Copper Area Ratio

This item checks for copper area ratio on each layer.

In many high-speed design practices, all signal nets are routed first and then the ground structure is constructed by automatically filling copper in empty areas. Ground surface has a lot of influence on circuit stability. Therefore, in order to reduce EMI problems, ground surface handling should be done more carefully. Well-designed ground surface structures are very effective for EMI protection as well as thermal and structural robustness. Improper copper coverage causes ground fluctuation, signal distortion and EMI problems. It also can cause board war page or twist by uneven heat dissipation and weight related issues. This item checks for copper area ratio on each layer. Lately, many designs fill ground for all layers to minimize EMI problems but they result in higher copper ratio.

With this DFE rule checking, you can evaluate the ground sensitivity against noise in each layer. Also, with the copper percentages produced by this option, you can predict and/or prevent board war page or twist caused by heat dissipation and weight related issues.
  • Except Board Area: Select the target layer which contains some void area. Upon selecting this option, DFE will subtract this void area when calculating board area.
  • Target Layer: Select target layer, all or certain layers. Upon selecting this option, DFE will show copper area ratio of each layer.
  • Target Net: Assign checking net. Upon selecting this option, DFE will show routing area ratio of each target net.
  • Object: Select routed object to be included for the Copper Area Ratio rule check.
    • Copper: Copper and Tear-Drop shape
    • Line/ARC: Line
    • Pin/PAD: Pin PAD
    • Via: VIA PAD
  • Line Width Type: For line objects included in item ③, define check criteria. For certain width line, they would be excluded from checking.
    • Not Check: Do not exclude by line width. In other words, program checks for all lines regardless of line width.
    • Max: Excludes lines wider than the value entered in column ⑥.
    • Min: Excludes lines narrower than the value entered in column ⑥
  • Line Width: Line width base
  • Subtract Drill: Drill areas are subtracted from the area calculation.
  • Combine net:
    • Check: Show the routing area ratio for net group.
    • Un-check: Show the routing area ratio for each net.

The image above shows copper percentages of top and bottom layers (layers 1 and 6) are similar at about 39.0 percent and inner layers (layers 3 and 4) are also similar at about 66 percent. This indicates that copper on the design spreads equally and it is well designed in this point of view.