Re: [SI-LIST] : Capacitance in a Ceramic changes

Michael Nagel (mina@force.de)
Tue, 25 May 1999 14:06:29 +0200

Keith,

did you have a look into the spec. of the capacitor regarding temperature
profile and so on? I assume the capacitor has a X7R dielectric. If you
have trouble with capacitance changes NPO dielectric might be worth a look
if you don't mind size.

Michael

> From kowal@cabletron.com Tue May 25 13:59:27 1999
> From: "Kowal, Keith" <kowal@cabletron.com>
> To: "'si-list@silab.eng.sun.com'" <si-list@silab.eng.sun.com>
> Cc: "Kowal, Keith" <kowal@cabletron.com>
> Subject: [SI-LIST] : Capacitance in a Ceramic changes ?i usedf
> Date: Tue, 25 May 1999 07:40:41 -0400
> MIME-Version: 1.0
>
> Recently I experienced a SMT chip cap (0.047uf - 1206package) change from
> a nominal capacitance that was within spec to a much larger capacitance
> once 3 or more seconds of soldering iron heat was applied to the component.
> Once it cooled down, I measured it again and to my dismay it measured
> 0.062uf
> and 1 day later it still measured 0.062uf... This is telling me that heat
> changed
> the value of the capacitance. My question to the group is this a bad
> component
> or is this typical - I tried other similar caps and some held to their
> spec'd capacitance.
> I did a statistical sample and not all 100 caps did this, although 92 out of
> the 100
> went out of spec. (grm42-6z5u473m050 /// this was the part number that
> gave
> me the trouble).
>
> any ideas?
>
>
> Keith
>
>
>
>
> * Outside 978-684-1574
> * Internet: Kowal@ctron.com
> * Fax: 978-684-1610
>
>
>
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