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Tinning

Bad tinning

Description:
Bad tinning of some parts of conductors. The copper areas partly visible (reddish) reveal a bad wettability of the copper. This can be caused by contaminated or corroded copper areas, in fery few cases by the hot tinning process itself.

Causes/Remedy:
  • contamination of copper areas
  • corrosion of copper areas
  • deficiencies in the tinning process (temperature, alloy)

Source: visual, optical inspection - general view
Bad tinning of conductors on a pcb

Inhomogenous tinning

Description:
Inhomogenous tinning. Excess solder in certain areas is characteristic of this. The distribution and thus the thickness of the layer is inhomogenous, (frequent phenomenon with hot air tinning). This defect is acceptable, as long as all areas are wetted with solder.

Causes/Remedy:
  • deficiencies in the tinning process
  • impaired local wettability of copper areas, in most of the cases due to contamination

Source: visual, optical inspection - general view
inhomogenous tinning

Disturbed tinning

Description:
Disturbed tinning on pads (bluish areas). Rough surface after tinning hinting to contamination of solder alloy and partially unwettable areas on pads.

Causes/Remedy:
  • deficiencies in the tinning process
  • impaired local wettability of copper areas, in most of the cases due to contamination
  • corrosions

Source: visual, optical inspection - general view
disturbed tinning on solder pads of a pcb

Strongly impaired wetting

Description:
Strongly impaired wetting of tinning at parts of conductors. The area shining reddish marks the copper areas which have not been wetted. Rework necessary.

Causes/Remedy:
  • deficiencies in the tinning process
  • impaired local wettability of copper areas, in most of the cases due to contamination
  • Corrosions

Source: visual, optical inspection - general view
Strongly impaired wetting of tinning at parts of conductors on a pcb

Whisker

Description:
Whisker in plated through-hole (thin single crystal, grown in the wall, needle-shaped). Unsuited combinations of different materials lead to material stress which can cause the growing of single crystals on the surface.

Causes/Remedy:
  • Addition of elements to alloy (lead, bismuth)
  • integrate intermetallic zone (Ni interlayer)

Source: visual, optical inspection - general view
Whisker in plated through-hole

Fehlgeschlagene Verzinnung

Description:
Failed tinning on pads of circuit. Due to very bad wetting of the pads the solder contracted and did not form a flat wetted surface. Not acceptable.

Causes/Remedy:
  • hardly wettable pads
  • contamination
  • contaminated solder alloy for tinning

Source: visual, optical inspection - general view
failed tinning on pads of a pcb

Inhomogenous layer thickness

Description:
Inhomogenous layer thickness of tinning at eyelets. Bad wetting of copper areas or deficiencies in the hot tinning process can cause this defect.

Causes/Remedy:
  • tinning deficiencies
  • impaired local wettability of copper areas, in most of the cases due to contamination

Source: visual, optical inspection - general view
Inhomogenous layer thickness of tinning at eyelets

Tinning deficiencies

Description:
Tinning deficiencies at pads due to corrosion on pads (dark areas). Not acceptable.

Causes/Remedy:
  • tinning deficiencies
  • impaired local wettability of copper areas, in most of the cases due to contamination
  • corrosion of pads

Source: visual, optical inspection - general view
Tinning deficiencies at solder pads of a pcb
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