[R-390] Orange Drop Caps vs Film Polyester Axial

[Dan Merz]

Hi, thanks for the detail. About what year was this kind of testing done?
Dan

Sent from my iPad

On Apr 28, 2013, at 6:30 AM, "Charles P. Steinmetz" <charles_steinmetz at lavabit.com> wrote:

> Dave wrote:
> 
>> Can you put some meat on these bones, please?  How is "unacceptable self-healing event" defined?  What were the test conditions (e.g. test setup, capacitor value, etc.)?
> 
> The test protocol used a slowly ramping voltage on the cap, up to its rated voltage, from a source with several hundred ohms impedance.  Every self-healing event reset the voltage to zero.  Every several hours there was a simulated power cycle (drain to zero, charge to rated voltage in 1/12 second, drain to zero and start ramp).  The voltage vs. time was recorded, as well as the charge dumped to ground during each self-healing event.  "Unacceptable" self-healing was defined as: (1) one or more clearing charge dumps in excess of a trigger value; or (2) more than (n) self-healing events under the trigger value -- each measured over the course of a month.  I do not recall the precise charge dump trigger value or the value of "n" -- I think "n" was 3, but many metallized film caps failed with "n" much higher than that -- sometimes 5-20 per day.  A typical pattern was a series of self-healing events at lower and lower voltages, sometimes with a "reset" to a higher voltage followed by another series at lower and lower voltages.  The "reset" event was usually a "charge dump in excess of trigger value" event.
> 
> I tested PE and PP metallized-film and film-and-foil caps, as well as Class 2 disk ceramics.  The caps were all new stock from quality manufacturers, acquired through the primary supply chain.  Values ranged from 0.005 to 0.22 uF.  (I also tested some large film caps -- 5 to 100 uF -- and some more esoteric dielectrics -- but that is not pertinent to BA bypass caps.)
> 
> This was an extension of a project to characterize capacitors in a production environment where we needed to get failure rates over the equipment lifetime down very, very close to zero.  We also had extremely limited space, so there was a lot of pressure to use metallized film caps.  In the production test, a single self-healing event over the course of a month disqualified a capacitor.  No metallized film cap ever passed that test.
> 
> Best regards,
> 
> Charles
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