best technique 🙂
In Eagle polygons are used to make big copper areas on a PCB that aren’t necessarily traces. We use them all the time to fill blank space on a PCB with copper connected to ground. Less frequently we use them to make large power traces such as with the ATX Breakout Board. Here’s some notes on how to use and customize polygons in Cadsoft Eagle.
How to use
Open Eagle and start a new schematic and PCB. Go to the board so we can lay down a polygon.
- Click ‘polygon’ icon located in the toolbar
- In the top menu bar make sure the top (red) or bottom (blue) copper layer is selected
Route the polygon in the shape you want it. Make sure to close it at the starting point or you’ll have problems generating gerbers later.
A polygon with a dashed line will appear (picture 3).
This will now be a solid copper area on your final PCB. Next we’ll look at a few ways to customize it.
Sometimes it’s useful to make the polygon part of an existing trace or electrical net. For example if you wanted to beef up a power trace.
To connect the polygon to the ‘net’ you want, right click on it’s edge, and select ‘Name’. Here make sure ‘This Polygon’ is selected, and type in the net name you want it to connect to. Hit ‘Ok’.
Right click on the edge of a polygon and select properties. This opens the Polygon properties menu. From here you can customize the polygon.
This is the width of the polygon’s perimeter when you draw it on the board. It also affects some properties below.
Here you can select between two versions of fill for inside the polygon, solid or hatched.
Hatched line widths are adjusted in the width property. Line spacing is adjusted in the Mesh Distances property. We only use the solid fill option in our projects.
This is the clearance between the polygon and neighboring objects, such as other traces, pins, and other polygons.
Don’t torture your board house here. Low isolation values lead to PCBs with electrical faults from under-etching. Leave as much room as you can.
Rank determines if one polygons if above or below an overlapping polygon.
Assigning a lower rank to one polygon will make that polygon dominate the other as seen in the pic above. When using a ground fill over the entire board it is important for it to have the highest rank so other polygons can be drawn.
With thermals on, a pin will connect to the polygon through small traces extending from the pin center in 4 directions. Thermals make soldering easier, the part heats faster because the heat is not dissipated as quickly.
Disable thermals will make a solid pour trough the pin/pad. We usually use thermals. We only turn it off on high power traces that require more conductivity between the pad and the polygon.
Ground planes fill-up the empty spaces of a PCB with copper connected to ground. The ground plane connects all the ground pins on a PCB automatically, which usually makes routing easier. It can also reduce electrical noise on the board.
Filling the board with a ground plane is the first thing we do when designing a PCB.
- Draw a polygon
- Give it the same name as the ground connections on your schematic, usually GND
- Click the ratnest button to refresh the ratnest after adding parts or traces
Any parts placed in the ground plane with pins names GND will automatically connect.
Power planes are no different than ground planes, they just carry a power supply instead of ground. We use these for fat power traces where the board will carry a lot of current.
Power distribution for multiple voltage powered chip
Multiple supply polygons, good for power distribution especially on CPLD and FPGA chips.
Although a normal traces can be used here, concentric C shaped polygons provide both a power supply access, and give you more freedom with it’s shape.
1. Pour the Copper by using polygon tool
First, you need to create copper pours on the top and bottom and name them. Both layers have to have the same name in order for this process to work. Naming them identically tells Eagle that they’re both connected to the same electrical node. Let’s call both of them ground, or “GND”, using the NAME tool.
Click on Via
Once you’ve placed the via, use the NAME tool on it, and give this via the same name as your two copper pours. Eagle may ask if you want to connect the via node (N$2 or something) to node GND — say ‘yes’.
Now that you’ve got your GND via, you can use the COPY tool to copy it as many times as you like
want to reverse, right-click on edge polygon and rip-up
2. Ripup the whole pcb
Go to the command section in Eagle on the top left and enter – ripup; That is correct, pretty explicit
3. switch two layers
left-click and middle-click to change layers
4. Switch from routed to unround – use ripup tool
Much like the WIRE tool isn’t actually used to make wires, the DELETE tool can’t actually be used to delete traces. If you need to go back and re-work a route, use the RIPUP tool – – to remove traces. This tool turns routed traces back into airwires.
You can also use UNDO and REDO to back/forward-track.
note: wait when all process display completed
Then click the location you want to measure from. Unfortunately, the mark command doesn’t accept coordinates; you have to click the location manually (and therefore, it must be on the current grid).
This will set a reference point, you’ll see that a new box appears between the standard coordinates and the command line:
The first set of parentheses in this new area contains the rectangular offset from the mark to your current cursor location, as indicated by the R. In this example, I’m 0.1″ to the right and 0.7″ above the mark. The second set of parentheses is the offset in polar coordinates – I’m 0.71″ away at an 81.87o angle above the positive X axis.