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In many PCBA processing processes, EMS electronics manufacturing factories 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
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
Class 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.
What is the difference between ICT and FCT in PCBA test?
PCBA testing is a key step to ensure the quality of shipments. Generally, customers need to provide a test plan, including test points, procedures, and test steps. PCBA electronics manufacturers perform corresponding ICT and FCT tests according to the design documents. ICT (In-circuit Test, circuit test) is mainly for the component level, by contacting the pins of each component on the PCBA board, and measuring whether its value is consistent with the nominal value, it is a kind of detection resistance and capacitance. The value and polarity of components such as inductors and inductors are very important means.
FCT test
With the rapid development of process capabilities in the electronics industry, ICT testing has become less and less, because the quality of many components can reach below 50PPM, which fully meets the process yield of electronic products. At this time, FCT (Function Test) is particularly important. The PCBA manufacturer will issue an FCT test rack according to the design file, place the PCBA board on the test rack, capture the test points on the PCBA board to write the program through the burner, and then simulate the input and output actions of the product to achieve the test purpose. On some occasions, PC software is needed to cooperate. FCT test is a kind of functional test close to the product level, which can effectively cover the performance range of the product and is a very effective method.
