Re: box vs film caps (if that even makes sense)

Posted by Drey on
URL: http://guitar-fx-layouts.238.s1.nabble.com/box-vs-film-caps-if-that-even-makes-sense-tp25024p25527.html

Interesting...

"MLCC capacitors use "class II" dielectrics which are very highly polarizable ceramics like Barium Titanate. These cause MLCCs to suffer from a number of non-ideal behaviors like variation of capacitance with applied voltage, as well as less stable capacitance over temperature and piezoelectric behavior (they can act like tiny microphones and speakers). When a DC bias voltage is applied, their capacitance goes down over time until it settles to a new value. When the bias is removed, the capacitance will go partially back but not entirely - there is some hysteresis. This can be fully reversed by heating them up and allowing them to cool back down - a form of annealing. Even the best MLCC class II capacitors, those whose EIA designator begins with the letter X (like X5R) have about a 40 or 50% reduction in capacitance from 0V bias to half of their rated voltage. They end up at something like only 20% of the rated cap value at full rated voltage. Like Tantalums, they can also fail shorted, but usually not as dramatically as tantalums. MLCCs often have even LOWER ESR than a similarly-sized Tantalum cap. So, MLCCs have definite advantages and disadvantages. Pretty much the only area where it still makes sense to use Tantalum caps is when you need a stable, large capacitance in a small size. If you don't care so much about size, metal film caps are superior."

Another article that kills the multi layer ceramic capacitors for audio use

http://www.eetimes.com/author.asp?section_id=183&doc_id=1279709