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Poor solder fillet in through-hole

Defective solder fillet in plated holes with component lead
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.

Description:
Poor solder fillet. In accordance with IEC 61191-3, still acceptable, since the solder fillet fills more than 75% of the through-hole.

Causes/Remedy:
  • poor wettability of component
  • poor wettability of through-hole
  • unsuitable soldering parameter
  • pollution of materials to be joined

Source: Microsection
poor solder fillet in through-hole

Description:
The solder joint is still acceptable despite disturbed wetting at the contact pin on the left.

Causes/Remedy:
  • poor wettability of component
  • poor wettability of through-hole
  • unsuitable soldering parameter
  • pollution of materials to be joined

Source: Microsection
disturbed wetting in a through-hole

Description:
Example of a solder joint with wetting problems at the component lead (left).No rework necessary though. The solder joint on the right is ideal.

Causes/Remedy:
  • poor wettability of component
  • poor wettability of through-hole
  • unsuitable soldering parameter
  • pollution of materials to be joined

Source: visual, optical inspection - general view
solder joint with wetting problem

Description:
Problem similar to the one in the preceding example. No rework necessary.

Causes/Remedy:
  • poor wettability of component
  • poor wettability of through-hole
  • unsuitable soldering parameter
  • pollution of materials to be joined

Source: visual, optical inspection - general view
wetting problem at a solder joint

Description:
Example of ideal wetting of the upper and lower contact areas (long solder outrun, small wetting angle)

Causes/Remedy:
- / -

Source: Microsection
ideal wetting of a solder joint

Description:
The vertical solder fillet is distinctly below 75%. Therefore rework is necessary.

Causes/Remedy:
  • poor wettability of component
  • poor wettability of through-hole
  • unsuitable soldering parameter
  • pollution of materials to be joined

Source: Microsection
poor wetting of a through-hole

Description:
Hole in the solder joint. The periphery of the through-hole was not completely wetted. In accordance with IEC 61191-3 this solder joint is still acceptable. Rework is nevertheless recommended.

Causes/Remedy:
  • poor wettability of component
  • poor wettability of through-hole
  • unsuitable soldering parameter
  • pollution of materials to be joined

Source: visual, optical inspection - general view
hole in a solder joint

Description:
Unacceptable solder joint. The peripheral wetting is less than 75 % of the wettable area. Rework necessary.

Causes/Remedy:
  • poor wettability of component
  • poor wettability of through-hole
  • unsuitable soldering parameter
  • pollution of materials to be joined

Source: visual, optical inspection - general view
unacceptable solder joint with less then 75% of wetting

Description:
Unacceptable solder joint, since the solder fillet fills less than 75 %. Moreover there are cracks in the solder along the lead. Rework necesssary.

Causes/Remedy:
  • poor wettability of component
  • poor wettability of through-hole
  • unsuitable soldering parameter
  • pollution of materials to be joined

Source: Microsection
through-hole with less than 75% solder

Description:
Unacceptable solder joints, because wetting covers less than 270° of the periphery on the soldered side. Rework necessary.

Causes/Remedy:
  • poor wettability of component
  • poor wettability of through-hole
  • unsuitable soldering parameter
  • pollution of materials to be joined

Source: visual, optical inspection - general view
unacceptable solder joint
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