Replacing memory chip in USB flash drive

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Replacing memory chip in USB flash drive

Postby Book » Fri May 07, 2010 10:32 am

Hello everyone, I'm in need of some help.

The other day, for no particular reason, my USB flash drive went dead. Plugging it into a USB slot does *nothing* (no LED light, & no indications on the PC whatsoever). I have been thinking that there must be some hardware problem with the controller, so I though I'd try swapping the memory chip on the malfunctioning drive, to a new, working flash drive. I'm pretty sure that if:

the original memory chip works, and
the new flash drive is of the exact specifications as the old one, and
I soldered the old chip correctly to the new drive, the end result would be a working drive, with the data.

The problem is that I don't have the same drive, and it's pretty old (the other problem would be soldering it, but it has been done before). Now, I must know if it would be possible for the above experiment to work with a flash drive of "similar" specs as the old one, but I do not know what specs are the required ones for it to work. Would anyone have any ideas on this? Can it be done? Has anyone tried this before?
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Re: Replacing memory chip in USB flash drive

Postby psilocybin » Fri May 07, 2010 10:15 pm

hasn't this been posted before? I'm getting deja vu here.

anyways. wow, you must have something pretty important on it to go through all this huh? the memory chip (I think they use flash prom?) will probably be something mass produced, so the controller chip will be tailored to the memory. assuming you can find another flash drive that uses the exact same memory chip, then yes it should work. It would be pretty damn hard to get that to work though. here's why:

1. it's going to be a pretty small surface mount device, so desoldering it is going to be a helluva thing. also, I don't know enough about semiconductors or flash technology to know how heat will affect the data stored on it, but I'd be careful with it getting too hot.
2. static electricity. once you get it off the pcb, if the chip doesn't have any built-in protection against esd, it will be extremely easy to fry that thing.
3. soldering it to another device is going to be hard if you've never done surface mount soldering.
4. finding a compatible device might be problematic if you can't find the same model that you're using. then again, most or perhaps all flash rom chips might have a similar or identical pinout/specifications, so maybe that's not a problem (I don't actually know whether or not that's true, maybe some research here would help :) ).

2 can be solved with anti-static measures, 1 and 3 might be solved if you got a heat gun (for desoldering and solder paste reflow) or learned how to do surface mount soldering with an iron (I've never done surface mount soldering, so I can't really help you there). I don't even know if 4 will be a problem.

If it's not doing _anything_ at all, the problem might be electrical. you might be able to figure out the problem by eye and fix it easily if you're lucky. if you open it up, look for black or brown spots on the pcb (which would indicate a short or a current surge, like if the 5 v rails from your computer's motherboard had a spike or an arc). also, look for discolored components which might be burned out. if it has any electrolytic capacitors (which I doubt for a device like this, but anyway...) look for bulging or signs or arcing. replace damaged components, and if part of the pcb has been burned, solder over it to re-close the circuit.

in conclusion, what you said should theoretically work, if you avoid the pitfalls I mentioned above. there might be other problems with this I haven't realized too, but I think I got it all.
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Re: Replacing memory chip in USB flash drive

Postby auzi » Sat May 08, 2010 11:55 am

nope, flash memory is a substrate of nand or nor gates. prom hasn't been mass-used since the 80s.

using psilocybin's structure
1 & 3. if you can't solder, give it up and try something simple, like useless DIP chips. you'd also need a hot air rework station to desolder it in the first place.
2. that's why you use tweezers and/or a micro-pneumatic pickup tool. not really a problem though, unless the chip is extremely sensitive, because most chip have snubber diodes on all pins to prevent ESD.
4. nope. you need to compare datasheets, it doesn't work like "they might look the same". farnell might be a good start

simply put, this isn't the best start for learning how to solder/desolder. but you should start easy. check if there's any accumulated dust and if the chip works if you wiggle the usb jack a little. these are the common problems.
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Re: Replacing memory chip in USB flash drive

Postby Book » Sun May 09, 2010 11:43 am

Thanks for the reply, I though I wouldn't be getting any.

Onto the point:
The drive employs this memory chip. Visually inspecting the drive didn't yield any results; everything looks normal. My "plan" as of right now is to try and find an exactly same drive (this is not going to be easy), and get someone with the right equipment and experience to do the delicate soldering work (I wouldn't dare to do this with an iron). I'm also worried about the heat somehow corrupting the memory, but hopefully the guy that does this work will have this in mind.

Now I do have other (different) flash drives, that obviously do not use the exact same chip. Would it be possible to replace it onto one of those drives? The other chips are also Hynix, and have the same number of pins, but I have no idea what other variables should match.

Obviously I only need the drive alive & working for a few seconds just to grab the data (which, in size, isn't much).

Thanks again.
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Re: Replacing memory chip in USB flash drive

Postby psilocybin » Sun May 09, 2010 2:00 pm

I don't know if the other drives will work, but there's a way you can check. Read the model number off the other memory chips from the other devices and google it for the datasheet (it's usually the first line). If you can find the datasheet, you can look at the pinout and see if it matches the pinout for the old chip. If it does, it will probably work.

Like I said, the chipset for a flash rom might be standardized so it might work anyway. Having never worked with flash rom (well, not directly), I don't know from experience, but that makes sense to me. But I'm just a student, and I'm still learning, so I can always be wrong.
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Re: Replacing memory chip in USB flash drive

Postby Cool_Fire » Wed May 12, 2010 8:24 pm

Basically, if it uses the same make/model memory chip it'll work.
But it's going to be freakin' impossible to actually do it, even with really good equipment like (de-)soldering ovens, absolute anti-static materials, tools and surfaces to work with.

It's just too small to do by hand.
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Re: Replacing memory chip in USB flash drive

Postby Book » Sat May 15, 2010 10:52 am

Browsing the web for some help, I found another interesting idea: connecting the flash chip on an xD card reader, while the chip is still soldered on the drive board. I already have a reader of this sort (SD "all in one" card reader) which has an Alcor controller in it. The broken drive also has an Alcor controller, but a different model. However, the flash chip to be read has 48 pins (24 on each side). The cards that the reader accepts have different number of pins, and none has exactly 48 (so that I could figure out a one-to-one correspondence).

So I don't know how to wire the chip on one of the readers inputs. Any ideas on what there is to do?

Also, by testing another flash drive of mine (containing a different hynix chip), heating doesn't appear to be a big issue. I heated the whole drive pretty much (I didn't measure the exact temperature due to lack of equipment), for more than 10 minutes, and the file which I had created for this purpose (filled the entire addressable memory of the drive, around 4GB) did not get corrupted at all (was validating its checksum at various intervals). I repeated the test 2-3 times, but still no corruption. I would be tempted to think that desoldering it wouldn't raise the chip's temperature high enough to cause corruption, as it would dissipate quickly.
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