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Subject: Re: Ceramic Capacitors
Date: Tue, 01 Oct 2002 18:34:04 -0500
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Organization: ExecPC Internet - Milwaukee, WI
C0Gs (NP0s) are mostly low in BaTiO2 which is ferroelectric
and high in TiO2 which is not. That means that they are "very low" in
piezoelectric effects. All NP0s are not created equal however. Some
applications call for size/performance compromises that call for more
high-K ferroelectric additives to reduce the size. I would assume
these would be a bit more piezoelectric, but still lower than Class 2
ceramics like X7R.
Go to the Novacap site. There is a tech bulletin that
explains some of this. Also see AVX.com, good stuff there.
On Thu, 26 Sep 2002 12:44:46 GMT, Fred Bloggs
>> I just found out that ceramic capacitors can exibit a piezoelectric effect
>> that in presence of mechanical vibrations on a board, can produce electrical
>> noise on a line that the capacitor is suppose to decouple...
>> The phenomenon may not be negligeable on big size surface mount caps.
>> The paper said "some" ceramic capacitor..
>Can you cite this paper? And I am perplexed by the statement that NP0
>dielectric does not exhibit piezoelectric effects since it is the same
>material in a blend of N-egative and P-ositive tempco to yield 0.
>> Does anyone have any information on precisely what kind of ceramic capacitor
>> would particularly exibit this behavior ? ( NPO, X7R, X5R, Y5V, Z5U ... ? )
>> Searches onthe net didn't bring anything relevant.
>Even if it does, the bulk component continues to exhibit capacitance
>which will attenuate the voltage greatly- probably because of the large
>effective output impedance of the small region producing the emf.
>Maybe you can use a microphonics damper as shown here:
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