A chip is like a car: it must pass strict tests before it is allowed on the road, and AEC-Q100 is the chip's driving licence and the entry ticket to the automotive field.

MSL (moisture sensitivity level) is the classification system used in the electronics industry to assess how sensitive a component is to moisture. It divides components into eight levels according to moisture sensitivity, reflecting how long a component can be stored safely under specified temperature and humidity conditions without absorbing moisture that would affect performance or reliability. As a professional third party testing body, NTEK provides comprehensive automotive related testing to ensure the performance and reliability of electronic components in different humidity environments.

The MSL should be selected with reference to JESD22-A113 and J-STD-020. The minimum MSL requirement for automotive chips is MSL 3. The levels are described below.

MSL 1. The lowest sensitivity level. Components can be stored indefinitely at up to 30℃ and 85 percent relative humidity without any floor life limit.

MSL 2. Components can be stored for one year at up to 30℃ and 60 percent relative humidity without affecting performance.

MSL 2a. Similar to MSL 2, but floor life is reduced to four weeks.

MSL 3. Floor life is further reduced to 168 hours, or one week.

MSL 4. Floor life is 72 hours, or three days.

MSL 5. Floor life is 48 hours, or two days.

MSL 5a. Floor life is 24 hours, or one day.

MSL 6. Floor life is 12 hours. Components at this level must be baked before reflow and must complete reflow within the time stated on the moisture sensitivity label.

Why the MSL matters

The MSL guides how components should be stored and handled from packaging through to final assembly. The lower the MSL, the more resistant the component is to moisture and therefore the longer its floor life. Conversely, the higher the level, the shorter the time a component may be exposed to a humid environment, so stricter control and handling are needed before assembly.

An MSL 4 component, for example, may not be stored for more than 72 hours at up to 30℃ and 60 percent relative humidity. This means that once it is removed from the vacuum packaging, placement and reflow must be completed within 72 hours. If this is not possible, the component must be re-vacuum packed and preferably re-baked before repacking so that the storage time is recalculated. Components that exceed the specified time must be baked again before use.

How moisture affects electronic components

Moisture affects electronic components in several ways. First, it accelerates chemical degradation and reduces performance. Second, it can cause physical damage during soldering. Reflow heating is rapid and builds pressure inside the component. If the absorbed moisture has not been properly removed, that pressure can delaminate the package, break gold wires, damage the die or even crack the component internally. In the most severe cases the expansion of moisture can make the component bulge and burst, a phenomenon known as the popcorn effect.

Moisture protection measures

Preventing moisture damage requires a series of measures: choosing packaging materials wisely, strictly controlling humidity and temperature in the assembly environment, and using sealed packaging and desiccant during transport and storage. In some advanced manufacturing environments, moisture tracking systems with radio frequency tags, local control units and dedicated software are used to monitor and control humidity in real time across packaging, test lines, transport and handling, and assembly operations.

MSL grading provides an important reference for the storage and handling of electronic components, and appropriate moisture protection is the key to ensuring performance and reliability. As the electronics industry continues to raise product quality requirements, understanding and applying MSL grading will become even more important.

About NTEK

NTEK Group was founded in 2009 and is headquartered in Shenzhen. The group provides quality research and technical services covering R&D verification, inspection and testing, failure analysis, simulation and market access for intelligent connected vehicles, electronic communications and new energy.

NTEK has extensive experience in automotive-grade electronic certification and has helped more than 100 companies pass AEC-Q series certification. Driven by the need of vehicle makers to localise automotive-grade components and supported by the domestic semiconductor industry, NTEK provides comprehensive testing and certification services, applying AEC-Q automotive standards to control the safety and quality of automotive components, supporting the growth of domestic automotive-grade components and adding new momentum to the intelligent vehicle safety system.