Circuit Board Design Class
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Introduction: Manufacturing

As soon as the design is complete, your board is ready to be printed. While there are instructions online for creating your own board, I recommend that your first one be professionally manufactured. In this lesson we will go over generating gerber files for manufacturing, reviewing your gerber files, and then a little bit about selecting a manufacturer.


Measure Twice, Manufacture Once

Before I generate the production files, I want run two separate checks to validate the board.

The first check is to look for missing airwires and certify there are no connections missing between components. To accomplish this we once again simply press the magic ratsnests button. It should return "Nothing to do!" This indicates to us all of the airwires have been connected.

The second check is to look out for any glaring design errors. On the bottom of the left-hand toolbar we need to select the DRC button (Design Rule Check) which is basically just a button with the initials DRC with a check mark. Once selected, a new window should open. Click on the "Load" button and select "default.dru," and press "Open." You will then be redirected back to the original window where you simply press "Check." If all goes well, the phrase "DRC: No errors." will load at the bottom of your design window.

If all does not go well, the "DRC Errors" window will load with a list of errors. By clicking on each itemized error is will give an explanation what is wrong, and highlight on the board where the error is occurring. It is imperative that all of the errors are resolved before proceeding. Typically I don't use the check process in the error window itself. Instead, I exit out, make the necessary changes that it has indicated, and just run the DRC again (until the errors don't appear).


Generating Gerbers

In an ideal world, we would be able to just send the Eagle files to the manufacturer and be done with it. However, Eagle is just one PCB design software package in a universe of design software packages. As well, Eagle has so many different layers that a manufacturer might not be sure which layers you meant to include and which ones you did not.

For both of these reasons, we need to generate a special type of CAM file called gerbers. Gerber files are basically the universal format for circuit board production. Regardless of what piece of software you used to generate the board, the gerber files are always going to follow the same format. Thus, when a manufacturer receives these files, they know exactly what needs to happen.

In the olden days (2016 or earlier), you used to have to open Eagle's native CAM processor and go through an elaborate rigamarole to generate gerber files. You still can do this if you want, but I don't recommend it.

Eagle's new process for creating gerber files is much more simple, and the one I will be using. It basically involves uploading the board to Autodesk Circuits, which is Autodesk's online hub for all things electronics. By uploading your board file here, all of the appropriate gerber files will be automatically generated.

To upload your files to Autodesk Circuits, press the "Make' button on the right-hand side of the top menu bar. After that, just follow the prompts that pop up to upload your board file and log into the circuits.io site. This will redirect you away from Eagle and to a web page on your default web browser where your file has just been uploaded.

Once logged into Autodesk Circuits, you will be presented with your circuit board in a viewing window. First, look at the top and the bottom of the board and see if they appear correctly. If you have done everything right, this should be no problem. Otherwise, go back to Eagle, make the necessary changes to your board, and re-upload it.


Reviewing the Files

After the quick visual check, you will want to look at the gerber files themselves. To do this, click on the "layer stack" button in the top right-hand side of the window to switch views.

You should see a list on the left-hand side with the following files:

LayerDescription
Top View A composite rendering of all of the layers on the top of the board. This layer has no equivalent gerber file and is unique to Autodesk Circuits.
Top Silkscreen The top silkscreen layer for the circuit board as it appears.
Top Copper The copper layer as it appears on the top of the board. This layer does not account for drill holes.
Top Soldermask The soldermask layer displays the inverse of where the soldermask appears. In other words, where there is black displayed, there will be no solder mask.
Bottom View A composite rendering of all layers on the bottom of the board. This layer has no equivalent gerber file and is unique to Autodesk Circuits.
Bottom Silkscreen The bottom silkscreen layer for the circuit as it appears. This layer is typically not used.
Bottom Copper The copper layer as it appears on the bottom of the board. Like the top copper layer, this one also does not account for drill holes.
Bottom Soldermask This is the soldermask layer on the bottom of the board. It too returns an inverse display.
DrillsIndicates all of the holes to be drilled through the board.

Toggle through the gerber files and make sure there is information there, and everything looks about right. The drill file should have guides for drilling. The silkscreen file should have everything that needs to be silkscreened. The other files should have whatever the other files are supposed to have. If they don't, you need to go back, figure out what went wrong during the setup process, and create new files.

When you are sure they all look correct, scroll down the page and click the big "Download Gerber" button to download the zip file to your computer. This file is what you will be providing to the manufacturer.

If you want to take a look at my files, you can find them on the Octave Up Pedal Instructable.


Selecting a Manufacturer

There are so many different PCB manufacturers to choose from, and there are pros and cons to them all. Selecting one can be a daunting task the first time you are having a board made. This is especially true since there is no one thing that would make one stand out above the rest, and most manufacturers provide roughly the same services.

You need to weigh many different factors including cost, turnaround time, scale of order, ease of interaction, and added features such as as fun-colored boards, flexible PCBs, or certified lead-free production.

To give some hypothetical real world examples, one manufacturer might be really cheap because they batch your jobs together with dozens of other jobs and produce them all at once. However, they have no real board options to choose from. Additionally, they only do this once a week, and they also use the cheapest possible shipping, which makes turnaround times very slow.

Another manufacturer might cost a lot more, but they can get you a board in 3 days. However, they are set up exclusively for low-volume production with fast turnaround times and can't cheaply produce hundreds of boards.

A third manufacturer might produce thousands of boards cheaply and have fast shipping, but they might not speak the same language as you and ordering is challenging.

In short, you need to weigh the various considerations and decide what is important to you.


Often, word of mouth is the best way to find a PCB manufacturer. Ask your friends who they have used to have their PCBs made. If your friends don't make PCBs, or you have no friends, Adafruit has created a list of popular manufacturers and explain some of the pros and cons of each.

Lately, I have been having my boards produced by PCBWay. I find their prices, quality, and turnaround times to be reasonable at the small scale at which I am working. I should note that I am in no way affiliated with their business, I just personally choose to use them.

Ultimately you just need to pick the manufacturer which looks like it might work best for you.

Another thing to keep in mind when working with low-volume production is the cost to make one might be roughly as much or the same as the cost to make ten. A lot of the initial charge is setup fee, and producing addition boards might be possible at little to no cost.

In my opinion you should always order more than one in case one is corrupted, you assemble it wrong, or there is a design flaw and that you need to debug. Five is a fairly safe number and not too excessive.


Wait

After your board is submitted to the manufacturer and you have paid them a bunch of money, the only real thing left to do is wait. I do not recommend compulsively checking the mailbox, or online tracking information. Worrying about whether or not your board has errors is also not helpful. It is best to forget about all of this for a while and find something else to do.

CLASS PROJECT

Share a photo of your finished project with the class!

Nice work! You've completed the class project