Cadsoft Eagle is a multi-platform freeware circuit layout program. lots of open source hardware is developed in Eagle, and it’s become a hobbyist favorite. We use it for all of our hardware designs.
There are several ways to turn an Eagle design into an actual printed circuit board (PCB). We’ll show you how to save Eagle designs as industry-standard gerber files that are accepted by any PCB manufacturer. You can use the gerbers to purchase a single prototype, or a full panel.
Introduktion
Toner transfer is the beginners’ favorite way to make a PCB because the investment in materials is minimal. We’ve covered toner transfer before. many PCBs in our how-tos are made with the photo-resist process. The photo process makes good boards, but requires a bit of equipment; sensitized boards, developer, and an ultra-violet light source.
Some board manufacturers, like Olimex, make PCBs directly from Eagle .brd files. many require a minimum purchase of one eurocard-sized PCB (100mmx160mm). good if you need a few boards, expensive for a single experimental prototype.
The most affordable option is to submit gerber files like the professionals. any PCB producer will accept gerber formatted design files. Gold Pheonix sells 155square inches of PCB panel for $110. If you’re searching for something smaller, services like BatchPCB and PCB-Pool combine small orders and submit them as a full panel. Either way, you’ll submit gerber files to the board house. This is the process we describe.
Process overview
Prepare the design.
Create gerbers, generic files accepted by any PCB fab house.
Verify that the gerbers are correct.
Send the design for production.
Prepare the design
We’re going to walk you through the process of preparing our digital picture frame PCB for production. This design requires a double-sided board with fairly small traces.
Download the project archive (ZIP) from last week. open the .brd file with the freeware version of Cadsoft Eagle.
The ground fill is empty when the file opens. press the ratsnest button (or Tools->Ratsnest) to fill in the empty polygons.
Board producers publish specifications outlining their production capabilities, such as the smallest possible traces, spacing, and drill size. BatchPCB has 8mil minimum traces and spacing, and 20mil minimum holes.
Don’t torture the manufacturer. just because they advertise 8mils, doesn’t imply it’s safe to make every trace 8mils. slightly larger-than-minimum tolerances will decrease manufacturing errors. The digital picture frame has 8mil traces around the tiny LCD connector, shown above. The traces are 8mils only until there’s enough clearance to use 10mil traces.
Use Eagle’s design guideline check to make sure your board doesn’t exceed the manufacturer’s production abilities. download the SparkFun design guidelines (DRU) for BatchPCB, or the Olimex 8mil (DRU) or 10mil (DRU) design rules. Click the DRC icon (or, Tools->DRC) and load the design guideline file. Eagle analyzes the design and highlights any areas that break the design guideline parameters.
Correct any errors. Here, the spacing between traces is too close. in some cases the spacing on a part footprint is too small to be manufactured. Sparkfun’s default footprint for the Nokia LCD connector had pad spacing less than 8mils. We edited the part library to make the pads smaller, and the separation larger.
It’s valuable to include part numbers on the printed silkscreen layer. BatchPCB prints a silkscreen on both sides. Be sure to see what your board house offers, some charge extra. use the smash tool to unlink obscured labels, then relocation them to a better location.
Create gerber files
Gerber files are the PDFs of PCBs. Gerber files describe a PCB exactly as it ought to appear, agnostic of the display hardware. It’s a final production format that isn’t intended to be edited. We created our gerber files in Eagle using the procedure described in SparkFun’s Eagle tutorial.
The Eagle CAM processor writes gerber files, open it from the menu under File->CAM processor.
SparkFun has a script (CAM) that configures the CAM processor to make gerber files. load the CAM script using File->Open->Job…
By default, SparkFun’s silkscreen configuration only includes the place layer. Our parts typically have labels on the names and docu layers, activate these layers on the top and bottom silkscreen tabs to add them to the output.
Click process job to create the gerber files.
The CAM processor creates seven files that we need.
Top and bottom copper (.GTL, .GBL)
Top and bottom solder mask (.GTS, .GBS)
Top and bottom silkscreen (.GTO, .GBO)
Drill file, 2.4 leading (.TXT)
Verify that the gerbers are correct
Verify the CAM output in a gerber audience to make sure everything was positioned correctly. We followed SparkFun’s idea and used Viewplot.
Load the seven files with Viewplot. Be sure to specify the drill file type as 2.4 leading.Check for errant vias, mirrored layers, and alignment. We’ve discovered that text added to the silkscreen layer is typically bigger than it was in Eagle. appropriate any problems and run the CAM processor again.
When everything looks good, the board is ready for production.
Send the design for production
Zip the seven gerber files and submit them to the PCB fab house. remember to tell them that the drill file format is 2.4 leading.
BatchPCB is a pooled panel service that sells space by the square inch. other producers and batch services require you to purchase at least a full eurocard. We use BatchPCB for prototyping because we never need the extra board space of a full eurocard, and we don’t mind the average 20day wait.
At BatchPCB, $2.50/square inch purchases a PCB with silkscreen on both sides, limitless vias, and a substantial range of drill sizes; stuff that typically costs extra. BatchPCB’s minimum traces, spacing, and drill are similar to other prototyping services. There’s a $10 per purchase setup fee, but an purchase can include multiple designs. Shipping, even internationally, isn’t outrageous.
If you need a lot of the same board, look at Gold Phoenix. They manufacture boards for BatchPCB. A 100 square inch panel is $100, a 155 square inch panel is $110.
Create an account at BatchPCB. Click submit to add a new design. name the design and submit the zip archive including the 7 gerber files.
Verify that the gerber layers were successfully detected.
Verify that the appropriate size was detected.
The BatchPCB guideline check ‘robot’ will verify that your design meets production standards, and send an e-mail in a few minutes. because we ran our own guideline check prior to sending the design, we can expect that everything will be fine. Click continue and you’ll have the option to purchase the board. For much more help, see the BatchPCB help and support forum.
Receive your boards
Boards arrive from BatchPCB in about 20 days. check the boards for apparent errors before soldering. Some producers test PCBs, BatchPCB doesn’t. We’ve purchased PCBs from two of the popular hobbyist board houses, Olimex and BatchPCB, and all the boards have been satisfactory.
Taking it further
It’s easy to purchase professional PCBs using gerber files. Why not build that amazing diy project you’ve been putting off?
What has been your experience with PCB fab houses?
UPDATE: the files have been moved! find them here.