John McMaster Turns to X-rays, Acids to Tear Down Raspberry Pi's New RP2040 Microcontroller Silicon
Self-professed reverse engineer offers an in-depth analysis of the RP2040, created by X-raying the chip then de-capping it with acids.
Reverse engineer John McMaster has turned his attention to the RP2040, the first in-house silicon from Raspberry Pi, sharing a series of images ranging from X-rays of the chip and Raspberry Pi Pico carrier microcontroller board to physical die shots.
Launched late last month, the RP2040 represents two firsts for Raspberry Pi, being the first device from the organization's in-house application-specific integrated circuit (ASIC) team and its first microcontroller. Launching in the Raspberry Pi Pico, the RP2040 has drawn considerable interest — and McMaster's curiosity.
In a series of Twitter posts, McMaster has analyzed both the Pico board and the RP2040 microcontroller - starting by putting them under a high-resolution X-ray imager. "X-ray shows bond wires easier after removing thermal slug," he writes, before beginning a more destructive analysis: The removal of the package from the silicon die using corrosive acids.
"De-capped to show copper bond wires connecting die to package pins," McMaster continues. "Initially used only nitric acid which destroyed copper bond wires (last image). Fixed by switching to mixed nitric + sulfuric acid."
Using the de-capped chip and a high-resolution microscope, McMaster has been able to post a series of detailed images of the underlying silicon die — including finding a hidden Raspberry Pi logo and markings which identify the die as a likely B0 silicon revision and an eight-metal-layer chip and which confirm Raspberry Pi's announcement that the part is produced on a 40nm process node.
The full analysis, which includes identifying components including RAM, seemingly-unused power pads, digital logic transistors, and IO IP, can be found on McMaster's Twitter thread.
