Moisture Sensitivity Level (MSL) & Popcorn Effect

MSL (Moisture Sensitivity Level) is an electronic standard which is established by JEDEC for the time period in which a moisture sensitive device can be exposed to ambient room temperature.

That is, short for Moisture Sensitivity Level, MSL is a JEDEC (Joint Electron Device Engineering Council) standard established for the purpose of preventing device failure due to volumetric expansion of atmospheric moisture introduced into the resin package of semiconductor devices during reflow.

Note that a semiconductor components with resin-sealed package could be damaged during SMD reflow when moisture was trapped inside the component expands.

And, according to the aforementioned JEDEC standard, there are eight levels of moisture sensitivity as shown in the below table.

Simply put, Moisture Sensitivity Level (MSL) defines how sensitive components are to moisture. Lower MSL levels allow manufacturers a wider processing window; reducing inventory & processing costs.

Popcorn Effect: The popcorn effect is when an IC pops because the moisture inside the package expands in the reflow process. As a result of this expansion the substrate, the die, or the wire bonds could be damaged. 

Note that when the antistatic bag is opened and the IC is exposed to ambient conditions, the moisture in the air is trapped inside the device. This means that during the reflow process, this moisture expands and can damage the device. The damage is often invisible and requires X-ray equipment to conduct a proper analysis.

To avoid the Popcorn Effect, you can simply bake the device and seal it in a hermetically sealed antistatic bag. If the device was exposed to moisture, re-bake it and assemble the device within the allowed exposure time (the baking is driving all the moisture out of the device).

Next figure shows an Xbox 360 graphical processing unit that was desoldered from an Xbox 360 motherboard (https://commons.wikimedia.org/wiki/File:PopcornBGA.jpg).

This photograph shows the risks of desoldering ball-grid array components without proper procedures. 

Here you can see that moisture in the circuit board turned to steam when it was subjected to intense heat. This produces the so-called Popcorn Effect.

You can prevent this by using a fast-acting solvent such as methyl ethyl ketone as well as preheating the circuit board using an oven.

Well, we will be providing more updates in due course ⪫

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