Buy from these Ali Express/Amazon sellers at your own risk

Hamlet

Joined Jun 10, 2015
519
Haven't US fabs been creating "homage" parts for decades? These parts are not "original"
or "genuine". Yet, they are still functionally identical or similar. Also, US fabs have sister
fabs in China, that make bread & butter parts, for which there is no other source.

Fake would imply a part that is marked as one thing, but inside is completely different, or empty,
making them useless. Another type of fake part would be something that has functions
that are close to the original to avoid easy detection. And yet another would be rejects,
that failed for temperature, current, hfe, etc., yet sold as top tier parts.

Here's a link to the datasheets for the LM317; as can be seen, there are dozens of manufactures
for this one part alone:
https://www.alldatasheet.com/view.jsp?Searchword=Lm317
 

SamR

Joined Mar 19, 2019
5,031
Fake would imply a part that is marked as one thing, but inside is completely different,
In fact, some are. They shave the top of the chip w/ the laser etched markings off and mark them as similar more expensive parts to sell at a premium price. Or take a "generic" manufactured part and stamp them with a reliable company's logo and model number. Unless you have research grade test equipment to do a full parameter analysis, they may work but not to specifications for the real deal. Some I have received are DOA. Makes me wonder if they are buying scrap failed quality chips from dealers and selling them as the real deal. In other words, Don't Trust Them! They have no qualms about lying and cheating, much less false advertising.
 

Hamlet

Joined Jun 10, 2015
519
I now see where you can buy "pulls" from chinese outlets. Presumably, scrap ewaste from the US/Euro sails over, and a chinese kid chews off the parts, that are then rinsed off (optional) and sold to wary 1st world shoppers who don't trust their shiny new stuff.

How long before they start faking "pulls" from new/defective parts? Splash a little solder on them, then nib the legs shorter, and vola! Brand new fake old pulls!
 

SamR

Joined Mar 19, 2019
5,031
They have all kinds of tricks. Years ago, a buddy from Hong Kong told me about a tongue in cheek article in the HK Times announcing that China had learned how to counterfeit chicken eggs and to be wary of any eggs bought at the market now being counterfeit.
 

Thread Starter

dl324

Joined Mar 30, 2015
16,846
I now see where you can buy "pulls" from chinese outlets.
China has many companies who specialize in counterfeit product. Some of it is from manufacturers who make products for legitimate companies and decided to compete with their customers. Other counterfeiting is done by bounty hunters who are supposed to be tracking down counterfeits for legitimate companies. One guy who was working as a bounty hunter was setting up factories to manufacture counterfeit product that he'd turn over for the bounty.
 

Hamlet

Joined Jun 10, 2015
519
China has many companies who specialize in counterfeit product. Some of it is from manufacturers who make products for legitimate companies and decided to compete with their customers. Other counterfeiting is done by bounty hunters who are supposed to be tracking down counterfeits for legitimate companies. One guy who was working as a bounty hunter was setting up factories to manufacture counterfeit product that he'd turn over for the bounty.
Gwad Dam, I lurv capitalizem!
 

ag-123

Joined Apr 28, 2017
276
I'd think ESD would need to be quite severe to cause damage, it probably happens in certain circumstances.
I'd just test them and if they work make do, don't think it is so easy to damage those transistors.

for 3.3v to 5v level shifters, these days I'd prefer the 74hctxxx series e.g. 74hct245
https://www.aliexpress.com/wholesale?catId=0&SearchText=74hct245
they are very fast (it can switch at Mhz speeds), performs very well and are low cost and readily available
as those are stocked in large volumes by the chip stockists.
those 74hctxxx chips has built-in ESD protection in the chip design, so u'd have one less worry about ESD
note that the hc(T) the T series is needed for 3.3v - 5v shifting, whose without the T won't do.

Incidentally 74hctxxx are my preferred 5v logic level mostet drivers, very low cost compared to literal mosfet gate drivers
and is high performance fast switching speeds, each time every time, and they can drive the gates of high power mosfets running in the 10s of amps.
only thing would be it needs to be 5v logic level mosfets.
 
Last edited:

Thread Starter

dl324

Joined Mar 30, 2015
16,846
I'd think ESD would need to be quite severe to cause damage, it probably happens in certain circumstances.
I'd just test them and if they work make do, don't think it is so easy to damage those transistors.
As I think I've said before. If you're lucky, the devices die outright. If you're unlucky, an ESD event will allow the device to appear to function normally before failing prematurely.

Some MOSFETs are quite easily damaged. The BSS138 used in the level shifters I bought only take 20V to damage the gate oxide. Even with 10k resistors pull ups, plastic packaging could potentially create sufficient voltage to damage the gate oxide. A plastic bag could easily generate the 50V necessary to damage the source/drain.

Incidentally 74hctxxx are my preferred 5v logic level mostet drivers, very low cost compared to literal mosfet gate drivers
and is high performance fast switching speeds
The level shifters I referenced aren't for high speeds.
 

Wolframore

Joined Jan 21, 2019
2,609
The worst are damaged devices which still function (latent failure). Here are some microscopic images of ESD damage

This one looks catastrophic
1644020666513.png

This looks like latent failure, which will work until it gets stressed from current or temp.
1644021150320.png
 

Thread Starter

dl324

Joined Mar 30, 2015
16,846
The worst are damaged devices which still function (latent failure).
Exactly.

Were these all from ICs that had "ESD protection"? Or bare devices? Bare devices are especially susceptible to ESD events because most MOSFETs don't have any gate protection.

I have some NTA4151P P channel MOSFETs that have a protection network on the gate, that can only tolerate 6V, but there's only the parasitic diode to protect the source-drain.
1644022453517.png
 

k1ng 1337

Joined Sep 11, 2020
940
If professionals such as yourselves are having big trouble getting authentic parts I'm starting to think it's impossible to get good parts for us toddlers.

