Custom Printed Circuit Boards
Creating your own, professional quality printed circuit boards, is not as hard, or as expensive, as you would think. There is a lot of good software out there and any number of PCB fabrication houses who are eager for your business, even though it is only one PCB that you want.
You could still etch and drill your own board, and that would be great if you like wearing horsehair shirts. But this is the Internet era - just send off your design and get a professional result back.
This article is aimed at the hobbyist who wants a custom PCB for their latest creation and does not want to pay the earth. It summarises one approach to creating the perfect PCB. If you are keen you can find other software and PCB houses, but this method works for me.
Most software packages require you to draw the circuit first. Then, based on the schematic, the software can generate the PCB. Either automatically or manually.
I use Eagle from Cadsoft (http://www.cadsoft.de). Eagle is reasonably popular and you can find a lot of support for it on the Internet. But, best of all, Cadsoft are kind enough to provide a limited version for free. The free version limits you to one schematic page (generally not a problem), just two layers (also not a problem) and a maximum size of 100 x 80 mm. The last restriction can be a bit limiting but you can get a lot in that size.
Eagle has its own unique way of operating but after a while it becomes quite natural to use. Cadsoft provide a tutorial but other people also provide some good how-to guides. One of the best comes from SparkFun in three "volumes":
- Getting started with Eagle PCB and capturing a schematic
- The basics of laying out a PCB with Eagle
- How to create a custom footprint and part in Eagle PCB (for the more sophisticated)
You only really need to do the first two tutorials. Sparkfun also provide a good hints tutorial that is worth reading. For example, Eagle defaults to a rather narrow track width and they provide some guidance for altering it.
The schematic drawing capability in Eagle is rather primitive and its main use is just to enter the schematic into the software. Having done that you lay out the components on the PCB and just click on the autorouter button... Voilà, you have a complete PCB. Well, not quite, you might have to rearrange components and tracks, but Eagle does 95% of the work. Old hands maintain that an autorouter is not as good as an expert human, and they are probably right, but the autorouter certainly does a better job than non expert me.
This is a schematic and the resulting board design:
PCB Design Tutorial
David L. Jones has created an excellent tutorial on the ins and out of PCB design. His paper can be downloaded from his website http://www.alternatezone.com/electronics/pcbdesign.htm.
The output from Eagle should be a set of Gerber files which can be sent to almost any modern PCB fabricator who will make the board and send it back to you. If you have never heard of the Gerber format you should refer to this short description.
The best part of modern PCB fabrication is the fact that it is so easy - you just send off your design via the Internet and back comes the board. No drilling, cutting and mess. The bad part is that it takes quite a few weeks, 4 to 6 weeks is typical.
I use BatchPCB. They aggregate many individual PCBs onto one large panel and send the design for the whole panel off to a PCB fabrication house in China, who make the panel, cut it into the individual boards and send the lot back to BatchPCB (who are in the USA). BatchPCB then mail you your boards. Other potential fabrication houses are listed here. Also, here are some more comments on PCB fabricators.
I have found BatchPCB to be one of the cheapest (even counting freight) and they also make it easy to submit boards designed with Eagle and the Sparkfun tutorials (described above). This is probably because BatchPCB is an offshoot of Sparkfun. If you follow the Sparkfun tutorials and upload the resulting design to BatchPCB you should get back a good, working board.
BatchPCB charge US$2.50 per square inch plus US$10 setup per order plus postage (as at April 2009). They will ship via standard air post which is fast and cheap (I hate wasting money on international courier companies). So, for a board of 100mm x 75mm it will cost you about US$45. Not bad for a professional quality double sided PCB with plated through holes, solder mask on both sides, and silk screen printing on both sides. You could not get better if you were IBM.
The resulting board also looks good...