PCB design and Introduction to KiCadELEC-D0301 Protopaja15.6.2020Juha Biström

Why to make a PCB

● Mounting for components

● Wires between components

● PCB CAD will ensure the circuit is connected properly

● Hugely improved reliability, especially compared to some sketchy ratsnest of wires or breadboard

● Clean and representable solution to a product

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KiCad

● Open source PCB CAD

– Main supporter Cern

● Efficient and versatile tool for design of circuits and PCBs

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Components of KiCad

● Eeschema – circuit design

● Symbol editor – create and edit own symbols

● Pcbnew – Layout design based on circuit

● Footprint editor – create own footprints

● Gerber viewer – view manufacturing files

● PCB calculator – relevant calculators to help PCB design

– e.g. minimum trace width for specified current

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KiCad workflow

● Create schematic/circuit– Create own symbols if needed

● Annotate symbols (components)

● Assign footprints to symbols– Create own footprints if needed

● Design layout based on previous steps– Previous steps can be visited if needed

● Generation of manufacturing files

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General hints for KiCad

● Memorize at least the most common key shortcuts– It will speed up your work a lot

● Grab (g) ↔ Move (m)

● Absolute and relative (to a movable origin) coordinates– Can be used e.g. to aligning to a grid or measuring distances

– Origin is placed by space bar

● Internet has a lot of instructions and other material– http://docs.kicad-pcb.org/5.1.2/en/getting_started_in_kicad/getting_started_in_kicad.html

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Tips to schematic design● Start by filling project information and adding mounting holes

● Use supply voltage nets (power nets)

● Create own nets where appropriate (label)– Multiple long wires make schematic unclear and disorganized

● Remember to add Power flags to power supply lines

● When schematic is done, proceed with toolbar special functions from left to right

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Eeschema user interface

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Eeschema user interface

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Symbol annotation

● It's convenient and easy to annotate all symbols automatically at once

● Different naming conventions depending on e.g. project size

– Symbol number for whole project

– Sheet number * 100 + symbol number

– Sheet number * 1000 + symbol number

● Can be used to annotate a sheet at a time or whole project at once

● Can not be undone

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Electrical rules check, ERC

● Checks circuit integrity based on pin definitions– e.g. two outputs shall not be connected together, supply voltage has to be present

● Problems might arise from errors in symbols– Especially in self made symbols

● Mystic power supply problems are usually due to missing power flags in external supply connection

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Footprint association

● In this phase casing type and size will be chosen to symbols

● Can be changed later if e.g. PCB space is running out or component can't be found in that casing

● Self made footprints have to be ready before associating them

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Tips to layout design● Start by filling project information and design rules

– E.g. minimum trace widths and spacings, trace widths to be used, via sizes

– Is the PCB going to be etched or produced commercially (→ check supplier minimum rules)

● Draw (preliminary) board edges (Edge.Cuts) and place mounting holes

● Spread components in groups e.g. by functional blocks

● Place critical parts and their traces then others– Connectors are convenient at board edges

– Indicators, connectors, check points and debug ports should be located on same side of board

– Switches, potentiometers, displays and other mounted to housing can be wired

– If etching board, try to avoid vias, as they are labour intensive to mount

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Pcbnew user interface

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Pcbnew user interface

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Questions?

● Time for demo

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