When I bought my first logic level MOSFET
listed as IRL44ZN from the local hobby shop. I busted out the flashlight and identified it was IRF44ZN and returned it for my money back for which I had to argue with the rep who took it to his boss who both said I was wrong. They made me feel like the dummy but still gave me my money back. Since then I've identified a handful of mislabeled parts from their shop.
 

Thread Starter

dl324

Joined Mar 30, 2015
16,846
If professionals such as yourselves are having big trouble getting authentic parts I'm starting to think it's impossible to get good parts for us toddlers.
I started this thread about some assembled level shifters. I bought them because $0.30 each was more in my price range than the $3.00 the likes of Sparkfun charge and I considered it worth the risk. What I wouldn't accept was getting something that was obviously mishandled. If they had packaged them properly, I would have tested a couple. If they worked, I would have set the rest aside until I needed them. If any didn't work, I would have had to do 100% testing so I'd know how much of a refund to ask for. I didn't even bother to test any from the problematic lot because ESD damage doesn't always produce an outright failure.

I buy few semiconductors from AE that aren't installed on something. I took a risk on some AO3400 and AO3401 because I wanted some logic level MOSFETs that cost a couple cents each. I had good luck with a few lots of 100, but I only tested for threshold voltage and 1A drain current (they're supposed to handle 3A+, but 1A was more than sufficient for everything I had in mind). I thought about buying full reels, since these parts are EOL, then I reminded myself it wasn't worth the risk.
 

SamR

Joined Mar 19, 2019
5,031
There is a world of difference in how their vendors package DIPs for shipping. Only ~1 in 15-20 will actually put them on non-ESD foam. I've seen them just dumped in the envelope and arrived with all the pins bent or broken but did dispute it and got a refund. Some will dump them in small plastic (NOT non-ESD) bags, and some will stack the chips and put a bit of bubble wrap around them. And I always build a test circuit for basic go/no-go test before I store them. Anything I am working on and not just using as a learning exercise, I buy from Arrow or DigiKey or any reputable US dealer.
 

Thread Starter

dl324

Joined Mar 30, 2015
16,846
I buy most of my semiconductors from Jameco, Newark, Mouser, or Tayda. Even Newark isn't immune to having incompetent pullers/packers. I got some IC's in cut tubes that had pins mangled enough that I complained and got a credit (it was an item they had on clearance and were discontinuing to carry). I could straighten the pins, but it was the principle of them sending me damaged product that made me complain. They probably lost money on that transaction because it was less than 25 parts that they shipped in 3 installments and they gave me credit for half a dozen of them.

Ali Express does have some decent ratcheting crimpers and I've bought several for significantly less than what distributors would charge. I finally found an "automatic" wire stripper that actually works. But I'm working on a 1000' spool of #22 insulated, tinned solid wire that I got from Circuit Specialists on clearance with free shipping that the insulation comes off easily; too easily in fact. So it isn't much of a chore with regular wire strippers.
 

DickCappels

Joined Aug 21, 2008
10,152
One online vendor which I now refuse to even visit sent me the wrong microcontrollers -they substituted a 4K of flash part for a 2K of flash part. When developing the product you don't develop on one version then switch to another without a lot of testing. To make it worse, they were plugged into plain Styrofoam. The icing on the cake was that I had paid a huge expedite so I could have them with me for the three months I was going to be in a different country -yeah the parts arrived long after my plane left.

Over the past 20 years they have accepted orders they never filled, accepted orders for "in stock" parts that were not, shipped components with prepped leads corroded (un-solderable) leads, parts that did not match the pin-out on their site and were incompatible with what I was designing. One shipment was so bad that I dumped the whole thing in the trash.
 

DickCappels

Joined Aug 21, 2008
10,152
I can't name them. I live a country where saying anything bad about anybody or any company can swiftly get on in jail waiting for the lawsuit to start, and they have a warehouse in this country.

It has been about three years since I tried to buy anything from them. I was trying to get a part that I needed for a client's application and they jerked me around for over a month and I finally ordered the parts from directly from the manufacturer -at a lower price! They are not all bad news. For one project they recommended an excellent PCB engineer and a manufacturer for our product.

I cannot imagine circumstances under which I would order parts from them again.
 

SamR

Joined Mar 19, 2019
5,031
We fuss about AliX but I was telling my wife today about a couple of other chinese vendors that make AliX shine like a gem. I also buy tea from china and I have learned that most of the tea vendors are far more disreputable than the ones on AliX selling electronic parts. No qualms whatsoever about false advertising. Not wrapping packages for international shipping and sending broken damaged wrapped for sale packages. I bought some green tea for my wife that arrived looking like floor sweepings it had so much dust and dirt in it. Buying tea from china is not for the faint at heart there is so much chicanery in that market.
 

ag-123

Joined Apr 28, 2017
276
We fuss about AliX but I was telling my wife today about a couple of other chinese vendors that make AliX shine like a gem. I also buy tea from china and I have learned that most of the tea vendors are far more disreputable than the ones on AliX selling electronic parts. No qualms whatsoever about false advertising. Not wrapping packages for international shipping and sending broken damaged wrapped for sale packages. I bought some green tea for my wife that arrived looking like floor sweepings it had so much dust and dirt in it. Buying tea from china is not for the faint at heart there is so much chicanery in that market.
If even electronics parts some of which has rigorous specs can be fakes, tea would be much harder to tell in particular its grades. u'd not be able to tell if that tea is a dollar per pound leaves or that they are premium auctioned stuff where they sell it to the highest bidder.
 
Top