MLCC SMD Stacking Plates

[dknguyen]

I can get 4.7uF 25V X7R caps for about $0.60 each. Anything larger remotely larger (and not even in X7R) costs about $5.00 each. So I want to stack them. I'm not sure if it's okay to just stack them by soldering them on top of each other on a PCB (I'm don't think they woudl say put either). BUt I was wondering if there was anything that might make it easier? I'd prefer not to have to put them side by side on the PCB just because there would be so many if no stacking was done.

**broken link removed**

 

[mneary]

Do you need ceramic? Is it non-polarized? What's your ESR requirement? An aluminum electrolytic in fairly large values still costs a lot less than a dollar.

 

[Speakerguy]

You can also change the package footprint and solder them on edge. They actually perform better at really high frequencies this way.

 

[dknguyen]

I'm not sure about ESR, but this is to boostrap a gate driver IC on the highside that is not designed to do so (therefore it has a mA level quiescent current) so leakage and frequency response do matter.

I try not to use electros anywhere on my boards. Just a personal preference- a strong personal preference.

Speakerguy: You mean solder them on their thin side down rather than flat side down?

 

[Speakerguy]

Yes. There is a TI app note that talks about why it's superior for bypass applications to solder on the side. Interesting app note, called something like "How (Not) to decouple high speed operational amplifiers". IIRC.

If they are HV caps they will be thick and soldering thin side down won't do much good. But if they are thin it could help.

ETA: Found the app note:

https://www.electro-tech-online.com/custompdfs/2008/03/sloa069.pdf

 

[Hero999]

Just use an electrolytic, even if you have to make it oversized to get the characteristics you desire.

Using ceramic capacitors with values greater than 1:mu:F doesn't make any economic sense.

If you want a good quality capacitor, then use a tantalum but becareful with the voltage rating. I've heard they can easilly melt down if overvoltaged, even for a short period of time.

 

[dknguyen]

These are 15V max but I am using 25V rated caps at which I don't trust tantalums for (just things I've heard, and it's been so long since I bothered to look at them I forget if you can get them at 50V+ at the values I want, you know that 50% derating thing)

 

[Speakerguy]

Do you need MLCC? Try Digikey PN 445-2898-ND. 10uF Radial X7R ceramic. 1.50ea.

 

[Speakerguy]

Did you ever find a solution?

 

[dknguyen]

I'm still deciding whether to cram a bunch of MLCCs or use an MLCC with a very large.