Buy from this Ali Express seller at your own risk

Thread Starter

dl324

Joined Mar 30, 2015
11,530
All Electronics Trading company.
https://www.aliexpress.com/item/1972789887.html?spm=a2g0s.issue_5ptha.0.0.5e1f4c4dhZmpWO

I bought some level shifters that use an N channel MOSFET and this is how they packaged them:
levelShifterPlasticPackaging.jpg

When I asked for a refund, they asked me if I tested them. I refused and they stopped responding, so I filed a dispute and AE issued a refund in a day. I expected them to make me jump through hoops like they've done in the past and then reject my request.
 

ericgibbs

Joined Jan 29, 2010
10,809
hi dl234,
Why are you concerned about the packing, most shifters of that type I have bought from other suppliers, have been packed that way and they all work OK when assembled.
E
 

Thread Starter

dl324

Joined Mar 30, 2015
11,530
Why are you concerned about the packing, most shifters of that type I have bought from other suppliers, have been packed that way and they all work OK when assembled.
N channel MOSFETs are static sensitive devices. If they're subjected to an ESD event, they'll die outright if you're lucky. If you're unlucky, they'll exhibit increased leakage and/or die prematurely. It's not worth adding that uncertainty to any circuit.

If they're packaged improperly, you'd probably be correct in assuming that they were handled improperly. It's just not worth the bother.

I have never had that level shifter shipped to me in packaging that wasn't antistatic.
EDIT: From any other seller.
 
Last edited:

ericgibbs

Joined Jan 29, 2010
10,809
hi,
This image is the circuit for the shifters I buy.

You can buy either 3 or more shifters on a PCB.

Sometimes I connect a TO92 TS2951 3.3V regulator laid flat across the top of the shifter PCB, using the onboard pads for 5Vin and 3.3Vout to TS2950.
This is useful when you need a low current 3v3 supply for other devices on the project.

E
 

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tindel

Joined Sep 16, 2012
730
N channel MOSFETs are static sensitive devices. If they're subjected to an ESD event, they'll die outright if you're lucky. If you're unlucky, they'll exhibit increased leakage and/or die prematurely. It's not worth adding that uncertainty to any circuit.

If they're packaged improperly, you'd probably be correct in assuming that they were handled improperly. It's just not worth the bother.

I have never had that level shifter shipped to me in packaging that wasn't antistatic.
EDIT: From any other seller.
If you're that worried about it you should also not be buying from Ali Express. :rolleyes:
 

Thread Starter

dl324

Joined Mar 30, 2015
11,530
Is there a 10k resistor from Gate to Source?
Yes, but I reasoned that the plastic bag could accumulate different potentials on it's surface and be able to apply enough a differential voltage across the resistor that's high enough to damage the gate oxide or to apply sufficient voltage across the source-drain to break it down. For BSS138, it only takes 40-50V.
 

Thread Starter

dl324

Joined Mar 30, 2015
11,530
This image is the circuit for the shifters I buy.
Maximum gate to source voltage for those MOSFETs is 20V. Some datasheets specify a short pulse of 40V. 50V is enough to damage or kill those devices and being in a plastic bag can expose the devices to that, and more.
 

Thread Starter

dl324

Joined Mar 30, 2015
11,530
If you're that worried about it you should also not be buying from Ali Express. :rolleyes:
I won't pay the prices the likes of Sparkfun charge for them.

I've bought them from several Sellers and they're the only ones to not package properly.
 

Wolframore

Joined Jan 21, 2019
1,796
I’ve had failed MOSFETs from AliExpress which were packaged like that or just thrown in one baggie. I wonder if the ones that are not packaged correctly are the rejected ones just grabbed from a scrap bin.
 

Thread Starter

dl324

Joined Mar 30, 2015
11,530
I wonder if the ones that are not packaged correctly are the rejected ones just grabbed from a scrap bin.
It's hard to say. Selling a lot of known defective/counterfeit product would seem to be a poor business model unless they count on buyers being clueless, not complaining about improper packaging, and not discovering that parts are defective until the buyer assurance period has expired. My experience has been that most sellers at Ali Express don't know much about the products they sell.
 

