FCBGA1440 Compatibility

[caveman123]

So I'm pretty sure I know the answer to this but my friend gave me their acer pre-built with a i5-9400h, socket FCBGA1440. I was wondering if that would be compatible with your typical LGA 1151 motherboard if someone wanted to upgrade the motherboard? 

[BobVonBob]

FCBGA1440 is soldered, not a socket. They're bare die CPUs soldered directly to the motherboard and are used in laptops or, as you have found out, prebuilts. While replacing it is technically possible, you could only replace it with another FCBGA1440 chip, and desoldering massive BGA chips runs a high risk of cooking the board into oblivion if you don't know what you're doing. Very much not recommended. You'll need to get a new CPU, motherboard, and cooler if you want to upgrade.