An anonymous maker decided that the 4GB of RAM in their Raspberry Pi 400 was too limiting — so, armed with a hot-air rework station, upgraded it to a more capacious 8GB.
The Raspberry Pi 400 launched last year as the first "consumer product" from Raspberry Pi Trading — an "object of desire," as co-founder Eben Upton told us at the time — with a custom single-board computer based on the Raspberry Pi 4 built into a keyboard housing. As a very-nearly-all-in-one system, the Raspberry Pi 400 has proven popular — but unlike the Raspberry Pi 4 family proper only comes with one choice of memory: 4GB.
That the 4GB memory chip is literally soldered into place did not discourage an anonymous tinkerer from upgrading their Raspberry Pi 400, though — by de-soldering the surface-mount part and replacing it with an 8GB chip taken from a Raspberry Pi Compute Module 4 instead.
It was no small effort: While ball-grid array (BGA) chips are usually fitted with solder balls using a stencil and a machine, the maker opted to position them by hand — all 200 of them.
"To reball the chip, I covered it in a very thin layer of flux, so the balls wouldn't roll (the layer can't be too thick, or the balls will float if you heat the flux)," the maker, identified only as "Pi800," explains. "I rubbed a tiny bit of flux on a ceramic tip, and used it to pick up one ball after another.
"The chip should be thoroughly cleaned with isopropyl alcohol after reballing. When I did so the first time, two balls fell off. They weren't actually soldered to the chip, but just stuck in flux. I probably didn't clean the chip's pads well enough before soldering."
More details on the project are available on Pi800's Reddit thread.