【摘要】 为了优化汽车电子用高可靠性焊料SAC-SBN合金的焊接工艺，探讨了不同冷却速度对SAC-SBN焊料合金及其焊点微观组织的影响。结果表明，SAC-SBN合金中的组织随着冷却速度的降低而逐渐粗化。冷却速度为48℃/s条件下合金组织细化程度最佳，而冷却速度为0.13℃/s下合金中IMC发生粗化，且合金中Bi元素出现晶界偏析现象。与传统SAC305合金对比，在焊点界面处，SAC-SBN焊点的IMC晶粒数量多且尺寸小，这归因于Bi元素在界面晶界处的析出，其促进了（Cu, Ni）₆Sn₅的异质成核生长。冷却速度为48℃/s时，SAC-SBN焊点界面IMC层最薄，为1.96μm,但由于热膨胀系数差异导致界面处应力较大，界面IMC层出现孔洞。冷却速度为0.13℃/s时，焊点IMC层最厚，为3.18μm,且由于界面反应与熟化机制，合金Sn基体与IMC之间存在应力，导致界面处IMC层和焊料内部熟化长大的（Cu, Ni）₆Sn₅处均存在孔洞。冷却速度为1.33℃/s时，焊点组织细密，无明显缺陷。更多还原

【Abstract】 In order to optimize the welding process of high reliability solder SAC-SBN alloy for automotive electronics, the influence of different cooling rates on microstructure of the SAC-SBN solder alloy and its solder joints was investigated. The test results indicate that the microstructure of the SAC-SBN alloy gradually coarsens with the decrease of cooling rate. Under the condition of a cooling rate of 48 ℃/s, the refinement degree of the alloy structure is optimal, while at a cooling rate of 0.13 ℃/s, the intermetallic compound（IMC） coarsens in the alloy and the Bi element exhibits grain boundary segregation. Compared with traditional SAC305 alloy, the SAC-SBN solder joints have a larger number and smaller size of IMC grains at the solder joint interface, which is attributed to the precipitation of Bi element at the interface grain boundary, which promotes the heterogeneous nucleation growth of（Cu, Ni）₆Sn₅. When the cooling rate is 48 ℃/s, the IMC layer at the SAC-SBN solder joint interface is the thinnest, as 1.96 μm. However, due to the difference in thermal expansion coefficients, the stress at the interface is relatively high, and voids appear in the IMC layer at the interface. When the cooling rate is 0.13 ℃/s, the IMC layer of the solder joint is the thickest, as 3.18 μm. And due to the interface reaction and maturation mechanism, there is stress between the Sn alloy matrix and IMC, resulting in voids in both the IMC layer at the interface and the（Cu, Ni）₆Sn₅ that has matured and grown inside the solder. When the cooling rate is 1.33 ℃/s, the solder joint structure is fine and there are no obvious defects.更多还原