On Sat, 06 Feb 2010 10:15:29 -0800, Mycelium
wrote:

On Sat, 06 Feb 2010 12:07:56 -0500, Hammy wrote:


The rms current rating was probably exceeded for the ambient temp it
overheated and Kabloowee!


Properly operating ceramic capacitors do not experience ANY heavy
current. If they are experiencing current, they are already bad.

Sure they are 10 and 22uF MLCC's (X5R) are used all the time in the
output of SMPS's so they do carry large RMS currents. That cap looks
like a large 1206 or bigger package which means it's probably a 10 or
22uf cap.

You are attributing storage cap nomenclature and specs with ceramic
caps, which have entirely different purposes and operating spec
declarations.

If your SMPS is switching at 500kHz are faster you don't need large
Aluminum's for hold-up in between such small switching periods.

From just one of the numerous application notes out there on MLCC's as
output caps for SMPS's.

"Because the ESR of ceramic capacitors is low, the capacitor
temperature rise due to ripple current dissipation is usually
negligible. Good design practice dictates that we always confirm this
and verify that the output capacitor RMS current and temperature rise
are within the manufacturer's suggested limit. The maximum RMS ripple
current seen by the output capacitor occurs at the maximum input
voltage…."

Sounds to me like they are working while they carry high rms current.