Numerical simulation and interconnection of high-density deep hole solder joints based on magnetothermal synergy

Objective The aim is to address challenges of bridging, insufficient solder fill rate and void formation in the interconnection of high-density micro-deep hole solder joints. Methods A magnetic-thermal coupling model with 2.54 mm pitch is developed on the COMSOL Multiphysics platform to systematically investigate effects of soldering time and pin length on magnetic field intensity and temperature distribution, with the aim of optimizing soldering parameters. Results The results demonstrates that soldering time significantly governs temperature regulation. When heating duration increases to 10 s, temperature of solder joints reaches 300 °C. By analyzing the optimal soldering temperature window (210～230 °C) for Sn63Pb37 solder, a 5 s heating cycle is identified to maintain both upper and lower regions of solder joints within the ideal temperature range, ensuring complete solder wetting and cavity filling. Concurrently, temperature of adjacent solder joints remains below 100 °C, effectively preventing bridging defects caused by secondary reflow. Pin length exhibits limited influence on temperature field, yet its dimensional increase reduces ferrite core installation space, inducing magnetic structure misalignment. Parameter scanning shows that magnetic field intensity at the upper and lower regions of target joints is stable at 0.045 T and 0.030 T, respectively, surpassing adjacent joints by two orders of magnitude. Conclusion Technical superiority of focused induction heating in precise magnetic field control offers an effective solution for interconnection of high-density micro-scale solder joints.