polar capacitors

[engr_joni_ee]

Hi, I guess polar capacitors are not available in 0603, 0805 and 1206 ceramic packages. In which packages polar capacitors are available ? Are they tantalum which are polar capacitors ? They are bigger in dimension compared to ceramic, right ?

The other question is can we use a non polar capacitor in place of polar capacitor in PCB. What is the purpose of using polar capacitor in schematic and not non polar ?

 

[danadakk]

Hi, I guess polar capacitors are not available in 0603, 0805 and 1206 ceramic packages. In which packages polar capacitors are available ? Are they tantalum which are polar capacitors ? They are bigger in dimension compared to ceramic, right ?

Polars are Tants for SMD packages.

Generally speaking Tants are bigger because the have larger C than ceramics.

Smallest package is .6 x .33 mm

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The other question is can we use a non polar capacitor in place of polar capacitor in PCB. What is the purpose of using polar capacitor in schematic and not non polar ?

Depends on what cap is used for and its C, Ceramics have (generally) better ESR than polars, so in
bypass applications generally better. But they are limited to somewhere around 25 uF. Application
dictates what to use, eg. tolerance, drift, sensitivities.....


Regards, Dana.,

 

[D.A.(Tony)Stewart]

The smallest polar e-caps in Alum. might be 3.3 mm square in tall cylindrical cans

General Purpose $0.184/pc in 2k reel up to 22 uF

bigger uF/$ but higher ESR/$ >1uF so you might need a combination of parts.

roughly...using f-3db= 0.35/C*ESR(=T)

G.P. e-caps <=30 kHz
Low ESR e-caps <=300 kHz
Ceramic, film HF to UHF depends on size.

 

[barry]

Hi, I guess polar capacitors are not available in 0603, 0805 and 1206 ceramic packages. In which packages polar capacitors are available ? Are they tantalum which are polar capacitors ? They are bigger in dimension compared to ceramic, right ?

The other question is can we use a non polar capacitor in place of polar capacitor in PCB. What is the purpose of using polar capacitor in schematic and not non polar ?

Tantalum (polarized) capacitors are most certainly available in 0603, 0805, etc.

Contrary to what Dana says, tantalums are NOT bigger than ceramics; they are much smaller for a given capacitance. That's one of the main reasons for using them!

 

[danadakk]

General capacitor esr performance :

OS-CON is polymer tantalum.


Regards, Dana.

--- Updated Apr 16, 2023 ---

Tantalum (polarized) capacitors are most certainly available in 0603, 0805, etc.

Contrary to what Dana says, tantalums are NOT bigger than ceramics; they are much smaller for a given capacitance. That's one of the main reasons for using them!

Contrary to what Barry says, tantalums are bigger than ceramics; they are bigger for a given capacitance.
Now qualify that, I did not search the entire solar system for the smallest cap, just used Digikey searcher
for the following.


1 uF MLCC 0.016" L x 0.012" W (0.40mm x 0.30mm) 0.018" (0.45mm)

1 uf tant 0.039" L x 0.020" W (1.00mm x 0.50mm) 0.024" (0.60mm)

Smallest of each I could find at Digikey.


Regards, Dana.

 

[barry]

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Order today, ships today. T491X108K006AT – 1000 µF Molded Tantalum Capacitors 6.3 V 2917 (7343 Metric) 600mOhm from KEMET. Pricing and Availability on millions of electronic components from Digi-Key Electronics.

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1000uf, 6.3V. 7.3mm x 4.3mm.

Your move.

 

[D.A.(Tony)Stewart]

Smallest Tantalum 0201=0.47 uF, 0402=1 to 10 uF , 0603 <=100 uF
Smallest Ceramic 01005=0.1uF

Not exactly the same specs, but both Dan and Barry are correct, you can get small sizes in both above parts which helps to lower ESL and raise SRF.
Whereas Alum. cans in SMD start at 0.3" rather than 0.01"x 0.005" for ceramic.

 

[KlausST]

Hi,

1 uF MLCC 0.016" L x 0.012" W (0.40mm x 0.30mm) 0.018" (0.45mm)

1 uf tant 0.039" L x 0.020" W (1.00mm x 0.50mm) 0.024" (0.60mm)

1000uf, 6.3V. 7.3mm x 4.3mm.

Without identical voltage specification such comaparisons make no sense.

****
From my knowledge (years ago) the energy densitiy of tantal is higher than of ceramics.
This may have changed ... I don´t have actual informations.

Klaus

 

[engr_joni_ee]

Smallest Tantalum 0201=0.47 uF, 0402=1 to 10 uF , 0603 <=100 uF
Smallest Ceramic 01005=0.1uF

Not exactly the same specs, but both Dan and Barry are correct, you can get small sizes in both above parts which helps to lower ESL and raise SRF.
Whereas Alum. cans in SMD start at 0.3" rather than 0.01"x 0.005" for ceramic.

Thanks for reply. I did not know before that polar tantalum caps are also available in small packages like 0402 and 0603. But Tantalum are always polar, right ?

Now the question is, if in the PCB layout we have 0603 polar 47 uF and we don't have polar 47 uF tantalum, then can we just use a non-polar ceramic in same package with lower voltage rating if that is not an issue ?

 

[danadakk]

Depends on what the cap is being used for.

Post schematic.


Regards, Dana.

 

[engr_joni_ee]

What if they are just de-coupling capacitors on the power rails.

 

[danadakk]

Then generally speaking that substitute should be OK.

One caution, the inrush current will be higher due to lower esr, so
take that into consideration.

Another caution is if the cap is at output on a V regulator, consult that datasheet
if there are any min ESR constraints on its output application C. This consideration
generally a problem associated with LDO regulators.


Regards, Dana.

 

[D.A.(Tony)Stewart]

I understood you wanted to know if Polar caps come in small packages like ceramic in bulk values.
Yes they do.
You asked if you can sub ceramic for polar.
Yes you may, but compare ESR, ripple current expected, stability specs.
Now you are asking for a specific value sub. In general purpose but it is necessary to specify ;

Source regulator, load type, Voc , Irms & Ripple max.

But we cannot guarantee your choice until you specify why you need this.

 

[FvM]

We have been using effectively no Tantals in recent designs, mostly MLCC accompanied by aluminum electrolyte. With high capacitance MLCC ( e.g. X5R and X7R dielectricum) you need to observe C/V characteristic, see 100 uF 6.3V 0805 chip curve below. As a rule of thumb, don't use it above 50 % of rated voltage.

 

[KlausST]

Depends on what the cap is being used for.

Post schematic.

What if they are just de-coupling capacitors on the power rails.

The correct way is like dana writes: it depends.

I have a linear voltage regulator in stock that is not stable with extremely low ESR like ceramics capacitors for outut (power supply) decoupling.
--> If you want avoid problems there is no way around reading the datasheets thoroughly.

Klaus

 

[engr_joni_ee]

We have been using effectively no Tantals in recent designs, mostly MLCC accompanied by aluminum electrolyte. With high capacitance MLCC ( e.g. X5R and X7R dielectricum) you need to observe C/V characteristic, see 100 uF 6.3V 0805 chip curve below. As a rule of thumb, don't use it above 50 % of rated voltage.

View attachment 182321

You mean using aluminum electrolyte with MLCC ceramic is better then using Tantalum caps combination with MLCC ceramic

 

[danadakk]

If you look at earlier posted esr graph Polymer Tant + MLCC best. But probably
overkill.

FVMs post more appropriate for cost reasons and good overall performance.


Regards, Dana.