PCB_Design_Process for BTech students.ppt
- 1. How to Design Printed Circuits Boards ... and live to tell about it. Bob Kressin, Instructor Department of Electrical Engineering and Computer Science
- 2. Overview •What is a Printed Circuit Board? •How do you design a PCB? •How do you order a custom PCB? 2
- 3. What is a PCB? A Mechanical Solution to an Electrical Problem Photo from www.sparkfun.com 3 Photo from hephaestusaudio.com
- 4. What is a PCB? Layers, Traces, Planes, and Vias ... oh my! Image from www.elkosoft.com 4
- 5. What is a PCB? Image from www.gettyimages.com Essentially, you’re job is this ... 5
- 6. Component Suppliers •For the “weird & wonderful” - •For the “inexpensive everyday” - •For the board itself - Where do we get the goods? www.sparkfun.com www.mouser.com www.4pcb.com
- 7. The PCB Design Process From Vision To Reality Eagle PCB www.cadsoft.de 7 Place Place Components Components Route Traces Route Traces Fab! Fab! Iteration Generate Gerbers Generate Gerbers Schematic Schematic Capture Capture
- 8. Eagle PCB A CAD Tool For Designing a Board Schematic Schematic Capture Capture Layout Layout Control Panel Control Panel Library Library Symbol Footprint Project 8
- 9. Eagle PCB Symbol + Footprint + Device = Component Device Device Dev Dev Symbol Symbol Sym Sym Footprint Footprint Pac Pac 9
- 10. Eagle PCB •A Plan •Block Diagram / Napkin Sketch •Component Selection •Connections and Testing Considerations •Power and Performance Considerations •A New Project •Access to Libraries Stuff I Need To Get Started 10
- 11. Eagle PCB It’s all about the planning. Components Components Connections Connections Power & Power & Performance Performance Passives: 0805, 0603, etc. IC Packages: QFN, TQFP, etc. Libraries Mechanical Connections Bus Connections PC Connections Power Ratings Battery Performance High-Speed / High-Sensitivity 11
- 12. Eagle PCB Creating a New Project •Launch Eagle •File -> New -> Project •Enter Project Name •Directory structure taken care of automagically. •Active project is shown with a green light. 12
- 13. Eagle PCB Accessing Libraries •Full view of libraries available via Control Panel •Download more from the web and place in the Eagle installation directory in /lbr •Sparkfun has an incredible library of more advanced parts (accelerometers, etc.) •Caution! Just because you see the library in Control Panel doesn’t mean you can access it in your schematic. 13
- 14. Schematic Capture Creating a New Schematic •File -> New -> Schematic •Save it right away. •Don’t worry about creating a Board just yet. •Keep the 100-mil grid. Schematic Capture Schematic Capture 14
- 15. Schematic Capture Adding Components •Click the Add icon •Find the component in the library •Set values •Don’t see the library? Try Use -> Library Schematic Capture Schematic Capture 15
- 16. Schematic Capture Adding Global Symbols •Click the Add icon •Find the global symbol in the library (supply1) •Place as if it were a component Schematic Capture Schematic Capture 16
- 17. Schematic Capture Adding Traces (aka Wires) •Click the Wire icon •Have at it! Schematic Capture Schematic Capture 17
- 18. Schematic Capture Some General Tips • Avoid changing the grid unless absolutely necessary. • Free Eagle version does not allow “sheets”. • Free Eagle version requires that schematic drives the layout ... not vice-versa. • Groups, Info, and Layers icons are useful. • Pan, zoom, niceties easy to use. • Really care about that “net”? Label it. • Keep it clean - don’t be lazy. • Document! Schematic Capture Schematic Capture 18
- 19. Place Components But before you do ... • Passives - 0805 means 0.08” by 0.05” • Connectors - beware of physical fit • Actives - lots of packaging alternatives • Give thought to testability and troubleshooting Schematic Capture Schematic Capture DIP LQFP, QFP, TQFP QFN BGA Thru-Hole (TH) Thru-Hole (TH) Surface Mount (SMT) Surface Mount (SMT) Place Components Place Components 19
