Anshul Shrivastavaa, Stefan Bangertha, Michael H. Azariana, Carlos Morilloa, Michael Pechta, Mark Levinb, Larry Steinhardtb and Andrew Callinic
a Center for Advanced Life Cycle Engineering, University of Maryland, College Park, MD 20742, USA
b Teradyne, Agoura Road, Agoura Hills, CA 30701, USA
c Teradyne, 500 River Park, North Reading, MA, USA
Detecting leakage from liquid aluminum electrolytic capacitors is not easy. Typically there is very little evidence of leakage because the electrolyte is volatile and leaves behind only trace residues. Liquid aluminum electrolytic capacitors are known to cause catastrophic failures where there is complete loss of functionality due to a short or open circuit. In the study presented in this paper, printed circuit board assemblies from a test and measurement system used in a clean room environment failed. Two units failed, causing burning in a particular area on the printed circuit board assembly. The failure area included several surface mount liquid aluminum electrolytic capacitors, and several others were mounted very close to the burnt region. A study was initiated to evaluate the cause of failure. Careful optical inspection revealed some residues on the outer side of the rubber seals of two of the electrolytic capacitors. Through using Fourier transform infrared analysis and a process of experimentation and analysis, it was determined that the residues were produced by liquid electrolyte that leaked out of the capacitor at some point in the field. The leaked electrolyte that came out of the capacitor was believed to be the cause of failure that led to the burning of the printed circuit board assembly.
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