The phone arrived at our lab with a description that it had stopped working normally and data was inaccessible. A case that looks like a software glitch at first, but in reality is caused by a serious hardware fault on the motherboard.
Diagnostics and finding the cause
A restart loop, known as a bootloop, can have a wide range of causes in modern smartphones. It could be a software issue, a faulty PMIC power management circuit, a processor failure, or even damage to the UFS memory chip that stores all data and the operating system. Degradation of NAND blocks in the memory, failure of the controller inside the UFS chip, or corruption of critical system areas — all of these can prevent the phone from booting up.
In this case, diagnostics pointed to a fault on the motherboard. Suspicion fell on the PMIC power management area and the processor. We attempted to repair the original board directly, but the effort proved unsuccessful. The fault was so extensive that the only remaining solution was to transfer the key chips onto a functional donor motherboard.
Why replacing a single component is not enough
The Galaxy S23 Ultra uses UFS 4.0 storage — the latest generation of smartphone memory chips, offering significantly higher transfer speeds compared to earlier generations. All user data on this chip is encrypted. The encryption key is not stored in one place but is distributed across several hardware components.
A critical part of the encryption chain is the so-called unique hardware key, which is burned directly into the processor's silicon during manufacturing using one-time programmable fuses. This key cannot be read, copied, or extracted in any way. The cryptographic engine inside the processor can use it for encryption operations but never outputs it.
This means that the memory chip containing the data is nothing but a mass of unreadable encrypted blocks without the original processor. Conversely, a different processor would have a different hardware key and would be unable to decrypt the data. From an encryption standpoint, the processor and the memory chip form an inseparable pair.
Transferring chips to a donor board
The solution that offers a chance of data recovery in such a situation is exactly the opposite of what one might intuitively expect. We do not transfer a working processor into the faulty phone. Instead, we transfer the original processor along with the memory chip from the damaged board onto a functional donor motherboard of the same phone model. The donor phone is sacrificed in the process — its own chips are removed and replaced with the originals from the faulty unit.
The entire operation ranks among the most demanding in the field of mobile phone data recovery. The Galaxy S23 Ultra uses a so-called sandwich motherboard architecture, where two circuit boards are stacked on top of each other and connected through miniature solder joints. The processor, memory chip, and other key components are distributed between the layers of this sandwich. Any intervention therefore requires separating the boards first at precisely controlled temperatures to avoid damaging surrounding components.
The actual chip transfer involves carefully removing them from the original board, cleaning off residual solder and underfill, and then applying new solder balls using a precision stencil — a process called reballing. On the donor board, the original chips are then removed and replaced with the components from the faulty phone. The processor also had to undergo modifications to boot correctly on the donor board. Once completed, the sandwich board is reassembled and tested.
Unlocking and data recovery
After the chip transfer, the phone was successfully initialised to a state where the user password could be entered. This is yet another essential condition for success. The user's password is part of the encryption key derivation process — without it, no one could access the data, even if the entire hardware transfer went flawlessly. The customer knew the password, and after entering it, we created a complete copy of the user data.
Device: Samsung Galaxy S23 Ultra (SM-S918)
Storage: Samsung UFS 4.0
Problem: Bootloop caused by motherboard failure, sandwich board construction
Solution: Transfer of original CPU and memory chip onto a donor board with processor modifications, initialisation and password unlock
Result: All target data successfully recovered.
It is important to note that this type of intervention is destructive from the standpoint of further phone usability. The primary goal is data recovery, not device repair. The donor board, which in the case of the Galaxy S23 Ultra represents a cost of several hundred euros, also cannot serve its original purpose after the procedure. This makes the entire job one of the more expensive ones, and it is worth considering how valuable the data being rescued truly is.
Cases involving motherboard failure in modern smartphones are among the most technically complex, and success is never guaranteed. The chances of data recovery depend on whether the key chips — particularly the processor and memory — are still functional. In this case, the procedure was successful.
Technical terms explained
Bootloop: A state where the phone repeatedly powers on and restarts without completing the operating system launch. The user cannot reach the home screen or access any data. The cause can be either a software error or a hardware fault in the processor, power management circuit, or memory chip.
UFS 4.0 (Universal Flash Storage): The latest generation of memory chips used in premium smartphones. Compared to the older UFS 3.1 generation, it offers approximately double the transfer speed. The memory chip contains its own controller and NAND flash memory in a single package.
CPU swap (processor transfer): In the context of mobile phone data recovery, this refers to moving the original processor and other key chips from a non-functional motherboard onto a functional donor board. The goal is to restore the electrical environment in which the original chips can operate, thereby enabling access to encrypted data.
PMIC (Power Management Integrated Circuit): A circuit that manages power distribution on the motherboard. Its failure can cause system-wide instability, including the inability to complete the phone's boot sequence. During bootloop diagnostics, it is among the first suspects alongside the processor.
