Meaning
Ultra-sensitive analytical techniques use helium gas and vacuum chambers to detect and quantify extremely small leaks in sealed enclosures. The practice of vacuum helium mass spectrometry represents the primary method for validating the hermeticity of lithium-ion cell assemblies to ensure long-term durability. By evacuating the interior of a cell or placing the sealed cell inside an evacuated chamber, this method detects helium molecules that pass through microscopic weld cracks or seal pores.
The high sensitivity of this system can measure leak rates as low as ten to the minus ten atmospheric cubic centimeters per second, providing an exact measure of sealing performance.
System Architecture
Specialized equipment is required to perform these evaluations at high speed and with high accuracy. In vacuum helium mass spectrometry, the test apparatus consists of a vacuum chamber, a roughing pump, a turbomolecular pump, and a mass spectrometer tuned to mass-to-charge ratio four. The mass spectrometer ionizes the incoming tracer gas and measures the ion current, which is proportional to the leak rate.
This automated process provides rapid and repeatable results for high-volume manufacturing lines.
Testing Protocols
Standardized testing procedures define the steps for both overpressure and vacuum methods to suit different cell geometries. For cylindrical or prismatic cells, vacuum helium mass spectrometry often utilizes a chamber where the sealed, helium-filled cell is exposed to a hard vacuum. This method mimics the internal pressure stresses that can occur during cell operation or air transport.
Sourcing documents require suppliers to perform these tests on a statistical sample of every production run to ensure process stability.
Sourcing Strategy
Sourcing teams utilize this sensitive technique to audit the manufacturing consistency of cell suppliers. Mandating vacuum helium mass spectrometry ensures that the procured cells meet strict quality standards for electric vehicle battery packs.
