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I am trying to help a friend who is very concerned that she has just lost all of the data on her 32GB SanDisk microSD card. I told her I would post this and see if anyone could offer help.

Here are the details:

  1. The SanDisk microSD card is less than two years old. Probably only about a year old. The store will take it back, but that doesn't really help. She wants her data.
  2. She used the card in her Samsung Galaxy S4 smartphone for over a month. The phone was never exposed to water or temperature extremes.
  3. Today, her phone suddenly said something like "Your SD card is blank or an unsupported format".
  4. Her phone was then unable to read the SanDisk microSD card at all.

Here's what she has tried:

  1. Rebooting her phone. Had no effect.
  2. Taking out the SanDisk microSD card and putting it inside a full-size SD card adapter, and inserting it into a Windows 7 SP1 computer. The computer did not recognize its presence at all.
  3. Putting the SanDisk microSD card into a USB 2.0 external card reader and inserting the card reader into a USB port on a Windows 7 SP1 computer. The computer recognized the card reader and installed drivers for it. The card reader shows up as 'Removable Disk' in Windows Explorer. Clicking on 'Removable Disk' in Windows Explorer results in the error "Insert disk: Please insert a disk into the Removable Disk".
  4. After trying #3, tried opening the 'Removable Disk' in FreeCommander. Doing so results in the error "The device is not ready".

She does not have access to a Linux box, but does have access to her Android phone.

What can she do to recover the data on her 32GB SanDisk microSD card?

Amazon Dies In Darkness
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2 Answers2

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You could try pressing the card together (in case it came a little loose?) and maybe cleaning the contacts with a little bit of isopropanol on a swab. But I really wouldn't expect any results, and at best you might manage to read some of the data off before it dies again. I would not recommend opening it up under any circumstances - that will not help recovery any, and it will likely cause further damage.

You could also try various alternative readers - if you manage to find one that can at least expose the card as a block device, then you can take an image of the data (while recovering useful data from an image of damaged media is a whole other exercise - it's still better than where you are now).

Sometimes, there just isn't anything that can be done. If the data is very important, you could consider professional data recovery services (do they even exist for SD cards?), but they'd be very expensive. Otherwise, she might just have to accept the loss and try to recreate what she can.

When a storage device becomes physically unreadable, undetectable even, you can't go through the normal home data recovery steps (take image, scan for what files you can, etc.). With a mechanical drive, at least common failure modes are partial, so you can at least read something. With the nature of NAND storage, I can think of three possibilities:

  • You've lost the controller. The flash chip itself might still be readable, but reassembling the data from it will be a long and arduous task. This is not doable at home, and requires expensive, professional tools and expertise. (If you had the equipment to solder tiny chips (source) and read NAND flash, I suppose you could attempt this yourself, but you're more likely to accidentally destroy it.)

  • You've lost the flash chip itself. In this case, I don't think there's anything you or anyone else can do. It would be even harder to recover than a lost controller.

  • The card is physically damaged, but the controller and flash memory are intact. This is probably the best you can hope for. Again, with how small and fragile the card is, there isn't much you can do at home - but the chance of professional recovery is far higher.

The problem with all these is they require very expensive and still uncertain services to even attempt a recovery. Is the data worth that much?

Perhaps the best thing to do is to treat this as a lesson on backups - always have at least one extra copy of any data you can't afford to lose. The more important it is, the more copies you want, stored separately from each other.

Bob
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As a rule of thumb if the MicroSD isn't detected in Windows Disk Management with correct capacity then no software will be able to help you (assuming you tried the obvious like cleaning the contacts and trying different reader etc. - hint: try built-in laptop readers they may be PCIe connected rather than USB).

disk management

Possible reasons:

Broken surface mounted resistor on PCB replaced by copper wire was all that was needed in this case. Note that from data recovery perspective USB Flash Drives and memory cards are identical.

broken resistor

  • Some physical defect. Unlike PCB based full-size SD cards there isn't much that can be done to repair the device. Unlike with full-size cards we can not try to identify defects like broken capacitors and such, we can not replace the controller, we can not move NAND memory to a donor etc.. Even labs don't attempt these kinds of repairs. If we look at the MicroSD in detail we can understand why (Fact you were able to get the card going by applying pressure is sheer luck or coincidence):

naked microSD

  • Second major reason for this type of cards failing is "firmware issues". These in turn can be caused by for example sudden loss of power that the card can not recover from or NAND degradation. Simplified, NAND degradation resulting in such an amount of read errors the controller gets overwhelmed. Occasionally if the latter happens if we give a card enough time it can self-recover.

Can data be recovered?

For those that don't have the luck of applying pressure being enough to get the card going this may be the golden question.

If nothing helps then a data recovery lab may still be able to recover data from it. The main determining factor is if the NAND is in one piece and did not develop a physical defect.

In above image you can see some of the pins being marked because they allow us to access the NAND memory without relying on the controller. It allows us to bypass the controller and read the contents from the NAND directly, they're pins that are for example data signals, clock signals etc.. We often first need to reveal the pins by carefully scratching the surface to expose them.

In case we're dealing with a common 'pinout' we may have adapter we can connect to a reader or else we need to solder enameled copper wire to connect the card to a NAND reader.

microSD adapter or soldering copper wire

If it's a totally unknown pinout a lab can try 'creating' one by using a logic analyzer device. This will increase the price of a recovery! From this screenshot we can recognize the marking we find back in the above image (D1, D2, D3, etc.)

screenshot logic analyzer

Once we have everything set up we're ready to 'dump the data'.

It's only half the battle won though! We can not just run some file recovery tool and extract data from this dump: Since we read without relying on the controller we basically have now a large 'binary blob' that requires (XOR)-descrambling, error correction plus we need to determine the layout in which data was organized. As a final step we need to build a virtual translator to connect LBA blocks to physical blocks (remember that NAND based devices tend to shuffle data around for for example wear-leveling purposes).

We then take that and save that as a 'logical' image from which data can be recovered (although specialized tools are able to skip this step too and give us a file / folder structure straight away).

reading NAND and transforming dump

Monoliths in general can not be repaired, whether it being a full size SD Card or microSD. Full size SD Card can also be PCB design which sometimes allow the card simply be to be repaired so we don't have to do all the complex and time consuming stuff:

enter image description here

Only very occasionally can a monolith be repaired if we can for example observe broken traces after exposing the surface. An even closer look at a microSD card to illustrate how 'real' repair is virtually impossible:

enter image description here

Repair or destruction? In this case it was determined data could only be recovered by physically disabling the controller. X-Ray was used to determine the location of the controller. This is a monolithic USB Flash Drive, but again from perspective of data recovery these and microSD cards are one and the same:

enter image description here