Dissolving cured epoxy is not easy. It requires a fairly concentrated solution of potassium hydroxide in water. The epoxy is immersed in the solution and it is boiled until the epoxy gradually dissolves. If the epoxy has a filler in it such as silica, forget it. To dissolve the silica requires an acid so you would have to alternate between acid and base. I had to do this once at work and had to have an identifiable IC in the end. It took hours to dissolve just a microscopic layer, so it was not feasable to do.