钎焊温度对Sn58Bi-1.5Al_2O_3/Cu微焊点组织及性能的影响

Effect of the Soldering Temperature on the Structure and Properties of Sn58Bi-1.5Al_2O_3 Micro Solder Joint

采用超声协振复合钎焊新技术制备Cu/Sn58Bi-1.5Al_2O_3/Cu微焊点,通过微观组织观察、显微硬度测试和拉伸性能检测,综合评定钎焊温度对焊点组织和性能的影响.研究结果表明:随着钎焊温度从200、220、240℃逐步提高到260℃,钎料合金的组织粗化,细小的点状过渡到层片状,Bi相面积占比也从56.73%逐步提高到62.66%;并且界面IMC层厚度逐步变厚,在90℃经高温时效100h后,IMC的形貌也由原来的扇贝状变为明显的块状,单一的Cu_6Sn_5薄层也增厚为Cu_6Sn_5和Cu_3Sn两层界面;复合钎料合金的显微硬度逐步提高,而焊点的拉伸强度则逐步下降,且高温时效后比时效前下降的幅度更为明显,钎焊温度越高,高温时效对抗拉强度的影响越大,焊点的可靠性越低.

New ultrasonic-assisted soldering technology was adopted to weld Cu/Sn58Bi-1.5Al_2O_3/Cu mini butt joints. Through microstructure observation, micro hardness experiment,and tensile test to evalu- ate comprehensively the effect of soldering temperature on the microstructure and properties of solder joint. The results show that with the soldering temperature from 200 ℃ ,220 ℃ ,240 ℃ to 260 ℃ ,the mi- crostructure of soldering alloy coarsened, the small pods transited to lamellar structure, and the proportion of Bi phase area also gradually increased from 56.73% to 62.66%. The thickness of the interface IMC layer gradually thickened, after aging at 90 ℃ for 100 hours,the shape of the IMC also changed from the original scallop to the obvious block,and the single Cu6 Sn5 thin layer is also thickened to two layers of Cu6 Sn5 and Cu3 Sn phases. The micro hardness of the composite solder alloy gradually increased, while the tensile strength of the solder joint gradually decreased, and the decline after the high temperature aging is more obvious than the pre aging. The higher the soldering temperature, the greater the influence of high temper- ature aging on tensile strength, and the lower the reliability of solder joints was.