin (Sn) and bismuth (Bi), and keep it at 300°C for 20 minutes to ensure that the melt is a uniform single liquid phase;

[0039] (2) Add Sn-La rare earth additives and keep warm at 550°C for 20 minutes to ensure full melting of rare earth elements and uniform distribution of elements in the melt;

[0040] (3) The alloy melt is poured into a mold to obtain a Sn-Bi cast alloy.

[0041] figure 1 Components, rare earth additives, phase composition, layer spacing and mechanical properties of the samples of the comparative example and each embodiment of the present invention. Depend on figure 1 It can be seen that the lamellar spacing of the eutectic structure of the alloy in this example is 3.2 μm, the hardness is 431.0 MP...

Embodiment 3

[0043] The atomic percentage composition of the alloy of the embodiment of the present invention is 55.3 at.% tin, 41.6 at.% bismuth, 3.0 at.% lanthanum and unavoidable impurities.

[0044] Take the following steps to make:

[0045] (1) Completely melt metal tin (Sn) and bismuth (Bi), and keep it at 350°C for 20 minutes to ensure that the melt is a uniform single liquid phase;

[0046] (2) Add Sn-La rare earth additives and keep warm at 650°C for 30 minutes to ensure full melting of rare earth elements and uniform distribution of elements in the melt;

[0047] (3) The alloy melt is poured into a mold to obtain a Sn-Bi cast alloy.

[0048] figure 1 Components, rare earth additives, phase composition, layer spacing and mechanical properties of the samples of the comparative example and each embodiment of the present invention. Depend on figure 1 It can be seen that the lamellar spacing of the eutectic structure of the alloy in this example is 2.1 μm, the hardness is 464.7 MPa,...

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Abstract

The invention discloses a method for refining the eutectic structure of Sn-Bi alloy, and particularly relates to a simple low-cost preparation method. The method is characterized in that rare earth alloy (Sn-La or Sn-La-Ce) is used as a modificator or a refiner, the surface activation effect of rare earth elements can promote nucleation in the alloy solidification process, and metamorphic homogenization of solder alloy is facilitated; in addition, compounds (LaBi2 and CeBi2) subjected to in-situ precipitation in the solidification process can also serve as a heterogeneous nucleation core of a Bi phase, and the nucleation rate of the Bi phase is increased; and rare earth single phases (La and Ce) subjected to in-situ precipitation can also effectively hinder growing of grains, coarsening of the grains in the service process is inhibited, the aging service strength of a welding head is improved, and the service life of the welding head is prolonged. The preparation method is simple and feasible in technology, low in cost, remarkable in refining effect, capable of preparing the Sn-Bi as-cast alloy provided with the fine eutectic structure easily, and suitable for industrialized quantity production.

Description

1. Technical field [0001] The invention relates to a method for refining the eutectic structure of a Sn-Bi alloy, belonging to the technical field of metal material preparation. 2. Background technology [0002] With the strengthening of people's awareness of environmental protection, the rapid development of the electronics industry and the promulgation of relevant laws and regulations, more and more people advocate the use of green and pollution-free lead-free products. Today's most representative lead-free solder alloys are based on Sn and alloyed with other elements. Four kinds of Sn-Bi lead-free solders instead of Sn-Pb solders have the advantages of low melting point, good solderability and high joint strength. However, the plasticity and toughness of Sn-Bi lead-free solder is poor, which greatly limits its application in the electronic packaging industry, especially in the field of low-temperature lead-free soldering. At present, the method for refining the eutectic...

Claims

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Application Information

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IPC IPC(8): C22C12/00C22C1/03B23K35/26
CPCC22C12/00B23K35/264C22C1/03
Inventor 贾鹏杨中喜张金洋
Owner UNIV OF JINAN