SEM Lab, Inc. performed failure analysis on a diode bridge.  Electrical tests results suggested that one of four internal diodes had short circuited.


The module was chemically decapsulated and the shorted die was isolated for SEM/EDS analysis. This is a BSE SEM image of the shorted die.


The suspected short site was located near a corner of the die.


An elemental map confirms that the suspected short is a silicon melt pipe.


Higher magnification images of the site also confirmed it is the breakdown site.


The size of the breakdown site is related to the melt-thru current [1], which in this case is estimated as ~14.3 amperes.  The location of the melt through suggests that the breakdown was caused by a high voltage transient.

[1] J. T. May, “Limiting Phenomena in Power Transistors and the Interpretation of EOS Damage”, in Microelectronics Failure Analysis Desk Reference, 3rd Edition, ASM International Press, 1993, pp. 321-328.



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