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Deficiencies in component alignment

Appearance
The position of the components relative to the landings pads on the substrate deviates from the specifications.
Attention ! Always compare current standards. They are often different from each other. Here DIN EN 61191, Part 1 - 4, and IEC 61191, Part 1 - 4, respectively are taken as reference.
The assessment of all solder joints is based on the standards stated above.

Alignment deficiencies at CMC

Description:
Clearly visible alignment fault of a CMC after wave soldering. The component has separated from the adhesive depot during the soldering process. Rework is necessary because the function is impaired. The component should be replaced. Observe soldering parameter (soldering temperature </= 350°C)

Causes/Remedy:
  • poor adhesive application
  • adhesive insufficiently hardened
  • poor soldering parameter


Source: visual, optical inspection - general view

Alignment deficiencies at MiniMELF

Description:
Borderline case for an end overhang of two MiniMELF. Although the overhang has not impaired the formation of the solder joint, this is to be regarded as a borderline case which is just acceptable. The minimum overlap on the right contact side must not be forgotten, however. It must not be below 2/3 (Class A,B) of the metallization width or the total metallization width respectively.

Causes/Remedy:
  • placing faults: teaching, tolerances, systematic faults
  • floating of components during reflow process
  • vibration during soldering


Source: SEM
Alignment faults of two MiniMELF

Alignment deficiencies at PLCC

Description:
Alignment fault at a PLCC. The leads are exactly between the pads instead of on them. According to the standard the overhang must not exceed 1/2 and 1/4 of the lead width respectively. In this case rework is necessary. It is remarkable that a solder joint has formed despite the excessive overhang.

Causes/Remedy:
  • placing faults: teaching, tolerances, systematic faults


Source: SEM

Alignment deficiencies at QFP

Description:
This photo was taken shortly after placing the components. On the bottom left there is a PLCC which has clearly not been aligned correctly. This can lead to defects during soldering. Here the overhang is clearly nonconforming. Rework can be done before soldering.

Causes/Remedy:
  • placing faults: teaching, tolerances, systematic faults


Source: visual, optical inspection - general view
alignment fault of a QFP

Alignment deficiencies at SO

Description:
Alignment fault at a SO component. The component was twisted during placing, so that electrical connection is not possible.

Causes/Remedy:
  • placing faults: teaching, tolerances, systematic faults
  • floating of components during reflow process
  • vibration during soldering


Source: visual, optical inspection - general view

Alignment deficiencies at SOT23

Description:
Acceptable alignment fault at a SOT23. The component has only slightly shifted. Rework is not necessary.

Causes/Remedy:
  • placing faults: teaching, tolerances, systematic faults
  • floating of components during reflow process
  • vibration during soldering


Source: visual, optical inspection - general view
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