Meaning
Non-destructive evaluation of electronic and electrochemical components relies on phase-sensitive thermal imaging to locate microscopic defects. The analysis of modulated thermal waves known as lock-in thermography allows researchers to detect localized current paths and micro-shorts with high spatial resolution. This technique is applied in quality control to inspect cell pouch seals and electrode coatings during or after assembly.
Excitation Source
Active thermal imaging requires the application of a periodic energy input to generate detectable thermal waves within the test object. In a lock-in thermography setup, a modulated electrical current or a pulsed light source stimulates the cell. This periodic excitation generates localized heat at defects, which is monitored by an infrared camera synchronized with the excitation frequency.
The resulting lock-in thermography amplitude and phase images show the distribution of heat source density, which reveals the internal structural defects of the battery.
Defect Resolution
Sifting through background noise is essential when attempting to isolate minute thermal variations in high-capacity cells. By averaging thermal images over multiple modulation cycles, lock-in thermography isolates tiny heat signatures that are otherwise hidden by uniform heat dissipation. This process allows inspectors to pinpoint the exact location of micro-shorts and electrode inconsistencies.
Manufacturing Integration
Quality assurance in automated battery assembly lines uses rapid non-contact diagnostic tools to maintain high production yields. Implementing lock-in thermography in the inspection phase allows for the early rejection of defective cells before they are integrated into larger packs. This diagnostic capability reduces the risk of field failures and enhances the overall reliability of the battery system.
