I thought they were no more durable than any other type given that they can be all too easily broken by board flexing during assembly.
Thinking more about it, why do we care about durability? Like, who takes capacitors and hits them with a hammer or something after manufacturing?

Durability matters a whole lot in those applications where "production yield" matters. "production yield", for those unfamiliar with the term, is the portion of product coming off the assembly line that meets all the specifications and is ready to be packed up and sold. 100% is the target, and mostly if it does not exceed 95%somebody is in trouble.

 

Hello,
In every schematic from a datasheet I've ever read, they always either explicitly say that the decoupling caps are ceramic, or they show them as being non-polar thus leading one to guess either film or ceramic caps are required (film have very high ESR in my experience, so they may not work). C0G/NP0 is impressive over frequency and temperature, but I'm still confused.

Why are decoupling caps never aluminum polymer or tantalum polymer?

Thanks

It truely depends on the application and what your trying to decouple as every technology has trade offs.

Most IC's recommend using ceramics as they have low esr and high Self Resonant frequency which give a good low impedance source for pulses of current to be pulled from the capacitor to power the IC during normal operation. As these pulses usually have fast moving edges, for EMC reasons these capacitors tend to focus on the 1 to 150Mhz regions which naturally make them small in value and physical size. Ceramic components have physical manufacturing limitations which means they are fairly limited in capacitive size and voltage. Ceramics can also resonate at low frequencies that can cause audible issues if hit with the right frequency. Theres many different Ceraminc Technologies. X7R, X5R are very common for larger capacitances and COG/NPO are good for smaller values and applications where stability is needed.

Electrolytics, Polymer, & Tantalum area good for applications where high capacitance is needed. The polymer electrolytics tend to have lower ESR and higher ripple current capabilities but the self resonant frequencies are usually mid 100's of Khz at best so pretty hopeless for RF noise filtering. They are often used as mass storage of energy. Downside is usually the life of them which tends to be much lower than ceramics. Due to their limitations in EMC due to the Low SRF they are often used with ceramics to get the best of both worlds.

 

Hello,
Could you please expand the two abbreviations here?
Thanks

> Due to their limitations in EMC due to the Low SRF they are often used with ceramics to get the best of both worlds.

 

EMC= Electro Magnetic Compatability, SRF is less common, but consider the context. SRF= Self Resonant Frequency.

 

Think about capacitors as a charge separating mechanism. (+++| ---) The action with AC ripple and noise is the change in polarity.
The DC cannot pass through the dielectric but the AC electrical counterpart does. The DC current proceeds in a loop in the component that was designed to have an external bypass capacitor to work within the PSRR specs. The multi layered ceramic capacitors makes an easy pathway for AC
while blocking DC.

Marconi used ceramic capacitors for transmit. Mica was another dielectric used in receivers. The capacitor varieties here were designed around the
active component and other capacitors designed for circuits like RLC. The vacuum tube circuits used capacitors designed for tube type characteristics. Bell labs used Tantalum for transistor type characteristics. The aluminum alkaline paper Ecap is also used for decoupling which deals with transient surges and as a filter capacitor. A Mosfet will turn on and off, it is up to you to explore that voltage threshold so you understand why a mosfet circuit can be out of spec, why the datasheet will recommend a bypass capacitor close to the input as a detour for noise. ≈ (--- | +++) ≈ ⊥Θ

 

Capacitors have a huge range of capabilities. Use what's needed for each application.

 

Out of curiosity, what is that @nsaspook ?

 

Out of curiosity, what is that @nsaspook ?

RF match for a plasma chamber.
https://phxitech.com/srn/