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Wednesday, June 13, 2012

Data Required for PCB Layout

Data Required for PCB Layout


Physical description data sheets from the component manufacturer, of all component land patterns that are not in your PCB Design software Libraries. Only mechanical data is required, IE: Pin Spacing in Metric Units, Lead Size or Hole Size in Metric Units, Pin Numbers.


Identify where is pin 1, pin 2, pin 3 and the connector End Pins assignments

Constraint Drawing

Board outline illustrating dimensions in Metric Units and the location of all fixed component coordinates in Metric Units. IE: Mounting Holes, Connectors, Switches, Potentiometers, etc.

This can be obtained from a mechanical drafting tool i.e. AutoCAD or Solidworks in DXF format. Some PCB tools require specific version of the DXF file. It should be noted that the units used in the mechanical draft (DXF) should match the PCB software's design units when importing the DXF file.

Note: The CAD origin, (X=0, Y=0) should be in the lower left Mounting Hole of the board.


PowerPCB format netlist including the shape names of the library land patterns is required. The header at the top of the netlist should be: !PADS-POWERPCB-V4.0-METRIC! 
(In this example, the software used was PowerPCB which is now Mentor Graphics' PADS)


Need schematic to debug the netlist if “one pin nets” occur or if only one pin of a two pin part is in the netlist. Schematic is also used to place components.


Pencil sketch of suggested component placement layout map of major components. 
It is highly recommended that the engineer participate in the part placement to avoid duplication.

Power and Ground Plane instructions including bypass capacitor fanout, BGA & QFP fanout. If there are multiple nets on the same layer, need Split Plane information.

Clock, or High Speed trace instructions - Matched Length, Differential Pairs and Trace Widths in Metric Units. Special Route Layers, Impedance, etc. and include the net name reference. What needs to be hand routed and what can be auto-routed?

Silkscreen text identification requirements including copyright, board name, part number, revision level, connector ID’s, reference designator rotations and polarity markings.

Special fabrication notes, layer construction and panel information. 
Provide special assembly notes and drawings that illustrate special assembly information.

1 comment:

  1. Thanks for such an informative article and the extensive explanation, it's been very useful.circuit board assembly ,pcb suppliers