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Can I use both copper layers for a single, higher-capacity connection?

My application involves some fairly high currents. I have widened the traces as much as practical, but would still like to increase current carrying capacity. I can specify heavier copper layer thicknesses, but PCB costs increase dramatically going from 2 oz/ft2 to 4 oz/ft2. The circuit is simple and will fit on one layer. It seems I could double the current carrying capacity by specifying the same circuit on both the top and bottom copper layers. If I could do this, I could get the current carrying capacity of a single 4 oz/ft2 layer by using two 2 oz/ft2 layers, which would be much more economical. In Eagle, however, once I have connected two pads together in the top layer, I cannot figure out how to also connect them together in the bottom layer. Any comments or suggestions? And thank you for a great tutorial.


Hi Mark,
I hope you are doing well upon receipt of this message. Just let you know you have a really good question and I will do my best to provide you some options. EAGLE v7 or earlier releases don't support Loop Routing, so if you are using an earlier version, you will need to consider using the Wire Command and draw the trace on the other layer. Make sure you use the name command to name the wire with the same name the pads signal are carrying. I have seen this done many time s and should work fine.

If you are using Autodesk EAGLE v8 or greater, that version does support Loop routing. Click on the ROUT command, on the top tool bar you will notice that Loop routing is deselected by default. Select the icon that enables it. From the layer selection, make sure you pick the layer you wish the loop rout to be on, from the action tool bar you can also select the desired wire width. Start at one pad and follow the path that best suits your trace.

I added an image that way its easier for you to find the loop routing options.

Best Regards,

Ed

looprouting.PNG
Mark Bohon (author)  eagleofficial1 month ago

Ed,

Thank you very much for that clear and detailed answer. I am using Eagle 8.2.1, and so can enable Loop Routing. Before receiving your answer, though, I found a work-around: I used Copy to put a copy of a trace in an unused area of the board; then I used Info to change the layer on which the copy of the trace was drawn; and then finally I used Move to place the copy on top of/underneath the original. The nice thing about this was when I put a red trace (top layer) over a blue trace (bottom layer), the combined traces turned pink, making very easy to keep track of which traces I had doubled and which remained to be done. While this worked quite well, your Loop Routing suggestion sounds like it would be the easier way to achieve what I wanted. Thanks again.

Mark Bohon

Hi Mark,
Great to learn you found a solution for this as well. Its obvious you have become quite comfortable using EAGLE as the tool of choice for your PCB needs. Make sure you continuously run DRC checks when taking this type of manual action on your board. The DRC dialog box has a SELECT option which allow you to only run CHECKS on areas you are working on. Consider using it often to make sure overlaps are not created by mistake.
Best Regards,
Ed