Transcript Printed Circuit Board Design - IEEE Concordia

Printed Circuit Board Design
IEEE Concordia Student Branch
Presented by Marc-Alexandre Chan
Concordia University, 26 November 2015
Photo by Christian Taube, CC-BY-SA 2.5.
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Workshop Overview
1. Why PCBs?
2. Background
3. Design Process
4. Advanced Considerations (Intro)
5. Software Walkthrough
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Why PCBs?
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Why PCBs?
Limited alternatives: Breadboard/protoboard,
wire wrap, chassis mount, point-to-point
Custom designed for each circuit
High flexibility
Compact (high density)
Protective solder mask
20+ layers possible
Robots!
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(or cheap overseas labour)
Photo by Christian Taube, CC-BY-SA 2.5.
Technical Background
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Board Technologies
Board Materials
Most common: FR4
Copper layers
– Epoxy and fibreglass
– Allows traces to cross
– Heat resistant, cheap
– More heat dissipation
– Usually 1.6mm thick
– More compact board
High-frequency boards
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Layer Structure
– Usually 1oz (thickness)
– Controlled impedance
Surface Layers
– Usable at 1 GHz or more
– Solder mask
– Well-known: Rogers Corp.
– Silkscreen printing
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Board Technologies
Components, solder mask, and silkscreen layers on a PCB. Photo by Christian Taube, CC-BY-SA 2.5.
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Packages: Through-Hole
Common types of through-hole capacitors
(aluminium × 4, ceramic × 4)
TO (transistor outline): TO-220 (left),
TO-92 (right), metal can, etc.
Axial lead resistor
Inline packages: SIP, DIP (above);
Plastic (PDIP, above), ceramic (CDIP)
Photo credits: Abdullah Al Mamun, CC-BY-SA 2.5 Generic / Wikimedia Commons;
“Nunikasi”, CC-BY-SA 3.0 Unported / Wikimedia Commons; Adafruit Industries, CC-BY-NC-SA, Flickr;
Yves-Laurent Allaert, CC-BY-SA 3.0 Unported / Wikimedia Commons;
Kimmo Palosaari, public domain / Wikimedia Commons;
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Diodes in DO-41 package
Packages: Surface Mount (1)
SMD capacitors
Resistors are similar
Sizes in photo:
– 1206, 1206, 0603, 0603
– 1210, 1206, 0805, 0805
– 1812, 1812, 1206, 1210
Photo credits:
“Shaddack”, public domain / Wikimedia Commons.
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Packages: Surface Mount (2)
SOT-23-3
(3-pin small-outline transistor 23)
SO-8 (“SOIC” family)
(with PDIP for comparison)
Left to right: SOIC-14,
SSOP16, QFN-28
BGA-16 (left, top and bottom
of package), with SOT23-6
Photo credits: All images on this slide from Wikimedia Commons.
“Leapfrog”, public domain; “Swift.Hg”, CC-BY-SA3.0 Unported; “SPHL”, CC-BY-SA 3.0 Unported;
“NobbiP”, CC-BY-SA 3.0 Unported; “NobbiP”, CC-BY-SA 3.0 Unported.
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QFP40 (40-pin quad flat pack)
0.65mm pitch
Design Software
Hobbyist
DipTrace (Win/Mac/Lin)
Cadence OrCAD/Allegro
KiCad (Win/Mac/Lin)
Altium Designer
CircuitMaker (Win)
Agilent ADS
gEDA (Linux)
Pulsonix
Eagle (Win)
Mfg’s software
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Design Process
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Component Selection
Classes vs. real world
– In class: “100nF cap”
– Real world: And…?
 Material. (Polarised?)
 Rated voltage
 Physical size/package
Photo by John Fader. CC-BY-SA 3.0.
 Maximum temperature
 Error tolerance + tempco
 Cost!
– Digi-Key: 10HV23B104KN
– 100nF, 1kV, 10%, $70 ea.
Photo by Megger Ltd. CC-BY 3.0.
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Component Placement
Balance of objectives
– Room for traces
– Compactness (cost)
– Heat dissipation
– Design simplicity
– Assembly
IC pin layouts
– Dictated by IC structure
– Can seem illogical
Photo by Nicholas Wang (modified). CC-BY-SA 2.0.
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Component Pinout Example
From the CD4543BE datasheet (Texas
Instruments). Educational use.
Yes, you are reading the diagram correctly. The
pinout uses order A-D-B-C and A-B-C-D-E-G-F.
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Routing Techniques: Traces
Like wires on a PCB
Point A to point B
45o junctions: not 90o
Can’t cross each other
Usually CNC milled
– Avoid right angles
– Avoid T junctions
Classic PCB “look”
Photo by Creativity103 (flickr). CC-BY 2.0.
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Routing Techniques: Vias
Connect layers
– All: Straight through
– Some: Buried/blind vias
 Difficult and expensive
Allows trace “tunnels”
– Pass under another trace
Tips for vias
– Through hole pads = vias!
– Allow for enough space
– High current: more vias
Photo by Karl-Ludwig G. Poggemann. CC-BY 2.0.
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Routing Techniques: Copper Pour
Large area of copper
– High thermal capacity
– Large current capacity
– Obstacle for traces
– Obvious light colour
Copper pour tips
– Might need thermals
– Can have vias in them
– Island/deadzone removal
– Software priority order
Photo by t0msk (flickr). CC-BY-NC-SA 2.0.
