Moisture Sensitivity Level

Classification Scale

Standardization of moisture susceptibility helps electronics manufacturers prevent component damage during reflow soldering. This classification is the moisture sensitivity level, which ranges from level one for non-sensitive parts to level six for highly sensitive parts. It determines the allowable floor life of components once removed from their sealed bags.

The level is printed on the barcode labels of the protective packaging.

Reflow Damage

Plastic components with high moisture levels can crack or delaminate during the high temperatures of reflow soldering. The trapped water vapor expands rapidly, creating internal stresses that lead to mechanical failures. This failure mode is often called the popcorn effect.

Tracking the moisture level helps prevent these expensive defect rates during the manufacturing process.

Storage Standard

Components with high sensitivity levels must be stored in specialized dry cabinets or sealed in moisture-barrier bags with desiccant. Level three components allow one hundred and sixty-eight hours of floor exposure before assembly. In contrast, level five components must be soldered within forty-eight hours of bag opening.

This differentiation ensures that each part receives appropriate environmental protection.

Testing Method

Qualification involves exposing test samples to controlled temperature and humidity before subjecting them to three reflow cycles. After the reflow, parts are inspected using acoustic microscopy to check for internal delamination or cracks. This test procedure is defined by standards such as IPC-J-STD-020.

The results are used to assign the correct sensitivity level to each new device type. Engineering teams review these scans to identify sub-surface damage that could bypass standard electrical testing. The scanning process is highly sensitive to the presence of micro-cracks at the leadframe interfaces, which is the primary failure location.