Wolframore

Joined Jan 21, 2019
1,796
Thats why I wonder, if they were in anti static reel type packaging it would be less work to just cut the reel and bag them rather than peel them out and bag. Until recently they were paying subsidized postage. That’s why you might see a $1.50 purchase with $0.05 in postage all the way from somewhere in China.
 

Thread Starter

dl324

Joined Mar 30, 2015
11,530
Thats why I wonder, if they were in anti static reel type packaging it would be less work to just cut the reel and bag them rather than peel them out and bag.
It's unlikely that they would have packaged the finished boards in antistatic reels. They probably just put the assembled shifters in bulk antistatic packaging and the entity that buys them is responsible for packaging in smaller quantity. That can be done in an ESD safe manner, but anything repackaged improperly makes you wonder how they were handled.

I plan to test some of the parts when I have nothing better to do.
 

Wolframore

Joined Jan 21, 2019
1,796
We were talking about similar situations. I received unsoldred SMD mosfets 50 in a plastic bag. These were nice mosfets at one point.
B12AE597-A0B1-4388-8098-5E0C37F3377C.jpeg
The gate is exposed on your board so I would be concerned about ESD.
2CDAB496-7388-40B1-B507-3C4EF503831C.jpeg
 

Thread Starter

dl324

Joined Mar 30, 2015
11,530
We were talking about similar situations. I received unsoldred SMD mosfets 50 in a plastic bag.
If the seller won't give a refund, submit a dispute if they stop responding. Ali Express was fast for the dispute this time; issuing a refund in a day. My past experience was that they'd side with the seller and deny the dispute.

The gate is exposed on your board so I would be concerned about ESD.
I reasoned that the plastic bags could develop different potentials along the surface and that it would be possible to apply 50V+ across the gate to S/D or across the source and drain. Either situation could damage the devices while they're still in the bag.

You could also damage them while removing them from the bag.
 

rsjsouza

Joined Apr 21, 2014
262
I won't pay the prices the likes of Sparkfun charge for them.

I've bought them from several Sellers and they're the only ones to not package properly.
Yes, but you are never sure how they were handled before packaging.

This is a common problem of anti-static packaging: it tends to give you a false sense of safety but, if the entire process is not static-safe, the last line of defense (the packaging itself) cannot help with prior damage.

I have seen multiple occasions where parts were bagged in nice anti-static bags but had paper labels or scotch tape inside them, which are prime for building up static. In older days, I also have seen many people count CD4000 or MOSFETs with bare hands and then put them on shiny bags.

Oh well... For hobby purposes this usually does not go beyond a nuisance but, if that is important to you, then I echo the comment to buy from reputable sources. You can never tell if a retail vendor such as Aliexpress will side with you or the seller.
 

Thread Starter

dl324

Joined Mar 30, 2015
11,530
Yes, but you are never sure how they were handled before packaging.
That's true, but there isn't much you can do about it.

I've bought parts from Newark that weren't handled properly. They had low quantity of a part that I ordered and they could only ship around 20 of the 25 parts I ordered. The first shipment had parts in 3 cut down tubes and about a quarter of them had mangled pins. The mangled parts weren't always on the ends of the tubes, so it wasn't shipping damage.
 
I've bought from All Electronics Trading company on Aliexpress, and the parts were in anti-static cut-tape. Slow 16 weeks shipping.
I've bought from Shenzen IC store on Aliexpress, and none of the parts (TO-92 JFETS) were in anti-static bags. Kind of like OP's.

But the level-shifter 10k resistor does dissipate G-S static charge, so I would not be as upset if it was a plain MOSFET. I never use BSS138 or 2N7002 as they are super fragile with ESD. Instead I use BSS138K or 2N7002K that have built-in gate zener. It's the gate that is very fragile.
 
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