Decapsulate Microcontroller Silicon Package which has helped to provide the protection over the chip wafer from moisture and air, microcontroller can be decapsulated using 100% Nitric acid heated to 60°C. It was added in small drops and washed away with acetone after a few seconds.

Decapsulate Microcontroller Silicon Package

This MCU decapsulation process was repeated for several minutes until the surface of the chip die was exposed. Although the bonding wires were also exposed, this did not create any short circuits because of the high concentration of the acid. Once the IC decapsulation was finished, the whole sample was cleaned in acetone using ultrasonic bath. That removed the remaining of the acid and particles of resin. As a result the surface of the chip became clean. After careful removal of the tapes and testing the device demonstrated full functionality (below Figure).

PCB of the security token after live decapsulation

It is very important to make sure that the microcontroller is not over-decapsulated. This would result in the acid going into contact with PCB traces made of copper. They react very actively with acid and this will quickly result in loss contact with bonding wires. The device with live battery connection could then be used for further IC extraction of the embedded SRAM using microprobing MCU attacks.

Comments are closed.