Meaning
The permanent material bond formed by high frequency acoustic energy and mechanical pressure applied to thermoplastic components or metal foils inside an ultrasonic welding seam creates molecular or metallurgical interlocks. High frequency electrical oscillations convert into mechanical vibrations through a piezoelectric converter before a sonotrode transfers those oscillations directly to the stacked substrates under a controlled clamping force. Specific acoustic impedance matching between the sonotrode tip and the workpiece governs energy delivery efficiency, preventing thermal degradation outside the immediate joint interface.
High velocity frictional rubbing at the boundary breaks up oxide layers and surface contaminants, producing localized plastic flow without external melting. This metallurgical or polymer chain entanglement zone defines the boundary where mechanical strength equals or exceeds the parent material, ending where the horn contact footprint leaves physical indentation traces on the outer surface.
Acoustic Frequency
Generator output frequencies typically range between twenty kilohertz and forty kilohertz during battery tab and terminal assembly operations. Higher frequencies deliver smaller displacement amplitudes, suiting delicate foils and thin film stacks prone to tearing under excessive mechanical stress. Piezoelectric stack actuators expand and contract rapidly within that window, driving longitudinal waves through the booster and sonotrode directly into the target material.
Clamping Force
Pneumatic actuators apply a precise normal load to hold the components in firm contact against a stationary anvil throughout the acoustic burst duration. Insufficient pressure causes acoustic decoupling between the horn and the workpiece, generating excessive localized heat and surface burning rather than internal shearing. Excessive force suppresses microscopic interface slip, preventing frictional dissipation and stalling the acoustic stack before molecular diffusion can occur.
Weld Strength
Destructive peel testing and shear pull testing verify joint integrity against minimum tensile force thresholds required for high vibration battery module environments. Operator inspection checks for microcracks along the perimeter of the deformation zone, which indicate excessive horn amplitude or incorrect dwell times. Electrical resistance measurements across the bonded region confirm that solid state consolidation achieves low milliohm performance, preventing thermal hotspots during high current discharge cycles.
