Some of the first chips I decapsulated, did not require complex procedures or dangerous chemicals, they were in fact some of the first inter grated circuits (the older people amongst us will remember they were of white ceramic with 'gold' tops).
These first integrated circuits came out of computers from a company Called ICL
, a friends father used to be a service technician and as such the boards were usually scrapped off, due to reliability concerns.
Usually we opened the devices with a screwdriver/knife then used a magnifier to look at the circuits.
Fast forward to today:
When most Ic's are packaged with the packaging material in contact with the top of the die.
This particular 'etch' was something I threw together, from an IC that had been removed off a burnt PCB (see the IC legs), the actual package was intact, the pitting you see was the mixture of HCL+Sulfuric acid (Ok, I had run out of fuming Nitric acid*), spitting and hissing on the IC material.
* High quality nitric acid is something else to see, when you have the good stuff, it actually produces brown/red fumes when in contact with the air.
This Material is easy to get hold of in China, but it can be illegal to have in Hong Kong (partly due to people throwing bottles of acid from rooftops onto crowds below.(such things pass for entertainment in Hong Kong)), it tends to be a very energetic oxidizing agent (read highly explosive when mixed with organic materials)
The main purpose of the experiment was to find the optimum method for decapsulation for this IC type, without destroying the chip surface or bond wires and to understand the possibilities of in house decapsulation.
To activate the acid we added heat to the IC to get the case temperature up to about 90 degrees C, put on our 'rubbers' and goggles then applied small amounts of acid with a glass pipette (this whole operation was performed outside the building, since any gasses produced would be highly toxic/corrosive).
So we have our decapsulated IC, now we need suitable equipment to examine the chip surface.
Here we see a 3D microscope , with 5,10,20,40,60,100X primary lenses and a 10,16X eye piece.
One eye piece has an attached microscope camera.
Key features of the equipment are polarizing filters and a top and bottom lighting system for the sample, it is critical that your microscope equipment is designed for top lit operation, since most other microscopes rely on light passing through the sample so that an image can be formed on the lens system.
With a top lit microscope, the light is actually passed DOWN the lenses, bounces off the sample and is then reflected back up into the lens, this allows you to view samples that are not translucent to light (IC packages), this type of equipment is usually used by Geologists or for metal structure & crystal analysis.
One major balls up... when my cameras were delivered they were for eye piece mounting rather than a "C" mount, this means I loos e the function of one eye piece when using the camera.
With a "C" mount camera the device fits into the pillar just in-front of the eye piece assembly, that way you can still use both eye pieces.Why use an eye piece camera?
Above we see an image of the chip surface, taken with a standard handheld camera whilst trying to focus it through the eye piece
(not too bad, but I have had time to practice).
This technique is extremely time consuming and difficult to accomplish, since the hand held camera optics have to be aligned exactly with the microscope optics, otherwise you just get pictures with large areas of black, the above picture has already been trimmed by about 50%, in an attempt to remove these areas.
The picture actually shows a "dummy" metal mask, that the manufacturer has added to protect the intellectual property contained in the chip, whilst it looks 'cool' it is totally useless for information( other than the fact that something is hidden underneath).
The following image was taken with the custom eyepiece CCD camera.