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PCBA Tech

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PCBA Tech

PCBA Tech

Management method of MSL humidity sensor in PCBA processing
2021-09-26
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Author:Aure

Management method of MSL humidity sensor in PCBA processing



Many EMS electronic manufacturing plants often encounter humidity-sensitive electronic components, which must be paid attention to. Because of improper management of humidity-sensitive components, it will directly lead to poor soldering, resulting in defects such as false soldering, continuous tin, and low tin. The management of humidity sensitive components is mainly carried out from two aspects: storage and feeding.


Each kind of humidity sensor has its MSL (Moisture Sensitivity Level), which clearly stipulates the maximum exposure time allowed by the humidity sensor and the feeding interval. Once the agreement is exceeded, strict baking must be carried out before going online. Humidity-sensitive components are generally stored in a moisture-proof cabinet with specific functions. It is recommended to install a specific temperature and humidity alarm on the moisture-proof cabinet to remind the warehouse staff that once the humidity exceeds the standard, an alarm and manual intervention will be carried out. When taking it out, you must check the condition of the humidity label card, and record the time of taking out and the time of returning the remaining material to the box.

There are 8 levels of MSL classification



Management method of MSL humidity sensor in PCBA processing


Level 1-less than or equal to 30°C/85% RH, unlimited floor life

Level 2-Less than or equal to 30°C/60% RH One year floor life

Class 2a-Less than or equal to 30°C/60% RH Four weeks floor life

Level 3-less than or equal to 30°C/60% RH 168 hours floor life

Level 4-Less than or equal to 30°C/60% RH 72 hours floor life

Level 5-Less than or equal to 30°C/60% RH 48 hours floor life

Level 5a-Less than or equal to 30°C/60% RH 24 hours floor life

Level 6-Less than or equal to 30°C/60% RH 12 hours shop life (For level 6, the components must be baked before use and must be reflowed within the time limit specified on the moisture sensitive attention label)


The process of MSL determination is:

(1) Good IC conducts SAT to confirm that there is no delamination.

(2) Bake the IC to completely remove moisture.

(3) Humidify according to MSL level.

(4) Pass IR-Reflow 3 times (simulate IC upload, repair and dismantle, repair and upload).

(5) SAT test whether there is delamination phenomenon and IC test function.

If it can pass the above test, it means that the IC package meets the MSL level.


Generally speaking, the factory will formulate strict forms, requiring operators to perform strict registration before each pick-and-place, inspection and feeding to ensure the effectiveness of materials. The management of humidity sensitive components is an extremely critical operation requirement in the entire PCBA processing process, and strict management must be carried out.


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