针对微焊点服役过程中由大温度梯度导致的热迁移问题,设计了一种热迁移试验装置,研究了复合钎料/Cu钎焊接头热迁移过程中的组织演变与力学性能.研究结果表明:设计的试验装置可满足单一热迁移试验条件.与未热加载时相比,Ni-GNSs增强Sn2.5Ag0.7Cu0.1RE复合钎料/Cu钎焊接头热迁移200 h后,接头热端Cu6 Sn5界面金属间化合物(IMC)大幅减薄并在界面出现微孔洞;冷端界面粗大扇贝状IMC厚度明显增加,冷端Cu/Cu6 Sn5界面间生成平均厚度1μm的层状IMC Cu6 Sn5.热加载200 h后,钎焊接头剪切强度降低33％.复合钎料钎焊接头断裂位置由热端界面IMC/钎缝的过渡区向界面IMC方向迁移;随热加载时间增加其断裂机制由韧性断裂向先转变为以韧性断裂为主的韧-脆混合断裂,再转变为以脆性断裂为主的韧-脆混合断裂.Ni-GNSs增强相的添加可抑制复合钎料/Cu钎焊接头的热迁移.

借助扫描电子显微镜、能谱仪、X射线衍射仪和微剪切试验等手段,研究了镀镍还原氧化石墨烯(Ni-rGO)增强Sn2.5Ag0.7Cu0.1RE复合钎料/Cu钎焊接头电迁移组织与性能.研究结果表明:在恒温120℃、电流密度1×104 A/cm2条件下,随着通电时间的增加,Ni-rGO增强Sn2.5Ag0.7Cu0.1RE复合钎料/Cu钎焊接头电迁移阳极区金属间化合物(IMC)层Cu6Sn5和Cu3Sn平均厚度增大,阴极区界面IMC层Cu6Sn5平均厚度减小、Cu3Sn平均厚度先增大后减小.Ni-rGO的添加,明显抑制了Ni-rGO增强Sn2.5Ag0.7Cu0.1RE复合钎料/Cu钎焊接头电迁移阳极区Cu6Sn5的生长及阴极区微空洞的生成,提高了钎焊接头剪切强度.通电72 h后,Ni-rGO增强Sn2.5Ag0.7Cu0.1RE复合钎料/Cu钎焊接头的剪切强度较未添加Ni-rGO的提高了47.8％.复合钎料/Cu钎焊接头电迁移剪切断裂,由阴极钎缝区呈以韧窝为主的韧性断裂,向界面IMC由解理、准解理和少量韧窝组成的混合型断裂转变.

The spreading and wetting behaviors of Sn2.5Ag0.7Cu0.1RE0.05Ni lead-free solder on the surface of Cu substrate under ultrasonic vibration were studied by SEM, EDS and other methods. The ultrasonic time was 1, 2, 3, 4, 5 s, respectively and was compared with the spreading of solder in the condition of soldering flux. The results showed that the Sn2.5Ag0.7Cu0.1RE0.05Ni solder was forced to spread instantly on the base metal surface under the action of ultrasonic vibration, and the ultrasonic cavitation can crush the oxide film on the surface of solder and base metal, resulting in the wetting of liquid solder and base metal. When the ultrasonic time was 3 s, the spreading area and spreading ratio of the solder achieved the maximum, and the ultrasonic cavitation could break the β-Sn and eutectic structure of the solder during solidification, refining the microstructure and improving the hardness of the solder matrix.