Our products
Related
  1. 1PCB Surface-mount Technology
  2. 2PCB Through-hole technology
  3. 3Multiwire Boards
  4. 4PCB Cloning Service
  5. 5PCB Through-hole Technology
  6. 6PCB Cordwood Construction
PCB clone

PCB design

  Time:2012-06-07 11:16

Printed circuit board design was initially a full manual process.During this process, a initial schematic diagram was converted into a layout of parts,then traces were routed between packages terminals to provide the required interconnections.Pre-printed non-reproducing mylar grids assisted in layout,and rub-on dry transfers of common arrangements of circuit elements  such as pads, contact fingers, integrated circuit profiles,and so on, helped standardize the layout.Traces between devices were made with self-adhesive tape. The finished layout "artwork" was then photographically reproduced on the resist layers of the blank coated copper-clad boards.
Modern practice is less labor intensive since computers can aotomatically perform many of the layout steps. The general progression for a commercial printed circuit board design would include:
1.Schematic capture through an electronic design automation tool.
2. Card dimensions and template are decided based on required circuitry and case of the PCB.Determine the fixed components and heat sinks if required.
3.Deciding stack layers of the PCB. 4 to 12 layers or more depending on design complexity.Ground plane and power plane are decided.Signal planes where signals are routed are in top layer as well as internal layers.
4.Line impedance determination using dielectric layer thickness,routing copper thickness and trace-width.Trace separation also taken into account in case of differential signals.Microstrip,stripline or dual stripline can be used to route signals.
5.placement of the components.Thermal consideration and geometry are take into account.Vias and lands are marked.
6.Routing the signal trace.For optimal EMI performance high frequency signals are routed in internal layers between power or ground planes as power plane behaves as ground for AC.
7. Gerber file generation for manufacturaing.
In layout of the board, a power plane is the counterpart to the ground plane and behaves as an AC signal ground,whilst providing DC voltage for powering circuits mounted on the PCB. Where possible it is good to have a power plane for each ground plane on the board, known as  a "plane air",as this reduces power supply impedance to the components on the board. In electronicdesign automation (EDA) design tools,power planes(and ground planes) are usually drawn automatically as a negative layer.Adding primitive layout shapes on such a layer automatically produces a negative of those primitives,placing copper wherever there is no track or via.