General > General Technical Chat
Chips pulled off dumped PCBs and then sold, due to the "chip shortage"?
Faringdon:
Thanks, from what kind contributants are saying, this is done, but eg, a "desoldered and cleaned up" 20TSSOP couldnt be cleaned up well enough to appear as new?
Also, it makes you wonder about the ESD situation of it.
ryan_zheng:
--- Quote from: Faringdon on August 30, 2022, 07:35:52 am ---Thanks, from what kind contributants are saying, this is done, but eg, a "desoldered and cleaned up" 20TSSOP couldnt be cleaned up well enough to appear as new?
--- End quote ---
It can be done if they want to. A quick search on Taobao and I found "tin removing liquid".
After using such liquid to remove all tin plating and solder residues, I imagine they can chemically tin the pins again to make it look brand new.
--- Quote from: Faringdon on August 30, 2022, 07:35:52 am ---Also, it makes you wonder about the ESD situation of it.
--- End quote ---
If whoever wants so they definitely can put care into it. Otherwise yeah it may be less than ideal.
AndyC_772:
It goes without saying that these chips have not been handled according to any ESD precautions; they will have been exposed to ESD events and most will have latent damage.
That's not the worst thing in the world, though. The only reason to buy these recycled parts at all is desperation, and if what you really need is one or two microcontrollers so you can develop code at your desk ready for production that might be a year away, it's not the end of the world if a chip dies. Just make sure you have spares, and never let any of them outside an R&D environment. You can still develop good code on a flaky chip, and chances are you will come across a perfectly good one from time to time.
Personally I'd be more concerned about them having had OTP memory programmed, or non-reversible code protection enabled. On an STM32, setting code protection level 2 means the chip can never be reprogrammed again using an external debugger. For all practical purposes it's scrap, and I can all but guarantee the vendor won't care.
Also, if the brown-out reset voltage is set to a level that's above the supply voltage used on your board, it'll never exit the reset state. The chip is effectively dead unless you can increase the supply voltage and then reset the option bytes, and if you can't do that on your board, then it's useless.
(Learn from my mistake, folks! The BoR voltage setting can easily catch you out when you migrate a design from 3.3V to 2.5V without changing the option bytes... you'll soon remember the first time you upload newly modified code from a previous hardware revision into a new platform!)
coppercone2:
those parts soaked in tin removing liquid are dodgy as fuck. Think about it, you get a part that is soaked in some kind of acid after its been desoldered. There could be cracks in the plastic from the desoldering and previous use that have whatever tin removal stuff that is used go into the chip. those bond wires are really not that durable. And then you also have tinning liquid going on a bonded die chip.
The stuff you get is tinned BEFORE the die is bonded. That means rigorous cleaning. :--
I am not sure ESD is your primary problem anymore!
I strongly suggest if you reuse parts, you just desolder them, clean them with alcohol and resolder them. I don't think you should be using any kind of chemical dips for cosmetic purposes.
Kasper:
It seems this has been a problem for years.
--- Quote ---The [usa] military estimates that up to 15 percent of all spare and replacement parts for its weapons, vehicles and other equipment are counterfeit, making them vulnerable to dangerous malfunctions.
[...]
Between November 2007 and May 2010 alone, U.S. Customs officials seized 5.6 million counterfeit microchips destined for military contractors and the commercial aviation industry, and the problem has only grown since then.
--- End quote ---
https://www.scientificamerican.com/article/the-pentagon-rsquo-s-seek-and-destroy-mission-for-counterfeit-electronics/
--- Quote ---a Florida woman last month [in 2010] pleaded guilty to her part in the sale of $16 million worth of such rebranded counterfeit chips to the US navy and multinational arms firm BAE Systems
--- End quote ---
https://www.newscientist.com/article/dn19819-the-phoney-chips-that-could-cripple-military-tech/
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