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The time when the moisture-sensitive device is not in a sealed state or stored in a dry state needs to be recorded on the "Moisture Sensitive Element Unsealing Time Control Label".
After the device is unpacked, the allowable unpacking exposure time is controlled according to the moisture sensitivity level control and the specification requirements.
Remarks: Each storage or unit can use the moisture-sensitive device opening time control label in its own format, but the content of the above label must be covered.
For the SMD that has been damp, it must be baked before the SMT processing. For the baking under the condition of 110 ℃, some problems should be paid attention to: It is necessary to confirm whether the inner packaging (tray type, tube type, roll type) has the ability of "high temperature resistance" (some suppliers will mark "HEATPROOF" on the inner packaging), otherwise it can only be baked at a low temperature of 45°C. In addition, under the aforementioned two baking conditions, the oven door should not be opened and closed frequently during the baking period to maintain a dry environment in the oven.
When SMD is reflow soldering, must strictly control the rate of temperature change: its heating rate is less than 2.5°C/sec; also need strictly control the maximum temperature and high temperature duration (manufacturer requirements), each device must meet its own requirements.
When hot-air rework of the damp SMD, if the device needs to be reused, the PCBA board needs to be baked before disassembling the device. The baking conditions are based on the PCBA baking requirements described; if the device does not need to be reused, baking board is not required before the repair. However, if the entire board needs to be heated to above 110°C during the rework process, or if there are other moisture-sensitive devices within 5mm of the rework area, the PCBA components must be pre-baked and dehumidified according to the moisture sensitivity level and storage conditions.
