Ultrasound Tab Welding Microstructure and Joint Resistance Limits
Ultrasonic tab welding balances acoustic softening and static clamp force to break interfacial oxides, yielding sub-5-micro-ohm joints without foil cutting.
Sonotrode Amplitude
Meaning
Oscillatory displacement measurements describe the physical movement of the welding horn in an ultrasonic joining system. The sonotrode amplitude is the distance the tool travels during each vibration cycle and directly influences the friction generated at the material interface. It is the primary control variable for welding multiple layers of copper or aluminum foil.
Energy Transfer
Mechanical work is converted into thermal energy through the sliding motion of the metal surfaces under pressure. Higher sonotrode amplitude increases the rate of oxide layer removal and promotes the formation of a solid state bond.
Tool Frequency
Resonance must be maintained between the power supply and the vibrating assembly to achieve stable displacement. While the frequency is usually fixed by the hardware design, the sonotrode amplitude can be adjusted to suit different material thicknesses.
Friction Output
Surface shearing creates the plastic deformation necessary to intermix the metals at the atomic level. If the sonotrode amplitude is too low, the foils will not bond because the surface contaminants are not cleared away. Excessive displacement can lead to thinning of the top foil or cracking of the weld zone due to over-stressing the metal.
Finding the correct balance ensures a strong joint with low electrical resistance. Monitoring the output during production catches tool wear or loose components before they impact joint quality.