These "through the hole" components,which I have always assumed were MLCCs with leads attached.would probably have used that earlier construction.
Logically,currently available"through the hole" components must use the same technology as SMD's.so they probably exhibit the same behaviour,& are subject to the same limitations.
Does anybody know if this is so?
That is precisely the case.
By the way, for anyone shopping for their best choice of capacitor:
For a given nominal capacitance rating, get the highest voltage available (usually topping out at 50V), in the desired package size. Examples:
All these are X7R. Don't get worse than this if you have the option (X5R has a smaller temp range but same spec otherwise; anything Z5U or related is just crap).
50V 0.1uF 0805 -- 0.1 might also be available in 50V for smaller sizes (0603, 0402?), but whatever the highest voltage is, get that.
10uF 0805 -- 16V is usually tops, I think?
10uF 1206 -- 35 or 50V
47uF 16V 1210, maybe 1812
Don't get bigger than 1812, they're much more liable to crack. IPC doesn't even really recommend going over 1210, but that might be coming from a maximum reliability (military?) angle.
C0G:
Small values (up to 1nF is economical): doesn't matter
2.2nF 630V 1206
10nF 630V 1812
Most economical for higher voltages and high dV/dt. High voltage kind of precludes small package sizes (1206 at 630V or more is already pushing it).
FYI: type 1 dielectrics exhibit very little to no voltage effect. I've blasted "100pF 50V" C0G disks at 500VAC (and as many kHz) with no effect (they got slightly warm from the current, that's all; a 2kV Y5P in the same place barely lasted seconds before effectively shorting out the oscillator). Not that I would recommend or condone such abuse of ratings, but they are very robust, and well worth the cost when needed.
As for type 2 dielectric variability, I don't know that they've advanced all that much in a
decade, but certainly since the early days. I have some truly monstrous 120pF NP0 (now called C0G) disk caps. Probably rated 500V, but probably don't break down until a spark physically jumps the pins (5-10kV). Even the Z5Us were terrible in size. But aside from tolerance (Z5U has always been the same +80/-20% definition), no one much cared about voltage coefficient or aging. And they might not've noticed, because the voltage coefficient on such a huge capacitor is pretty small.
Also back in the day, voltage ratings might've been for safe operation AND meeting tolerance. I made this plot from an unknown ceramic cap,
only labeled "223Z". If it's rated less than 25V, it still meets spec (well, not currently.. but would've, and probably would again after additional annealing?), and there's no problem.
So where they got off removing voltage from the tolerance, if it was ever used in the first place, I don't know. It's absolutely true that there's no relation today, and one must be constantly mindful of this.
So, if you're still wondering, what's the difference between voltage ratings, anyway? Number of layers, and thickness of layers. The chip cap is solid ceramic, through and through, so you're paying for that regardless -- what you're paying for is the number of layers (a production time cost, and a small cost in palladium or whatever they use), which is why there's a small difference in price across voltage rating (for a given capacitance; or vice versa).
The reason I would suggest getting the biggest (highest C, V for a given size; but also the most expensive) is because, this combination pushes the material limitations, so that you are most likely to get capacitors with a similar or equal curve of C(V in %), so you can safely use the same adjustment factors (rated voltage = 2-3x nominal) and get the same expected performance.
You can always cost-reduce from there, if you need to.
Tim