Today, many modern NAND flash devices use a new type of architecture in which the interface, controller, and memory chips are integrated into one common layer of compound. We call such a structure monolithic.
Until recently, all memory cards such as SD, Sony MemoryStick, MMC and others used a simple "classic" structure with separate parts - a controller, a board and a NAND memory chip in a TSOP-48 or LGA-52 package. In such cases, the recovery process was very simple - we unsoldered the memory chip, read it into the PC-3000 Flash, and did the same preparation as in the case of ordinary USB flash drives.
However, what if our memory card or UFD device has a monolithic structure? How to access the NAND memory chip and read data from it?
In this case, to put it simply, we need to find a special technological output contact on the bottom of our monolithic device by removing its coating for this.
But before you get started with recovering data from a monolithic device, we must warn you that the process of soldering a monolithic device is complex and requires good soldering skills and special equipment. If you have never tried soldering a monolithic device before, we recommend that you practice on donor devices with unnecessary data. For example, you can buy a couple of devices just to practice your preparation and soldering.
Below is a list of required equipment:
- A high-quality optical microscope with a magnification of 2, 4 and 8 times.
- USB soldering iron with a very thin tip.
- Double sided tape.
- Liquid active flux.
- Gel flux for ball leads.
- Soldering gun (for example, Lukey 702).
- Rosin.
- Wooden toothpicks.
- Alcohol (75% isopropyl).
- Copper wires 0,1 mm thick with lacquer insulation.
- Jewelery sandpaper (1000, 2000 and 2500 - the higher the number, the smaller the grain).
- Ball leads 0,3 mm.
- Tweezers.
- Sharp scalpel.
- Pinout scheme.
- Adapter board for PC-3000 Flash.
When all the equipment is ready, you can begin the process.
Let's take our monolithic device first. In this case, it's a small microSD card. We need to fix it on the table with double-sided tape.
After that, we will begin to remove the compound layer from below. This will take some time - you need to be patient and careful. If you damage the contacts layer, the data cannot be recovered!
Let's start with the coarsest sandpaper, with the largest grit size - 1000 or 1200.
After removing most of the coating, you need to switch to a smaller sandpaper - 2000.
Finally, when the copper layer of contacts appears, you need to switch to the finest sandpaper - 2500.
If everything is done correctly, you will get something like this:
Instead of sandpaper, you can use this fiberglass brush, which perfectly cleans the layers of compound and plastic, and does not harm copper:
The next step is to look for a pinout on the site. .
To continue work, we need to solder 3 groups of contacts:
- Data I/O: D0, D1, D2, D3, D4, D5, D6, D7;
- Control contacts: ALE, RE, R/B, CE, CLE, WE;
- Power pins: VCC, GND.
First you need to select the category of a monolithic device (in our case it is microSD), and then select a compatible pinout (in our case it is type 2).
After that, you need to fix the microSD card on the adapter board for easy soldering.
It's a good idea to print out the pinout diagram of your monolithic device before soldering. It can be placed next to it so that it is more convenient to refer to it when necessary.
We are ready to start soldering! Make sure your desktop is well lit.
Apply liquid flux to the microSD pins with a small brush.
Using a wet toothpick, place all the balls on the copper pins marked on the schematic. It is best to use balls with a diameter of 75% of the size of the contacts. The liquid flux will help us to fix the balls on the surface of the microSD.
After placing all the balls on the contacts, you will need to use a soldering iron to melt the solder. Be careful! All procedures are carried out gently! To melt for a very short time, touch the balls with the tip of a soldering iron.
When all the balls are melted, you need to apply gel flux for ball leads to the contacts.
Using a soldering dryer, you need to heat the contacts to a temperature of +200 C Β°. The flux will help spread the temperature across all the contacts and melt them evenly. After heating, all contacts and balls will take on a hemispherical shape.
Now you need to remove all traces of the flux with alcohol. You need to spray it on the microSD and clean it with a brush.
Next, prepare the wires. They should be the same length, about 5-7 cm. You can measure the length of the wires with a piece of paper.
After that, you need to remove the insulating varnish from the wires with a scalpel. To do this, just gently scrape them on both sides.
The last stage of preparing the wires is tinning them in rosin so that they are better soldered.
And now we are ready to solder the wires to the adapter board. We recommend that you start soldering from the side of the board, and then solder the wires from the other side to a monolithic device under a microscope.
Finally, all the wires are soldered and we are ready to use the microscope to solder the wires to the microSD. This is the most difficult operation, requiring great patience. If you feel tired, rest, eat something sweet and drink coffee (blood sugar will eliminate hand shaking). Then continue soldering.
For right-handers, we recommend holding the soldering iron in the right hand, and holding the tweezers with the wire in the left hand.
The soldering iron must be clean! Don't forget to clean it while soldering.
After soldering all the pins, make sure none of them are touching the ground! All contacts must be very tight!
Now we can connect our adapter board to PC-3000 Flash and start the data reading process.
Video of the whole process:
Note. transl.: Just shortly before the translation of this article, I came across the following video, suitable for the topic:
Source: habr.com