Moisture Sensitivity Level Test (MSL Test) is introduced to verify moisture sensitivity level of ICs, for avoiding shortened lifespan or damage resulting from IC delamination in SMT reflow assembly.
Device under test (DUT) shall be subject to “Initial Electric Characteristics Test”, “External Look Inspection”, and “Ultrasonic Inspection” to validate the initial status of the DUT (e.g. existence of delamination and cracks) before “baking out” at 125 ℃ for 24 hours followed by a “Dehumidification” and “Reflow” Test.
Moisture sensitivity level can vary greatly depending on the moisture conditions of the device, ranging from Level 1 to Level 6.
The testing conditions are defined into two categories: Sn-Pb Eutectic Assembly and Pb-Free Assembly, in accordance with the using reflow profile.
|Profile Feature||Sn-Pb Eutectic Assembly||Pb-Free Assembly|
|Preheat & Soak|
Time(Tsmin to Tsmax) (Ts)
|Average ramp-up rate|
(Tsmax to Tp)
|3 ℃/second max||3℃ /second max.|
Time at liquidous(tL)
|Peak Package body temperature(Tp)*||See classification temp in Table 4.1||See classification temp in Table 4.2|
|Time(Tp)** within 5 ℃ of the specified|
classification temperature (Tc)
|20** seconds||30** seconds|
|Average ramp-down rate(Tp to Tsmax)||6 ℃ /second max.||6℃ /second max.|
|Time 25 ℃ to peak temperature||6 minutes max.||8 minutes max.|
Failures mode includes the apparent damages, electrical failures, internal cracks and the position and ratio of delamination. In case the selected moisture sensitivity level fails the test, less strict conditions can be used for re-test. The final level identification shall be indicated on the outer package.
No delamination before MSL test
Delamination on die paddle/lead frame after MSL test
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