Creation of a printed circuit board usually begins with a schematic capture of an electrical or electronic design that meets the specifications of the original circuit design. The schematic with the component selection list is then transformed into a circuit layout, usually with the use of a computer-aided design (CAD) program. The board layout includes component placements and conductor pathways or traces. Printed circuit boards are usually made from copper that is laminated to a fiberglass substrate. Circuit traces are typically produced by selectively etching the copper. Printed circuit boards can be fabricated as a single-sided, double-sided, or multi-layer configuration. As its name implies, through hole technology assembly indicates that the component leads are placed through holes in the board and soldered on the other side. There are three basic types of components used in through-hole technology (THT) assembly: (a) axial-lead components; (b) radial-lead components; and (c) single (SIP) or dual (DIP) in-line packages. Surface mount devices (SMDs), have leads or pads that are mounted directly to the board surface. In surface mount technology (SMT) assembly, holes are not required for securing the component.