SD card and micro sd data recovery is the most difficult and time consuming of all data recoveries.
Shown below is a typical micro SD Card and typical SD card before its surface coating is removed and after the painstaking process was performed to remove the exterior coating without damaging the underlying circuit to gain access.
At this point, solder points can be made under a microscope and data and control buses can be accessed with very small wires.
Now, potentially the raw data can be dumped to a personal computer. This is a extremely tedious and time consuming task.
Once the raw data dump is retrieved, reverse engineering takes place. Custom algorithms have to be designed to unscramble the raw data and emulate the original controller to allow user access to the original data in its usable form. This also takes an extremely long time with the use of a hex editor and advanced recognition of page and bit patterns.