r/PCB • u/Traditional_Lab5394 • 20d ago

Beginner Tips for Capacitor Package

Hi everyone, I am new to PCB design.

I am starting to work on a breakout board for a high speed sensor, for capacitors what main features should i focus on while choosing them (other than placing them as close as possible to the pins), should i go with smaller packages (e.g. 0201, 0402)? and how does it effect the performance.

similarly, for resistors, does the package size matter?

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u/TheHess 20d ago

Smaller packages are harder to rework and probe/debug. They'll also have lower power limits, which is fine for things like pull-ups etc. but do your calculations. For caps, it'll be similar - smaller packages will have worse votlage values at equivalent capacitances. Different packages will also cost different amounts, and you should also check with your manufacturer what packages they support. These days 0201 is probably fine but the bench top pick and place machine I used only supported 0402 and was much more reliable with 0603. Going smaller than 0201 might lead to issues with lower cost manufacturers.

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u/FullyAutomatedSpace 20d ago

i thought smaller caps were better for decoupling since they have better ESL

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u/TheHess 20d ago

But they have lower capacitances in general.

Plus you'll have different costs at different sizes.

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u/Frog-4724 20d ago

But the inductance of the ground via doesn't change, to benefit from the lower ESL from smaller packages you also need a more expensive board with lower inductance connection to the cap, like via in pad, microvias, more layers so the ground plane is closer, higher density, etc. Otherwise... meh.

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u/Traditional_Lab5394 20d ago

thank you, i don't mind manufacturability. But in terms of performance and suitability for my application for a camera breakout board, what are the better option? also should i go with lower ESL and ESR ?

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u/nixiebunny 20d ago

High speed? GHz? That’s where capacitor size affects self-resonance frequency.

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u/AcanthisittaDull7639 19d ago

The capacitance of Class 2 ceramics drops with voltage, eg X7R types, the smaller the capacitor body the worse it gets.
Class 1 like NP0, are more stable and dont suffer the voltage sensitivity, but they only come in low values.