#RaspberryPiPico silicon teardown time!
Board as received optical + x-ray images
Inspecting package. X-ray shows bond wires easier after removing thermal slug
Thermal slug removed w/ HCl + H2O2
Decapped to show copper bond wires connecting die to package pins. Initially used only nitric acid which destroyed copper bond wires (last image). Fixed by switching to mixed nitric + sulfuric acid