Nonlinear Acoustic Shear Wave Detection of Zero Gap Kissing Bonds in Encapsulated Packs
Nonlinear acoustic shear wave harmonic detection resolves zero gap kissing bonds in encapsulated battery packs by measuring contact acoustic nonlinearity.
Surface Contamination
Meaning
The presence of unwanted particles, chemical residues, or moisture on the surface of battery electrodes or casing material degrades electrical contact and can cause internal short circuits during cell operation. Any surface contamination must be eliminated prior to cell assembly and filling because microscopic debris can damage the fragile separator or disrupt the weld quality of the terminals. Monitoring and cleaning these surfaces are standard steps in high-volume cell production.
Technical Consequence
When metal shavings or dust settle on the electrode during the slitting and winding processes, they can pierce the separator layer. This mechanical failure creates a direct electrical path between the anode and cathode, leading to localized heating and potential thermal runaway. Chemical residues like oil or grease on the casing prevent secure welding of the cell tabs, resulting in high contact resistance.
This localized resistance causes the battery to overheat under high current loads.
Mitigation Strategy
Cleanroom environments and automated vacuum systems are used to minimize the risk of airborne particulates contacting the raw materials. Electrodes are passed through contact cleaning rollers and ionized air knives before the winding step. In addition, laser cleaning systems are deployed to remove surface oxides from terminal tabs before welding.
These cleaning steps are verified using optical inspection cameras and surface tension test pens.
Sourcing Influence
Procurement contracts specify maximum allowable particle counts and surface tension values for incoming materials to ensure they meet cleanliness standards. Sourcing from suppliers who operate class 10,000 cleanrooms reduces the likelihood of contaminated cells entering the assembly line. This specification is a major factor when qualifying new raw material vendors.