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Identification of Electrical Leakage Sites in MLC Capacitors

IP.com Disclosure Number: IPCOM000121603D
Original Publication Date: 1991-Sep-01
Included in the Prior Art Database: 2005-Apr-03
Document File: 2 page(s) / 53K

Publishing Venue

IBM

Related People

McLean, JR: AUTHOR [+2]

Abstract

Disclosed is a technique to identify the precise location of electrical leakage paths in defective Multi Layer Ceramic (MLC) capacitors. This technique involves monitoring the DC leakage between two or more electrodes during polishing to uncover the defective layer. When the defective layer is reached, the measured resistance changes dramatically and the polishing is then stopped.

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Identification of Electrical Leakage Sites in MLC Capacitors

      Disclosed is a technique to identify the precise location
of electrical leakage paths in defective Multi Layer Ceramic (MLC)
capacitors.  This technique involves monitoring the DC leakage
between two or more electrodes during polishing to uncover the
defective layer.  When the defective layer is reached, the measured
resistance changes dramatically and the polishing is then stopped.

      MLC surface mount capacitors are secured to a mechanical
polishing fixture and wires are connected to the electrode end caps,
as shown in Fig. 1.  The other ends of the wires are connected to a
curve tracer to measure low levels of leakage current.

      DC leakage resistance is normally caused by a defect, such as a
crack, between electrodes.  Fig. 2 shows the typical construction of
a MLC capacitor.  The defective capacitor is polished on a wheel
using very fine polishing discs.  During polishing to de-layer the
capacitor, the resistance is monitored on the curve tracer.  When the
site of the defect is reached, the resistance measurement will change
from a low resistance reading to a much higher resistance.  The
polishing is immediately stopped at this point.

      The polished surface of the capacitor is then inspected with an
optical microscope, or SEM, to identify the cause of the electrical
leakage.

      References
(1)  S. W. Freiman and R. C. Pohanka, "Review of Mechanically Related
...