Electronic components can absorb moisture. When going through the reflow process, the absorbed moisture is rapidly heated. This can result in excessive pressure inside the component package. Excessive pressure can cause delamination and internal mechanical damage. The electronics industry has come up with Moisture Sensitivity Level (MSL) rating which defines the floor life between the time the drypack packing is opened and the time when the component goes through a reflow cycle. The absorption of moisture on the factory floor prior to PCB mounting is proportional to the ambient temperature and relative humidity. The MSL specification is provided with respect to 30°C and 60% relative humidity.

The MSL rating for each product can be found in the product data sheet in the package option addendum section. Alternatively, the MSL rating can be found under the Quality section in module product folder on TI.com. The MSL rating is also located on the product packaging label. See Figure 4-1.

Figure 4-1 MSL Information Available at Various Locations