expansion card 
(also expansion board)
noun Computing
A circuit board that can be inserted in a computer to give extra facilities or memory.With almost everything I need integrated on the motherboard, the only expansion card I have in my PC is the graphics card....
- The terminals are used for electrically connecting the elongated expansion card with a printed circuit board on which the card connector is mounted.
- If you have ever added an expansion card to your computer, you are almost half-way to building your own system.