Acceptance Quality Limit Sampling Plans for Lithium Cell Receiving Facilities
Enforce ANSI ASQ Z1.4 Level II sampling with AQL 0.010 for critical safety flaws and Kelvin OCV IR screening to reject defective lithium cells at receiving dock.
Tab Weld Pull Strength
Meaning
Mechanical pull force required to separate the electrode tab from the current collector foils determines the structural integrity of the electrical connection. Measuring tab weld pull strength involves applying a tensile force to the welded joint until it fails. This test confirms that the ultrasonic or laser weld has created a robust metallurgical bond.
Joint Evaluation
Failures are categorized by the location of the break to determine the quality of the welding process. When testing tab weld pull strength, a failure in the weld nugget indicates insufficient energy during the welding process, while a break in the foil indicates a strong weld. This classification helps engineers adjust the weld pressure and energy settings.
Tensile Testing
Destructive tests are performed on a statistical sample of cells from each batch to monitor the stability of the welding machine. The measured tab weld pull strength must exceed a minimum threshold to ensure the cell can withstand the vibrations experienced during operation. This parameter directly affects the mechanical durability of the final pack.
Sourcing Specification
Buyers define the minimum acceptable force values in the quality agreement to guarantee product quality. Low tab weld pull strength values lead to immediate batch rejection, since poor welds can fail under thermal or mechanical stress, leading to high electrical resistance and potential localized heating. Sourcing teams rely on these force values to qualify new cell suppliers and establish consistent production standards.
When a new welding tool is introduced, a series of sample tests is carried out to ensure the bond strength meets these strict automotive standards before mass production begins.