基于多物理场的焊球缺陷检测方法

摘要

为检测倒装焊芯片在生产和服役过程中产生的焊球缺陷,提出了基于电、磁、热多物理场的脉冲涡流热成像检测方法.该方法利用有限元COMSOL软件建立焊球电磁感应热模型,并引入常见的焊球缺陷(空洞和裂纹)进行仿真;提取焊球顶端的温度分布,分析不同缺陷焊球的传热性能并进行缺陷识别;仿真分析裂纹和空洞尺寸变化对温度分布的影响,定量分析焊球缺陷.结果表明:在加热结束时,裂纹(长200μm,高20μm)焊球、空洞(直径150 μm)焊球与正常焊球的顶端温度差为一负一正,根据焊球顶端温度的分布特征可以区别不同缺陷焊球,对于裂纹焊球,当裂纹位置越靠近焊球顶端,温度值越高;对于空洞焊球,空洞半径从35 μm增大到75 μm时,焊球顶端温度呈线性增加.%A pulsed eddy current thermal imaging method that is based on a coupled electric,magnetic,and thermal physical field was proposed for defect detection of solder balls in the production and service process of flip chips.In this method,an electromagnetic-thermal model for solder balls was established using the finite element software COMSOL.Through this model,temperature distributions on the top surface of solder balls were extracted to analyze their thermal conduction properties and identify their defects (i.e.,voids and cracks).The effects of defect size (crack length or width and void radius) on the temperature distribution were discussed for quantitative analysis of solder ball defects.Simulation results show that at the end of heating,the solder ball with a crack of length 200 μm and height 20 μm has a higher surface temperature than the normal solder ball,while the solder ball with a void of diameter 150 μm has a lower surface temperature.The surface temperature rises when there exists a crack close to the top surface of the ball,but increases linearly for voided solder balls when the void radius increases from 35 to 75 μm.Therefore,solder balls with different defects can be identified according to their surface temperature distribution.