TLDR: bulk material for standard packages can be removed using a fiber laser. However, a CO2 laser will not work (lower peak power ⇒ melts silica instead of ablating it). However the laser will damage the die surface if you try to go all the way to the surface (without using a special setup like FALIT). Finally, COB epoxy appears to be workable even with a CO2 laser
General results
From Sam Wagner:
Above: laser decap from below (Source)
https://www.jamiecraig.com/de-encapsulating-ics-with-a-laser-cutter/
Above: source
http://siliconexposed.blogspot.com/2013/08/laser-ic-decapsulation-experiments.html
https://www.youtube.com/watch?v=-x4lyX1C4q0
https://www.youtube.com/watch?v=SvWgSs2_f00
https://www.youtube.com/watch?v=sSRl3Vqbos8
TODO: add pictures, estimate material removal rate
Basically this was too slow to be practical except for very small samples. That said, it did work very well. A quicklase or other higher throughput Nd:YAG system would likely work well
Remove bulk epoxy
https://twitter.com/johndmcmaster/status/1641575200109244416
Can be used to cut open package
Seems to also work