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Date: | Thu, 15 Feb 96 08:48:27 gmt |
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>Does anyone have any information on the affects that the soldering
>process has on X7R or Z5U type dielectric capacitors? What change in
>capacitance can be expected due to the result of capacitor aging?
>
>**************************
>
>According to Howard W. Johnson and Martin Graham in their book entitled
>"High-Speed Digital Design, A Handbook of Black Magic":
>
>Z5U and X7R capacitors decrease in value at a rate that is proportional to the
>logarithm of time since firing. SOLDERING A CHIP CAPACITOR RESETS ITS AGING
>CLOCK.
Taking the dielectric material above its curie point for a period of time
resets the clock - it is not instant, but I would guess it is probably
pretty fast for most at soldering temp however it also takes place over a
period of time at much lower temps (often <125C) so if you cyle them up
and down slowly you actually see quite a big hysteresis loop in the C v. T
relationship!
>Z5U ages at a rate of about -2% per decade.
I have seen manufacturer data showing as high as -5% !
David Whalley
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