金丝的力学特征对球键合的微观组织和性能的影响

Effect of Mechanical Characteristics of Gold Wire on Microstructure and Properties of Ball Bonding

用电子背散射衍射仪对具有不同力学特征金丝的微区组织进行表征,采用扫描电镜和光学显微镜观察线弧轮廓、热影响区和焊点形貌,并通过推拉力测试仪测量线弧拉力和焊球剪切力,分析金丝力学特征对球键合质量的影响。结果表明:半硬态1和半硬态2的金丝芯部保持纤维状组织,边缘晶粒为细小的等轴晶,沿径向微区组织形貌有明显差异。打火烧球后形成的热影响区长度短,球颈部的组织有明显的梯度性,键合后弧高较小。软态金丝的组织为粗大的等轴晶,沿径向分布均匀,键合拉力低,易发生滑球现象。半硬态2金丝与焊盘的结合力强,引线键合拉力高,综合键合质量优,是最适合球键合工艺的金丝。

Microstructure of gold wires with different mechanical characteristics was characterized by electron backscattering diffractometer.The loop profile,the heat affected zone and bonding point morphology were observed by scanning electron microscopy and optical microscopy,and the pulling force and ball shear force were measured by push-pull tester.Finally,the influence of mechanical characteristics of gold wires on the ball bonding quality was analyzed.The results show that there is obvious difference in microstructure along the radial direction.The core of the gold wire in semi-hard state 1 and 2 retains fibrous structure,and the edge grains are fine equiaxed grains.The length of the heat affected zone(HAZ)formed after forming the ball is short,the structure of the ball neck has obvious step,and the loop height after bonding is small compared with the soft state.The soft gold wire shows coarser equiaxed crystal,lower pulling force,and is prone to ball slip.The gold wire in semi-hard 2 state has strong bonding force to the pad,high pulling force and excellent overall bonding quality,which is the most suitable for the ball bonding process.