Development of Sonotrode with Multiple-Pad Replaceable Tip for Use in the Ultrasonic Welding Process

Among technologies that are being used for joining foil-to-tab, tab-to-tab, and tab-to-bus in lithium-ion batteries, ultrasonic metal welding (UMW) is an effective welding method because it is a solid-state process and excels at welding dissimilar materials. It is also an excellent choice when joining multiple layers of the highly conductive materials used in batteries. Although it requires low input power and welds in fractions of a second, it has its own limitations, including the wear of sonotrode's knurl pad which requires complete replacement of the sonotrode. This is a limiting factor for battery manufacturers who are dealing with tens of thousands of welds per day. To reduce the tool cost, maintenance cost, and welder downtime, FEA was used in this study to aid in the design of two 20-kHz sonotrodes with multiple-pad replaceable tips made from tungsten carbide. Mechanical fasteners and a braze joint were used to attach the tip to the sonotrode. Once the sonotrodes were designed, they were manufactured, characterized, and tested to evaluate the performance of each attachment technique. The results of this study showed that while attaching the tip to the sonotrode using mechanical fasteners can be applicable for higher frequencies applications (e.g., 40–60 kHz) with lower amplitudes, braze joint can be used for applications that need higher amplitudes.