John McMaster writes: [via]
Many people use concentrated acids to decapsulate ICs. One alternative is to heat them up to a high temperature and then drop them to a low temperature quickly. The high temperature was supplied by a butane torch and the cold temperature from a salted ice water bath. From the brief experiments I did today, the ideal chip seems to be large, have a metal plate (large expansion constant difference), and have a passivation layer that expands under heat (pushes epoxy off of die). This chip has all three and was decapsulated in less than a minute. It does have some small amount of residue on it, but chips can be cleaned in various ways.
Using Heat Shock to Open an IC Package – [Link]