Decoupling capacitor on STM32H7A3NG

[LDi T.2]

Messrs ST,

my customer has asked to me to replace their actual microcontroller with STM32H7A3NG: the more difficult thing is the placement of decoupling capacitors because their placement is not permitted on the bottom of the PCB (as best practice for BGA package); so I have to ask you if such a attached placement is feasible for our STM32. Can you kindly verify if the placement of capacitances all around the BGA package is feasible and can work?

[Tesla DeLorean]

You should really work with the FAE assigned to your account, out of the local sales office.

[TDK]

It's not a binary good/bad sort of thing. Longer traces are worse but typically will still work. If you are pushing the chip to its limits in terms of temperature, current, frequency, capacitor location will become more important.

[KiptonM]

I agree with Tesla and TDK this is not a simple question to answer in this forum.

My general answer is it depends on the frequency of the board. You can probably get away with it on low power microcontrollers running under 32 MHz. As the frequency increases and the power increases the likelihood of it working well diminishes. More ceramic capacitance distributed on the board to the power plane and the ground plane can help after you have taken care of the close pins.

Unfortunately the only real answer will be to try it. But make sure the customer understands there are no guarantees.

[LDi T.2]

Thank you all for your precious suggestions.

Best Regards