How to identify a counterfeit component - Page 1
Forum section: electronics / beginners

author: HansGruber
author_rank: Contributor
timestamp: September 13, 2022, 07:15:36 am
content: I am having some issues with a motor control PCB recently, so I grabbed a old working motor controller and started looking at each component and comparing them. I am not sure with one MOSFET I found, they are both supposed to be onsemi FDMS86540 N-Channel MOSFETs:https://www.onsemi.com/pdf/datasheet/fdms86540-d.pdf. I can't find the manufacturers description of the original markings on the package, maybe someone has a idea ?They are both 5mm wide but one is 6mm long and the other one is 5.5mm long (without pins). Is this just a production variance from a old batch or is this really what I expect it to be. Is there a way to measure this in-circut or maybe after desoldering them ?

author: magic
author_rank: Super Contributor
timestamp: September 13, 2022, 08:22:26 am
content: Your datasheet says 6mm and an older one from Fairchild says 6mm too, and your part must be newer than that because it has the ON logo.https://html.alldatasheet.com/html-pdf/475048/FAIRCHILD/FDMS86540/2958/6/FDMS86540.htmlNot sure why there is no F in the part number and DMS86540 doesn't seem to exist.Did anyone work on this board before?

author: HansGruber
author_rank: Contributor
timestamp: September 13, 2022, 08:39:31 am
content: You can't see the F because of my low quality picture, it's hard to take one with all the conformal coating, I made another picture where you can see it a little bit more. I just remove a little bit of the conformal coating, otherwise it's not been worked on. I would have assumed that the right component on the picture of my first post is the original component (because it's working). But that's actually the one that's 5.5mm long.The onsemi logo on the right component looks better to me, also the general alignment of the marking font, the left one looks a little crooked and the onsemi logo does not seem so... crisp ? It's just a feeling and hard to proof.

author: HansGruber
author_rank: Contributor
timestamp: September 13, 2022, 09:17:16 am
content: I found a dimension that I can measure more clearly, it's from the most recent datasheet. It's supposed to be the "height" of the component. I can measure the same at the right component (~5.6mm) of my first post, the left one is ~6mm.EDIT: I wrote a E-Mail to onsemi, I wonder how my chances are for a real answer.

author: strawberry
author_rank: Super Contributor
timestamp: September 13, 2022, 03:59:25 pm
content: measure DS on resistance with miliohm meter. it must be less than datasheet value at room temperaturedont know how to cheat on resistance to get smaller diegate capacitance. smaller die will give less capacitance

author: HansGruber
author_rank: Contributor
timestamp: September 14, 2022, 07:23:45 am
content: Just as a general question: how likely is it that the manufacturer will change the package size with the markings on it ? I've collected several boards from the past months and years (see attachment). The images are a little distorted because of different microscope zoom and resizing the image etc.But everything in the past looked similar, except for the "new" batch. Sadly I realized I don't have the equipment to measure it.

author: Haenk
author_rank: Super Contributor
timestamp: September 14, 2022, 07:30:40 am
content: The 6 month old part looks coated, I'd suggest trying to use some solvent to rub it away - if the black color does come off, it's coated and likely fake.

author: magic
author_rank: Super Contributor
timestamp: September 14, 2022, 08:10:26 am
content: Quote from: HansGruber on September 13, 2022, 08:39:31 amSo we can assume that the board contains exactly the components that have been placed on it by the manufacturer. Question arises: who made this board and where did they get these transistors from?Did you order the board from China?Could the manufacturer source components from dodgy vendors in China?Quote from: HansGruber on September 13, 2022, 08:39:31 amIf the logo or markings are rotated and not exactly horizontal (hard to tell from the pictures, but maybe you are right about the newest one) then yes, it's a common thing on fake parts and it generally doesn't happen on quality parts.

author: HansGruber
author_rank: Contributor
timestamp: September 14, 2022, 08:23:23 am
content: Quote from: Haenk on September 14, 2022, 07:30:40 amI would assume that's just the silicon based conformal coating. It's a little unfortunate that they are all mixed of different conformal coatings (or none), makes it hard to compare them. My main argument was just the general marking, which looks similar on all except the new one.Quote from: magic on September 14, 2022, 08:10:26 amI think our electronics manufacturer could not get it from a reliable source and just ordered something in China. Onsemi actually answered me, they want a picture of the sticker with the LOT-number. I hope they still have the roll somewhere, maybe it's traceable.

author: wraper
author_rank: Unknown
timestamp: September 14, 2022, 08:26:10 am
content: Quote from: HansGruber on September 14, 2022, 07:23:45 amOften they don't change anything. Just produce the same part at factories in different parts of the world, and then they have some significant differences in package and marking. Sometimes differences are shown in the datasheet, but usually not.

author: mikerj
author_rank: Super Contributor
timestamp: September 14, 2022, 08:28:57 am
content: Quote from: magic on September 13, 2022, 08:22:26 amNote that the OP said 6mmwithoutpins. The datasheet gives a dimension of 5.65-5.85mm for the body, so neither 5.5mm or 6mm is in tolerance. OP, did you use some precision measurement such as vernier calipers to get these dimensions?

