<Last part of the previous post>

Perhaps it's time to comment on this thread.

Dichloromethane and dimethylformamide are relatively effective disrupters of most epoxies but their action is accompanied by great swelling because the polymer becomes engorged with the liquid before any significant solvation takes place. This will destroy wire bonds on an IC.

Fuming (essentially anhydrous) sulfuric acid acts by the completely different process of sulfonating reactive groups that remain on the polymer. The depolymerized and sulfonated byproducts are quite soluble not only in the acid but usually in water as well. The worst thing that you could do in this relatively straightforward process is to wash with water at intervals because this would initiate almost instantaneous corrosion. It would be advisable for a chemist, as someone trained in the handlingof reactive materials, to carry this out or at least to establish procedures and train others with less experience. The action of sulfuric acid in this regard is quite different than that of nitric. Nearly anhydrous nitric acid (completely anhydrous is extremely difficult to prepare) is a very powerful oxidizer and could lead to unstable, dangerous byproducts whereas the sulfonates resulting from the sulfuric acid reaction are relatively stable. Water must, of course, be prevented from splashing into any concentrated acid, especially sulfuric.

A very strong acid such as sulfuric behaves completely differently in the absence of water. Since most acids are highly hygroscopic and are sold as water solutions, most people do not observe this other side of their behavior. Without water to create an ionized electrolyte, corrosion of metals will not take place. I have de-encapsulated ICs for failure analysis in 200 degree sulfuric acid and been able to operate the IC without replacing the .001" aluminum wirebonds that it came with. I recall one instance where our company built prototype hybrid microelectronic circuits out of such de-encapsulated ICs when their supplier was late getting a new design on the market and the only ones available were already encapsulated.

The key is to realize that water must be excluded until the sulfonating acid has been completely rinsed away by a non-aqueous liquid. As Mr. Saxon said, there are simple and safe devices available for doing this operation. However, with proper care and protective gear it can be done in a beaker on a hot plate in a fume hood. A few ml.s of sulfuric acid are heated to drive off water until heavy vapors are observed over the liquid (which may darken during heating due to trace impurities). The IC is carefully lowered into the hot acid and a vigorous reaction ensues with the epoxy almost instantly washing into the solution. After a few seconds the IC is then quickly lifted out and held over a receiving vessel and flooded with a stream of ethanol. Only after this is a final rinse in deionized water carried out, followed by fresh electronic grade ethanol and forced drying in warm air.

The ready made devices which carry out the operation are typically a small bowl with a hinged lid from which air is withdrawn by a gentle vacuum. An inert metal feeder tube leads from a heated reservoir for the sulfuric acid and passes through the wall of the bowl to a position where the encapsulated device is secured. When the lid is closed and the slight vacuum applied, the hot acid is pulled into the bowl over the device. It is somewhat self-limiting in that, if the lid is opened, there is no driving force to bring more acid into the container. Naturally, the vacuum source needs to be protected by a trap and all waste products properly handled no matter how the procedure is carried out.

John Twilley
Conservation Scientist
(formerly, Manager of the Reliability Analysis Center, Teledyne Microelectronics)

From daemon Fri Jan 25 08:35:53 2002

From: Darrell Miles : milesd-at-US.ibm.com
Date: Fri, 25 Jan 2002 11:45:46 -0500
Subject: IC package removal

Body of Message

Jon,

If it is the black "plastic" (glass filled epoxy), nitric acid works on some, and sulfuric acid works on most. There are also some chemicals called "Dynasolve", that we use various types of. The differences are in the speed with which the material is removed, and what damage is done to interconnects, etc. If you watch the time you have the sample in sulfuric acid, it works for most parts.

Hope this helped.
Regards,
Darrell

I have sent one PAL (Apple calls them HALs on the Mac boards) to MEFAS. You can find them at http://www.mefas.com

They offer a decapsulation service at only $45 per part with a 2-3 day turnaround. I have sent them the ASG PAL since its the only one I don't have equations for. I have requested the service of decapsulation with cleaning options for photography. This means they don't pay attention to the bond wires and attempt to clean the surface.

Their website describes their decapsulation service as follows.

I liked how they described the entry level procedure... "eye drop concentrated nitric acid in the cavity to remove the plastic from the IC."

Most companies I've found don't go into detail about how they do their service, and wouldn't admit it could be done with a hotplate and eye dropper.

You need decap equipment
 

Decapping by hand is not only extremely dangerous, but it is done successfully by very few people. Nisene Technology Group Manufactures the equipment you would need to do this. Email me at erik@nisene.com and I will set you up with a quote and resources on getting out equipment.

The hard part is getting acid good enough. After an hour of work with some over-the-counter nitric acid I had a 68000 done, but the water content was so high that it left a residue on the chip. Its still fun to look at. MEFAS at $35-40 is worth it for sure! :)

Sulfuric and Nitric Acid concentrations for we chemical decapsulation
 

Guys,

I just joined this forum and would really appreicate your help here.

What are the concentrations of the sulfuric and nitric acids you use for
wet chemical decapsulation. I'm in the process of purchasing chemicals for our chemical lab and need to know the concentration of acid in the solution that will yield the best results. I was thinking 90% Nitric Acid and 96% sulfuric acid would be ok to use but need you to confirm.

thank you

Roberto

There are several variations of sulfuric and nitric acid on the market. Our equipment uses 20% fuming sulfuric and 98% fuming nitric. I could give you a few pointers if you would like to discuss further. erik@nisene.com or 831-761-7980

X-Ray Machine for IC's
 

I work in a company that specialize in decap and test discret parts and IC's, to detect counterfeit components, we are thinking in buy a X-Ray machine, does anyone in this forum knows what kind i need to buy for this particular application?