Quantifying Water Vapor Diffusion across Elastomer Pressure Sensor Seals
Water vapor diffusion across elastomer seals causes reference cavity pressurization and dielectric drift, requiring coulometric ISO 15105-2 verification.
Hermeticity Verification
Leak Rate
Mass spectrometer leak detection methods measure gas egress rates from sealed sensor cavities to confirm environmental isolation. In microelectronics packaging, hermeticity verification quantifies helium tracer gas flow through sub-micron seal defects. Standard helium fine leak testing bombards sealed enclosures with high-pressure tracer gas inside pressure vessels.
Measured tracer gas outflow indicates equivalent air leak rates across package seals. Testing applicability stops when package volumes fall below specified minimum cavity dimensions.
Mass Spectrometry
Vacuum chambers connected to tuned mass spectrometers isolate helium ion currents with high precision. During qualification testing, hermeticity verification determines baseline background gas concentrations prior to chamber evacuation. Ion collector current calibration relies on calibrated capillary reference leaks producing known mass flow rates.
Residual gas analysis identifies volatile organic contaminants alongside tracer gas signals.
Gross Leakage
Bubble testing and optical deflection methods detect large package voids that allow rapid tracer gas evacuation before fine leak sampling begins. Pre-conditioning cycles evaluate hermeticity verification under severe liquid fluorocarbon submersion and thermal stress cycles. Submersible fluorocarbon baths reveal bubble streams emerging from structural package fractures.
Qualification Threshold
Military standards define maximum allowable equivalent leak rates based on internal cavity volume limits. Calibration certificates state mass spectrometer sensitivity thresholds under controlled ambient temperatures. Polymer seal degradation over extended operational lifetimes increases long-term atmospheric moisture ingress.