Examples of Defects of LED Products/Chip Capacitor

Lighting failure [Failure of LED product]

• Thermal expansion of mold resin due to continuous lighting may cause sequential non-lighting.

  Possible causes are:

  • Connection failure at the 1^st bonding portion;
  • Break at the 1^st bonding neck portion; (Grain coarsening due to the thermal effect during bonding)
  • Break at the 2^nd bonding portion (Corrosion, joint failure, effects during resin molding, etc.)

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SIM:Scanning Ion Microscope

Internal electrode crack [Failure of chip capacitor]

• Crack may be generated in the internal electrode area of the chip capacitor, causing a failure.

  Due to the warp of the mounting substrate, crack may be generated starting from the solder joint on the bottom of the chip capacitor. If a crack is generated crossing electrodes, failures such as short-circuit and insulation degradation will become apparent.

  The base material of the chip capacitor is ceramic such as barium titanate which is a dielectric, and many internal electrodes are laminated inside the chip capacitor. Therefore, due to a shock such as bending, crack is easily generated.

  Cracking of the chip capacitor may be generated at the time of the dividing of the mounted substrate and similar occasions.

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Short circuit between internal electrodes [Failure of chip capacitor]

Short-circuited chip capacitor was found at the market.

As the examination result of the cross section of the chip capacitor, it was found that the portion between the internal electrodes was short-circuited. As stress over the withstand voltage is not applied to this chip capacitor, and the failure is dependent on the lot of the chip capacitor. Therefore, it is presumed that the short-circuit was caused by a poor insulation between the internal electrodes.

• The portion between the internal electrodes is short-circuited, causing a crack on the dielectric.

  

• On another product in the same lot, a slight trace of short-circuit is recognized on the internal electrode.