>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