Visual Inspection of Soldered Leads
A visual inspection typically at a low power magnification of up to 10X is performed after the solder has been applied. There are several criterions to look for. This attempts to clarify and interpret the visual requirements.
Bridging Solder - Leads or Balls are Shorting
- Excessive solder
- Bent or skewed leads therefore, reducing the space between leads
- Excessive solder paste
- Pad to lead ratio is incorrect
Leads Lifting - Leads not Making Contact with Solder Pad
- Bent leads or uneven leads
- Warped package possibly due to moisture absorption
- Lead pitch out of tolerance
Solder Wetting/de-wetting - Voids or Lack of Sufficient Solder Flow on Leads
- Insufficient solders on leads
- Thin oxide buildup on leads
- Not enough solder paste applied
- Solder temperature too low
- Insufficient plating on leads
- Leads absorbed moisture
- Solder paste degradation
Solder Wicking - Solder has not Flowed Evenly on Lead
- Insufficient amount of solder paste applied
- Solder temperature insufficient to footprint
Solder on Board Around or Near the Leads
- Rapid rise in solder paste temperature
- Degradation of solder paste
Flux Residue Present - Flux Present on Board Around or Near the Leads
- Excessive heat applied to flux
- Insufficient cleaning or removal of flux
- Flux shelf life exceeded therefore old flux was used