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Insufficient solder at MiniMELF

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Description:
Borderline case of a reflow solder joint at a MiniMELF. This solder joint meets all minimum requirements of IEC 61191 - 2 in all classes (Class A-C). Wetting is irreproachable and the height of the solder fillet is 1/4 of the component diameter. No rework necessary.

Causes/Remedy:
  • solder paste quantity relatively low


Source: SEM
Insufficient solder at a MiniMELF - borderline case

Description:
Same context as described above. Illustrated in colour for better understanding.

Causes/Remedy:
  • solder paste quantity relatively low


Source: visual, optical inspection - general view
Insufficient solder at a MiniMELF

Description:
Same context as described in the main file. Apart from that the photo shows a case of non-soldering (left) and a borderline case of insufficient solder. It can be seen how complex it is to analyse defects in the inspection of soldered assemblies.The difference between the two defects is difficult to define.

Causes/Remedy:
  • wave soldering: shadow effect, unfavourable positioning of component
  • reflow soldering: poor solder paste application
  • wetting problems at component terminal end face


Source: SEM
Insufficient solder at a MiniMELF

Description:
Borderline case of insufficient solder at a MiniMELF (center). The difference between the "normal" solder fillets (right) and the borderline case is clearly visible. In this case rework is not necessary. Indications concerning the quality and reliability of the solder joint cannot be deducted, however. But lean solder joints, in some cases even very lean solder joints have often proved to meet reliability requirements.

Causes/Remedy:
  • reflow soldering: inhomogenous solder paste application
  • wave soldering: wetting problems, shadow effect, flux problems


Source: visual, optical inspection - general view
Insufficient solder at MiniMELF
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