PCB Design

Hi Makers!

Here's some information regarding PCB design. Scroll down to see the class specific FAQ and to get the DRU file.

Useful links

PCB Basics
https://learn.sparkfun.com/tutorials/pcb-basics
"One of the key concepts in electronics is the printed circuit board or PCB. It’s so fundamental that people often forget to explain what a PCB is. This tutorial will breakdown what makes up a PCB and some of the common terms used in the PCB world."

PCB terminology
http://www.build-electronic-circuits.com/pcb-terminology/
Trace? Via? Silkscreen? Gerber? Double-sided PCB? All the answers are on this link.

Sparkfun EAGLE Tutorials
How to Install and Setup EAGLE: https://learn.sparkfun.com/tutorials/how-to-install-and-setup-eagle
Using EAGLE: Schematic https://learn.sparkfun.com/tutorials/using-eagle-schematic
Using EAGLE: Board Layout https://learn.sparkfun.com/tutorials/using-eagle-board-layout
Excellent tutorial if you want to use EAGLE. Note that Sparkfun provide free libs for the products they sell.

PCB Design Basics - EDN
Part 1: http://www.edn.com/design/pc-board/4424239/1/PCB-design-basics
Part 2: http://www.edn.com/design/pc-board/4426878/PCB-Design-Basics--Example-design-flow
Part 3: http://edn.com/design/pc-board/4428665/Component-placement-tips-and-strategies

How to design the perfect PCB
Part 1: http://www.michaelhleonard.com/how-to-design-the-perfect-pcb-part1/
Part 2: http://www.michaelhleonard.com/how-to-design-the-perfect-pcb-part2/
Good overview of the design process, lots of pictures

Altium Designer Tutorial: Schematic capture and PCB layout
Part 1: http://www.youtube.com/watch?v=Y7PY1nBtImk
Part 2: http://www.youtube.com/watch?v=9u0Fzpb0yZU
Video examples.

The Engineer’s Guide To High-Quality PCB Design
http://electronicdesign.com/embedded/engineer-s-guide-high-quality-pcb-design

EEVBlog on PCB Design for Manufacture
"A how-to guide to taking your electronics project from prototype through to high volume PCB manufacture."
Part 1: http://www.eevblog.com/2010/11/15/eevblog-127-pcb-design-for-manufacture-tutorial/
Part 2: http://www.eevblog.com/2012/01/25/eevblog-239-pcb-design-for-manufacture-part-2/

Ten best practices of PCB design - EDN
http://edn.com/electronics-blogs/all-aboard-/4429390/Ten-best-practices-of-PCB-design

Class Specific Information

Now that I have reviewed some of your schematic and PCBs I can summarize the most common issues.

Schematic:

• Use a mix of net names and wires. It's really hard to read a schematic with only wires, or with only net names. Read this Sparkfun tutorial and check Charles' design for examples.
• Use explicit net names. 'LED1' is much better than 'PA0'.
• For VCC/+5V & GND use the symbols from the 'supply1' lib. Do not mix names (I've seen some schematic where the +5V symbol was linked to a net names 'VCC').
• When you place a resistor such as 'RES-US1206FAB' it doesn't have a value. It could be 0 ohm or a mega ohm. Use the 'Value' command.
• It's good practice to draw your schematic in a frame. In the 'frames' lib use 'A4LOC'
• Use the 'Show' tool to highlight your nets and make sure that what you think is connected truly is
• Be careful when you wire your switch. If you connect it across +5V and GND you will short your power supply when you press on it... your laptop might not like that.
• Keep in mind that at some point your schematic will be printed in black and white. Will people be able to understand what's going on? Using a frame (the same size as your sheet), clear names, un-tangled wires and comments will make it so much easier for someone reading it.

PCB:

• When possible, avoid right and acute angles
• When you are done routing make sure to run a DRC (Design Rule Check). Use 'fab.dru' (it's in the archive, right next to fab.lbr) as your design rule file. The DRC will tell you if your board can by milled or not.
• Adjust the Outline to be slightly bigger than the circuit
• DRC: You will be milling your boards with the 1/64 endmill. 1/64 = 15.625 mils. You should use a clearance of AT LEAST 16 mils. 17 or 18 is probably safer. Here's a 17 mils DRU file for you: fablab_17mils.dru.
• Some versions of the fab.dru file have 0.315mm for the clearance. That's 12.4 mils => not enough. It's good for a 10 mils endmill, not for the one you'll be using.
• As a general piece of advice, never trust anything that comes free from the Internet. Always double-check. Same for the libs.
• A general rule of thumb is to use the same spacing for traces and clearance (so 16 mils in that case). If you need you can do finer traces (I use down to 6 mils on the Modela), but try to keep them wide for now.

Feel free to contact me at jfduval (at) mit (dot) edu if you have any questions or comments!