How to Design Printed Circuits Boards

How to Design Printed Circuits Boards

How to Design Printed Circuits Boards ... and live to tell about it. Bob Kressin, Instructor Department of Electrical Engineering and Computer Science Overview What is a Printed Circuit Board? How do you design a PCB? How do you order a custom PCB? 2 What is a PCB? A Mechanical Solution to an Electrical Problem

Photo from hephaestusaudio.com Photo from www.sparkfun.com 3 What is a PCB? Layers, Traces, Planes, and Vias ... oh my! Image from www.elkosoft.com 4 What is a PCB? Essentially, youre job is this ... Image from www.gettyimages.com 5

Component Suppliers Where do we get the goods? For the weird & wonderful www.sparkfun.com For the inexpensive everyday www.mouser.com For the board itself - www.4pcb.com The PCB Design Process From Vision To Reality Schematic Capture Place Components Eagle PCB

www.cadsoft.de Iteration Route Traces Generate Gerbers 7 Fab! Eagle PCB A CAD Tool For Designing a Board Control Panel Project Schematic Capture

Layout Symbol Footprint Library 8 Eagle PCB Symbol + Footprint + Device = Component Symbol Sym Device Dev

9 Footprint Pac Eagle PCB Stuff I Need To Get Started A Plan Block Diagram / Napkin Sketch Component Selection Connections and Testing Considerations Power and Performance Considerations A New Project Access to Libraries 10 Eagle PCB

Its all about the planning. Components Connections Power & Performance Passives: 0805, 0603, etc. Mechanical Connections Power Ratings IC Packages:

QFN, TQFP, etc. Bus Connections Battery Performance Libraries PC Connections High-Speed / HighSensitivity 11

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 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 doesnt mean you can access it in your schematic. 13 Schematic Capture Creating a New Schematic File -> New -> Schematic Save it right

away. Dont worry about creating a Board just yet. Keep the 100-mil grid. 14 Schematic Capture Schematic Capture Click the Add Adding Components

icon Find the component in the library Set values Dont see the library? Try Use > Library 15 Schematic Capture Schematic Capture Adding Global Symbols

Click the Add icon Find the global symbol in the library (supply1) Place as if it were a component 16 Schematic Capture Schematic Capture Adding Traces (aka Wires) Click the Wire

icon Have at it! 17 Schematic Capture Schematic Capture 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 - dont be lazy. Document! 18 Place Components Schematic Capture 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 Thru-Hole (TH) DIP Surface Mount (SMT) LQFP, QFP, TQFP 19 QFN BGA Place Components Creating a new board design

From the schematic, choose File -> Switch to Board. Create From Schematic? You bet! Board window automatically opens. 20 Schematic Capture Place Components Place Components

Some Common Tasks Right-click on top of component, select Move to reposition. While moving, rightclick to Rotate. Use Group wisely. Right-click to Mirror (change to other side of board) Use Move to change outline 21

Schematic Capture Place Components 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. 22

Schematic Capture Place Components Place Components Schematic Capture 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. 23 Schematic Capture Route Traces

Place Components 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. 24 Schematic Capture Route Traces Some General Tips Two layers? Have an Place Components Route Traces x-layer and a y-layer. Dont forget mounting holes, other nice things.

Add testability features. Do the what if? dance. Do the cardboard mockup. Pour Copper. 25 Generating Gerbers Some General Tips Schematic Capture

Place Components Route Traces Gen Gerbers Easier than spit! Using Advanced Circuits? Have I got a script for you ... This involves the CAM Processor ... Generate critical layers. 26 Generating Gerbers

Sanity Checking The Result Schematic Capture Place Components Route Traces Gen Gerbers freedfm.com Youll 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. 27 Generating Gerbers Reviewing The Result Schematic Capture Place Components Route Traces Gen Gerbers ViewMate - Free Gerber Viewer for Microsoft Windows (link on Dr. Wickerts site).

Review planes, drill holes, and obvious defects. Not usually any surprises here. Biggest error - not exporting the proper layers. 28 Schematic Capture Fab Place Components Route Traces Before you hit the button ... Gen Gerbers Fab!

Generate a Parts List (aka The BOM) using Export -> Partlist. Generate a Pin List (aka The Netlist) using Export -> Netlist. Sanity check both. 29 Schematic Capture Fab Place Components

Route Traces Some General Tips Gen Gerbers Fab! 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 The PCB Design Process A Summary of a Lot of Information Schematic Capture

Place Components Eagle PCB www.cadsoft.de Iteration Route Traces Generate Gerbers 31 Fab!

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