Bi含量对Sn-0.3Ag-0.7Cu钎料微观组织及接头性能的影响
Influence of Bi Content on Microstructure of Sn-0.3Ag-0.7Cu Solder and Properties of Welded Joint
卫江红1， 权延慧2
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作者单位：1.德州学院，山东 德州 253023；2.山东华宇职业技术学院，山东 德州 253034
中文关键字：回流焊；低银；无铅钎料；剪切强度
英文关键字：reflow; low silver；lead-free solder；shear strength
中文摘要：以Sn-0.3Ag-0.7Cu低银无铅钎料为研究对象，添加不同量的Bi(1.0%~4.5%)元素，和Cu盘进行钎焊，取部分试样进行高温时效处理。观察分析了Bi对钎料微观组织结构的影响，以及Bi对焊接接头界面金属间化合物(IMC)显微形貌演变、生长动力学和接头剪切强度的影响。研究结果表明；Bi元素的加入使钎料基体内晶粒尺寸变得细化而均匀，且随着Bi含量的增加可以显著提高钎料钎焊接头的剪切强度，断口经过扫描电镜观察发现剪切断面均沿着剪切方向有明显的塑性变形，这表明焊点中发生的是塑性断裂；高温时效试验表明，钎料基体中Bi的存在降低了界面IMC的生长速率，且随着Bi含量的增加，抑制IMC生长的作用越大。但是过量的Bi会使组织粗化，且对IMC生长的抑制作用反而会变差。IMC层厚度随着时效时间的延长明显增加，断裂机制很快由钎料基体的韧性断裂逐渐变为界面IMC的脆性断裂，使焊接接头的剪切强度明显下降。
英文摘要：Taking Sn-0.3Ag-0.7Cu lead-free solder with low silver as research objects, different content of Bi (1 wt%~4.5wt%) is added, and then Cu plate is brazed, then the testing sample is taken into high temperature aging treatment. The microstructure and welded joint of interface intermetallic (IMC) microscopic morphology evolution, growth dynamics and joint shear strength were observed and studied. The results show that adding Bi can make the base body solder become fine. But the excess of Bi can make the microstructure become coarse, and the increase of Bi content can significantly improve the shear strength of solder joints, the fracture can be found that the shear section along the shear direction has significantly plastic deformation by SEM. The phenomenon shows that the plastic fracture occurs in solder joints; after high temperature aging, Bi existing in solder matrix can reduce the growth rate of interface intermetallic compounds. In a certain amount of range, with the increase of Bi content, the growth of the IMC would be larger. The inhibitory effect of the excess of Bi content on the growth of compounds would be worse. The IMC layer thickness significantly increases with the extension of aging time, the fracture mechanism changes quickly from the ductile fracture of solder matrix into the brittle fracture of intermetallic compounds, the shear strength of the welded joints undergos a significant decrease.