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

Ron Miller (rmiller@Brocade.COM)
Tue, 25 May 1999 09:37:09 -0700

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Keith

There are may types of ceramic capacitors. Those with the higher values
also have higher temperature dependence up to the amounts you have seen.

Only through using NPO type can you expect the values to be stable with
temperature. Look at the Murata/Erie web sites to get info.

Ronb Miller

"Kowal, Keith" wrote:

> 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
>
> **** To unsubscribe from si-list: send e-mail to majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE si-list, for more help, put HELP. si-list archives are accessible at http://www.qsl.net/wb6tpu/si-list ****

--
Ronald B. Miller  _\\|//_  Signal Integrity Engineer
(408)487-8017    (' 0-0 ') fax(408)487-8017
     ==========0000-(_)0000===========
Brocade Communications Systems, 1901 Guadalupe Parkway, San Jose, CA  95131
rmiller@brocade.com,  rbmiller@sjm.infi.net

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<!doctype html public "-//w3c//dtd html 4.0 transitional//en"> Keith

There are may types of ceramic capacitors.  Those with the higher values
also have higher temperature  dependence up to the amounts you have seen.

Only through using NPO type can you expect the values to be stable with
temperature.  Look at the Murata/Erie web sites to get info.

Ronb Miller

"Kowal, Keith" wrote:

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

**** To unsubscribe from si-list: send e-mail to majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE si-list, for more help, put HELP.  si-list archives are accessible at http://www.qsl.net/wb6tpu/si-list ****

-- 
Ronald B. Miller  _\\|//_  Signal Integrity Engineer
(408)487-8017    (' 0-0 ') fax(408)487-8017                 
     ==========0000-(_)0000=========== 
Brocade Communications Systems, 1901 Guadalupe Parkway, San Jose, CA  95131
rmiller@brocade.com,  rbmiller@sjm.infi.net
  --------------1F323E2B5A44F091983B26F5-- **** To unsubscribe from si-list: send e-mail to majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE si-list, for more help, put HELP. si-list archives are accessible at http://www.qsl.net/wb6tpu/si-list ****