SMT Moisture Sensitivity Level Classifications and Floor Life Limits
Component floor life compliance requires strict tracking, verified moisture barrier packaging, and controlled bake protocols before surface reflow.
Desiccant Units
Absorptive Medium
Drying agents sealed inside moisture barrier bags absorb trace water vapor to protect surface mount components during extended storage. Active desiccant units lower the internal relative humidity below ten percent before heat sealing takes place. Verification of water absorption capacity occurs through weight gain measurements prior to packaging insertion.
Saturated material loses effectiveness and must be replaced before vacuum packaging.
Sizing Calculation
Mathematical formulas defined in packaging specifications determine the volume of drying material needed based on bag surface area and moisture vapor transmission rate. Solderable surface finish preservation depends on maintaining dry ambient conditions inside the sealed pouch. Technical calculations account for the internal bag area, water vapor permeability of the barrier film, and the maximum allowed storage duration.
When flexible packaging contains moisture sensitive devices, desiccant units absorb incoming moisture that migrates through thin polymer layers over time. Exceeding the calculated storage time saturates the drying medium and exposes delicate component leads to ambient humidity during transit.
Environmental Boundary
Atmospheric exposure during packaging operations reduces active capacity before sealing completes. Operators track exposure time on assembly floors to prevent premature saturation of desiccant units prior to vacuum sealing. Solderability testing identifies oxidation on terminal leads when protective packaging fails.