author: wraper
author_rank: Unknown
timestamp: September 14, 2022, 08:32:27 am
content: I would remove transistor from PCB, then first measure RDS(on), if it's fine then also drain-source voltage. Maybe compare gate capacitance measurement with a known good part (or meet all measurement conditions and compare it with datasheet). Fake power transistors are rarely up to spec and usually have a much smaller die.

author: HansGruber
author_rank: Contributor
timestamp: September 14, 2022, 08:39:05 am
content: Quote from: mikerj on September 14, 2022, 08:28:57 amI am just bad at measuring, I've attached my new measurement. Maybe it's clearer now.

author: strawberry
author_rank: Super Contributor
timestamp: September 14, 2022, 09:01:30 am
content: that new PCB is counterfeit 100%poorer quality PCB (made in China)vias and traces dont matchand all other parts dont match eitherif they were honest they put similar spec transistor (made in China) with fake ON semi markings ...

author: mikerj
author_rank: Super Contributor
timestamp: September 14, 2022, 02:30:02 pm
content: Quote from: HansGruber on September 14, 2022, 08:39:05 amIt's clear the newer MOSFET is unlikely to be a genuine part!

author: wraper
author_rank: Unknown
timestamp: September 14, 2022, 06:42:06 pm
content: I think it's actually a different package. Old one is PQFN8 5X6, new one should be similar to DFN 5X6E (ALPHA & OMEGA semi)http://www.aosmd.com/res/data_sheets/AOE6930.pdfwhich has no protruding terminals. But Infenion makes both type and calls both with the same name ThinPAK 5x6 SMD although they are obviously different.With protruding terminalshttps://www.farnell.com/datasheets/3629119.pdfWithout themhttps://docs.rs-online.com/f5c7/A700000007497990.pdf

author: wraper
author_rank: Unknown
timestamp: September 14, 2022, 07:05:35 pm
content: Actually ON also uses both packages and calls both PQFN8 5X6, 1.27Phttps://www.onsemi.com/pub/Collateral/483AE.PDFhttps://www.onsemi.com/pub/Collateral/483AF.PDFAlthough more specifically one is CASE 483AE, another is CASE 483AF. However the datasheet you provided says specifically PQFN8 5X6, 1.27P 483AE in the drawing. But in ordering information ON datasheets just says PQFN8 5X6, 1.27P. IMHO the right question you should ask manufacturer is if particular transistor may come in anything other than CASE 483AE.From this there are at least 10 variants of this packagehttps://www.onsemi.com/pub/collateral/brd8011-d.pdf

author: HansGruber
author_rank: Contributor
timestamp: September 15, 2022, 08:58:16 am
content: The most recent (May 2015) datasheet (from the official onsemi website) states that the used case is 483AE, like wraper said. Based on the reel sticker of our components, the MOSFETs were produced week 42 in 2020 (so they had 2 years to refresh the datasheet). I am in contact with onsemi, if the reel itself is genuine. If the reel is genuine, I will ask them about the different case, if it's possibly a different one.

author: HansGruber
author_rank: Contributor
timestamp: September 16, 2022, 03:20:43 pm
content: Waiting for the answer of onsemi made me bored, so I made a poor man's die analysis, I hit it with a hammer and chisel toprofessionallyremove the package. Except for the package, I also remove the copper "hat" that was sitting on top to connect the lower source/gate pins. The "new" part got a unlucky hit to the top right, it would normally look different. Overall it looks different to me, but I am really no expert.I did it to 3 different ones, just to be sure they don't look different purely because I hit one harder than the other one.EDIT: onsemi just confirmed it's fake, the LOT number does not exist

author: magic
author_rank: Super Contributor
timestamp: September 16, 2022, 05:09:16 pm
content: This is the professional wayhttps://www.richis-lab.de/Howto_Decap.htmhttps://www.richis-lab.de/Howto_Decap_Ofen.htmBTW, no fancy gas torch is strictly required - even a lighter may work.A bunch of fake IRF3708 from that guy:https://www.richis-lab.de/Transistoren_FET_pwr.htm

author: strawberry
author_rank: Super Contributor
timestamp: September 16, 2022, 08:38:51 pm
content: 22 ohm resistornew 5% old 1% even not necessary precision thereit s clear that board was made to be close to original (and work for 1 month to not receive refund) for some dumbass to not notice any difference and think he got lifetime dealeven original may hide some design flaw but this new board may not be even as goodless via count less current capability

author: wraper
author_rank: Unknown
timestamp: September 16, 2022, 08:43:47 pm
content: Quote from: strawberry on September 16, 2022, 08:38:51 pmDo you net get it's their own board? They had a problem with counterfeit components.

author: strawberry
author_rank: Super Contributor
timestamp: September 16, 2022, 09:33:01 pm
content: they didnt stole it , right?