decapsulating ICs

[whiz115]

Hi...

sodium hydroxide (the chemical we use to develop PCBs) is it suitable to decapsulate transistors and ICs? or i have to use sulfuric acid?

thanx!

 

[jpanhalt]

I am not sure either is a very good choice. Presumably, you need an oxidant to degrade the "epoxy". Sodium hydroxide is definitely not that.

Sulfuric acid will char (oxidize) plastics. The more concentrated the better. Nitric acid is probably better. A chromic acid-sulfuric acid mixture (old-time chromic acid cleaning solution) is probably even better. There are lots of possibilities, but I would do a bit more research on it before starting out.

I doubt there is a simple answer, and the above possibilities should not be tried by someone who is inexperienced.

John

 

[whiz115]

i want to use a chemical that is easy to find and can disolve the epoxy...

i agree it's dangerous, also the chemical we use to develop photosensitive boards is dangerous but for many people is something ordinary to use

 

[Nigel Goodwin]

i want to use a chemical that is easy to find and can disolve the epoxy...

I doubt you're going to find one - I think it requires fairly exotic and hard to obtain chemicals?.

 

[atferrari]

And how to stop?

I wonder how are you going to stop the process when the epoxi is gone and the innards of the IC in question are openly exposed to those chemicals? Could you?

 

[jpanhalt]

Here is a description from a document I had from University of Cambridge (Sergei P. Skorobogatov, Technical Report Number 630,
Computer Laboratory, UCAM-CL-TR-630, ISSN 1476-2986).

The process of manual decapsulation usually starts with milling a hole in the package so that
the acid will affect only the desired area above the chip die (Figure 50). The tools necessary for
this operation are available from any DIY shop for less than £10.
The commonly used etching agent for plastic packages is fuming nitric acid (>95 %), which is a
solution of nitrogen dioxide NO2 in concentrated nitric acid HNO3. It is very strong nitrifying
and oxidizing agent; it causes plastic to carbonise, and it also affects copper and silver in the
chip carrier island and pins. Sometime a mixture of fuming nitric acid and concentrated
sulphuric acid H2SO4 is used. This speeds up the reaction with some types of packages and also
prevents the silver used in bonding pads and chip carrier from reacting.

Note that nitogen dioxide and nitric acid are in the context used here equivalent (NO2 and its dimer, N2O4, are gases; HNO3 is the liquid form). Both nitric acid and sulfuric acid are readily available in the USA.

John

 

[Hero999]

It depends on what the packages are made of?

If it's ceramic, i.e. glass (silicon dioxide) based then you have a problem, hydrofluoric acid can dissolve glass but I think it will also dissolve the silicon die.

 

[whiz115]

looks like nitric acid with sulfuric acid is what's needed... but how is it inactivated?!


@Nigel Goodwin the exotic ones do better job they don't spoil the IC only remove the epoxy...but these chemicals can be much more toxic than these we're talking about. i have found many of them on google and i'm glad they are exotic we don't need em around.

@atferrari the same way you stop the process when you develop boards
and you don't want the chemicals to eat up all of your pcb.

@Hero999 i'm interested only on usual packages...not ceramic ones.

 

[Hero999]

Acids can be deactivated by mixing with an alkaline solution, sodium bicarbonate or calcium carbonate (chalk) will do.

Ceramic packages are quite common but as long as you're sure it's epoxy the you'll be fine.