Upgrade the SO-DIMM, not the soldered RAM.

No, you can’t upgrade the soldered RAM. It’s permanently attached to the motherboard. The removable SO-DIMM slot is your only way to increase total memory.

That slot lets you add or replace a stick to get more RAM, but you’re stuck with whatever is soldered on. So if you have 8GB soldered plus a 4GB SO-DIMM, you can swap the 4GB for a 16GB stick and end up with 24GB total. Just make sure your laptop supports that configuration — some models max out at a specific amount.

Also, mixing sizes usually means the RAM runs in “flex mode” (dual-channel for the matching portion, single-channel for the rest). Performance loss is minor in most real-world use. It’s better than being stuck with 8GB.

This is not where you try to desolder and resolder memory chips. Leave that to repair wizards with hot air stations and a high risk tolerance.