全息干涉法在表面封装组件质量检测中的应用

Applications of holographic interferometry in surface mount technology

利用二次曝光全息干涉技术对表面封装组件(SMA)在功率循环中的离面变形场进行了测试。为解决从器件边缘到印制电路板(PCB)间干涉条纹级次的不连续问题,实验中采用了“搭桥”技术来处理表面封装器件(SMD)和PCB的变形失配;此外,全息干涉技术还被用于一个实际产品(硬盘驱动器)的无损在线检测。结果表明:模塑J引线封装体(PLCC)和PCB由于中心热源及材料的热膨胀系数差而导致离面弯曲变形;沿器件边缘,引线和焊点经历了非共面的离面变形;通过正常硬盘驱动电路板和失效板的干涉条纹数量的对比,能快速简捷地检测板的质量。

In this paper, the applications of holographic interferometry (HI) in surface mount technology are presented. Out of plane deformations of a PLCC PCB assembly induced by power dissipation are given by using Double exposure HI. To solve the problem of the fringes discontinue between two bodies of surface mount device and PCB, and to further determine the deformations of the SMD leads and solder joint, a “bright” technique is used in Double exposure HI measurements. Real time HI is used to test the whole hard disk board deformation during power cycling. A over heat device is found in the defective board. The results show that the HI is a quite effective tool for the studies of thermal mechanical behavior and quality control of SMT products.