You can't upgrade soldered RAM — and trying will void your warranty.

Yes. Soldered RAM is physically attached to the motherboard. It’s not a slot you can pop out. Any attempt to desolder and replace the chips is a motherboard-level repair that almost no manufacturer allows under warranty. Even if a third-party service does it cleanly, the board has been modified. Warranty voided.

Most laptops with soldered RAM are designed that way to be thinner or cheaper, not to be user-serviceable. If you want upgradeable memory, buy a machine with SODIMM slots. Future you will thank present you. This is not a thing you can hack around.