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Excessive solder

Appearance
Solder fillet by far above specification limit.
Attention ! Always compare with current specifications and standards. They often differ from each other. Here DIN EN 61191, Part 1 - 4, and IEC 61191, Part 1 - 4 respectively are taken as reference basis.
The assessment of all solder joints is based on the standards given above.

Excessive solder at CMC

Description:
Borderline case of excessive solder at a CMC after wave soldering. The relatively fat solder joint is just acceptable. The solder may reach over the contact area or up to the top edge of the contact metallization, but it must not reach over the body of the component.

Causes/Remedy:
  • poor layout design
  • pollution of the solder (alloy)
  • poor process parameter (wave soldering)


Source: SEM

Excessive solder at MiniMELF

Description:
Excessive solder at a MiniMELF resistor after wave soldering.The solder reaches beyond the contact metallization and touches the component body.The solder joint has to be reworked in any case. (observe soldering temperature, T ≤ 350°C)

Causes/Remedy:
  • poor layout design
  • pollution of the solder (alloy)
  • poor process parameter (wave soldering)


Source: SEM

Excessive solder at PLCC

Description:
Borderline case of excessive solder at a PLCC. It is clearly visible that the solder has crept up the leads. As long as the solder does not come into contact with the component body, the solder joints are acceptable. It has to made sure, however, that there is a solder fillet at the toe as well as at the heel of the lead.

Causes/Remedy:
  • -/-


Source: SEM
Excessive solder at a PLCC

Excessive solder at SO

Description:
Excessive solder at two gullwing-leads of a SO component. During repair solder in excess quantity was deposited at the leads. According to IEC 61191 - 2 these two solder joints are still acceptable.As the width of the solder joints exceeds that of the leads, it cannot be ruled out that the minimum distance between two neighbouring conductors is not adhered to. Make sure that there are solder fillets at the heels ot the leads.

Causes/Remedy:
  • repair soldering: solder fillet too big
  • inexpert carrying-out of rework


Source: SEM

Excessive solder at SOT23

Description:
Excessive solder at SOT23 components after wave soldering. The photo shows that the solder touches the component body. According to IEC 61191-2 the solder joints are not acceptable and have to be reworked.
Observe precautions for handling ESD!

Causes/Remedy:
  • poor process parameter during wave soldering (soldering angle, temperature)
  • pollution of the solder /alloy
  • poor flux/flux application


Source: SEM

Excessive solder, general

Description:
Fat solder joint, with a wetting angle of >90°. According to EC 61191-1 this is a borderline case which is acceptable, however. It should be made sure nevertheless that the majority of solder joints has a wetting angle of < 90° and is concave to the lead of the component respectively.

Causes/Remedy:
  • poor process parameter during wave soldering (soldering angle, temperature)
  • pollution of the solder /alloy
  • poor flux/flux application


Source: visual, optical inspection - general view
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