Is it possible to replace the APU with a new one?

Hi, I read that the APU is “married” to the PS4 motherboard is that true? I have a PS4 with a defective APU on it so reflow/ reball wouldn’t fix it. But I could get a replacement APU. I knew that the PS4s Bluray Drive board is married with the motherboard but the thing with the APU married to the motherboard is new to me. Can anyone confirm or give any information about that topic please?