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2220 capacitors near board edge

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cupoftea

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Hi,
In the atatched layout of boost 5v to 24v at 3A75, there are the four shown "y" caps (2220) from chassis ground to circuit ground.
Would you agree they are too near the board edge and could suffer depanelisation damage.
Would you also agree that they woudl better be more like 1nF, in as small as package possibel for the voltage range?
C26, C25, C17, C18
(C26 is just 1.25mm from the board edge)

C2220C104KDRACTU

caps_2220.jpg
 

Hi,

in general, if you are concerned about a sort-circuit failure mode of your capacitors, you should try to place them in a way the electrodes are facing towards the smaller dimension of your board, in your picture in y-direction (rotate them by 90°). So they are less exposed to stress e.g. due to vibration.

Further, you can use so called open-mode or flexi-mode capacitors [1], but they are more expensive and available with lower capacitances due to their functional principle.

[1] https://www.arrow.com/en/research-a...roducts-for-demanding-automotive-applications

BR
 
you should try to place them in a way the electrodes are facing towards the smaller dimension of your board,
Thanks, i always tend to think the same thing, but in this case, people tell me that because they are in the corner of the board, they will be safe from flexion?
Also, i have a question on the Y capacitor function, but for that i believe i must start a new post?
 

Hi,
Thanks, i always tend to think the same thing, but in this case, people tell me that because they are in the corner of the board, they will be safe from flexion?

if they are mouted in the vicinty of a mounting point, the capacitor is not that stressed compared to a placement e.g. in the center of the board. In the the vicinity the of the mounting point/srwe, it is more stiff, where the board is more deflected in the (non-fixed) center. Just, imagen to add force on your shown board (e.g. phusing with a finger) when it is fixed, and where less force is needed to deflect the board. But be aware, by mounting the capacitors in the vicinity to the scweing/mounting holes, it is more likely that they be damaged by e.g. a srewdriver during the installation process.

If it comes to the sparation of already populated boards, have a look here [2]. But of course, to achive this, you have to align with your EMS.

[2] https://ele.kyocera.com/en/product/capacitor/ceramic/mlcc-handling/mounting-02/

BR
 

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