[time-nuts] GC-1000 Clock Cap Choice?

[shalimr9 at gmail.com]

Also they are almost impossible to solder by hand without setting high internal stress which sometimes results in cracks, not necessarily immediately. Even on professional wave solder equipment, high delayed failure rates are not uncommon, which sometimes results in many units having to be recalled. Don't ask me how I know, I was lucky this was not my design, but it could have been.

Yet, I still use them, under the assurance that our manufacturing folks have resolved the problem, which for now seems true.

Didier

Sent from my Verizon Wireless BlackBerry

-----Original Message-----
From: Chuck Harris <cfharris at erols.com>
Sender: time-nuts-bounces at febo.com
Date: Sun, 16 Jan 2011 17:43:18 
To: Discussion of precise time and frequency measurement<time-nuts at febo.com>
Reply-To: Discussion of precise time and frequency measurement
	<time-nuts at febo.com>
Subject: Re: [time-nuts] GC-1000 Clock Cap Choice?

I have found that such high dielectric constant capacitors have other
problems in some circuits.  While the capacitance value is dropping,
as much as 50% when you apply voltage, their physical volume is
changing.  They behave as piezoelectric transducers.

I have used them inappropriately, and found them singing loudly.  If
that were to happen in a switching regulator, I would think the ultrasonic
vibrations could do damage to the capacitor, the PCB, or the solder joints.

-Chuck Harris

Poul-Henning Kamp wrote:
> In message<4D336A19.40709 at freenet.de>, "Dr. Frank Stellmach" writes:
>
>> High cap value Ceramics are available since years, [...]
>
> Can you clarify one thing for me: When I studied datasheets for these
> it looked like they drop 50% of their capacitance at a DC voltage
> of 10-20V.
>
> Doesn't that make them a so-so bargain for power supply bulk capacitance ?
>

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