Pics, measurements and experiences of fake ICs - Page 1
Forum section: electronics / projects

author: Phil1977
author_rank: Frequent Contributor
timestamp: September 14, 2024, 07:49:39 am
content: Hi,the last post about getting stuff from AliExpress started a discussion about recognizing fake ICs. I think this is too complicated and too important to be forgotten in the spin-off of another thread, so let´s start it here.It'd be very interesting to collect the experiences you made with grey-market semiconductors. Please only post real own experiences, nothing like "I have heard" or "in Youtube they show"...I propose to give each reported component an own post so it´s easier to relate the replies.I start with the LMC662 I bought at AliExpress in the beginning of 24: Got 25pcs for around €3,- + shipping. Delivery was in non-conductive foam plastic. Electrically they look okay, 1.8V/us slew rate, 26mA short circuit current at 5V, 0.6mA quiescent current, bias current <0.1pA.I´m confused by the housing - see the pics:Indications it´s faked / salvaged e-waste:- Not very precisely printed label- slightly bent pinsIndications it´s authentic:- Non-solvable ink- No directly visible sanding marks. In the last thread it was mentioned they look sanded, but inspecting the edges in detail reveals from my point of view no clear indication for sanding. I assume if the package gets sanded then the surface in the indentations should look different than on top - and here its looking very similar:- Good electrical behaviour

author: Phil1977
author_rank: Frequent Contributor
timestamp: September 14, 2024, 07:54:09 am
content: To also give a bad example, this is an Analog Devices AD620AN that I got for a too good to be true price.It was electrically a complete shortcut, I even thought about opening it up to see if there is any silicon inside.Here you can easily spot the sanded or even grind surface and the fake looking laser marking.

author: Phil1977
author_rank: Frequent Contributor
timestamp: September 14, 2024, 08:02:34 am
content: Another example of a bad part: A TL072 with a pristine package but a suspicious TI-Logo. Needless to say it behaves like one of the first opamps of the world. Bought at Aliexpress for around €2.- for 10pcs. Money was reimbursed after uploading slew rate measurements - but no one pays me back the hour in the lab that takes.

author: magic
author_rank: Super Contributor
timestamp: September 14, 2024, 08:24:14 am
content: I have heard something about fake opamps in some forum post,hereYour "mermaid" TL072 is almost certainly a Chinese LM358 clone.I have some legit LMC662 and IIRC the package is supposed to look like that. As for markings, their exact position and paint (or laser) may have changed over the years. It may still be recycled, and it may be a different recycled part with fake markings, I have seen such things. Sometimes they also "upgrade" to a better precision or temperature bin or simply "refresh" a batch of e-waste parts to look like they are factory new from the same lot (I got a batch of NE5534 which were like that - a mix of various revisions of the TI die inside). But going by the package shape, yours would still likely be some National part.LMC662 is known for having very low input leakage, the 2fA typical spec is typically met for real. You canmeasure itif you have a gigaohm+ resistor.One trick is to measure the package's thickness with calipers. They usually get thinner when the top is sanded to remove original markings.editThere seems to be some solder on its pins, so it's probably recycled. If the pins are unusually soft and fragile, that's another sign. I think they are overheating them in the process. Yet another sign is when you get a lot with different date codes on each chip. Or if they are the same - then it means the markings are fake

author: RoGeorge
author_rank: Super Contributor
timestamp: September 15, 2024, 08:43:10 am
content: Can't say I've found any IC fakes so far, but I don't buy much from untraceable vendors.One can never be sure if it's a fake by simply looking at the exterior package. To be sure you'll have to open the chip, and compare the die pics with the original.To verify the LMC662 in particular (without opening the chip) would be easy, because LMC662 is an opamp with one of the tiniest bias currents ever, of only a couple of fA. Take an 8 pins DIL socket and improvise an electrometer, like this:That's a funny experiment to do anyway. Use the electrometer as described inhttps://www.eevblog.com/forum/projects/opamps-die-pictures/msg4599961/#msg4599961, and the air capacitor should keep the voltage for a very long time.Grease from the fingerprints, or even the socket itself may add significant leakage. To minimize the socket leakage you can lift/bend the input pin of the IC, and leave it outside of the DIL socket, as suggested in the datasheet. Avoid adding any flux when soldering the socket. Against fingerprints, preferably use rubber gloves. If already handled the chip with the bare hands, brush the LMC662 with normal soap and water.

author: Phil1977
author_rank: Frequent Contributor
timestamp: September 15, 2024, 09:13:06 am
content: I´ve bought the LMC662 for a similar purpose (Teraohmmeter) - they behave very good regarding its bias current. With the air electrometer circuit I could proof the bias current to be <100fA - that clearly is okay for the application.As already mentioned in the other thread: I also have a few LMC662 from digikey, they have another type of labelling but measurements of output current, quiescent current and slew rate are more or less the same.In that case I even think it´s of no use to decap it and look at the die. The AliExpress-types may be salvaged from e-waste or they may be a 1:1 clone of the TI-/NationalSemi design.

author: wobbly
author_rank: Regular Contributor
timestamp: September 15, 2024, 09:38:33 am
content: I've had fake high voltage caps. Supposed to be 250V rated but most of them failed at just 50 or 100! Our board assembler had bought them from some dodgy reseller with an eBay storeWe demanded they send us the batch number, and we then contacted TDK who confirmed that it wasn't a valid batch ID.I've also had bad FPGAs (Intel Cyclone) which all have inoperable JTAG ports or shorted power rails, making them completely unusable. Those were bought from a supposedly reputable broker. I suspect they are simply counterfeit or perhaps recycled from broken products.

author: wraper
author_rank: Unknown
timestamp: September 15, 2024, 10:33:28 am
content: Genuine on top. One on the bottom is relabeled incompatible Toshiba IC of the same purpose (will cause magic smoke if used). Why they did it is beyond my comprehension as both of them cost about the same. Was bought on ebay for the same price as original IC before that (IIRC about half of digikey price at qty of 1).

author: guenthert
author_rank: Frequent Contributor
timestamp: September 15, 2024, 11:10:15 am
content: Quote from: wraper on September 15, 2024, 10:33:28 amSounds like a SNAFU at factory. Surely this was detected and the bad chips were meant to be destroyed. I'd wager, some employee took them out of the recycling bin and put them on the secondary market (quite possibly unaware of why they were in the recycling bin in the first place). While the employees are clearly instructed not to do such, that is probably not well monitored.

author: wraper
author_rank: Unknown
timestamp: September 15, 2024, 11:25:32 am
content: Quote from: guenthert on September 15, 2024, 11:10:15 amTerminals are a tiny bit shorter and their surface looks suspicious. I'm 99% positive it's salvaged from e-waste and relabeled as different IC. I don't believe a tiny bit that factory fucked up in such way.