What are the possible reasons for the falling off of SMT red glue process?

What are the possible reasons for the falling off of SMT red glue process?

1. If the surface mount components and the red oil (solder resist) of the PCB board fall off together, it indicates that there is a problem with the material of the PCB board itself (the adhesion of the red oil is not enough);

2. Check whether there are scratches at the position where the PCB board surface mount components fall off. Scratches at the position where the PCB board surface mount components fall off will also cause insufficient adhesion of the green oil;

3. Check whether the PCB board surface mount components fall off regularly. If several fixed surface mount components fall off, you need to consider whether the holes of the steel mesh are blocked, the amount of red glue is too small, or the curing time of the red glue in the reflow soldering is not enough. If the falling off of the surface mount components is irregular, you need to consider whether the adhesion of the red glue is not enough, the red glue is expired, or the recovery time of the red glue is not enough;

4. The surface mount components fall off, but the red glue is still stuck on it. The reason is that there is a problem with the incoming materials of the surface mount components (there is a problem with the surface treatment of the surface mount components, such as the presence of release agent, which affects the adhesion of the red glue);

5. The surface mount components fall off during transportation, such as (glass diodes). This requires that the PCB board be placed properly, not stacked, and the circuit board be packaged with bubble bags or other cushioning packaging materials to avoid the components from colliding with each other and falling off;

6. The PCB board is stored for too long after surface mounting: If the time is exceeded, the red glue will gradually lose its stickiness and produce unstable adhesion, resulting in falling off of components.

7. When only large components of surface mount components fall off, you can consider whether the temperature is not enough? The red glue curing agents of different companies may be different, resulting in different curing temperatures. In addition, for some ICs with higher pins, pay attention to whether the amount of red glue is sufficient and whether the contact surface between the red glue and the IC is sufficient to avoid the falling off of components.