In Line Phased Array Inspection of Encapsulated Battery Structural Adhesives
Inline phased array testing maps structural adhesive wet-out and void formation through metal pack enclosures in real time at production line speeds.
Attenuation Coefficient
Meaning
Measurement of exponential energy loss per unit distance along a wave path quantifies acoustic and electromagnetic signal decay through battery component materials. Signal amplitude decays as energy scatters off grain boundaries or absorbs into viscous electrolyte phases within a cell. The attenuation coefficient defines this logarithmic decay rate per millimeter of beam path length under controlled thermal conditions.
Applicability ceases once scattering becomes incoherent or background electronic noise exceeds signal amplitude.
Wave Dissipation
Viscous friction within liquid electrolyte and micro-cracking inside nickel-rich cathode particles convert acoustic wave energy into localized heat. Dense fully wetted separator matrices yield low loss rates, whereas delaminated active layers create severe acoustic impedance mismatches. Changes in the attenuation coefficient during fast-charging protocols signal lithium plating or localized gas generation before electrical voltage signatures capture the failure.
Material Response
Signal decay rates scale nonlinearly with excitation frequency across lithium-ion battery geometries. Higher excitation frequencies improve spatial resolution while reducing effective penetration depth through thick graphite anodes.
Quality Standard
Cell manufacturing plants track the attenuation coefficient across high-throughput ultrasonic testing bays to screen un-wet regions after electrolyte injection. Automated transducers scan cell surface coordinates, mapping signal decay to verify uniform electrolyte wetting before formation cycling begins. Pouch cells exceeding baseline attenuation limits undergo extended vacuum soaking or scrap routing.
Production yield improves when un-wet cells are diverted prior to formation charging.