MSL in PCBA processing

MSL in PCBA processing

PCBA processing is to connect various electronic components on PCB board through surface mount (SMT), plug-in (DIP) and other electronic assemblies. PCBA process flow mainly includes SMT, AOI, DIP, FCT testing and other processes. Due to the size difference of electronic components, there will be different processes and requirements in assembly and insertion. The assembly density of PCBA is relatively high, and the small size and light weight of electronic products also have certain changes and requirements in mounting. The reliability, seismic resistance and excellent weldability of the products have high requirements for the hardware and software facilities of PCBA processing.

Many EMS electronic manufacturing plants often encounter humidity sensitive electronic components, which must be highly valued. Due to improper management of humidity sensor, it will directly lead to poor welding, resulting in a variety of defects such as false soldering, tin bonding, and less tin. The management of humidity sensor is mainly carried out from two aspects: storage and feeding.

Each humidity sensor has its own MSL (Moisture Sensitivity Level), which clearly specifies the maximum exposure time allowed for the humidity sensor and the use and feeding interval. Once the agreement is exceeded, strict baking must be carried out before going online. Humidity sensors are generally stored in moisture-proof cabinets with specific functions. It is recommended to install a specific temperature and humidity alarm on the moisture-proof cabinet to remind the warehouse personnel that once the humidity exceeds the standard, they will give an alarm and intervene manually. When taking out, check the condition of the humidity label card, and record the taking out time and the return time of the surplus materials.

There are 8 levels of MSL classification

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

Level 2 - less than or equal to 30 ° C/60% RH one year workshop life

Grade 2a - less than or equal to 30 ° C/60% RH four week shop life

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

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

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

Grade 5a - less than or equal to 30 ° C/60% RH 24 hour workshop life

Level 6 - less than or equal to 30 ° C/60% RH 12 hours workshop life (for Level 6, components must be baked before use, and must return within the time limit specified on the humidity sensitive notice label)

The MSL determination process is:

(1) The IC of good products was tested by SAT, and it was confirmed that there was no delamination.

(2) Bake the IC to completely remove moisture.

(3) Humidify according to MSL grade.

(4) Pass IR Reflow 3 times (simulate IC loading, repair removal, repair loading).

(5) SAT inspection for delamination and IC test function.

If the above tests can be passed, it means that the IC package meets the MSL level.

Generally speaking, the factory will formulate strict forms and require the operator to strictly register before each picking, placing, inspection and feeding to ensure the effectiveness of materials. The management of humidity sensor is an extremely critical operation requirement in the whole PCBA processing process, and must be strictly managed.