Electrochemical Characterization and Impedance Matching in Parallel Cell Strings
Dynamic impedance matching and symmetrical busbar resistance prevent destructive circulating currents and accelerated capacity fade in parallel cell strings.
Wedge Bonding
Meaning
Ultrasonic wire bonding process connecting thin metal wires or ribbons to semiconductor substrates and battery cell terminals. Manufacturing lines utilize wedge bonding to attach interconnect wires between cell tabs and circuit boards or busbars. The solid-state process forms low-resistance electrical joints without applying high thermal energy to delicate cell structures.
Interconnect Joining
Aluminum or copper wire passes through an angled tool called a wedge, which presses the wire against the target bonding pad. High-frequency ultrasonic energy applied under controlled mechanical force plastically deforms the wire and substrate surface at room temperature. Interatomic bonds form across the contact interface to create a durable, highly conductive joint.
Process Mechanics
Ultrasonic transducer frequency, bonding force, power duration, and tool geometry determine the mechanical and electrical quality of the weld. Flat wedge surfaces create a rectangular bond footprint with high shear strength and low electrical contact resistance. Automated bonding heads execute multiple wire bonds per second with sub-micron positioning accuracy.
Surface cleanliness remains critical because microscopic organic oil or oxidation layers impede plastic deformation at the weld interface. Transducer vibration profiles are dynamically controlled to adjust power delivery as wire hardness varies across production spools.
Quality Verification
Inline vision systems check bond placement, wire loop height, and footprint deformation immediately following the bonding process. Destructive pull and shear testing on sample coupons verify mechanical bond strength limits during production calibration runs. High bond strength ensures that interconnect wires withstand mechanical shock and vibration throughout operational life.