The number of counterfeit semiconductors being introduced into the supply chain is on the increase, and as the numbers increase, so does the sophistication of the counterfeiters themselves. Organisations strive to reduce cost and stay competitive. In doing so, some, may purchase devices from unorthodox sources.
Challenged with the problem of how to effectively detect counterfeit semiconductor parts. Companies are increasingly turning to detailed visual inspection to ensure counterfeit or defective devices do not make it to their production line.
A visual inspection is performed on a sampling of devices from a given lot. Device markings and dimensions are compared with the manufacturer’s datasheet for authenticity. The lead finish is examined for evidence of previous use or refinishing. The body of the device is examined for evidence of improper handling or previous use. With more sophisticated counterfeits, a visual inspection is often insufficient. Being able to look inside the package is often required. De-capsulation is destructive, but can reveal many hidden features.
If you see a high percentage of DOA components purchased from an unorthodox source, how do you know if the devices really carry die or are simply empty shells designed to increase your suppliers margin?
If you see a high percentage of DOA components purchased from an unorthadox source, how do you know if the devices really carry die or are simply empty shells designed to increase your suppliers margin?
Some flash memory and eeprom devices protect the code image with internal lock bits, set as a final step at the end of programming. When set, these bits prevent the microcontroller programmer from "downloading" or "reading" the internal program. In practice, the only way to erase the lock bits is by erasing all memory, which allows the device to be reprogrammed but destroys the program memory contents in the process.
The lock bit approach can be easily defeated. A careful study of the die layout and selective erasing of areas of the die with a UV source or eprom eraser can reveal the location of the security lock bits. This technique is often performed on UVerasable EPROMs. After decapsulation, the die is painted with opaque paint or even electrical tape, and pinholes carefully made over the location of the lock bits. Exposing the device to a strong UV light then erases the security lock bits, yet leaves the main memory array unaffected. The device can then be read in a standard programmer as though the lock bits were never set. Pictures below show a device with the code area protected with opaque material prior to UV exposure to remove the security protection.