夹杂物诱发超薄引线框架铜合金带材表面微裂纹缺陷的研究

Study on inclusion induced microcracking defects on surface of ultra-thin leadframe copper alloy strip

针对超薄引线框架铜合金带材表面出现的微裂纹问题,采用扫描电子显微镜(SEM)、X射线能谱仪(EDS)、金相显微镜、纳米压痕仪分别对其表面形貌、元素分布、金相组织和力学性能等进行了测试和分析,并根据微裂纹区域的变化探寻了其形成原因。结果表明:裂纹的平均长度在10μm左右,随机分布于铜合金带材的两侧,并垂直于轧制方向。铜合金在熔炼过程中发生了C、O元素的偏聚,生成了C、O、Cu夹杂物,由于轧制过程中基体发生变形,导致在夹杂物处产生了应力集中,形成了微裂纹。最后,根据表面微裂纹的产生原因对浇铸及轧制工艺提出了改进建议,减少了微裂纹的产生。

For the microcracks on the surface of ultra-thin lead frame copper alloy strip,the surface morphology,element distribution,metallographic structure and mechanical properties of copper alloy strip were tested and analyzed by scanning electron microscope(SEM),energy dispersive spectrum(EDS),crystallographic microscopy and nanoindenter,and the cause for the formation of microcrack regions according to their variations was discussed.The results show that the average length of cracks is about 10μm,and it distributes randomly on both sides of the copper alloy strip,and perpendicular to the rolling direction.The segregation of C and O elements occurs in the melting process of copper alloy,and C,O and Cu inclusions are generated.The matrix is deformed during the rolling process,and the stress concentration occurs at the inclusions,resulting in the formation of microcracks.Finally,according to the cause of microcracks on the surface,some suggestions are put forward to improve the casting and rolling processes and reduce the occurrence of microcracks.