Bending stresses can cause fracture of stiff components such as chip resistors.
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Activated solder flux can corrode open copper plated-through-hole vias causing an open circuit condition.
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Multilayer chip capacitors (MLCCs) can fail due to a manufacturing defect known as Knit Line Fracture, which is a lamination defect causing separation on internal layers.
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Residual molding compound indicates the bond wire was hot enough to thermally decompose the epoxy molding compound.
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Chip resistors can corrode and increase in resistance or go open circuit due to sulfur in atmospheric pollution.
Here is another example …
The conformal coating was removed to exposed the top of the resistor.
SEM/EDS analysis of an apparent corrosion bloom suggest that it is silver sulfide.
This is a higher magnification image showing the structure of the bloom.
Solder mask defined pads are considered undesirable since they require exacting mask alignment. In this case misalignment likely contributed to weakness in the ball attachment.
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Pad lift can be caused by excessive heat during reflow soldering or poor copper adhesion to the PWB laminate.
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This is an LED microsection where the open circuit failure was caused by the die and lens material separating from the bottom of the cup and rupturing the die attachment.
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This is a flex crack in MLCC caused by breakout of PCBA from panel. The PCBA layout during the design phase is critical in preventing this type of failure.
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