Don't upgrade soldered MacBook Air RAM.

Technically possible, but I wouldn’t.

There are a handful of shops that will micro-solder new RAM chips onto the logic board. It’s not a simple swap — they have to remove the old chips, clean the pads, reball new ones, and hope the firmware plays nice. Apple doesn’t support it, and the firmware can reject the change or behave unpredictably.

The risks are real: board damage during the process (one slip and the whole logic board is toast), instability or crashing later, and near-certain bricking if you ever need a macOS update or logic board repair. On top of that, it costs several hundred dollars — often more than just selling the old machine and buying one with the RAM you need.

If you’re stuck with 8GB and need more, sell the Air and buy a used 16GB model. That’s cheaper, safer, and actually works.