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To prepare design layout of PCBs using software tools.

Object: To prepare design layout of PCBs using software tools.

Apparatus: Designing software like Tina or Express PCB or CAD system.

Theory: Printed circuit boards are electronic circuits boards created for mounting electronic components on a nonconductive board, and for creating conductive connections between them. The creation of circuit patterns is accomplished using both additive and subtractive methods. The conductive circuit is generally copper, although aluminum, nickel, chrome, and other metals are sometimes used. There are three basic varieties of printed circuit boards: single‐sided, double‐sided, and multilayered.

 Layout: Layout is a circuit board layout tool that accept a layout-compatible circuit net list (ex-from capture CIS) and generate an output layout files that suitable for PCB fabrication.

Creating Layout Board having created the net list, the next list is to create a new board in Layout.  Launch layout then create the layout board file. When you create a new board files in ORCAD layout, you merge the electrical information from the layout net list (.MNL) and physical information from a template file (.TPL) or a technology file (.TCL) to create a new board design (.MAX). Therefore to be able to create a board file for a new design in layout, you need to provide a template file and a net list. A template (.TPL) file describes the characteristics of a physical board. A template can include information, such as the board outline, the design origin, the layer definitions, grid setting, spacing rules and default track widths.

Glossary of terms:

Footprint: The pattern and space on a board taken up by a component.

Clearance: The spacing required between two entities on a PCB to ensure safe operation.

Photo plotter: (also "vector plotter", or "Gerber photo plotter" after Gerber Scientific Co., which built the first vector photo plotters for commercial use). It plots images from a CAD database on photographic film in a darkroom by drawing each line with a continuous lamp shined through an annular‐ring aperture, and creating each shape (or pad) by flashing the lamp through a specially sized and shaped aperture.

Gerber File: Data file used to control a photo plotter. Named after Gerber Scientific Co., who made the original vector photo plotter.

Aperture: An indexed shape with a specified x and y dimension, or line‐type with a specified width, used as a basic element or object by a photo plotter in plotting geometric patterns on film. The "apertures" are thin trapezoidal pieces of plastic which are mostly opaque, but with a transparent portion that controls the size and shape of the light pattern passing through it.

Track: Besides its usual definition of a strand of conductor, wire on a printed board.

Fig 3.1: Layout

Pad: The PCB Component footprints have copper landing areas where the components are fixed by means of solder.

Fig 3.2: Pad

Through Hole: (Of a component, also spelled "thru‐hole"). Having pins designed to be inserted into holes and soldered to pads on a printed board. Plated‐Through Hole: A hole in a PCB with metal plating added after it is drilled. Its purpose is to serve either as a contact point for a through‐hole component or a via.

Fig 3.3: Through hole

Via: A plated‐through hole in a PCB used to route a trace vertically in the board, that is, from one layer to another.

SMD: Surface Mount Device, where the components’ leads are not fixed into PTHs but are soldered to pads directly.

Procedure:

  1. From the file menu in orCAD layout, choose new. The AutoECO dialog box appears.
  2. In the input layout TCH or TPL or MAX file text box, specify the name and the location of the technology file to be used for your board.
  3. In the input MNL netlist file text box, specify the location of the FULLADD.MNL created in the creating layout netlist section.
  4. From the drop-down list in the options section, AutoECO.

Result: We have studied the layout design by software TinaPro.

Precautions:

  1. Make connections right and tight.
  2. Switch off power supply when not in use.
  3. Handle the equipments carefully.

Questions:

1. What is layout?

2. What do you mean by schematic?

3. What is netlist?

 

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