pcb design

What are the main benefits of rectangular connectors? When compared to circular connectors rectangular connectors are generally less expensive,have shorter lead times and are more easily customizable.Rectangular Connectors are also have better grounding system providing more protection against overvoltage and have a visual polarization for easy mating. They can also be easily keyed. Key advantages for using rectangular connectors over circular includes: 1. Off-the-self modules for easy custom designs for any application. 2. superior space efficiency. 3. more termination option-crimp,solder, screw terminal, others. 4. More locking options-single or double-lever or push button. 5. Ability to connect to other device such as PCB. 6. Greater contact Density Possible. 7. Greater cabling Flexibility- Top,Dual,side or angled cable entry. 8. Surface mount,Panel mount and cable to cable compability. 9.lower cost. 10.Better protection against over voltage. 11. easier Visual matin

QFP  —Quad Flat Pack, a fine-pitch SMT package that is rectangular or square with gull-wing shaped leads on all four sides. The lead pitch of a QFP is typically either 0.8mm or 0.65mm, although there are variations on this theme with smaller lead pitches: TQFP   also 0.8mm; PQFP   tooled at either 0.65mm (0.026") or 0.025" and SQFP   at 0.5mm (0.020"). Any of these packages can have a wide variety of lead counts from 44 leads on up to 240 or more. Although these terms are descriptive, there are no industry- wide standards for sizes. Any printed circuit designer will need a spec sheet for the particular manufacturer's part, as a brief descrition like "PQFP-160" is inadequate to define the mechanical size and lead pitch of the part.    Ratsnest  —A bunch of straight lines (unrouted connections) between pins which represents graphically the connectivity of a PCB CAD database. [Derived from the pattern of the lines: as they crisscross the board, the lines

Manhattan length  —The length of the two sides of a right triangle as a distance between two points, as opposed to the hypotenuse.. (Derived from the Manhattan Alogorithm  for determining the length of a taxicab trip following streets and avenues on the island of Manhattan, NY.)  Routing of traces in orthagonal patterns in a PCB design, or in a semiconductor chip, follows the same pattern as streets and avenues in a city.  The minimum distance between two component leads, or two nodes on a chip, when routing on 90 degrees is the  Manhattan length  .  Advanced PCB auto-routers permit specification of maximum length of classes of nets as a percentage of  Manhattan length  . For example, one could specify clocks as 120% and random nets as 160% of  Manhattan length  . (This percentage, expressed as a ratio, becomes the "Manhattan coefficient", ie. a Manhattan coefficient of 1.2 means the routed length is 120% of the  Manhatten length  .) Specifying such limits on the auto