- 20. Place Components Creating a new board design • From the schematic, choose File -> Switch to Board. • “Create From Schematic”? You bet! • Board window automatically opens. Schematic Capture Schematic Capture Place Components Place Components 20
- 21. Place Components Some Common Tasks • Right-click on top of component, select Move to reposition. • While moving, right- click to Rotate. • Use “Group” wisely. • Right-click to Mirror (change to other side of board) • Use Move to change outline Schematic Capture Schematic Capture Place Components Place Components 21
- 22. Place Components Thinking ahead • Take your time. • Untangle flight lines. • Think about planes. • Consider testability. • Mechanical Fit? • Hard stuff first. • Keep silkscreen. • Think hard about components on 2-sides. Schematic Capture Schematic Capture Place Components Place Components 22
- 23. Place Components Some General Tips • Are your Design Rules setup correctly? • Run the Design Rule Check (DRC) often. • Run the Electrical Rule Check (ERC) often. • Save a snapshot of your placement file. Schematic Capture Schematic Capture Place Components Place Components 23
- 24. Route Traces Adding “Waaaahrs” To Your Layout • You want to route, not wire. • You want to ripup, not delete nets. • Are you on the top or the bottom? • Vias are on top and bottom. Easy to add. • DRC often! • Iterate like mad. Schematic Capture Schematic Capture Place Components Place Components Route Traces Route Traces 24
- 25. Route Traces Some General Tips • Two layers? Have an x- layer and a y-layer. • Don’t forget mounting holes, other nice things. • Add testability features. • Do the “what if?” dance. • Do the cardboard mockup. • Pour Copper. Schematic Capture Schematic Capture Place Components Place Components Route Traces Route Traces 25
- 26. Generating Gerbers Some General Tips • Using Advanced Circuits? Have I got a script for you ... • This involves the “CAM Processor” ... • Generate critical layers. Schematic Capture Schematic Capture Place Components Place Components Route Traces Route Traces 26 Gen Gerbers Gen Gerbers Easier than spit!
- 27. Generating Gerbers Sanity Checking The Result • You’ll need an account with Advanced Circuits. • Email will be sent confirming design rule checking. • Advanced Circuits even gives you a discount. • Squash any errors, review all warnings. Look for open vias, closed vias, etc. Schematic Capture Schematic Capture Place Components Place Components Route Traces Route Traces 27 Gen Gerbers Gen Gerbers freedfm.com
- 28. Generating Gerbers Reviewing The Result • ViewMate - Free Gerber Viewer for Microsoft Windows (link on Dr. Wickert’s site). • Review planes, drill holes, and “obvious” defects. Not usually any surprises here. • Biggest error - not exporting the proper layers. Schematic Capture Schematic Capture Place Components Place Components Route Traces Route Traces 28 Gen Gerbers Gen Gerbers
- 29. Fab Before you hit “the button” ... Schematic Capture Schematic Capture Place Components Place Components Route Traces Route Traces 29 • Generate a Parts List (aka “The BOM”) using Export -> Partlist. • Generate a Pin List (aka “The Netlist”) using Export -> Netlist. • Sanity check both. Gen Gerbers Gen Gerbers Fab! Fab!
- 30. Fab Some General Tips • Do you have all of your components? Lead time? • Find out what file format your PCB Vendor wants. • Advanced Circuits - GERBER_RS_274X (no, really) • Consider routing it yourself at UCCS. • Consider barebonespcb.com. Really cheap. • Sleep on it. Follow my tradition - 30 Schematic Capture Schematic Capture Place Components Place Components Route Traces Route Traces Gen Gerbers Gen Gerbers Fab! Fab!
- 31. The PCB Design Process A Summary of a Lot of Information 31 Place Place Components Components Route Traces Route Traces Fab! Fab! Iteration Eagle PCB www.cadsoft.de Generate Gerbers Generate Gerbers Schematic Schematic Capture Capture