Reasons of inadequate solder paste in PCB assembly process

1. When the printing machine is working, the solder paste is not added in time.

2. Solder paste quality is bad, which is mixed with hard objects such as foreign body etc.

3. Solder paste that has not been used up before, already expired, is re-used.

4. Quality of PCB is bad, there are inconspicuous coverings on the pad, such as solder resist, or silkscreen oil, was printed on the pad.

5. The fixed clamping of the circuit board in the printing machine is loose, PCB is moving during solder paste printing.

6. Solder paste stencil thickness is uneven.

7. There is foreign body on solder paste stencil or circuit board (such as PCB packaging material, stencil wiping paper, foreign matter floating in the ambient air, etc.).

8. The solder paste scraper is damaged or the stencil is damaged.

9. The equipment parameters such as pressure, angle, speed and demoulding speed of the solder paste scraper are not suitable.

10. After the solder paste is printed, it is accidentally knocked out due to human factors.