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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 14th Apr 2024, 11:16 am   #1
John_BS
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Default Fake semicoductors and keeping abreast with progress!

Whilst reading Craig's post on low distortion oscillators*, I searched for the data-sheet for the opamps used ( LME 49710). I then happened upon this interesting site, where the owner opens devices and compares the die with genuine samples:

https://www.tinytransistors.net/2022...fake-lme49710/

Another of the chips he looks at is a MEMS device, something I'd never heard of, but for anyone else intrigued by micro-technology, here's an article describing MEMS (albeit with a sales / marketing slant).


* https://www.vintage-radio.net/forum/...eferrerid=9910
Attached Files
File Type: pdf MEM resonators.pdf (1.22 MB, 47 views)
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Old 14th Apr 2024, 2:16 pm   #2
kalee20
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Default Re: Fake semicoductors and keeping abreast with progress!

That's good detective work in the link!

Any decent counterfeiter would use something which is both dead cheap, and works. The 741 chip satisfies both of these, although as pointed out, not to the extent of the fast slew rate of the original device. Still, fingers crossed, that might not be noticed in a Production test.

Wire-bonding quality might be inferior; plastic encapsulation likewise, with lower-spec resin that perhaps has a bigger coefficient of thermal expansion. But again, unless one of the counterfeit devices is used in a design-proving or qualification-type test, it probably won't be noticed till maybe a few years down the line - by which time the counterfeiter will have long-gone scarpered.

There's a lot 'out there' and the hi-rel industry is very cautious about supply chain!
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Old 14th Apr 2024, 6:18 pm   #3
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Default Re: Fake semicoductors and keeping abreast with progress!

Something new about MEMS arose a few years ago.

Someone's iphone stopped working. Back at work, the owner mentioned it to a colleague and was told hey, so-and-so's has doen that too along with comments on their quality and reliability. It was later found that a lot of iphones had died... all belonging to people working in the same hospital. In this way it was discovered that there was a significant helium leak from their MRI system where it was used to cool superconducting magnets. Helium is a small enough molecule to diffuse through a lot of materials and it had diffused into the MEMS device packaging, spoiling the vacuum and affecting the tuning.

I'm working on old memory of reading of the event, but I think that's the gist of it.

David
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Old 15th Apr 2024, 1:21 pm   #4
Chrispy57
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Default Re: Fake semicoductors and keeping abreast with progress!

Hi David - the "old memory" seems to be pretty accurate, here is a link to an article on the subject

https://hothardware.com/news/apple-i...um-leak-update

I wonder if the hospital staff also started sounding like Donald Duck for the duration of the helium leak!

Cheers
Chris
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Old 15th Apr 2024, 3:26 pm   #5
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Default Re: Fake semicoductors and keeping abreast with progress!

Hello,

I had to check a sample quality of a very low noise Toshiba 2SK170 N-Type FET transistor with a very low Noise figure and a defined IDSS range.

Markings looked fine and it was supposed to have come via a traceable source.

They were fitted to the unit and ‘yes’, they were a N-Type FET, however the noise was substantially higher, and the operating conditions indicated the IDSS classification was out of the range of the IDSS classification marked on the device.

Much like the LME 49710 in the OP, it was a working N-Type FET, but it appeared to be what I’d call a general-purpose N-Type FET with comparable voltage and current ratings.

Also, a year or so ago I bought on line one of those class D amplifier modules using a TPA3118 for a development hook-up unit… The IC was marked as TI TPA3118… However, the rub was…, this IC had 28 pins whereas the TI data sheet states the TPA3118 as being a 32-pin device… I smelt a rat (or lack of pins!) and put it in the ‘tat’ box, and didn’t bother using it, and found something legit (from TI) with 32 pins!

Terry.
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Old 15th Apr 2024, 8:29 pm   #6
Craig Sawyers
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Default Re: Fake semicoductors and keeping abreast with progress!

Quote:
Originally Posted by Chrispy57 View Post
Hi David - the "old memory" seems to be pretty accurate, here is a link to an article on the subject

https://hothardware.com/news/apple-i...um-leak-update

I wonder if the hospital staff also started sounding like Donald Duck for the duration of the helium leak!

Cheers
Chris
The problem with helium gas is that it fills a lab with a major leak from the ceiling down (being a lot less dense than air). Problem is you get no indication that anything is wrong, until you asphyxiate. You also get no indications at all that this is happening - no gasping, no urge to open the door. It is not nice stuff at all.

Craig
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Old 15th Apr 2024, 10:24 pm   #7
kalee20
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Default Re: Fake semicoductors and keeping abreast with progress!

Quote:
Originally Posted by Valvepower View Post
I had to check a sample quality of a very low noise Toshiba 2SK170 N-Type FET transistor with a very low Noise figure and a defined IDSS range.

Markings looked fine and it was supposed to have come via a traceable source.

...

it was a working N-Type FET, but it appeared to be what I’d call a general-purpose N-Type FET with comparable voltage and current ratings.
Even buying from an authorised distributor isn't a cast-iron guarantee...

Dodgy customer buys a big batch of genuine devices from an authorised distributor, gets the delivery note, pays for them... job done.

Then a few months later, they contact the distributor explaining they over-ordered and would they take them back and refund the price, less an admin/restocking fee? Distributor usually says Yes, takes them back maybe refunding 75% of the selling price. But... dodgy customer actually sends back an equivalent quantity of counterfeit devices against the original delivery note reference.

So, the next customer of the distributor actually gets counterfeit devices, which look just like the real thing - and in the meantime the dodgy customer has a stock of genuine devices which they've paid only 25% of the catalog price for. They sell them on, at maybe 80% of the list price, netting a healthy profit with no possibility of any dissatisfied customers!
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