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I am using the STM32H747XIHx from STMicro. There are quite a few bypass capacitors that need to be placed. Because of space, I am using the BGA version of the part which is 15mm x 15mm with 0.8mm spacing between balls. Many of the power pins are buried deep into the BGA array. How should I place the bypass capacitors for these pins? Is the best way to put it on the back side of the PCB to keep it as close to the pin, or can I run traces out to the outside edge of the part? I'm thinking the later is too far away from the pin to be useful.

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Back side of the PCB. Should be listed with examples in the application note by serious manufacturers.

Here is an example:

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Borrowed from How important is it to put decoupling caps on the same side of the PCB?

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    \$\begingroup\$ Nearly everyone that calls out multiple power/ground pins these days also has guidance somewhere in their datasheet about laying out bypass caps. Those sections should be read carefully even if you're experienced, and flouted at your own risk. \$\endgroup\$
    – TimWescott
    Commented Aug 15, 2023 at 15:56
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    \$\begingroup\$ @TimWescott Indeed. Also, when in doubt, more decoupling capacitors, shorter wider tracks and sandwich more power and ground layers. \$\endgroup\$
    – winny
    Commented Aug 15, 2023 at 16:50

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