Never has this occurred to me and I've been buying parts from China for a good while. Well, it did punctually as in one dud in ten but never an entire batch. Let me backtrack. This article is about ST Microelectronics chips and the not-so-obvious clones sold under the original branding. Specifically, this is my attempt to arm you, dear reader, with the tools to fight this sordid cat-and-mouse game.STM32F030K6T6 - left: original, right: clone
In my case, a lot of STM32F030K6T6 proved to be something different than expected. Although they look like the original and pass the quick GPIO and USART tests, you cannot use the ADC, there is no functional timer - let alone PWM, no interrupts and I won't mention DMA channels because as you probably guessed, there's none.
So, what can I do, you'd ask. Well, the first step is visual inspection of the chips in the lot. This is of utmost importance as it can be decisive in choosing sellers. Secondly, if you bought them and have your suspicions, the functional tests will certainly reveal fakes - sadly, too late.
Any forgery, no matter how good, has its differences caused by inherent production limitations. Most of them cannot be circumvented without additional investment and most often they're deliberately ignored. Some are discreet and some are hail-Mary attempts. These constitute telltale signs to look for.
1. Shipping packaging of the here-assumed fake chips was a black ABS matrix plate wrapped 3-4 times in transparent foil. All the chips shared the same rather dusty enclosing. That's just appalling compared with another, good batch that came in plastic tape/reel with individual sealed pockets for each IC.STM32F030K6T6 clone - general LQFP32 matrix package STM32F030K6T6 original - individual reel pouch
2. Index dot shape of the fake chip is larger and has an angled dashing pattern. The image also reveals differences in the case material. The clone is more porous than the original. The latter seems deliberately rugged probably to improve grip. On a second guess, the dashed dot may hide the fact that the case material cannot be smoothed (like the one inside the original dot disk).STM32F030K6T6 index dot - left: original, right: clone (bigger, with a dash pattern)
3. Marking font of the fake chip is larger than the original, thus occupies more of the chip face. At a closer look, there are clear differences in the S, T and F characters and the rounded chars are a bit more rounded on the original.STM32F030K6T6 marking font-size - up: clone, bottom: original
4. ST logo emboss. I should have put this higher in this check-list because it the most obvious. To achieve this effect, the graphic tool must pass exactly over the same spot as the engraver and none in the clone batch seems to nail that.STM32F030K6T6 ST logo - up: clone, bottom: original (perfect alignment of the marking tools)
should reveal that neither ADC, DMA, NVIC, RTC, timers or interrupts actually work. In fact the chip resets when the execution flow reaches the initialization of any of the above-mentioned modules. The clones allow your regular tools to read/write binaries and to make simple GPIO operations. That's OK if you're just a blinky fan but it is not for the other infinite number of reasons.
Now, I'm not pointing fingers at sellers, marketplaces or at China. Most likely these chips were made in a second-hand plant on a rusty floating island somewhere in international waters and somehow ended-up being sold from there. There's also a slight possibility that the chips were part of a failed production batch that instead of being discarded, landed in a store. At least in my case - all facts indicate non-compliant clones. Since I have purchased these chips, the seller seems to have flushed the stock and not selling them anymore. Either way, I hope you're reading this not because you got fooled too but because you're cautiously double-checking online shops or testing samples.