Moisture sensitivity level (MSL) relates to the packaging and handling precautions for some semiconductors. The MSL is an
electronic
Electronic may refer to:
*Electronics, the science of how to control electric energy in semiconductor
* ''Electronics'' (magazine), a defunct American trade journal
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standard for the time period in which a moisture sensitive device can be exposed to ambient room conditions (30 °C/85%RH at Level 1; 30 °C/60%RH at all other levels).
Increasingly,
semiconductors have been manufactured in smaller sizes. Components such as thin fine-pitch devices and
ball grid array
A ball grid array (BGA) is a type of surface-mount packaging (a chip carrier) used for integrated circuits. BGA packages are used to permanently mount devices such as microprocessors. A BGA can provide more interconnection pins than can be p ...
s could be damaged during
SMT reflow when moisture trapped inside the component expands.
The expansion of trapped moisture can result in internal separation (
delamination
Delamination is a mode of failure where a material fractures into layers. A variety of materials including laminate composites and concrete can fail by delamination. Processing can create layers in materials such as steel formed by rolling a ...
) of the plastic from the die or lead-frame, wire bond damage, die damage, and internal cracks. Most of this damage is not visible on the component surface. In extreme cases, cracks will extend to the component surface. In the most severe cases, the component will bulge and pop. This is known as the "popcorn" effect. This occurs when part temperature rises rapidly to a high maximum during the soldering (assembly) process. This does not occur when part temperature rises slowly and to a low maximum during a baking (preheating) process.
Moisture sensitive devices are packaged in a moisture barrier
antistatic bag
An antistatic bag is a bag used for storing electronic components, which are prone to damage caused by electrostatic discharge (ESD).
These bags are usually plastic polyethylene terephthalate (PET) and have a distinctive color (silvery for metal ...
with a
desiccant and a moisture indicator card which is sealed.
Moisture sensitivity levels are specified in
technical standard
A technical standard is an established norm or requirement for a repeatable technical task which is applied to a common and repeated use of rules, conditions, guidelines or characteristics for products or related processes and production methods, ...
IPC/
JEDEC
The JEDEC Solid State Technology Association is an independent semiconductor engineering trade organization and standardization body headquartered in Arlington County, Virginia, United States.
JEDEC has over 300 members, including some of the w ...
''Moisture/reflow Sensitivity Classification for Nonhermetic Surface-Mount Devices''.
The times indicate how long components can be outside of dry storage before they have to be baked to remove any absorbed moisture.
* MSL 6 – Mandatory bake before use
* MSL 5A – 24 hours
* MSL 5 – 48 hours
* MSL 4 – 72 hours
* MSL 3 – 168 hours
* MSL 2A – 4 weeks
* MSL 2 – 1 year
* MSL 1 – Unlimited floor life
Practical
MSL-specified parts must be baked before assembly if their exposure has exceeded the rating. Once assembled, moisture sensitivity is generally no longer a factor.
References
{{reflist
External links
* https://electronics.stackexchange.com/questions/23044/ics-with-humidity-or-moisture-sensitivity-bake-recommendations
Integrated circuits
Semiconductors