The foundation of every electronic device is the board on which every component is connected. The PCB consists of minute conductors, usually of copper, seen as fine lines criss-crossing the surface, mounted on an insulated substrate. The minute pathways actually carry data signals or power between the various components that are eventually soldered on the PCB. PCBs come in various sizes and shapes, and besides the motherboard, are also seen in expansion cards (sound cards, graphics cards, etc.) and RAM modules.