Device for locking and unlocking at least one interface card plugged into a socket of a receiving system linked to a data processing system. The crystalline multilayer structure includes a base substrate and a corundum-structured crystalline oxide semiconductor thin film disposed directly on the base substrate or with another layer therebetween. Tests are performed on the memory chips and when a memory chip fails a test, the memory chip is placed in a repair bin and a test identifier is stored in the database in association with the memory chip identifier.