The flow of electrons down a macroscopic cable constitutes electricity. However, cables are generally large and bulky. In order to realize miniature electrical devices, printed circuits boards (PCB) are used. A PCB consists of an insulating substrate upon which tiny copper tracks are deposited. The tracks can connect individual components such as resistors and capacitors. When designing a PCB, there are several important dimensions. Substrate Dimensions Copper Weight Drilled Holes Copper Track Width
The PCB substrate is an insulating material typically only millimeters thick. One of the most important decisions in PCB design is deciding how large to make the lateral dimensions of the board. The lateral dimensions of a PCB are often limited by the final device casing it will be placed in, the size of electrical components to be placed on the board, and the width of the copper tracks.
The copper weight is another important dimension on a PCB. The copper weight refers to the thickness of the copper track deposited on the board. PCB manufacturers normally offer only these options: 0.5 oz (17.5 µm copper thickness); 1.0 oz ( 35 µm copper thickness), and 2.0oz (70 µm copper thickness). The greater the copper weight, the lower the track resistance.
A PCB is normally mounted and supported in place through the use of holes in the corners of the board. In order for this to occur, holes need to be drilled into the corners of the board. The dimension of the drilled holes need to be determined in the design phase. The device's final dimensions, substrate thickness and available screw size are the major factors which influence the size of the drilled holes.
The most basic unit on a PCB is the copper track. The lateral width of the copper track determines how many electrical components can be squeezed onto a board of a given size. Since resistance increases with decreasing copper track width, there is a trade off between making the track very narrow, allowing more components to be on the board, and making the track wider which reduces the electrical resistance.
