The most important heavy copper PCB design guide is the line width and line space for heavy copper PCB; meanwhile the DFM (design for manufacturing) is very critical for heavy copper PCB because most of PCB design guides will not meet heavy copper PCB. Lots of PCB suppliers can manufacture PCB with 3 mil ~ 4mil line width and line space as min trace/space, but it is not meet the requests of heavy copper PCB, 3 mil circuit line width is always for 0.5 OZ or 1 OZ copper layer on PCB, but not for heavy copper PCB (3 OZ ~ 20 OZ copper PCB). PCB manufacturers can’t do 3 mil line space for 20 OZ PCB, this is why PCB designers have to consider the DFM. And here is the Design Guide for Heavy Copper PCB:

1. Circuit board trace, depending on its size and manufacturing process, may not be rectangular in shape. Heavy copper conductors can significantly add to the overall board thickness.

2. Typical conductor width/spacing/thickness tolerance is +/-20%, although tighter.

3. The minimum width and thickness of a heavy copper PCB conductor is determined primarily on the basis of the current carrying capacity required and the maximum permissible conductor temperature rise.

4. Additive (plating) processed are preferred to subtractive (etching) processes but are more expensive).

5. Tolerance is achievable.

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