3/08/2015
Embedded Systems Design ELEN90066
Lecture 3 Printed Circuit Boards David Jahshan
Announcements
Timetable Issues
Please contact David Benson david.benson@unimelb.edu.au for help.
Subject Issues
Please contact subject co-ordinator Iman Shames
Labs start this week
First lab: learning how to use Altium Designer
Today • Introduction to PCB
• ManufacturingTechniques • Design Flow
• Example
What is a Printed Circuit Board? • Copper plated Fibreglass (or other
nonconductive material)
• Holes drilled for components
• Copper removed to create wires
Legs
Component Fibreglass
Copper Solder
Why Use A PCB?
• Easier to assemble • Neater
• MoreRobust
When do you use a PCB? • After you are sure of your design
– Breadboard first
• When using surface mount components
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Different Types Of PCB’s
• SingleSided
– Has copper only on one side
• Double Sided
– Has copper on both sides
• MultipleLayer
– Has copper on both sides as well as layers of copper in the middle.
How do you connect different
layers?
• Vias are small holes to permit a connection
from one layer to the other • Vias are made by either
– Wires
– Through hole plating
Solder
Wire
Blind Via
Buried Via
Copper
Fibreglass
How are PCB’s Made?
• Create the PCB art work using CAD tools such as Altium Designer
• Manufacture the PCB using photolithography
Photolithography • Print out artwork onto transparency
• Drill holes into PCB blank
• Coat PCB blank with photoresist
• Place artwork onto PCB blank
• Expose to UV light
• Develop
• Etch
• Clean
UV Light
Glass Plate Artwork
Photoresist coated copper Fibreglass
Finishes
– Finished PCB’s rarely have bare metal, tends to corrode and makes it hard to solder
• Clear Circuit Board Lacquer • Solder Mask
• Silk Screen
• Tinned
• Solder Reflow
Assembly Methods • Hand Solder Components
• Slow and time consuming • Pick and Place machines
• Fast but only surface mount components • Wave Soldering
• Solder lots of through holes in one • Solder Reflow
• Part 2 of the pick and place machine
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Work Flow to Create a PCB
• Work out what the circuit needs to do • Select components
• Draw a schematic diagram
• Simulate the schematic
• Placecomponents
• Draw in where the wires need to go • ManufacturePCB
• Solder on components
Demo
• Don’t be afraid to make your own libraries (accept for this project)
• Remember to set up your rules first, they are critical for a good PCB
Remember to:
• Label your nets
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