Abstract: Starting from printed circuit board(PCB) welding process and based on the growth mechanism of conductive anodic filament(CAF),ANASYS simulation was used to analyze the influence mechanism of thermal stress on the stress and strain of PCB dielectric layer in different welding conditions,which better explained the reason why the probability of cracks was greater in the core plate area of longitudinal structure in the actual failure products. At the same time,through the experimental analysis,the influence of soldering heat on the dielectric layer between plated through hole and anti-CAF performance. The results showed that thermal stress could lead to the increase of white fiber diameter and crack length,which provided a channel for CAF to reduce anti-CAF performance of PCB. For plates with different curing systems,the defect characteristics of materials after being soldered were also different. Finally,based on CAF experimental data and Bell Labs model to analyze the CAF life,the method to determine the safe hole wall spacing in the product design process was obtained,which provided design for manufacture and design for reliability reference for product design.