ICtok lemaras recept

[Fuzesi Arnold]

Opening of plastic encapsulated IC

SAFETY WARNING !  Used chemicals are extremely dangerous.
Use a fume cupboard and gloves !

Chemicals:

1. Etching acid         4 parts 100% fuming nitric acid
                        1 part   96% sulphuric acid

2. Epoxy solvent        dimethylformamid

3. Neutralizing liquid  isopropyl alcohol

Procedure:

1. It is adviceable to machine a small recess onto IC surface to speed 
up the process. Depending on IC about 0.5 ... 1.0 mm deep is good.
Put a block or piece of aluminium sheet onto hot plate. A piece of
8 mm square Al bar fixes nicely normal IC. It also shorts legs and
protects it from statics. Heat transfer is also good.

2. Put the IC on hot plate, tempereture about 60 - 70 C.

3. When IC has heatened to over 60 C, apply with pipette a drop of
etching acid into recess (5-10 drops on large IC's). Etching time 
- depending on temperature - is 1-3 minutes.

4. When acid has formed a hemispheric bubble, rinse circuit with warm
water, dry with tissue and finaly flush with isopropyl alcohol.

5. Put the IC into ultrasonic cleaner for about two minutes (put into
beaker containing dimethylformamid). The best way is to put circuit 
laying on its side, so that epoxy residues may fall away.

6. Finally, put IC into beaker containing isopropyl alcohol, for a
moment. Alcohol efficiently neutralizes acid residues in ultrasonic
cleaner.

7. If recess is not large enough start from 2.

Normally you will need 4 - 6 rounds to open the circuit.

Etching acid and dimethylformamid are both extremely dangerous.
However with these chemicals you can open the chip and it still works.