多次重熔过程中La2O3对Sn-58Bi钎料组织及性能的影响

为提高Sn-58Bi钎料的钎焊性,采用机械混合法制备了不同La2O3含量的Sn-58Bi低温无铅复合钎料.借助SEM、EDS和DSC等分析手段研究了La2O3对Sn-58Bi钎料显微组织、熔化特性以及力学性能的影响,并考察了多次重熔过程中Sn-58Bi-x La2O3/Cu界面IMC层组织演变.研究结果表明:La2O3的加入可以抑制大块富Bi相的偏析生成,但对钎料熔点的影响不大;在多次重熔过程中,同一种钎料的界面IMC层晶粒粒径随重熔次数的增加而增大,但La2O3的加入能有效阻碍界面IMC层晶粒粗化;加入不同含量La2O3后,复合钎料的硬度和模量都有一定程度的提高,其抵抗局部变形、开裂的能力提高,从而提高无铅钎料焊点在实际封装过程中的可靠性.

Effect of La2O3 particles on structure and properties of Sn-58Bi solder after multi-remelting

To improve the solderability of the Sn-58Bi solder, the Sn-58Bi composite solder reinforced with different mass fraction of La2 O3 particles was prepared by mechanical mixing method. The effect of La2 O3 particles on microstructures, melting characteristics and mechanical properties of the Sn-58Bi solder was investigated by SEM, EDS and DSC analytical methods, and the microstructure evolution of intermetallic layer along interface of Sn-58Bi-xLa2 O3/Cu soldered joint after multi?remelting was also discussed. Results indicated that the addition of La2 O3 particles to the solder inhibited the segregation orientation of large pieces of Bi?rich phase, but had no obvious effect on the soldered melting point. The grain size of the intermetallic layer along interface of the same soldered joint was increased with the increasing of remelting time, but the addition of La2 O3 particles to the solder hindered the grain coarsening of the intermetallic layer along interface. After adding different mass fraction of La2 O3 particles to the solder, the hardness and modulus of the composite solder and its ability of resistance to local deformation and cracking had been improved for a certain degree.