Visual inspecting before reflow soldering, Shenzhen PCB Assembly
Visual inspecting before reflow soldering

1. The workflow
When the assembled PCB arrives to the inspection desk before reflow oven, it should be noted that the hand can only touch the edge of the PCB, avoid touching the solder paste and the placed components. Large components that floated up exceed the thickness of the solder paste should be pressed by the iron bars. The iron bars cannot be directly put above the module, BGA.
 
2. Visual inspection
Visual inspect solder paste printing for defects such as misalignment, missing printing, extra solder, and insufficient solder. Check if the orientation of the polar components is correct, if the material is damaged, and if the component leads are deformed, the silkscreen is not clear, the position of the placing is shifting, and the shielding frame does not float high from the PCB.
 
3. Manual repairing operation
For IC components, check the levelness of the IC lead before use. If the IC leads have a high floating, it cannot be used. It must be repaired by the technician before placing it onto PCB. Each time the material is added, it should be checked according to the BOM and Gerber files, after IPQC confirming it can put it into oven.
 
4. Exception situation handling
When a defect is found, it must be immediately reported to the supervisor. If is a poor paste printing, notify the printer to improve. If it is poor placement, inform the technician to improve. The defect is reported to the inspector of next step. All the NG products must be isolated. After repair, it should confirmed by the IPQC before continuing production.
 
I. Main NG items of this step: Shielding frame floating high, components misalignment, insufficient tin, wrong direction, components missing, IC lead flip up etc.
II. NG product corrective action plan: If found same defect more than 3 in production line, immediately notify the engineer to improve.
III. Work protection: before the operation, the electrostatic ring should be worn tightly on left wrist, fingerstall should be worn well on the thumb, forefinger and middle finger of both hands.