Great video, nice to see that the HP E3620E works again.
That decapping method you use is inefficient, however.
If you go fully destructive, ie fully dissolved package, you better use hot/boiling sulphuric acid in a test tube, since it's much easier to get and has no nasty NOx production. Furthermore aqueous nitric acid is far more corrosive to metals => much more damage to the metal layers of the die.
The trick with nitric acid is that you can remove the package specifically, with no attack to metal traces, since pure nitric acid has no water in it that removes the oxides/nitrates which protect the metal. To get the anhydrous nitric acid, you need an glass destilation setup, where you can remove the water from commercial 53-65% nitric by using 98% sulphuric acid as dehydration agent or use sulphuric acid to liberate pure nitric acid from alkali metal nitrates (NaNO3, KNO3).
Works really great, did that several years ago and as I was quite pyromanic back then, I had plenty of anhydrous nitric acid available
. Best method to decap the chip is to put it onto hotplate (into fumehood/outside, with gloves and faceshield, since it splashes quite strongly), heat in near/to the boiling point of nitric acid and use a pipette to put single drops of nitric acid onto the center of the chip, where the die sits.
The nitric acid will vigorously attack the package and start to boil. This removes any reaction products that might attack the bonding wires or lead traces in the package. When finished, clean with ethanol and put in ultrasonic bath with acetone for a while.
If you stop at the right time, you can get quite nice chips with bond wires fully intact, that even work that way. Difficult part is to know when to stop, since black goo from the package obscures the die in the process and you have to guess when to stop. Too long and the die gets fully exposed and detaches from the package.