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Circuit boards or Printed circuit board or Printed Wiring Board (PCB / PWB), is board made out of non-insulating and highly heat-resistant insulating material such as fiberglass. These boards are also called substrates. A substrate or board may have only one single layer (Single-Layer Circuit Board) or more than one layer (Multilayer Circuit Board). A conductive metal such as copper is used to make conductive pathway or traces to facilitate flow of electricity. Once these conductive traces are etched on the substrate, it is termed as "printed circuit board". History of Circuit Boards dates back to mid-1930s, when an Austrian engineer Paul Eisler invented the PCB while designing a radio set. These radio sets were later massively used in World War II by United States. These circuit boards are of no good use until Electronic Components are mounted on it. Electronic components can be either through- hole components or SMD Components. Again the technology used to solder these components on the circuit board can be through-hole technology or Surface Mount Technology. Soldering material may include Solder in the form of Solder Wire, Solder Paste, Solder Balls for BGA (Ball Grid Array) and Solder Flux. As explained above, a printed circuit board (PCB) is a board made of one or more layers of insulating material (Fiberglass, Ceramic, Highly Heat-Resistant Plastic or any other dielectric material) with conductive pathways etched with metal such as copper. During the manufacturing process of the circuit board, traces of copper or any other conductor is etched off the board leaving only traces that are needed to mount / solder electronic components. Once all electronic components are mounted / soldered / assembled on the circuit board and the board is ready for use, it is called Printed Circuit Assembly (PCA) or Printed Circuit Board Assembly (PCBA). The current generic standard for design of a circuit board is IPC-2221A. IPC 2221A Generic Standard on Printed Board Design provides rules for manufacturing circuit boards and quality guidelines. These information and guidelines is applicable for all types of circuit boards including single-layer and multilayer PCBs and information includes substrate information, material properties, criteria for surface plating, conductor thickness, component placement, dimensioning and tolerance rules and more. Other circuit board designing standards are IPC-2220 and IPC-9592. It has to be noted that IPC and other standards will provide information on how to properly route the board. For a perfect and reliable circuit board design, you need good knowledge and understanding of PCB layout techniques and basic understanding of circuit operation. While designing a printed circuit board, one must take proper care of the substrate material based of type of soldering technology and components to be used. The width of the traces of the circuit board (circuit conductors) should be chosen wisely based on expected maximum temperature rise at the rated current and acceptable impedance. Other points to keep in mind with circuit board design are CTE, cost and dielectric properties. The designer needs to carefully balance the constraints of cost with reliability and performance needs. In addition, solder masks and via holes should also be selected carefully. HubPages. "Circuit Board: Design, Diagram and Assembly." March 16, 2010 http://hubpages.com/hub/Circuit-Board-Design-Diagram-and-Assembly
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