Don't bother desoldering soldered RAM.

Technically yes, you can desolder BGA RAM chips and replace them with larger ones using a rework station. But the success rate for anyone who doesn’t do this daily is low—like 20-30% low. Even then, it’s rarely worth the hassle.

The process is finicky. You need a proper BGA rework station (cheap ones are useless), flux, stencils, and the exact matching chips. One wrong temperature profile and you lift a pad or cook the board. Then you’ve got a dead laptop. And that’s assuming the BIOS and memory controller even support the higher density chips—sometimes they don’t, and you’re stuck with a system that won’t POST.

For professionals who do this full-time, success rates can hit 80-90%. But those folks charge hundreds, and you’d be better off selling your current machine and buying one with the RAM you need. The only time it makes sense is if you have a rare or expensive board that can’t be replaced, or you’re doing it as a hobby project.

Unless you’re that hobbyist, just buy the right machine from the start.