In simple cases free data rescue software can help: Zero Assumption Recovery or
formatting software: SD Formatter (works also for USB flash drives).
But has your memory device suddenly started giving you error messages like: card error, unknown device, formatting required, unreadable, etc.? This indicates that a physical damage is present; most likely, the controller is damaged. Data rescue software can't help in this case. In almost every instance, the memory chips are intact and the data are actually available. When the memory chips of a memory device with this kind of damage are removed from the printed circuit board, it is possible to read the data with the help of a special NAND flash reader. However, at this point the data are raw data and must be compiled into readable data. This is the most difficult part of the rescue procedure, and is carried out by only a few service companies world-wide.

                Demounted memory cards/USB Flash Drive

With this method, I succeed in 92% of all cases in rescuing the data, even when other data rescue companies have said they can’t do it. For the 8% of cases in which I am unsuccessful in rescuing the data, the memory chips themselves are damaged or due to a controller malfunction the file allocation tables are overwritten with memory data. In the pictures below showing damaged memory chips, data rescue is impossible. Even the FBI is not able to do the job!

   Memory cards with broken memory chips - data rescue no longer possible