A client provided a failed metal thin film resistor (Nichrome) to SEM Lab for failure analysis. 

 

This is a failed resistor, IRC P/N W1206R033323B, 332K, 1%, 1/4W.
This is a failed resistor, IRC P/N W1206R033323B, 332K, 1%, 1/4W.
This is an optical image of the microsection at a location just outside of the NiCr thin film resistor pattern.  There is evidence of corrosion at the edge of the resistor pattern (arrows).
This is an optical image of the microsection at a location just outside of the NiCr thin film resistor pattern.  There is evidence of corrosion at the edge of the resistor pattern (arrows).
This is a higher magnification image of the corrosion damage to the resistor pattern.
This is a higher magnification image of the corrosion damage to the resistor pattern.
This region appears to be corroded (i.e. NiCr pattern missing).
This region appears to be corroded (i.e. NiCr pattern missing).
5.    The cover glass and interfacial structure appear to contain micro-pores that might explain moisture ingression from the edge of the resistor.
5.    The cover glass and interfacial structure appear to contain micro-pores that might explain moisture ingression from the edge of the resistor.
This is another image of a region that appears to have been corroded (i.e. missing NiCr).
This is another image of a region that appears to have been corroded (i.e. missing NiCr).

 

The analysis results suggest that the resistor failed due to corrosion of the edge of the NiCr resistor pattern.  The removal of material by the corrosion process created an open (likely multiple opens) in the resistor pattern.

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