高密度封装基板镀层酸蚀针孔的形成机理及优化方案的研究

Study on Forming Mechanism and Optimization Scheme of Acid Etched Pinhole of High-Density Package Substrate

本文研究了封装基板经酸蚀减薄后镀铜层出现麻点的失效情况,通过金相显微镜、扫描电镜、能谱分析仪、氩离子截面抛光仪等宏微观测试方法和表征手段,对封装基板电镀铜层的生长过程和针孔的形成过程进行了分析论述,发现在正常的电镀工艺中会随机出现一些铜晶粒缺陷,酸蚀过程中异常晶粒整体脱落,导致麻点的产生.缺陷会造成腐蚀速度的不均匀,并引发毛细增溶效应,对此我们提出改进方案,在腐蚀液中添加半胱氨酸等铜离子的配体化合物,可使铜离子不同晶面的溶解速度发生改变,留下慢溶晶面,使针孔现象不容易发生,实验结果表明针孔数目明显减少,优化方案的改进效果显著.

In this paper,the failure of pitted copper plating layer after acid erosion on package substrate was studied,and the growth process and pinhole formation process of copper plating layer on package substrate were analyzed and discussed by macro and micro testing and characterization methods,such as Metallographic Microscope,Scanning Electron Microscope,Energy Dispersive Spectrometer,Argon-ion Cross Section Polisher.It was found that some copper grain defects occurred randomly in normal plating process,and abnormal grains fell off in the whole process of acid erosion,which resulted in the appearance of pinholes.Defects will cause uneven corrosion velocity and lead to capillary solution-increasing effect.Therefore,we put forward an improved plan to add cysteine to the corrosion solution to form ligand compounds of copper ions,which can change the dissolution velocity of copper ions at different crystal surfaces,hence slow solution crystal surfaces were left and pinholes would be less likely to occur.The experimental results show that the number of pinholes is significantly reduced,and the improvement effect of the optimization scheme is remarkable.