For a little project I need to decap a PIC16C57C but keeping it alive for analysis. I finally manage to have a clean “localized” decaping but I did many test before. If you have stuff needed to work with HNO3 it will be easier, there are many article on that point on the mega Interweb. In my case I’m more comfortable with H2SO4 mainly because it’s easier to source (drain cleaner that’s what I use) where Nitric Acid is regulated (explosiv manufacturing ?). So my today results seem promising, the decaping is really clean.