On the next page, we'll look at the colored layers of the board editor, and see how they compare to the actual layers of a PCB. PCB composition is all about layering one material over another. The thickest, middle part of the board is a insulating substrate usually FR4. On either side of that is a thin layer of copper , where our electric signals pass through. To insulate and protect the copper layers, we cover them with a thin layer of lacquer-like soldermask , which is what gives the PCB color green, red, blue, etc.
Finally, to top it all off, we add a layer of ink-like silkscreen , which can add text and logos to the PCB. We use a palette of colors to represent the different layers. Here are the layers you'll be working with in the board designer:. To turn any layer off or on, click the "Layer Settings Before you start routing, make sure the layers above aside from tStop and bStop are visible.
Here's one last tip before we get to laying our board out. This is an interface trick that trips a lot of people up. Since the board view is entirely two-dimensional, and different layers are bound to overlap, sometimes you have to do some finagling to select an object when there are others on top of it. Normally, you use the mouse's left-click to select an object whether it's a trace, via, part, etc. In cases like that, EAGLE will pick one of the two overlapping objects, and ask if that's the one you want.
If it is, you have to left-click again to confirm. If you were trying to grab one of the other overlapping objects, right-click to cycle to the next part. EAGLE's status box, in the very bottom-left of the window, provides some helpful information when you're trying to select a part.
We right-click to cycle, and it asks us instead if we'd like to select Reset. Right-clicking again cycles back to VCC , and a final left-click selects that as the net we want to move. The new board file should show all of the parts from your schematic.
The gold lines, called airwires , connect between pins and reflect the net connections you made on the schematic. There should also be a faint, light-gray outline of a board dimension to the right of all of the parts.
Our first job in this PCB layout will be arranging the parts, and then minimizing the area of our PCB dimension outline. PCB costs are usually related to the board size, so a smaller board is a cheaper board. In the schematic editor we never even looked at the grid, but in the board editor it becomes much more important.
The grid should be visible in the board editor. You can adjust the granularity of the grid, by clicking on the GRID icon If you need finer control, hold down ALT on your keyboard to access the alternate grid , which is defined in the Alt box. Using the MOVE tool -- -- you can start to move parts within the dimension box. While you're moving parts, you can rotate them by either right-clicking or changing the angle in the drop-down box near the top.
The way you arrange your parts has a huge impact on how easy or hard the next step will be. As you're moving, rotating, and placing parts, there are some factors you should take into consideration:. Below is an example of how you might lay out your board while considering those factors. We've minimized airwire intersections by cleverly placing the LEDs and their current-limiting resistors. Some parts are placed where they just have to go the barrel jack, and decoupling capacitor.
And the layout is relatively tight. Note: The tNames layer which isn't visible by default was turned on to help identify which part is which. Now that the parts are placed, we're starting to get a better idea of how the board will look. Now we just need to fix our dimension outline. You can either move the dimensions lines that are already there, or just start from scratch. Then use the WIRE tool -- -- to draw a new outline. Before you draw anything though, go up to the options bar and set the layer to 20 Dimension.
Also up there, you may want to turn down the width a bit we usually set it to 0. Then, starting at the origin, draw a box around your parts. Don't intersect the dimension layer with any holes, or they'll be cut off! Make sure you end where you started.
That's a fine start. With the parts laid out, and the dimension adjusted, we're ready to start routing some copper! Routing is the most fun part of this entire process. It's like solving a puzzle! Our job will be turning each of those gold airwires into top or bottom copper traces. At the same time, you also have to make sure not to overlap two different signals.
After selecting the tool, there are a few options to consider on the toolbar above:. With those all set, you start a route by left-clicking on a pin where a airwire terminates.
The airwire, and connected pins will "glow", and a red or blue line will start on the pin. You finish the trace by left-clicking again on top of the other pin the airwire connects to. Between the pins, you can left-click as much as you need to "glue" a trace down. While routing it's important to avoid two cases of overlap: copper over vias, and copper over copper. Remember that all of these copper traces are basically bare wire.
If two signals overlap, they'll short out, and neither will do what it's supposed to. If traces do cross each other, make sure they do so on opposite sides of the board. It's perfectly acceptable for a trace on the top side to intersect with one on the bottom. That's why there are two layers!
If you need more precise control over your routes, you can hold down the ALT key on your keyboard to access the alternate grid. By default, this is set to be a much more fine 0. Vias are really tiny drill holes that are filled with copper. We use them mid-route to move a trace from one side of the board to the other. To place a via mid-route, first left-click in the black ether between pins to "glue" your trace down.
Then you can either change the layer manually in the options bar up top, or click your middle mouse button to swap sides. And continue routing to your destination.
EAGLE will automatically add a via for you. It's useful to put fabrication notes here such as the thickness of the PCB, stackup specs, soldermask color, silkscreen color, copper weight, material, impedance control specs, surface finish, any other custom requirements. Reference - Reference marks fiducial marks - these are critical for automated assembly and should be included in every design. At least 2 reference marks are necessary but 3 is ideal.
We've put together a useful guide on what fiducials are and how they are used. This layer is generally not printed on the PCB itself so make sure your polarity marks and reference designators are still on your tPlace Layer 21 and bPlace Layer 22 layers.
We're still working on it. This is what the layout looks like with all of the above layers displayed. Top - Top side copper tracks - all of the copper on the top of the PCB. Pads - Thru-Hole. Vias - Thru-Hole. Dimension Board Outline. Skipped tDocu - Top side part documentation - this can supplement your silkscreen layer for defining characteristics of your PCB. Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts.
It only takes a minute to sign up. Connect and share knowledge within a single location that is structured and easy to search. I am finishing up a PCB design for the first time in Eagle, and I need to know how to print the component names onto the silkscreen layer, how to I set the layers up so the right things are printed? Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group.
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