Highly Stable Pin Pull Test Method for PCB Pad Cratering Characterization

Although the problem of pad cratering has become the focus of printed circuit board (PCB) manufacturing industry for nearly a decade, the existing test method and equipment have not been widely promoted in industrial usage. This approach is unsuitable for large-scale industrial application because the existing equipment and consumables are expensive, the test success rate is low, and the test procedure requires human operation. In this study, a pin pull test method is proposed; it implements highly stable soldering between the pull pin and the target pad through the optimized pins and soldering method, thereby greatly improving the pulling success rate and obtaining ideal adaptability for micro-pads with a diameter below 0.5 mm. In addition, the pull pin can be repeatedly used, effectively reducing testing costs. A stable control of the solder ball size without human intervention can be achieved with the unique solder ball generating method. The key parameters, such as the peak soldering temperature, pulling speed, and the matching relationship between pull pin and target pads, are studied in the experiment. The success rates of the test for 0.3- and 0.5-mm pads are validated, and the results indicate that the test stability on pad soldering and pulling is remarkably improved.