How Does An SD Card Work?

Unlike a hard drive, SD cards do not contain any mechanical parts, but rather use flash memory technology to store data. Flash memory is a highly condensed physical format that allows for rewritable memory and no loss of data when switched off.

It therefore differs from the traditional hard disk, which saves data via magnetic reading and writing, whereas the SD card uses electrical reading and writing. To electronically save data, the technology traps electrons on a grid by applying a voltage across a transistor (the electronic component equivalent of a switch).

Upon opening an SD card (as seen in Figure 2), we can see that it is composed of a silicon wafer, on which an integrated circuit including a management chip and storage element is located. The storage element is composed of a multitude of micro-transistors.

The transistor stores digital information in the form of electrons on the silicon wafer. The transistor acts as a door, only letting information through upon command. The electrons are stored in a grid that is isolated from the rest of the silicon wafer. This grid can be used several times to store information.

How long does an SD card last?

Contrary to popular belief, an SD card does not have an unlimited life span. Like many electronic elements, it is damaged over time with use. It is sometimes possible to find information on SD cards for several years, when the SD card is not switched on. When the SD card is not switched on or used, it will in turn have a longer life cycle.

If used, the SD card will age over time – the limiting factor in its life cycle being the number of write cycles performed on the information storage area. However, reading information is less damaging than writing, which requires a higher voltage, leading to gradual damage to the storage area over time.