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Ground/Power Planes
Common in 4+ layer PCBs
– Copper pour for whole layer (power, ground)
– Objective: low inductance/resistance
– Objective 2: Signal shielding
For 2-layer PCBs
– Same objectives, can’t use layer!
– Use big pours for power/ground
– Avoid “thin” connections between power/ground pours
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Practical Considerations
Routing components
Fabrication constraints
– Take advantage of mask:
Put traces between pins!
– Trace resist./inductance
– Traces under SMD parts
– Plated holes as vias
 Minimum sizes
 Clearances
Physical constraints
– Real-world drill sizes
– Space for soldering?
Safety/protection
– Big components?
– ESD, overvoltage,
overcurrent, reverse
polarity, short circuit, &c.
– Indicator LEDs visible?
– Switches, cables,
connectors have space?
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– DRC limits
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External Connections
Board-to-Device
Pin Headers
Sockets
Dedicated Connectors
– JST/Servo
– Computer Cables
– Barrel Connectors
Chassis Mounting
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Board-to-Board
Slotting
– Routing / Fabrication
– Gold Fingers
– Tab Routing
Stacking
– Arduino Shields
Connector Examples
Photo credits (clockwise from top left): oomlout (flickr), CC-BY-SA 3.0; Appaloosa, CC-BY-SA
3.0 / Wikimedia Commons; M7, public domain / Wikimedia Commons; Mike1024, public domain
/ Wikimedia Commons
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High-Frequency Considerations
High-Frequency
Multilayer Design
Board RF Behavior
Problems Alleviated
– Transmission line effects
– Ground loops
– Digital circuit switching
– Intentional antennas
– Unintentional antennas
Controlled Impedance
– Simulation / fabrication
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 Traces to ground have
impedance in real world!
– Crosstalk
Internal Planes
– “Free” capacitor
– Buried/blind vias
Photo by Windell Oskay. CC-BY 2.0.
DipTrace: A Design Walkthrough
Link to PCB software: http://ieee.concordia.ca/portfolio/pcb-workshop/
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Concept: Schematic and Layout
Schematic
– Circuit components
– Connections (“ideal”)
– Priority: easy to read
Layout
– Physical PCB layout
– Component placement
– Traces, pours
– Nonideal effects
vs. position
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Concept: Components and Patterns
Component
– Schematic symbol only
– “Idea” of a component
– Component value, etc.
Pattern (or footprint)
– Copper pads on PCB
– Real part soldered on it
– Holes (if needed)
– Generic patterns (DIP…)
– “Attach” to component(s)
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Alarm/Buzzer Module
Schematic: Alarm/buzzer module
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Alarm/Buzzer Module
How it works
– When TRIG is LO (0V): nothing happens
– When TRIG is HI (5V) :
buzzer sounds
– When TRIG is short to ground: nothing happens
– When TRIG is open circuit: buzzer sounds (pull-up R)
Ideas for the module
– Plug a switch in between TRIG and GND
– Use reed switch+magnet on door!
– Microcontroller module, keypad…
– Arm/disarm, intruder detection, alarm patterns, etc.
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To Do List
Basic schematic capture
– Choose components
– Connect with wires
Custom components
– LM555CN
 Custom symbol (pins)
 Standard DIP8 pattern
– Speaker custom symbol and
pattern
Convert to PCB
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Routing the board
– Create board outline
– Ground and power planes
– Target size: 5cm × 8cm
– Traces for programming
– Pre-place components
– Check drill sizes
– Verify packages and sizes
– Prepare for manufacturing
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Board Layout
Sample PCB layout:
top layer (left) and bottom layer (right)
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Ready for Manufacturing
Sample PCB Gerber file (bottom layer traces)
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Ready for Manufacturing
How can you manufacture your design?
Do it yourself with traditional methods
– Photosensitive two-sided copper boards
– Regular copper board + a laser printer + glossy paper
– In all cases: ferric chloride to eat away unwanted copper
Get a fab house to do it
– Many companies can do prototypes/small orders for cheap
– APCircuit (Alberta, http://www.apcircuits.com)
– Advanced Circuits (US, http://www.4pcb.com)
– ITEAD (China, http://iteadstudio.com)
– SeeedStudio (China, http://www.seeedstudio.com)
– OSHPark (US, https://oshpark.com)
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Want to learn more?
More details and “good practices” for PCBs?
– http://alternatezone.com/electronics/files/
PCBDesignTutorialRevA.pdf
Want to start getting into advanced PCB design?
– High power and high current design
 Copper thickness (“weight”: standard is 1 oz)
 Maximum current through a trace
 Isolation slots, circuit isolation
– High frequency design (100MHz to many GHz)
 Transmission line effects, microstrip design…
(ELEC351/353/453)
 Cross-talk, resonant circuit layout, etc.
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Thank you for participating
in this workshop!
Questions? [email protected]
http://ieee.concordia.ca
This work is licensed under the Creative Commons BY-NC-SA 3.0 Unported License. To view a copy of this license,
visit http://creativecommons.org/licenses/by-nc-sa/3.0/ or send a letter to Creative Commons, 444 Castro Street,
Suite 900, Mountain View, California, 94041, USA.
Copyright © 2013-2015 the Institute of Electrical and Electronics Engineers, Inc. Contributors: Marc-Alexandre
Chan, Ryan Desgroseilliers.
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